Display spatial brightness control

A system includes a spatial light modulator (SLM) configured to project an image. The system also includes a controller coupled to the SLM. The controller is configured to receive the image and determine a brightness level of the image. The controller is also configured to enforce a brightness limit on the image responsive to the brightness level, to produce a reduced image. The controller is configured to instruct a display to display the reduced image.

BACKGROUND

Imaging systems are used for a variety of applications, such as projectors, displays, automotive heads-up displays (HUDs), near-eye displays, augmented reality (AR) systems, virtual reality (VR) systems, and many others. Some imaging systems use spatial light modulators (SLMs) to modulate a beam of light to produce an image, such as by modulating the intensity of the beam of light. One type of SLM is a digital micromirror device (DMD). A DMD is a micro-electrical-mechanical system (MEMS) that has on its surface an array of several hundred thousand or millions of microscopic mirrors. Each micromirror corresponds to a pixel in an image that is projected onto the micromirrors and then reflected from the micromirrors to a display. Other types of SLMs are liquid crystal display (LCD) systems, liquid crystal on silicon (LCoS) systems, or microLED (light emitting diode) displays.

SUMMARY

In accordance with at least one example of the description, a method includes receiving, by a controller, an image. The method also includes determining a brightness level of the image. The method includes reducing an attribute of the image responsive to the brightness level being above a threshold, to produce a reduced image. The method also includes instructing, by the controller, a display to display the reduced image.

In accordance with at least one example of the description, a system includes a spatial light modulator (SLM) configured to project an image. The system also includes a controller coupled to the SLM. The controller is configured to receive the image and determine a brightness level of the image. The controller is also configured to enforce a brightness limit on the image responsive to the brightness level, to produce a reduced image. The controller is configured to instruct a display to display the reduced image.

In accordance with at least one example of the description, an SLM is configured to display an image. An optical system is optically coupled to the SLM, the optical system configured to project the image. A controller is coupled to the SLM. The controller is configured to determine an identification (ID) of the SLM. The controller is also configured to receive the image. The controller is configured to determine a brightness level of the image, where the brightness level is based at least in part on the ID of the SLM. The controller is configured to enforce a brightness limit on the image responsive to the brightness level and the ID.

DETAILED DESCRIPTION

SLMs are used in a variety of applications. Some applications are designed to use the full brightness of the SLM, such as a projector for a conference room or a theater. The full brightness of the SLM provides a high definition image with a high dynamic range. Other applications use a lower light output or brightness, such as a near-eye display or a HUD. These other applications may display information on a limited portion of the display area, or they may display information at a lower brightness. These low brightness applications may rarely use the full brightness capabilities of the SLM. The same SLM is useful for the high brightness application and the low brightness application. A manufacturer of SLMs may want to charge a lower price for an SLM used in a low brightness application, and charge a higher price for a similar SLM used in a high brightness application. However, a customer could purchase a lower-priced SLM and use it in a high brightness application, thereby defeating the pricing structure. Also, an SLM for a low-brightness application may include a different thermal dissipation allowed for a given lifespan compared to an SLM in a high brightness application. The ability to pull heat from the device through means such as heat-sinking or airflow, or the ability to transfer heat from the mirrors themselves to the ambient environment via alternative packaging techniques, may be different for low brightness applications compared to high brightness applications.

