Projection system and method using a folding mirror, and integrated rod adjustment

Abstract

This invention provides a projection system and a method for calibrating the same. [Solution] A light source configured to emit light in response to image data; an illumination optical system configured to direct the light, the illumination optical system including an integrating rod and a folding mirror; a digital micromirror device (DMD) including a plurality of micromirrors, each micromirror configured to either reflect the directed light as on-state light to a predetermined position or reflect the directed light as off-state light to an optical dump; determining the deviation between the actual attitude angle and the expected attitude angle of each of the plurality of micromirrors; calculating a first amount of rotational adjustment corresponding to the folding mirror and a second amount of lateral adjustment corresponding to the integrating rod; and acting the folding mirror and the integrating rod according to the corresponding first and second amounts.

Description

Technical Field

[0001] Reference to Related Applications This application claims priority based on U.S. Provisional Application No. 63 / 104,855, filed on October 23, 2020, and incorporates by reference in its entirety the disclosure of that application.

[0002] 1. Field of the Disclosure This application generally relates to projection systems and methods for calibrating projection systems.

Background Art

[0003] 2. Description of the Related Art Digital projection systems typically utilize a light source and an optical system to project an image onto a surface or screen. The optical system includes components such as mirrors, lenses, waveguides, optical fibers, beam splitters, diffusers, spatial light modulators (SLMs), etc. The contrast of a projector indicates the brightest output of the projector relative to the darkest output of the projector. The contrast ratio is a quantifiable measure of contrast and is defined as the ratio of the luminance of the brightest output of the projector to the luminance of the darkest output of the projector. This definition of the contrast ratio is also referred to as the "static" or "native" contrast ratio.

[0004] Some projection systems implement spatial amplitude modulation based on an SLM. In such systems, the light source can provide a light field that embodies the brightest level that can be reproduced on an image, but in order to generate the desired scene level, the light is attenuated or discarded. In some high-contrast examples of projection systems based on this architecture, contrast is improved by using a semi-collimated illumination system and a small aperture stop in the projection optics. In such an architecture, the illumination angle in the SLM has a significant impact on the projected image. Such an impact includes, but is not limited to, the impact on the contrast ratio and sharpness of the projected image.

Summary of the Invention

[0005] Various aspects of this disclosure relate to apparatus, systems, and methods for projection displays with high-contrast projection architectures.

[0006] In one exemplary embodiment of the present disclosure, a projection system is disclosed. The projection system comprises a light source configured to emit light in response to image data; an illumination optical system configured to direct the light, the illumination optical system including an integrated rod and a fold mirror; a digital micromirror device including a plurality of micromirrors, each micromirror configured to reflect the directed light as on-state light to a predetermined position when the micromirror is in the on position, and to reflect the directed light as off-state light to an optical dump when the micromirror is in the off position; and a controller. The controller determines the difference between the actual attitude angle of each of the plurality of micromirrors of the digital micromirror device and the target attitude angle of that micromirror of the digital micromirror device, and rotates the fold mirror based on the difference between the actual attitude angle and the target attitude angle of each of the plurality of micromirrors of the digital micromirror device. The system is configured to calculate a first amount and a second amount of lateral adjustment corresponding to the integration rod, rotate the folding mirror by an angle corresponding to the first amount, and actuate the integration rod in the first direction according to the second amount. The second amount is based on the first amount and is set to change the angle of incidence of the directed light on each micromirror in response to the misalignment, and to maintain the position of the directed light on each micromirror.

[0007] In another exemplary embodiment of the present disclosure, a method is provided for calibrating a projection system comprising: a light source configured to emit light in response to image data; an illumination optical system configured to direct the light, the illumination optical system comprising an integrated rod and a folding mirror; and a digital micromirror device comprising a plurality of micromirrors, each micromirror configured to reflect the directed light as on-state light to a predetermined position when the micromirror is in the on position, and to reflect the directed light as off-state light to an optical dump when the micromirror is in the off position. The method includes determining the deviation between the actual attitude angle of each of the plurality of micromirrors of the digital micromirror device and the target attitude angle of that micromirror of the plurality of micromirrors of the digital micromirror device; calculating a first amount of rotational adjustment corresponding to the folding mirror and a second amount of lateral adjustment corresponding to the integrating rod based on the deviation between the actual attitude angle and the target attitude angle of each of the plurality of micromirrors of the digital micromirror device; rotating the folding mirror by an angle corresponding to the first amount; and acting the integrating rod in a first direction according to the second amount. The second amount is based on the first amount and is configured to change the incident angle of the directed light on each micromirror in response to the deviation and to maintain the position of the directed light on each micromirror.

[0008] In another exemplary embodiment of the present disclosure, a non-temporary computer-readable medium for storing instructions is provided. The instructions are executed by a processor of a projection system which includes a light source configured to emit light in response to image data, an illumination optical system configured to direct the light, the illumination optical system including an integrated rod and a folding mirror, and a digital micromirror device including a plurality of micromirrors, each micromirror configured to reflect the directed light as on-state light to a predetermined position when the micromirror is in the on position, and the directed light as off-state light to an optical dump when the micromirror is in the off position. The process involves determining the deviation between the actual attitude angle of each of the plurality of micromirrors and the expected attitude angle of the micromirror in the digital micromirror device; calculating a first amount of rotational adjustment corresponding to the folding mirror and a second amount of lateral adjustment corresponding to the integrating rod based on the deviation between the actual attitude angle of each of the plurality of micromirrors and the target attitude angle of the digital micromirror device; rotating the folding mirror by an angle corresponding to the first amount; and acting the integrating rod in a first direction according to the second amount. The second amount is based on the first amount and is set to change the incident angle of the directed light on each micromirror in response to the deviation and to maintain the position of the directed light on each micromirror.

