PROJECTION SYSTEMS WITH ROTATING ANAMORPHOTIC LENSES

Description

TECHNICAL FIELD

[0001] This disclosure relates generally to improving optical projection systems.BACKGROUND

[0002] Digital Light Processing (DLP) projection systems are used for digital cinema throughout the world. Digital Cinema Initiatives (DCI) was formed in March 2002 as a joint project of major motion picture studios to develop a system specification for digital cinema. DLP cinema projectors that adhere to DCI use two formats that are related to how the movie is captured and edited. These two formats are "flat" (also known as "academy") at an aspect ratio of 1.85:1, and "cinemascope" (also known as "scope") that can be as wide as 2.66: 1 but is normally projected at 2.35:1.

[0003] In DLP projector systems, an image is created by a spatial light modulator (SLM), such as microscopically small mirrors arranged in a matrix on a semiconductor chip, known as a digital micro-mirror device (DMD). A DMD is an electromechanical device, whose pixel-generating elements form an array of hundreds or thousands of tiny tilting mirrors. To permit the mirrors to tilt, each is attached to one or more hinges mounted on support posts, and spaced by means of an air gap over underlying control circuitry. The control circuitry provides electrostatic forces, which cause each mirror to selectively tilt. Incident light on the mirror array is reflected by the "on" mirrors in one direction and by the "off" mirrors in the other direction. The pattern of "on" versus "off" mirrors forms an image.

[0004] In most applications, the light from the DMD is projected by a projection lens to a screen. In a projection system with a single DLP chip, colors are produced either by placing a color wheel between a white lamp and the DLP chip or by using individual light sources to produce the primary colors. In a DLP projection system with three DLP chips, a prism is used to split light from the lamp, and each primary color of light is routed to its own DMD chip where it is recombined with the other primary colors and routed out through the lens.

[0005] In liquid-crystal display (LCD) projection systems, a light source emits a beam of intense white light that is passed through an optical integrator (e.g., a fly's eye integrator) which homogenizes the light. The homogenized light is then passed to dichroic mirrors that are coated with a film that are designed to reflect only a specific wavelength of color, resulting in red, green and blue light beams. Some LCD projectors have a separate LED for each color rather than film-coated dichroic mirrors. The red, green and blue light beams are passed through transmissive LCD panels composed of tiny pixels that either block or allow light to pass when triggered by an electric current. The red, green and blue tinted images output by the LCD panels are recombined in a dichroic prism to form a single image composed of millions of colors. The single image is then projected by a projection lens on a screen.

[0006] US 2006 / 0250579 A1 discloses a projection apparatus having an illumination section that provides at least a first, a second, and a third component wavelength illumination. At least two component wavelength modulating sections accept and modulate the component wavelength illumination to provide a modulated component wavelength beam. Each component wavelength modulating section has a portion of a monochrome transmissive liquid crystal modulator panel that has been segmented into at least a first, a second, and a third spatially separate portion. A component wavelength polarizer directs substantially polarized light to the corresponding portion of the monochrome transmissive liquid crystal modulator panel. An illumination path Fresnel lens focuses incident illumination from the component wavelength polarizer through the corresponding portion of the monochrome transmissive liquid crystal modulator panel. An analyzer conditions the polarization of the modulated component wavelength beam. A lens forms an image of superimposed component wavelength beams for projection onto a display surface.

[0007] US 2006 / 0082888 A1 discloses an illumination system for illuminating spatial light modulators of display systems. The illumination comprises a light integrator that comprises at least a movable wall through which the aspect ratio at the exit aperture of the integrator can be adjusted. Alternatively, the illumination system may comprise two juxtaposed light integrators, one of which can be a regular light integrator in prior art, while the other one can be an integrator having at least one movable wall for enabling the adjustment of the aspect ratio at the exit aperture of the integrator. During the operation, one of the juxtaposed integrators is used for collecting and delivering light from the light source according to the aspect ratio of the desired image.

[0008] US 3,015,988 discloses an apparatus for altering an original image of an object as said object appears when viewed from a first angle to provide a resultant image simulating the appearance of the same object viewed from a different angle, comprising in combination, first and second primitive transformation means and uniform magnification means arranged to act upon said original image, the powers and angular orientations of said primitive transformation means and the power of said uniform magnification means constituting adjustable parameters, drive means for adjusting a plurality of said adjustable parameters, and computer means providing signals to control said drive means in accordance with desired changes in viewing angle, said signals being so determined by said computer means that each point of said resultant image will be displaced with respect to the corresponding point of said original image by an amount proportional to the distance of said corresponding point from the horizon of said original image.

