Apparatus, system, and method for blending black levels in projector

Abstract

To make the brightness inside and outside an overlap area uniform.SOLUTION: An apparatus controls at least two projectors to project color channel images at multiple image levels with partial overlap in the overlap region. Using at least one sensor, the apparatus acquires digital images of the projected color channels and determines a function of projected brightness for each projector point's image level. The apparatus selects brightness levels for points outside the overlap region to blend brightness inside and outside the overlap region when projecting a black image. The apparatus then uses the function to determine the image level for each color channel and controls the projectors accordingly.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present disclosure relates generally to projectors, and more particularly to an apparatus, system and method for blending black levels in a projector. [Background technology]

[0002] A projector has a predetermined black level, which can be defined as the light output from the projector even when the projector is projecting a "black" and / or minimum-brightness pixel (e.g., a black pixel) and / or a minimum-brightness image (e.g., a black image). Different projectors may have different black levels. These black levels may have various intensities and hues, for example, across a black image projected by the projector. Furthermore, overlapping projector regions will be brighter than non-overlapping regions 418, as depicted, for example, in FIG. 1, which depicts a projected image 100 consisting of two overlapping black images (Image 1 and Image 2) projected by two different projectors according to the prior art; overlapping regions 417 are clearly seen to be brighter than non-overlapping regions 418. Such differences in black level intensity and hues can be very unpleasant and distracting when low-light content, such as an image of a night sky, is projected. 1, different projectors with different black levels having various intensities and hues indicate that the brightness and color of overlap region 417 may differ from the adjacent non-overlapping region 418 of the projected image. In particular, in a projector, "black" does not mean the absence of light; the light in the different black regions of overlap region 417 is additive, resulting in a brighter "black" than the non-overlapping region 418.

[0003] In other words, even when a projector is projecting "black," there is still some light output, which is called the black level. Different projectors have different black levels. These black levels vary in intensity and hue. Currently, it is difficult to blend (adjust, mix) the black levels of different projectors.

[0004] Furthermore, a single projector does not necessarily have corner regions of the projected image 200 that have different brightness and hue / hue than other regions of the image 200, as depicted, for example, in FIG. 2 , which depicts a projected white image 200 from a single projector according to the prior art. The white image is shown merely to illustrate variations in brightness and hue / color; it is understood that a black image from this projector can have similar variations in brightness and hue / color. In other words, the projected image 200 varies in brightness and color (e.g., hue) at least at the corners of the projected image relative to the center of the projected image 200. Furthermore, such differences in black levels from a single projector can be very distracting for content displayed in low light. In other words, a single projector can have uneven black levels that can be corrected.

[0005] Current methods for blending black levels do not adequately account for differences in black level hue or luminance intensity between projectors or for a single projector.

[0006] Furthermore, measuring these black levels with a non-specialist camera can be difficult: even at high exposure values, the black light may be too dim to measure accurately, or the measurement may be dominated by noise.

[0007] Furthermore, it is difficult to determine what the native black level of a projector is, and it is also difficult to determine what image levels (e.g., brightness levels and / or power levels) should be sent to the projector to produce a given light output. Such determinations are further complicated by the fact that individual projectors may not have uniform black levels in terms of hue or intensity.

[0008] Some current black level blending methods blend the intensities of different projectors together to smooth the overlapping areas, allowing the user to manually input the relative brightness of the different projectors.

[0009] However, manually entering the relative brightness of different projectors can be time-consuming, requires multiple renderings of black levels, and does not properly account for brightness variations and color tints that vary between projectors.

[0010] A more automated process for blending black levels involves running a binary search through a series of camera images to estimate the relative intrinsic luminance between projectors. However, this method is not always successful and can be time-consuming (processing intensive). Furthermore, taking repeated photographs to estimate the relative black levels between different projectors does not adequately account for the different luminance variations and color hues of different projectors. Furthermore, it does not account for the different camera sensitivities between different projectors.

[0011] A first aspect of the present specification provides a method including: controlling, via a computing device, at least two projectors to project respective color channel images for a plurality of color channels at a plurality of video levels such that the color channel images at least partially overlap in an overlap region; acquiring, via the computing device, respective digital images of the respective color channel images at the plurality of video levels using at least one sensor; determining, via the computing device, respective functions of projected luminance for the video levels of the plurality of color channels (the respective functions for the respective projection points of the at least two projectors) from the respective digital images; selecting, via the computing device, respective luminances for the respective projection points outside the overlap region that blend luminances of the overlap region and the non-overlapping region when the at least two projectors project respective black images; determining, via the computing device, respective image levels of the respective color channels for the projection points using the respective functions; and controlling, via the computing device, the respective projection points of the at least two projectors to the respective image levels.

[0012] A second aspect of the present specification includes a computing device including a controller and a computer-readable storage medium having stored thereon program instructions that, when executed by the controller, cause the controller to perform a series of operations, the program instructions including: controlling at least two projectors to project respective color channel images for a plurality of color channels at a plurality of video levels such that the color channel images at least partially overlap in an overlap region; acquiring, using at least one sensor, respective digital images of the respective color channel images at the plurality of video levels; determining, from the respective digital images, respective functions of projected luminance for the video levels of the plurality of color channels (the respective functions for the respective projection points of the at least two projectors); selecting, when the at least two projectors project respective black images, respective luminances for the respective projection points outside the overlap region that blend luminances of the overlap region and the non-overlapping region; determining, using the respective functions, respective image levels of the respective color channels for the projection points; and controlling the respective projection points of the at least two projectors to the respective image levels.

[0013] For example, Figure 3 depicts images 300A and 300B acquired by a camera according to the prior art, where image 300A consists of a white image projected onto a screen by a lamp-based projector (e.g., the left side of Figure 3) and image 300B consists of a white image projected onto a screen by a laser-based projector (e.g., the right side of Figure 3) (e.g., at different times). While reproduced in black and white, image 300A acquired by the camera from the lamp-based projector is understood to be bluish and labeled as such, and image 300B acquired by the camera from the laser-based projector is understood to be reddish and labeled as such, respectively. While both images may be nominally white, the camera may produce colored images 300A and 300B. [Brief explanation of the drawings]

