EP1567912A2

EP1567912A2 - Optimisation of the illumination of a projection appliance

Info

Publication number: EP1567912A2
Application number: EP03812170A
Authority: EP
Inventors: Harald Lang; Soeren Dambach
Original assignee: Barco Control Rooms GmbH
Current assignee: Barco Control Rooms GmbH
Priority date: 2002-12-04
Filing date: 2003-12-03
Publication date: 2005-08-31
Also published as: US20060256295A1; WO2004051993A3; DE10256506A1; WO2004051993A2; US7445344B2; DE10256506B4

Abstract

The aim of the invention is to be able to adjust the position of optical components of a projection appliance (1), especially a rear projection appliance of a projecting screen, said projection appliance comprising a light mixing rod (8). To this end, an adjustment reflecting mirror (19) which can be adjusted by means of servomotors (23) is arranged in the illumination path of the image producer (11) between the lamp (3) and the light mixing rod (8).

Description

Optimization of the illumination of a projection device

The invention relates to the optimization of the illumination of the imaging device in projection apparatus. Projection devices are used to project an image onto a projection screen. The invention is directed to projection apparatuses which comprise an image generator for displaying the image on a reduced scale, an illumination unit with condenser optics and / or a (preferably focusing) lamp reflector (for example in an elliptical or more complex form) for illuminating the image generator and a projection lens Projection device for magnifying imaging of the image represented by the imager on the projection screen. Such projection apparatuses also include a spatial light mixing device for compensating for local differences in the brightness distribution. As a rule, the image generator and / or the projection device for adjusting the position of the projected image on the projection screen is fastened in or on the projection apparatus in a position that can be adjusted with adjustment elements.

A distinction is made between incident light and rear projection devices. One difference between reflected light projectors and rear projection systems is that in rear Projection devices usually contain other optical elements such as deflecting mirrors and projection screens, which are not used in incident light projectors.

Both incident light and rear projection devices are used to display an image on a large-scale projection screen. The imaging device can be a transmitted light imaging device, that is to say an imaging device that is transmissively illuminated by an illumination unit for illuminating the imaging device, or a reflecting imaging device that is illuminated by the illumination unit. According to the prior art, for example, transmitted-light liquid-crystal imaging devices or reflective polysilicon or liquid-crystal imaging devices or DMDs (Trademark of Texas Instruments Inc., digital micromirror device) are used.

A lighting unit for illuminating the imaging device or for illuminating the transmitted light imaging device generally comprises a light source, a reflector and a condenser lens system with one or more condenser lenses for illuminating the imaging device. Furthermore, light mixing devices and further imaging optical elements, for example for optimally illuminating a rectangular image format, can additionally be provided. The condenser optics can also be dispensed with when using a focusing, for example elliptical, lamp reflector. The projection device or the lighting unit is either integrated into the projection apparatus or attached to it. A projection apparatus is thus a closed, complete unit for displaying an image, a screen for viewing the image being integrated in a rear projection apparatus. Rear projection modules in particular are widely used in cases where a complex image, for example consisting of various video or computer images, is to be displayed over a large area. Widespread areas of application for such rear projection apparatus are screens which are viewed by several people at the same time. Large screen rear projection is particularly widespread in modern control room technology.

If the image displayed should exceed a certain size and complexity given the quality requirements, this is no longer possible with a single rear projection module. In such cases, the image is composed of partial images, each of which is displayed by a rear projection module. In this case, the image displayed by a rear projection module is a partial image of the overall image of the screen displayed by all rear projection modules.

According to the state of the art it is possible to have a large one

Number of rear projection modules in a modular structure of a projection screen and / or stack one above the other in order to display a large image composed of many individual partial images. The number of rear projection modules that are put together to form a projection screen is up to 150 or more.

Further details on rear projection modules can be found in document EP 0 756 720 B1, to which reference is hereby made.

Projection devices, in particular on projection screens constructed modularly from a plurality of projection devices, are used in high demands in many cases. The following problems have to be overcome.

A particular problem consists in achieving and maintaining a certain ^'and uniform brightness of the image or of the images. The lamps used in the different projection devices, which in many cases are high-performance lamps, have a different basic brightness and a different position of the arc. Both sizes also change over the life of the lamps in an aging process that is individual for each lamp. This requires a repeated, complex adjustment of the individual projection devices in order to achieve homogeneous illumination of the projected image and thus a uniform representation on a screen - with the maximum possible light output.

In particular in the case of projection apparatuses which project a partial image of an overall image, the position of the image generated by the image generator and projected by means of the projection lens on the fixed projection screen must be adjusted very precisely, so that the overall image, which extends over several partial images, is as free of directories, seamless and as free of webs appears. For this purpose, according to the prior art, the projection apparatus is constructed with a highly stable and inherently rigid framework, into or on which an also mechanically rigid imaging module is inserted or attached, which includes the lighting unit and the projection device. Adjustment elements are provided by means of which the position of the image generation module for setting the position of the projected image relative to the frame can be adjusted. In order to meet the required high precision, complex and massive mechanical components are used according to the state of the art in order to create mechanically stable components and to be able to adjust them precisely. For example, multi-axis adjustment devices or adjustment tables, for example optical cross tables, or complex adjustment devices such as, for example, according to document DE 198 24 917 AI are proposed.