[0009] US 2008 / 0259223 A1 discloses systems, equipment and methods that allow the improved tiling of multiple projections displays in order to create higher resolution images. Equipment and methods are disclosed for improved blending of the seam by optical means where edge blending masks are employed to create a brightness ramp in the blending region. Equipment and methods are also disclosed for the correction of artifacts in an optically blended seam by modifying the brightness of image pixels in the overlap or blend region. Equipment, systems, and techniques are disclosed for preserving the resolution and uniformity of the image across each seam by actively controlling the position of each display using a servo controlled lens mount for the positioning of each projected image in conjunction with a real time image analysis system.

[0010] US 2017 / 0227744 A1 discloses first to third lens groups that are formed of anamorphic lenses having positive power and anamorphic lenses having negative power combined with one another and allow the distances between the anamorphic lenses to be changed cooperate with one another to allow field curvature to be changed both in the meridian direction and the sagittal direction.

[0011] JPH06242396A discloses, according to a machine translation thereof, a head loading type video display device having a video display element for displaying a video and a projecting optical system for projecting the video displayed on the element to observer's eyes, an anamorphic optical system consisting of an anamorphic lens, a cylindrical lens, etc., is provided in a photographing optical system, and when the anamorphic optical system is switched so as to be mutually rotated around the optical axis by 90 degrees, both the videos in a normal size and the wide size can be observed.

[0012] JP2017086653A discloses, according to a machine translation thereof, a subjective optometry apparatus including: a light projecting optical system for projecting a target light flux toward a subject eye; a corrective optical system disposed in an optical path of the light projecting optical system to change optical characteristics of the target light flux; and an optical member for guiding the target light flux corrected by the corrective optical system to the subject eye, the subjective optometry apparatus being characterized in that the apparatus comprises: subjective measurement means for subjectively measuring optical characteristics of the subject eye; correction setting means for setting an amount of correction to correct the optical aberration produced by the subjective measurement means, based on the degree of correction of the corrective optical system; and correction means for correcting the optical aberration produced by the subjective measurement means, based on the amount of correction set by the correction setting means.

[0013] US 2003 / 0090635 A1 discloses a system and method for improving asymmetric projection comprising a light source producing a light beam to form a light path, a projection lens disposed in the light path, a light valve inserted in the light path between the light source and the projection lens, and at least one anamorphic surface unit placed in the light path between the light source and the light valve. The anamorphic surface unit offsets a distortion of a light spot resulted from obliquely incidence on the light valve, thus an asymmetric light spot can be improved as a more symmetric one to increase illuminating collection efficiency and uniformity.

[0014] US 2015 / 0077725 A1 discloses an illumination unit includes a light source, an optical mixer to form secondary light sources from a light beam from the light source, and an illumination system to illuminate an optical modulator with the light beam from the optical mixer, including an optical element having an anamorphic surface, in which the optical element is rotated at a certain rotational angle about a rotational axis which is a normal line from a vertex of a surface of the optical element.

[0015] US 2018 / 0313510 A1 discloses a light module for motor vehicle that offers a light source associated with a first part of an imaging system so as to produce a reflected beam coincident with the reflection surface of a high definition pixellated spatial light modulator, which makes it possible to avoid unnecessarily lighting the periphery of the spatial light modulator. The light source consists essentially in one or more light emitting diodes and / or has a punctiform or virtually punctiform appearance. The reflected radiation arrives on a second part of the imaging system, this part characteristically consisting in an optical projection system, some of whose elements can form a back focussing system. The module remains compact and is clearly suitable for providing adaptive lighting in a homogeneous, efficient manner and with high resolution.

[0016] US 2018 / 0284401 A1 discloses a compact anamorphic objective lens assembly. In one example, the objective lens assembly includes a first anamorphic lens group including a first cylindrical lens having a surface optically powered in a first dimension and a second cylindrical lens having a surface optically powered in a second dimension orthogonal to the first dimension, the first anamorphic lens group being positioned to receive visible light along an optical path, a second anamorphic lens group positioned along the optical path to receive the visible light from the first anamorphic lens group, the second anamorphic lens group including a third cylindrical lens having a surface optically powered in the first dimension and a fourth cylindrical lens having a surface optically powered in the second dimension, and an aperture stop centered along the optical path and interposed between the first and second anamorphic lens groups.SUMMARY

[0017] The present invention is defined by the independent claims. Embodiments are defined by the dependent claims. The present disclosure relates to projection systems with rotatable anamorphic lenses.