[0014] For a better understanding of the various embodiments described herein, and to show more clearly how they may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which: [Figure 1] FIG. 1 shows an example of an overlapping projector image with black levels of varying intensity and hue according to the prior art. [Figure 2] FIG. 1 shows an example of a single projector image with non-uniform black levels according to the prior art. [Figure 3] FIG. 1 illustrates an example of camera sensitivity to different projector types according to the prior art. [Figure 4] 1 illustrates an example of a system used to implement a method of black level blending, particularly a system before implementing the method of black level blending, according to a non-limiting example. [Figure 5] 1 shows a flowchart of a method for black level blending, according to a non-limiting example. [Figure 6] 1 shows, by way of non-limiting example, an example of a simplified array of points of an image projected by a projector and the functions corresponding to the points; [Figure 7] According to a non-limiting example, an exemplary data set that may be collected in performing the method of FIG. 5 and used to determine the function of the corresponding point in the array of FIG. 6 is shown. [Figure 8] According to a non-limiting example, an exemplary data set that may be collected in performing the method of FIG. 5 and used to determine the function of the corresponding point in the array of FIG. 6 is shown. [Figure 9] According to a non-limiting example, an exemplary data set that may be collected in performing the method of FIG. 5 and used to determine the function of the corresponding point in the array of FIG. 6 is shown. [Figure 10] 5 illustrates the system of FIG. 4 before implementing a method for black level blending, according to a non-limiting example. [Figure 11] 10 shows an image projected by a projector before and after performing a black level blending method, according to a non-limiting example. DETAILED DESCRIPTION OF THE INVENTION

[0015] The automated black level blending apparatus, systems, and methods provided herein can enable projector black level characterization in multiple projectors, for example, by determining a function for each light output by the projector on a point-by-point (e.g., pixel-by-pixel) basis (e.g., every Nth pixel combined with interpolation / extrapolation, etc.) and color channel-by-color channel basis. The function is typically determined using a photon sensor (e.g., a camera and / or one or more cameras), etc. Because the method includes a separate characterization of the function for each color channel, point-by-point, the method may also consider colored black levels.

[0016] In particular, the automatic black level blending provided herein relies on a series of measurements of images projected by projectors at various intensities of different color channels using one or more sensors. A function of the light output of each projector is estimated for each different color channel, point by point, thereby enabling the determination of a black level at which a point on the projector can be controlled to blend the black level of points outside the image overlap region 417 with points within the overlap region 417. Such a function may be linear. In any case, such a function may enable the determination of a minimum image level (e.g., black level) intensity that might otherwise be too dim to measure directly using a camera or the like. Furthermore, the function can be used to calculate, point by point, the amount of light required to reach a desired black level and / or a desired color for any region of the image projected by the projector, and its respective color, as a function of the results of the different color channels.

[0017] Indeed, the term "black level" may refer to the minimum inherent brightness of a point and / or image projected by a projector, e.g., zero video level (e.g., minimum power), but the term "black level" may also refer to any suitable brightness and / or color of "black" projected by a projector.

[0018] Additionally, the term "video level" as used herein may refer to the power level and / or brightness to which a point on a projector is controlled, and may vary on a normalized scale from 0% to 100% and / or from 0 to 1, with "0" being the minimum level (e.g., corresponding to a native black level) and "100" and / or "1" being the maximum level.

[0019] Additionally, the term "point" as used herein may correspond to a pixel of an image projected by a projector and / or any smallest area of ​​such an image that can be characterized via a sensor as described herein. Thus, for example, a point may correspond to a pixel and / or a plurality of pixels representing the smallest area of ​​an image projected by a projector whose brightness can be controlled to form an image. Alternatively, or in addition, a point may correspond to every Nth pixel and / or every Nth pixel, with estimates of other pixels determined via interpolation and / or extrapolation techniques, among other possibilities, where "N" is on the order of 2-20 pixels, etc., although "N" may further vary depending on the resolution of the image.

[0020] Additionally, as used herein, the term "color channel" may refer to a component of color information that makes up an image projected by a projector. For example, many projectors generate images by combining three primary color channels: red, green, and blue (RGB). Each color channel corresponds to a respective range of wavelengths of light, and by varying the intensity of each color channel, a projector can generate a wide spectrum of colors. However, while RGB is an example of three primary color channels, any suitable number of color channels is within the scope of this specification. For example, some projectors rely on four color channels, such as red, green, blue, and white (RGBW), while others rely on six color channels, such as red, green, blue, cyan, magenta, and yellow (RGBCMY).

[0021] It is further understood that color channels can provide light according to their respective color response curves across the spectrum of light visible to the human eye, being strong at certain wavelengths and weak at others. As an example, a red color channel can include light of red, green, and blue wavelengths, but the red wavelengths are more intense than the green and blue wavelengths, causing the light in that color channel to appear red to a human viewer.

[0022] Furthermore, it is understood that while a color channel may primarily provide light in its own color wavelength range, a camera or the like capturing a digital image of a projected color channel image may "see" wavelengths of other colors because a particular color sensor in the camera may be sensitive over a wider wavelength range than the respective wavelength range of the projected color channel, which may be referred to as "crosstalk." In other words, a digital image of a projected red color channel image may contain green and / or blue components because the green and blue sensors in the camera capturing the digital image are at least partially responsive to any light incident on the camera.

[0023] Additionally, the term "sensor" as used herein may refer to a camera that captures a digital image of an image projected by a projector onto, for example, a screen and / or any other suitable surface, although any suitable sensor and / or photon sensor is within the scope of this specification.

[0024] Furthermore, it is understood that in many projectors, the projection brightness (e.g., as measured by a sensor) may increase linearly as the image level increases. As such, the function relating the projection brightness to the image level of the projector may comprise a linear function. However, in other embodiments, the projection brightness (e.g., quadratically, gamma-curve, among other possibilities) may increase in any suitable manner as the image level increases. Thus, although a linear function is used herein as an example, the function relating the projection brightness to the image level of the projector may comprise any suitable function.

[0025] Attention is now directed to FIG. 4, which illustrates a system 400 for digital black level blending in a projector.

[0026] The system 400 comprises a computing device 401 (hereinafter interchangeably referred to as computing device 401, but which may include any suitable combination of one or more computing devices), a plurality of projectors 407-1, 407-2 (hereinafter interchangeably referred to collectively as projectors 407 and generally referred to as projectors 407), at least one sensor 414 (e.g., a camera), and objects including, but not limited to, a screen 415 onto which an image from the projector 407 is projected. Indeed, it is envisioned that each projector 407 is mounted relative to the screen 415 such that an image from the projector 407 is projected onto the screen 415. It is further envisioned that the computing device 401, in combination with the projector 407 and the sensor 414, is used to implement methods described herein.

[0027] In particular, at least one sensor 414 is positioned to capture a digital image of screen 415, and more particularly, to capture a digital image of an image projected onto screen 415 by projector 407; for example, if projectors 407 are individually controlled to project images of various intensities and / or shades of red, green, and blue, at least one sensor 414 may be used to obtain a color digital image of projected image 416. In some examples, projector 407 may be controlled to project images of various intensities (e.g., shades of gray), such that at least one sensor 414 may be used to obtain a color digital image of projected image 416.

