US3336835A - Color source - Google Patents

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US3336835A
US3336835A US453308A US45330865A US3336835A US 3336835 A US3336835 A US 3336835A US 453308 A US453308 A US 453308A US 45330865 A US45330865 A US 45330865A US 3336835 A US3336835 A US 3336835A
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Prior art keywords
light
color
lens
filter
filter means
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US453308A
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Lester R Evensen
David A Lieberman
Jr Anthony W Vering
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Welch Scientific Co
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Welch Scientific Co
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Priority to US453308A priority Critical patent/US3336835A/en
Priority to GB19189/66A priority patent/GB1142524A/en
Priority to DE19661522310 priority patent/DE1522310A1/en
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    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03BAPPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B27/00Photographic printing apparatus
    • G03B27/32Projection printing apparatus, e.g. enlarger, copying camera
    • G03B27/52Details
    • G03B27/54Lamp housings; Illuminating means
    • G03B27/545Lamp housings; Illuminating means for enlargers
    • G03B27/547Lamp housings; Illuminating means for enlargers colour mixing heads

Definitions

  • This invention relates to a color source in general, and more specifically is directed to a new and improved color head which is adapted for use with existing enlarger system, for example, that type system commonly known as a condenser-type enlarger.
  • the present invention is also suitable for use in color analysis, reproduction determination and the like. For convenience, however, it will be described in conjunction with a photographic enlarger and printer system as deficiencies in existing designs were the principal stimulant in its development.
  • One of the more widely used methods of printing techniques involves multi-layer dye coupling type paper readily available on the open market.
  • the individual layers are sensitive respectively to red, green and ⁇ blue light to release the dye.
  • Cyan, magenta and yellow layers form the negative film to be printed, which layers are responsive respectively to adjust the level of the red, green and blue light reaching the paper.
  • Such negatives are obtained through the exposure and development of such film known by the trademarks Kodacolon Ektacolor and the like.
  • the sensitive layers of the paper are not only responsive to the specific wave lengths of red, green and blue contained in the white light but will also respond to wave lengths above, below and between the red, blue and green Wave lengths. Accordingly, unwanted portions of the white light sensitize the various layers resulting in a print which is somewhat removed in color proportions from the negative.
  • Elimination of .subtractive filters in the enlarger increased the efiiciency of the light.
  • exciting light is refined to the peak response of the individual layers of the photographic paper to avoid simultaneously stimulating adjacent layers.
  • a small but further correction provides rened light whose peaks fall within the range of peak response of the individual layers of the photographic paper and are still within a more sensitive wave length -range of known types of phototubes.
  • the system required a minimum number of special parts while making highly eflicient use of the available light.
  • the present invention provides a new and improved color head which solves the above noted problems and achieves all the stated objectives.- It is capable of providing an additive light source permitting simultaneous balanced exposure of the sensitive layers of photographic paper since this light source, through a unique lens and multi film lter system, provides a coaxial white light composed-of color components which are of a well defined band width and which for all practical purposes are nonoverlapping.
  • the present invention through a unique and unobvious solution of the problems enumerated, provides a system whereby the problems of the prior art may be avoided.
  • FIG. 1 is a perspective view of the color head of the present invention applied to a conventional type condenser enlarger;
  • FIG. 2 is an elevational view of the color head shown in FIG. l with the shield removed;
  • FIG. 3 is a top plan view of the color head as shown in FIG. 2;
  • FIG. 4 is a side elevational view of one of the light source subassemblies
  • FIG. 5 is a schematic diagram of the system shown in FIG. l.
  • FIG. 6 is a graph of light transmittance (in percent) plotted against wave lengths for the visible region with the solid lines representing theoretical calculations taking into account the limitations of measuring phototube while compensating for the three layer peak response and the dash lines representing one workable set of wave lengths taken from the system of FIGS. 1 5.
  • an enlarger system is represented generally by the reference character 10 including a color head ll having a condenser adaptor i2 at the lower extremity.
  • a condenser system 13 and negative holder 15 of conventional design are disposed above an adjustable length bellows 14 which terminates in a focusing system 16 positioned above an easel schematically represented by the rectangle 1'7.
  • the color head 1l through use of the condenser adaptor l2 and unique optical design may be used with any known type of system which heretofore has used a single light source-
  • the optical design and geometry of the present invention is such that it terminates and presents the appearance to the condenser assembly of being a single white light point source evenly diffused into a perfect circle while in actuality being composed of three distinct colors of readily identifiable and well defined wave lengths.
  • the color head 11 is illustrated with the case or shield removed, generally displaying three separate light sources 2l), 2 1 and 22 arranged in vertical relationship above the condenser adaptor 12.
  • Each of the light sources has a'n optical land geometric axis which intersects a common vertically disposed central axis 30 coincidental with the geometric axis of the cylindrical condenser adaptor 12..
  • horizontal planes passing through the axis or center of each of the light sources 20, 21 and 22 are vertically spaced and parallel to each other and intersect a vertically disposed central axis 30 at righ-t angles.
  • the condenser adaptor 12 is broken away in FIG. 2 to illustrate a semisphere subassembly 23 which is also broken away to illustrate the mounting arrangement.
  • the semisphere subassembly includes a mounting tube 24 held in a bracket 25 which is disposed below the light source 2li.
  • the mounting tube 24 houses an aspheric lens 26 at its upper end and a plano-concave or negative lens 27 at its lower end.
  • a diffusing semisphere 28 is suspended from the lower end of the mounting tube 24.
  • Suitable retaining means may be provided to hold the lens in the position shown with the dimension between the two lenses 26 and 27 being carefully and accurately controlled.
  • the appearance of an ordinary single light source is presented making it suitable to replace a single light source.
  • the sources 2l), 2l and 22 are arranged about a central axis 30, angularly spaced in azimuth by 45. As seen in FIGS. 2 and 3, the central axis 30 is coincidental with the geometric axis of the mounting tube 24 and condenser adaptor 12. The importance of the coaxial arrangement of each of the light sources 2t), 2l and 22 will become apparent.
  • the angular spacing of the light sources 20-21 serves to allow the separation between each of the individual lamps contained in the light source with- 1n good design geometry in order to facilitate a good cooling or heat dissipation during operation of the enlarger.
  • a blower (not shown), is
  • a light source holder or mount 31 may be formed in any suitable manner by machining, casting or the like.
  • the holder 31 is provided with an upstanding bracket portion 32 which threadably mounts a plurality of thumb screws 33 for movement along their respective axes in response to rotation.
  • the thumb screws 33 at their inner end mount a spherical mirror 34 which may be adjusted towards and away from a lamp 35 mounted in a lamp socket 36 on the light source holder 31.
  • the lamp 35 is of a type known as having a prefocused base so that when inserted in the socket 36, the lament 37 will be in the same location relative to the base for all lamps within a specified close tolerance.
  • the light source holder 13 is provided with an annular chamber 38 terminating adjacent the lamp 35 in an inwardly projecting flange 4f), counterbored as at 41 to receive a positive meniscus lens 42.
  • An enlarged bore 43 adjacent the lens 42 has an enlarged counterbored portion to form a mount for a double convex lens 44.
  • the lens 42 is held within the counterbored portion on the fiange 40 by a retaining ring 45 while a larger diameter retaining ring 46 holds the double convex lens 44 in its mounting in the counterbored portion of the enlarged bore 43.
  • Each of the counterbored portions is very carefully machined in order that the lenses 42 and 44 may be accurately placed relative to each other and the lamp 35.
  • the positive meniscus lens 42 serves to initiate collimation of the light from the lamp 35 and for convenience will be identified as a first collimator.
  • the double convex lens 44 serves to collect and arrange light rays from the first collimator 42 into parallel rays and will be identified as the second collimator.
  • the light sources are point sources and light is uniformly passed by each lens.
  • the filaments have a finite dimension, and chromatic aberration is normally experienced.
  • the size of the filament can be ignored as well as aberration.
  • the filament size will run on the order of about several millimeters square. Accordingly, the collimating system shown was developed to accommodate this finite size of the filament and avoid aberration or non-uniformity in the intensity of the beam of light when viewed in cross section.
  • a filter mounting means or holder 47 which is held in place by suitable mounting means such as the screws 43 received in tappings in the holder 31.
  • Two permanent filters are shown at 5ft and 51 clamped within the filter mounting means 47 and serve to refine the collimated white light from the lamp 35 into a selected color having a wave length falling within selected limits for one of the additive primary color components.
  • An additional filter 52 which is sometimes referred to as a dichroic filter, is held to machine surfaces 53 and 54 on the light holder 31 by means of screws and clamps 55 and 56 respectively.