[0009] In this way, various aspects of the present disclosure provide display of images having a high dynamic range and high resolution, and utilize at least the technology of image projection, holography, signal processing, etc. To bring about improvements in the field. [Brief explanation of the drawing]

[0010] These and other more detailed and specific features of various embodiments are fully described in the following description with reference to the attached drawings. [Figure 1] Figure 1 shows a block diagram of an exemplary projection system relating to various aspects of this disclosure. [Figure 2A] Figure 2A shows a plan view of an exemplary spatial light modulator used in various embodiments of this disclosure. [Figure 2B] Figure 2B shows a cross-sectional view taken along line 2B in Figure 2A. [Figure 3A] Figure 3A shows an exemplary optical state in an exemplary projection system relating to various aspects of this disclosure. [Figure 3B] Figure 3B shows an exemplary optical state in an exemplary projection system relating to various aspects of this disclosure. [Figure 3C] Figure 3C shows an exemplary optical state in an exemplary projection system relating to various aspects of this disclosure. [Figure 4] Figure 4 shows an example of the adjustment method for the optical systems illustrated in Figures 3A to 3C. [Figure 5] Figure 5 shows an exemplary calibration system relating to various aspects of this disclosure. [Figure 6] Figure 6 shows an example of the calibration method for the calibration system shown in Figure 5. [Modes for carrying out the invention]

[0011] The disclosure and its embodiments can be implemented in various forms, including hardware, devices or circuits, computer program products, computer systems and networks, user interfaces and application programming interfaces, and hardware-implemented methods, signal processing circuits, memory arrays, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), etc. The above summary is intended solely to provide concepts of the various embodiments of the disclosure and does not limit the scope of the disclosure in any way.

[0012] The following description includes many details, such as the configuration, timing, and operation of optical devices, in order to provide an understanding of one or more aspects of the present disclosure. It will be readily apparent to those skilled in the art that these specific details are merely illustrative and are not intended to limit the scope of the application.

[0013] Furthermore, while this disclosure primarily focuses on examples of how various circuits are used in digital projection systems, it will be understood that this represents only one implementation example. Moreover, it will be understood that the systems and methods of this disclosure can be used in any device requiring the projection of light, such as cinema, home, and other commercial projection systems, head-up displays, virtual reality displays, and the like.

[0014] (Projector system) The optical system of an SLM-based projection system can be broadly classified into two parts: the optical system located on the illumination side (i.e., optically upstream of the SLM) and the optical system located on the projection side (i.e., optically downstream of the SLM). The SLM itself includes, for example, multiple modulation elements arranged in a two-dimensional array. Each modulation element receives light from the illumination optical system and transmits the light to the projection optical system. In some examples, the SLM can be implemented as a digital micromirror device (DMD). Further details on this will be discussed later. However, generally speaking, a DMD (Directional Mass Diode) includes a two-dimensional array of reflective elements (micromirrors or simply "mirrors"). Based on the position of each individual reflective element, the two-dimensional array of reflective elements selectively reflects light toward the projection optical system or discards light.

[0015] As described above, semi-collimated illumination systems and high-contrast projection systems using small aperture diaphragms in the projection optics can be significantly affected by differences in the angle of incidence (also called the "input angle") of light on the DMD. To prevent degradation of the projected image, the projection system may maintain the position and focus of the output of the illumination optics (e.g., light output from an integration rod or other uniformity correction device and subsequently reflected by one or more reflectors) on the DMD, while simultaneously maintaining the reflected beam at the center of the aperture diaphragm (e.g., filter aperture) of the projection optics. However, the precise position of the angle of the DMD mirror (e.g., the respective attitude angles in the "on" and / or "off" positions of the DMD mirror (further details below)) can be affected by manufacturing tolerances or other errors, so the actual angles may vary to some extent. To compensate for differences in DMD mirror angles between different actual DMDs and to ensure that the beam is properly centered, the angle of light exiting (e.g., reflected from the DMD) the DMD (also called the "exit angle") may be controlled. Such control should be robust to the first and second angular variations of the DMD mirror. Robustness to angular variations can be provided by implementing adjustments to the angle of incidence of the beam onto the DMD so that, when reflected by the DMD mirror, the exit beam is always at (or substantially at) the nominal design exit angle relative to the aperture. Furthermore, since each color channel in a color projection system may have different angular requirements, it is desirable to provide adjustments for each color.

[0016] Such high-contrast projection system architectures may impose certain constraints, in addition to the adjustment and maintenance of appropriate illumination angles. For example, the projection system may utilize a prism in which three colors are recombined, and / or a folding mirror in front of the prism, to reduce the size footprint of the optics and the projector itself. Furthermore, as described above, the image of the integrated rod should be positioned at the center of the DMD. This specification describes an example of a projection system in which the input angle of the beam to the DMD can be adjusted without changing the focus or position of the image of the integrated rod (or other uniformity correction device) in the DMD.

