Intel Patent | Three Dimensional Glasses Free Light Field Display Using Eye Location
Patent: Three Dimensional Glasses Free Light Field Display Using Eye Location
Publication Number: 20200204781
Publication Date: 20200625
Applicants: Intel
Abstract
In some examples, a three dimensional display system includes a display (for example, a display screen or a display panel), a micro lens array, and an eye tracker to track one or more eyes of a person and to provide eye location information. The display system also includes a rendering processor to render or capture color plus depth images (for example, RGB-D images) or light field images. The display system also includes a light field processor to use the eye location information to convert the rendered color plus depth images or light field images to display images to be provided to the display.
TECHNICAL FIELD
[0001] This disclosure relates generally to three dimensional (3D) display.
BACKGROUND
[0002] Technology needed to deliver stereo three dimensional (3D) video content such as 3D TV, cinema, gaming, etc. has increasingly entered mass market products (for example, such as Virtual Reality, 3D Cinema, 3D smartphones, etc.) Some stereo 3D displays such as active/passive glasses-based, multi-view lenticular, etc. deliver a different image to each eye in a stereo pair. These independent images can be, for example, stereoscopically fused in a user’s brain, effectively re-creating a binocular experience of 3D visual perception.
[0003] In real world situations, when a human is observing a particular subject, for example, their eyes both converge and focus (or accommodate) to the distance of the subject. However, in many stereo three dimensional displays, a user is not able to converge and focus (or accommodate) to the distance of the subject.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] The following detailed description may be better understood by referencing the accompanying drawings, which contain specific examples of numerous features of the disclosed subject matter.
[0005] FIG. 1 illustrates a real world viewing environment;
[0006] FIG. 2 illustrates a three dimensional (3D) display viewing environment;
[0007] FIG. 3 illustrates a three dimensional (3D) display system;
[0008] FIG. 4 illustrates temporal multiplexing;
[0009] FIG. 5 illustrates an eye box;
[0010] FIG. 6A illustrates an eye box;
[0011] FIG. 6B illustrates a display and a micro lens array;
[0012] FIG. 7 illustrates an eye box;
[0013] FIG. 8 illustrates a display image processing environment;
[0014] FIG. 9 illustrates a computing device;
[0015] FIG. 10 illustrates one or more processor and one or more tangible, non-transitory, computer-readable media;
[0016] In some cases, the same numbers are used throughout the disclosure and the figures to reference like components and features. In some cases, numbers in the 100 series refer to features originally found in FIG. 1; numbers in the 200 series refer to features originally found in FIG. 2; and so on.
DESCRIPTION OF THE EMBODIMENTS
[0017] Some embodiments relate to three dimensional (3D) display. Some embodiments relate to 3D display with eye tracking (and/or with pupil tracking). Some embodiments relate to a 3D display that solves convergence and accommodation issues.
[0018] In three dimensional displays, a user may not be able to converge and focus (or accommodate) to the distance of the subject. This can be referred to as a vergence-accommodation conflict that can occur in 3D displays, and can also be referred to as a convergence-accommodation conflict. This conflict relates to eye focus and convergence issues, and can cause eye fatigue, dizziness, nausea, etc., particularly after extended use. Tensor displays can sometimes solve convergence and accommodation (focus) problems, but the efficiency of such a display can be very low. These displays can suffer from diffraction, Moire, etc., and can require a large amount of computation for optimization purposes. Volumetric displays can be bulky, and often require moving mechanical parts. Many volumetric displays also do not support occlusion, and can suffer from reduced visual quality such as being unable to render color images.
[0019] In some embodiments, a three dimensional display system can be implemented that is bright, presents full color images, and allows for correct occlusion. In some embodiments, a three dimensional display can be compact but still have a large depth field.
[0020] FIG. 1 illustrates an environment 100 (for example, a “real world” environment) including a user 102 (or viewer 102). The user 102 has eyes 104. The user’s eyes 104 look out toward an object 106 (for example, a real world object 106) along lines of vision illustrated by dotted lines 110 in FIG. 1. Dotted line 112 illustrates a focus line ending at a focus point at object 106. Dotted lines 110 end at a convergence point that is also at object 106. In some embodiments, environment 100 illustrates real three dimensional (3D) vision in physical space. The convergent point and the focus point in FIG. 1 are on the same depth plane. That is, the convergent point and the focus point in the real world environment 100 is the same (for example, at a real world object 106).