  • the dichroic filter 52 is arranged at a perfect 45 angle relative to the collimated light so that the incident and refiection angles are equal to 457 thereby to direct collimated and filtered light through the aperture 57 in the holder 31.
  • the aperture 57 has its cen- 6 ter coaxial with the central axis 30, as do the apertures on the light sources 20 and 22.
  • the light source 2t? is physically identical to the light source 21, and difiers optically only in the selection of filters to be substituted for equivalent filters 5f), 51 and 52.
  • light source 22 is physically identical to light source 21 with the exception that a single filter is substituted for the two filters 5t) and 51, and a dichroic having a different reflectance wave length is substituted for the dichroic 52.
  • the spherical mirror 54 may be adjusted at the factory to focus the maximum amount of light from the filament 37 of the lamp 35 back to the filament so it is directed toward the first collimator 42.
  • the lamp 35 when no longer operative, may be readily replaced by a similar lamp without affecting the optical relationship of the filament 37 relative to the collimating lens system.
  • the collimating lens system composed of the first collimator 42 and double convex lens 54 forming the second collimator, collimates the light into parallel bundles, directing it to the lters which by selection reject all light above and below selected wave lengths.
  • the intensity of the lamp 35 may be adjusted by the variable resistance shown schematically at 60.
  • this resistor comprises a -ohm 22S-watt resistance to provide a good range of intensity adjustment. Additional resistors may be placed in series and factory adjusted to obtain a reduced operating voltage to the lamp 35 for long life.
  • a preheat circuit may be provided t0 keep the filaments warm and further extend their life. With the arrangement shown, the power to the lamp 35 may be varied to raise and lower the intensity level for purposes noted above.
  • FIG. 5 the enlarger system 10 is illustrated in schematic form and like reference numerals have been given to common elements including the first and second collimators 42 and 44, lamps 35 and mirror 34 of each of the respective light sources 20, 21 and 22.
  • vertical filters 62 and 63 are provided to filter the collimated white light into a band falling between about 610 millimicrons and into the infrared region or about 740 millimicrons. The upper limit will be defined by a subsequent lter.
  • a 45 dichroic filter 64 is arranged in parallelism with the dichroic 52 and disposed in the path of the collimated light so that the angles of incidence and refiection will be equal to 45.
  • the upper light source 22 is provided with a single vertically disposed filter 65 which is sometimes referred to as a 90 filter.
  • the angularly arranged filter or dichroic 66 is located relative to its collimated light source such that the angles of incidence and reflection of the collimated light will be exactly equal to 45 which is parallel to the dichroics 52 and 64. All of the dichroics 52, 64 and 66 are arranged so that the angle of reflection of each will be coincidental with the central axis 30 to provide a refined coaxial white light.
  • the or transmitting filters 50, 51, 62, 63 and 65 allow only light of a specified or definite wave length to pass and are chosen and identified by their transmittance value.
  • the dichroics or separating filters 52, 64 and 66 are chosen to refiect only the desired color of light while transmitting or passing all that is not reflected.
  • the multi film filters selected absorb practically no light. Their transmittance at any selected wave length in the spectrum is determined by their refiecance at that wave length and accordingly when either of these factors is adjusted, the other increases or decreases in a compementary manner.
  • the filter 65 is designed to reflect all visible light above about 480 millimicrons. It transmits a preponderance (90%) of visible light wave lengths falling between about 380 and 425 millimicrons.
  • the associated dichroic or separating filter 66 passes almost all visible light above about 610 millimicrons while wave lengths below this value are reected along the axis 30. The lower range of the spectrum is reflected including ultraviolet rays which may be present, however, these are filtered out as will be seen.
  • a preponderance of refiectance (over 90%) is experienced in the band from about 400 to 560 millimicrons.
  • Filters 50 and 51 are chosen to transmit vlight having a wave length falling generally between 520 and 600 millimicrons being what is commonly known as the wave length band ⁇ for green light.
  • the associated dichroic or 45 separating filter 52 is designed to pass all light above and below the noted wave length and to reflect a band width of about 500 to 590 millimicrons at a 90% reflectance capability. Accordingly, the green color component is well defined and readily identified.
  • Multi film lters 62 and 63 in the lower light source 20 are chosen to pass all light above about 600 millimicrons including some wave lengths extending into the infrared range.
  • the associated dichroic filter 64 has a reflectance characteristic to reflect virtually all wave lengths above 630 millimicrons at 90% reflectance while transmitting other wave lengths. Accordingly, the separating or dichroic filter 64 serves to trim the lower end of the band by some 30'millimicrons to further separate it from the adjacent green component.
  • a 90 filter 67 is provided to suppress ultraviolet wave lengths or those wave lengths below about 400 millimicrons passing all visible wave lengths above.
  • a second filter 68 acts as a heat absorber to transmit with about 50% or ⁇ greater efiiciency, those wave lengths falling substantially within the visible region between an upper limit of 700 and the lower ultraviolet cut off of 400 millimicrons effected by filter 67. Accordingly, higher value wave lengths of infrared will be substantially suppressed with a small controlled portion passed. Unwanted ultraviolet light which is normally considered to be below 400 millimicrons is sharply cut off.
  • the light sources 20, 21 and 22 which are red, green and blue respectively, are energized, refined white light consisting of three identifiable and individually controllable well defined color components will be generated. At printing intensities, each of the colors is non-overlapping with adjacent colors.
  • Light source 22 will provide to the aspheric lens 26 light falling within 400 to 480 millimicrons with a peak transmittance falling slightly below what in theory is identied as pure blue.
  • the light source 21 will provide the green component of light which will be blended with the light from the blue source 22. This light has a wave length of about 520 to 590 millimicrons with a peak or maxi mum transmittance experienced at about 550 millimicrons as seen in dotted lines in the graph of FIG. 6.
  • the lower light source 20 will provide the red component of light, since it has a wave length of from about 600 millimicrons out into the infrared range slightly in excess of 700 millimicrons.
  • each of the separating filters 52 and 64 has a trimming effect on the color component reflected from the sources disposed above the same.
  • the accurate collimation provided by the unique collimating lens selection and arrangement directs the light to the filters at the proper incident angle. This is very critical as it avoids resonance conditions which arise when the light strikes the filter at non-unform incident angles, a common occurence when the light is not collimated.
  • the light rays of the three color components are blended together with the unwanted portion of ultraviolet filtered out through the filter 67.
  • the infrared wave lengths are controlled by the suppressor 68 to permit a small percentage to pass to enhance printing.
  • the aspheric lens 26 is of a special design to focus the blended color components to a focal point which is coincident with that of the negative lens 27, the latter serving to evenly diffuse or spread the light to ll the semisphere 28.
  • the plane surface of the planoconcave lens 27 may be etched, sand blasted, or the like to provide a diffusing surface to fill the semisphere 28 with light.
  • a separate diffuser may be provided as an alternative, however, ideally the diffuser should be as close to the plane surface as possible.
  • the semisphere 28 is a sphere truncated substantially above the geometric center and may also be provided with a diffusing type etch, sand blast, coating or the like on either the interior or exterior surface or both.
  • a color compensating lens 74 mayalso be provided immediately above the aspheric lens in those situations wherein enlargements of unusual size are to be made.
  • This lens is indicated in the diagram at 74 and includes a planoconcave lens receiving a double convex lens. As indicated, one side of the double convex lens is formed on a greater radius than the side abutting the plano-concave lens.
  • chromatic aberration exists in lenses resulting from the differences of the index of refraction at different wave lengths.
  • the compensating lens 74 formed of glasses having different refractive indices, the focal point of the upper and lower wave lengths are brought into coincidence and the intermediate wave length (green) also coincides fairly accurately. In this manner fall-off or loss of light at the corners of the photograph can be maintained uniform for all sizes. As pointed out previously, the light level around the margin of the photograph is substantially equal to that in the center. In printing pictures in the popular sizes, the color compensating lens is not needed and may be omitted..
  • the solid line represents a theoretical curve of the three additive colors as measured by a spectral photometer, which are arbitrarily assigned a value of percent.
  • the dash lines represent one workable solution to separating the wave lengths by the lens, filter and diffusing system described above.
  • the losses in intensity result from several factors common to optical systems. These include intersurface reiiections, scattering, absorption of light and the performance of the refiecting filters being somewhat less than one hundred per cent or perfect. This loss however is not critical so long as the actual curves are maintained within the given wave lengths, as the level of intensity for each lamp can be individually adjusted.
  • the light measuring probe When changing from the first negative to subsequent negatives the light measuring probe may be placed on the easel and the resistance adjusted to return the meter on the amplifier to Zero for each of the respective colors. Adjustment of one color does not affect the others. In this manner an appropriate color balance for each negative may be rapidly and readily obtained with a single test.
  • a second diffuser is inserted above the negative as at '73 in the space provided.