[0017] Figure 1 illustrates an exemplary high-contrast projection system 100 relating to various aspects of the present disclosure. In particular, Figure 1 illustrates a projection system 100 comprising a light source 101 configured to emit a first light 102; an illumination optical system 103 (an example of an illumination optical system according to the present disclosure) configured to receive the first light 102 and redirect or otherwise modify the first light 102 to produce a second light 104; a DMD 105 configured to receive the second light 104 and selectively redirect and / or modulate the second light 104 to produce a third light 106; a first projection optical system 107 configured to receive the third light 106 and project it as a fourth light 108; a filter 109 configured to filter the fourth light 108 to produce a fifth light 110; and a second projection optical system 111 configured to receive the fifth light 110 and project it onto a screen 113 as a sixth light 112.

[0018] In a practical implementation example, the projection system 100 may include fewer optical components, or may also include additional optical components such as mirrors, lenses, waveguides, optical fibers, beam splitters, diffusers, etc. Except for the screen 113, the components illustrated in FIG. 1 may be integrated within a housing in one implementation example to provide a projection device. In other implementation examples, the projection system 100 may include a plurality of housings. For example, the light source 101, the illumination optical system 103, and the DMD 105 may be installed within a first housing, and the first projection optical system 107, the filter 109, and the second projection optical system 111 may be installed within a second housing that can be coupled to the first housing. In some further implementation examples, one or more of the housings themselves may include sub-assemblies. One or more housings of such a projection device may also include additional components such as memory, input / output ports, communication circuits, power supplies, etc.

[0019] The light source 101 can be, for example, a laser light source, an LED, etc. Generally, the light source 101 is any light emitter that emits light. In some implementation examples, the light is coherent light. In some aspects of the present disclosure, the light source 101 may include a plurality of individual light emitters. Each light emitter corresponds to a different wavelength or wavelength band. The light source 101 emits light in response to an image signal provided by the controller 114. The controller 114 is, for example, one or more processors such as a central processing unit (CPU) of the projection system 100. The image signal includes image data corresponding to a plurality of frames to be continuously displayed. Individual elements in the projection system 100, such as the illumination optical system 103 and / or the DMD 105, can be controlled by the controller 114. The image signal may be provided from an external source in a streaming or cloud-based manner, or may be provided from an internal memory of the projection system 100 such as a hard disk, or may be provided from a removable medium operably connected to the projection system 100, or a combination thereof.

[0020] FIG. 1 illustrates a substantially straight optical path, but in reality, the optical path is generally more complex. For example, in the projection system 100, the second light 104 from the illumination optical system 103 is directed at an oblique angle towards the DMD chip 105 (or chip).

[0021] To illustrate the angle of incidence and the effect of the DMD mirror, FIGS. 2A-2B show an exemplary DMD 200 according to various aspects of the present disclosure. In particular, FIG. 2A illustrates a plan view of the DMD 200, and FIG. 2B illustrates a partial cross-sectional view of the DMD 200 taken along line II-B illustrated in FIG. 2A. The DMD 200 includes a plurality of square micro-mirrors 202 arranged in a two-dimensional rectangular array on a substrate 204. In some examples, the DMD 200 can be a digital light processor (DLP). Each micro-mirror 202 corresponds to one pixel of the final projected image and can be configured to tilt about a rotation axis 208 so as to be shown for a particular part of the micro-mirrors 202 among the micro-mirrors 202 by electrostatic or other types of actuation. The individual micro-mirrors 202 have a width 212 and are arranged at an interval of width 210 from each other. The micro-mirrors 202 can be formed of or coated with any highly reflective material such as aluminum or silver. Thereby, the micro-mirrors 202 specularly reflect light. The gap between the micro-mirrors 202 can be absorptive so that the input light incident on the gap is absorbed by the substrate 204.

[0022] Figure 2A shows only some representative micromirrors 202, but in reality, the DMD 200 may contain many more individual micromirrors equal to the resolution of the projection system 100. In some examples, the resolution may be 2K (2048×1080), 4K (4096×2160), 1080p (1920×1080), consumer 4K (3840×2160), etc. Furthermore, in some examples, the micromirrors 202 may be rectangular and arranged in a rectangular array, or hexagonal and arranged in a hexagonal array, etc. In addition, Figure 2A illustrates a rotation axis 208 extending diagonally, but in some implementations, the rotation axis 208 may extend vertically or horizontally.

[0023] As can be seen in Figure 2B, each micromirror 202 may be connected to the substrate 204 by a yoke 214. The yoke 214 is rotatably connected to the micromirror 202. The substrate 204 includes multiple electrodes 216. In the cross-sectional view of Figure 2B, only two electrodes 216 per micromirror 202 are visible, but each micromirror 202 may actually include additional electrodes. Although not specifically illustrated in Figure 2B, the DMD 200 is The substrate 204 may further include a pacer layer, a support layer, hinge components for controlling the height or orientation of the micromirrors 202, etc. The substrate 204 may also include electronic circuits related to the DMD 200, such as CMOS transistors and memory elements.

[0024] Depending on the specific operation and control of the electrode 216, individual micromirrors 202 can be switched between an "on" position, an "off" position, and a non-operated or neutral position. When a micromirror 202 is in the on position, it is actuated to an angle of (e.g.) -12° (i.e., rotated 12° counterclockwise relative to the neutral position) to specularly reflect the input light 206 to produce on-state light 218. When a micromirror 202 is in the off position, it is actuated to an angle of (e.g.) +12° (i.e., rotated 12° clockwise relative to the neutral position) to specularly reflect the input light 206 to produce off-state light 220. The off-state light 220 may be directed toward an optical damper that absorbs the off-state light 220. In some examples, the micromirrors 202 may be positioned parallel to the substrate 204 without being actuated. As illustrated in Figures 2A and 2B, the specific angles described herein are merely examples and not limiting. In some implementations, the on and off attitude angles may be ±11 to ±13 degrees (including ±11 and ±13 degrees), respectively.

