Glasses-free stereoscopic image display device with split backlight

Abstract

To provide an autostereoscopic display device that solves the problem of the distance required between a light source and a concave mirror, and the problem of crosstalk and afterimages that occur when the switching speed of a display panel cannot keep up.SOLUTION: The autostereoscopic image display device with partitioning backlight is suitable for use in combination with an imaging semi-reflective mirror, a display screen includes a main display module and a light shielding module, a light incident side or a light emitting side of the main display module overlaps with the light shielding module, the display screen is divided into a plurality of blocks and is switched in a time division manner, and is correspondingly switched in combination with a backlight source to achieve an image split region display effect, to resolve an afterimage and crosstalk caused by an insufficient response speed of the main display module when parallax images of left and right eyes are switched at a high speed, and to adjust brightness of image observation by changing a display time of a display block.SELECTED DRAWING: Figure 16A

Description

Technical Field

[0001] The present invention relates to a naked-eye stereoscopic image display device, and more particularly, to a naked-eye stereoscopic image display device provided with a segmented backlight.

Background Art

[0002] As shown in FIGS. 1A and 1B, a conventional head-up display (HUD) emits a backlight beam using a backlight light source 01. The backlight beam passes through a display panel 03 to form an image beam, and the image beam is further reflected by an imaging concave mirror 5. The imaging concave mirror 5 is a concave reflecting mirror. The image on the display panel 03 forms an image virtual image corresponding to the rear of the imaging concave mirror 5, and the backlight light source 01 forms a real image of the backlight light source in the optical path in front of the imaging concave mirror 5.

[0003] The imaging semi-reflecting mirror is used to reflect a part of the image beam from the imaging concave mirror to the observer's eyes, and at the same time, transmit a part of the light from the scene in front of the observer to the observer's eyes. The imaging semi-reflecting mirror may be, for example, a front glass WS as shown in FIG. 1A or a combiner C as shown in FIG. 1B. After the image virtual image behind the imaging concave mirror 5 is reflected by the imaging semi-reflecting mirror (front glass or combiner), an image virtual image G_im is formed on the side of the imaging semi-reflecting mirror away from the observer. The real image of the backlight light source in front of the imaging concave mirror 5 is reflected by the imaging semi-reflecting mirror and then forms a real image of the backlight light source in focus on the side of the imaging semi-reflecting mirror close to the observer. This is the eye box EB.

[0004] When the observer's eyes are located at the position of the eye box, that is, at the actual focus of the light emitted from the backlight light source, the observer can see the brightest and clearest image virtual image.

[0005] In order for the backlight source to form a real image of the backlight source in front of the imaging concave mirror, the distance between the backlight source and the imaging concave mirror must be longer than the focal length of the imaging concave mirror, which is even more difficult in a car dashboard where space is limited.

[0006] As shown in Figure 1C, a conventional directional backlight autostereoscopic head-up display device uses a directional backlight array as the backlight source 01 and combines it with a high-speed response display panel 03. The directional backlight array 01 projects a directional backlight beam B onto the display panel 03. The display panel 03 quickly switches between displaying the left-eye disparity image and the right-eye disparity image, and the directional backlight beam B passes through the display panel 03 to form a directional image beam D containing image information. The directional image beam D is reflected by the imaging concave mirror 5 and the imaging semi-reflecting mirror 7, forming a real image of the backlight source on the side of the imaging semi-reflecting mirror 7 facing the observer, i.e., forming an eyebox array EBA, and forming a real image of the virtual image G_im on the side of the imaging semi-reflecting mirror 7 away from the observer. The observer's left and right eyes can see the virtual disparity images G_im for the left and right eyes, respectively, within the region of the eyebox array EBA. The image seen by the observer's right eye is the right-eye parallax virtual image, and the image seen by the left eye is the left-eye parallax virtual image. The brain integrates the left-eye parallax virtual image and the right-eye parallax virtual image to form a three-dimensional image.

[0007] Light emitted or reflected from the backlight light source array is reflected by the imaging concave mirror 5 to form a real image of the backlight light source in front of the imaging concave mirror 5, and the real image of the backlight light source is reflected by the imaging semi-reflector 7 and projected onto the observer's eye box array EBA. The left eye parallax image on the display panel 03 is reflected by the imaging concave mirror 5 to form a first left and right eye parallax image virtual image located behind the imaging concave mirror 5. Next, the left and right eye parallax images reflected by the imaging semi-reflector 7 become a second left and right eye parallax image virtual image G_im located away from the observer on the imaging semi-reflector 7. The eye-tracking module 6 detects the relative position information of the observer's left and right eyes and the eye-tracking module. The control calculation module 61 receives detection information from the eye-tracking module 6 and, through identification, calculation, table lookup, or inference, obtains the left eye position E_L and right eye position E_R in the observer's space. Next, it obtains the corresponding left eye sub-eyebox EB_L and right eye sub-eyebox EB_R in the eyebox array EBA from the left and right eye positions, and obtains the left eye backlight source Led_L and right eye backlight source Led_R from the left and right eye sub-eyeboxes. When the display panel 03 displays the left eye disparity image, the left eye backlight source Led_L lights up, and when it displays the right eye disparity image, the right eye backlight source Led_R lights up. Since the switching time between the two images is shorter than the visual duration of the human eye, the left and right eyes can continue to view the left disparity image and the right disparity image, respectively.

[0008] The time interval between the display panel 03 switching and the display of the left-eye parallax image and the right-eye parallax image is very short, but the liquid crystal requires time to respond. If a part of the liquid crystal cannot switch in time, the other eye will see the area that has not been switched (a part of the previous image) or the area that is being switched, causing crosstalk and afterimages. [Overview of the project] [Problems that the invention aims to solve]

[0009] In summary, achieving bright, clear stereoscopic images for the naked eye requires resolving the issue of the distance between the backlight source and the image-forming concave mirror, as well as resolving the crosstalk and afterimage problems caused by the display panel's inability to keep up with the switching speed. [Means for solving the problem]

[0010] Based on the above objectives, the present invention provides a glasses-free stereoscopic image display device.

[0011] The naked-eye stereoscopic image display device is suitable for use in combination with an imaging semi-reflecting mirror. A backlight module that emits a backlight beam, including a backlight light source array composed of multiple backlight light sources, An off-axis dual mirror module includes a first mirror and a second curved mirror positioned with their optical axes offset from each other, wherein the first mirror and the second curved mirror sequentially reflect the backlight beam to form a directional backlight beam, The system includes a main display module and a light-shielding module superimposed on each other, the main display module alternately displays left-eye parallax images and right-eye parallax images, and the display forms an image beam after a directional backlight beam has passed through it. A concave imaging mirror that reflects the image beam, An eye-tracking module that detects relative position information between the left and right eyes, A control calculation module that acquires detection information from an eye-tracking module and obtains the left and right eye positions in the observer's space, Includes.

[0012] In the naked-eye stereoscopic image display device of the present invention, an off-axis dual mirror module is used to form a virtual image of the backlight source array on the backlight source array. The equivalent distance between the virtual image of the backlight source array and the imaging concave mirror is greater than the focal length of the imaging concave mirror, and the backlight beam corresponding to the virtual image of the backlight source array (or the backlight beam considered to have been emitted from the position of the virtual image of the backlight source array) is reflected by the imaging concave mirror and the imaging semi-reflector, and then projected and focused onto the backlight focusing surface on the side of the imaging semi-reflector 7 closer to the observer, forming a real image of the backlight source array. Each backlight source forms an independent small eye box, and all the small eye boxes constitute the real image of the backlight source array, thereby defining an eye box array, the eye box array containing multiple eye boxes.