[0021] FIG. 2 illustrates an environment 200 (for example, a three dimensional display environment) including a user 202 (or viewer 202). The user 202 has eyes 204. The user’s eyes 204 look out toward an apparent location of a three dimensional (3D) displayed object 206 displayed on a three dimensional (3D) display screen 208 along lines of vision illustrated by dotted lines 210 in FIG. 2. Dotted line 212 illustrates a focus line ending at a three dimensional (3D) focus point (for example, a focus or accommodation point 214) at 3D display screen 208. Dotted lines 210 end at a convergence point that is at the apparent location of the displayed 3D object 206. In some embodiments, environment 200 illustrates three dimensional (3D) vision by a user 202 viewing an apparent object 206 being displayed on a 3D display screen 208. In some embodiments, the eyes 204 of the user 202 are forced to decouple the focus point on the 3D display screen 208 from the convergence point at the apparent location of the 3D object 206. This is known as vergence-accommodation conflict, convergence-accommodation conflict, and/or a convergence and accommodation conflict problem, for example.
[0022] In real world environments such as, for example, environment 100 of FIG. 1, when a human user is observing a particular subject, for example, where the eyes of the user both converge and focus (or accommodate) to the distance of the subject (for example, real world object 106). However, in many stereo three dimensional display environments such as, for example, environment 200 of FIG. 2, a user is not able to converge and focus (or accommodate) to the distance of the apparent location of the subject (for example, to the apparent location 206 of the three dimensionally displayed object).
[0023] In some three dimensional (3D) display systems, the user’s eyes must accommodate to a single focal plane (for example, the focal plane of 3D display screen 208) in order to see a scene in focus. In the case of 3D video such as 3D television (TV) or a 3D movie, for example, the focal plane is the physical display screen itself. However, the user’s eyes may converge to one or more apparent locations of one or more 3D objects being displayed. These apparent locations can be in front of and/or behind the screen. The distance from the user’s eyes to the display screen and the distance from the user’s eyes to the apparent location(s) of the 3D object(s) appearing in front of and/or behind the screen will not match in many situations. This mismatch of distance from the eyes to the focus point (or accommodation point) at the display screen and the distance from the eyes to the 3D convergence point(s) at the apparent location(s) of displayed 3D objects can be referred to as the convergence-accommodation conflict (or the vergence-accommodation conflict, or the convergence and accommodation conflict problem). As a result of this conflict, the user may experience headaches, fatigue, eyestrain, etc. This problem may cause health implications, particularly among children whose visual systems are still developing.
[0024] FIG. 3 illustrates a three dimensional (3D) display system viewing environment 300. Environment 300 includes a user 302 (or viewer 302) of a display system. The user 302 has eyes including pupils 304. The display system viewing environment 300 includes a display 312 to be viewed by the user 302. In some embodiments, display 312 can be any type of display. In some embodiments, display 312 can be and/or can include a display screen and/or a display panel. In some embodiments, display 312 can be a display, a display screen, and/or a display panel with any pixel density. In some embodiments, display 312 can be a high pixel density display, a high pixel per inch or high PPI display, and/or a 4K display. In some embodiments, display 312 is a display having a pixel density higher than 250 pixels per inch. In some embodiments, display 312 is a display with as high of a pixel density as possible. In some embodiments, display 312 can be a mobile phone screen or a tablet screen, among others. In some embodiments, display 312 can be a liquid crystal display, an LCD display, a liquid crystal display screen, an LCD display screen, a liquid crystal display panel, and/or an LCD display panel, etc.