[0025] In the scenario shown in Figure 1, where the DMD mirror uses a 12° angle tilt to reflect or discard light, the second light 104 is directed towards the DMD chip 105 at a fixed angle of 24°. When the individual mirror is tilted to a first predetermined angle (e.g., -12°), the mirror is considered to be in the ON state and redirects light toward the first projection optics 107, the filter 109, and the second projection optics 111 (e.g., in a predetermined position). When the individual mirror is tilted to a second predetermined angle (e.g., +12°), the mirror is considered to be in the OFF state and redirects light toward a light dump located outside the active image area.

[0026] To ensure that the image on the screen 113 has acceptable sharpness and contrast ratio, the illumination optical system 103 may be designed and / or controlled to ensure that the incident angle on the DMD 105 is accurate, while maintaining the position of the second light 104 at the center of the DMD 105.

[0027] (Integrated rod and folding mirror control system) In one exemplary implementation of the present disclosure, the above can be achieved using an integrated rod and a folded mirror. Figures 3A-3C illustrate the optical state of an exemplary partial optical system 300 according to the present disclosure. The partial optical system 300 may be at least partially an example of the illumination optical system 103 and the DMD 105.

[0028] In particular, Figure 3A illustrates the integration rod 301 or other uniformity correction device (only its output surface is illustrated), the first light 302, the first lens group 303, the second light 304, the folding mirror 305, the third light 306, the second lens group 307, the fourth light 308, and the DMD 309. For illustrative purposes, the partial optical system 300 in Figures 3A-3C is shown with the first light 302 oriented in a substantially vertical direction. Therefore, the integration rod 301 moves substantially horizontally (perpendicular to the first light 302). Thus, the integration rod 301 is configured to perform lateral adjustment. The integration rod 301 further has a range of motion defined by a first point and a second point. For example, the integration rod 301 may be configured to move up to -10 mm and +10 mm from a starting point (the position of the integration rod 301 illustrated in Figure 3). In some implementations, the integrating rod 301 has a sufficiently large lateral size (e.g., diameter, aperture) so that the first light 102 passes through the integrating rod 301 throughout its entire range of motion. For example, the lateral size of the integrating rod 301 may be more than twice the maximum value of its range of motion. The folding mirror 305 is configured to allow rotational adjustment. The folding mirror 305 has a range of motion defined by a third point and a fourth point. For example, the folding mirror 305 may be configured to move within the range of 15° to 75°, where 0° is defined as the case where the folding mirror 305 is vertical. In some implementations, the folding mirror 305 has a sufficiently large lateral size (e.g., diameter) so that the second light 304 is reflected off the surface of the folding mirror 305 throughout its entire range of motion. For example, the lateral size of the folding mirror 305 may be large enough so that light from the light source 101 (or the integrating rod 301) remains incident on the folding mirror 305 even when the folding mirror 305 is at the maximum value of its range of motion and the integrating rod 301 is at the maximum value of its range of motion.

[0029] The integrating rod 301 is optically upstream (and therefore further away from the DMD) compared to the folded mirror 305. Furthermore, the first lens group 303 is optically upstream compared to the second lens group 307. In some implementation examples, the folded mirror 305 may be located downstream (e.g., after) the second lens group 307. The various elements illustrated in Figures 3A to 3C may correspond to the various elements (or components of various elements) illustrated in Figure 1.

[0030] In some examples, the integrating rod 301 may be a component of the light source 101, receiving light from the light-emitting element of the light source 101 and outputting light, where the first light 302 corresponds to the first light 102. In other examples, the integrating rod 301 may be a component of the illumination optical system 103, which causes the integrating rod 301 to receive the first light 102 (e.g., light emitted by the light source 101). In such examples, the first light 302 is located inside the illumination optical system 103 and is therefore not explicitly shown in Figure 1. In some examples, the first lens group 303, the folding mirror 305, and the second lens group 307 are components of the illumination optical system 103, such that the fourth light 308 corresponds to the second light 104. In some implementation examples, optical elements upstream of the integrating rod 301 (e.g., some or all optical components of the light source 101 and / or illumination optical system 303) may be configured to move with the integrating rod 301. Such a configuration may be implemented to ensure uniformity and efficiency.

[0031] The first lens group 303 includes a first lens 310 and a second lens 311. The second lens group 307 includes a third lens 312 and a fourth lens 313. Although the first lens group 303 and the second lens group 307 are shown to include two lenses, they can consist of any number of lenses such that the first light 302 is directed towards the DMD 309 at a predetermined angle. Furthermore, although each individual lens is shown separately, the individual lenses of a group may be bonded to each other. In addition, each lens group can consist of any type of lens, such as concave lenses, convex lenses, biconcave lenses, biconvex lenses, plano-concave lenses, plano-convex lenses, negative meniscus lenses, and positive meniscus lenses.

[0032] DMD309 may correspond to DMD105. For simplicity of explanation, DMD309 is illustrated as a plane, but in reality, it includes multiple individual reflectors, which may or may not be oriented along the same plane. Thus, DMD309 may have the structure illustrated in Figures 2A-2B to selectively reflect and direct the fourth light 308 (i.e., the second light 104) depending on whether the individual reflectors of DMD309 are in the on, off, or neutral position. To provide an appropriate contrast ratio and image sharpness, the fourth light 308 (i.e., the third light 106), once reflected by DMD309, should be centered at a predetermined location such as an aperture (e.g., the first projection optical system 107, the filter 109, and the second projection optical system 111).