[0013] Furthermore, the equivalent distance between the main display module and the imaging concave mirror is smaller than the focal length of the imaging concave mirror, and based on the left-eye parallax image and the right-eye parallax image, virtual images of the left-eye and right-eye parallax are formed on the side of the imaging semi-reflecting mirror away from the eyebox array, respectively.

[0014] Furthermore, the polarizer closest to the light-receiving side of the display is a reflective polarizer, and there is only one polarizer between the liquid crystal layer of the main display module and the liquid crystal layer of the light-shielding module.

[0015] Furthermore, the main display module defines multiple display blocks, and the shading module defines multiple switching blocks, each switching block corresponding to a display block. When the main display module displays an image, at least one switching block is selected in a time-division manner to control the display block to project the image beam in a time-division manner, while the remaining switching blocks shade any remaining blocks of the main display module that are still being switched or have not yet been switched.

[0016] Furthermore, when the main display module displays the image for one eye, at least one switching block is selected in a time-division manner to control the display block so that it projects the image beam in a time-division manner, while the remaining switching blocks occlude the display block for the image of the other eye.

[0017] Furthermore, by combining each display block with a backlight source at the same or different positions, it is possible to define more small eyeboxes, including the original eyebox array, outside the eyebox array space on both sides of the backlight focusing surface, thereby defining a wider extended eyebox array. This allows for viewing a complete left-eye parallax virtual image or a right-eye parallax virtual image even at spatial positions far from the backlight focusing surface.

[0018] Furthermore, by switching between small eyeboxes at different positions in the eyebox array or extended eyebox array, it is possible to accommodate the movement of the observer's eyes to different positions along the vertical, horizontal, and forward / backward directions.

[0019] Furthermore, the control calculation module acquires the left eye sub-eyebox and right eye sub-eyebox based on the left eye position, right eye position, and extended eyebox array, and then acquires the corresponding left eye matrix and right eye matrix according to the sub-eyebox-display block-backlight source matrix table. The left eye matrix and right eye matrix each include the corresponding display block, switching block, and backlight source. The display block, switching block, and backlight source are controlled to display the left eye disparity image and the right eye disparity image, respectively.

[0020] Furthermore, a corresponding small eyebox lights up depending on the position of the movement of the left or right eye. By switching between different small eyeboxes, it is possible to track the eye position and project an image, corresponding to the amount of eye displacement, which includes displacement in two or three dimensions.

[0021] In addition, the backlight module further includes a conical light cup array composed of conical light cups having different inclination angles, and the inclination angle of each conical light cup increases as it moves away from the center of the array.

[0022] In addition, the backlight module further includes a conical light cup array, a polarizing lens array, and a condenser lens array, which are arranged in order from the light emitting side of the backlight light source array.

[0023] In addition, the second curved mirror is a concave mirror, the first mirror is a concave mirror, a convex mirror, or a plane mirror, and the imaging position after being reflected by the first mirror in the backlight module is within the focal length of the second curved mirror.

[0024] In addition, the optical path from the backlight module to the first mirror and the optical path from the second curved mirror to the display module may intersect or not intersect.

[0025] In addition, the light incident side or the light emitting side of the main display module overlaps with the light shielding module.

[0026] In addition, the main display module and the light shielding module are adhered by an optical adhesive, and there is no polarizer between the optical adhesive and the liquid crystal layer of the main display module, or there is no polarizer between the optical adhesive and the liquid crystal layer of the light shielding module.

[0027] In addition, by adjusting the length of the lighting time of the backlight light source, which adjusts the length of the on-time of the switching block, the brightness of the observed left-eye parallax image virtual image and the right-eye parallax image virtual image can be controlled.

[0028] In addition, the liquid crystal switching speed of the main display module is slower than that of the light shielding module.

[0029] Furthermore, the observer's left-right (horizontal) or up-down (vertical) direction corresponds to one eye using 2n+1 adjacent small eye boxes. Here, n > 0 and n is a positive integer, and of the multiple small eye boxes, the central small eye box is aligned with the pupil, while the other 2n small eye boxes are located above and below or to the left and right of the central small eye box.

[0030] Furthermore, the main display module alternately displays the left-eye parallax image and the right-eye parallax image, and the switching interval time during which each display block projects image light to the same eye is shorter than 41.67 ms.

[0031] Furthermore, the imaging semi-reflecting mirror is a windshield or combiner, and is used to partially transmit light from the scene in front of it to the observer's eye while reflecting a portion of the image beam from the imaging concave mirror to the observer's eye. [Effects of the Invention]

[0032] This invention improves upon the problems faced by conventional glasses-free stereoscopic image display devices, eliminating afterimages and crosstalk, enhancing image brightness, uniformizing screen brightness, avoiding image flicker, and expanding the visible area, thereby realizing a glasses-free stereoscopic image display device that best meets the requirements of moving objects such as vehicles, ships, and aircraft. [Brief explanation of the drawing]

