WO1994027172A1 - Focusing method and apparatus for reading two dimensional optical information sets and the like - Google Patents
Focusing method and apparatus for reading two dimensional optical information sets and the like Download PDFInfo
- Publication number
- WO1994027172A1 WO1994027172A1 PCT/US1994/005381 US9405381W WO9427172A1 WO 1994027172 A1 WO1994027172 A1 WO 1994027172A1 US 9405381 W US9405381 W US 9405381W WO 9427172 A1 WO9427172 A1 WO 9427172A1
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- WIPO (PCT)
- Prior art keywords
- optical
- wedge
- tan
- wedges
- focusing
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Classifications
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/04—Prisms
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements
- G02B7/18—Mountings, adjusting means, or light-tight connections, for optical elements for prisms; for mirrors
- G02B7/1805—Mountings, adjusting means, or light-tight connections, for optical elements for prisms; for mirrors for prisms
Definitions
- the present invention relates generally to focusing systems and more particularly to focusing systems for reading optically readable two dimensional information sets over a substantial range of distances.
- Optically readable information often takes the form of a bar code symbol consisting of a series of lines and spaces of varying widths.
- Various bar code readers and laser scanning systems have been employed to decode such symbol patterns.
- One of the many problems encountered in the bar code reader art, wherein a photosensitive array are utilized, is to produce an optical system capable of focusing images of optically readable information where such information lies at varying distances from the reader.
- Two-dimensional bar code symbols or "portable data files" have recently been developed. With codes of this type access to a database is not required since the code contains the information which would normally be keyed for in a database. Since reliance on a database is not required, information may be accessed and exchanged more readily and reliably. However, in order to decode two-dimensional codes a more sophisticated apparatus is required. This is primarily true since normal vertical code redundancy is not present, making code registration, orientation, and condition very important.
- two dimensional codes may consist of a stack of conventional linear codes. Each line may contain different information, such as (1) pricing information, (2) product name, (3) name of the manufacturer, (4) product weight, (5) expiration date, (6) inventory data, (7) shipping information, and the like. Additionally, a user may require the ability to selectively store or send portions of the decoded bar code symbol.
- the present invention discloses a novel scanner/reader for reading two- dimensional optical information sets.
- the invention includes a housing for supporting a photosensitive array associated with an optical string means which is adapted to focus optical information over a substantial range of distances on the array.
- array and optical string control means for controlling the array and optical string such that the output of selected images on the array may be decoded via computer means.
- FIG. 1 is a schema diagrammatically illustrating the construction of an exemplary optical string of an apparatus for reading optically readable information over a substantial range of distances;
- FIG. 2 is a schema diagrammatically illustrating the construction of an exemplary optical string for reading optically readable information over a substantial range of distances
- FIG. 3 is a schema diagrammatically illustrating the construction of an exemplary optical string for reading optically readable information over a substantial range of distances
- FIGS. 4, 5, and 6 are perspective views illustrating a carrier for motorized focus control of the wedges in accordance with the principles of the instant invention. Best Mode for Carrying Out the Invention
- the present invention utilizes two optical wedges to interpose additional path length into an optical system. Additional path length results from the geometric configuration of the optical assembly and the imposition of differing thicknesses of optical material with refractive indices in excess of one.
- the refractive index is the ratio of the speed of light in a vacuum to the speed of light in a medium. Inserting a material into an optical path has the effect of lengthening that path. By controlling the amount of material inserted into the optical path we may vary the degree to which we can control the effective optical path length.
- the present invention utilizes optical wedges in an articulated symmetrical arrangement. Thus, for any ray path through both wedges, the optical path length for a particular double wedge configuration remains constant.
- Wedge faces need to have zero curvatures. What follows is a face by face analysis of the wedges.
- the face angles are represented by ( ⁇ -,, ⁇ 2 , ⁇ 3 , ⁇ 4 ). Ray directions are represented as ⁇ , and so forth.
- Points of ray intersections at surfaces occur at (x,y) coordinates along the path. The origin is fixed as shown.
- the y coordinate can be found by using either equation. Now x, and y. are known.
- ⁇ 2 is the exit angle expressed as a deviation from perpendicularity
- ⁇ 2 SIN '1 (N 2 SIN( ⁇ 1 + ⁇ 2 )).
- the ray has traversed two distances.
- the second is within the wedge where N 2 >1.00.
- the first distance is from (Xo,y 0 ) to (x,, y,).
- the second is from (x ⁇ y,) to (x 2 ,y 2 ).
- an embodiment of this focusser could be a pair of carriers for the two wedges constrained to move only vertically in slots, driven by an articulation means pivoting between the wedges thus, motion of the first wedge is matched by motion of the second wedge in the opposite direction. In this way, the image planes remain parallel with the object planes.