[0018] The details of the disclosed implementations are set forth in the accompanying drawings and the description below. Other features, objects and advantages are apparent from the description, drawings and claims.

[0019] Particular embodiments disclosed herein provide one or more of the following advantages. Illumination aspect ratios in projection systems are changed (e.g., from 2.35 to 1.85 aspect ratio) using two or more rotatable anamorphic lenses. The change in aspect ratio allows only the pixels showing data to be illuminated on the image plane, and thus increases the brightness of the projected image. Additionally, for DLP projection systems the rotatable anamorphic lenses are used to pre-distort the image projected on the DMD chip, resulting in a more rectangular spatially modulated image.DESCRIPTION OF DRAWINGS

[0020] In the accompanying drawings referenced below, various embodiments are illustrated in block diagrams, flow charts and other diagrams. Each block in the flowcharts or block may represent a module, a program, or a part of code, which contains one or more executable instructions for performing specified logic functions. Although these blocks are illustrated in particular sequences for performing the steps of the methods, they may not necessarily be performed strictly in accordance with the illustrated sequence. For example, they might be performed in reverse sequence or simultaneously, depending on the nature of the respective operations. It should also be noted that block diagrams and / or each block in the flowcharts and a combination of thereof may be implemented by a dedicated software-based or hardware-based system for performing specified functions / operations or by a combination of dedicated hardware and computer instructions. FIG. 1A is a side view of an example illumination system for an optical projection system. FIG. 1B illustrates a typical illumination area showing a parallelogram image of a rectangular integrator rod projected onto an SLM surface. FIG. 2 is a conceptual diagram that illustrates a relay lens system that uses paraxial lenses, showing the orientations of cylindrical optics (rectangular) stretching the image vertically, in accordance with an embodiment. FIG. 3 is a conceptual diagram of the relay lens system of FIG. 2 showing the orientations of the cylindrical optics (rectangular) stretching the image horizontally, according to an embodiment. FIG. 4 illustrates a rectangular illumination spot with cylinder lenses rotated to a first position to reduce distortion, according to an embodiment. FIG. 5 illustrates a rectangular illumination spot with cylinder lenses rotated to a second position to reduce distortion, according to an embodiment. FIG. 6 is a conceptual block diagram of a DLP projection system that uses a relay lens system with rotatable anamorphic lenses, according to an embodiment. FIG. 7 is a conceptual block diagram of an LCD projection system that uses a relay lens system with rotatable anamorphic lenses.

[0021] The same reference symbol used in various drawings indicates like elements.DETAILED DESCRIPTION Overview

[0022] Since a cinema microdisplay has an aspect ratio of 2048 x 1080 (or 4096 x 2160), it does not match the shape of either DCI format, and therefore some pixels are not used. In the case of scope, dozens of rows of pixels on the top and bottom of the microdisplay are not showing any data, yet they remain illuminated by the optics, which currently is optimized to illuminate the whole chip for both formats. In flat projection systems, some columns of pixels are not used, but are illuminated anyway.

[0023] A typical projection system utilizes one of two methods for homogenizing light and creating uniform illumination. The first method uses a rectangular integrator rod (solid or hollow). The second method uses lens arrays that are found in most LCD projectors. For the first method, an image of the rectangular integrator rod is projected on the image plane. For DLP projection systems, the DMD surface is illuminated at a 24 degree angle (from the vertical or y-axis where the z-axis is the optical axis) and a 45 degree clocking angle (from horizontal or x-axis) resulting in some distortion of the image of the rectangular integrator rod. Instead of a rectangle, the projected image is a parallelogram when the imaging optic is telecentric in nature.

[0024] For DLP and LCD projection systems, an anamorphic telescope is placed in the illumination relay optics of the projection system. The anamorphic telescope "compresses" the image of the rectangular integrator rod by a specified amount. The anamorphic optics magnify the image in one axis but make no change to the image size along an orthogonal axis. By using optical integrator of a specified aspect ratio and compression (e.g., 2.08:1 aspect ratio and a compression of 1.13:1), an image on the SLM surface is created with a desired DCI compliant aspect ratio (e.g., aspect ratio of 2.35:1 or 1.85:1) depending on the orientation of the anamorphic optics (e.g., 2.08 x 1.13 = 2.35 and 2.08 / 1.13 = 1.85).

