Patent Description:
This application claims priority to <CIT> and <CIT>.

The present invention relates to light recycling for projector systems and, particularly, to systems and methods for High Dynamic Range (HDR) projection systems.

Projector systems are now being architected with improvements in dynamic range. Dual and multi-modulator projector display systems are known in the art. However, additional improvements are possible in both the rendering and the performance of such display systems resulting from improved modeling of the light processing in such display systems. In addition, as appreciated by the inventors, it would be desirable to increase the brightness of image highlights for dual/multi-modulation systems and/or the energy performance for single modulation display systems - as well as for dual/multi-modulation display systems.

<CIT> ("D1") constitutes a prior right under Art. <NUM>(<NUM>) EPC. D1 describes projection systems and methods for efficient use of light by recycling a portion of the light energy. A projection display system is disclosed comprising a light source; an integrated rod that receives light from said light source at a proximal end that comprise a reflective surface which may reflecting/recycle light down said integrating rod; and a modulator comprising at least one moveable mirror that reflects light received from the integrating rod in either a projection direction or a light recycling direction. In other embodiments, dual and multiple modulator projector display systems are disclosed. A first modulator may affect either a pre-modulated halftone image or may affect a highlights modulated image for a desired image to be displayed. A second modulator may be provided for primary modulation of a desired image.

The present invention relates to a method according to claim <NUM> and a projector display system according to claim <NUM>. The dependent claims describe further embodiments.

Other features and advantages of the present system are presented below in the Detailed Description when read in connection with the drawings presented within this application.

Exemplary embodiments are illustrated in referenced figures of the drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive.

As utilized herein, terms "component," "system," "interface," and the like are intended to refer to a computer-related entity, either hardware, software (e.g., in execution), and/or firmware. For example, a component can be a process running on a processor, a processor, an object, an executable, a program, and/or a computer. By way of illustration, both an application running on a server and the server can be a component. One or more components can reside within a process and a component can be localized on one computer and/or distributed between two or more computers. A component may also be intended to refer to a communications-related entity, either hardware, software (e.g., in execution), and/or firmware and may further comprise sufficient wired or wireless hardware to affect communications.

Throughout the following description, specific details are set forth in order to provide a more thorough understanding to persons skilled in the art. However, well known elements may not have been shown or described in detail to avoid unnecessarily obscuring the disclosure. Accordingly, the description and drawings are to be regarded in an illustrative, rather than a restrictive, sense.

In the field of projector and other display systems, it is desirable to improve both image rendering performance and system efficiency. Several embodiments of the present application describe systems, method and techniques to affect these improvements by employing light field modeling for dual, or multi- modulation display systems. In one embodiment, light source models are developed and used to advantageous effect. Camera pictures of displayed images of known input images may be evaluated to improve light models. In some embodiments, an iterative process may accumulate improvements. In some embodiments, these techniques may be used on moving images to make live adjustments to improve image rendering performance.

Dual modulation projector and display systems have been described in commonly-owned patents and patent applications, including:.

In general, a projector with a single Digital Micromirror Device (DMD) may tend to have a limited contrast ratio. To obtain a greater contrast ratio, two or more DMDs and/or other reflectors (e.g., MicroElectroMechanical Systems (MEMS)) may be arranged in series. As a DMD may operate as a time-division or pulse-width modulator, operating two or more DMDs and/or reflectors in series -- both acting as pulse-width modulators - tends to require precise time-division alignment and pixel-to-pixel correspondence of time-division sequencing. Such alignment and correspondence requirements may be difficult in practice. Thus, in many embodiments of the present application, projector and/or display systems may employ different dual-modulation schemes to affect the desired performance.

For merely one example, one embodiment of a projector display system may use the first modulator (e.g., a first DMD/reflector) as a "pre-modulator" or "premod" - that may spatially modulate a light source by means of a halftone image that may be maintained for a desired period of time (e.g., a frame or a portion thereof). This halftone image may be blurred to create a spatially-reduced-bandwidth light field that may be applied to a second DMD/reflector. The second DMD/reflector -- referred to as the primary modulator -- may pulse-width modulate the blurred light field. This arrangement may tend to avoid both requirements mentioned above - e.g., the precise time-division alignment and/or the pixel-to-pixel correspondence. In some embodiments, the two or more DMDs/reflectors may be frame-aligned in time, and approximately spatially frame-aligned. In some embodiments, the blurred light field from the premod DMD/reflector may substantially overlap the primary DMD/reflector. In other embodiments, the spatial alignment may be known and accounted for - e.g., to aid in image rendering performance.

While the present application is presented in the context of a dual, multi-modulation projection system, it should be appreciated that the techniques and methods of the present application will find application in other dual, multi-modulation display systems. For example, a dual modulation display system comprising a backlight, a first modulator (e.g., LCD or the like), and a second modulator (e.g., LCD or the like) may employ suitable blurring optical components and image processing methods and techniques to affect the performance and efficiencies discussed herein in the context of the projection systems.

It should also be appreciated that - even though <FIG> depicts a two-stage or dual modulator display system - the methods and techniques of the present application may also find application in a display system with three or more modulator (multi-modulator) display systems.