[0028] Although computing device 401 is shown in communication with projector 407 and sensor 414, system 400 may include other computing and / or communication devices communicatively disposed between computing device 401 and projector 407 / sensor 414, such as devices that generate and / or manipulate video signals provided to projector 407.

[0029] However, although this embodiment is described with respect to a screen 415, in other embodiments, the screen 415 may be replaced by an object, including a three-dimensional object, and the projector 407 may project onto the object.

[0030] Each of the projectors 407 can comprise a respective image modulator (not depicted in FIG. 4 ), and the projectors 407 are further arranged to project respective images 416-1, 416-2 (interchangeably collectively referred to as images 416 and generally referred to as images 416) onto a screen 415 formed by the respective image modulators of the projectors 407, with the respective images 416 overlapping on the screen 415 in one or more overlap regions 417. In fact, because there are two projectors 407, one overlap region 417 results, with image 416-1 including one respective non-overlapping region 418-1 and image 416-2 including one respective non-overlapping region 418-2.

[0031] As depicted, the non-overlap region 418 appears black, although it is understood that some brightness remains, as described with respect to Figures 7, 8, and 9. Thus, the overlap region 41 appears a lighter "black" (e.g., gray) because light from the image 416 is added in the overlap region 41. To better distinguish the overlap region 417 from the non-overlap region 418, a white line has been drawn around the overlap region 417 to simply indicate the perimeter of the overlap region 417. It is understood that the white line does not actually exist, but the white line indicates that there is an abrupt interface in brightness (and possibly color) between the edges of the overlap region 417 and the non-overlap region 418.

[0032] Additionally, although two projectors 407 are depicted, system 400 may be comprised of any suitable number of projectors 407 projecting overlapping images 416. As a result, all respective images 416 from all projectors 407 may at least partially overlap, and / or only adjacent images 416 may overlap. Thus, one or more overlap regions 417 may occur.

[0033] Additionally, projector 407 may comprise any suitable type and combination of projectors, including but not limited to lamp-based projectors, laser-based projectors, and the like.

[0034] Similarly, although one sensor 414 is depicted, system 400 may comprise any suitable number of sensors 414 arranged to capture digital images of image 416. Sensor(s) 414 may comprise any suitable number and / or combination of digital cameras, video cameras, charge-coupled devices (CCDs), etc., and / or any suitable sensors capable of capturing digital images.

[0035] The computing device 401 may be comprised of any suitable combination of one or more computing devices, including, but not limited to, a graphics processing unit (GPU), graphics processing device, graphics processing engine, video (image) processing device, personal computer (PC), server, etc., and generally comprises a controller 440, memory 422, and a communication interface 424 (hereinafter interchangeably referred to as interface 424), and optionally any suitable combination of input and display devices.

[0036] Interface 424 comprises any suitable wired or wireless communication interface configured to communicate wired and / or wirelessly, as desired, with projector 407 and sensor 414. Communication links and / or communication couplings between components of system 400 are represented using double-headed arrows.

[0037] The controller 440 may be comprised of a processor and / or multiple processors, including, but not limited to, one or more central processing units (CPUs) and / or one or more processing units; in either case, the controller 440 is comprised of hardware elements and / or hardware processors. Indeed, in some implementations, the controller 440 may be comprised of an ASIC (Application-Specific Integrated Circuit) and / or FPGA (Field-Programmable Gate Array) specifically configured to implement the particular digital black level blending function as described herein. Thus, the computing device 401 is preferably not a general computing device, but rather a device specifically configured to implement the particular digital black level blending function as described herein. For example, the computing device 401 and / or the controller 440 may specifically comprise a computer-executable engine configured to implement the particular digital black level blending function as described herein.

[0038] Memory 422 may be comprised of non-volatile storage (e.g., erasable electronic programmable read only memory (“EEPROM”), flash memory) and volatile storage (e.g., random access memory (“RAM”)). Programming instructions implementing the functional teachings of computing device 401 described herein are typically persistently retained in memory 422 and used by controller 440, which appropriately utilizes volatile storage during execution of such programming instructions. Those skilled in the art will recognize that memory 422 is one example of a computer-readable medium that may store programming instructions executable on controller 440. Additionally, memory 422 is also one example of a memory unit and / or memory module and / or non-volatile memory.

[0039] In particular, memory 422 stores application 430 that, when processed by controller 440, enables controller 440 and / or computing device 401 to implement certain digital black level blending functions as described herein and / or to implement the sequence of operations represented by the method of FIG. 5.

[0040] Indeed, attention is now directed to FIG. 5, which illustrates a method 500 for controlling system 400. The operations of method 500 may correspond to machine-readable instructions executed by controller 440. Method 500 need not be performed in the exact order illustrated; similarly, various blocks may be performed in parallel rather than sequentially. Accordingly, elements of method 500 are referred to herein as "blocks" rather than "steps." Method 500 may also be implemented on variations of system 400.

[0041] Further, in the following description of method 500, the video levels may consist of one or more of the brightness levels and power levels of the two projectors 407. However, the video levels may be provided in any suitable format and / or using any suitable scale and / or units.

[0042] Further, in the following description of method 500, the multiple color channels may consist of a red color channel, a green color channel, and a blue color channel, although any suitable number of color channels, any suitable set of colors is within the scope of this specification.

[0043] Similarly, in the following description of method 500, the function for a given color channel may be composed of a red function, a green function, and a blue function, although any suitable number of color functions for any suitable set of colors is within the scope of this specification. Furthermore, the function for a given color channel may include a red component, a green component, and a blue component, although for a given color channel, a unique color function may dominate. For example, the function for a red color channel may include a red component, a green component, and a blue component, but the red component is significantly higher than the green and blue components, and the green and blue components may be ignored in some examples.

[0044] Further, in the following description of method 500, the at least one sensor 414 may comprise at least one digital camera, although any suitable sensor(s) for acquiring digital images is within the scope of this specification.

[0045] In block 502, the controller 440 and / or the computing device 401 controls at least two projectors 407 to project respective color channel images of the multiple color channels at multiple video levels, where the color channel images at least partially overlap in an overlap region 417.

[0046] In block 504, the controller 440 and / or the computing device 401 uses at least one sensor 414 to acquire respective digital images of respective color channel images at multiple video levels.

[0047] In block 506, the controller 440 and / or the computing device 401 determines, from each digital image, respective functions of projection brightness versus video level for multiple color channels, each function for each projection point of the at least two projectors 407.