[0033] In the configuration illustrated in Figure 3A, the surface of the DMD 309 is oriented perpendicular to the fourth beam of light 308. The integrating rod 301 and the folding mirror 305 are positioned such that the fourth beam of light 308, which exits the second lens group 307, is centered on the DMD 309. Typically, the DMD should be illuminated at an angle twice the inclination angle of the micromirrors, but for the sake of simplicity in illustrating the principle of the invention, Figure 3A shows the fourth beam of light 308 contacting the DMD 309 at 0° with respect to a surface perpendicular to the DMD 309. The first beam of light 302 travels along the vertical optical axis from the integrating rod 301 to the first lens group 303. In practice, the first beam of light 302 subtends as it travels, forming a non-zero solid angle on the surface of the first lens group 303. The surface of the first lens group 303 receives the first light 302 and directs it as the second light 304 to the folding mirror 305. The surface of the folding mirror 305 reflects the second light 304 as the third light 306 to the second lens group 307 so that the fourth light 308 is positioned at the center of the DMD 309. When the micromirror 202 is "on", it is tilted to -12° and the fourth light 308 is projected through the projection lens. When the micromirror 202 is "off", it is tilted to +12° and the fourth light 308 is projected onto the light dump as described above.

[0034] However, in practice, any deviation in the nominal tilt angle of the micromirror of the DMD309 (or DMD105) will cause a shift in the incident point of the third light 106 on the first projection optical system 107. Also, if the fourth light 308 is tilted at any angle other than 0° with respect to the surface of the DMD309, the third light 106 may no longer be centered on the aperture diaphragm 109. These shifts can be canceled out by adjusting the integrating rod 301 and the folding mirror 305. For example, as illustrated in Figure 3B, the integrating rod 301 may be shifted in a first direction 314. The folding mirror 305 may be rotated in a second direction 315. The first direction 314 is perpendicular (e.g., lateral) to the optical axis of the integrating rod 301 (e.g., the direction of the first light 302). The second direction 315 is the angular direction indicating the rotation of the folding mirror 305. In Figure 3B, the second direction 311 is counterclockwise (or negative). The shift of the integrating rod 301 and the folding mirror 305 causes a shift in the light, ultimately changing the direction of the fourth light 108. However, the movement of the integrating rod 301 and the folding mirror 305 can maintain the incident point of the fourth light 108 at the center of the aperture. The incident point is positioned at the center, but the angle of the light changes based on the amount of movement of the integrating rod 301 and the folding mirror 305.

[0035] For example, to counteract the misalignment in the first example, the fourth light 308 illustrated in Figure 3B is tilted 2° relative to the misalignment-free example in Figure 3A, so as to maintain an incident point positioned at the center of the DMD 309. To achieve this, the integrating rod 301 is adjusted to a first amount (e.g., a first distance) in a first direction 310, and the fold rod 305 is adjusted to a second amount (e.g., a second distance) in a second direction 315.

[0036] To counteract the misalignment in the second example, the fourth light 308 illustrated in Figure 3C is tilted at -2° relative to the misalignment-free example in Figure 3A, thus maintaining the incident point positioned at the center of the DMD 309. To achieve this, the integrating rod 301 is adjusted by a first amount to a third direction 316, and the folding mirror 305 is adjusted by a second amount to a fourth direction 317. The third direction 316 may be the opposite direction to the first direction 314. Furthermore, the fourth direction 317 may be the opposite direction to the second direction 315 (e.g., clockwise or positive rotation).

[0037] The angles and angle adjustments illustrated in Figures 3A-3C are illustrative and not limiting. In practice, specific angles and angle adjustments are the tilt angle of the micromirror of the DMD309. It may depend on multiple factors, including, but not limited to, misalignments within the projection system and system or performance parameters selected by the system user.

[0038] (Integrated rod and folding mirror adjustment method) Figure 4 illustrates an exemplary adjustment or orientation method that may be performed during the calibration of the partial optical system 300 illustrated in Figures 3A-3C. The adjustment method in Figure 4 may be performed in an automated manner, for example, via a computer program, which will be described in further detail below.

[0039] In operation 401, the adjustment method determines the attitude angle of the DMD micromirror 202, or the deviation of said attitude angle from the expected angle. In addition to or alternatively, said attitude angle may be determined indirectly, for example, by illuminating the DMD 309 at a known angle and measuring the emission angle of the reflected light. In some implementations, operation 401 may be performed in a test fixture before the DMD 309 is mounted on the prism assembly.

[0040] In operation 402, the adjustment method calculates appropriate amounts of lateral adjustment for the integrating rod 301 and rotational adjustment for the folding mirror 305 based on the measured angle of the DMD micromirror 202. The appropriate amounts of lateral and rotational adjustment may be amounts that position the third light 106 at the center on the DMD 309 and at the center within the projection aperture 109. The calculation of operation 402 may be performed by using a computer program that takes a single input (the tilt angle of the DMD micromirror 202, or the tilt angle relative to the expected angle of the orientation of the DMD micromirror 202) and outputs the amounts of lateral adjustment for the integrating rod 301 and rotational adjustment for the folding mirror 305.

[0041] The calculation of operation 402 may be performed during calibration, or it may be performed in advance and stored in a lookup table associated with the projection system 100. In such an implementation, the calibration method may calculate the appropriate mirror angle adjustment by referring to the lookup table.