The adjustment devices previously used in practice also have the disadvantage that adjusting the position of the projected image with them is extremely tedious and lengthy, since when an adjustment element is adjusted, image position changes also occur which can also be achieved with other adjustment elements. The individual adjustment elements of an adjustment device are therefore not without interaction with one another, but when adjusting an adjustment element it is necessary to also readjust individual or more other adjustment elements. In practice, this means that in a lengthy iteration process that can last for hours, the adjustment elements have to be repeatedly adjusted in order to achieve the desired image position. This is not only very complex for the initial adjustment of a projection apparatus, but also for a possible transport or a maintenance or repair measure.

In principle, the smaller the image generator, the smaller the projection apparatus could be due to the scaling laws of optical structures. A reduction in the size of the projection apparatus would ultimately make it possible to simplify the adjustment mechanism and the effort required to adjust it. According to the current development trend, the imaging providers are getting smaller and smaller, and it can be assumed that the development in this direction tergeht. This trend is opposed to the fact that the high-power lamps used in projection devices, which are mostly discharge lamps, cannot follow this trend; in particular because of their high operating temperature, they cannot be reduced significantly further without losing the desired service life.

For this reason, also progresses miniatur- the imager or a ^'imager projection device containing ization the size of the associated lighting unit hardly decrease, so that the high expenditure of mechanical adjustment of the projection apparatus is maintained.

In order to solve these high technical requirements, various state-of-the-art methods are used, which, however, do not completely solve the problems mentioned: - In order to achieve optimal illumination of the imaging device, the lamps are selected to a high degree in order to achieve minimal manufacturing tolerances that cannot be undercut to overcome. This is complex and involves high costs. - A brightness and homogeneity comparison is carried out during the installation of a projection apparatus or a screen and / or at fixed service intervals. The brightness distribution is measured on the screen. This is complex and cost-intensive, requires trained personnel and requires an interruption of ongoing operations. Image quality may deteriorate between service intervals. Taking into account the average change in luminous flux during the operating period based on experience. However, the deviation of individual lamps from an average time-dependent change in light current is so great that they lead to visible image artifacts without individual correction.

A determination of the luminous flux by measuring the lamp power by means of electrical measurement of the lamp current and lamp voltage. But only a small part of the available lamp drivers allows such an electrical measurement. In addition, due to the change in the size and position of the discharge arc, the light output emitted by the projector is only correlated with the total light output of the lamp to a first approximation. The one that characterizes the arc

Burn-up of the lamp electrodes differs from lamp to lamp in such a way that the assumption of a medium burn-up is not very useful.

A manual entry of a time-dependent change in luminous flux and homogeneity to be taken into account by the user. However, this requires appropriate training of the user and the activation of special image content, which disrupts continuous operation. - Electronic compensation by modifying the image content. However, this is accompanied by a disadvantageous reduction in the contrast and, moreover, no compensation for differences in brightness in the case of dark image content is possible. - The maintenance of projection apparatuses often requires that they be removed from their installation location or parts of the lighting unit from the projection apparatus. As explained above, this results in a complex new stage in commissioning. In the case of projection screens, the brightness is adjusted using the faintest projection device. Since the brightness of the individual projection apparatus fluctuates greatly due to the lamp tolerances with regard to total luminous flux and discharge arc lamp, there are large differences in brightness between the brightest and darkest element of a screen. The adjustment inevitably leads to a low overall light yield.

A video projector is known from document DE 198 19 245 C1, in which two deflecting mirrors are arranged between the light source and the image generator and a rod-shaped light mixing device is arranged between the deflecting mirrors. The deflecting mirror on the light entry side of the light mixing rod is fixed. The deflection mirror arranged on the light exit side of the light mixing rod can be adjusted with adjusting elements to adjust the outcoupling of the light emerging from the light mixing rod. The adjustment elements include screws that are loosened for adjustment. The adjustment is made by rotating the deflecting mirror and by moving the deflecting mirror towards or away from the image generator. This adjustment is used exclusively for the geometric alignment of the image of the exit surface of the light mixing rod on the imager. An adjustment or optimization of the light emitted by the light source on the entry surface of the light mixing rod, in particular by adjusting angles of the beam path, is not possible with the known device.

Taking this prior art into account, the object of the invention is to enable satisfactory illumination of the image generator in the above-mentioned projection apparatus. This task will solved according to the invention by a projection apparatus with the features of the attached independent device claim or by a method with the features of the attached independent method claim. Preferred refinements and developments of the invention result from the dependent claims and the following description with associated drawings.