In examples herein, a single SLM chipset, or different SLM chipsets with minor differences, are useful in a variety of applications. The SLM chipsets may be priced differently based on the application. SLM chipsets for high brightness applications may command a premium price due to enhanced power handling capabilities or expected device lifetimes, while SLM chipsets for lower brightness applications may be sold at a lower price. The lower price may be in part due to differences in construction of the SLM chipsets. These differences in construction for different SLM chipsets may include different power dissipation abilities, or differences in other features such as image quality, device lifetime, or allowable defect density. To reduce the possibility of a less expensive or low brightness SLM chipset being purchased and deployed in a high brightness application, examples herein control the allowable spatial brightness of the low brightness SLM chipsets. For low brightness applications, the total image power (e.g., a brightness level) may be limited to a certain percentage of full brightness. A controller in the SLM chipset may monitor the images for display and reduce the brightness level or reduce fidelity to ensure the brightness level of the image remains below a brightness limit. In another example, an SLM chipset may have an identification (ID) function available that identifies its capabilities (e.g., full brightness or limited brightness). A controller may read the ID and manage the SLM chipset according to the capabilities associated with the ID. The ID may indicate a maximum picture level in one example, described below. Also, the examples herein introduce little to no additional costs on existing SLM chipsets, because existing SLM controllers use algorithms to monitor brightness, and these algorithms may be extended and/or modified to limit brightness for low brightness applications, in accordance with examples described herein.

In an example, systems described herein may be used in a near-eye display. Near-eye displays are head-mounted or wearable displays. A near-eye display creates a virtual image in the field of view of one or both eyes. Immersive near-eye displays block a user's view of the real world and create a large field of view image, typically 30-60 degrees for cinema glasses and 90+ degrees for virtual reality displays. These products can act as a user's personal cinema or gaming environment. See-through near-eye displays leave the user's view of the real world open and create either a transparent image or a very small opaque image that blocks only a small portion of the user's peripheral vision. The see-through category may have two applications: augmented reality and smart glasses. Augmented reality headsets typically have a 20 to 60 degree field of view and overlay information and graphics on top of the user's view of the real world. Smart glasses typically have a smaller field of view and a display at which the user glances periodically rather than looking through the display continuously. Near-eye displays may be used in a variety of applications in both industrial and consumer markets. Near-eye displays may be used for warehouse management, equipment repair and assembly, remote control of drones or robots, or virtual reality training simulators. Near-eye displays may also be used for augmented reality gaming, outdoor activity monitors, 3D gaming, and 3D movies.

Systems described herein may also be used for automotive applications, such as HUDs and headlamps. Exterior and interior display and light applications may be realized using examples herein. As an example, an image may be projected onto a windshield to provide information to the driver. The driver's situational awareness may be enhanced and the driving experience improved with an automotive HUD. Also, headlight systems may increase brightness for drivers on the road while reducing the glare of oncoming traffic or reflections from high-gloss traffic signs. Customizable beam patterns include the ability to partially or fully dim individual pixels, creating headlight systems that allow drivers to keep their high-beams on while operating their vehicle in sub-par conditions.

Systems described herein may also be used for 3D printing applications. In 3D printing, a model of the object to be printed is converted into a series of cross-sectional slices that are sent to the 3D printer. For each cross-sectional slice of the object, the SLM projects patterned light that selectively exposes and hardens the resin. Because an entire layer is exposed with a single pattern, fast build speeds are achieved independent of layer complexity. Projection optics can also be used to control the resolution on the image plane and adjust the layer thickness, leading to smooth and accurate finished parts.

FIG.1is a block diagram of an SLM chipset100in accordance with various examples herein. SLM chipset100includes a controller102, memory104, interface106, power management integrated circuit (PMIC)108, light emitting diodes (LEDs)110, LED driver112, SLM114, executable code116, and bus118. SLM chipset100may include other components in other examples. In some examples, some components, such as PMIC108and LED driver112, may be integrated together.

Controller102manages many of the operations of SLM chipset100. Controller102may be one or more controllers or one or more processors in some examples. Controller102also controls the pattern of the elements of SLM114. Video or image data for display is received by SLM chipset100via interface106, for example, from an external storage device or video source. Memory104may store executable code, such as executable code116, for monitoring brightness of the video or image data, in accordance with examples herein. An algorithm may be embodied in executable code116. Executable code116may run on controller102. PMIC108provides power for the components in SLM chipset100. LED driver112provides a configurable current to LEDs110to control the light output of LEDs110. SLM114modulates light to produce an image for display, and is configured to project the image for display. In one example, SLM114is a DMD, which receives light from LEDs110and reflects the light to produce an image on a display. Bus118couples the components of SLM100to one another and provides for communication between the components.