  • This diffuser is a clear plastic having embossments which diffuse a small portion of the collimated light to illuminate the side walls of negative scratches.
  • it When used in combination with the system above described and placed immediately above the negative in a conventional type of condenser enlarger, it provides a soft portrait type diffusion to the print, obliterating minor skin blemishes and the like without interfering with the trueness of the fiesh tones, eye color, hair color and other features.
  • a color head adapted for use in condenser type enlargers, said color head comprising three light sources disposed at different elevations, multi film filter means to separate light emitted from each of said light sources into light rays having wave lengths falling within a band identifying separate color components, said multi film filter means including means to blend said separated color components into a coaxial white light ray of transversely uniform intensity, and lens means adapted to receive said coaxial white light and focus the same at a focal po-int coincidental with the focal point of a negative lens means for uniform transmission to a condenser system of an enlarger.
  • diffusing means is disposed between said negative lens means and said condenser system of said enlarger, said diffusing means including a semispherical type diffuser.
  • a color head adapted for use in condenser type enlargers, said color head comprising three light sources disposed at different elevations, multi film filter means to separate light emitted from each of said light sources into light rays having wave lengths falling within a band identifying separate color components, said multi film filter means including means to blend said separated color components into a coaxial refined white light ray of transversely uniform intensity, lens means adapted to receive said ycoaxial refined white light and focus the same at a focal point coincidental with the focal point of a negative lens means, first diffusing means adjacent said negative lens means to diffuse said coaxial refined white light, and second diffusing means adapted to diffuse said coaxial refined white light for uniform transmission to a condenser system.
  • a color head adapted to provide refined coaxial light for use in photographic enlargers, said color head comprising a plurality of light sources, means to collimate light from each of said sources into a beam of transversely uniform intensity, a first filter means disposed in the path of each of said collimated light rays to separate light from each of said light sources into one component of three primary colors of red, blue and green, second filter means disposed at an angle to each of said first filter means to reflect and trim light from said each of said first filter means into a more sharply defined component of the primary colors while-simultaneously mixing said components into a beam of coaxial light rays of uniform intensity, and means to diffuse said light rays for uniform transmission to a condenser system.
  • a color head particularly adapted for use in condenser type enlargers comprising three separate light ⁇ sources disposed at different elevations, collimating Imeans adjacent each of said light sources, multi film filter means to separate collimated light from each of said light sources into a single refined light ray, each of said light rays having a -wave length defining one of three color components consisting of blue, green and red, said multi film filter means including means to blend said refined color components into a coaxial and further refined ⁇ white light ray of transversely uniform intensity, second lter means in the path of said coaxial white light to reject wave lengths above and below visible wave lengths, lens means to focus Vsaid coaxial refined white light at a focal point -coincidental with the focal point of a negative lens means, first diffusing means adjacent sai-d negative lens means to diffuse said white light, and second diffusing means adapted to spread said light for uniform transmission to a condenser system.
  • a color control head adapted for application to a condenser-type of enlarger, said color control head comprising three light source means arranged in vertically spaced planes, individual intensity control means for each of said light source means, first and second lenses posltioned closely adjacent said each of said light source means to collimate light into parallel rays, the first of said lenses being a positive meniscus lens and the second of said lenses being a double convex lens having the focal point thereof coincidental with the focal plane of said first lens, first multi filter means disposed perpendicular to the path of each of said collimated'rays to filter said light into collimated rays having a relatively narrow and identifiable band width, each of said light rays from each of said light source after passing said first lter means having a wave length which differs from the other light source means to provide light of the primary color components, second multi filter means disposed at an angle to each of said collimated and filtered light rays from each of said light sources, each of said second multi filter means being
  • a color control head adapted for appli-cation to a condenser type of enlarger in lieu of an existing light head, said color control head comprising three light source means arranged one above the other, each of said light source means having first and second lenses disposed adjacent said light source means to collimate light emitted from said light source means into perfectly parallel rays and direct the same to an axis disposed at an angle to said rays, multi filter means disposed in the path of said collimated light to reject all light falling outside a given :band width, whereby three collimated light rays of diverse band widths will be disposed in substantially par-allelism in different elevations, second multi filter means disposed at an angle to each of said collimated and filtered light rays, each of said second multi filter means being angularly disposed relative to said axis and to the collimated and filtered light ray whereby a portion will be reflected off of said second multi filter means, said portion of said light ray reflected off of each ⁇ of said
  • a color source adapted to provide refined light composed of three primary additive colors to an enlarger, said color source including first, second and third light sources arranged in parallel planes, each of said light sources including a lamp adapted to emit light of variable intensity, a collimating system adapted to collimate said light emitted from said lamp into anbeam of parallel light rays, first filter means disposed '1n the path of said light rays to reject a portion of said collimated light of an unwanted wave length, second filter means disposed atan angle to said collimated light passed by said first filter means, said second filter means passing all light of an unwanted wave length while reflecting light of desired wave length, said second filter means of said first, second and third light sources being arranged in coaxial parallelism, said second filter means of said second light source being further characterized by passing a preponderance of light refiected from said second filter means of said first light source, said second filter means of said third llight source being further characterized by passing a preponderance of light reflected from the second
  • each of said sources comprises a positive meniscus lens and a double convex lens, said positive meniscus lens being disposed adjacent said lamp, said lenses being adapted to arrange light rays emitted from said lamp into a parallel beam at right angles to said first filter means.
  • a color source adapted to provide refined light composed of additive color components of red, blue, and green, said color source including three light sources disposed at different elevations, each of said light sources including a lamp having a filament with a finite dimension, collimating means to collect unrefined light emitted from said filament and arrange it in parallel rays of transverse uniformity, a first filter means associated with each of said light sources and adapted to reject a portion of said unrefined light while transmitting the remaining portion of said light, a second filter means associated with each of said light sources, said second filter means being disposed in the path of collimated light transmitted by said first filter means, said second filter means associated with each source being arranged in coaxial relation whereby light rejected by each of said second filter means will ⁇ be arranged in blended coaxial relation with light rejected 'by each of the remaining filter means, third filter means disposed in the path of said blended coaxial light to further refine the same, and lens means to collect said light and diffuse the same into a semispherical diffusing means for transmission to
  • a color source adapted to provide light having ⁇ [blended components each of which is rened to a nonoverlapping wave length, said color source comprising three light sources disposed at different elevations, each of said light sou-rees emitting unrefined light from a filament of finite dimension, a collimating system to collect said light and arrange it in a parallel beam of substantially transverse uniformity, a first multi filter means adjacent each of said collimatingsystems, said rst multifilm filter means refining .light from each of said sources into additive primary colors of refined light having wave lengths corresponding to that of red, blue and green, a lsecond multi film filter means associated with each of said light sources and refiecting the primary colors of light, said second multi film filter means of said red source passing blue and green light from two of said sources, said second multi film filter means of said green source passing blue light from one of said sources, third filter means adapted to reect ultraviolet wave lengths while suppressing infrared wave lengths thereby providing a collim
  • a color head adapted for use in condenser type i enlargers, said color head comprising three light sour-ces disposed at different elevations, multilm filter means to separate light emitted from each of said light sources into light rays having Wave lengths falling Within a hand identifying separate color components, said multi lm filter means including means to blend said separated color components into a coaxial white light ray of transversely uniform intensity, said multi filter means selecting wave lengths in each of sa-id bands of said separate colors which lfall Ibetween the known peak response of the paper to be .printed and that of known types of phototubes, and lens means adapted to receive said coaxial white light and focus the same at a focal point coincidental with ⁇ the focal point of a negative lens means for uniform transmission to a condenser system of an enlarger.