<FIG> shows one possible embodiment of a dual/multi-modulator projector display system <NUM> that may suffice for the purposes of the present application. Projector system <NUM> employs a light source <NUM> that supplies the projector system with a desired illumination such that a final projected image will be sufficiently bright for the intended viewers of the projected image. Light source <NUM> may comprise any suitable light source possible - including, but not limited to: Xenon lamp, laser(s), coherent light source, partially coherent light sources. As the light source is a major draw of power and/or energy for the entire projector system, it may be desirable to advantageously use and/or re-use the light, so as to conserve the power and/or energy during the course of its operation.

Light <NUM> may illuminate a first modulator <NUM> that may, in turn, illuminate a second modulator <NUM>, via a set of optional optical components <NUM>. Light from second modulator <NUM> may be projected by a projection lens <NUM> (or other suitable optical components) to form a final projected image upon a screen <NUM>. First and second modulators may be controlled by a controller <NUM> - which may receive input image and/or video data. Controller <NUM> may perform certain image processing algorithms, gamut mapping algorithms or other such suitable processing upon the input image/video data and output control/data signals to first and second modulators in order to achieve a desired final projected image <NUM>. In addition, in some projector systems, it may be possible, depending on the light source, to modulate light source <NUM> (control line not shown) in order to achieve additional control of the image quality of the final projected image.

Light recycling module <NUM> is depicted in <FIG> as a dotted box that may be placed in the light path from the light source <NUM> to the first modulator <NUM>, as will be discussed below. While the present discussion will be given in the context of this positioning, it will be appreciated that light recycling may be inserted into the projector system at various points in the projector system. For example, light recycling may be placed between the first and second modulators. In addition, light recycling may be placed at more than one point in the optical path of the display system. While such embodiments may be more expensive due to an increase in the number of components, that increase may be balanced off against the energy cost savings as a result of multiple points of light recycling.

<FIG> depicts one embodiment of a projector display system 100b that comprises a single modulator 106b. Light source 102b emits (possibly under controller control - not shown) a light beam 104b may be transmitted through a light recycling module 103b, as before. Modulator 106b may selectively reflect the light, as desired by controller - and modulated light 108b may be transmitted through projector optics 112b and projected onto screen <NUM> as a finally desired image to be viewed.

<FIG> depicts one embodiment of a light recycling module that may perform light recycling on a plurality of color laser channels (e.g., R, G, and B). As may be seen in this example, the display system may comprise a red light source (R) that enters into an integrating rod <NUM> (e.g., <NUM> for B and <NUM> for G) that may be transmitted (possibly via total internal reflectance) to a controllable reflector <NUM> that may comprise one or more reflectors that may exhibit a recycle position 120b or a transmit position 120a. If light is to be recycled, reflector 120b would reflect the laser light back into the integrating rod <NUM> - which may reflect within that path multiple times - until the reflector is commanded (via controller, not shown) to transmit position 120a. Light transmitted by reflector 120a may be directed to a red mirror <NUM> as shown. In the case of blue light, blue light may be combined with red light at dichroic combiner <NUM>. Similarly, green light may be thereafter combined as dichroic combiner <NUM> and the light may then be further modulated and/or projected - as simply depicted by optical element <NUM>. It will be appreciated that this light recycling module may suffice for the purposes of a single modulator, dual modulator and/or multiple modulator display systems as desired.

<FIG> depicts one embodiment of a light recycling subsystem and/or module, as may be suitable for the purposes of the present application. As discussed above, this light recycling subsystem/module may be placed in the projector system primarily between the light source <NUM> and a first modulator <NUM>. Light from light source <NUM> may be input to the optical path via an integrating rod/tube/box <NUM> (e.g., via a port 201b, as seen in <FIG>). Integrating rod/tube/ box <NUM> may comprise a substantially reflected surface in its interior, so that light that is incident on its surface may be reflected (e.g., possibly multiple times) until the light is exits its extreme right end <NUM>. Once the light exits the integrating rod/tube/box, the light may be placed into an optical path that is defined by a set of optical elements - e.g., lens <NUM>, <NUM> and <NUM> and a set of filters and/or polarizers <NUM>, <NUM> and <NUM>.

First modulator <NUM> may comprise a number of prisms 218a, 218b and a reflector <NUM>. Reflector <NUM> may comprise a DMD array of reflectors, or a MEMS array - or any other suitable set of reflectors possible that may reflect light in at least two or more paths. One such path is depicted in <FIG>. As may be seen, reflectors <NUM> direct the light onto the interface of prisms 218a and 218b, such that the light is thereby reflected into lens assembly <NUM> and thereafter to second modulator <NUM> (e.g., comprising lens assembly <NUM>, prisms <NUM> and <NUM> and reflector <NUM>). This light may be employed to form the finally projected image to be viewed by an audience.

However, at certain time during the rendering of the final projected image, the full power/energy of the light source <NUM> may not be needed. If it is not possible to modulate the power of light source <NUM> (or if it is difficult or if there is additional opportunity to conserve light), then it may be desired to recycle the light from light source <NUM>. In this case, and as may be seen in <FIG>, it may be possible to align reflector <NUM> from its current position as shown (i.e., where the light is directed to travel the path down to the second modulator - to position instead where the light would be substantially reflected back to the integrating rod/tube/box <NUM>, along substantially the same path as described as traveling from right-to-left direction. In one embodiment, a recycling system may be able to make parts of the image brighter. This may be desirable in circumstances where large parts of the screen are dark and some parts are very bright.

In another embodiment, a third (optional) path (not shown) allows the reflectors to direct light from the light source to a light "dump" - i.e., a portion of the projector system where the light is absorbed. In this case, the light is wasted as heat to be dissipated from the projector system. Thus, the projector system may have multiple degrees of freedom when it comes to directing the light as desired.