[0025] For DLP projection systems, if cylindrical, anamorphic lenses are placed at the proper orientation with respect to each other (e.g., less than 90 degrees) in the relay lens system, they will pre-distort the image such that the resulting illumination spot on the DMD surface becomes more rectangular. Therefore, in addition to solving the dual-format projection problem for cinema, the rotatable anamorphic lenses can also be used in specific orientations to rectangularize the shape of the illumination in DLP projection systems. This reduces the magnification necessary to illuminate the DMD surface, and improves efficiency by about 8-10%.

[0026] Although the example embodiments disclosed herein are optimized for one color only, a more complex system of optics utilizing various glasses can be used to focus the three primary colors (Red, Green, Blue) onto their respective SLMs simultaneously.Example Embodiments

[0027] FIG. 1A is an example illumination system 100 for an optical projection system. Illumination system 100 includes optical integrator 101, relay lens system 102 and SLM 103. In an embodiment for DLP projection systems, optical integrator 101 is a rectangular integrator rod. A rectangular integrator rod is a hollow or solid internally reflective "light pipe" which uses multiple reflections of a focused light source to obtain homogenization of round or irregular patterns of illumination and convert them into a uniform rectangular pattern. This pattern is imaged onto SLM 103 (e.g., a DMD chip) by relay lens system 102 and then projected to an image plane (e.g., a theatre screen) by a projection lens (not shown). Rectangular integrator rod 101 is used to improve uniformity and efficiently match the aspect ratio of the illumination source to SLM 103. Relay lens system 102 includes relay optics that are used to position the uniform rectangular pattern onto the SLM 103.

[0028] For DLP projection systems, since SLM 103 is illuminated at an angle (from normal) that is typically twice the tilt angle of the micro-mirrors (e.g., 24 degrees for a 12-degree tilt angle device) and a 45 degree clocking angle (from horizontal), there is some distortion in the image on SLM 103. This distortion is typical of rod-based DLP projection systems and reduces efficiency. Relay lens system 200 described in reference to FIGS. 2 and 3 below includes two or more rotatable anamorphic lens to change the aspect ratio of the image projected on SLM 103 (e.g., a DMD chip), and to remove the image distortion, resulting in a substantially rectangular image that utilizes all of the pixels of the aspect ratio. In effect, the anamorphic optics produce a parallelogram-shaped image onto a flat surface, but when this image impinges on SLM 103 at 24 degrees, the parallelogram distortion is canceled. It is desired that the anamorphic ratio (AR) of the cylinder lens group (the ratio of the focal length of the illumination relay parallel and perpendicular to the cylinder axis) satisfies the following conditions: AR > 1 / cos(θ), where θ is the illumination angle of SLM 103, nominally 24 degrees.

[0029] FIG. 1B illustrates a typical illumination area showing a parallelogram image of rectangular integrator rod 101 projected onto SLM 103.

[0030] FIG. 2 illustrates a relay lens system 200 that uses paraxial lenses, showing the orientations of the cylindrical optics (rectangular) stretching the image vertically, in accordance with an embodiment. FIG. 3 illustrates the relay lens system of FIG. 2, showing the orientations of the cylindrical optics (rectangular) stretching the image horizontally, according to an embodiment.

[0031] The exemplary relay lens system 200 shown in FIGS. 2 and 3 includes rotatable, anamorphic lens 201, 202 (forming an "anamorphic telescope"), spherical illumination lenses 203, 204 and SLM 205. The lines shown penetrating the optics in FIG. 2 represent light rays from a light source (not shown). The light source can be any coherent light source, such as white lite, high-power Light Emitting Diodes (LEDs) or lasers.

[0032] In an embodiment, spherical illumination lenses 203, 204 project an image of the rectangular integrator rod (not shown) without affecting its aspect ratio. Anamorphic lenses 201, 202, on the other hand, project a version of the image of the rectangular integrator rod that is compressed along the longer dimension (usually by a factor of two). In the embodiment shown, anamorphic lens 201, 202 are cylindrical lens with any desired surface type, including but not limited to: convex, concave, bi-concave or a combination of convex and concave surfaces ("meniscus" surface type). In an embodiment, doublet elements can be used to reduce light loss and increase the contrast ratio of the displayed image.