In one example herein, controller102(or a different controller or processor) executes executable code116in memory104to monitor the brightness level of the image that is sent to SLM114for display. Brightness may be monitored by calculating an average picture level (APL) of the image for display. The APL is the percentage of the display that is on and bright compared to a full white display. With an SLM114that uses LEDs110to display images, red, green, and blue LEDs110are used to produce colored light that is reflected by SLM114for display. To produce a completely white image on the display, each LED110is on and fully reflected by SLM114. The APL for a full white image would be 100%. A completely black image on the display may be produced by no light being reflected for display, and the APL would be 0%. For a completely red image, blue image, or green image, the APL would be 33%. As another example, if half of the display is fully white and half of the display is fully black, the APL would be 50%. Monitoring the APL allows controller102, LED driver112, or another component of SLM chipset100to limit the APL to a maximum allowed brightness limit, known herein as the maximum picture level (MPL). Limiting the APL limits the brightness of the display. By limiting the APL, some SLM chipsets100may be limited to low brightness applications and restricted from use in high brightness applications. In one example, executable code116may embody a content-adaptive illumination control (CAIC) algorithm that calculates the APL of each frame. The CAIC algorithm embodied in executable code116processes video content on a frame-by-frame basis, and calculates the APL for each frame as part of that processing. Therefore, the CAIC algorithm is useful to monitor the APL and enforce an MPL.

Controller102manages the operation of components in SLM chipset100. Controller102may monitor the APL based on an analysis of the images sent to SLM chipset100for display. Controller102provides instructions to SLM114that produce the image for display. Therefore, controller102may limit the brightness of the image for display by executing any appropriate executable code116to monitor and/or restrict the brightness of the image, such as the CAIC algorithm. For example, the MPL may be set at 25%. With an MPL of 25%, 25% of the display may display a full brightness image while the other 75% of the display is restricted and cannot display an image. Alternatively, 50% of the display may display an image with 50% brightness, while the other 50% of the display cannot display an image. As another alternative, the entire display may display an image, but with only 25% maximum brightness on any portion of the display. In another example, if the CAIC algorithm determines that the brightness level of an image exceeds the MPL, the brightness of some of the pixels in the image may be reduced by controller102so the image that is ultimately provided to SLM114for display is a reduced image that has a brightness level below the MPL. In this manner, controller102may monitor the APL and appropriately restrict the images displayed, to prevent the APL from surpassing the MPL.

In examples herein, SLM chipsets100restricted to low brightness applications may still provide images at full brightness and full dynamic range. However, those full brightness images are restricted to a subsection of the display. Therefore, a low brightness (and lower cost) SLM chipset100may be suitable for a HUD or a near-eye display, where only a subsection of the display area is used to display information. A low brightness SLM chipset100may be purchased at a lower price than a high brightness SLM chipset100, which allows SLM chipsets100to be used in a wider variety of applications. Customers who purchase low brightness SLM chipsets100may be informed of the MPL and any other brightness limits in a datasheet, for example. If SLM chipsets100are offered with a variety of different MPLs, the customer can choose an SLM chipset100with an MPL that matches the requirements of the customer's application.

FIG.2Ashows four images with an APL of 25% in accordance with various examples herein. In other examples, a different APL maybe used, such as 10%, 33%, 50%, or any other APL. The images are examples of images that may be displayed on a display using an SLM chipset100where a brightness limit is enforced. In these examples, full brightness is indicated by the white or light portions of the images202,204,206, and208. If SLM chipset100has an MPL of 25%, full brightness is allowed on 25% of the display area if the rest of the display area has 0% brightness (e.g., the darker (shaded) image portions inFIG.2A, which may be black in some examples). Any portions of the display are useful as the high brightness areas.

In image202, a single white portion210has full (100%) brightness. Portion210is 25% of the area of image202. The other 75% of image202, portion212, is therefore black and has 0% brightness. The APL of image202is 25%.