[0025] In some embodiments, a display backlight 314 may be provided behind the display 312. A micro lens array 316 (for example, a long focal length micro lens array and/or a long focal length micro lens array with an F number larger than 8) is provided in front of the display 312 between the display 312 and the eyes of the user 302. In some embodiments, micro lens array 316 is a long focal length micro lens array with high focal length. For example, in some embodiments, micro lens array 316 is a long focal length micro lens array with high focal length with an F number between 8 and 30. In some embodiments, micro lens array 316 has a high focal length, depending on viewing distance and eye box size (or viewing area size), with an F number varying between 8 and 30. A pupil tracking device 318 can be used to track the pupils 304 of the user 302, and send any result(s) to a computing device 322 and a light field processing unit 324. In some embodiments, for example, pupil tracking device 318 can be a real-time 3D pupil tracking system. Display 312 is used to display apparent locations of three dimensional objects 320, which can appear to user 302 to be at the display 312 (for example, at a plane of the display 312), in front of the display 312 (between the display 312 and the user 302), and/or behind the display 312.
[0026] Computing device 322 can include, for example, a graphics engine. The computing device 322 can render color images and/or color plus depth images (for example, can render any color components such as red, green, blue color components with or without depth, including for example, RGB or RBG-D images) according to the user’s left and/or right pupil position, and send the rendered images to the light field processing unit 324. It is noted that in some embodiments, the images can be captured rather than rendered by computing device 322. In some embodiments, computing device 322 can capture or render stereo color plus depth images or light field images. The light field processing unit 324 can use pupil location information from the pupil tracking device 318 to convert the images received from the computing device 322 to stereo integral imagery using, for example, screen space ray tracing. Although screen space ray tracing is described herein, there are many different ways that the images may be converted. For example, rendering and post processing can be implemented in many different ways according to some embodiments. Many post processing techniques other than screen space ray tracing may be implemented according to some embodiments. The light field processing unit 324 can provide a light field image stream to the display screen 312 for display. In some embodiments, the backlight 314 (for example, a directional backlight) can steer light to corresponding pupil positions.
[0027] In some embodiments, the display system illustrated in FIG. 3 is a flexible light steering apparatus enabling a plurality of applications. Some embodiments implement single-viewer glasses-free three dimensional (3D) display that does not suffer from a convergence and accommodation conflict problem. In some embodiments, such display is compact, lightweight, and computationally and energy efficient relative to other displays such as, for example, brute force integral displays requiring dozens of gigapixels, a tensor display, which may be constrained by diffraction limitations making generation of sufficient density of view difficult in order to support accommodation, or bulky and impractical volumetric displays. In some embodiments, a directional backlight apparatus can be implemented for further benefits.
[0028] In some embodiments, the light steering properties of display system in FIG. 3 can be used to generate a correct light field for light rays that pass through the viewer’s eye pupils. Generating light field directed to eye pupil location can allow using currently available commodity displays to create 3D images with light rays with high enough density to produce correct accommodation (or focus) and convergence cues.
[0029] In some embodiments, extremely high view densities can be achieved within a small eye box. The position of the small eye box can be aligned with the viewer’s pupil position (for example, in response to a pupil tracking device such as pupil tracking device 318). The size of the small eye box can correspond to a typical human eye pupil size range. High view density can be achieved within a small eye box by placing a micro lens array (MLA) (for example, such as a long focal length micro lens array and/or micro lens array 316) in front of a display (for example, such as a high pixel density display and/or display 312), with a specific space in between the micro lens array and the display. The location of the eye box can be changed by shifting the image to be displayed on the display in response to the user tracking apparatus (for example, in response to a pupil tracking device such as pupil tracking device 318).
[0030] In some embodiments, a rendering process (for example, a rendering process implemented by computing device 322) is dependent on positions of the viewer’s eyes (for example, dependent on positions of pupils 304 of user 302 tracked by pupil tracking device 318). In some embodiments, a capturing process (for example, a capturing process implemented by computing device 322) is dependent on positions of the viewer’s eyes (for example, dependent on positions of pupils 304 of user 302 tracked by pupil tracking device 318). In some embodiments, a real time 3D tracking system (for example, pupil tracking device 318) can be used to track a viewer’s pupil positions. The tracked pupil positions can be used to position capturing or rendering camera projection centers, and/or to digitally fine-tune eye box alignment.