[0048] In block 508, the controller 440 and / or the computing device 401 selects respective intensities for respective projection points outside the overlap region 417 that blend the intensities of the overlap region 417 and the non-overlap region 418 when the at least two projectors 407 project respective black images.

[0049] In block 510, the controller 440 and / or the computing device 401 determine the image levels of each of the multiple color channels for the projected point using the respective functions.

[0050] In block 512, the controller 440 and / or the computing device 401 controls the projection points of the at least two projectors 407 to their respective image levels.

[0051] In a specific example, in block 502, controlling at least two projectors 407 to project respective color channel images of the plurality of color channels may comprise using a series of structured light patterns.

[0052] In block 506, the respective functions may be constructed from respective linear functions, and in block 510, determining the respective video levels may be based on the respective luminances at the respective zero video levels and the respective slopes of the respective linear functions for the multiple color channels.

[0053] In other words, in block 506, each function may be constructed from a respective linear function, with each intercept with the vertical axis representing the minimum achievable luminance of each color channel.

[0054] In block 510, determining respective image levels for respective projection points of the at least two projectors 407 using respective functions may include determining respective colors for a given projection point, the respective colors being determined from relative respective image levels for the multiple color channels.

[0055] Method 500 may further include selecting further respective luminances (brightness) for further respective projection points within overlap region 417 that blend the luminances (brightness) of overlap region 417 and non-overlap region 418 when at least two projectors 407 project their respective black images, determining further respective video levels for a plurality of color channels for the further respective projection points using the respective functions, and controlling, via a computing device, the further respective projection points of at least two projectors 407 to the further respective video levels.

[0056] Next, with reference to Figures 6 to 11, an embodiment of the method 500 will be described using three color channels (RGB) and assuming that the function of the method 500 is a linear function.

[0057] In particular, it is understood that blocks 502, 504 may be implemented in parallel such that at least two projectors 407 project respective color channel images while sensor 414 acquires respective digital images of the respective color channel images in block 502. In particular, computing device 401 may control each projector 407 to project a series of structured light patterns, such as checkerboards, stripes (e.g., both horizontally and vertically), of increasingly smaller squares and / or increasingly narrower stripes, finer patterns of dots, etc., while sensor 414 acquires respective images (e.g., respective color channel images) of such structured light patterns.

[0058] Additionally, a black and white structured light pattern may first be used to determine the geometry of projector 407 and sensor 414 (e.g., point correspondences therebetween), and then a full-field solid color image may be projected at various brightness levels to determine point-by-point and color channel functions. For example, once point correspondences have been determined using a black and white structured light pattern, a digital representation of the full-field solid color image may be processed to determine the brightness levels of various points in the full-field solid color image.

[0059] The structured light pattern may be the same or different for each projector 407 and / or each color channel.

[0060] For example, the same or different structured light patterns may be used by each projector 407. For example, a checkerboard pattern may be used by one projector 407 and stripes may be used by another projector 407. For example, the projectors 407 may be at different angles relative to the screen 415, and some structured light patterns may be more effective at some angles than others, and different structured light patterns may be used depending on such angle.

[0061] Furthermore, for a given projector 407, once the function for a first color channel, such as green, is determined, fewer and / or different structured light patterns may be used for other color channels, such as the red and blue color channels, because the estimated function for the first color channel may be similar to the functions estimated for the other color channels. Indeed, estimated functions for other color channels may be calculated as refinements of the function for the first color channel using "fewer" structured light measurements and / or fewer structured light measurements. For example, alignment information may be obtained using fewer dots in the structured light pattern by assuming that dot positions follow a similar function as the first color channel (e.g., which may use more dots in the structured light pattern).

[0062] Alternatively or additionally, the luminance information of the color channels may be obtained with fewer luminance samples. For example, if the luminance function of a first color channel is determined to be linear after five luminance samples, the luminance function of a second color channel may be assumed to be linear and only two or three luminance samples may be used. In this example, curve fitting may be used for five luminance samples for the first color channel to determine that the luminance is linear. Therefore, for the other color channels, the respective luminance functions may be assumed to be linear and only two or three luminance samples may be used instead of five (which may be, for example, the default number of luminance samples used until the nature of the luminance function of the first color channel is determined).

[0063] Additionally, computing device 401 may perform this process for a combination of projector 407 and sensor 414 such that one or more sensors 414 may acquire digital images of the projected structured light pattern at any given time, but only one projector 407 projects a structured light pattern for one color channel at any given time. Such a process is described in further detail in applicant's U.S. Pat. No. 10,089,778, filed August 7, 2015, and issued October 2, 2018, and applicant's U.S. Pat. No. 10,630,948, filed September 26, 2018, and issued April 21, 2020, both of which are incorporated herein by reference. In certain implementations with three or more projectors 407, two of which do not have overlapping regions, computing device 401 may perform this processing for a combination of two projectors 407 and sensors 414 that do not have overlapping regions.

[0064] Further, in this specification, the structured light patterns are projected for different video levels. For example, if it is understood that the projection brightness increases linearly with the video level, the structured light patterns may be projected for at least two video levels (e.g., resulting in two sets of structured light patterns at different projection brightness levels) such that a linear function can be derived using the projection brightness and video level for the two video levels, as depicted in Figures 7, 8, and 9.

[0065] However, if the projected luminance is understood to increase non-linearly with image level (e.g., according to a non-linear function), the structured light pattern may be projected for more than two image levels, for example, corresponding to the highest order of the known non-linear function type plus 1. For example, if the projected luminance is understood to increase quadratically with image level, the structured light pattern may be projected for at least three image levels.

[0066] In any event, the image level used to project the structured light pattern may be higher than the minimum image level so that the brightness of the structured light pattern is higher than the minimum brightness. Such an approach may ensure that sensor 414 acquires a digital image of the structured light pattern in a brightness range that matches the sensitivity of sensor 414. Such an image level may be determined heuristically and / or from the technical specifications of sensor 414 and may indicate brightness levels below which sensor 414 has limited sensitivity. In this example, the image level may be selected to result in a projected brightness that exceeds such brightness levels below which sensor 414 has limited sensitivity.

[0067] It will therefore be appreciated that a general type of function defining the relationship between projected brightness and image level may be predetermined, and the number of image levels onto which to project structured light patterns may be selected accordingly.

[0068] In any case, using such structured light patterns, we found the following:

[0069] - Correspondence between pixels of the sensor 414 and points of the respective projector 407 (e.g., as described with reference to the applicant's U.S. Patent No. 10,089,778, filed August 7, 2015, and issued October 2, 2018, and the applicant's U.S. Patent No. 10,630,948, filed September 26, 2018, and issued April 21, 2020).