[0042] Following the calculations in operation 402, in operation 403, the adjustment method acts on the integrating rod 301 and the folding mirror 305 to implement the calculated adjustments. This actuation can be implemented using a stepper motor, a servo motor, or other suitable adjustment mechanism. For example, the integrating rod 301 may be coupled to a first track, and the folding mirror 305 may be coupled to a servo motor. The first track and the servo motor may be coupled (e.g., by mechanical coupling) such that the movement of the integrating rod 301 along the first track causes the corresponding movement of the folding mirror 305 by the servo motor. The integrating rod 301 may be actuated in a first direction 314 by acting on the first track so that the integrating rod 301 is in a first position, as calculated in operation 402. In another implementation example, the integrating rod 301 may be actuated in a third direction 316 by acting on the first track so that the integrating rod 301 is in a second position, as calculated in operation 402. The folding mirror 305 can be moved in a second direction 315 by operating a servo motor so that the folding mirror 305 is in a first position, as calculated in operation 402. In another implementation example, the folding mirror 305 can be moved in a fourth direction 317 by operating a servo motor so that the folding mirror 305 is in a second position, as calculated in operation 402. In some examples, the above operations are performed under the control of the controller 114 in Figure 1. In other examples, the above operations are performed under manual control.

[0043] (Integrated rod and folded mirror calibration system) Figure 5 illustrates an exemplary partial optical system 500 for calibrating the projection system 100. Some elements of system 500 correspond to elements in system 300 illustrated in Figures 3A-3C. Elements corresponding to each other are illustrated using the same reference numerals. System 500 includes an integrated rod 301, a first optical element 302, a first lens group 303, a second optical element 304, a folding mirror 305, a third optical element 306, a second lens group 307, a fourth optical element 308, and a DMD 309. In some implementation examples, the partial optical system 500 further includes a prism 318, such as a total internal reflection (TIR) ​​prism. Furthermore, system 500 includes a fifth ray 501, a sixth ray 502, a first projection lens 503, a beam splitter 504, a second projection lens 505, a first screen 506, a third projection lens 507, a second screen 508, and an aperture diaphragm 509. The first projection lens 503, the second projection lens 505, and the first screen 506 are the same as, or similar to, the first projection optical system 107, the second projection optical system 111, and the screen illustrated in Figure 1, respectively. The fifth ray 501, represented by long-chain-short-chain lines, is the peripheral ray of the system. The location where the rays of the fifth ray 501 converge indicates the location of the projected image of the DMD 309. The sixth ray 502, represented by half-double-chain lines, is the main ray of the system. The location where the rays of the sixth ray 502 converge indicates the aperture diaphragm 509, or the image of the aperture diaphragm 509.

[0044] The beam splitter 504 splits the fifth light 501 and the sixth light 502 such that the fifth light 501 ray converges onto the first screen 506 and the sixth light 502 ray converges onto the second screen 508. Thus, the image projected by the DMD 309 is reflected on the first screen 506. Specifically, the diffraction pattern projected by the DMD 309 can be used to calibrate the projection system 100. The image of the aperture diaphragm 509 is projected onto the second screen 508. The first screen 506 may be, for example, screen 113 in Figure 1. Each image can assist in the calibration of the projection system 100. For example, a technician of the projection system 100 may calibrate the projection system 100 while viewing both the diffraction pattern and the actual image of the aperture diaphragm 509 on the second screen 508. For calibration or testing purposes, an assembly including a beam splitter 504 and a second lens 505 may be configured to be inserted into the paths of the fifth light 501 and the second light 502. After calibration is complete, the assembly may be removed from the paths.

[0045] (Integrated rod and folded mirror calibration method) Figure 6 illustrates an exemplary calibration method that may be performed during the calibration of the partial optical system 500 illustrated in Figure 5. The calibration method in Figure 6 may be performed manually to set the initial positions of the integrating rod 301 and the folding mirror 305.

[0046] In operation 601, the integrating rod 301 and the folding mirror 305 are moved to the center of their respective ranges of motion. For example, the integrating rod 301 may be moved to the center of the first track or the center of its range of motion, as described above. The folding mirror 305 may be moved to the center of its range of motion, for example, 45°, as described above.

[0047] In operation 602, a projection aperture filter, such as filter 109 in Figure 1, is installed. Filter 109 may include an aperture configured to allow a predetermined order of diffraction or a predetermined irradiation angle of the fourth light 108 to pass through. For example, filter 109 may include a "Fourier section" or "Fourier lens assembly." The "Fourier section" or "Fourier lens assembly" refers to an optical system that spatially Fourier transforms the modulated light (e.g., light from DMD 105) by focusing it onto the Fourier plane. The spatial Fourier transform imposed by the Fourier section determines the propagation angle of each order of diffraction of the modulated light at the corresponding spatial position on the Fourier plane. This converts the signal to a specific value. This allows the Fourier section to select a desired diffraction order and abstract away unwanted diffraction orders through spatial filtering on the Fourier plane. For example, the Fourier section may be configured to allow projected light to pass through at an angle of 2°. The spatial Fourier transform of the modulated light on the Fourier plane corresponds to the Fraunhofer diffraction pattern of the modulated light.