[0031] Some embodiments relate to glasses-free 3D display using an integral imaging system, a 3D pupil tracking device, and a light-field processing unit that can deliver view density high enough for both left and right eyes of a user to overcome vergence-accommodation conflict or convergence-accommodation conflict (that is, convergence and accommodation conflict issues).
[0032] In some embodiments, a 3D pupil tracking system (such as pupil tracking device 318) tracks the pupil position of a viewer of a display, and sends the result to a computer (for example, such as computing device 322) and to a light field processing unit (for example, such as light field processing unit 324). The computing device captures and/or renders stereo images (for example, RGB and/or RGB-D images) according to the viewer’s left and/or right pupil position. The light field processing unit uses pupil location information to convert the captured and/or rendered images to integral imagery using, for example, screen space ray tracing or any other view interpolation/synthesis technique. The image is then displayed on a high resolution display screen (for example, on display 312). At the same time, in some embodiments, a directional backlight (for example, such as backlight 314) steers light to corresponding pupil positions.
[0033] In some embodiments, a micro lens array (MLA) such as, for example, micro lens array 316, is placed in front of a high pixel density display module such as, for example, display 312. The display module and the micro lens array are spaced at the focal length of the micro lens array so that the rays from each pixel on the display pass through each micro lens on the micro lens array to form a collimated beam. Given the distance d.sub.z between the micro lens array and a user eye viewpoint in front of the micro lens array, a largest eye box occurs when the integral image pitch size w.sub.p is:
w p = ( d z + f ) p l d z p p EQUATION 1 ##EQU00001##
[0034] Where f is the focal length of the micro lens array, p.sub.l is the lens pitch of the micro lens array, and p.sub.p is the pixel pitch of the display. The eye box size w.sub.e can be calculated using the following:
w e = d z w p p p f EQUATION 2 ##EQU00002##
[0035] When the viewer’s eyes are perfectly located in the center of the eye box, they are able to observe a correct light field image. The rays from one pixel travel through the micro lens above that pixel, and also travel through neighboring micro lenses, forming replica eye boxes. When the viewer’s eyes move out of the primary eye box, they will perceive a change in the light field image, and then enter a replica eye box.
[0036] In some embodiments illustrated in FIG. 3 and/or other embodiments, if you take a display with a certain image pattern displayed thereon, and place a lens array in front of the display, a user can see a full three dimensional image. This can be accomplished without the user wearing glasses, but merely looking at an area of the display and lens array. Depending on parameters of the display and the lens array, the size of the area that the user will see the 3D image may vary. The area where the user sees this 3D image may be referred to as a primary viewing zone (viewing zone as used herein is also referred to as an eye box). However, if the user moves outside a primary viewing zone (primary eye box), the user may also see the same or similar image in one or more secondary viewing zones (secondary eye boxes) that may repeat through various user viewing areas (eye boxes). There may be a number of secondary viewing zones, the number of secondary viewing zones depending on what the lens array may allow the user to see.
[0037] The resolution of the image (and/or 3D image quality), focus capability of the image, etc. can depend on an overall number of pixels beamed into a viewing zone. The smaller the viewing zone, the denser the light field. The wider the viewing zone, the sparser the light field. With sparser light fields, focus will degrade and 3D image quality will gradually become unacceptable
[0038] In an implementation in which a lens array is placed in front of a display and the viewing zone is made small (for example, slightly larger than the size of a viewer’s pupil), a very dense light field can be created. However, one pupil may see the image very well, but the other pupil may not see the image well at all (for example, the other pupil may see the same image or a corrupted image because it is between viewing zones). Additionally, if a user shifts their eye, their eye may leave one viewing zone and enter another viewing zone. If the viewing zone (eye box) is divided into two portions (for example, one portion for left eye and another portion for right eye), the left eye may see one repetition of a left portion of the viewing zone, and the right eye may see another repetition of a right portion of the viewing zone, then the user can view a stereo dense light field to view a 3D image with the user’s two eyes. Another approach is to use one eye box per eye. However, if a regular backlight is used where light goes in multiple directions, all eye boxes (viewing zones) will be lit up with all repetitions of the viewing zones.