In image204, a single white portion214has full brightness. Portion214is 25% of the area of image202. The other 75% of image202, portion216, is black and has 0% brightness. In image204, the portion with full brightness is at the bottom of the display. Image204provides an example of how an automotive HUD may operate with an MPL. An automotive HUD may display information to a driver on the bottom portion of a windshield, where full brightness is useful. The upper portions of the windshield may rarely be used to display information, and therefore limiting maximum brightness to a portion of the screen is suitable for this application. The APL of image204is also 25% in this example.

In image206, two different portions218and220have full brightness. In total, portions218and220cover 25% of image202, so this configuration also has an APL of 25%. Portion222is black with 0% brightness.

Image208includes a large number of separate portions of the image at full brightness. The total area of those portions is 25% of the area of image208, so the APL of image208is 25%. Image208shows that the bright and dark portions can be distributed about an image in any suitable configuration, so long as the APL does not exceed 25% in this example. For example, a near-eye display may display text or images on numerous small portions of the display at full brightness, while the majority of the area of the display has a low brightness level. As shown in image208, a number of smaller, bright portions are visible on the display. The rest of the display has an image at a lower brightness. For a near-eye display, a user may want to view text, graphics, or other information on a small portion of the display. As an example, a user may want to see information displayed in the lower left portion of the field of view, with the rest of the field of view unobstructed so that the user can view the real world. In another example, the user may want to see text or graphics in the bottom left, bottom center, and top left of the display, with the rest of the field of view unobstructed. Image208shows that images may be placed in small locations throughout the field of view, while a large portion of the field of view remains unobstructed. The text or images may be displayed at high brightness or full brightness, while other portion of the display may have low brightness or not display any images.

FIG.2Bshows two additional images250and252with an APL of 25% in accordance with various examples herein. In image250, the entire display is used to display an image, but the image has a maximum brightness of 25%. Image250shows a scenario where the entire display is used, but the brightness is reduced everywhere in image250. In this example, the brightness of every pixel is 25%, which makes the APL 25%. Image250therefore does not exceed the MPL of 25%.

Image252is an example of a large portion of an image at reduced brightness, with another portion of the image at 0% brightness. In image252, portion254constitutes approximately 50% of the display area, while portion256has 0% brightness for the other 50% of the display area. Because 50% of the display area is used to display an image, portion254may have up to 50% brightness, and the system still remains below the MPL of 25%. In other examples, any combination of brightness and display area may be used, as long as the total brightness remains below the MPL. For example, a portion of the screen may be at 100% brightness, another portion at 75% brightness, another portion at 25% brightness, and the rest at 0% brightness. These types of combinations are useful to display different types of data at different brightness levels, while remaining below the MPL for the entire display. Any number of different brightness levels may be used to display data or images, and any number of different portions of the screen may be used to display data or images.

Reducing an attribute of the image, such as the brightness level of the image, is one example for enforcing an MPL in SLM chipset100. In other examples, dynamic range is an attribute that may be reduced in addition to, or rather than, reducing brightness. Reducing dynamic range is another method to differentiate low brightness SLM chipsets100from high brightness SLM chipsets100. A low brightness SLM chipset100may restrict the dynamic range of an input video or image that attempts to exceed the MPL. The reduced dynamic range would produce a reduced image that is a distorted or incomplete image. If the MPL is exceeded, the dynamic range may be reduced below a predetermined limit based on the allowable MPL.

In another example, controller102may enforce an MPL with a digital limit imposed on the data sent to an SLM114to reduce the brightness of the image. If SLM114is a DMD, digital signals are sent to the DMD that indicate which pixels are on and off, and how bright each of those pixels are, to properly display the programmed image with the DMD. The brightness of each pixel is set with a series of bits, with the status of the most significant bit (MSB) of the series of bits having the largest impact on the brightness of the pixel. For example, an MSB may be set to 1 or 0, with 1 used to indicate the MSB is set, and 0 used to indicate the MSB is not set. To limit the brightness and enforce an MPL, the number of MSBs that can be set to 1 for the pixels of an image is restricted. In one example, only 25% of the pixels in a given frame may have an MSB with a value of 1; the rest of the MSBs are set to 0. Those pixels that utilize the MSB may be placed anywhere within the frame. Other bits beside the MSB (such as the second most significant bit) may have no restrictions, or those bits may have some restrictions as well in some examples.