Description

u@ 22, 1967 L.. R. EVENSEN ETAL. 3,336,835
COLOR SOURCE 2 Sheets-Sheet l Filed May 5, 1965 @rd/x0@ Wife/"Ugg u 22 B967 l.. R. EVENSEN ETAL 3,336,835
COLOR SOURCE 2 Sheets-Sheet 2 Filed May 5, 1965 United States Patent O 3,336,335 COLOR SOURCE Lester R. Evensen, Morton Grove, David A. Lieberman, Glenview, and Anthony W. Vering, Jr., Chicago, lill., assignors to The Welch Scientific Company, Skokie, lill., a corporation of Illinois Fiied May 5, 1965, Ser. No. 453,308 16 Claims. (Cl. 88-24) This invention relates to a color source in general, and more specifically is directed to a new and improved color head which is adapted for use with existing enlarger system, for example, that type system commonly known as a condenser-type enlarger. The present invention is also suitable for use in color analysis, reproduction determination and the like. For convenience, however, it will be described in conjunction with a photographic enlarger and printer system as deficiencies in existing designs were the principal stimulant in its development.
The prior art is replete with a variety of printing techniques, processes, materials and different approaches all aimed at obtaining a successful and expedient method of printing color photographs. Even the most successful of these `attempts involves a certain amount of cut and try techniques or repeated adjustment and measurement in order to obtain the necessary color balance. This is primarily due to deficiencies or inadequacies of the printing apparatus.
One of the more widely used methods of printing techniques involves multi-layer dye coupling type paper readily available on the open market. The individual layers are sensitive respectively to red, green and `blue light to release the dye. Cyan, magenta and yellow layers form the negative film to be printed, which layers are responsive respectively to adjust the level of the red, green and blue light reaching the paper. Such negatives are obtained through the exposure and development of such film known by the trademarks Kodacolon Ektacolor and the like.
When a negative of the type described is exposed through the use of a conventional white light source, i.e., a conventional light bulb, the sensitive layers of the paper are not only responsive to the specific wave lengths of red, green and blue contained in the white light but will also respond to wave lengths above, below and between the red, blue and green Wave lengths. Accordingly, unwanted portions of the white light sensitize the various layers resulting in a print which is somewhat removed in color proportions from the negative.
When light from a single source is used, a true balance between the three colors is almost impossible to achieve because the exposure of each of the respective layers in the paper is dependent upon time and intensity of exposure to the appropriate sensitizing color. As expected, each of the dyes in the paper have different response rates while the interval of exposure is obviously the same for all colors when a single exposure source is used, Various attempts have been made to subtract, by the use of filters, the unwanted light and wave lengths to bring the color balance to a reasonable approximation necessary to obtain a print of at least marginal quality. This procedure is sometimes identified as the subtractive process of color balancing and is vulnerable to a number of criticisms by those working in the field, since it generally requires more exposure time by slowing down the response time of the respective dyes in order to Ibring the same to a closer common time interval of exposure for each color. The large light losses caused by this as well as the testing and checking prior to printing consume a great deal of the printers time as Well as tying up the enlarger for a considerable period. Even in those cases when a reasonably good color balance is ultimately achieved, it is unstable being susceptible to drift because of the change in value of the lters due to heat, aging, exposure to high intensity light and the like. In summary, while the above technique is not a complete failure, it is far from what could be considered commercially desirable.
Notwithstanding the criticism of the subtractive filtration arrangement, it is in use by photographers since it is the most expedient and convenient of known and operable printing and enlarging systems to date. One specific cornmercial structure in use today utilizes a subtractive filter system in combination with an integrating sphere `and two light sources. The subtractive filters in this design are subjected to the criticisms noted above while the integrating sphere provokes additional criticism since it does not provide the desired fineness of control and leaves something to `be desired when the efficiency of the light is analyzed.
In the past when a truly balanced print has been desired, successive exposure of each of the layers has been recommended. In this process, filtered red, green and blue light is transmitted consecutively through the film negative, permitting a higher color purity to be achieved. As a general rule, in this process the color purity has been controlled by the use of lters disposed between the negative and the print paper, with the obvious adverse effect on image definition. Other disadvantages mainly in the time required, exist which makes the successive exposure techniques impossible for competitive type color printing work.
In general, in all systems, subtractive filters have also been undesirable since one filter will properly compensate to remove an unwanted band of color but at the same time will have an adverse effect on the level of color of an adjacent band. In checking the color balance in the subtractive process, it is necessary to insert filters in the path of the light and check each of the respective colors at various positions on the easel to determine and adjust for lthe exposure time and color balance. A probe, provided with filters, is used to check the intensity of each of the color components. Adjustments may be made by adding or suhtracting filters to effect a color balance. Since filters are needed at the probe, the efiective light intensity is lowered necessitating a more powerful amplifier, as well as a preamplifier in the probe which adds to its bulk. In addition, a need exists to physically touch the probe to shift from one filter to another. If the probe is moved slightly, as lby an accidental bump, it becomes necessary to repeat the color measurement with the former time and effort wasted.
The foregoing problems are but a few examples of the difficulties experienced in the past, which gave impetus to the development of the present invention. During this development, these objectives were attained. The interaction of filters was eliminated in order that the respective color levels could-be chosen with a single light probe test. The system was accurate whereby the usual correction factors provided on the box of the printing paper could be readily compensated for, thus making this information more useful. Various switching between and use of subtractive filters in the probe and enlargers was eliminated in order to minimize the number of adjustments, and therefore minimize the possibility of printers error.f The elimination of the filters in the probe also permitted the use of a simpler probe and lower gain amplifier with the obvious advantageous effect on sensitivity. Elimination of .subtractive filters in the enlarger increased the efiiciency of the light. In addition, exciting light is refined to the peak response of the individual layers of the photographic paper to avoid simultaneously stimulating adjacent layers. A small but further correction provides rened light whose peaks fall within the range of peak response of the individual layers of the photographic paper and are still within a more sensitive wave length -range of known types of phototubes. The system required a minimum number of special parts while making highly eflicient use of the available light.
Y The present invention provides a new and improved color head which solves the above noted problems and achieves all the stated objectives.- It is capable of providing an additive light source permitting simultaneous balanced exposure of the sensitive layers of photographic paper since this light source, through a unique lens and multi film lter system, provides a coaxial white light composed-of color components which are of a well defined band width and which for all practical purposes are nonoverlapping.
Simple adjustment and balance of each of the respective colors may be individually affected without any effect on the intensity of the other colors thus requiring minimum light level testing before printing may begin. The effect of this on the printing time is obvious. The present system is highly accurate and provides means whereby the `correction factors given with each supply of printing paper may be used to their fullest potential. With the present system the simplest type of probe and a relatively sensitive low gain amplifier may be used to balance the respective color components to an appropriate level of intensity.
The present invention, through a unique and unobvious solution of the problems enumerated, provides a system whereby the problems of the prior art may be avoided. A
number of advantages in addition to those enumerated ow from the novel solution about to be described. A better comprehension of these advantages as well as the salient features of the invention may be had by a consideration of the objects to be achieved and a detailed description of a preferred form of the invention which follows.
It is a principal object of this invention to provide a new and improved color source for photographic printers and the like.
It is another object of this invention to provide a color head which permits simultaneous exposure of multisensitive layers of photographic paper, exposure of each layer being easily and accurately controlled.
It is a further object of this invention to provide a new and improved color head which provides a white light source composed of color components of blue, green and red with each of the colors being individually controlled without affecting the other and with each color falling within a wave length band which does not overlap the adjacent color or extend substantially above or below the visible region of wave lengths.
It is a still further object of this invention to provide a new and improved color head which is adapted to replace the light head of an existing enlarger.
It is a still further object of this invention to provide a new and improved color head which provides a white light source composed of the additive primary colors and which has suiiicient intensity to permit test equipment of relatively low gain to be used in testing the color balance prior to printing, and further which reduces the time of printing by permitting a simplified adjustment of each of the color levels.
It is a still further object of this invention to provide a new and improved photographic enlarger head which is capable of use with existing condenser type systems and further wherein a novel lter means is provided which permits both hard and portrait type prints to be printed on the same apparatus.
Further objects will become readily apparent when reference is made to the accompanying drawings wherein:
FIG. 1 is a perspective view of the color head of the present invention applied to a conventional type condenser enlarger;
FIG. 2 is an elevational view of the color head shown in FIG. l with the shield removed;
FIG. 3 is a top plan view of the color head as shown in FIG. 2;
FIG. 4 is a side elevational view of one of the light source subassemblies;
FIG. 5 is a schematic diagram of the system shown in FIG. l; and
FIG. 6 is a graph of light transmittance (in percent) plotted against wave lengths for the visible region with the solid lines representing theoretical calculations taking into account the limitations of measuring phototube while compensating for the three layer peak response and the dash lines representing one workable set of wave lengths taken from the system of FIGS. 1 5.