[0033] The extent to which anamorphic lens 201, 202, modify the aspect of the image they receive (herein referred to as its "aspect modification ratio") is determined by a number of factors. These include the radius, thickness, and type of glass of each element of the lens. Thus, the same configuration of anamorphic lenses 201, 202 could be modified to have a different optical prescription thereby providing other modification ratios. Anamorphic lenses 201, 202 can be any desired size, so long as the size is sufficient to capture all or most of the light rays from the light source. For example, anamorphic lens 201 can be the same size or a different size than anamorphic lens 202.

[0034] As previously described, the orientation of anamorphic lenses 201, 202 shown in FIG. 2 will "stretch" the image vertically, and the orientation of anamorphic lenses 201, 202 shown in FIG. 3 will "stretch" the image horizontally. Note that the orientations of anamorphic lenses 201, 202 shown in FIG. 3 are rotated by 90 degrees about the optical axis from their orientations shown in FIG. 2. In an embodiment, in which a rectangular integrator rod has an aspect ratio of 2.08:1, and anamorphic lenses 201, 202 provide a compression of 1.13:1, the image projected onto image plane 205 will have a DCI compliant aspect ratio of 2.35:1 or 1.85:1 (as 2.08 x 1.13 = 2.35 and 2.08 / 1.13 = 1.85). Thus, by stretching the image projected onto image plane 205 the illumination of the projection system is changed to allow only pixels showing data to be illuminated, and the brightness of the projected image is increased up to 20%. In practice, the rectangular integrator rod 101 is not exactly the same aspect ratio as the desired illumination spot in the case of DLP illumination, as the image is stretched by impinging on the DMD plane at an oblique angle. In the case of LCD projection, where the illumination is normal to the LCD modulator panel, the aspect ratio of the integrator more closely matches the desired illumination shape.

[0035] In an embodiment, anamorphic lenses 201, 202 are mounted in a lens barrel with bearings or other mechanical devices that facilitate rotation of anamorphic lenses 201, 202 about the optical axis, allowing lenses 201, 202 to be rotated manually or automatically using a suitable control system, as described in reference to FIG. 6. For example, anamorphic lenses 201, 202 can be rotated 90 degrees about the optical axis each time the DCI format needs to be changed. In an embodiment, the anamorphic lenses 201, 202 are mounted on a lens turret mounted on a projector that can be manually or automatically rotated to orientate the lenses about an optical axis. A used herein, an "optical axis" is an imaginary line that defines the path along which light propagates through the projection system, up to a first approximation. As used herein, an "optical path" is the path that light takes in travelling an optical medium or system.

[0036] In DLP projection systems, if anamorphic lenses 201, 202 are placed at certain orientations in relay lens system 200, anamorphic lenses 201, 202 can be used to pre-distort the image projected onto SLM 205, such that the image becomes more rectangular.

[0037] FIG. 4 illustrates a rectangular illumination spot with cylindrical, anamorphic lenses 201, 202 rotated to a first position, according to an embodiment. FIG. 5 illustrates a rectangular illumination spot with cylindrical anamorphic lenses 201, 202 rotated to a second position, according to an embodiment. The first and second positions can be determined empirically using computer-based modeling and simulation for the particular application and projection system illumination optics.

[0038] Therefore, in addition to solving the dual-format projection problem for cinema, the addition of rotatable anamorphic lenses 201, 202 that are rotated in specific relative orientations to each other (e.g., less than 90 degrees), results in a more rectangular shape of the illuminated image in DLP projection systems. The more rectangular image reduces the magnification necessary to illuminate the DMD chip, and improves efficiency by about 8-10%.

[0039] Although the example embodiments disclosed herein are optimized for one color only, a more complex system of optics utilizing various glasses can be used to focus the three primary colors (Red, Green, Blue) onto their respective SLMs (e.g., DMD chips, LCD panels) simultaneously.

[0040] FIG. 6 is a conceptual block diagram of DLP projection system 600 that uses a relay lens system with rotatable anamorphic lenses, according to an embodiment. System 600 is for one color only. Those with ordinary skill in the art would recognize that the DLP projection system can be applied to 3 colors by using a color wheel or Total Internal Reflection (TIR) prism to split the light into primary colors and individual DLD chips for each color. The relay lens system can include separate lens assemblies for each color or three separate relay lens systems can be used to change the format and correct for image distortion.