<FIG> shows one embodiment of the proximal end <NUM> (i.e., the end closest to the light source) that aids in affecting light recycling. As may be seen, light may travel through integrating rod/tube/box <NUM> (e.g., via multiple reflections) back to the proximal end <NUM>. Proximal end <NUM> may further comprise a back portion 201a - which may further comprise a reflecting surface - and a port opening 201b where light from light source <NUM> may be input into the projector system. Light impacting the back portion 201a may be reflected back down the integrating rod <NUM> (possibly multiple times until the reflector(s) at the first modulator are directed to transmit the light down to a second modulator or some other suitable optical path to form the final image). The examples of <FIG> and <FIG> may be considered one example of a light recycling module that (like other examples given herein) are capable of recycling light at some point in the light pathway through the display system.

<FIG> is yet another embodiment of a light recycling module <NUM> - which may serve a module for at least one laser and/or partially coherent colored light source <NUM>, <NUM>, <NUM>. Light from such a source may transmit through a first optical subsystem <NUM> to condition the light to be input into integrating rod <NUM> - which may comprise the reflecting proximal end <NUM>, such as in <FIG>. A second optical subsystem <NUM> may further condition the light as desired prior to input into a first modulator <NUM>. As with <FIG> and <FIG> above, this first leg of the module <NUM> may affect a light recycling mode, as discussed.

After first modulation, light may be transmitted through a third optical subsystem <NUM> prior to input into a second modulator <NUM> - which modulates the light for transmission through a projector optical subsystem <NUM> to project a final image for viewing.

In one embodiment, an optional highlights modulator may affect adjustable illumination with a fraction of the available light, unless it is combined with the pre-modulator. To accomplish this, both mechanical and/or non-mechanical subsystems and techniques of beam steering may be employed - e.g., steering portions of the illumination source to the various paths in the system using mechanical steering, holograms with spatial light modulators or other spatial modulation methods may be possible. It may be desired with such a system to increase efficiency by steering light to where it is desired.

Mechanical beam steering may use a collection of reflective elements which can be controlled over a range of motion in the horizontal and/or vertical direction. These reflective elements direct the light reaching them to the desired areas of the modulators following the highlight modulator creating controlled non-uniform illumination.

Non-mechanical beam steering methods may use a spatial light modulator to shift the phase of uniform coherent light reaching the modulator. The phase shifted light creates a three dimensional light field when imaged through a lens. The three dimensional light field can be imaged into a two dimensional light field with different planes from the collapsed dimension imaging with varying sharpness or PSF properties onto one of the following modulators creating a two dimensional light field.

Without regard to the manner of implementation, highlights modulation refers to using a modulator to steer light reaching it to anywhere on the subsequent modulators. While there can be restrictions, such as positional range and granularity, the term "anywhere" may still be used to distinguish highlight modulators from other modulators.

Depending on the number of highlight modulation elements, PSF properties and total coverage achievable by the highlights modulator, it may not be necessary in some embodiments to have a pre-mod/first modulator between it and the primary/second modulator. In some embodiments, it may be possible that the highlight modulator may be of such performance as to not require any modulation (pre or primary) after it.

In some embodiments, it may be possible to adjust the relay optics to control the Point Spread Function shapes of illumination on to the pre-mod/first modulator or primary/second modulator generated by a highlights modulator. In some embodiments, there may be controls to adjust the Full Width Half Max dimension as well as to control the shape or tails of the PSFs. It may be desirable to predict, monitor and/or measure the resulting performance when light recycling is employed as additional passes through the integrating rod will change the uniformity and angular diversity of the light which will in turn affect the resulting PSFs.

In some embodiments, Pre-mod/first modulation may entail the ability to modulate the light arriving at the pre-modulator on the way to the primary modulator. In some cases, pre-modulation may be employed to increase the system contrast. With highlighting, it is possible that the highlight image may illuminate the pre-modulator in addition to the non-imaged pre-modulator illumination.

In some embodiments, a suitable pre-mod/first modulator may be a DMD, an LCD, LCoS (Liquid Crystal On Silicon) or other intensity modulator. Regardless of the implementation, pre-modulation may be used to modulate the light intensity reaching it on to the following modulators. The pre modulator elements (e.g., mirrors, pixels, etc.) each influence a fixed location on the following modulators, or screen if no additional modulation follows the pre modulator. Depending on the number of pre modulation elements, PSF properties and total coverage achievable by a pre-modulator, it may not be necessary to have a primary modulator follow it. It is possible that the pre modulator could be of such performance as to not require any modulation (e.g., highlight or primary) before or after it.

This refers to the ability to adjust the relay optics to control the Point Spread Function shapes of illumination on to the Primary modulator generated by the Highlights or Pre modulator. There are controls to adjust the Full Width Half Max dimension as well as to control the shape or tails of the PSFs. It is possible to use recycling with the pre-modulator, and it may be desirable monitor, model, predict and/or measure the resulting illumination intensity as additional passes through the integrating rod will change the uniformity and angular diversity of the light which will in turn affect the resulting PSFs.

Primary/second modulation may entail the ability to modulate the light arriving at the primary modulator on the way to the screen. In some embodiments, this may tend to ensure a resulting quality image with high contrast, and desired spatial and intensity resolution. In some embodiments, it may be possible that the highlight and/or pre modulator images may illuminate the primary modulator, in addition to the non-imaged primary modulator illumination.