Referring now to FIG. l, an enlarger system is represented generally by the reference character 10 including a color head ll having a condenser adaptor i2 at the lower extremity. A condenser system 13 and negative holder 15 of conventional design are disposed above an adjustable length bellows 14 which terminates in a focusing system 16 positioned above an easel schematically represented by the rectangle 1'7.
The color head 1l through use of the condenser adaptor l2 and unique optical design may be used with any known type of system which heretofore has used a single light source- The optical design and geometry of the present invention is such that it terminates and presents the appearance to the condenser assembly of being a single white light point source evenly diffused into a perfect circle while in actuality being composed of three distinct colors of readily identifiable and well defined wave lengths.
Referring now to FIG. 2, the color head 11 is illustrated with the case or shield removed, generally displaying three separate light sources 2l), 2 1 and 22 arranged in vertical relationship above the condenser adaptor 12. Each of the light sources has a'n optical land geometric axis which intersects a common vertically disposed central axis 30 coincidental with the geometric axis of the cylindrical condenser adaptor 12.. Expressed another way, horizontal planes passing through the axis or center of each of the light sources 20, 21 and 22 are vertically spaced and parallel to each other and intersect a vertically disposed central axis 30 at righ-t angles.
The condenser adaptor 12 is broken away in FIG. 2 to illustrate a semisphere subassembly 23 which is also broken away to illustrate the mounting arrangement. The semisphere subassembly includes a mounting tube 24 held in a bracket 25 which is disposed below the light source 2li. The mounting tube 24 houses an aspheric lens 26 at its upper end and a plano-concave or negative lens 27 at its lower end. A diffusing semisphere 28 is suspended from the lower end of the mounting tube 24.
Suitable retaining means may be provided to hold the lens in the position shown with the dimension between the two lenses 26 and 27 being carefully and accurately controlled. When the lower end of the color head 11 is viewed in elevation, the appearance of an ordinary single light source is presented making it suitable to replace a single light source.
As seen in the top plan view of FIG. 3, the sources 2l), 2l and 22 are arranged about a central axis 30, angularly spaced in azimuth by 45. As seen in FIGS. 2 and 3, the central axis 30 is coincidental with the geometric axis of the mounting tube 24 and condenser adaptor 12. The importance of the coaxial arrangement of each of the light sources 2t), 2l and 22 will become apparent.
The angular spacing of the light sources 20-21, among other things serves to allow the separation between each of the individual lamps contained in the light source with- 1n good design geometry in order to facilitate a good cooling or heat dissipation during operation of the enlarger. To enhance this effect, a blower (not shown), is
mounted in a convenient location remote from the er1` larger support or pedestal and supplies cooling air through a flexible tube (not shown) to cool the color head 11. Through the remote mounting, vibrations inherent in the operation of the fan, particularly when it becomes worn from use, will not be transmitted to the enlarger head to cause a vibration during printing.
Referring now to FIG. 4, the light source 21 is illustrated with parts in section to present a clearer understanding of the more detailed features. A light source holder or mount 31 may be formed in any suitable manner by machining, casting or the like. The holder 31 is provided with an upstanding bracket portion 32 which threadably mounts a plurality of thumb screws 33 for movement along their respective axes in response to rotation. The thumb screws 33 at their inner end mount a spherical mirror 34 which may be adjusted towards and away from a lamp 35 mounted in a lamp socket 36 on the light source holder 31. The lamp 35 is of a type known as having a prefocused base so that when inserted in the socket 36, the lament 37 will be in the same location relative to the base for all lamps within a specified close tolerance.
The light source holder 13 is provided with an annular chamber 38 terminating adjacent the lamp 35 in an inwardly projecting flange 4f), counterbored as at 41 to receive a positive meniscus lens 42. An enlarged bore 43 adjacent the lens 42 has an enlarged counterbored portion to form a mount for a double convex lens 44. The lens 42 is held within the counterbored portion on the fiange 40 by a retaining ring 45 while a larger diameter retaining ring 46 holds the double convex lens 44 in its mounting in the counterbored portion of the enlarged bore 43. Each of the counterbored portions is very carefully machined in order that the lenses 42 and 44 may be accurately placed relative to each other and the lamp 35. The positive meniscus lens 42 serves to initiate collimation of the light from the lamp 35 and for convenience will be identified as a first collimator. The double convex lens 44 serves to collect and arrange light rays from the first collimator 42 into parallel rays and will be identified as the second collimator.
As is well known in optics, when theoretically designing a light system, it can be assumed that the light sources are point sources and light is uniformly passed by each lens. However, in actual practice where the sources are lamps, the filaments have a finite dimension, and chromatic aberration is normally experienced. In systems where the light intensity levels are of low order, for all practical purposes the size of the filament can be ignored as well as aberration. However, in an enlarger system such as the present where a high level of light is required, the filament size will run on the order of about several millimeters square. Accordingly, the collimating system shown was developed to accommodate this finite size of the filament and avoid aberration or non-uniformity in the intensity of the beam of light when viewed in cross section.
At the outer end of the bore 43 is provided a filter mounting means or holder 47 which is held in place by suitable mounting means such as the screws 43 received in tappings in the holder 31. Two permanent filters are shown at 5ft and 51 clamped within the filter mounting means 47 and serve to refine the collimated white light from the lamp 35 into a selected color having a wave length falling within selected limits for one of the additive primary color components.
An additional filter 52, which is sometimes referred to as a dichroic filter, is held to machine surfaces 53 and 54 on the light holder 31 by means of screws and clamps 55 and 56 respectively. The dichroic filter 52 is arranged at a perfect 45 angle relative to the collimated light so that the incident and refiection angles are equal to 457 thereby to direct collimated and filtered light through the aperture 57 in the holder 31. The aperture 57 has its cen- 6 ter coaxial with the central axis 30, as do the apertures on the light sources 20 and 22.
The light source 2t? is physically identical to the light source 21, and difiers optically only in the selection of filters to be substituted for equivalent filters 5f), 51 and 52. Similarly, light source 22 is physically identical to light source 21 with the exception that a single filter is substituted for the two filters 5t) and 51, and a dichroic having a different reflectance wave length is substituted for the dichroic 52.
The spherical mirror 54 may be adjusted at the factory to focus the maximum amount of light from the filament 37 of the lamp 35 back to the filament so it is directed toward the first collimator 42. Through the use of a prefocused base 36, the lamp 35 when no longer operative, may be readily replaced by a similar lamp without affecting the optical relationship of the filament 37 relative to the collimating lens system. The collimating lens system, composed of the first collimator 42 and double convex lens 54 forming the second collimator, collimates the light into parallel bundles, directing it to the lters which by selection reject all light above and below selected wave lengths. A better understanding of the optical characteristics and types of lenses and filters will be given when FIG. 5 is described.
The intensity of the lamp 35 may be adjusted by the variable resistance shown schematically at 60. In a typical case this resistor comprises a -ohm 22S-watt resistance to provide a good range of intensity adjustment. Additional resistors may be placed in series and factory adjusted to obtain a reduced operating voltage to the lamp 35 for long life. A preheat circuit may be provided t0 keep the filaments warm and further extend their life. With the arrangement shown, the power to the lamp 35 may be varied to raise and lower the intensity level for purposes noted above.
Ordinarily resistance control of light in enlargers has not been' successfully used in the past even though highly desirable, because it served to change the color temperature of the lamp. For example, the blue colors change at a faster rate than the reds. Due to the novel system of filters, the refined light band is relatively narrow, and any shift of intensity of one color has no effect on the other colors. The advantages of resistance control are self-evident permitting a wide range of intensity levels to be selected with unequaled ease.
In FIG. 5 the enlarger system 10 is illustrated in schematic form and like reference numerals have been given to common elements including the first and second collimators 42 and 44, lamps 35 and mirror 34 of each of the respective light sources 20, 21 and 22. In light source 20, vertical filters 62 and 63 are provided to filter the collimated white light into a band falling between about 610 millimicrons and into the infrared region or about 740 millimicrons. The upper limit will be defined by a subsequent lter. A 45 dichroic filter 64 is arranged in parallelism with the dichroic 52 and disposed in the path of the collimated light so that the angles of incidence and refiection will be equal to 45.
Contrasted with the lower light source 21, the upper light source 22 is provided with a single vertically disposed filter 65 which is sometimes referred to as a 90 filter. The angularly arranged filter or dichroic 66 is located relative to its collimated light source such that the angles of incidence and reflection of the collimated light will be exactly equal to 45 which is parallel to the dichroics 52 and 64. All of the dichroics 52, 64 and 66 are arranged so that the angle of reflection of each will be coincidental with the central axis 30 to provide a refined coaxial white light.
The or transmitting filters 50, 51, 62, 63 and 65 allow only light of a specified or definite wave length to pass and are chosen and identified by their transmittance value. Conversely the dichroics or separating filters 52, 64 and 66 are chosen to refiect only the desired color of light while transmitting or passing all that is not reflected. When figured on the basis of 100%, or perfect transmittance, and contrasted to colored glass, dyes and other type filters, the multi film filters selected absorb practically no light. Their transmittance at any selected wave length in the spectrum is determined by their refiecance at that wave length and accordingly when either of these factors is adjusted, the other increases or decreases in a compementary manner.
In the present system the filter 65 is designed to reflect all visible light above about 480 millimicrons. It transmits a preponderance (90%) of visible light wave lengths falling between about 380 and 425 millimicrons. The associated dichroic or separating filter 66 passes almost all visible light above about 610 millimicrons while wave lengths below this value are reected along the axis 30. The lower range of the spectrum is reflected including ultraviolet rays which may be present, however, these are filtered out as will be seen. A preponderance of refiectance (over 90%) is experienced in the band from about 400 to 560 millimicrons.