A projection apparatus according to the invention for projecting an image onto a projection screen thus comprises an image generator for displaying the image on a reduced scale, an illumination unit with a lamp and condenser optics and / or a lamp reflector, preferably a focusing lamp reflector for illuminating the image generator, and a projection lens Comprehensive projection device for enlarged imaging of the image represented by the image generator on the projection screen and a spatial light mixing device for compensating for local differences in the brightness distribution, and according to the invention it has the special feature that it has an adjustable adjustment deflection mirror arranged in the illumination path of the image generator for adjusting the illumination of the imager, the position of which is defined by the tilt angle by changing the tilt angle, in particular the polar and azimuthal angle of the reflected beam, mi is adjustable by means of adjusting elements, the adjustment deflecting mirror being arranged in the beam path between the lamp and the light mixing device.

A method according to the invention for adjusting the illumination of an image generator of a projection apparatus and thus for regulating the brightness of the projected image of a projection apparatus for projecting the image onto a projection screen comprising an image generator Displaying the image on a reduced scale, an illumination unit with a lamp and a condenser optic and / or a lamp reflector, preferably a focusing lamp reflector, for illuminating the image generator, a projection device comprising a projection lens for magnifying imaging of the image represented by the image generator onto the A special feature of the projection screen and a spatial light mixing device for compensating for local differences in the brightness distribution is that an adjustable adjustment deflection mirror is arranged in the illumination path of the image generator for adjusting the illumination of the image generator, the position of which is defined by the tilt angle by changing the tilt angle, in particular the polar angle and azimuthal angle of the reflected beam is adjusted by means of adjusting elements, the adjustment deflecting mirror being arranged in the beam path between the lamp and the light mixing device.

Within the scope of the invention it has been found that the illumination of the image generator can be optimized in a particularly advantageous manner by means of such a mirror. By means of the invention, simple adjustment and adjustment of the luminous flux coming from the lighting unit onto the image generator is possible, and it is the basis for improvements which can also be achieved.

According to a particularly advantageous additional feature, it is proposed that the adjustment deflection mirror be arranged between the condenser optics of the lighting unit or a (preferably focusing) lamp reflector and the image generator. In this case, it can advantageously be additionally provided that between the adjustment deflecting mirror and the image generator further elements of the Condenser optics for illuminating the imager are arranged.

The invention is directed to projection apparatuses which have a spatial light mixing device for compensating for local differences in the brightness distribution. Such light mixing devices for achieving homogeneous or homogenized illumination are known in the prior art. A spatial light mixing device, which extends in the direction of propagation of the light, in particular a light mixing rod, is preferably used here. Light mixing rods are known in the prior art. In this context, reference is made to document US 5,625,738, where both hollow, i.e. based on surface reflection as well as massive, i.e. light mixing rods based on total internal reflection can be used. Known embodiments include e.g. Hollow mixing bars (see e.g. US 5,625,738) and full mixing bars (see e.g. DE 10103099 AI).

The homogenization effect of a light mixing rod, also known as the degree of integration, depends on the ratio of the length to the cross section for a given angular distribution of the lighting. The larger this ratio, the higher the degree of integration. In the case of illumination with an f number in the range from 1 to 1.5, the ratio for a conventional light mixing rod is approximately 5 to 10 with a length of 50 mm. A highly integrating mixing stick is about twice the length, i.e. a ratio of 10 to 20. Since the enlargement of the

Ratio increases the average number of reflections inside the light mixing rod, this results in higher reflection losses and thus a lower light output when using hollow light mixing rods with a metallic reflection layer. For this reason and because of the The practically available space for the installation of the light mixing rod is therefore limited in the degree of integration that can be achieved in practice.

In the case of a projection apparatus according to the invention which has a light mixing device, the adjustment deflection mirror which can be set according to the invention is arranged in the beam path between the lamp and the light mixing device. The amount of that emitted by the lamp can then be adjusted by means of the adjustment deflecting mirror. Light that is coupled onto the light entry surface of the light mixing device can be adjusted.

An advantageous further development can consist in that the projection apparatus has an illumination sensor for

Determination of the intensity of the illumination of the imaging device comprises by the lighting unit. This illumination sensor is preferably arranged so that it can be used to determine the illuminance regardless of the image content. With the measured values of such an illumination sensor, it is possible to adjust and align the projected image or the projection apparatus in a simple manner.

Another advantageous embodiment can consist in that the lighting unit is arranged in a lighting module and the projection device in a separate projection module. In this context, a module is understood to mean an interchangeable, complex part of the projection apparatus which forms a closed functional unit. It comprises an independent mechanical basic construction, for example a profile frame, possibly a housing, and can be assembled and adjusted separately. The design according to the invention of a projection apparatus with an adjustment deflecting mirror creates the prerequisite for designing the modules in an arrangement which is particularly advantageous in practice, which in particular simplifies the mechanical-optical adjustment of the projection module and service work on the lighting module while maintaining a high luminous efficiency.