In some embodiments, a suitable primary/second modulator may be a DMD, an LCD, LCoS or other intensity modulator. Regardless of the manner of implementation, primary/second modulation may serve to modulate the light intensity reaching it on to the screen. The primary modulator elements (e.g., mirrors, pixels, etc.) each influence a fixed location on the screen. The size and shape of each location should be consistent to form the projected screen image whose overall size and shape will be determined by the Projection Optics. Depending on the primary modulator contrast range, it might not be necessary to use a highlight or pre-modulator. It is possible that the primary modulator may be of such performance as to not require any modulation (highlight or pre) before it. It may be possible to use recycling with the primary modulator. It would be desirable to understand the resulting illumination intensity both in level and over time in order to compensate with illumination adjustment or by changing the signal to the modulator to ensure the desired image is formed. It is possible to measure this level. It is also possible to model and predict this level algorithmically.

<FIG> depicts another embodiment of a dual/multi-modulator projector system <NUM> where it may be possible and/or desirable to perform light recycling. As may be seen, projector system <NUM> may comprise one or more light sources (e.g., 402a and/or 402b, or other additional light sources). In this embodiment, the light source 402a provides light into an integrated subsystem/box 404a that may resemble the embodiment of FIG. Light from 402a may eventually make it to first modulator <NUM> - where first modulator <NUM> may be constructed in substantially the same way as <FIG>, <FIG> and/or <NUM> (i.e., with reflectors that may reflect the light back into integrating subsystem/box 404a. The light may then proceed to optical subsystem <NUM>, second modulator <NUM> and thereafter to projector lens <NUM> and a final projected image may be formed on screen <NUM>.

However, another opportunity for light recycling may occur with another one (or more, in other embodiments) light source 402b. In one embodiment, light source 402b may be employed as another primary light source (i.e. to provide a significant amount of light for final images a substantial amount of the time). In this embodiment, light from 402b may be further reflected by reflector <NUM> such that this light may be combined with the light from 402a at beam splitter <NUM> - and the combined beam forms the final image a substantial amount of the time.

In another embodiment, light source 402b may be used a lesser amount of the time in order to provide highlight illumination within part of the image. It should be appreciated that reflector <NUM> may be a single mirror that is possible moveable (e.g. to take light to a dump or another recycling subsystem). Alternatively, reflector <NUM> may be a set and/or an array of reflectors (e.g., MEMS, DMD or the like) to provide a finer control of the additional light from 402b.

In yet another embodiment, light source 402b may be optional and integrating subsystem/box 404b may have a fully reflective surface at the end proximal to where light source 402b might be. In this embodiment, light may have another path (e.g. inside box 404b, as well as box 404a) in which to recycle light. In another embodiment, it might be possible to use a one way mirror for <NUM>. In this case, reflector <NUM> would just be a controllable mirror that may redirect the light into 404b and, thus, reflector <NUM> may only be necessary to "fold" the system for recycling. In such an embodiment, there may be no need to have light recycled in 404a but instead light may be recycled in 404b. This may be desirable as the recycling reflector which may not have hole in it for the light input making it a much more efficient recycler.

<FIG> is yet another embodiment for which light recycling may be possible and/or desirable. Projector system <NUM> may comprise a light source <NUM> and integrating subsystem/box <NUM> as previously described. Polarizer <NUM> may be a controllable polarizer such as an LCD which will polarize a selectable portion of the light in one orientation. Beam splitter <NUM> may be a polarizing beam splitter which will let the light in one orientation pass straight through as uniform light field <NUM> to get combined using <NUM> onto primary modulator <NUM>. The light polarized in the other orientation gets redirected by <NUM> as <NUM>. Mirror <NUM> may be a mirror to fold the system and get light to either a pre-modulator or a highlights modulator <NUM>, depending on the design of the system.

The non-uniform light field from <NUM> then gets combined with <NUM> using <NUM> to illuminate <NUM>. When <NUM> is a pre modulator, beam <NUM> may be used to provide some base level of illumination less than the first step of <NUM> out of dark for very dark portions of the image <NUM>. Alternatively, when <NUM> is a highlight modulator, <NUM> is used to provide the uniform light level required by image <NUM> in regions where no light will be in the non-uniform light field created by <NUM>.

In other embodiments, it may be possible to place a recycling-type integrating rod (similar to those described in <FIG>) in between <NUM> and <NUM> (or in between <NUM> and <NUM>) and a non-recycling version of an integrating rod (e.g., without a back reflector) in between <NUM> and <NUM>. In such an embodiment, it may be desired to remove <NUM> after <NUM> in order to keep the light as a tight beam.

<FIG> depict schematically one or more possible embodiments for projector systems that may afford these multiple opportunities for light recycling. <FIG> depicts schematically the processing <NUM> that may be possible with a dual/multi-modulator projector system. This processing may include light from a variety of laser, coherent or partially coherent light sources - e.g., where laser light may be pulsed (<NUM>) or supplied by laser diodes <NUM>. Such light may be combined and transported (<NUM>) in a variety of architectures and manners (as described in connection with several of the embodiments above). Light may then be split (<NUM>) into component parts (e.g., <NUM> through <NUM>) and this light may be combined and split (<NUM>) to serve various functions, such as highlight illumination (<NUM>), dump illumination (<NUM>), pre-mod (or first modulator) illumination (<NUM>) and primary (or second modulator) illumination (<NUM>).