Filters 50 and 51 are chosen to transmit vlight having a wave length falling generally between 520 and 600 millimicrons being what is commonly known as the wave length band `for green light. The associated dichroic or 45 separating filter 52 is designed to pass all light above and below the noted wave length and to reflect a band width of about 500 to 590 millimicrons at a 90% reflectance capability. Accordingly, the green color component is well defined and readily identified.
Multi film lters 62 and 63 in the lower light source 20 are chosen to pass all light above about 600 millimicrons including some wave lengths extending into the infrared range. The associated dichroic filter 64 has a reflectance characteristic to reflect virtually all wave lengths above 630 millimicrons at 90% reflectance while transmitting other wave lengths. Accordingly, the separating or dichroic filter 64 serves to trim the lower end of the band by some 30'millimicrons to further separate it from the adjacent green component.
A 90 filter 67 is provided to suppress ultraviolet wave lengths or those wave lengths below about 400 millimicrons passing all visible wave lengths above. A second filter 68 acts as a heat absorber to transmit with about 50% or `greater efiiciency, those wave lengths falling substantially within the visible region between an upper limit of 700 and the lower ultraviolet cut off of 400 millimicrons effected by filter 67. Accordingly, higher value wave lengths of infrared will be substantially suppressed with a small controlled portion passed. Unwanted ultraviolet light which is normally considered to be below 400 millimicrons is sharply cut off.
When the light sources 20, 21 and 22 which are red, green and blue respectively, are energized, refined white light consisting of three identifiable and individually controllable well defined color components will be generated. At printing intensities, each of the colors is non-overlapping with adjacent colors. Light source 22 will provide to the aspheric lens 26 light falling within 400 to 480 millimicrons with a peak transmittance falling slightly below what in theory is identied as pure blue. In a similar manner, the light source 21 will provide the green component of light which will be blended with the light from the blue source 22. This light has a wave length of about 520 to 590 millimicrons with a peak or maxi mum transmittance experienced at about 550 millimicrons as seen in dotted lines in the graph of FIG. 6. The lower light source 20 will provide the red component of light, since it has a wave length of from about 600 millimicrons out into the infrared range slightly in excess of 700 millimicrons.
All three light sources, due to the selection and arrangement of the filters will provide a coaxial band of light of uniform intensity. It can be appreciated that each of the separating filters 52 and 64 has a trimming effect on the color component reflected from the sources disposed above the same. The accurate collimation provided by the unique collimating lens selection and arrangement, directs the light to the filters at the proper incident angle. This is very critical as it avoids resonance conditions which arise when the light strikes the filter at non-unform incident angles, a common occurence when the light is not collimated. The light rays of the three color components are blended together with the unwanted portion of ultraviolet filtered out through the filter 67. The infrared wave lengths are controlled by the suppressor 68 to permit a small percentage to pass to enhance printing.
The aspheric lens 26 is of a special design to focus the blended color components to a focal point which is coincident with that of the negative lens 27, the latter serving to evenly diffuse or spread the light to ll the semisphere 28. If desired, the plane surface of the planoconcave lens 27 may be etched, sand blasted, or the like to provide a diffusing surface to fill the semisphere 28 with light. Obviously, a separate diffuser may be provided as an alternative, however, ideally the diffuser should be as close to the plane surface as possible. The semisphere 28 is a sphere truncated substantially above the geometric center and may also be provided with a diffusing type etch, sand blast, coating or the like on either the interior or exterior surface or both. It serves to diffuse the light evenly to the condenser system 13 containing the usual condenser lenses 71 and 72 both of which are of conventional design and serve the conventional function. When viewing the semisphere 28 back through the edges of the condenser lens, a perfect circle of light is seen which indicates that the light is uniformly received by the condenser system from the source for transmission to the focusing lens 16. Accordingly, more uniformity in intensity at the corners of the print will be experienced.
The negative holder 15 receives the negative and in addition has sufficient vertical clearance to accommodate an additional filter which will be described. A color compensating lens 74 mayalso be provided immediately above the aspheric lens in those situations wherein enlargements of unusual size are to be made. This lens is indicated in the diagram at 74 and includes a planoconcave lens receiving a double convex lens. As indicated, one side of the double convex lens is formed on a greater radius than the side abutting the plano-concave lens. As is well known, chromatic aberration exists in lenses resulting from the differences of the index of refraction at different wave lengths. By the compensating lens 74 formed of glasses having different refractive indices, the focal point of the upper and lower wave lengths are brought into coincidence and the intermediate wave length (green) also coincides fairly accurately. In this manner fall-off or loss of light at the corners of the photograph can be maintained uniform for all sizes. As pointed out previously, the light level around the margin of the photograph is substantially equal to that in the center. In printing pictures in the popular sizes, the color compensating lens is not needed and may be omitted..
In FIG. 6, the solid line represents a theoretical curve of the three additive colors as measured by a spectral photometer, which are arbitrarily assigned a value of percent. The dash lines represent one workable solution to separating the wave lengths by the lens, filter and diffusing system described above. The losses in intensity result from several factors common to optical systems. These include intersurface reiiections, scattering, absorption of light and the performance of the refiecting filters being somewhat less than one hundred per cent or perfect. This loss however is not critical so long as the actual curves are maintained within the given wave lengths, as the level of intensity for each lamp can be individually adjusted.
In operation, when initially set up for printing, an approximation of the color balance to be set on each of the various primary colors must be made. Several prints of a given negative are run in sequence with visually selected for the printing paper used. Printing may now commence.
When changing from the first negative to subsequent negatives the light measuring probe may be placed on the easel and the resistance adjusted to return the meter on the amplifier to Zero for each of the respective colors. Adjustment of one color does not affect the others. In this manner an appropriate color balance for each negative may be rapidly and readily obtained with a single test.
When the supply of paper has been exhausted, and a new supply is opened, the corrective factors given with the new supply may be noted. Compensation for changes in corrective factors relative to the previous box may be readily obtained by appropriate resistance adjustment to add or subtract the numerical color corrective color compensating factor on the meter scale. Printing may resume without the cut and try method to establish a proper color balance. it can be appreciated that color corrective fac* tors will be now more meaningful in the present system since once the desired balance between colors is obtained, corrective factors of new paper supplies may be compensated for through a simple adjustment.
Of considerable importance in the measurement of the intensity of the respective colors in the selection of a wave length which is optimum for exciting the paper, and also within what is known to be the most sensitive range for the measuring phototube. This is a phenomena best illustrated by an example. In the infrared region above 7G01'millimicrons, known types of phototubes are relatively insensitive while the paper is quite sensitive and responsive. Accordingly, the peak of the wave length in red region is controlled by filter selection to fall between the peak response of the known types of'paper which is quite broad, and the responsive wave Ilength of known type of phototubes. The same applies to the selection of peak wave lengths for the other colors in the color source. Accordingly, the wave length of each color at its peak will fall between the peak response of the tube and paper. Accordingly, measurement of the intensity of each color prior to printing can be achieved to predetermine with great accuracy the intensity of the exciting light providing advantages formerly not available.
When portrait work is to be done, a second diffuser is inserted above the negative as at '73 in the space provided. This diffuser is a clear plastic having embossments which diffuse a small portion of the collimated light to illuminate the side walls of negative scratches. When used in combination with the system above described and placed immediately above the negative in a conventional type of condenser enlarger, it provides a soft portrait type diffusion to the print, obliterating minor skin blemishes and the like without interfering with the trueness of the fiesh tones, eye color, hair color and other features.
After a consideration of the foregoing description of the invention, it becomes apparent that the objectives set out above are readily achieved. It will become obvious to those skilled in the art that modifications may be made without departing from the inventive concepts embodied herein. Therefore, only such limitations should be imposed as lare indicated by the spirit and scope of the appended claims.
We claim:
1. A color head adapted for use in condenser type enlargers, said color head comprising three light sources disposed at different elevations, multi film filter means to separate light emitted from each of said light sources into light rays having wave lengths falling within a band identifying separate color components, said multi film filter means including means to blend said separated color components into a coaxial white light ray of transversely uniform intensity, and lens means adapted to receive said coaxial white light and focus the same at a focal po-int coincidental with the focal point of a negative lens means for uniform transmission to a condenser system of an enlarger.
2. The color head of claim ll wherein diffusing means is disposed between said negative lens means and said condenser system of said enlarger, said diffusing means including a semispherical type diffuser.
3. A color head adapted for use in condenser type enlargers, said color head comprising three light sources disposed at different elevations, multi film filter means to separate light emitted from each of said light sources into light rays having wave lengths falling within a band identifying separate color components, said multi film filter means including means to blend said separated color components into a coaxial refined white light ray of transversely uniform intensity, lens means adapted to receive said ycoaxial refined white light and focus the same at a focal point coincidental with the focal point of a negative lens means, first diffusing means adjacent said negative lens means to diffuse said coaxial refined white light, and second diffusing means adapted to diffuse said coaxial refined white light for uniform transmission to a condenser system.