Particular practical advantages of the invention result from the fact that the brightness adjustment can be carried out in a simple, quick and uncomplicated manner, if necessary also during operation. It is also advantageous that in a further embodiment of the invention, no additional measuring devices or deployments by trained personnel are required because the adjustment can take place automatically. For this reason, no significant disruption or interruption of ongoing operation is required, and even when using lighting units with a double lamp module to ensure uninterrupted operation in the event of a lamp failure due to switching to the second lamp, the adjustment is immediate possible.

The invention thus achieves goals for which experts have long sought. In order to be able to achieve particularly good results, the following measures are preferably used individually or in combination with one another.

The arrangement according to the invention of a just deflecting mirror can be used particularly advantageously in projection apparatuses in which the image generator can be controlled pixel by pixel and the projection apparatus for realizing the time-sequential additive color mixing. bles color filter - hereinafter referred to as dynamic color filter - for generating primary colors. The imager is preferably a digital micromirror device (DMD). A preferred embodiment of a dynamic color filter is a rotating color wheel.

Many commercially available projectors, such as video projectors, use separate channels for each of the three primary colors. Such a system requires an imager and optical lines for each primary color »which must converge on the screen with pixel accuracy. Novel projection apparatuses use only one image generator based on the time-sequential additive color mixture, the entire image being broken down into three single-color partial images with respect to the primary colors red, green and blue. The imager is sequentially illuminated with the primary colors. The image data to be displayed are sent to the image generator in accordance with the color just reaching the image generator. The eye combines the colored partial images into a single full-color image. The eye also combines successive video images and video partial images into a full motion image.

Such a system requires a device for sequentially illuminating the imager with primary colors. The simplest way to set up a dynamic color filter suitable for this is a rotating color wheel, which is used to filter out the desired color from the white spectrum of a lighting unit.

Color wheels of this type for changing the color of the light coupled out from the projection lamp are generally produced from dichroic filters. However, the filters have deviations in their production spectral filter characteristics, which are expressed in that the edge positions of the filters differ. As a result, there are differences in the perception of the primary colors and the mixed colors.

The image generators currently used in connection with time-sequential image generation are so-called digital micromirror devices, which are described, for example, in US Pat. No. 5,079,544. They include an arrangement of small movable mirrors for deflecting a light beam either towards the projection lens (on) or away from the projection lens (off). A gray scale can be achieved by quickly switching the pixels represented by the mirrors on and off. The use of DMDs for digitizing light is also known as DLP (Digital Light Processing). A DLP projection system comprises a light source, optical elements, color filters, digital control and formatting, a DMD and a projection lens.

A digital micromirror device (DMD) is preferably used as the imager in the time-sequential additive color mixing. However, other image generators, for example those mentioned at the beginning, can also be used within the scope of the invention.

The dynamic color filter for the time-sequential generation of primary colors is advantageously a color wheel. However, other corresponding devices currently or future available can also be used within the scope of the invention.

In particular in the case of such projection apparatuses with a time-sequential color mixing, it is known to provide spatial light mixing devices in the form of a light mixing rod use. With the invention it is possible to improve the coupling of light into the light mixing rod and to facilitate the adjustment.

However, the invention cannot only be used for DLP imagers (lchip), i.e. can be used in connection with a color wheel. 3chip (based on LCD or DMD) solutions are also conceivable. No color wheel would be used here. The color splitting then takes place behind the light mixing rod.

The invention is explained in more detail below with reference to exemplary embodiments shown in the figures. Special features described therein can be used individually or in combination with one another in order to create preferred embodiments of the invention. Show it:

1 is a schematic representation of components of a projection apparatus according to the prior art,

2 shows the adjustment of the projection apparatus from FIG. 1,

3 shows the condenser optics and the light mixing rod from FIG. 1,

4 shows the light entry surface of the light mixing rod from FIG. 3, FIG. 5 shows the brightness distribution at the output of the light mixing rod from FIG. 3,

6 an adjustment deflecting mirror according to the invention with a light mixing rod,

7 shows the light entry surface of the light mixing rod from FIG. 6 without correction,

8 shows the brightness distribution at the output of the light mixing rod according to FIG. 7, 9 shows the light entry surface of the light mixing rod from FIG. 6 with correction,

10 shows the brightness distribution at the output of the light mixing rod according to FIG. 9, FIG. 11 shows an adjustment deflecting mirror according to the invention with an illumination sensor, adjusting elements and a control device,

12 shows a projection apparatus according to the invention with an illumination module and a projection module and

13 shows a projection apparatus with a decoupling element.

FIG. 1 shows the optical components of a projection apparatus 1 according to the prior art. It comprises an illumination unit 2 with a lamp 3 as the light source, preferably a discharge lamp, and condenser optics 4. A dynamic color filter 5 in the form of a color wheel 6 and a spatial light mixing device 7 in the form of a light mixing rod 8 extending in the direction of propagation of the light follow in the beam path. The light entry surface 13 of the light mixing rod 8 is located in the or. in the immediate vicinity of the focal plane of the condenser optics 4 or the focal plane of a focusing lamp reflector. The light emerging at the light exit surface 14 of the light mixing rod 8 is imaged on an imager 11 by means of imaging optics 9, which is also referred to as relay optics.