[0033] [Figure 1A] This is an explanatory diagram of a backlit head-up display device that combines a conventional imaging semi-reflecting mirror. [Figure 1B] This is an explanatory diagram of a backlit head-up display device that combines a conventional imaging semi-reflecting mirror. [Figure 1C] This is an explanatory diagram of a conventional directional backlit head-up display device for glasses-free 3D imaging. [Figure 2A] This is an explanatory diagram of an off-axis dual mirror module. [Figure 2B] This is an explanatory diagram of an off-axis dual mirror module. [Figure 2C] This is an explanatory diagram of an off-axis dual mirror module. [Figure 2D] This is an explanatory diagram of an off-axis dual mirror module. [Figure 3A] This is an explanatory diagram of a backlit display device that combines an off-axis dual mirror module. [Figure 3B] This diagram illustrates the diffusion angles of a backlight source beam through and without an off-axis dual mirror module. [Figure 4A] This is an explanatory diagram of a directional backlight array module. [Figure 4B] This is an explanatory diagram of a directional backlight array module. [Figure 4C] This is an explanatory diagram of a directional backlight array module. [Figure 4D] This is an explanatory diagram of a directional backlight array module. [Figure 5A] This is an explanatory diagram of a backlight light source array module with a lens. [Figure 5B] This is an explanatory diagram of a backlight light source array module with a lens. [Figure 5C] This is an explanatory diagram of a backlight light source array module with a lens. [Figure 6A] This is an explanatory diagram of a display device that uses a backlight light source array combined with an off-axis dual mirror module to form a real image. [Figure 6B] This is another explanatory diagram of a display device that uses a backlight light source array combined with an off-axis dual mirror module to form a real image. [Figure 7] This is an explanatory diagram of a glasses-free stereoscopic image display device. [Figure 8A] This is an explanatory diagram illustrating the correspondence between the eyebox array and the positions of the left and right eyes. [Figure 8B] This is an explanatory diagram illustrating the correspondence between the eyebox array and the positions of the left and right eyes. [Figure 8C] This is an explanatory diagram showing multiple small eye boxes corresponding to the position of one eye. [Figure 8D]This is an explanatory diagram showing multiple small eye boxes corresponding to the position of one eye. [Figure 9] This is an explanatory diagram illustrating the switching images of the main display module under ideal conditions. [Figure 10A] This is an explanatory diagram of the liquid crystal conversion time. [Figure 10B] This is an explanatory diagram of the pixel conversion state of an LCD display panel. [Figure 11A] This is an explanatory diagram of the main display module and the light-shielding module. [Figure 11B] This is an explanatory diagram showing the superposition of the main display module and the light-shielding module. [Figure 11C] This is an explanatory diagram of the response times of IPS LCDs and TN LCDs. [Figure 11D] This is an explanatory diagram showing the detailed structure of the overlapping main display module and light-shielding module. [Figure 11E] This is an explanatory diagram showing the detailed structure of the overlapping main display module and light-shielding module. [Figure 11F] This is an explanatory diagram showing the detailed structure of the overlapping main display module and light-shielding module. [Figure 11G] This is an explanatory diagram showing the detailed structure of the overlapping main display module and light-shielding module. [Figure 11H] This is an explanatory diagram showing the detailed structure of the overlapping main display module and light-shielding module. [Figure 11I] This is an explanatory diagram showing the detailed structure of the overlapping main display module and light-shielding module. [Figure 12A] This is an explanatory diagram of the pixel conversion cycle of the main display module. [Figure 12B] This is an explanatory diagram showing multiple blocks defined by the main display module and the light-shielding module. [Figure 13] This diagram illustrates the switching timing of multiple blocks in the main display module, light-shielding module, and backlight module. [Figure 14] This is an explanatory diagram for switching between the main display module, light-shielding module, and backlight module blocks. [Figure 15] This is an explanatory diagram showing images viewed by the left and right eyes at different times. [Figure 16A] This is an explanatory diagram illustrating the real image formation of the backlight module and the virtual image formation of the main display module. [Figure 16B] This diagram illustrates the real image formation in the divided regions of the backlight module and the virtual image formation in the divided regions of the main display module. [Figure 16C] This diagram illustrates the real image formation in the divided regions of the backlight module and the virtual image formation in the divided regions of the main display module. [Figure 17A] This is an explanatory diagram of the spatial light path for the combination of the first backlight source and each display block. [Figure 17B] This is an explanatory diagram of the spatial light path for the combination of the first backlight source and each display block. [Figure 17C] This is an explanatory diagram of the spatial light path for the combination of the first backlight source and each display block. [Figure 17D] This is an explanatory diagram showing the combination of the first backlight source and the divided regions of the main display module, and their intersection in the spatial optical path. [Figure 17E] This is an explanatory diagram showing the combination of the first backlight source and the divided regions of the main display module, and their intersection in the spatial optical path. [Figure 18A] This is an explanatory diagram of the spatial light path for the combination of the second backlight source and each display block. [Figure 18B] This is an explanatory diagram of the spatial light path for the combination of the second backlight source and each display block. [Figure 18C] This is an explanatory diagram of the spatial light path for the combination of the second backlight source and each display block. [Figure 18D] This is an explanatory diagram showing the combination of the second backlight source and the divided regions of the main display module, and their intersection in the spatial optical path. [Figure 18E] This is an explanatory diagram showing the combination of the second backlight source and the divided regions of the main display module, and their intersection in the spatial optical path. [Figure 19A]This is an explanatory diagram of the spatial light path for the combination of the third backlight source and each display block. [Figure 19B] This is an explanatory diagram of the spatial light path for the combination of the third backlight source and each display block. [Figure 19C] This is an explanatory diagram of the spatial light path for the combination of the third backlight source and each display block. [Figure 19D] This is an explanatory diagram showing the combination of the third backlight source and the divided regions of the main display module, and their intersection in the spatial optical path. [Figure 19E] This is an explanatory diagram showing the combination of the third backlight source and the divided regions of the main display module, and their intersection in the spatial optical path. [Figure 20A] This is an explanatory diagram of the spatial light path of the combination of the first backlight source and the first display block. [Figure 20B] This is an explanatory diagram of the spatial light path for the combination of the second backlight source and the second display block. [Figure 20C] This is an explanatory diagram of the spatial light path of the combination of the third backlight source and the third display block. [Figure 20D] This is an explanatory diagram showing the combination of the divided regions of the backlight module and the main display module, and their intersection in the spatial optical path. [Figure 20E] This is an explanatory diagram showing the combination of the divided regions of the backlight module and the main display module, and their intersection in the spatial optical path. [Figure 21A] This is an explanatory diagram of the spatial light path for the combination of the third backlight source and the first display block. [Figure 21B] This is an explanatory diagram of the spatial light path for the combination of the second backlight source and the second display block. [Figure 21C] This is an explanatory diagram of the spatial light path of the combination of the first backlight source and the third display block. [Figure 21D] This is an explanatory diagram showing the combination of the divided regions of the backlight module and the main display module, and their intersection in the spatial optical path. [Figure 21E]This is an explanatory diagram showing the combination of the divided regions of the backlight module and the main display module, and their intersection in the spatial optical path. [Figure 22A] This is an explanatory diagram showing the combination of a naked-eye stereoscopic image display device and an imaging semi-reflecting mirror. [Figure 22B] This is an explanatory diagram showing the combination of a naked-eye stereoscopic image display device and an imaging semi-reflecting mirror. [Figure 23A] This is a diagram illustrating the extended eyebox array. [Figure 23B] This is a diagram illustrating the extended eyebox array. [Figure 24A] This is an explanatory diagram showing examples of a backlight module, a main display module, and a light-shielding module. [Figure 24B] This is an explanatory diagram of an example of an extended eyebox array. [Figure 24C] This is an explanatory diagram of an example of an extended eyebox array. [Figure 25A] This is an explanatory diagram illustrating an example of a corresponding matrix table for a small eyebox, display block, and backlight source. [Figure 25B] This is an explanatory diagram illustrating an example of a corresponding matrix table for a small eyebox, display block, and backlight source. [Figure 26A] This is an explanatory diagram showing the switching timing of the small eye boxes for the left and right eyes, the main display module display block, the light-shielding module switching block, and the backlight light source of the backlight module in a glasses-free stereoscopic image display device. [Figure 26B] This is an explanatory diagram showing the switching timing of the small eye boxes for the left and right eyes, the main display module display block, the light-shielding module switching block, and the backlight light source of the backlight module in a glasses-free stereoscopic image display device. [Figure 26C] This is an explanatory diagram showing the switching timing of the small eye boxes for the left and right eyes, the main display module display block, the light-shielding module switching block, and the backlight light source of the backlight module in a glasses-free stereoscopic image display device. [Figure 26D]This is an explanatory diagram showing the switching timing of the small eye boxes for the left and right eyes, the main display module display block, the light-shielding module switching block, and the backlight light source of the backlight module in a glasses-free stereoscopic image display device. [Modes for carrying out the invention]

[0034] The optical paths described below are described with the direction of light emission from the light-emitting surface being forward, in accordance with the common understanding of those skilled in the art. However, when the terms "forward" and "backward" are used to describe the image formation position, it means that the image formation position is located in front of or behind the curved mirror reflective surface, when the corresponding image is a real image or a virtual image.

[0035] An off-axis dual mirror module 2 can be used to extend the equivalent distance of the backlight source, satisfy the condition that the object distance for real image formation is greater than the focal length of the concave mirror, reduce space usage, and form a directional beam. As shown in Figures 2A-2D, the off-axis dual mirror module 2 includes a first mirror 21 and a second curved mirror 22 that are offset from each other's optical axes, and the mirror centers MC of the first mirror (here, a curved mirror) 21 and the second curved mirror 22 are not on each other's optical axes OA. Using a smaller area backlight module 1, a more distant virtual image of the backlight source is formed, expanded behind the second curved mirror 22, after reflection by the first mirror 21 and the second curved mirror 22. The position of the virtual image of the backlight source is outside the focal length of the imaging concave mirror 5, and the real image of the backlight source is formed via the imaging concave mirror 5.

[0036] Light emitted from the backlight source of the backlight module 1 is projected onto the first mirror 21, reflected by the first mirror 21 and projected onto the second curved mirror 22, and reflected by the second curved mirror 22 and projected onto the display 3. A concave mirror can be used for the second curved mirror 22 to form a virtual image of the backlight source away from the imaging concave mirror.