- a focusing system 10 may be constructed by placing prisms (12, 14) into a motorized carrier.
- the focusing system 10 also includes top prism supports (16, 18) pivotably engaged by first linkage 20 and bottom prism supports (22, 24) pivotably engaged by second linkage 26.
- Linkages 20 and 26 are guided by first and second guides (28, 30) via a servo motor 32.
Abstract
The present invention is a focusing system for focusing optically readable information over a substantial range of distances. The focusing system (10) includes a first optical wedge (12) and a second optical wedge (14) with a reciprocating drive for moving the prisms relative to each other.
Description
FOCUSING METHOD AND APPARATUS FOR READING TWO DIMENSIONAL OPTICAL INFORMATION SETS AND THE LIKE
Technical Field
The present invention relates generally to focusing systems and more particularly to focusing systems for reading optically readable two dimensional information sets over a substantial range of distances.
Background Art
Many industries designate their products with optically readable information.
Optically readable information often takes the form of a bar code symbol consisting of a series of lines and spaces of varying widths. Various bar code readers and laser scanning systems have been employed to decode such symbol patterns. One of the many problems encountered in the bar code reader art, wherein a photosensitive array are utilized, is to produce an optical system capable of focusing images of optically readable information where such information lies at varying distances from the reader.
Known to the art are readers which utilize mechanical means to change the focal length of an optical system. Although such mechanical means may be employed to read optical information over a substantial range of distances, such means are often somewhat cumbersome in design, temperamental, expensive, and require the expenditure of additional battery energy. Thus, in the hand-held optical information reader art, where power consumption, weight, portability, convenience, range, and depth-of-field are of great concern, means for obviating and simplifying focusing requirements have long been sought.
Additionally, conventional bar code symbols have small data storage capacities. This reduces the utility of conventional bar code scanner and reader systems. For example, the 11 digit Uniform Pricing Code found on most supermarket items acts as an identifying number which may be utilized to access information in a
database. Codes of this type do not carry information along their vertical axis, and are therefore, less prone to skewing errors during decoding.
Two-dimensional bar code symbols or "portable data files" have recently been developed. With codes of this type access to a database is not required since the code contains the information which would normally be keyed for in a database. Since reliance on a database is not required, information may be accessed and exchanged more readily and reliably. However, in order to decode two-dimensional codes a more sophisticated apparatus is required. This is primarily true since normal vertical code redundancy is not present, making code registration, orientation, and condition very important.
Several two-dimensional coding standards have been proposed, e.g., Code 49, 16K, Identicode MLC-2D, and Code PDF417. While such codes are capable of storing information such as price, name of product, manufacturer, weight, expiration date, inventory data, shipping information, and the like; apparatus which assist the user in aiming and decoding two-dimensional codes are not currently available.
For example, two dimensional codes may consist of a stack of conventional linear codes. Each line may contain different information, such as (1) pricing information, (2) product name, (3) name of the manufacturer, (4) product weight, (5) expiration date, (6) inventory data, (7) shipping information, and the like. Additionally, a user may require the ability to selectively store or send portions of the decoded bar code symbol.
Therefore, it is a principal object of the present invention is to provide a scanner/reader adapted to selectively read two-dimensional optical information sets over a substantial range of distances. Finally, another object of the present invention is to provide a scanner/reader adapted to selectively read two-dimensional optical information sets which is efficient in operation, simple in construction, easy to use, and trouble free. These and other objects will be apparent to those skilled in the art.
Disclosure of the Invention The present invention discloses a novel scanner/reader for reading two- dimensional optical information sets. In one exemplary embodiment the invention includes a housing for supporting a photosensitive array associated with an optical string means which is adapted to focus optical information over a substantial range of distances on the array. Also provided are array and optical string control means for
controlling the array and optical string such that the output of selected images on the array may be decoded via computer means.
Brief Description of the Drawings FIG. 1 is a schema diagrammatically illustrating the construction of an exemplary optical string of an apparatus for reading optically readable information over a substantial range of distances;
FIG. 2 is a schema diagrammatically illustrating the construction of an exemplary optical string for reading optically readable information over a substantial range of distances; FIG. 3 is a schema diagrammatically illustrating the construction of an exemplary optical string for reading optically readable information over a substantial range of distances; and
FIGS. 4, 5, and 6 are perspective views illustrating a carrier for motorized focus control of the wedges in accordance with the principles of the instant invention. Best Mode for Carrying Out the Invention
1. Description of a First Exemplary Apparatus
It has long been known that optical materials have varying indexes of refraction.