[0070] -The correspondence between each point of the projector 407 (as described with reference to, for example, the applicant's U.S. Patent No. 10,089,778, filed August 7, 2015, and issued October 2, 2018, and the applicant's U.S. Patent No. 10,630,948, filed September 26, 2018, and issued April 21, 2020).

[0071] - Capability of different color channels for each point of the projector.

[0072] While such structured light patterns can be used to efficiently determine correspondences and functions, other suitable processes for determining correspondences and functions are within the scope of this specification, including, but not limited to, controlling each projector 407 to raster scan to project each point one at a time.

[0073] With respect to determining correspondence, computing device 401 may generally determine each point of projector 407 located in overlap region 417, and each additional point of projector 407 located outside overlap region 417 and / or in non-overlap region 418. Again, such determinations are described in applicant's U.S. Pat. No. 10,089,778, filed August 7, 2015, issued October 2, 2018, and applicant's U.S. Pat. No. 1,063,0948, filed September 26, 2018, issued April 21, 2020.

[0074] Thus, using the correspondences, computing device 401 can determine which points of each projector 407 are in overlap region 417 and which points of each projector 407 are in non-overlap region 418. For example, a point of first projector 407-1 is determined to be in overlap region 417 when such point corresponds with a point of second projector 407-2. Similarly, a point of first projector 407-1 is determined to be in non-overlap region 418 when such point does not have a correspondence with a point of second projector 407-2, and conversely, a point of second projector 407-2 is determined to be in non-overlap region 418 when such point does not have a correspondence with a point of first projector 407-1.

[0075] It will be appreciated that such correspondence further provides an indication of the positions of the points on the screen 415 and / or at least the positions of the points relative to each other.

[0076] Turning now to the functions of the different color channels for projector points, attention is now directed to FIG. 6, which depicts a simplified version of a 4-by-6 array 600 of points (which may correspond, for example, to array pixels) of projector 407. This array associates each point with a respective function "f," and in FIG. 6, each f r,c where "r" is the row number and "c" is the column number. So, for example, f 1,1 consists of the determined function for the first row and the first column, and f 1,2 consists of the determined function for the first row and the second column, etc.

[0077] However, although 24 points are depicted, it is understood that the number of points of projector 407 may be similar to the number of pixels of the projector (e.g., 8,294,400 pixels in a 4K projector with 3840 x 2160 pixels) and / or the number of points of projector 407 may depend on the resolution of the structured light pattern, and one point may encompass 2 pixels, 5 pixels, 10 pixels, among other possibilities.

[0078] Furthermore, each projector 407 is associated with a respective array similar to array 600, although it is understood that the number of respective points in each array may be the same or different.

[0079] An example of the function of array 600 and its determination will now be described with reference to FIGS. 7, 8, and 9. FIGS. 7, 8, and 9 show measured sensor brightness as a function of projector video level for three different color channel image sets. It will be understood that the measured sensor brightness may be normalized. For example, when multiple sensors 414 are used, calibration may be performed so that the sensors 414 measure the same brightness for the same projection point, and such measurements may therefore be normalized to a 0% to 100% and / or 0 to 1 scale, with "0" being the minimum level of brightness and "100" and / or "1" being the maximum level of brightness on the normalized scale. However, when a single sensor 414 is used, the measured sensor brightness may similarly be normalized.

[0080] 7, 8, and 9 show exemplary data sets collected for a particular point during the performance of projector 407 projecting color channel images (e.g., structured light patterns) of various intensities and / or tints (shades) of red, green, and blue in block 502 of method 500, and using sensor 414 to acquire color images of the projected color channel images. It is further understood that sensor 414 may measure red, green, and blue light separately from one another using any suitable combination of sensors.

[0081] In the data set, four different video levels were used to derive the linear function, but it is understood that only two different video levels are used for such a linear function.

[0082] 7, four different video levels of red images for a particular point of a particular projector 407 were used, and the red color channel digital image was measured by sensor 414 (e.g., using four sets of structured light patterns for the red color channel at four different video levels). Because sensor 414 is typically configured to measure red, green, and blue light, and the red color channel image has primarily red components, but may also have green and blue components, the overall redness function for the depicted point is a linear redness function f R , the linear green function f G , and the linear blue function f B It consists of:

[0083] For example, as depicted in Figure 7, the overall redness function for the depicted points is constructed as follows:

[0084] f R : Brightness = 249.47v + 0.0433··· Equation (1)

[0085] f G : Brightness = 84.384v + 0.1163··· Equation (2)

[0086] f B : Brightness = 27.795v + 0.1748··· Equation (3)

[0087] In these functions, "v" represents the video level, so the value multiplied by "v" represents the slope of the function, and the value at v=0 represents the "y" and / or vertical intercept and / or intrinsic black level when the video level is zero.

[0088] Further, with reference to FIG. 8, for the same particular point in FIG. 7, for the same particular projector 407, green images at four different video levels were used and the green color channel digital images were measured by sensor 414 (e.g., using four sets of structured light patterns for the green color channel at four different video levels), resulting in an overall green color function for the depicted point as depicted in FIG. 8:

[0089] f R : Brightness = 13.222v + 0.0703··· Equation (4)

[0090] f G : Brightness = 249.36v + 0.0752... Equation (5)

[0091] f B : Brightness = 100.56v + 0.0752... Equation (6)

[0092] Further, with reference to FIG. 9 , for the same particular point in FIGS. 7 and 8 , and for the same particular projector 407, blue images at four different image levels were used, and the digital images of the blue color channel were measured by sensor 414 (e.g., using four sets of structured light patterns for the green color channel at four different image levels), resulting in the following overall blue function for the depicted point, as depicted in FIG. 9 :

[0093] f R : Luminance = 1.1378v + 0.0729··· Equation (7)

[0094] f G : Luminance = 8.0634v + 0.1113··· Equation (8)

[0095] f B :Brightness=247.9v+0.1438...Equation (9)

[0096] Thus, equations (1) through (9) represent a particular function f for a particular point in array 600 of FIG.r,c can be expressed as:

[0097] Furthermore, in equations (1) through (9), the y-intercepts and slopes for the red, green, and blue channels are understood to be determined for luminance measured as a function of video level (e.g., projector power) when red, green, and blue images are projected onto a screen by projector 407 and sensor 414 is used to acquire color images of the projected color channel images.

[0098] It will further be appreciated that any of equations (1) through (9) may be solved for the image level "v" and the target luminance of a particular color channel may be input into such an equation to determine the image level at which each point may be controlled to achieve the target luminance.