In one embodiment, adjusting the laser power tends to affect the entire display area uniformly for global dimming. This may be appropriate for some images and scenes in projector systems where it is possible to adjust the laser and/or light source power. However, in some circumstances, it may be advantageous at low luminance levels to have a controllable base level uniform illumination applied directly to the highlights, pre-mod/first modulator or primary/second modulators. Controlling this type of laser power adjustment will be considered another form of global dimming.

In one embodiment employing multiple laser sources (either an individual laser or group of lasers for each controllable source, or by splitting lasers or groups of lasers into each controllable source) in the display system, it may be possible to spatially arrange them such that each one affects a portion of the display area allowing for local dimming. This method is different from the highlights modulator in that these local dimming zones are fixed spatially, where the highlights modulation local dimming zones can be spatially adjustable. It is possible to use mechanical light steering to control the laser power adjustment to each zone by directing the light reaching the mirror to a spatially oriented fiber or optical component such as a segmented integrating rod which will direct the light to a predetermined spatial zone on the modulator.

In such a case, the mechanical light steering device may be considered part of the laser power adjustment and not a highlights and/or pre modulator, however these systems where the number of individually controllable elements on the mechanical steering is greater than the number of spatial zones have the additional advantage of being able to spatially redistribute the illumination from a fixed or variable source rather than having to directly vary the source of each zone. The spatial application of the laser illumination to the modulators may be controlled by the illumination optics for each modulator. For global dimming, illumination by the illumination optics (e.g., lenses, integrating rods, etc.) may be designed to uniformly illuminate the modulator. For local dimming, illumination by the illumination optics (e.g., lenslet arrays, segmented integrating rods, etc.) may be designed to take each light path and spread it across a desired portion of the modulator to create the appropriate PSF.

In an embodiment where the pre-mod/first modulator is anticipated to receive the majority of the illumination, if light recycling is implemented, then it may be desirable to have its illumination adjustable either in splitting or with laser power control, or by using the modulators to compensate which may reduce contrast.

<FIG> depicts several embodiments schematically of projector systems that may affect such processing as noted in <FIG>. System <NUM> may optionally provide for highlight illumination <NUM> to enter into an optical path <NUM> to a highlight modulator <NUM>. This light may be either sent into the pre-mod (or first modulator) light path at <NUM> via optical path <NUM> - or the light may be dumped (<NUM>) and possibly recycled at <NUM>.

The pre-mod/first modulator stage may input light at <NUM> via optical path <NUM>. This light may be combined with highlight illumination at the pre-mod/first modulator <NUM>, as described. This light may be either sent to the primary/second modulator (e.g., forming a pre-mod image <NUM>) -- or it may be dumped and recycled at <NUM>.

The primary/second modulator (<NUM>) may receive light from the pre-mod/first modulator or primary illumination <NUM> (e.g. via optical paths <NUM>, <NUM> respectively). This light may be sent as a primary image <NUM> to projection optics <NUM>, forming projected image <NUM> onto a projection screen (possibly with vibration, if the light source is coherent or partially coherent) <NUM> and viewed in an auditorium <NUM> or the like. Otherwise, the light may be dumped and recycled at <NUM>.

It will be appreciated that this schematic diagram may support a variety of possible projector systems and that all of them are encompassed in the scope of this present application. It may suffice that a projector system architecture may support one or more opportunities for light recycling for the purposes of the present application.

As mentioned, in many times during the projection of an image, a set of images or video, it may not be desired to use the full power of the light source to form the final projected image. In this case, a portion of the light may be recycled many times (substantially indefinitely) until it is needed to form a more luminant image. In addition, as reflector <NUM> may actually comprise a set (or array) of reflectors, the opportunity to recycle light may be possible on a local dimming basis. In one possible embodiment, it may be possible to employ light recycling - on either a global or local dimming basis - when not all the available light is needed to form the final projected image - and then use it on a targeted basis, e.g., to project a "highlight" in the final projected image. A highlight may be a portion of the image for which it is desired to direct a good deal more luminant energy than its surrounding part of the image in order to accentuate that portion.

In another embodiment, it may be possible to employ light recycling - again on either a global or local dimming basis - in order to boost luminance of an image or scene that is, on average, a brighter image or scene than the one preceding it. These opportunities may arise during illumination of the pre-mod/first modulator stage, or primary/second modulator stage - as may be seen in <FIG>.

In one embodiment, the projector system may make a determination as to how best to employ light recycling through the controller as it processes input image/video data. The decision to recycle may be made either on-the-fly as the image data is processed - or in advance, in a look-ahead fashion by a frame, set of frames or scene-by-scene basis. In another embodiment, whole video and/or scenes may be analyzed off-line and the control signals may be sent to the controller as part of an associated metadata stream, together with the image/video data.

<FIG> is one embodiment of a flowchart for performing light recycling. Control system/method <NUM> may input image data at <NUM>. Based on the response curve and/or table (e.g., as shown in <FIG>), the system/method may calculate the Average Picture Level (APL) for each Individually Modulated Color (IMC) of the modulator. As may be seen in the graph of <FIG>, each individual color may exhibit a different relative brightness for a given DMD fill percentage. It may be desirable to take into consideration these color difference when performing light recycling - so as to eliminate and/or mitigate any tonal visual artifacts. It should be appreciated that the flowcharts of <FIG> may assume the recycling generates a uniform field of light - whereas the flowchart of <FIG> may account for spatial intensity variation due to the recycling and employ the tables in <FIG>. For example, according to the Table depicted in <FIG>, an input image may be divided into a <NUM> x <NUM> array of image regions, and light recycling in each of the image regions may be adjusted as noted, from <NUM>% to <NUM>%.