[0048] In operation 603, the folding mirror 305 is adjusted until the center of the diffraction pattern from the DMD 309 is positioned at the center of the second screen 508. For example, the fifth light 501 may be a random noise pattern. The diffraction pattern (e.g., spatial frequency) observed when the fifth light 501 is projected onto the second screen 508 is an asinc² function. As the folding mirror 305 is rotated, the diffraction pattern of the fifth light 501 shifts. Once the diffraction pattern is centered, the folding mirror 305 is in its final calibration position. However, the image projected onto the first screen 506 may no longer be fully illuminated. In operation 604, the integrating rod 301 is adjusted until the image of the random noise pattern from the DMD 309 is fully illuminated on the first screen 506. Once the DMD 309 is fully illuminated, the integrating rod 301 is in its final calibration position. The final calibration positions of the integrating rod 301 and the folding mirror 305 are stored in the controller 114's memory (e.g., a lookup table) as the initial positions of the integrating rod 301 and the folding mirror 305.

[0049] The above projection system and calibration method may provide a configuration having an illumination optical system that can adjust and maintain the appropriate illumination angle, maintain the illumination position, and do all of this within an architecture using an integrated rod and a folded mirror.

[0050] The systems, methods, and apparatus relating to this disclosure may take one or more of the following configurations.

[0051] (1) A light source configured to emit light in response to image data; an illumination optical system configured to direct the light, the illumination optical system including an integrated rod and a folding mirror; a digital micromirror device including a plurality of micromirrors, each micromirror configured to reflect the directed light as on-state light to a predetermined position when the micromirror is in the on position, and to reflect the directed light as off-state light to an optical dump when the micromirror is in the off position; the actual attitude angle of each of the plurality of micromirrors of the digital micromirror device; and the micromirror of the plurality of micromirrors of the digital micromirror device A projection system comprising: a controller configured to determine the deviation between the actual attitude angle of each micromirror among the plurality of micromirrors of the digital micromirror device and the target attitude angle, calculate a first amount of rotational adjustment corresponding to the folding mirror and a second amount of lateral adjustment corresponding to the integrating rod based on the deviation between the actual attitude angle of each micromirror among the plurality of micromirrors of the digital micromirror device and the target attitude angle, rotate the folding mirror by an angle corresponding to the first amount, and actuate the integrating rod in a first direction according to the second amount, wherein the second amount is based on the first amount and is set to change the angle of incidence of the directed light on each micromirror in response to the deviation and maintain the position of the directed light on each micromirror.

[0052] (2) The projection system according to (1), further comprising a first lens group optically positioned between the integrated rod and the folding mirror, and a second lens group optically positioned downstream of the first lens group.

[0053] (3) The projection system according to (2), wherein the second lens group is optically positioned between the folding mirror and the digital micromirror device.

[0054] (4) The projection system according to (2), wherein the second lens group is optically positioned between the first lens group and the folding mirror.

[0055] (5) A projection system according to any one of (1) to (4), further comprising a filter between the digital micromirror device and the screen, the filter including an aperture configured to allow a predetermined order of diffraction of the reflected light to pass through.

[0056] (6) A projection system relating to any one of (1) to (5), wherein calculating the first amount and the second amount includes using a lookup table stored in the controller's memory to match the deviation to the first amount of rotational adjustment and the second amount of lateral adjustment.

[0057] (7) A projection system relating to any one of (1) to (6), wherein the lateral size of the integrated rod is at least twice the maximum value of the second quantity.

[0058] (8) A projection system according to any one of (1) to (7), further comprising a total internal reflection prism optically positioned between the folding mirror and the digital micromirror device.

[0059] (9) A projection system relating to any one of (1) to (8), wherein the first direction is substantially perpendicular to the optical axis of the integrated rod.

[0060] (10) A method for calibrating a projection system comprising: a light source configured to emit light in response to image data; an illumination optical system configured to direct the light, the illumination optical system comprising an integrated rod and a folding mirror; and a digital micromirror device comprising a plurality of micromirrors, each micromirror configured to reflect the directed light as on-state light to a predetermined position when the micromirror is in the on position, and to reflect the directed light as off-state light to an optical dump when the micromirror is in the off position, the method comprising the actual attitude angle of each micromirror among the plurality of micromirrors of the digital micromirror device and the digital micromirror device A method comprising: determining the deviation of one of the plurality of micromirrors between the target attitude angle and the actual attitude angle of that micromirror; calculating a first amount of rotational adjustment corresponding to the folding mirror and a second amount of lateral adjustment corresponding to the integrating rod based on the deviation between the actual attitude angle of each of the plurality of micromirrors of the digital micromirror device and the target attitude angle; rotating the folding mirror by an angle corresponding to the first amount; and acting the integrating rod in a first direction according to the second amount, wherein the second amount is based on the first amount and is set to change the angle of incidence of the directed light on each micromirror in response to the deviation and to maintain the position of the directed light on each micromirror.

[0061] (11) The method according to (10), wherein the projection system further comprises a first lens group optically positioned between the integrating rod and the folding mirror, and a second lens group optically positioned downstream of the first lens group.

[0062] (12) The method according to (11), wherein the second lens group is optically positioned between the folding mirror and the digital micromirror device.

[0063] (13) The method according to (11), wherein the second lens group is optically positioned between the first lens group and the folding mirror.

[0064] (14) The projection system further comprises a filter between a digital micromirror device and a screen, the filter including an aperture configured to allow a predetermined order of diffraction of the reflected light to pass through, according to any one of (10) to (13).

[0065] (15) A method relating to any one of (10) to (14), wherein calculating the first amount and the second amount involves using a lookup table stored in the controller's memory to match the deviation to the first amount of rotational adjustment and the second amount of lateral adjustment.

[0066] (16) The method relating to any one of (10) to (15), wherein the lateral size of the integrated rod is at least twice the maximum value of the second quantity.