[0099] For example, the video level applied to a point is calculated based on the following formula:

[0100]

number

[0101] The intrinsic black level in equation (10) may be the y-intercept of the corresponding equation (1)-(9), and the slope of equation (10) may be the slope of equation (1)-(9). In effect, equation (10) represents any one of equations (1)-(9), but rearranged to solve for "v" so that the "applied video level" in equation (10) corresponds to "v."

[0102] Equation (10) assumes that the functions described herein are linear, but if such functions are of another type, equation (10) can be adjusted accordingly to solve for the applied video level.

[0103] It will further be understood that exemplary data sets similar to those depicted in Figures 7, 8, and 9 may be collected for each point of each projector 407. In this manner, it will be understood that a set of nine equations may be determined for each point of array 600.

[0104] However, in some examples, only functions corresponding to the unique colors of the color channels may be used in method 500, such as in block 510. For example, only Equation (1) may be used for the red color channel, only Equation (5) may be used for the green color channel, and only Equation (9) may be used for the blue color channel.

[0105] In fact, although sensor 414 can “sense” extraneous colors of a color channel, such extraneous colors may not actually exist in the color channel, and therefore color features that are not inherent to the color channel may be ignored in some instances. For example, an image of a red color channel may not contain green or blue light, but sensor 414 may nevertheless sense green or blue light due to crosstalk. Therefore, ignoring color functions that are not inherent to the color channel can eliminate such crosstalk. In other words, such crosstalk can be eliminated by using only equations (1), (5), and (9). In fact, in some instances, equations (2), (3), (4), (6), (7), and (8) may not be determined to conserve processing resources. Nevertheless, it is understood that the red, green, and blue receptors in the human eye may sense light of other colors but in a different manner than the specific color sensor of sensor 414. Thus, while equations (2), (3), (4), (6), (7), and (8) may not strictly represent "false" information, they may not represent the response curve of the human eye's receptors and may be ignored and / or not determined. In other words, the process provided herein seeks to determine what projector 407 is projecting, not what sensor 414 and / or the human eye is seeing.

[0106] Turning now to block 508, it will be appreciated that when at least two projectors 407 project respective black images, blending the intensities of the overlap region 417 and the non-overlap region 418 and selecting respective intensities for respective projection points outside the overlap region 417 can occur in any suitable manner.

[0107] For example, computing device 401 may determine the average brightness and color of points within overlap region 417 using the functions determined in block 506. For example, assuming that each set of equations (1)-(9) is determined for a set of points from each projector 407 that overlap in overall region 417, the y-intercepts from each set of equations (1)-(9) may be added together to determine the brightness of such set of points, and the relative amounts of red, green, and blue light defined by the y-intercepts may be used to determine the color of such set of points. Such a determination may be made for each set of points within overlap region 417.

[0108] For example, by determining which points of projector 407 are within overlap region 41, the respective luminances at the y-intercepts of the equation for the corresponding points may be determined, added to obtain the sum of the luminances of each black level within overlap region 41 for points within overlap region 417, and averaged to determine the average luminance. A similar process may be used to determine the average color of the black levels of overlap region 417.

[0109] In these examples, the average brightness and average color may be selected as the target brightness and target color for the points in the non-overlap region 418, and the video level for each point in the non-overlap region 418 may be determined (e.g., in block 510) using values ​​corresponding to the target brightness and target color using the respective functions (e.g., equation (10) may be used with the y-intercept and slope from each of equations (1)-(9)).

[0110] Each point within the non-overlap region 418 may be controlled (e.g., in block 512) to a target brightness and color using the video levels determined from equation (10). In this example, the "black" brightness and / or color of points outside the overlap region 417 may be controlled to the "black" brightness and / or color of points inside the overlap region 417. In other words, light may be added to the non-overlap region 418 to increase the "black" brightness of the non-overlap region 418 to the "black" brightness of the overlap region 417, and the relative amounts of red, green, and blue light may be adjusted in the non-overlap region 418 to make the color of the non-overlap region 418 the color of the overlap region 417. However, any suitable scheme may be used to "smooth" the edges of the overlap region 417.

[0111] For example, light may be added to portions of non-overlap region 418 of projected image 416 adjacent to overlap region 417 (but not the entire non-overlap region 418) to smooth the edges of overlap region 417 relative to adjacent non-overlap region 418. The amount of light that may be added may be determined based on the method described in U.S. Patent No. 10,298,893, entitled "System And Method For Digital Black Level Blending," issued May 21, 2019 to Christie Digital Systems USA, Inc. (e.g., commonly assigned herein), and incorporated herein by reference. However, in brief summary, rather than controlling all points within non-overlap region 418 to the same brightness and color, some points in non-overlap region 418 adjacent to overlap region 417 may be controlled to grade their brightness and / or color from the brightness and / or color of points in overlap region 417 adjacent to non-overlap region 418 to the brightness and / or color of points within non-overlap region 418, thereby "smoothing" the abrupt transitions in brightness and / or color at the edges between overlap region 417 and non-overlap region 418.

[0112] In some of these examples, to smooth the overlap region 417 between different projectors 407 projecting overlapping images 416, samples (e.g., digital images of the projected images 416) may generally be taken near the edges of the overlap region 417. Stated differently, in these embodiments, rather than determining a function for all points of a given projector 407, correspondences between points of the projectors 407 may be determined using a first set of structured light patterns at a first video level, and the function may be determined only for points within a given distance (e.g., 10%, 20%, 30%, etc., of the length and / or width of the overlap region 417) from the edges of the overlap region 417. For example, a second set of structured light patterns at a second video level may be used, but to characterize only those points within a given distance of the edges of the overlap region 417.

[0113] It will be further appreciated, therefore, that smoothing the edges of overlap region 417 may include not only brightness adjustments but also color adjustments. For example, if the image projected by one projector 407 is dominated by a red hue and the image projected by the other projector 407 is dominated by a blue hue (e.g., as described with respect to FIG. 3), the "black" of overlap region 417 may be a purple hue. Thus, not only may the brightness of non-overlap regions 418 adjacent to overlap region 417 be increased, but the color of such non-overlap regions 418 adjacent to overlap region 417 may be adjusted using respective functions to blend (adjust / mix) with the color of overlap region 417.

[0114] It is further understood that such blending may include changing the brightness and / or color of the points in the overlap region 417. For example, in the overlap region 417, there may be a variation in brightness and / or color across the points of the overlap region, and the brightness and / or color of the points in the overlap region 417 may be adjusted to better blend with the color of the points in the adjacent non-overlapping region 418.