Returning to <FIG>, at <NUM>, the system/method may determine the relative brightness increase for each IMC. Once accomplished, system/method may instruct the display system to reduce the illumination source intensity to the reciprocal of the brightness increase for each IMC. It should be appreciated that other functional relationships may be possible and/or desirable between illumination source intensity and brightness increase - e.g., possibly some inverse relationship of some function of brightness increase. Where the term "reciprocal" is used herein, it will be appreciated that such other embodiments are also possible. It is possible to adjust the light source intensity in <NUM>, but in some embodiments, the recycling may remain the same (e.g., the percentage of recycling may not be changed by the source reduction, just the absolute value - so as to not put too much illumination onto the modulator). Since light travels fast and even the fastest PWM cycle is comparatively very slow, the recycling may be considered instantaneous and the resulting illumination level may be achieved right after the modulator switches to its current state.

In the case where the system employs DMD(s) as primary modulators (e.g., modulators which spread out the modulation over several time segments), there may be a modulator state and resulting recycling level for each time segment and each one may be calculated and compensated. For systems that employ DMD(s) as pre-modulators, there may be just one time segment as the system may drive them with a half tone binary patternwhich may only change once per frame (e.g., in practice it may change it <NUM>-<NUM> times per frame, but this may be significantly less than the <NUM>'s-<NUM>'s of time segments for a primary DMD modulator). With embodiments employing LCD and LCoS as primary modulators, these may switch slowly (relative to DMD's) while displaying -- so the resulting recycling may be integrated over that time to determine how to compensate.

While the control system/method of <FIG> may work in general for any dual/multi-modulator display system, this control may work also in the context of a single modulator projector system (e.g., as might be constructed in the same or similar manner as <FIG>). Recycling on the primary modulator may come from the time sequential nature of the DMD, LCoS and LCD based systems.

<FIG> is yet another control system/method (<NUM>) for light recycling. Control may start inputting image data at <NUM>. At <NUM>, the system may calculate the APL for each IMC. The system may then determine the relative brightness increase for each IMC at <NUM>. At <NUM>, the system may reduce the illumination source intensity to the closest setting to the reciprocal of the brightness increase for each IMC, possibly without going below that reciprocal value. In one embodiment, it may be assumed that the system may reduce the light with the modulator but not increase it - in such a case, it may not be desired that the system may reduce the illumination source below the required level. However, in another embodiment (e.g., in the case of a mostly dark modulator image), the opposite may tend to be true (e.g., the system may reduce the illumination and then set the modulator to allow more light to pass). In such a case, step <NUM> may proceed to reduce illumination source intensity to the closest setting to the reciprocal of the brightness increase for each IMC and still allowing for modulator compensation.

The system at <NUM> may then decrease the intensity of the image driven to the modulator to compensate for the difference between the desired reciprocal of the brightness increase and the setting obtainable with the illumination source. Alternatively, step <NUM> may also adjust the intensity of the image driven to the modulator to compensate for the difference between the desired reciprocal of the brightness increase and the setting obtainable with the illumination source.

<FIG> is yet another embodiment of a control system/method for light recycling. However, this control system/method may work well in display systems where the light non-uniformity due to recycling may need to be considered and/or adjusted, and the illumination intensity control is fine grained or continuous. The system/method <NUM> may input image data at <NUM>. At <NUM>, the system may calculate APL for each region of an IMC (i.e., where the image may be divided into different regions). At <NUM>, the system may determine the relative brightness increase for each region in each IMC based on experimental statistics. The system may drive patterns (e.g., certain regions off while the rest are on) to the modulator and observe the distribution of light. Depending on the location of the dark region, its recycled light may return to the modulator in a non-uniform fashion. This non-uniformity needs to be compensated for on the modulator.

At <NUM>, the system may reduce illumination source intensity to the reciprocal of the region with the lowest brightness increase for each IMC. The system may determine the relative brightness increase for each region in each IMC, based on the illumination source intensity setting. Then, at <NUM>, the system may decrease the intensity of the image driven to each region of the modulator to compensate for the difference between the desired reciprocal of the brightness increase for that region and the setting of the illumination source.

Given an input image divided into a <NUM> x <NUM> array of image regions, <FIG> depicts a partially populated (e.g., the center and corner values are populated only by measurement, estimation and/or calculation - the remainder may be similarly filled) example Table for setting non-uniform levels of light recycling on the modulator given a certain modulator regional pattern (e.g., as derived as part of experimental statistics). In another aspect, it may be possible to show a pattern and then adjust the resulting recycling levels based on its characteristics. For example, Table <NUM>, shows the luminance characteristics of an image segmented into a <NUM> x <NUM> array of image regions (e.g., in each region, it shows whether the average or peak luminance level is above or below a predefined luminance threshold (e.g., <NUM> nits)). For example, since the bottom right region is OFF (or below the threshold), in an embodiment, as shown in Table <NUM>, most of the light recycling may be performed closer to that area and then drop off for image regions positioned further away. Many such tables, derived by experiment, may be used in <NUM>.