To restrict the number of MSBs that are allowed to be in use at one time to display an image, controller102may use a counter that counts the number of MSBs transmitted to SLM114for each frame to be displayed. The counter may be embodied in hardware or software, or a combination of the two. As the pixels are transmitted to SLM114, controller102increments a counter for each MSB that is in use. After the counter reaches the limit of MSBs for a given frame, controller102would no longer transmit MSBs to SLM114for that frame (e.g., the MSBs for each subsequent pixel of that frame would be inactive). Therefore, controller102would enforce a limit on the image, and the image would appear distorted if a user attempted to display an image with brightness above a limit, as determined by the number of MSBs in the image. For the next frame to be displayed, the MSB counter would reset, and controller102would again send MSBs to SLM114until the MSB limit is reached.

In another example, an MPL may be enforced by blanking the display. If a user attempts to display a frame of an image that exceeds the MPL, the controller102may instruct SLM114to display a blank image on the display. If the next frame does not exceed the MPL, the next frame is displayed without limit. As an alternative, the dynamic range of the image may be reduced rather than blanking the screen if the image exceeds the MPL.

In another example, the attribute that is modified to reduce brightness of the image is the power provided to LED110. Brightness may be controlled or limited by limiting the power provided to a light source such as LED110. Controller102may control LED driver112or LEDs110in some examples. Controller102may send an instruction to LED driver112to reduce power to LEDs110if the MPL is exceeded. Reducing power to LEDs110reduces the brightness of the image displayed, which enforces the MPL. If another illumination source other than LEDs are used, power may be reduced to that illumination source to reduce the brightness level and produce a reduced image for display. To reduce brightness in other examples, any suitable method is useful to lower the light output of an illumination source.

In some examples, an SLM chipset100includes an ID stored in firmware or software. The ID could be hard-coded in read only memory (ROM), encoded in one-time programmable memory, stored in electrically erasable programmable ROM (EEPROM), or encoded and stored using any other appropriate technique. The ID may be unique for that SLM chipset100, and/or may indicate that the SLM chipset100belongs to a specific class of chipset. Each SLM chipset100may be assigned to a specific class based on the MPL of that SLM chipset100. For example, a first class may indicate that the SLM chipsets100have a 25% MPL. A second class of SLM chipsets100may have an MPL of 35%, while a third class of SLM chipsets100has an MPL of 50%. Finally, a fourth class of SLM chipsets100may have an MPL of 100%, and this class would be unrestricted in their operation. The ID of an SLM chipset100may identify to which of the four classes the SLM chipset100belongs. The SLM chipsets100may be priced according to their class, with SLM chipsets100having higher MPLs priced higher than SLM chipsets100having lower MPLs. In this manner, customers may purchase lower-priced SLM chipsets100for applications where less brightness is adequate, such as a near-eye display or a HUD, or for applications that are price-sensitive. Customers that want high brightness, for applications such as home theater projectors, may purchase the SLM chipsets100that provide for 100% brightness with no restrictions. In some examples, controller102is configured to read the ID and then enforce the MPL associated with SLM chipsets100in the class indicated by the ID.

FIG.3is a block diagram of a near-eye display300in accordance with various examples herein. Near-eye display300may be an AR system that provides information in a portion of the field of view of the user, in some examples. Near-eye display300in this example includes an illumination system302, an SLM304, and an optical system306. Optical system306includes optics308and a waveguide310. An eye312of a user receives the image produced by near-eye display300. One eye312is shown here for simplicity. In some near-eye displays300, two images are produced, one image for each eye. Near-eye display300also includes controller314and memory316. Executable code318may be stored in memory316. Near-eye display300also includes bus320. Bus320couples the components of near-eye display to one another and provides for communication between the components.