[0041] System 600 includes light source 601, optical integrator 602, relay lens system 603, spatial light modulator 604, projection lens or lens group 605, lens controller 607, processor 608 and memory 609. The dotted arrows in FIG. 6 represent the optical path. Note that FIG. 6 is simplified for clarity and a practical DLP projection system would include other components, such as a light reflector, mirrors (e.g., folding mirrors, dichroic mirrors, front-surfaced mirror) and / or lenses (e.g., focusing lens, shaping lens, collimating lens, condenser lens) and / or apertures (e.g., vignetting aperture) to direct and / or focus the light rays, diffractive beam shapers, light sink, and a color wheel or prism assembly (e.g., TIR prism) for processing the optical paths of the three primary colors (Red Green Blue).

[0042] In this example embodiment shown, light source 601 illuminates optical integrator 602. In an embodiment, optical integrator 602 is a solid or hollow rectangular integrator rod. Light source 601 can be a high-pressure xenon arc lamp unit, LEDs or lasers. Optical integrator 602 outputs a uniform rectangular pattern, which is imaged onto spatial light modulator 604 by relay lens system 603 and then projected to an image plane 606 (e.g., a theatre screen) by projection lens 605. In an embodiment, spatial light modulator 604 is a DMD, liquid crystal display (LCD) or Liquid Crystal on Silicon (LCoS).

[0043] Relay lens system 604 includes two or more rotatable, anamorphic lenses as described in reference to FIGS. 2 and 3. In an embodiment, the anamorphic lenses are cylindrical. In an embodiment, relay lens system 603 includes a lens barrel for housing the anamorphic lenses and optionally other illumination optics. The anamorphic lenses are mounted in the barrel on bearings or other suitable mechanical devices to facilitate rotation of the lenses in two different orientations, as described in reference to FIGS. 2 and 3. In an embodiment, the rotation of the anamorphic lenses is controlled by lens controller 607 which is controlled by processor 608. In an embodiment, processor 608 also controls the operation of spatial light modulator 604 based on software or firmware instructions stored in memory 609. In other embodiments, a separate processor is used for controlling the operation of spatial light modulator 604 than is used for controlling rotation of the anamorphic lenses in relay lens system 603.

[0044] In operation, a projectionist can use an input device (e.g., a computer graphical user interface) to change formats and to set the angular positions of the anamorphic lenses to remove distortion. The inputs provided by the projectionist are processed by processor 608, which commands lens controller 607 to send control signals to relay lens system 603 to rotate the anamorphic lenses. In an embodiment, relay lens system 603 includes a rotary actuator coupled to a lens holder for holding the anamorphic lens in the optical path and one or more feedback sensors (e.g., angular rate sensor) for providing closed-loop feedback to lens controller 607. Lens controller 607 can be a processor that executes software or firmware instructions or an Application-specific Integrated Circuit (ASIC). Lens controller 607 can implement a state machine and / or a suitable control algorithm to control the rotation of the lenses in a stable manner. In an alternative embodiment, the anamorphic lenses are rotated manually by the user using a hardware mechanism (e.g., a lever) attached to the relay lens system 603.

[0045] FIG. 7 is a conceptual block diagram of an LCD projection system 700 that uses a relay lens system with rotatable anamorphic lenses, according to an example not falling under the scope of the claimed invention.

[0046] Light source 701 emits a beam of intense white light that is passed through optical integrator 702 (e.g., a fly's eye integrator) which homogenizes the light. The homogenized light is passed to dichroic mirrors 703 that are coated with a film that are designed to reflect only a specific wavelength of color, resulting in red, green and blue light beams. In some LCD projection systems, the white light and dichroic mirrors are replaced by red, blue and green LEDs. The red, green and blue light beams are passed through relay lens system 707. The output of relay lens system 707 is input into transmissive LCD panels 708 composed of tiny pixels that either block or allow light to pass when triggered by an electric current. The red, green and blue tinted images output by transmissive LCD panels 708 are recombined in dichroic prism 709 to form a single image composed of millions of colors. The single image is then projected by projection lens 710 onto a screen.