<FIG> is one embodiment of an algorithm (<NUM>) for reducing illumination source intensity according to brightness increases. Such brightness increases may occur on a individually modulated color basis in some systems.

At <NUM>, the system may input a desire image for viewing. At <NUM>, the system may calculated the light field desired (or otherwise required) to be generated by the pre-modulator for each of the individually modulated colors (IMC). At <NUM>, the system may calculate the average picture level (APL) for the pre-modulator of each IMC. The relative brightness increase may be determined at <NUM> for each of the IMCs on its APL. At <NUM>, the system may then reduce the illumination source intensity to the reciprocal of the brightness increase for each IMC.

<FIG> is one embodiment of an algorithm (<NUM>) for reducing illumination source intensity - especially in systems that may employ polarization to project images -e.g., as may be seen in <FIG>.

At <NUM>, the system may input a desired image for viewing. At <NUM>, the system may calculate the amount of light to be diverted directly to the primary modulator (e.g., such as <NUM> in <FIG>), possibly for each of the IMCs. At <NUM>, the system may then calculate the light field required to be generated by the pre-modulator of each IMC. The APL may then be calculated for the pre-modulator of each IMC at <NUM>. The system may then determine the relative brightness increase for each IMC based on its APL at <NUM>. At <NUM>, the system may reduce the illumination source intensity to the reciprocal of the brightness increase for each IMC. This may also include the amount of light to be diverted directly to the primary modulator for each IMC. At <NUM>, the system may then adjust the polarizer (e.g., <NUM>) to align the polarization into a beam splitter (e.g., <NUM> ) such that a desired amount of light may be diverted directly to the primary modulator.

<FIG> is one embodiment of an algorithm (<NUM>) that may input images that were generated without the assumption that the display system may engage in light recycling. In one embodiment, the system may adjust for light recycling in many possible ways - e.g., take a "EDR Master" grade and mapping it down to the capabilities of the targeted display while preserving artistic intent by way of metadata.

At <NUM>, the system may input a desired image for viewing. This image may have been created assuming that no recycling is/was to be accomplished. At <NUM>, the system may calculate the APL for each IMC. At <NUM>, the system may determine the relative brightness increase for each IMC based on its APL. The system may then provide (or otherwise calculate) the brightness range that may be achievable for each IMC to the display management algorithm at <NUM>. At <NUM>, the display management algorithm may generate an image to be displayed based on a recycling range which may be less bright than achievable for each IMC with recycling - but, possibly, not greater. At <NUM>, the system may then calculate a New APL (NAPL) for each IMC. At <NUM>, the system may determine the new relative brightness increase for each IMC based on its NAPL. Thereafter, the system may, at <NUM>, reduce the illumination source intensity to the reciprocal of the NAPL for each IMC.

In continued reference to <FIG>, there is shown a relay optical system <NUM> that is placed in between a first modulator <NUM> (e.g., a pre-modulator) and a second modulator <NUM> (e.g., a primary modulator). Such a relay optical system may be desirable to both reduce the amount of artifacts in the image processing - as well as increasing the contrast of the projected image.

As discussed herein in the context of one embodiment, it is desirable for the first modulator/pre-modulator to produce a blurred and de-focused image based upon image data values, such as the halftone image mentioned herein. It is desirable to have a relay optical system that tends to produce a uniformly blurred/de-focused image from the pre-modulator to the primary modulator. In addition, it is desirable to have a desired, defocused spot shape for this embodiment.

In many embodiments, the relay optical system may comprise lenses or other optical elements that effectively moves the focal plane, corrects for any coma, and adjusts the spread (e.g., by creating defocus/blur and adding spherical aberration to some desired amount).

For example, <FIG> depicts one possibly desirable spot shape <NUM> which is substantially Gaussian-shaped - where the x-axis is distance (in mm) and the y-axis is the relative amount illumination (e.g., where '<NUM>' is maximum illumination and '<NUM>' is dark). It should be noticed that, in a system that may provide for light recycling or other systems/methods of supplying highlight, the illumination may exceed "<NUM>" at some time or another.

In addition to the optical system <NUM> of <FIG>, <FIG> is yet another embodiment of a relay optical system <NUM> suitable for the purposes of the present application. On either end of relay optical system <NUM>, there are disposed two modulators - e.g., 1602a and 1602b (e.g., as shown here as an unfolded prism systems). First modulator 1602a may be a pre-modulator and second modulator 1602b may be a primary modulator, as mentioned further herein.

Light transmitted by first modulator 1602a may be further transmitted through a focus group of lenses <NUM>, a coma-correction group of lenses <NUM> and a field flattening/spherical aberration-inducing group of lenses <NUM> - prior to illuminating the second modulator 1602b. In many embodiments, the relay optical system may be substantially telecentric - e.g., wherein the chief rays (that is, oblique rays which pass through the center of the aperture stop) are substantially parallel to the optical axis in front of or behind the system, respectively.

<FIG> and <FIG> depict embodiments of the focus group l604 and the coma-correction group of lenses <NUM>, respectively. As may be seen in <FIG>, light from first modulator 1602a is transmitted to focus group <NUM>. Focus group <NUM> may further comprise a first lens 1604a - which may be a plano-convex lens. Lenses 1604b and 1604c may be two lenses comprising plano-convex lenses or lenses comprising a slight meniscus.