[0037] After the light from the backlight module 1 is reflected by the first mirror 21, whether the resulting image is a real image of the backlight source formed in front of the first mirror 21 or a virtual image of the backlight source behind the first mirror 21, it must be between the second curved mirror 22 and the focal length of the second curved mirror 22, so that the light is reflected by the second curved mirror 22 and forms a virtual image 1_im of the backlight source behind the second curved mirror 22. For this reason, as shown in Figures 2A and 2C, the first mirror 21 may be a concave mirror, as shown in Figures 2B and 2D, a convex mirror, or a plane mirror, as long as it can form an image within the focal length of the second curved mirror 22. Next, the light is reflected by the second curved mirror 22 and forms a virtual image 1_im of the backlight source behind the second curved mirror 22, as shown in Figure 3A.

[0038] The first optical path from the backlight source to the first mirror 21 and the second optical path from the second curved mirror 22 to the display 3 may intersect each other, as shown in Figures 2A and 2B, or they may not intersect each other, as shown in Figures 2C and 2D.

[0039] Figure 3A shows a display device combining an off-axis dual mirror module 2 with a relatively small backlight module 1, which offers the advantages of reducing the overall space required and allowing a clear and bright image to be viewed in the eye box EB where the backlight source's real image is formed.

[0040] As shown in Figure 3B, the equivalent backlight source of the display 3 is the virtual image 1_im of the backlight source formed behind the second curved mirror 22. The diameter of the second curved mirror 22 is smaller than the cross-section of the beam diffused from the virtual image 1_im to the second curved mirror 22. In other words, the boundary 221 of the second curved mirror 22 limits the beam diffusion angle of the virtual image 1_im of the backlight source, which is equivalent to forming a directional backlight beam B.

[0041] In the design of the backlight module, LEDs are used as the backlight source, and a backlight source array 11 is configured as shown in Figure 4A, which can be further combined with a conical light cup array 12. The conical light cup array 12 consists of multiple conical light cups. The conical light cups may be hollow light cups coated with a reflective film on their surface, or transparent solid light guides. By installing the conical light cup array on the light emission side of the backlight source array 11, the diffusion angle of the light source is reduced, forming a directional backlight.

[0042] Alternatively, as shown in Figure 4B, a cone-shaped light cup array 12, a polarizing lens array 13T, and a focusing lens array 13L are arranged in order on the light-emitting side of the backlight light source array 11. The polarizing lens array 13T is used to concentrate the projection angle of each light source, and the focusing lens array 13L further reduces the diffusion angle of the light sources to form a directional backlight.

[0043] Alternatively, a conical light cup array 12 and a focusing lens 14 are added together, as shown in Figure 4C. Or, as in the inclined conical light cup array 12 in Figure 4D, conical light cups with different inclination angles are included, where the inclination angle of each light cup increases as it moves away from the center of the array, the diffusion angle of the light source decreases, and the projection angle of each light source converges.

[0044] As shown in Figure 5A, the backlight light source array 11 may be configured using LEDs 13 with built-in lenses on a flat substrate. Alternatively, as shown in Figure 5B, the backlight light source array 11 may be configured using LEDs 13 with built-in lenses on a curved substrate, or as shown in Figure 5C, the backlight light source array 11 may be configured using LEDs 13 with built-in lenses on a flat substrate, and a focusing lens 14 may be added in front of the backlight light source array 11.

[0045] As shown in Figure 6A, the backlight light source array 10 of the backlight module is formed outside the focal length of the imaging concave mirror 5 via imaging by the off-axis dual mirror module 2 (virtual image 10_im of the backlight light source array). The backlight beam reflected from the off-axis dual mirror module 2 passes through imaging by the imaging concave mirror 5 (real image 10_re of the backlight light source array), and then the real image 10_re of the backlight light source array is projected onto the imaging semi-reflector 7 (front glass), and reflected by the imaging semi-reflector 7 (front glass) onto the backlight focusing surface BFP to form an eye box array EBA. The backlight light source array 10 includes multiple backlight light sources, and each backlight light source, after passing through the off-axis dual mirror module 2 and the imaging concave mirror 5, forms an independent small eye box EB (see Figure 7), and all small eye boxes EB are coupled to the eye box array EBA. As shown in Figure 6B, in this eyebox array EBA, the observer's eye can see a virtual image G_im, which is far from the observer, through the imaging semi-reflecting mirror 7.

[0046] As shown in Figure 7, the naked-eye stereoscopic image display device includes a backlight module 1, an off-axis dual mirror module 2, a display 3, an imaging concave mirror 5, and an eye-tracking module 6. The backlight module 1, the display 3, and the eye-tracking module 6 are all connected to a control calculation module 61, which transmits detection information and control signals.

[0047] The backlight module 1 includes a backlight light source array 11 composed of multiple backlight light sources and emits a backlight beam B.

[0048] The off-axis dual mirror module 2 includes a first mirror 21 and a second curved mirror that reflect the backlight beam B.

[0049] Display 3 (see Figure 11A) includes a main display module 31 and a light-shielding module 4 that are stacked on top of each other.

[0050] The main display module 31 alternately displays the left-eye parallax image and the right-eye parallax image, defining multiple display blocks. The light-blocking module 4 defines multiple switching blocks, each of which corresponds to a display block and alternately blocks the penetration of light.

[0051] The backlight beam B passes through the display 3 to form the image beam D.

[0052] The imaging concave mirror 5 reflects the image beam D.

[0053] The eye-tracking module 6 detects the relative position information between the observer's left eye and the eye-tracking module in the space between the left and right eyes.

[0054] The control calculation module 61 receives detection information from the eye-tracking module 6 and obtains the left eye position E_L and right eye position E_R in the observer's space through identification, calculation, table lookup, or inference. These values ​​may be coordinates in a Cartesian coordinate system, cylindrical coordinate system, spherical coordinate system, or other coordinate system. From the left eye position E_L and right eye position E_R, the corresponding left eye sub-eyebox EB_L and right eye sub-eyebox EB_R are obtained in the eyebox array EBA, and from the left eye sub-eyebox EB_L and right eye sub-eyebox EB_R, the corresponding left eye backlight source Led_L and right eye backlight source Led_R are obtained.

[0055] Light emitted from the backlight light source array 11 of the backlight module 1 is reflected by the off-axis dual mirror module 2, the imaging concave mirror 5, and the imaging semi-reflecting mirror 7, and converges on the backlight focusing plane BFP on the side of the imaging semi-reflecting mirror 7 closer to the observer, forming a backlight light source real image which is an eyebox array EBA containing multiple small eyeboxes EB. The main display module 31 displays a parallax image for the left or right eye, and the emitted light is reflected by the imaging concave mirror 5 and the imaging semi-reflecting mirror 7, forming a virtual parallax image G_im for the left or right eye on the image focal plane IFP on the side of the imaging semi-reflecting mirror 7 farther from the observer.

[0056] When the main display module 31 displays the left-eye parallax image, the left-eye backlight source Led_L is turned on, and the light-shielding module 4 switches the switching block. When the main display module 31 displays the right-eye parallax image, the right-eye backlight source Led_R is turned on, and the light-shielding module 4 switches the switching block. The display blocks of the displayed left-eye or right-eye parallax image can be displayed in time division, allowing both the left and right eyes to continuously see a bright and clear virtual image G_im of the left or right eye parallax image without crosstalk afterimages, thereby forming stereoscopic vision.