The image generated by the image generator 11 is enlarged by means of a projection lens 12 of a projection device 10 and is projected onto a projection screen (not shown), that is to say projects the image from the image generator 11 Image generated in transmission or reflection on a projection screen, not shown. In a preferred application of the invention, the projection apparatus 1 is a rear projection apparatus, and the image projected by the projection objective 12 is a partial image of an image wall containing a plurality of projection apparatuses or rear projection apparatuses.

The projected image is constructed using the time-sequential mixture of successive monochrome partial images in the primary colors red, green and blue. The sequence can also contain a fourth partial image in black and white, which is mixed in to increase the image brightness. ill. The sequence of the partial images follows at a sufficiently high speed that the eye cannot follow the color change and a physiological color mixture takes place.

The color wheel 6 is used to generate the primary colors red, green and blue from the white light of the lamp 3 for illuminating the image generator 11. Imager 11 is preferably a DMD. With appropriate synchronization, the imager 11 can generate the monochrome partial images, which are composed by the eye of the viewer of the projected image.

The light from the lamp 3 is focused on the entry of the light mixing rod 8 by means of the condenser optics 4. The rotating color wheel 6 has segments of different colors in the primary colors which, depending on the rotational position of the color wheel 6, transmit the spectral components of the lamp 3 in accordance with the color filter currently in the beam path. The light mixing rod 8 ensures homogenization of the illumination, and the imaging optics 9 form the light distribution at the exit of the Light mixing rod 8 on the imager 11. The color wheel 6 is arranged in the vicinity of the input or the output of the light mixing rod 8.

The basic brightness of the projected image, i.e. the brightness of an image with fully white image content depends on the luminance at the location of the imager 11. Because of the problems mentioned at the outset, it is therefore desirable to optimize the luminance at the location of the imager 11. Apertures 15 or other methods can then be used to adjust the brightness in practical operation.

As explained at the beginning, the setting and adjustment of the optical components in FIG. 1 must be highly precise in order to achieve a high luminous efficacy and precise imaging. This is illustrated in FIG. 2 on a projection apparatus 1 according to the prior art, which has to be adjusted in six degrees of freedom on a fixed projection screen 17. It comprises an illumination unit 2 and a projection device 10. The illumination unit 2 contains one or more lamps, the lamp drivers and one or more power supply units. It takes up most of the projector's mass and volume. In addition to the imager 11 and the projection objective 12, the projection device 10 contains only a few optical elements and only requires a smaller part of the projector mass and the volume.

The mass or volume ratio will be even more extreme in the future due to the miniaturization of the image generators 11. Since the lamps 3 developed for continuous operation with a long service life are difficult to downsize due to thermal boundary conditions, no significant miniaturization of the lighting unit 2 is to be expected. The The trend towards using double lamp solutions to increase operational safety even calls for the lighting units to be enlarged.

The lighting unit 2 and the projection device 10 are arranged in a common housing according to the prior art. For adjustment, the entire unit is aligned in six degrees of freedom using adjustment elements. This is very complex and must be carried out again in the event of a service measure.

Another problem, which is only insufficiently solved according to the prior art, is explained with reference to FIGS. 3 to 5. FIG. 3 shows an illumination unit 2 with a lamp 3 and condenser optics 4 and a light rod 8. In order to achieve a high light yield, precise focusing on the light entry surface 14 is necessary.

The discharge lamps 3 used, however, typically show fluctuations in the position of the discharge arc 18 due to production, operation and aging. FIG. 3 shows the position of a misaligned discharge arc 18 for illustration purposes.

If the incorrect position of the discharge arc 18 is not corrected, there is a shifted illumination, illustrated in FIG. 4, at the light entry surface 13 of the light mixing rod 8. As a result, the coupling efficiency is reduced on the one hand, ie there is a reduced overall brightness of the projection apparatus 1. On the other hand, the asymmetrical result Illumination of the light entry surface 13 to form an inhomogeneous light distribution on the light exit surface 14. This is due to the fact that the light mixing occurs only to a limited extent due to the finite length of the light mixing rod 8. Given the length of the light mixing rod 8, for reasons of symmetry the highest homogeneity at the light exit surface 14 can only be achieved with symmetrical illumination of the light entry surface. In order to achieve a sufficient degree of homogeneity at the light exit surface 14, taking into account asymmetrical illumination of the light entry surface 13, a much longer and therefore usable light mixing rod would be required in practice than with symmetrical illumination. The brightness H on the projection screen 17 can have spatial fluctuations such as brightness gradients.