Each of these lenses may be designed to have a desired amount of spherical aberration that, in combination with defocus, can yield the proper light distribution (as shown in <FIG>) at the image plane, where the primary modulator is located. Multiple weak lenses, rather than fewer elements with higher power, will produce the desired amount of spherical aberration more easily. The distances between the lens elements can also contribute to achieving the desired amount of these aberrations.

As mentioned, the amount of blur and/or de-focusing may be set and/or controlled, depending on the distance between lens 1604a and lens 1604b. In one embodiment, a distance and/or air gap of approximately <NUM>-<NUM> may be suitable to provide sufficient de-focusing/blurring for illuminating the second modulator. Another embodiment of the focusing group <NUM> may affect the ability to change the focus, and thereby adjust the spot size at the primary modulator, by changing the air space between <NUM> of the elements. In this regard, the adjustable focus with the elements may also tend to create the desired spherical aberration.

In one embodiment, the projector system may set this distance one time at the time of manufacture and the lenses may be set on a permanent mount for the working lifetime of the projector system. In another embodiment, the distance may be dynamically varied during the course of operation. In such an embodiment, one or more of the lenses may be moveably mounted in the relay optical system wherein the distance may be adjusted as desired according to a controller providing control signals to the moveable mount.

<FIG> depicts that light from the focus group1604 is transmitted to a coma correcting group <NUM>. As in several embodiments of the present projection system, the fact that light is transmitted between two modulators that may comprise optical elements that are tilted with respect to one another (e.g., the two modulators comprising a plurality of prisms or the like), this may tend to induce a certain amount of coma and/or stigmatism into the transmitted light. Thus, in many embodiments, coma-correcting group <NUM> may be placed into the optical path to correct for this coma and/or stigmatism. One manner of correcting coma/stigmatism may be achieved by off-setting the optical axis 1607a in the first lens 1606a with respect to the optical axis 1607b in the second lens 1606b by a desired amount, as may be seen in <FIG>. In one embodiment, both lenses 1606a and 1606b may be slight meniscuses - e.g., where the surface proximal to the light path is slight concave and the surface distal to the light path is slight convex. It may be possible that one or both may be plano-convex lenses.

In addition, the coma-correcting group <NUM> may be designed to provide color correction in the light - e.g., so that the projector system may employ multiple color light (e.g., red, green and blue) in such a manner as to provide uniform magnification and avoid the use of any additional corrective optical elements. If the positive element is made from crown glass with low dispersion, and the negative element of the group <NUM> is made from a flint glass with high dispersion, then the glasses and element shape can be selected such that all light wavelengths are focused nearly the same at the primary modulator. This feature also can provide for the same magnification for each color, so that in a <NUM>-color projector, the optical system of <FIG> can be made the same for each color's light path.

Light from the coma-correcting group <NUM> may be transmitted to field flattening/spherical aberration inducing group <NUM>. Group <NUM> may be employed to provide additional spherical aberration to provide additional de-focusing/blurring to the Point Spread Function (PSF - e.g., substantially Gaussian) for the light transmitted to the second modulator.

In some embodiments, it may be possible to have relay optics system that may have one, two or three functional groups for different arrangements. For example, one relay optical system may comprise a focus group, a coma-correcting group and/or a spherical aberration inducing group in different combinations.

In projector systems that employ light recycling systems as discussed herein, <FIG> shows one possible embodiment that comprises a first modulator 1602a, a second modulator 1602b and a relay optical system that may comprise a focus group <NUM>, a coma-correcting group <NUM>, and a spherical aberration inducing group <NUM>. The focus group <NUM> and the coma-correcting group <NUM> and the spherical aberration inducing group <NUM> may function and be set substantially the same as discussed above in the case without light recycling.

However, in a system that employs light recycling, it may be desirable that the light from the first modulator 1602a has a different angle of incidence to the light path coming into the relay optical system (as is depicted by the light transmitted from surface <NUM> of 1602a). To correct for this angle of incidence, a prism <NUM> may be placed at the proximal side of the second modulator 1602b. This may be so because the light exiting the object (premodulator 1602a) is substantially at an angle of incidence of <NUM> degrees relative to the premodulator 1602a (in this case referenced as the chief ray angle), and the light arrives at the primary modulator 1602b at <NUM> degrees angle-of-incidence. This may tend to cause a loss of symmetry in the optical path that is not seen in the non-recycling case. The light path (both glass and air) to be traveled by light from all corners of the object plane to the image plane may be desired to be substantially the same. Where the image plane is found to be tilted relative to the primary modulator 1602b, a wedge of glass <NUM> may be added to one or more of the prisms in the optical path, the shape of such wedge to be determined by optimizing the design taking into consideration the focus group <NUM>, coma group <NUM> , and aberration group <NUM>.

Claim 1:
A method for controlling a projector display system comprising a light source, a first modulator (1602a), a second modulator (1602b) and a relay optical system (<NUM>) that is placed in between the first modulator and the second modulator, the light source comprising a plurality of individually modulated color emitters, said projector display system capable of recycling light from the light source the method comprising:
receiving an input image;
producing, using the first modulator, an image based on the input image; and
providing, using the relay optical system, a uniformly blurred and de-focused image to the second modulator from the image produced using the first modulator,
the method further comprising:
calculating (<NUM>), based on the input image, an average picture level for each individually modulated color;
determining (<NUM>) the relative brightness increase for each individually modulated color; and
reducing (<NUM>) the illumination source intensity to the reciprocal of the brightness increase for each individually modulated color.