4. A color head adapted to provide refined coaxial light for use in photographic enlargers, said color head comprising a plurality of light sources, means to collimate light from each of said sources into a beam of transversely uniform intensity, a first filter means disposed in the path of each of said collimated light rays to separate light from each of said light sources into one component of three primary colors of red, blue and green, second filter means disposed at an angle to each of said first filter means to reflect and trim light from said each of said first filter means into a more sharply defined component of the primary colors while-simultaneously mixing said components into a beam of coaxial light rays of uniform intensity, and means to diffuse said light rays for uniform transmission to a condenser system.
S. The system of claim i wherein a negative holder is provided below said condenser system `and a diffuser is mounted above said negative holder for use in printing portraits.
`6. A color head particularly adapted for use in condenser type enlargers, `said color head comprising three separate light `sources disposed at different elevations, collimating Imeans adjacent each of said light sources, multi film filter means to separate collimated light from each of said light sources into a single refined light ray, each of said light rays having a -wave length defining one of three color components consisting of blue, green and red, said multi film filter means including means to blend said refined color components into a coaxial and further refined `white light ray of transversely uniform intensity, second lter means in the path of said coaxial white light to reject wave lengths above and below visible wave lengths, lens means to focus Vsaid coaxial refined white light at a focal point -coincidental with the focal point of a negative lens means, first diffusing means adjacent sai-d negative lens means to diffuse said white light, and second diffusing means adapted to spread said light for uniform transmission to a condenser system.
7. The color head of claim 6 wherein said light sources are arranged so that the light source of the green color component is disposed above the light source of the red color component and the light source of said blue color comopnent is disposed above both of the previously `mentioned light sources whereby said means to blend said refined color components into a coaxial refined light ray will further trim each of said color components.
8. A color control head adapted for application to a condenser-type of enlarger, said color control head comprising three light source means arranged in vertically spaced planes, individual intensity control means for each of said light source means, first and second lenses posltioned closely adjacent said each of said light source means to collimate light into parallel rays, the first of said lenses being a positive meniscus lens and the second of said lenses being a double convex lens having the focal point thereof coincidental with the focal plane of said first lens, first multi filter means disposed perpendicular to the path of each of said collimated'rays to filter said light into collimated rays having a relatively narrow and identifiable band width, each of said light rays from each of said light source after passing said first lter means having a wave length which differs from the other light source means to provide light of the primary color components, second multi filter means disposed at an angle to each of said collimated and filtered light rays from each of said light sources, each of said second multi filter means being angularly disposed relative to said collimated and filtered light ray-s whereby each of said light rays will be refiected ofi:` of said second multi filter means to form a single light ray of uniform transverse intensity, aspheric lens means disposed in the path of said white light ray to direct said `white light ray to the focal point of a plano-concave lens, a diffusing type means adjacent said plano-concave lens to diffuse said white light ray passing through said plano-concave lens and semispheric means to receive light passing through said diffusing means to further diffuse said light for passage into a condenser system.
9. A color control head adapted for appli-cation to a condenser type of enlarger in lieu of an existing light head, said color control head comprising three light source means arranged one above the other, each of said light source means having first and second lenses disposed adjacent said light source means to collimate light emitted from said light source means into perfectly parallel rays and direct the same to an axis disposed at an angle to said rays, multi filter means disposed in the path of said collimated light to reject all light falling outside a given :band width, whereby three collimated light rays of diverse band widths will be disposed in substantially par-allelism in different elevations, second multi filter means disposed at an angle to each of said collimated and filtered light rays, each of said second multi filter means being angularly disposed relative to said axis and to the collimated and filtered light ray whereby a portion will be reflected off of said second multi filter means, said portion of said light ray reflected off of each `of said multi filter means being directed parallel to said axis in a single coaxial white light ray of uniform intensity, asphericlens means disposed in the path of said white light ray and being adapted to direct the same to a negative lens system having its focal point disposed .at the focal point of said aspheric lens, first diffusing means disposed on one side of said negative lens land a second diffusing means to receive light from said diffusing means and spread it for uniform transmission to a condenser system.
10. A color source adapted to provide refined light composed of three primary additive colors to an enlarger, said color source including first, second and third light sources arranged in parallel planes, each of said light sources including a lamp adapted to emit light of variable intensity, a collimating system adapted to collimate said light emitted from said lamp into anbeam of parallel light rays, first filter means disposed '1n the path of said light rays to reject a portion of said collimated light of an unwanted wave length, second filter means disposed atan angle to said collimated light passed by said first filter means, said second filter means passing all light of an unwanted wave length while reflecting light of desired wave length, said second filter means of said first, second and third light sources being arranged in coaxial parallelism, said second filter means of said second light source being further characterized by passing a preponderance of light refiected from said second filter means of said first light source, said second filter means of said third llight source being further characterized by passing a preponderance of light reflected from the second filter means of said first and second light sources thereby to provide a coaxial refined collimated beam of light, third filter means to further refine said light primarily in the wave lengths outside the visible region, and means to collect and diffuse said refined light for transmission to an enlarger.
11. The color source of claim 1th wherein said means to collect and diffuse said light Iincl-udes an yaspheric lens, and a-color compensating lens is disposed between said aspheric lens and said third filter means to provide uniformity in light intensity when printing enlargements of substantial size.
12. The color source of claim 10 wherein said collirnating system of each of said sources comprises a positive meniscus lens and a double convex lens, said positive meniscus lens being disposed adjacent said lamp, said lenses being adapted to arrange light rays emitted from said lamp into a parallel beam at right angles to said first filter means.
13. A color source adapted to provide refined light composed of additive color components of red, blue, and green, said color source including three light sources disposed at different elevations, each of said light sources including a lamp having a filament with a finite dimension, collimating means to collect unrefined light emitted from said filament and arrange it in parallel rays of transverse uniformity, a first filter means associated with each of said light sources and adapted to reject a portion of said unrefined light while transmitting the remaining portion of said light, a second filter means associated with each of said light sources, said second filter means being disposed in the path of collimated light transmitted by said first filter means, said second filter means associated with each source being arranged in coaxial relation whereby light rejected by each of said second filter means will `be arranged in blended coaxial relation with light rejected 'by each of the remaining filter means, third filter means disposed in the path of said blended coaxial light to further refine the same, and lens means to collect said light and diffuse the same into a semispherical diffusing means for transmission to a condenser system.
14. A color source adapted to provide light having `[blended components each of which is rened to a nonoverlapping wave length, said color source comprising three light sources disposed at different elevations, each of said light sou-rees emitting unrefined light from a filament of finite dimension, a collimating system to collect said light and arrange it in a parallel beam of substantially transverse uniformity, a first multi filter means adjacent each of said collimatingsystems, said rst multifilm filter means refining .light from each of said sources into additive primary colors of refined light having wave lengths corresponding to that of red, blue and green, a lsecond multi film filter means associated with each of said light sources and refiecting the primary colors of light, said second multi film filter means of said red source passing blue and green light from two of said sources, said second multi film filter means of said green source passing blue light from one of said sources, third filter means adapted to reect ultraviolet wave lengths while suppressing infrared wave lengths thereby providing a collimated beam of light -composed of three additive primary colors of readily identifiable and non-overlapping Wave lengths, aspheric lens means adapted to receive said refined light yand direct it to a negative lens means, and semisphere means receiving said light for transmission to an enlarger system.
15. The color source of claim 14 wherein said rst, second and third iilter means provide 'blended red, blue and green light, each of whi-ch has a peak response intermediate that 4of known types of paper to be printed and known types of measuring phototubes.
16. A color head adapted for use in condenser type i enlargers, said color head comprising three light sour-ces disposed at different elevations, multilm filter means to separate light emitted from each of said light sources into light rays having Wave lengths falling Within a hand identifying separate color components, said multi lm filter means including means to blend said separated color components into a coaxial white light ray of transversely uniform intensity, said multi filter means selecting wave lengths in each of sa-id bands of said separate colors which lfall Ibetween the known peak response of the paper to be .printed and that of known types of phototubes, and lens means adapted to receive said coaxial white light and focus the same at a focal point coincidental with `the focal point of a negative lens means for uniform transmission to a condenser system of an enlarger.
References Cited UNITED STATES PATENTS 12/1965 Remesat 88-24 l/l966 Dauser 88-24