The above-described disadvantages of adjusting and correcting the brightness of projection apparatuses according to the prior art are eliminated by the arrangement of an adjustment deflecting mirror according to the invention or made possible in a further embodiment by such an adjustment deflecting mirror. The mode of operation of the invention is explained in more detail in FIGS. 6 to 1 °.

FIG. 6 shows an illumination unit 2 with a lamp 3 and condenser optics 4. Furthermore, an adjustable deflection mirror 19 according to the invention is shown. By using a Just deflecting mirror 19, two tolerance problems can be solved simultaneously:

A lateral deviation of the discharge arc 18 from the optical axis 21 results in asymmetrical illumination at the light entry surface 13 of the light mixing rod 8 (FIG. 7). As a result, an inhomogeneous light distribution at the light exit surface before 14 (Figure 8) with reduced overall efficiency.

The illumination of the light entry surface 13 of the light mixing rod 8 can be centered by adapting the two-dimensional setting angle of the adjustment deflection mirror 19 (FIG. 9). This results in an increased coupling efficiency and also a far more homogeneous light distribution on the light exit surface 14 (FIG. 10) of the light mixing rod 8.

The same problem arises when the light mixing rod 8 is shifted or tilted with respect to the optical axis 21. Even in such a case, the illumination of the light entry surface 13 can be centered by adapting the adjustment deflecting mirror 19 and thus improving the efficiency and homogeneity of the light transmission. This creates the basis for mechanically separating the lighting unit 2 and the projection device 10 from one another in a further embodiment of the invention.

FIG. 11 illustrates a preferred embodiment of a projection apparatus 1 with an illumination sensor 16 for determining the intensity of the illumination of the image generator 11 by the illumination unit 2, preferably independently of the image content. The illumination sensor 16 is located behind the light mixing rod 8 and detects the amount of light emerging at the exit surface 14 of the light mixing rod 8. The sensor signal therefore provides information about the efficiency with which the light from the lamp 3 is coupled into the light mixing rod 8. By evaluating the sensor signal by means of a data evaluation 20, a control loop for setting the two-dimensional angle of the adjustment deflection mirror 19 can be implemented. The adjustment deflecting mirror 19 is tilted by a motor control 22 and driven actuating elements, for example two servomotors 23 or two other actuators depending on the signal of the lighting sensor 16 with respect to its actuating angle.

The adjustment of the adjustment deflection mirror can be carried out automatically by the control device in order to achieve an optimal brightness of the projected image. For example, an automatic scan of the angle settings of the adjusting deflection mirror 19 can be carried out in order to determine an optimum or to approach it iteratively.

In order to improve the sensitivity for finding an optimal setting, one or more diaphragms, preferably two diaphragm diaphragms oriented transversely to one another, can be provided according to a further advantageous feature. The diaphragms can be arranged in the beam path in front of or behind the adjustment deflection mirror 19.

FIG. 12 illustrates a particularly advantageous development of a projection apparatus 1, in which the illumination unit 2 is arranged in an illumination module 24 and the projection device in a separate projection module 25. The image generator 11 and the projection lens 12 are advantageously arranged in the projection module 25, whereas the adjustment deflection mirror 19 and the condenser optics 4 of the lighting unit 2 are arranged in the lighting module 24. If further condenser lenses are provided, these are preferably arranged in the projection module 25. In particular, it can be provided that the lighting module 24 contains two or more lamps to maintain ongoing operation in the event of a lamp defect, that the lighting module 24 contains an electronic lamp driver required for the voltage supply of the lamp 3 and a power supply unit that the lighting module 24 switches on has a larger volume than the projection module 25 or that the lighting module 24 has a larger mass than the projection module 25.

Such a projection apparatus 1 having separate modules 24, 25 is particularly easy to adjust, as was explained further above. To this end, it is advantageously provided that it comprises adjustment means for fine adjustment of the projected image, by means of which the position of the projection module 25 in the projection apparatus 1 can be adjusted, and that the lighting module 24 has a fixed position in the projection apparatus 1 or that it has adjustment means for roughly adjusting the position of the lighting module 25 in the projection apparatus 1.

The use of the adjustable adjustment deflection mirror 19 allows the mechanical separation of the lighting unit 2 and the projection device 10 into separate modules 24, 25. The more massive lighting module 24 can be used in the

Installation of a projection apparatus, for example in a module of a screen, remain in a fixed position, while the smaller projection module 25 is adjusted in six degrees of freedom with respect to the fixed projection screen 17.

This has the following advantages:

Due to the lower mass to be adjusted, the adjustment mechanism can be designed to be much less massive and less complex, that is to say, more cost-effective. The adjustment is simplified for the personnel commissioned with the installation.

Most service-relevant modules can be accommodated in the fixed lighting module 24. A misalignment of the projection module 25 and the necessary readjustment are therefore far less likely in the event of service.