[0067] (17) The projection system includes a total internal reflection prism optically positioned between the folding mirror and the digital micromirror device, according to any one of (10) to (16).

[0068] (18) The method relating to any one of (10) to (17), wherein the first direction is substantially perpendicular to the optical axis of the integrated rod.

[0069] (19) A non-temporary computer-readable medium storing instructions that cause the projection system to perform an operation including one of the methods described in (10) to (18) when executed by the projection system's processor.

[0070] With respect to the processes, systems, methods, heuristics, etc., described herein, the steps of such processes, etc., have been described as occurring in a certain sequence, but it should be understood that it is also possible to carry out such processes by performing the steps in an order other than that described herein. Furthermore, it should be understood that it is also possible to perform certain steps simultaneously, to add other steps, or to omit certain steps described herein. In other words, the descriptions of processes herein are provided for the purpose of illustrating certain embodiments and should not be construed in any way as limiting the scope of the claims.

[0071] Therefore, it should be understood that the above description is illustrative and not limiting. Reading the above description will reveal many embodiments and uses other than those given above. The scope should be determined not by reference to the above description, but by reference to the appended claims and the entire scope of equivalents to which those claims are entitled. It is anticipated and intended that the technology discussed herein will develop further and that the systems and methods disclosed herein will be incorporated into such future embodiments. In short, it should be understood that this application is modifiable and can be amended.

[0072] All terms used in the claims are intended to be given the broadest reasonable interpretation and the ordinary meaning as understood by a person familiar with the art described herein, unless expressly otherwise stated herein. In particular, the use of singular articles such as “a,” “the,” and “said” should be read as describing one or more of the elements indicated, unless the claim explicitly states a limitation to the contrary.

[0073] The Abstract of the Disclosure is provided to allow readers to grasp the essence of the technical disclosure in a short time. It is submitted with the understanding that it is not to be used to interpret or limit the claims or their meaning. Furthermore, in the Detailed Description above, it is found that various features are grouped together in various embodiments for the purpose of streamlining the disclosure. This method of disclosure should not be interpreted as reflecting an intention that the claimed embodiments possess more features than those explicitly described in each claim. Rather, as the following claims demonstrate, the subject matter of the invention lies in fewer features than all of the features of a single disclosed embodiment combined. Therefore, the following claims are incorporated into the Detailed Description as if each claim were existing independently as the subject matter of a single claimed embodiment.

Claims

1. A light source configured to emit light in response to image data, An illumination optical system configured to direct the aforementioned light, comprising an illumination optical system including an integrated rod and a folding mirror, A digital micromirror device comprising multiple micromirrors, each micromirror configured to reflect directed light toward a predetermined position as on-state light when the micromirror is in the on position, and to reflect directed light toward a light dump as off-state light when the micromirror is in the off position, wherein the multiple micromirrors have an actual tilt angle that has changed from the designed nominal tilt angle, A filter between the digital micromirror device and the screen, comprising an aperture configured to allow one or more predetermined diffraction orders of the reflected light to pass through, wherein the folding mirror is configured to rotate, and the integrating rod is configured to actuate laterally, thereby compensating for the difference between the nominal tilt angle and the actual tilt angle, so that the reflected ON-state light passes through the aperture even if there is a difference between the nominal tilt angle and the actual tilt angle, A projection system equipped with the following features.

2. A first lens group optically positioned between the integrated rod and the folding mirror, A second lens group optically positioned downstream of the first lens group, The projection system according to claim 1, further comprising:

3. The projection system according to claim 2, wherein the second lens group is optically positioned between the folding mirror and the digital micromirror device.

4. The projection system according to claim 2, wherein the second lens group is optically positioned between the first lens group and the folding mirror.

5. The projection system according to claim 1, further comprising a total internal reflection prism optically positioned between the folding mirror and the digital micromirror device.

6. A method for calibrating a projection system comprising: a light source configured to emit light in response to image data; an illumination optical system configured to direct the light, the illumination optical system including an integrated rod and a folding mirror; a digital micromirror device including a plurality of micromirrors, each micromirror configured to reflect the directed light as on-state light toward a predetermined position when the micromirror is in the on position, and to reflect the directed light as off-state light toward an optical dump when the micromirror is in the off position, the light being projected onto a first position on the digital micromirror device; and a filter between the digital micromirror device and a screen, including an aperture configured to allow a predetermined order of diffraction of the reflected light to pass through, the plurality of micromirrors having an actual tilt angle that has changed from a designed nominal tilt angle; Rotating the aforementioned folding mirror by a certain angle, The integrated rod is operated laterally, Includes, A method for compensating for the difference between the nominal tilt angle and the actual tilt angle, even if there is a difference between the nominal tilt angle and the actual tilt angle, such that the reflected ON-state light passes through the aperture, by the rotation of the folding mirror and the lateral movement of the integrating rod.

7. The method according to claim 6, wherein the projection system includes a first lens group optically positioned between the integrating rod and the folding mirror, and a second lens group optically positioned downstream of the first lens group.

8. The method according to claim 7, wherein the second lens group is optically positioned between the folding mirror and the digital micromirror device.

9. The method according to claim 8, wherein the second lens group is optically positioned between the first lens group and the folding mirror.

10. The method according to claim 6, wherein the projection system includes a total internal reflection prism optically positioned between the folding mirror and the digital micromirror device.

11. A non-temporary, computer-readable medium for storing instructions that, when executed by the processor of the projection system, cause the projection system to perform an operation including the method according to claim 6.

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