[0115] It will further be appreciated that a similar process may be used for a single projector 407 if the projected black image 416 is non-uniform. For example, if the corners of the projected black image 416 are a different brightness and / or a different color than the center of the projected black image 416, the determined function may be used to adjust the brightness and / or color of points throughout the projected black image 416 to achieve a black that is uniform in brightness and / or color throughout the projected black image 416. In these examples, the brightness and / or color of the relative black level of the projected black image 416 of the projector 407 may be determined using the determined function, and the video level of the point that minimizes the brightness and / or color difference may be determined and applied to that point.

[0116] In other words, once each projector 407 has been characterized as described herein, the brightness and color values ​​of any point in the projected image 416 of any of the projectors 407 may be calculated, and the determined function may be used to determine the respective video levels corresponding to the brightness and color values. The points of the projectors 407 may be controlled accordingly.

[0117] Additionally, to accommodate black level non-uniformities for a given projector 407 and / or overlap areas 417 of multiple projectors 407, a target image level corresponding to a target black level may generally be determined for each point of each color channel of a given projector 407 and / or multiple projectors 407. The black level may be calculated across the point of a given projector 407 and may define what the actual target black level should be. Additionally, the image level may be calculated independently for each point of each color channel. Additionally, to account for non-uniform black levels of a single projector 407, samples are generally taken across the entire projected area of ​​the single projector 407.

[0118] Indeed, attention is now directed to Figure 10, which illustrates system 400 after method 500 has been performed. In particular, the brightness and color of non-overlapping region 418 has been controlled to the same (e.g., average) brightness and color as overlapping region 411. The white lines around overlapping region 417 have been removed, relative to Figure 4, to illustrate that the edges of overlapping region 417 have blended with the adjacent edges of non-overlapping region 418.

[0119] Indeed, attention is now directed to FIG. 11 , which depicts black image 1100 projected by projector 407 before and after method 500. In particular, the brightness of black image 1100 before method 500 is depicted as being higher at the left edge than the remainder of black image 1100, as adapted for a single image and / or single projector 407. However, black image 1100 after method 500, as adapted for a single image and / or single projector 407, is depicted as having the brightness of the remainder of black image 1100 raised to the brightness at the left edge and uniform. Although color variations are not depicted, they can be similarly corrected. In particular, points of image 1100 were controlled to the target brightness and / or color by determining a function for the points of image 1100, selecting a target brightness and / or color corresponding to the average brightness and / or color along the left edge, and controlling the video level of projector 407 accordingly.

[0120] Next, aspects of calibration and / or normalization of the sensor 414 will be described.

[0121] As described herein, one or more sensors 414 (e.g., cameras) may be used to assist in determining the function, and such sensors 414 may generally have different sensitivities to different light sources. Accordingly, one or more sensors 414 may initially be calibrated for each projector 407. For example, the projector 407 may be controlled to project a relatively bright white image onto the screen 415, and the relatively bright white image may be sensed and / or acquired in a manner that does not overexpose the sensor 414 in any color channel.

[0122] For example, overexposure in a color channel may include at least one pixel and / or point being at the maximum brightness level of the sensor 414 for at least one color channel, such that the at least one pixel and / or point may be clamped. For example, a digital camera may return brightness levels between 0 and 255, etc. (e.g., on a scale of 0 to 1, or a scale of 0 to 100%, etc.). In fact, if a pixel is at maximum brightness, the measurement of the pixel may be "cut off": in other words, it is impossible to know whether the pixel is actually at maximum brightness or above maximum brightness.

[0123] For example, if a pixel is at 255 (e.g., the maximum value) in the digital image captured by sensor 414, the exposure of sensor 414 can be halved and another digital image captured. If the same pixel goes to 200 (half the exposure), the first measurement should have been 400, but it will stay at 255. Even worse, if the pixel is still at 255, the first measurement should be 510 or higher, and the actual brightness cannot be determined.

[0124] Thus, controlling the sensor 414 to sense a relatively bright white image on the screen 415 in a manner such that the relatively bright white image is not overexposed by the sensor 414 in any color channel may include sensing and / or acquiring such a bright white image at different exposures in a feedback loop with the sensor 414 until no pixels in the digital image have a value of 255 (or a corresponding maximum value) and / or until only a minimum number of pixels in the digital image have a value of 255 (or a corresponding maximum value), where the minimum value may be less than 1%, less than 0.5%, less than 0.1%, etc. of the pixels.

[0125] 3 , an image acquired by sensor 414 of a white image projected by a lamp-based projector 407 may appear generally blue, and an image acquired by sensor 414 of a bright white image projected by a laser-based projector 407 may appear generally red, even though both projectors 407 are projecting the same white image (e.g., white to the human eye). In other words, images acquired by the same sensor 414 of the same white image projected by different types of projectors 407 may have different levels of red and blue (and / or green, etc.). It should be understood that this is an example using two particular projectors 407, and that the same sensor 414 may acquire images of different shades from white images projected by different lamp-based projectors 407, and / or that the same sensor 414 may acquire images of different shades from white images projected by different laser-based projectors 407.

[0126] Therefore, because not all sensors 414 acquire images from different projectors 407 in the same way, when multiple sensors 414 are used, the sensors 414 may be calibrated to one another so that measurements from a first sensor 414 can be compared to measurements from a second sensor 414. (Even identical sensor 414 models may have different measurements because the aperture of each sensor may be manually altered.) The sensors 414 may be calibrated to one another as long as they acquire at least some common light (e.g., different sensors 414 are used to acquire the same projected image).

[0127] After acquiring the sensor 414 image of the white projected image, the next step may be to calibrate the sensor 414 readings so that the sensor 414 image appears white without any coloration. This may be done by first determining the average pixel value (e.g., luminance) of all three (e.g., red, green, and blue) color channels. A scale ratio may then be calculated to bring each color channel closer to the average pixel value. This scale ratio is used each time a data point is measured for the sensor 414 / projector 407 pair.

[0128] Furthermore, as described herein, projecting images in various shades of red, green, and blue and using sensor 414 to capture color images of the projected images can be beneficial when the color channels of sensor 414 are affected by other colors, e.g., when a color sensor type of sensor 414 is at least partially activated when light of other colors is captured by sensor 414 (e.g., as shown by equations (1)-(9)).

[0129] In some examples, one or more monochrome sensors 414 are used to capture digital images, while the projector 407 is controlled to project color channel images as described herein. In such examples, the one or more monochrome sensors 414 detect only the luminance of points in the color channel images, and not specific colors, thereby avoiding crosstalk between the color sensors 414.