[0047] Relay lens system 707 includes two or more rotatable, anamorphic lens as described in reference to FIGS. 2 and 3. In an example, the anamorphic lenses are cylindrical. In an example, relay lens system 707 includes a lens barrel for housing the anamorphic lenses and optionally other illumination optics. The anamorphic lenses are mounted in the barrel on bearings or other suitable mechanical devices to facilitate rotation of the lenses in two different orientations, as described in reference to FIGS. 2 and 3. In an example, the rotation of the anamorphic lenses is controlled by lens controller 704 which is controlled by processor 705. In an example processor 705 also controls the operation of transmissive LCD panels 708 based on software or firmware instructions stored in memory 706. In other examples, a separate processor is used for controlling the operation of transmissive LCD panels 708 than is used for controlling rotation of the anamorphic lenses in relay lens system 707.

[0048] In operation, a projectionist can use an input device (e.g., a computer graphical user interface) to change formats and to set the angular positions of the anamorphic lenses to remove distortion. The inputs provided by the projectionist are processed by processor 705, which commands lens controller 704 to send control signals to relay lens system 707 to rotate the anamorphic lenses. In an example, relay lens system 707 includes a rotary actuator coupled to a lens holder for holding the anamorphic lens in the optical path and one or more feedback sensors (e.g., angular rate sensor) for providing closed-loop feedback to lens controller 704. Lens controller 704 can be a processor that executes software or firmware instructions or an Application-specific Integrated Circuit (ASIC). Lens controller 704 can implement a state machine and / or a suitable control algorithm to control the rotation of the lenses in a stable manner. In an alternative example, the anamorphic lenses are rotated manually by the user using a hardware mechanism (e.g., a lever) attached to the relay lens system 707.

[0049] While this document contains many specific implementation details, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments. Logic flows depicted in the figures do not require the particular order shown, or sequential order, to achieve desirable results. In addition, other steps may be provided, or steps may be eliminated, from the described flows, and other components may be added to, or removed from, the described systems. Accordingly, other implementations are within the scope of the following claims.

Claims

1. A digital light processing, DLP, projection system (600) comprising: a light source (601); a rectangular integrator rod (602) configured to receive light from the light source and to distribute a uniform pattern of light having a rectangular shape; a relay lens system (603) including two or more rotatable anamorphic lenses, the anamorphic lenses oriented about an optical axis to simultaneously transform the uniform pattern of light into an image having a specified aspect ratio and a relative angle of the anamorphic lenses with respect to each other being less than 90 degrees to pre-distort the image to a parallelogram shape; at least one spatial light modulator (604) configured to receive the pre-distorted image and to direct a spatially modulated image along an optical path, wherein the at least one spatial light modulator is configured to receive the pre-distorted image at an illumination angle θ to cancel the parallelogram distortion and produce a rectangular shape; and at least one projection lens (605) configured to receive the spatially modulated image from the optical path and to project the spatially modulated image onto an image plane (606) with the specified aspect ratio, wherein the two or more anamorphic lenses are cylindrical lenses and an anamorphic ratio, AR, of the anamorphic lenses satisfies the conditions AR > 1 / cos(θ).

2. The system of claim 1, wherein the light source is one or more lasers.

3. The system of claim 1 or 2, wherein the optical integrator has an aspect ratio of about 2.08:1, the anamorphic lenses have a compression ratio of about 1.13:1, and the pre-distorted image received by the spatial light modulator has an aspect ratio of about 1.85:1 or about 2.35: 1.

4. The system of any of the preceding claims 1-3, wherein the anamorphic lenses are configured to be rotated together to a first angular position to stretch the image vertically, and then rotated together to a second angular position to stretch the image horizontally.

5. The system of any of the preceding claims 1-4, wherein at least one of the anamorphic lenses has at least one convex surface arranged perpendicular to the optical axis.

6. The system of claim 1, wherein the illumination angle θ of the spatial light modulator is nominally 24 degrees.

7. The system of any of the preceding claims 1-6, further comprising: a lens controller (607) for controlling rotation of the two or more of the anamorphic lenses about the optical axis.

8. The system claim 7, further comprising: one or more processors (608) that communicate with the lens controller to command the controller to rotate the two or more of the anamorphic lenses about the optical axis, and to control the reflection of the pre-distorted image by the spatial light modulator.

9. The system of any of the preceding claims 1-8, wherein the spatial light modulator is a digital micro-mirror device (DMD).

10. The system of any of the preceding claims 1-9, wherein the specified aspect ratio is compliant with Digital Cinema Initiatives (DCI) illumination format specifications.