The modularity of lighting module 24 and projection module 25 also enables, for example, a complete exchange of the lighting module 24 with the projection device 10 remaining adjusted in the projection module 25, so that after a service measure has been carried out on the lighting module 24, the lighting module 24 or a replaced lighting module into the projection apparatus 1 can be used and the projected image can be compared without the projection module 25 having to be adjusted.

FIG. 13 illustrates a further advantageous embodiment of a projection apparatus 1, in which a further lighting condenser for illuminating the image generator 11 can be arranged between the adjustment deflecting mirror 19 and the image generator 11 and which has a spatial light mixing device 7 in the form of a light mixing rod 8 for compensating for local differences in the Brightness distribution.

The adjustment deflection mirror 19 is arranged between the condenser 4 of the lighting unit 2 and the light entry surface 13 of the spatial light mixing device 7. The projection apparatus 1 also has an optical decoupling element 26 for decoupling a part of the luminous flux generated by the illumination unit 2 for illuminating the image generator 11, which see the lighting unit 2 and the imaging device 11 is arranged and the light from the beam path on the way from the lighting unit 2 to the imaging device 11 is coupled. The outcoupling element 26 is preferably arranged between the light exit surface 14 of the light mixing rod 8 and the imager 11. A preferred embodiment of a decoupling element 26 is a partially transparent mirror 27.

The light for the illumination sensor 16 (cf. FIG. 11) is coupled out by means of the partially transparent mirror 27. It can advantageously be provided that the illumination sensor 16 is arranged in an optical plane 28 which corresponds to the illumination plane 29 of the imager 11, that the corresponding planes 28, 29 contain an image of the output of the spatial light mixing device 7 and that the projection apparatus 1 has one Sensor optics 30 comprises, by means of which on the illumination sensor 16 a reduced image of the illumination pattern of the imager. 11 is generated

The advantages of the invention include the following. By using the adjustment deflecting mirror 19, the light yield can be maximized given the lamp tolerances currently given. The fluctuation in light output between individual projection devices can be minimized. This effectively leads to an increased overall light output in a screen. the light beam is centered relative to the light mixing rod 8, which leads to an increased homogeneity of the image illumination. sufficient illumination homogeneity can be achieved even with shorter light mixing rods 8. there is no need to select the lamps 3 used. it is possible to mechanically decouple the projection device 10 and the lighting unit 2 into separate housings or modules 24, 25, the more massive lighting module 24 with the lighting unit 2 remaining unadjusted, fixed and stationary, and the adjustment relative to a fixed projection screen 17 exclusively by the smaller projection module 25. The adjustment mechanism can be made much less solid and less expensive with the same precision. Since the service-relevant components, such as the lamp, lamp driver and power supply unit, are contained in the lighting module 24, the readjustment of the projection apparatus is generally not necessary after the maintenance work has been carried out.

LIST OF REFERENCE NUMBERS

Projection apparatus, lighting unit, lamp, condenser optics, dynamic color filter, color wheel, spatial light mixing device, light mixing rod, imaging optics, projection device, image generator, projection lens, light entry surface to 8 light exit surface to 8 aperture, illumination sensor, projection screen, discharge arc, adjustment deflecting mirror, data evaluation, optical axis, motor control, actuator motor, illumination module, projection module, level coupling element, and optical coupling module to decoupling level sensor

Claims

Expectations

1. Projection apparatus (1) for projecting an image onto a projection screen (17), comprising an image generator (11) for displaying the image on a reduced scale, an illumination unit (2) with a lamp (3) and condenser optics (4) and / or a lamp reflector, preferably a focusing lamp reflector, for illuminating the image generator (11), a projection device (10) comprising a projection objective (12) for magnifying imaging of the image represented by the image generator (11) on the projection screen (17), and one spatial light mixing device (7) for compensating for local differences in the brightness distribution, characterized in that it comprises an adjustable adjustment deflecting mirror (19) arranged in the illumination path of the image generator (11) for adjusting the illumination of the image generator (11), the position of which is defined by the tilt angle by changing the tilt angle, in particular the polar and azimuthal angle of the ref selected beam, is adjustable by means of adjusting elements, the adjustment deflecting mirror (19) being arranged in the beam path between the lamp (3) and the light mixing device (7).

2. Pro ection apparatus (1) according to claim 1, characterized in that the adjustment deflecting mirror (19) between the condenser optics (4) of the lighting unit (2) or a lamp reflector and the imager (11) is arranged.

3. Projection apparatus (1) according to the preceding claim, characterized in that further condenser lenses for illuminating the imaging device (11) are arranged between the adjusting deflection mirror (19) and the imaging device (11).

4. Projection apparatus (1) according to one of the preceding claims, characterized in that the light entry surface (13) of the spatial light mixing device (7) in or in the immediate vicinity of the focal plane of the condenser (4) of the lighting unit (2) or a lamp reflector is arranged.

5. Projection apparatus (1) according to one of the preceding claims, characterized in that the spatial light mixing device (7) is a device extending in the direction of propagation of the light, in particular a light mixing rod (8).