[0039] In some embodiments, a directional backlight can be used to emit light all in a certain direction. In this manner, directional backlight control can be used to light up only one viewing zone at a particular time, and repetitions of the viewing zone are not visible. For example, in some embodiments, a directional backlight emits light that is only directed toward one eye box (or viewing zone) in the area of an eye (and/or a pupil) of a user at one particular time. In some embodiments, pupil position is tracked, so the directional backlight can be controlled to send light to a particular tracked pupil at a particular time. In some embodiments, particular light emitting diodes (LEDs) of the backlight can be turned on and particular other LEDs of the backlight can be turned off to direct the controlled light emitted from the backlight to emit the light in the area of the viewer’s eye (and/or pupil). In this manner, direction of the emitted light of the directional backlight can be changed according to eye movement (and/or pupil movement). Such directional backlight can be time multiplexed (also referred to herein as temporal multiplexed) between eyes of a viewer. In some embodiments, eyes (and/or pupils) of more than one user can be time multiplexed according to some embodiments. In some embodiments, for one particular user, the time multiplexing occurs at a fast frequency between eyes of a user (and/or pupils of a user) so that the image appears continuous to the user. For example, in some embodiments, the frequency can be 120 Hz for two eyes of a user (60 Hz for each eye). In some embodiments, the frequency is greater than 120 Hz (greater than 60 Hz for each eye).
[0040] In some embodiments, as described above, a high view density light field concentrated around one or more viewer’s eye pupils is generated by a system using a long focal length micro lens array and a directional backlight. Such a system directs a light field into a small eye box (for example, in some embodiments, a small 10 mm by 10 mm eye box) with many views (for example, 20 by 20 views). In some embodiments, the eye box position is changed using a controllable directional backlight system. In this manner, at any particular moment the directional backlight can steer light into only one eye. Time multiplexing can be used to deliver required light field into both eyes, by changing the eye box position and displayed content at speeds exceeding a human eye flicker threshold.
[0041] FIG. 4 illustrates temporal multiplexing 400 (and/or time multiplexing 400). In some embodiments, FIG. 4 illustrates temporal multiplexing (and/or time multiplexing) with directional backlight control. FIG. 4 illustrates a user 402 with left and right eyes at a first timeframe (frame 1), a second timeframe (frame 2), a third timeframe (frame 3), and a fourth timeframe (frame 4), for example. In some embodiments, the timeframes are at a display rate faster than a human can recognize. In some examples, the timeframes are at a display rate of 120 Hz, for example.
[0042] FIG. 4 also illustrates a display 412 (for example, a display screen and/or display panel), a backlight 414 (for example, a directional backlight that can be directionally controlled), and a micro lens array 416. In some embodiments, display 412, backlight 414, and/or micro lens array 416 can be similar to and/or the same as display 312, backlight 314, and/or micro lens array 316 of FIG. 3. At frame 1, a high view density light field 432L is concentrated from backlight 414, display 412 and micro lens array 416 to a left eye (and/or a left pupil) of user 402. At frame 2, a high view density light field 432R is concentrated from backlight 414, display 412 and micro lens array 416 to a right eye (and/or a right pupil) of user 402. At frame 3, a high view density light field 432L is concentrated from backlight 414, display 412 and micro lens array 416 to the left eye (and/or the left pupil) of user 402. At frame 4, a high view density light field 432R is concentrated from backlight 414, display 412 and micro lens array 416 to the right eye (and/or the right pupil) of user 402. In this manner, display backlight 414 can be a directional backlight that can steer light alternating between the left and right eye of the user 402. This steering of light can be based, for example, on tracked eye location information (for example, tracked pupil location information). The tracked eye location information can be tracked eye location information from an eye tracking device such as, for example, pupil tacking device 318. In some embodiments, the display backlight 414 can steer light alternating between the left and right eye based on the tracked eye location information (and/or based on the tracked pupil location information) at a refresh rate that is higher than a human perceivable refresh rate (for example, at 120 Hz). For example, the frames in FIG. 4 can be alternated at a refresh rate that is higher than a human perceivable refresh rate (such as a refresh rate of 120 Hz).