Claims (1)

1. A COLOR HEAD ADAPTED FOR USE IN CONDENSER TYPE ENLARGERS, SAID COLOR HEAD COMPRISING THREE LIGHT SOURCES DISPOSED AT DIFFERENT ELEVATIONS, MULTI FILM FILTER MEANS TO SEPARATE LIGHT EMITTED FROM EACH OF SAID LIGHT SOURCES INTO LIGHT RAYS HAVIN GWAVE LENGTHS FALLING WITHIN A BAND IDENTIFYING SEPARATE COLOR COMPONENTS, SAID MULTI FILM FILTER MEANS INCLUDING MEANS TO BLEND SAID SEPARATED COLOR COMPONENTS INTO A COAXIAL WHITE LIGHT RAY OF TRANSVERSELY UNIFORM INTENSITY, AND LENS MEANS ADAPTED TO RECEIVE SAID COAXIAL WHITE LIGHT AND FOCUS THE SAME AT A FOCAL POINT COINCIDENTAL WITH THE FOCAL POINT OF A NEGATIVE LENS MEANS FOR UNIFORM TRANSMISSION TO A CONDENSER SYSTEM OF AN ENLARGER.
US453308A 1965-05-05 1965-05-05 Color source Expired - Lifetime US3336835A (en)

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GB19189/66A GB1142524A (en) 1965-05-05 1966-05-02 Color source
DE19661522310 DE1522310A1 (en) 1965-05-05 1966-05-04 Color head in particular for use in enlarging apparatus

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3492070A (en) * 1964-11-24 1970-01-27 Agfa Gevaert Ag Illuminating system for a copying apparatus
US4025199A (en) * 1974-04-08 1977-05-24 Agency Of Industrial Science & Technology Optical color mixing method
US4754272A (en) * 1986-09-18 1988-06-28 General Signal Corporation Three aspect signalling device using no moving parts
US4786146A (en) * 1987-02-11 1988-11-22 Hughes Aircraft Company Color sequential illumination system for a liquid crystal light valve
US5217285A (en) * 1991-03-15 1993-06-08 The United States Of America As Represented By United States Department Of Energy Apparatus for synthesis of a solar spectrum

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4188111A (en) * 1978-09-15 1980-02-12 Kreonite, Inc. Additive tri-color lamphouse for a photographic printer
FR2489006A1 (en) * 1980-08-25 1982-02-26 Mercier Philippe IMPROVED PUNCTUAL LIGHT PHOTOGRAPHIC ENLARGER

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3222985A (en) * 1963-01-29 1965-12-14 Remesat Armin Projection photographic color printing apparatus
US3227040A (en) * 1962-05-17 1966-01-04 William C Dauser Color head

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3227040A (en) * 1962-05-17 1966-01-04 William C Dauser Color head
US3222985A (en) * 1963-01-29 1965-12-14 Remesat Armin Projection photographic color printing apparatus

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3492070A (en) * 1964-11-24 1970-01-27 Agfa Gevaert Ag Illuminating system for a copying apparatus
US4025199A (en) * 1974-04-08 1977-05-24 Agency Of Industrial Science & Technology Optical color mixing method
US4754272A (en) * 1986-09-18 1988-06-28 General Signal Corporation Three aspect signalling device using no moving parts
US4786146A (en) * 1987-02-11 1988-11-22 Hughes Aircraft Company Color sequential illumination system for a liquid crystal light valve
US5217285A (en) * 1991-03-15 1993-06-08 The United States Of America As Represented By United States Department Of Energy Apparatus for synthesis of a solar spectrum

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Publication number Publication date
GB1142524A (en) 1969-02-12
DE1522310A1 (en) 1969-09-25

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