[0057] The backlight module 1, in combination with the off-axis dual mirror module 2, forms a directional backlight beam. Therefore, the small eyeboxes EB included in the eyebox array EBA are not only distributed on the backlight focusing surface BFP, but their effective area extends to the depth in front of and behind the observer's line of sight. In other words, the effective area of ​​the eyebox array EBA extends along both directions of the Z-axis. The Z-axis is perpendicular to the X-axis (horizontal) and Y-axis (vertical). Depending on the current position of the eye, different small eyeboxes EB can be switched, and the effective area of ​​the small eyeboxes EB shrinks as it moves forward and backward along the Z-axis, and shrinks further away from the backlight focusing surface BFP. Furthermore, by combining each display block with at least one backlight source located in a different position, multiple smaller eyeboxes EB_V of other groups can be defined outside the space of the eyebox array EBA on both sides of the backlight focusing surface BFP, forming a wider-range extended eyebox array EBA_V including the original eyebox array EBA. Since the entire extended eyebox array EBA_V includes multiple smaller eyeboxes EB_V of other groups, like a combination of two trapezoidal stereoscopic structures joined together at their bases, it can cover the possible range of movement when the eyes move up and down, left and right, and forward and backward, providing a wide-field-of-view naked-eye stereoscopic image display device.

[0058] The light-shielding module 4 switches each switching block according to the settings. Each time, one or more switching blocks are selected and switched, and used to shield the display blocks on the main display module 31 screen that have not yet been converted. By simply not displaying the display blocks that have not yet been converted, afterimages are eliminated, allowing both eyes to continuously view an image without afterimages or crosstalk, thus realizing a high-quality glasses-free stereoscopic image display device.

[0059] Furthermore, the on-time interval of the switching blocks, the number of switching blocks on, or the time interval of the backlight illumination can be used to adjust the brightness of the image. The more display blocks displayed simultaneously, or the longer the display time of each display block, the brighter the visible image will be.

[0060] The eye-tracking module 6 uses imaging, ultrasound, millimeter-wave radar, laser, or a combination of these detectors to detect the relative positions of the observer's left and right eyes and the eye-tracking module itself. The control and calculation module 61 receives the detection information from the eye-tracking module 6 and obtains the observer's left eye position E_L and right eye position E_R in space through identification, calculation, table lookup, or inference. These values ​​may be in a Cartesian coordinate system, cylindrical coordinate system, spherical coordinate system, or other coordinate system.

[0061] As shown in Figure 8A, if we consider only the eyebox array EBA on the backlight focusing surface BFP without considering the distribution of small eyeboxes in the Z-axis direction, the eyebox array EBA is composed of many small eyeboxes, and the control calculation module 61 searches for the small eyeboxes EB_43 and EB_23 corresponding to the left eye position and right eye position, respectively, in the eyebox array EBA based on the left eye position E_L and the right eye position E_R. When the main display module 31 displays the left eye disparity image, the backlight light source Led_43 corresponding to the small eyebox EB_43 lights up, and when the main display module 31 displays the right eye disparity image, the backlight light source Led_23 corresponding to the small eyebox EB_23 lights up.

[0062] As shown in Figure 8B, when the observer moves their head, the corresponding backlight sources Led_52 and Led_32 are switched on according to the small eye boxes EB_52 and EB_32 corresponding to the eye positions E_L' and E_R' after the eye movement, allowing the left and right eyes to continue viewing the disparity image and creating stereoscopic vision.

[0063] As shown in Figure 8C, one eye can also correspond to 2n+1 adjacent small eyeboxes EB in the eyebox array EBA, where n>0 and n is a positive integer. For example, one eye can correspond to 3 (n=1), 5 (n=2), or 7 (n=3) small eyeboxes. Taking three adjacent small eyeboxes as an example, the central small eyebox EB_93 and its two adjacent small eyeboxes EB_83 and EB_103 are selected according to the position of the pupil of the left eye, and the central small eyebox EB_43 and its two adjacent small eyeboxes EB_33 and EB_53 are selected according to the position of the pupil of the right eye. When the main display module 31 displays the left eye disparity image, the backlight sources Led_83, Led_93, and Led_103 corresponding to the small eyeboxes EB_83, EB_93, and EB_103 are illuminated simultaneously. When the main display module 31 displays the right-eye parallax image, the backlight sources Led_33, Led_43, and Led_53 corresponding to the small eye boxes EB_33, EB_43, and EB_53 are illuminated simultaneously.

[0064] As shown in Figure 8D, when the pupil of the observer's left eye moves to the position of small eyebox EB_103 and the pupil of the right eye moves to the position of small eyebox EB_53, three small eyeboxes EB_93, EB_103, and EB_113 are re-selected according to the position of the left pupil, and three small eyeboxes EB_43, EB_53, and EB_63 are re-selected according to the position of the right pupil. This allows both the left and right eyes to continue viewing the disparity image, reducing image interruptions that occur when the switching of adjacent small eyeboxes in the horizontal direction is not fast enough when the gaze moves rapidly in the horizontal direction, and thus avoiding image flickering.

[0065] Using 2n+1 adjacent eyeboxes, the system can be configured in either a left-right (horizontal) or up-down (vertical) direction. The central eyebox is aligned with the pupil of the eye, and the other eyeboxes are dynamically switched. The adjacent eyeboxes to the left / right or up / down are used as buffers during eye movement tracking.

[0066] When the human eye sees an object, the object is formed as an image on the retina, stimulating the optic nerve. This is converted into nerve impulses in about 1-2 ms, which are then transmitted to the brain via the optic nerve, causing the person to perceive an image of the object. However, when the object is removed, the impression the optic nerve has of it does not disappear immediately, but persists for 0.1-0.4 seconds. This property is called "visual persistence."

[0067] When the conversion speed of still images is faster than 10-16 fps (frames per second), humans perceive the image as continuous and flicker-free. However, for dynamic images, the brain needs to perceive the screen as smooth, requiring a conversion speed of 24-60 fps. Therefore, the image interval seen by each eye must be less than 1 / 24-1 / 60 of a second, meaning the image interruption time Tg must be less than 41.67 ms-16.78 ms. The slower the movement of the scene on the screen, the longer the acceptable image interruption time Tg becomes, approaching 41.67 milliseconds. The faster the image movement, the shorter the acceptable image interruption time Tg becomes, approaching 16.78 milliseconds before the image appears continuous and flicker-free.

[0068] As shown in Figure 9, when switching between left-eye and right-eye images using the same liquid crystal display panel, the image interruption time Tg between the two preceding left-eye images or the two preceding right-eye images must be 1 / 24 to 1 / 60 seconds or less, i.e., ≤41.67 ms to 16.78 ms.

[0069] In an ideal state, when the entire LCD display panel screen completely switches to the left-eye image, the backlight array also switches to the light source corresponding to the left eye. When the entire LCD display panel screen completely switches to the right-eye image, the backlight array also switches to the light source corresponding to the right eye, and this cycle continues.

[0070] As shown in Figure 10A, in actual conditions, the switching of liquid crystals takes time, and the liquid crystal response time is the rise time Tr + fall time Tf, which refer to the brightness range of 10% to 90% and 90% to 10% of a single pixel, respectively. The conversion is not performed simultaneously for all pixels on the screen, but is scanned and switched sequentially, so there is a time difference in the conversion for pixels in different areas.

[0071] As shown in Figure 10B, current general automotive liquid crystal display panels have difficulty completely switching all pixels on the entire screen to the image of the other eye within the image interruption time Tg, then switching back to the image of the original eye, allowing the backlight to pass through the entire display panel for at least 2ms to stimulate the optic nerve, converting it into nerve impulses, and displaying a complete image. During processing, there are pixels pix_t in a partially converted state on the screen, and furthermore, there are pixels pix_p in the previous image state.

[0072] When the light source corresponding to the backlight array is turned on, the observer may see an image in which the converted state pixels pix_t and the previous state pixels pix_p are mixed. This is known as afterimage or crosstalk, which greatly affects the quality of the observed image and can cause dizziness or discomfort in the observer.