6. Projection apparatus (1) according to one of the preceding claims, characterized in that the adjustment deflecting mirror (19) between the condenser (4) of the lighting unit (2) or a lamp reflector and the light entry surface (13) of the spatial light mixing device (7) is arranged ,

7. Projection apparatus (1) according to one of the preceding claims, characterized in that it has an illumination sensor (16) for determining the intensity the illumination of the imaging device (11) by the lighting unit (2).

8. Projection apparatus (1) according to the preceding claim, characterized in that it comprises an optical decoupling element (26) for decoupling a portion of the luminous flux generated by the illuminating unit (2) for illuminating the imaging device (11), which in the illumination path between the illuminating unit (2) and the imager (11) _. is arranged and the light is coupled out of the beam path on the way from the lighting unit (2) to the image generator (11).

9. Projector (1) after the previous one

Claim, characterized in that the decoupling element (26) between the output of the spatial light mixing device (7) and. the imager (11) is arranged.

10. Projection apparatus (1) according to one of claims 8 to

9, characterized in that the decoupling element (26) is a partially transparent mirror (27).

11. Projection apparatus (1) according to one of claims 7 to

10, characterized in that it comprises drivable adjusting elements (23) for adjusting the position of the adjustment deflection mirror (19) and a control device by means of which the position of the adjustment deflection mirror (19) can be adjusted as a function of the signal from the lighting sensor (16).

12. Projector (1) after the previous one

Claim, characterized in that the adjustment of the Adjustment deflecting mirror (19) is carried out automatically by the control device.

13. Projection apparatus (1) according to one of the preceding claims, characterized in that it comprises one or more diaphragms that can be inserted into the beam path, preferably two diagonally oriented slit diaphragms, for adjusting the adjustment deflection mirror (19).

14. Projection apparatus (1) according to one of the preceding claims, characterized in that the lighting unit (2) in a lighting module (24) and the projection device (10) in a separate projection module (25). are arranged.

15. Projection apparatus according to the preceding claim, characterized in that the image generator (11) and the projection lens (12) are arranged in the projection module (25).

16. Projection apparatus (1) according to one of claims 14 to 15, characterized in that the adjustment deflecting mirror (19) and the condenser optics (4) of the lighting unit (2) or the lamp reflector are arranged in the lighting module (24).

17. Projection apparatus (1) - according to one of claims 14 to 16 and according to claim 3, characterized in that further condenser lenses are arranged in the projection module (25).

18. Projection apparatus (1) according to one of claims 14 to 17, characterized in that the lighting module (24) contains two or more lamps.

19. Projection apparatus (1) according to one of claims 14 to 18, characterized in that the lighting module (24) includes an electronic lamp driver and a power supply unit which is necessary for the operation of the lamp (3).

20. Projection apparatus (1) according to one of claims 14 to 19, characterized in that the lighting module (24) has a larger volume than the projection module (25).

21. Projection apparatus (1) according to one of claims 14 to 20, characterized in that the lighting module (24) has a larger mass than the projection module (25).

22. Projection apparatus (1) according to one of claims 14 to 21, characterized in that it comprises adjustment means for fine adjustment of the projected image, by means of which the position of the projection module (25) in the projection apparatus (1) is adjustable.

23. Projection apparatus (1) according to one of claims 14 to 22, characterized in that the lighting module (24) has a fixed position in the projection apparatus (1) or in that it has adjustment means for roughly adjusting the position of the lighting module (24) in the Projector (1) comprises.

24. Projection apparatus (1) according to the preceding claim, characterized in that after carrying out a service measure on the lighting module (24), the lighting module (24) or an exchanged lighting module in the projection apparatus (1) can be used without an adjustment of the projection module (25) being necessary.

25. Projection apparatus according to one of the preceding claims, characterized in that it is designed as a rear projection apparatus.

26. Screen, comprising a plurality of projection apparatus (1) according to one of the preceding claims.

27. A method for adjusting the illumination of an image generator (11) of a projection apparatus (1) for projecting an image onto a projection screen (17), comprising an image generator (11) for displaying the image on a reduced scale, an illumination unit (2) with a Lamp (3) and a condenser (4) and / or a lamp reflector, preferably a focusing lamp reflector, for illuminating the image generator (11), and a projection device (10) comprising a projection objective (12) for magnifying imaging of the image generator (11 ) displayed image on the projection screen (17), and a spatial light mixing device (7) for compensating for local differences in the brightness distribution, characterized in that an adjustable adjustment deflecting mirror for adjusting the illumination of the image generator (11) in the illumination path of the image generator (11) (19) is arranged, the position defined by the tilt angle by changing the tilt in particular the polar and azimuthal angle of the reflected beam is adjusted by means of adjusting elements, the adjustment deflecting mirror (19) being arranged in the beam path between the lamp (3) and the light mixing device (7).

28. The method according to claim 27, characterized in that it comprises a feature of a projection apparatus (1) according to one of claims 2 to 25.