[0043] In some embodiments, a high view density light field (for example, high view density light field 432L and/or high view density light field 432R) can be concentrated around one or more viewer’s eye pupils (for example, can be concentrated around eyes and/or eye pupils of viewer 402). The high view light field(s) can be generated by a system using a long focal length micro lens array (for example, micro lens array 416) and a directional backlight (for example, backlight 414). Such a system directs a light field (for example, light field 432L and/or light field 432R) into a small eye box (for example, in some embodiments, a small 10 mm by 10 mm eye box) with many views (for example, 20 by 20 views). In some embodiments, the eye box position is changed using a controllable directional backlight system (for example, including backlight 414). In this manner, at any particular moment the directional backlight can steer light into only one eye as illustrated, for example, in FIG. 4. Time multiplexing can be used to deliver required light field into both eyes, by changing the eye box position and displayed content at speeds exceeding a human eye flicker threshold (for example, at 120 Hz).
[0044] FIG. 4 has been described herein as time multiplexing between two eyes of a single user. However, in some embodiments, the time multiplexing illustrated in FIG. 4 or described herein is not limited to a single user. In some embodiments, time multiplexing of directional backlight can be implemented between more than one user (for example, between eyes of multiple users at a high enough refresh rate so that it is not apparent to any one user). Steering of directional backlight is not limited to one user. If display frequency is high enough, two or more users can be addressed simultaneously. For example, in some embodiments, in frame 1 a first eye of a first user receives directional backlight, in frame 2 a first eye of a second user receives directional backlight, in frame 3 a second eye of the first user receives directional backlight, and in frame 4 a second eye of the second user receives directional backlight. In other embodiments, other numbers of users and order of eyes receiving directional backlight at particular times can be implemented. In some embodiments, a sequential system is implemented. For example, some embodiments relate to a time multiplexed system in which light can be steered (for example, from a directional backlight) to individual positions or spaces near a display in a time multiplexed manner.
[0045] In some embodiments, with controlled backlight or without controlled backlight, the integral image displayed on the display can define the size and position of the eye box. By shifting the integral image displayed on the display, the eye box center can be shifted to align with either the left or the right pupil position.
[0046] FIG. 5 illustrates an eye box 500 that is subdivided into left (L) and right (R) parts. Eye box 500 includes left (L) and right (R) center eye box 502. The other eye boxes 500 other than center eye boxes 502 are repetitions of the center eye box 502. In some embodiments, eye box 500 is referred to as a divided eye box or a subdivided eye box, since it is divided into left (L) and right (R) portions. In some embodiments, eye box 500 can be used in conjunction with the system of FIG. 3 and/or of FIG. 4 in order to deliver a required light field into the eyes (for example, into the pupils) of one or more user.
[0047] FIG. 6A illustrates an eye box 600A from a front view. FIG. 6B illustrates a combination of a display 612B and a micro lens array 616B from a side view. In some embodiments, FIG. 6A illustrates good viewing area 602A and bad viewing areas 604A from a front view. In some embodiments, the side view 600B is a view from the side of front view 600A. In some embodiments, micro lens array 616B is a long focal length micro lens array. In some embodiments, display 612B is similar to and/or the same as display 312 of FIG. 3. In some embodiments, micro lens array 616B is similar to and/or the same as micro lens array 316 of FIG. 3. In some embodiments, eye box 600A can be used in conjunction with the system of FIG. 3 and/or of FIG. 4 in order to deliver a required light field into the eyes (for example, into the pupils) of one or more user.
[0048] In some embodiments, a high view density light field is generated in a small eye box using a long focal length micro lens array (for example, micro lens array 616B) and a divided eye box (for example, divided eye box 500 and/or divided eye box 600A).
[0049] In some embodiments, by dividing the eye box into left (L) and right (R) parts, the eye box can be arranged in a manner such that the left part of the eye box will cover the left eye, and a repetition of the right part of the eye box will cover the right eye. In this manner, the viewer will see a correct light field when at a correct viewing distance. In some embodiments, when a user’s IPD is close to an integral multiple of the eye box size, the user will not be able to perceive a correct light field image since both eyes will see the same sub eye box (for example both eyes will see a right eye box or both eyes will see a left eye box). In some embodiments, this problem can be solved using micro lens array optics that can change focal lengths and spacing between micro lens array and screen, or by changing the viewing distance which determines the eye box size.