[0073] As shown in Figures 11A and 11B, in order to solve the above problem, a light-shielding module 4 is superimposed on the light-incident or light-emitting side of the main display module 31, and in this embodiment, the light-shielding module 4 is also a display module. The two display modules are bonded together with an optical adhesive (OCA), and the backlight beam B needs to pass through the main display module 31 and the light-shielding module 4 simultaneously in order to generate the image beam D.

[0074] When the light-incident side of the main display module 31 overlaps with the light-shielding module 4, multiple switching blocks of the light-shielding module 4 are switched in a time-division manner to control the area through which the backlight beam B can pass through the main display module 31, so that the image of a specific display area is projected by forming an image beam D.

[0075] If the light-emitting side of the main display module 31 overlaps with the light-shielding module 4, multiple switching blocks of the light-shielding module 4 are switched in a time-division manner to control the image beam D so that it transmits only a specific display area and projects it forward.

[0076] For the sake of explanation, the following description will only explain the method of stacking the light-shielding module 4 on the light-incident side of the main display module 31 to form the display 3.

[0077] As shown in Figure 11C, the main display module 31 uses, for example, an IPS (In-Plane Switching) color liquid crystal display panel with a wide color gamut, while the light-shielding module 4 uses a liquid crystal material with a faster response time, such as a TN (Twisted Nematic) monochrome liquid crystal display panel, and the response time (Tr+Tf) of the TN liquid crystal is shorter than that of the IPS liquid crystal.

[0078] As shown in the overlapping detailed structure in Figure 11D, the main display module 31 includes a lower polarizer 32, a liquid crystal layer 33, and an upper polarizer 34, while the light-shielding module 4 includes a lower polarizer 42, a liquid crystal layer 43, and an upper polarizer 44, with an optical adhesive OCA between the main display module 31 and the light-shielding module 4. The lower polarizer 32 of the main display module 31 and the upper polarizer 34 of the light-shielding module 4 are polarizers having the same polarization direction. Even if one of them is removed, the original function of reducing light source loss and thus reducing costs is maintained, and as shown in Figure 11E, the upper polarizer 44 of the light-shielding module 4 is removed. Alternatively, as shown in Figure 11F, the lower polarizer 32 of the main display module 31 is removed.

[0079] The display system that projects parallax images for the left and right eyes requires a high-brightness backlight module 1 because the brightness of the backlight is evenly divided over time by switching the timing. However, about 50% of the backlight beam B projected by the backlight module 1 has a different polarization direction from the lower polarizer 42 and is absorbed by the lower polarizer 42. The remaining 50% of the light has the same polarization direction as the lower polarizer 42 and passes through the lower polarizer 42 before entering the liquid crystal layer 43. Under the illumination of the backlight beam B, the lower polarizer 42 absorbs almost half of the energy of the backlight beam B, causing its temperature to rise rapidly and making it susceptible to damage to the light-shielding module 4 and the main display module 31.

[0080] Therefore, by replacing the lower polarizer 42 closest to the light incident side (display 3) with a reflective polarizer 45, light with a different polarization direction than the lower polarizer 42 can be reflected and not absorbed by the lower polarizer 42, thereby significantly lowering the temperature of the light shielding module 4 and the main display module 31. A higher brightness backlight module can be used to increase the brightness of the display, while also avoiding damage to the light shielding module 4 and the main display module 31 due to high temperatures. Figure 11G shows the result of replacing the lower polarizer 42 in Figure 11D with a reflective polarizer 45, Figure 11H shows the result of replacing the lower polarizer 42 in Figure 11E with a reflective polarizer 45, and Figure 11I shows the result of replacing the lower polarizer 42 in Figure 11F with a reflective polarizer 45.

[0081] If the display 3 is stacked such that the light-shielding module 4 is placed on the light-emitting side of the main display module 31, the lower polarizer 32 closest to the light-incident side is replaced with a reflective polarizer 45.

[0082] As shown in the liquid crystal conversion cycle curve of the main display module 31 in Figure 12A, if the complete liquid crystal conversion cycle of the main display module 31 is T, the time interval from when the image light is projected onto the left eye until the next image light is projected onto the left eye is 2T. As shown in Figure 12B, the main display module 31 is a color liquid crystal display panel, defined as three display blocks, for example, the first display block IPS_1, the second display block IPS_2, and the third display block IPS_3, each containing multiple pixels. When a pixel is switched ON, it transmits backlight and displays the set color and brightness, and when a pixel is switched OFF, it becomes opaque. The light-shielding module 4 is a monochrome liquid crystal display panel, and it is also defined that there are, for example, three switching blocks of the same size, which are the first switching block TN_1, the second switching block TN_2, and the third switching block TN_3. The first switching block TN_1 corresponds to the first display block IPS_1, the second switching block TN_2 corresponds to the second display block IPS_2, and the third switching block TN_3 corresponds to the third display block IPS_3. Each switching block can contain multiple pixels or a single pixel, and when a pixel is switched ON, it transmits light, and when a pixel is switched OFF, it becomes opaque.

[0083] As shown in Figure 13, the image for the left eye is displayed first. After turning on the liquid crystal of the first display block IPS_1, the first switching block TN_1 and the backlight source for the left eye are turned on. Next, the backlight source for the left eye and the first switching block TN_1 are switched off, and then the liquid crystal of the first display block IPS_1 is switched off.

[0084] The timing of IPS_2 is slightly later than that of IPS_1. The switching timing of the second display block IPS_2, the second switching block TN_2, and the left eye backlight source are the same as those of the first display block IPS_1, the first switching block TN_1, and the left eye backlight source, respectively.

[0085] The timing of IPS_3 is slightly later than that of IPS_2. The switching timing of the third display block IPS_3, the third switching block TN_3, and the left eye backlight source are the same as those of the first display block IPS_1, the first switching block TN_1, and the left eye backlight source, respectively.

[0086] After the display of the left eye image is complete and the first display block IPS_1 LCD switches to OFF, the first display block IPS_1 LCD switches from OFF to ON, displays the right eye image, and then switches the first switching block TN_1 and the right eye backlight source ON. Next, the right eye backlight source and the first switching block TN_1 are switched to OFF, and then the LCD of the first display block IPS_1 is switched to OFF.

[0087] After turning off the LCD of the second display block IPS_2, it is switched on to display the right eye image. The switching timing for the second display block IPS_2, the second switching block TN_2, and the right eye backlight source is the same as that for the first display block IPS_1, the first switching block TN_1, and the right eye backlight source, respectively, as described above.

[0088] After turning off the LCD of the third display block IPS_3, it is switched on to display the image for the right eye. The switching timing for the third display block IPS_3, the third switching block TN_3, and the right eye backlight source is the same as that for the first display block IPS_1, the first switching block TN_1, and the right eye backlight source, respectively.

[0089] The switching order is IPS_1 → IPS_2 → IPS_3 → IPS_1, switching one block each time in this cycle. Alternatively, multiple blocks can be switched at once, for example, two blocks at once: IPS_1 & IPS_2 → IPS_2 & IPS_3 → IPS_3 & IPS_1 → IPS_1 & IPS_2. The following is by analogy.

[0090] When the image in a display block is being switched or has not yet switched (the previous image), the corresponding backlight source is turned off or the corresponding switching block is turned off until the image switch is complete. After that, the corresponding switching block and the corresponding backlight source are turned on to avoid projection afterimages.

[0091] Generally speaking, the duration of TN switching block ON is shorter than the duration of IPS display block ON, and the duration of backlight light source ON is shorter than the duration of each TN switching block ON. The time interval between the transmission of the backlight beam projected onto the same eye twice, before and after an IPS display block pixel, must be shorter than the image interruption time Tg (16.78ms to 41.67ms). In other words, the switching interval time for each display block that projects the image beam onto the same eye must be less than Tg to satisfy the visual duration requirement, resulting in smooth dynamic images.