The illumination system302includes a light source (e.g., red, green, blue (RGB) LEDs) and illumination optics to guide light onto SLM304. SLM304reflects the incoming light to create the image with the use of optical system306. Optical system306is optically coupled to SLM304, and is configured to project an image by collecting the light reflected off SLM304and directing it into eye312. Near-eye display300forms a pupil, and eye312converts the light from near-eye display300into an image on the retina of eye312. In one example, optics308provide the light to waveguide310in optical system306. Optics308may include magnifying optics, pupil forming optics, and collimating optics in one example. The use of waveguide310allows for optics and illumination components to be located out of the field of view of eye312, for example, on the side of the user's head. This orientation leaves only a relatively small, light, transparent waveguide optical element in front of the eye312that directs the image to eye312. A near-eye display300such as this provides one example of a system where an SLM chipset100with reduced MPL may be used effectively.

Controller314and memory316operate similarly to controller102and memory104described with respect toFIG.1above. Controller314may be one or more controllers or one or more processors in some examples. Controller314may enforce an MPL for near-eye display300using any of the techniques described above. As described above, a near-eye display300, in general, displays information on a limited portion of the display area, and/or displays information at a lower brightness level. Near-eye display300is used to augment a user's vision, but generally not to completely cover a user's field of view. A customer may therefore purchase an SLM chipset100with reduced MPL at a lower cost for near-eye display300, which provides adequate performance for near-eye applications even though the MPL is limited.

In some examples, near-eye display300displays images to a user similar to image204or image206inFIG.2A. With image204, images may be displayed on a bottom portion of the display at full brightness, while no images are displayed on the upper portion of the display. With image206, full brightness images may be displayed on certain portions of the user's field of view, as long as the total area of those portions of full brightness do not exceed the MPL. Alternatively, near-eye display300may display images similar to image208, where information is displayed in a number of different locations within the field of view of the user. The information may be displayed at full brightness in some portions of the image, as long as the MPL is not exceeded.

Controller314may enforce the MPL using any of the techniques described herein. In one example, controller314may reduce brightness of certain portions of the displayed image so the total brightness remains below the MPL. In another example, dynamic range may be reduced in addition to, or rather than, reducing brightness. Controller314may enforce an MPL by limiting the number of MSBs sent to an SLM in one example. An MPL may be enforced by blanking the display in another example. In yet another example, power to LEDs110or another illumination source may be reduced to lower the brightness of the image below the MPL. Any other suitable method is useful to reduce the output of an illumination system in other examples.

FIG.4is a flow diagram of a method400for enforcing a brightness level of an image in accordance with various examples herein. The steps of method400may be performed in any suitable order. The hardware components described above with respect toFIGS.1and3may perform method400in some examples, such as controller102or controller314.

Method400begins at410, where a controller receives an image. The image may be an image for display using an SLM in one example. The controller may be a controller such as controller102or controller314as described above. In an example, controller102or controller314receives each image for display and then provides instructions to other components of SLM chipset100so the image may be displayed.

Method400continues at420, where a controller determines a brightness level of the image. The brightness level of the image may be determined using any suitable algorithm embodied in executable code as described above. In one example, a CAIC algorithm determines an APL of the image. In one example, the CAIC algorithm processes incoming data for a frame of an image. The CAIC algorithm generates an APL based on the average intensity of the pixels over the entire frame. The CAIC algorithm may also calculate the APL of each color in the frame. The APL provides an indication of the brightness level of the image. Other suitable algorithms are useful to determine a brightness level. In another example, the number of MSBs for the image is a measure of the brightness level of the image. Controller102may keep a count of the number of MSBs in the image to determine the brightness level as described above.