[0050] In some embodiments, a compact and controllable directional backlight system (for example such as backlight 314 of FIG. 3 and/or backlight 414 of FIG. 4) is used to overcome limitations of a divided eye box system. For example, a divided eye box system can produce a correct light field at certain fixed viewing distances when an IPD of a viewer (such as a horizontal IPD of a viewer) is an odd multiple of half the eye box width. As illustrated in FIG. 3, for example, when IPD=5*W.sub.e/2, an L portion of the eye box lines up on the left eye of the viewer and an R portion of the eye box lines up on the right eye of the viewer. However, adjustment and/or use of a backlight may be necessary for a viewer with IPD=6*W.sub.e/2, where an L portion of the eye box lines up on the left and an L portion of the eye box also lines up on the right, for example. Similar arrangements can occur with eye box 600A illustrated in FIG. 6A.
[0051] In some embodiments, the eye box shape is not required to be square. In some embodiments, however, the eye box is in a shape that can be tiled in a uniform grip. If the viewer’s head is rotated with respect to the display screen, the viewer’s left and right eyes may have different apparent heights relative to the display. Therefore, in some embodiments, left and right portions of the eye box can be moved up or down.
[0052] FIG. 7 illustrates an eye box 700. In some embodiments, eye box 700 includes first eye box portions 702 (for example, left eye box parts 702) and second eye box portions 704 (for example, right eye box parts 704). As discussed above, if the viewer’s head is rotated with respect to the display screen, for example, the viewer’s left and right eyes may have different apparent heights relative to the display. Therefore, as illustrated in FIG. 7, portions 702 (for example, left portions 702) of the eye box 700 can be moved up or down, and/or portions 704 (for example, right portions 704) can be moved up or down so that portions 702 and 604 are at different heights. In some embodiments, eye box 700 can be used in conjunction with the system of FIG. 3 and/or of FIG. 4 in order to deliver a required light field into the eyes (for example, into the pupils) of one or more user.
[0053] Some portions of eye boxes have been illustrated herein as being rectangular in shape. For example, L and R eye box portions in FIGS. 5 and 7 are illustrated as being rectangular. However, in some embodiments, this may cause less than half of the light rays to be utilized since a rectangular shape does not match up well with the shape of a pupil. However, in some embodiments, a micro lens array can be designed with a different micro lens aspect ratio. For example, in some embodiments, a micro lens array design can be used with a micro lens aspect ratio equal to 2, resulting, for example, in an arrangement where each subdivided (or divided) eye box can be of a square shape.
[0054] In some embodiments, in order to generate an image to be displayed on the 3D display, capturing and/or rendering based on the pupil position of a user (viewer) can be performed by a computing device (for example, using graphics hardware) to generate intermedia data that encapsulate the geometry and texture information of the scene (such as, for example, RGB-D images). The data (such as RGB-D images) is then transmitted to a light field processing unit. The light field processing unit uses the real-time pupil position to calculate an optimal eye box size and an image offset needed to align the eye box center with pupil position. Then the light field processing unit can convert the image (such as the RGB-D image) to the final integral image. This can be implemented, for example, using screen-space ray tracing, or according to other techniques. In some embodiments, instead of using a graphic engine to generate the RGB-D images, captured RGB-D images can be transmitted to a light field processing unit to generate an image to be displayed on the 3D display.
[0055] Screen-space ray tracing is a very efficient post-processing technique for generating approximations of reflection, refraction, glossy reflection, ambient occlusion, and/or global illumination. This can be implemented at a much lower cost than some ray tracing techniques. In some embodiments, screen-space ray tracing is used to generate light field renderings from RGB-D data. In some embodiments, techniques other than screen-space ray tracing may be used (for example, according to some embodiments, any post processing technique may be used).