[0092] The backlight source illuminates the entire display area, and the IPS display block that is being switched or has not been switched (the previous image) is shielded by the OFF state TN switching block, preventing the backlight from passing through and thus preventing the observer from seeing afterimages or crosstalk.

[0093] As shown in Figure 14, within the first 1 / 3T (=1 / 6 × 2T) time, the first display block IPS_1 completes the left eye image conversion, and the backlight source corresponding to the left eye small eyebox lights up. However, only the backlight beam that passes through the first switching block TN_1 passes through the first display block IPS_1 to form the left eye IPS_1 image beam.

[0094] During the second 1 / 3T time interval, the second display block IPS_2 completes the left-eye image conversion, and the backlight source corresponding to the left-eye small eyebox lights up. However, only the backlight beam that passes through the second switching block TN_2 passes through the second display block IPS_2 to form the left-eye IPS_2 image beam.

[0095] During the third 1 / 3T time interval, the third display block IPS_3 completes the left-eye image conversion, and the backlight source corresponding to the left-eye small eyebox lights up. However, only the backlight beam that passes through the third switching block TN_3 passes through the third display block IPS_3 to form the left-eye IPS_3 image beam.

[0096] During the fourth 1 / 3T time, the first display block IPS_1 completes the right eye image conversion, and the backlight source corresponding to the right eye mini-eyebox lights up. However, only the backlight beam that passes through the first switching block TN_1 passes through the first display block IPS_1 to form the right eye IPS_1 image beam, thus creating a cycle.

[0097] The projection effect in Figure 14 is shown in Figure 15. During the first 1 / 3T time interval, only the image from the first display block IPS_1 is projected onto the left eye, and no image is projected onto the right eye. During the second 1 / 3T time interval, only the image from the second display block IPS_2 is projected onto the left eye, and no image is projected onto the right eye. During the third 1 / 3T time interval, only the image from the third display block IPS_3 is projected to the left eye, and no image is projected to the right eye. During the fourth 1 / 3T time interval, no image is projected onto the left eye, and only the image from the first display block IPS_1 is projected onto the right eye. During the fifth 1 / 3T time interval, no image is projected onto the left eye, and only the image from the second display block IPS_2 is projected onto the right eye. During the sixth 1 / 3T time interval, no image is projected onto the left eye, and only the image from the third display block IPS_3 is projected onto the right eye. During the seventh 1 / 3T time, only the image from the first display block IPS_1 is projected onto the left eye, and no image is projected onto the right eye. The projection effect during the seventh 1 / 3T time and the first 1 / 3T time are the same, thus creating a cycle.

[0098] The left eye sequentially views each display block IPS_1, IPS_2, and IPS_3 of the left-eye image, forming a complete left-eye image from the combination of images in each block. Then, from 16.78 ms to 41.67 ms, it again sequentially views each display block of the left-eye image, with the interval between the two left-eye images of each display block being shorter than the time it takes for the afterimage to disappear. Correspondingly, the right eye also sequentially views each display block IPS_1, IPS_2, and IPS_3 of the right-eye image, with the interval between the two right-eye images of each display block being shorter than the time it takes for the afterimage to disappear. Therefore, a continuous, smooth image can be formed in both the left and right eyes.

[0099] Figures 16A, 16B, and 16C illustrate the imaging of the backlight module 1 and the main display module 31. The white blocks of the backlight module 1 are the blocks where the LEDs light up, and also correspond to the small eyeboxes where the eyebox array EBA lights up. The white blocks of the main display module 31 are the display blocks that have been switched ON, and also correspond to the parallax image virtual image G_im visible at the image focal plane IFP.

[0100] As shown in Figure 16A, the backlight light source array of the backlight module 1 emits a backlight beam B, which passes through the light-shielding module 4 and the main display module 31 to form an image beam D. The image beam D is reflected by the imaging concave mirror 5, and the backlight light source array of the backlight module 1 forms a real image of the backlight source (eyebox array EBA) at the backlight focusing surface BFP in front of the imaging concave mirror 5, while the parallax image of the main display module 31 forms a parallax image virtual image G_im behind the imaging concave mirror 5.

[0101] As shown in Figure 16B, when only the second backlight light source Led_2 of backlight module 1 is lit, the light shielding module 4 switches only the first switching block TN_1 ON, and only the second small eye box EB_2 can clearly see the virtual image IPS_1_im of the first display block IPS_1.

[0102] As shown in Figure 16C, when only the third backlight light source Led_3 of backlight module 1 is lit, the light shielding module 4 turns on only the second switching block TN_2 and the third switching block TN_3, so that only the third small eye box EB_3 can clearly see the virtual images IPS_2_im and IPS_3_im of the second display block IPS_2 and the third display block IPS_3.

[0103] Figures 17A to 21E show a small eyebox at a specific location, consisting of a backlight source and a display block. The backlight source shown in the aforementioned figures is a surface light source, and the real image formed is a surface real image on the focal plane.

[0104] As shown in Figures 17A to 17C, when only the first backlight source Led_1 is lit, the first display block IPS_1, the second display block IPS_2, and the third display block IPS_3 are combined to display an image, and the image beams in these optical paths are focused on the first small eye box EB_1.

[0105] As shown in Figure 17D, the optical paths from Figures 17A to 17C are superimposed to form an intersection region, which is defined as the small eyebox EB_1V. This intersection region is a small eyebox that has volume in three-dimensional space, with its volume gradually decreasing towards the front and back, similar to the small eyebox EB_1V which is the intersection of the three shaded regions shown in Figure 17E. When the backlight source and display block combinations shown in Figures 17A to 17C, namely IPS_1 and Led_1, IPS_2 and Led_1, and IPS_3 and Led_1 are combined and displayed in sequence, the images of IPS_1 to IPS_3 become visible in this small eyebox EB_1V region, meaning a complete image is visible.

[0106] As shown in Figures 18A to 18C, when only the second backlight source Led_2 is lit, the first display block IPS_1, the second display block IPS_2, and the third display block IPS_3 are combined and displayed, and the image beams in these optical paths are focused on the second small eye box EB_2.

[0107] As shown in Figure 18D, the optical paths in Figures 18A to 18C are superimposed to form an intersection region, which is defined as the small eyebox EB_2V, as shown by the intersection of the three shaded regions in Figure 18E. The state of the small eyebox EB_2V is similar to the state of the small eyebox EB_1V in Figures 17D and 17E. When the backlight source and display block combinations shown in Figures 18A to 18C, namely IPS_1 and Led_2; IPS_2 and Led_2; and IPS_3 and Led_2 are combined and displayed in sequence, the images of IPS_1 to IPS_3 become visible in this small eyebox EB_2V region, meaning a complete image is visible.

[0108] As shown in Figures 19A to 19C, when only the third backlight source Led_3 is lit, the first display block IPS_1, the second display block IPS_2, and the third display block IPS_3 are combined and displayed, and the image beams in these optical paths are focused on the third small eye box EB_3.

[0109] As shown in Figure 19D, the optical paths from Figures 19A to 19C are superimposed to form an intersection region, which is defined as the small eyebox EB_3V. As shown by the intersection of the three shaded regions in Figure 19E, the state of the small eyebox EB_3V is similar to the state of the small eyebox EB_1V in Figures 17D and 17E. The combinations of backlight sources and display blocks shown in Figures 19A to 19C, namely IPS_1 and Led_3, IPS_2 and Led_3, and IPS_3 and Led_3, are displayed in sequence, and the images of IPS_1 to IPS_3 are visible in the region of this small eyebox EB_3V, meaning that a complete image can be seen.