The present invention utilizes two optical wedges to interpose additional path length into an optical system. Additional path length results from the geometric configuration of the optical assembly and the imposition of differing thicknesses of optical material with refractive indices in excess of one. The refractive index is the ratio of the speed of light in a vacuum to the speed of light in a medium. Inserting a material into an optical path has the effect of lengthening that path. By controlling the amount of material inserted into the optical path we may vary the degree to which we can control the effective optical path length. The present invention utilizes optical wedges in an articulated symmetrical arrangement. Thus, for any ray path through both wedges, the optical path length for a particular double wedge configuration remains constant.
Therefore, upward movement of one wedge matches the reciprocal downward motion of the other wedge. Wedge faces need to have zero curvatures. What follows is a face by face analysis of the wedges. The face angles are represented by (φ-,, φ2, φ3, φ4). Ray directions are represented as θ, and so forth.
Points of ray intersections at surfaces occur at (x,y) coordinates along the path. The origin is fixed as shown.
(1) A ray emanating from (x^) has the equation y-Mx+B since the scope of the ray path is the tangent of the ray orientation angle θ0. This becomes y =
TAN(θ0)x+B. But (Xo,y0) is on the ray trajectory so B-y0- TAN θ x,, and Y = TAN(θ0)x + y0- TAN(θ0) x0.
(2) This ray strikes the first wedge face. This face is shown to intersect the origin. The ray's two dimensional projection has the equation y=B.,- C0 + (φ,) x. φ, is the first surface wedge angle. Since (0, 0,) is on the wedge face, B. = 0 and y=-
C KΦJx.
(3) The intersection is defined by the relationship: -COTCφ^x, = TAN(Θ0)X1 + y0 - TAN(Θ0) χ„ -COTtøX - TAN(Θ0)X1 = y0 - TAN(θ0)x0 COTtøX÷ TAN(Θ0)X1 = TAN(θχ - y0
This is the x coordinate of the point where the ray strikes the wedge. The y coordinate can be found by using either equation. Now x, and y. are known.
(4) The ray angular oreintation within the wedge may now be calculated. First, the incidence angle must be calculated. Using an optical wedge, the angle we need is φ θ0 using Snells law, N- x SIN(φrθ0) = N2 x SIN(Θ.,). . = internal ray trajectory deviation from normal path. N1 is 1.00 for this example (air). So N2 = SINCΦ -ΘJ/SINCΘ,) or θ,= SIN-1((SIN(φ1-θ0)/N2.
(5) The exit surface angle is then θ1+φ2 and the equation of the line (ray) is y - Mx+B, or y = TAN(θ1)x+B, and B = y, - TAN(θ1)x1 so y = TAN(θ1)x + y1 - TAN(θ1)x1.
(6) The face projection in 2-D space (orthogonal) for the real face of the wedge falls upon the line y=COT(φ2)x+1B2 in this case is not zero. The geometry of the wedge is defined. Thus, the position (Xo,yc) is known. It falls upon the line. yc = COT(φ2)xc+B2 and then B2 = yc - COT(θ2)x-. So y = COT(φ2) + yc - COT(φ2) xc. (7) The intersection point is then found by setting the two equations equal to each other and solving.
COT(φ2)x + y0-COT(φ2)xc=TAN(θ1)x+y1- TAN(θ1)x1 COT(φ2)x + yc-COT(φ2)xc=TAN(θ1)x+y1- TAN(θ1)x1 COT(φ2)x-TAN(θ1)x = y1-TAN(θ1)x1- yc+COT(φ2)xc x2 = (y1-TAN(θ1)x1-yc+COT(φ2)xc)/(COT(φ2)-TAN(θ1) y2 can then be found by using either equation.
(8) Using Snell's law again N2SIN(θ1+φ2) = N-, SIN(Θ2) N., =1.00 again. N2 > 1.00. θ2 is the exit angle expressed as a deviation from perpendicularity θ2 = SIN'1 (N2SIN(θ1+φ2)).
(9) The ray has traversed two distances. The first is in air where N.,=1.00. The second is within the wedge where N2>1.00. The first distance is from (Xo,y0) to (x,, y,). The second is from (x^y,) to (x2,y2). These are easily calculated.
(10) A ray leaving the optical wedge at (x2,y2) will travel through air to (x3,y3) and then continue on through the second wedge to (x4,y4). The wedges must be pressed into the optical path symmetrically, so as not to skew the focus plane. Their position controls the distances mentioned above.
(11) Forcing the distances to be maximized within the wedges lengthens the optical path by imposing the maximal amount of high index material.