Method400continues at decision block430. At decision block430, the method determines if the brightness level is at or below a threshold. The threshold may be a brightness limit like an MPL, where the MPL is 25% or 50% of the maximum brightness of the display. In another example, the threshold is a certain number of MSBs in the image. In another example, the brightness level is set by determining an ID of the SLM, and then setting the brightness level based on the ID. The ID may denote the class of the SLM chipset as described above, with different classes having different brightness levels in some examples.

If the brightness level of the image is at or below the threshold, the method400proceeds to440. At440, the controller instructs a display to display the image. If the brightness level of the image is at or below the threshold, the image is displayed without altering the image. For example, if the APL of the image is below the MPL, as determined by controller102, then the brightness level is at an acceptable level and the image is displayed without limit. In another example, if the number of MSBs in the image is below the allowable number of MSBs per image, the image is displayed without alteration.

If the brightness level of the image is above the threshold, the method400proceeds to450. At450, the controller reduces an attribute of the image to produce a reduced image. A controller, such as controller102, may enforce the MPL using any of the techniques described herein to reduce an attribute of the image. In one example, controller102may reduce brightness of certain portions of the displayed image so the total brightness level remains below the MPL. Controller102may select the certain portions using any suitable technique. For example, if the pixels of the image are transmitted to the display as a sequence of bits, the first bits transmitted may be displayed normally, while the bits for later pixels may have their brightness reduced to remain below the MPL. In another example, one or more rules could be implemented to determine how to reduce brightness of certain portions. For example, images in the center of the display may be reduced in brightness first. Images toward the outer edges of the display are reduced in brightness next, and the process continues until the APL is below the MPL. In another example, brightness may be reduced starting on one edge of the display and moving toward the other edge of the display until the APL is below the MPL. In yet another example, dynamic range may be reduced in addition to, or rather than, reducing brightness. To reduce dynamic range, the brightest portions of the image may have their brightness reduced systematically until the APL of the entire image is below the MPL. In another example, the dynamic range may be reduced by reducing the brightness difference between the brightest portions and the darkest portions of the image, creating a washed-out look for the image. If the brightness level is above a first threshold, the dynamic range may be reduced until the dynamic range is below a second threshold. The first threshold may be based on the APL, while the second threshold may be based on a measure of the dynamic range of the image. Controller102may enforce an MPL by limiting the number of MSBs sent to an SLM in another example, as described above. In another example, an MPL may be enforced by blanking the display. In another example, power to LEDs or another illumination source may be reduced to lower the brightness level of the image. Any of the techniques described herein are useful to enforce the brightness level of the images for display.

Method400proceeds to460, where the controller instructs a display to display the reduced image. The reduced image includes a reduced attribute, such as a brightness below the MPL or a reduced dynamic range.

In examples herein, SLM chipsets may be priced differently based on the intended application of the SLM chipset. SLM chipsets for high brightness applications may command a premium price due to enhanced power handling capabilities or expected device lifetimes, while SLM chipsets for lower brightness applications may be sold at a lower price. A controller in the SLM chipset may monitor the images for display and reduce the brightness level or reduce fidelity to ensure the brightness level of the image remains below a brightness limit. An SLM chipset may have an ID that identifies its capabilities (e.g., full brightness or limited brightness). The examples herein are not simple for a customer to defeat or bypass, and they would also rarely cause an SLM chipset to be falsely limited. Also, the examples herein introduce little to no additional costs on existing SLM chipsets, because existing SLM controllers use algorithms to monitor brightness, and these algorithms may be extended and/or modified to limit brightness for low brightness applications, in accordance with examples described herein.

In this description, the term “couple” may cover connections, communications, or signal paths that enable a functional relationship consistent with this description. For example, if device A provides a signal to control device B to perform an action, then (a) in a first example device A is directly coupled to device B, or (b) in a second example device A is indirectly coupled to device B through intervening component C if intervening component C does not substantially alter the functional relationship between device A and device B, so device B is controlled by device A via the control signal provided by device A.

Unless otherwise stated, “about,” “approximately,” or “substantially” preceding a value means+/−10 percent of the stated value. Modifications are possible in the described examples, and other examples are possible within the scope of the claims.