[0130] Additionally, if a bright image is projected and the sensor 414 channel measurements are overexposed while the sensor 414 is acquiring a particular image of the projected bright image, the exposure of the sensor 414 may be reduced and a new image acquired. Subsequent readings may then be "normalized" to the previous exposure by scaling the readings by the ratio between the old and new exposures.

[0131] As should now be apparent, the operations and functions of the devices described herein are sufficiently complex to require implementation on a computer system and, as a practical matter, cannot be performed by the human mind. In particular, it is understood that a computing device as defined herein, in addition to the inherently digital nature of such operations (e.g., the human mind cannot directly interface with a digital projector, cannot project light, etc.), requires and provides management of speed, precision, and complexity not available with human mental processes.

[0132] Examples of the term "configured to," such as "a computing device configured to," "a processor configured to," and "a controller configured to," when executed by the computing device and / or processor and / or controller, can cause the computing device and / or processor and / or controller to perform a series of operations that include the functions that the computing device and / or processor and / or controller is configured to perform. Therefore, it should be understood that the term "configured to perform" is not unduly limited to a means-plus-function interpretation or the like.

[0133] Furthermore, references to one processor and / or controller and / or device and / or engine, etc. configured to perform a particular function are understood to include, but are not limited to, multiple processors and / or multiple controllers and / or multiple devices and / or multiple engines, etc. performing such function.

[0134] It should be understood that for purposes of this specification, the phrases "at least one of X, Y, and Z" and "one or more of X, Y, and Z" may be interpreted as X only, Y only, Z only, or any combination of two or more items X, Y, and Z (e.g., XYZ, XY, YZ, XZ, etc.). Similar logic can be applied to two or more items where phrases such as "at least one..." or "one or more..." are used.

[0135] The terms "about," "substantially," "essentially," "approximately," etc. are defined as "close," e.g., as understood by one of ordinary skill in the art. In some instances, the term is understood to be "within 10%," in other instances "within 5%," in yet other instances "within 1%," and in yet other instances "within 0.5%."

[0136] Those skilled in the art will recognize that many more alternatives and modifications are possible, and that the above-described embodiment is merely illustrative of one or more embodiments, the scope of which is therefore limited only by the claims appended hereto.

[0137] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Patent Application No. 63 / 567995, filed March 21, 2024, which is incorporated herein by reference.

Claims

1. controlling, via a computing device, at least two projectors to project respective color channel images for a plurality of color channels at a plurality of video levels, such that the color channel images at least partially overlap in an overlap region; acquiring, via the computing device, digital images of each of the color channel images at the plurality of video levels using at least one sensor; determining, via the computing device, from the respective digital images, respective functions of projected luminance versus video level of the plurality of color channels (the respective functions for the respective projection points of the at least two projectors); selecting, via the computing device, a luminance of each of the projection points outside the overlap region that is a blend of luminances of the overlap region and the non-overlapping region when the at least two projectors project their respective black images; determining, via the computing device, an image level for each of the plurality of color channels for the projection point using the respective functions; and controlling, via the computing device, the respective projection points of the at least two projectors to the respective image levels. method.

2. controlling the at least two projectors to project each color channel image of the plurality of color channels comprises using a series of structured light patterns; The method of claim 1.

3. the respective functions include respective linear functions, and determining the respective video levels is based on respective luminances at respective zero video levels and respective slopes of the respective linear functions for the plurality of color channels. The method of claim 1.

4. the respective functions include respective linear functions, each having a vertical axis intercept representing the minimum achievable luminance of the respective color channel; The method of claim 1.

5. determining the respective image levels for the respective projection points of the at least two projectors using the respective functions further includes determining a respective color for a given projection point, the respective color being determined from the relative respective image levels for the plurality of color channels; The method of claim 1.

6. the video levels include one or more of brightness levels and power levels of the two projectors; The method of claim 1.

7. selecting additional respective intensities for additional respective projection points within the overlap region that blend intensities of the overlap region and the non-overlapping region when the at least two projectors project the respective black images; determining, for each projection point, further respective video levels for the plurality of color channels using the respective functions; and controlling, via the computing device, each projection point of the at least two projectors to each image level. The method of claim 1.

8. the plurality of color channels including a red color channel, a green color channel, and a blue color channel; The method of claim 1.

9. the functions for a given color channel include a red function, a green function, and a blue function; The method of claim 1.

10. the at least one sensor includes at least one of a charge coupled device and a digital camera; The method of claim 1.

11. A controller; a computer-readable storage medium having stored thereon program instructions that, when executed by the controller, cause the controller to perform a series of operations; The program instructions include: controlling at least two projectors to project respective color channel images for a plurality of color channels at a plurality of video levels, such that the color channel images at least partially overlap in an overlap region; acquiring, using at least one sensor, a digital image of each of the color channel images at the plurality of video levels; determining, from the respective digital images, respective functions of projected luminance versus video level of the plurality of color channels (the respective functions for the respective projection points of the at least two projectors); selecting a luminance of each projection point outside the overlap region that is a blend of luminances of the overlap region and non-overlapping region when the at least two projectors project their respective black images; determining an image level for each of the plurality of color channels for the projection point using the respective functions; and controlling the respective projection points of the at least two projectors to the respective image levels. Computing devices.

12. controlling the at least two projectors to project each color channel image of the plurality of color channels includes using a series of structured light patterns; The computing device of claim 11.

13. the respective functions include respective linear functions, and determining the respective video levels is based on respective luminances at respective zero video levels and respective slopes of the respective linear functions for the plurality of color channels. The computing device of claim 11.

14. the respective functions include respective linear functions, each of whose vertical axis intercepts represents the minimum achievable luminance of the respective color channel; The computing device of claim 11.

15. determining the respective image levels for the respective projection points of the at least two projectors using the respective functions further includes determining a respective color for a given projection point, the respective color being determined from the relative respective image levels for the plurality of color channels; The computing device of claim 11.

16. the video levels include one or more of brightness levels and power levels of the two projectors; The computing device of claim 11.

17. The series of operations is: selecting additional respective intensities for additional respective projection points within the overlap region that blend intensities of the overlap region and the non-overlapping region when the at least two projectors project the respective black images; determining, for each projection point, further respective image levels for the plurality of color channels using the respective functions; and controlling, via the computing device, each projection point of the at least two projectors to each image level. The computing device of claim 11.

18. the plurality of color channels includes a red color channel, a green color channel, and a blue color channel; The computing device of claim 11.

19. the functions for a given color channel include a red function, a green function, and a blue function; The computing device of claim 11.

20. the at least one sensor includes at least one of a charge coupled device and a digital camera; The computing device of claim 11.

Images