(12) Minimizing the distances traveled in air shortens the distance from object to lens that constitutes an infocus condition. Maximizing the "air distance" lengthens this distance. We have not changed the lens focal length; we have changed the effective lens to image distance. The symmetrical wedge pair avoids focus plane skewing. Positions of the wedges, then, must be adjusted symmetrically.
(13) The equation which governs the point made in item (12) is very familiar; 1/f=1/s.,+1/s2; f is the lens focal length, s, is the object to lens distance and s2 is the lens to image distance, s., will vary, so s2 must vary to achieve an in-focus condition. s2 here can be replaced by V(S__) where U is a value that is based upon wedge position and index of refraction.
(14) Physically, an embodiment of this focusser could be a pair of carriers for the two wedges constrained to move only vertically in slots, driven by an articulation means pivoting between the wedges thus, motion of the first wedge is matched by motion of the second wedge in the opposite direction. In this way, the image planes remain parallel with the object planes.
(15) A provision for independent wedge motion could compensate for skewed codes. 2. Operation
As illustrated in FIGS. 4, 5, and 6, a focusing system 10 may be constructed by placing prisms (12, 14) into a motorized carrier. The focusing system 10 also includes top prism supports (16, 18) pivotably engaged by first linkage 20 and bottom prism supports (22, 24) pivotably engaged by second linkage 26. Linkages 20 and 26 are guided by first and second guides (28, 30) via a servo motor 32.
Claims
1. A focusing system for focusing optically readable information over a substantial range of distances, comprising:
(a) a first optical wedge having at least two surfaces substantially free of curvature, disposed at an acute angle, and wherein said at least two surfaces have substantially equal surface areas;
(b) a second optical wedge having at least two surfaces substantially free of curvature, disposed at an acute angle and wherein said at least two surfaces have substantially equal surface areas, and wherein said second optical wedge is adjacent and in the optical path of said first optical wedge; and
(c) a recipricating drive for moving said first and second optical wedges in relation to each other along an axis substantially perpendicular to the optical axis such that the effective optical path length of said focusing system may be controlled and the image of a optically readable information may be focused upon a photosensitive array.
2. The focusing system of claim 1 , wherein said system further comprises at least one more optical wedge adjacent at least one of said first and second optical wedges and in the optical path of said first and second optical wedges.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US6040593A | 1993-05-11 | 1993-05-11 | |
| US08/060,405 | 1993-05-11 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO1994027172A1 true WO1994027172A1 (en) | 1994-11-24 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/US1994/005381 WO1994027172A1 (en) | 1993-05-11 | 1994-05-11 | Focusing method and apparatus for reading two dimensional optical information sets and the like |
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| Country | Link |
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| WO (1) | WO1994027172A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2004057521A2 (en) * | 2002-12-18 | 2004-07-08 | Symbol Technologies, Inc. | Optical code reader having variable depth of field |
| CN102353389A (en) * | 2011-07-22 | 2012-02-15 | Tcl集团股份有限公司 | System for improving imaging resolution of array detector and realization method for system |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2258903A (en) * | 1939-08-07 | 1941-10-14 | George A Mitchell | Variable focus system for optical instruments |
| SU1456859A1 (en) * | 1985-12-09 | 1989-02-07 | Киевский технологический институт легкой промышленности | Device for checking dielectric losses of substances and materials |
| US4846550A (en) * | 1987-01-07 | 1989-07-11 | Allied-Signal Inc. | Optical wedges used in beam expander for divergence control of laser |
-
1994
- 1994-05-11 WO PCT/US1994/005381 patent/WO1994027172A1/en active Application Filing
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2258903A (en) * | 1939-08-07 | 1941-10-14 | George A Mitchell | Variable focus system for optical instruments |
| SU1456859A1 (en) * | 1985-12-09 | 1989-02-07 | Киевский технологический институт легкой промышленности | Device for checking dielectric losses of substances and materials |
| US4846550A (en) * | 1987-01-07 | 1989-07-11 | Allied-Signal Inc. | Optical wedges used in beam expander for divergence control of laser |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2004057521A2 (en) * | 2002-12-18 | 2004-07-08 | Symbol Technologies, Inc. | Optical code reader having variable depth of field |
| WO2004057521A3 (en) * | 2002-12-18 | 2004-09-30 | Symbol Technologies Inc | Optical code reader having variable depth of field |
| US7025271B2 (en) | 2002-12-18 | 2006-04-11 | Symbol Technologies, Inc. | Imaging optical code reader having selectable depths of field |
| CN102353389A (en) * | 2011-07-22 | 2012-02-15 | Tcl集团股份有限公司 | System for improving imaging resolution of array detector and realization method for system |
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