[0056] FIG. 8 illustrates display image processing in a three dimensional (3D) display environment 800. Environment 800 includes a display 812 (and/or a display screen 812, and/or a display panel 812) and a micro lens array 816. Display 812 can display three dimensional images to be viewed by a user or viewer. In some embodiments, display 812 can be the same as or similar to display 312, for example. In some embodiments, display 812 can be any type of display, any type of display screen, and/or any type of display panel. In some embodiments, display 812 can be a mobile phone screen or a tablet screen, among others. In some embodiments, a display backlight (not shown in FIG. 8) may be provided behind the display 812. Micro lens array 816 can be a long focal length micro lens array, and is provided in front of the display 812 between the display 812 and the eyes of a user. Display 812 is used to display apparent locations of three dimensional (3D) objects 820, which can appear to a user to be at the display 812 (for example, at a plane of the display 812, in front of the display 812 (between the display 812 and the user, and/or behind the display 812. In FIG. 8, the objects 820 are displayed at apparent locations behind the display 812 (above the display 812 in FIG. 8). A capturing and/or rendering camera 832 is used to capture and/or render images through a near clip plane 842, micro lens array 816, display 812, and a far clip plane 844.
[0057] In some embodiments, a scene including objects 820 has been captured and/or rendered to a canvas at the near clip plane 842. Since the scene has been captured and/or rendered, color and depth at any point is available. For a pixel P on the display 812, the location of the pixel P and the optical center of the lenslet (or lens within the micro lens array) in front of the pixel P defines a ray R in space. The color of pixel P can be defined by the color of the intersecting point of ray R with the three dimensional (3D) scene (for example, at point C). A simple one dimensional (1D) search on the canvas of the near clip plane 842 can be used to find the intersecting point C using the following steps:
[0058] 1. Compute the intersection of ray R with both the near clip plane 842 and the far clip plane 844. In the case of FIG. 8, these two points are point A at the near clip plane 842 and point B at the far clip plane 844.
[0059] 2. Project point B onto the near clip plane 842 to get point B’. This projection can be performed by drawing a line between point B and the viewpoint of the capturing and/or rendering camera 832.
[0060] 3. Interpolate from point A to point B’. This interpolation can occur in the two dimensional (2D) plane represented by near clip plane 842. Each pixel in the sequence can be efficiently computed using the Bresenham interpolation algorithm (or Bresenham’s line algorithm, or digital differential analyzer algorithm, or DDA line algorithm), for example. In some embodiments, Bresenham’s line algorithm (or other algorithm) can be used to determine points of an n-dimensional raster that should be selected in order to form a close approximation to a straight line between two points. In some embodiments, any of the Bresenham family of algorithms extending or modifying Bresenham’s original algorithm may be used. See, for example, https://en.wikipedia.org/wiki/Bresenham%27s_line_algorithm.
[0061] 4. For each point C’ generated by the interpolation, the depth is read from a precomputed two dimensional (2D) canvas. The depth of the corresponding 3D point C on ray R is also computed. Since the 2D line segment from point A to point B’ is a 2D projection of the 3D line from point A to point B, for any point C’ a corresponding point C can be directly computed. Points C’ are repeatedly generated and tested until the depth of the 3D point C is larger than the depth read from the precomputed 2D canvas, or the 3D point is outside the frustrum (that is, past the far clipping plane 844). That test can be used to determine whether the correct point C in the virtual scene has been found, or if there is no virtual object associated with that pixel. If there is no virtual object associated with that pixel, then the color of C can be set to a background color.
[0062] 5. Set the color of the pixel P to the color of pixel C and stop the process.
[0063] In some embodiments, techniques described herein can be used to build a computational display that is practical for users. In some embodiments, computational displays can be used to display 3D content without causing eyestrain or requiring 3D glasses. In some embodiments, displays described and/or illustrated herein can be included in all form factors (for example, all displays including wearables, phones, tablets, laptops, desktops, and/or far-eye displays).
[0064] In some embodiments, the image to be displayed on the 3D display can be rendered directly with ray tracing, and/or with any other techniques. With tracked pupil location and viewing distance, the eye box size and position can be computed using Equation 1 and Equation 2. In some embodiments, each single pixel on the display will only be visible from one micro lens in any given eye box. Tracing the ray that passes though the pixel center and the mirco lens optical center in the virtual scene will return the pixel color for that particular pixel in the final image.
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