[0110] Using a directional backlight beam, the image beams passing through the small eye boxes EB_1, EB_2, and EB_3 become nearly parallel, and accordingly the small eye boxes EB_1V, EB_2V, and EB_3V become longer, increasing their volumetric area, which allows for different eye positions in the front-to-back direction and widening the visible area.

[0111] The optical paths shown in Figures 20A to 20C combine the first backlight light source Led_1, the second backlight light source Led_2, and the third backlight light source Led_3 with the first display block IPS_1, the second display block IPS_2, and the third display block IPS_3, respectively, so that the image beams of these optical paths are focused on the first small eyebox EB_1, the second small eyebox EB_2, and the third small eyebox EB_3, respectively.

[0112] As shown in Figure 20D, the optical paths of Figures 20A to 20C are superimposed to form an intersection region, which is defined as the small eyebox EB_123_123V. The intersection region has volume in three-dimensional space and is located between the imaging concave mirror 5 and the small eyeboxes EB_1, EB_2, and EB_3. It is a small eyebox that gradually shrinks towards the rear, as shown by the intersection of the three shaded regions shown in Figure 20E. Figures 20A to 20C show combinations of backlight sources and display blocks, namely IPS_1 and Led_1, IPS_2 and Led_2; and IPS_3 and Led_3, displayed in sequence. In this small eyebox EB_123_123V region, the images of IPS_1 to IPS_3 are visible, meaning that a complete image can be seen, thus accommodating different positions in the forward direction of the eye and widening the visible area.

[0113] The optical paths shown in Figures 21A to 21C combine the third backlight source Led_3, the second backlight source Led_2, and the first backlight source Led_1 with the first display block IPS_1, the second display block IPS_2, and the third display block IPS_3, respectively, so that the image beams of these optical paths are focused on the third small eyebox EB_3, the second small eyebox EB_2, and the first small eyebox EB_1, respectively.

[0114] As shown in Figure 21D, the optical paths of Figures 21A to 21C overlap to form an intersection region, which is defined as the small eyebox EB_123_321V, as shown in the shaded region of Figure 21E. The intersection region has volume in three-dimensional space and is located behind the small eyeboxes EB_1, EB_2, and EB_3. It is a small eyebox that gradually shrinks as it moves both forward and backward, as shown by the intersection of the three shaded regions shown in Figure 21E, namely the small eyebox EB_123_321V. Figures 21A to 21C show the combination of the backlight source and the corresponding display block. Only within this small eyebox EB_123_321V region can the images of IPS_1 to IPS_3 be visible, meaning that a complete image can be seen. Therefore, it can accommodate different positions in the direction behind the eye, and the visible area is widened.

[0115] As can be seen from Figures 17A to 21E, each display block is combined with at least one backlight source at a different position to define multiple smaller eyeboxes EB_V in other groups, including the original eyebox array EBA, outside the eyebox array EBA space on both sides of the backlight focusing plane BFP, forming a wider extended eyebox array EBA_V, i.e., a three-dimensional array containing more smaller eyeboxes EB_V. The effective area of ​​the smaller eyeboxes EB_V has depth in the front-to-back direction along the Z axis. By switching between different backlight sources and different display blocks, the image beam can be projected onto the smaller eyeboxes EB_V at different positions. Even if the eye position is outside the backlight focusing plane, different smaller eyeboxes EB_V can be selected according to the up-and-down, left-and-right, and front-to-back movement of the eye. Within the range of the extended eyebox array EBA_V, the left-eye parallax image or the right-eye parallax image can be fully viewed, providing a naked-eye stereoscopic image display device with a wide field of view. In the extended eyebox array EBA_V, 2n+1 adjacent small eyeboxes EB_V in the left-right or up-down direction correspond to the left or right eye and function as buffers during eye movement tracking.

[0116] As shown in Figures 22A and 22B, the aforementioned backlight module 1, main display module 31, and light-shielding module 4, in combination with the reflection of the imaging semi-reflector 7 (front glass), project an image onto the small eye box EB_V of the extended eye box array EBA_V according to the different positions of the observer's eyes. This allows the viewer to see a complete parallax image virtual image G_im without afterimages, crosstalk, or image interruptions, thereby realizing a high-quality naked-eye stereoscopic image display device.

[0117] As shown in Figures 23A and 23B, the small eyeboxes EB_V included in the wide-field-of-view extended eyebox array EBA_V are distributed not only on the backlight focusing surface (XY plane at Z=0) but also include the depth in front of and behind the observer's line of sight, for example, including 20 cm in both front and back (Z=20 to Z=-20). The distribution area shrinks slightly as it moves away from the backlight focusing surface. The extended eyebox array EBA_V is similar to a combination of two trapezoidal three-dimensional structures joined together at their lower bases, covering the visible movement range of the eye required for a naked-eye stereoscopic image display device. The relationship between the small eyeboxes EB_V at different positions in the extended eyebox array EBA_V, the corresponding backlight light sources of backlight module 1, and the display blocks of main display module 31 can be obtained by simulation or actual measurement, and a small eyebox-display block-backlight light source matrix table can be created. The small eyebox-display block-backlight source matrix table is stored, for example, in the control arithmetic module 61 or in a storage device connected to the control arithmetic module 61, and the table can be referenced during actual operation.

[0118] As shown in Figure 24A, in this embodiment, the backlight module 1 has an array of 7 × 3 backlight light sources (Led_11~Led_73), the light shielding module 4 has three switching blocks TN_1, TN_2, and TN_3 on the light incident side of the main display module 31, and the main display module 31 also has three display blocks IPS_1, IPS_2, and IPS_3, one for each of the switching blocks TN_1, TN_2, and TN_3. For example, as shown in Figure 24B, this is the distribution of small eye boxes with Z=0 in the extended eye box array EBA_V. The observer's eye is on a plane with a Z coordinate of 0 cm. The left eye corresponds to small eye box EB_V(0,0,0), and the right eye corresponds to small eye box EB_V(4,0,0). For example, as shown in Figure 24C, this is the distribution of small eye boxes with Z=20 in the extended eye box array EBA_V. The observer's eye is on a plane with a Z coordinate of 20 cm. The left eye corresponds to the small eyebox EB_V(-2,-1,20), and the right eye corresponds to the small eyebox EB_V(2,-1,20).

[0119] A small eyebox-display block-backlight source matrix table can be obtained through simulation or actual measurement. For example, the small eyebox-display block-backlight source matrix table MT shown in Figure 25A is a matrix table of backlight sources (LEDs) corresponding to different small eyeboxes (EB_V) and different display blocks (IPS) in the X-axis direction when Y=2 and Z=0. The small eyeboxes (EB_V) in these positions are close to the backlight focusing plane (XY plane at Z=0) of the extended eyebox array EBA_V, and the backlight sources (LEDs) of the display blocks (IPS) corresponding to the same small eyebox (EB_V) are all the same backlight sources. For example, if the left eye is in small eyebox EB_V(4,2,0), the matrix for the left eye is as follows:

[0120]

number

[0121] Figure 25B shows another portion of the small eyebox-display block-backlight source matrix table MT, which is a matrix table of backlight sources (LEDs) corresponding to different small eyeboxes (EB_V) and different display blocks (IPS) in the X-axis direction when Y=-2 and Z=10. The small eyeboxes (EB_V) at these positions are far from the backlight focusing plane (XY plane at Z=0) of the extended eyebox array EBA_V, and the backlight sources (LEDs) corresponding to the display blocks (IPS) of the same small eyebox (EB_V) may correspond to backlight sources at the same position, such as EB_V(0,-2,10), or to backlight sources at different positions. For example, if the left eye is in small eyebox EB_V(4,-2,10), the matrix for the left eye is as follows:

[0122]

number

[0123] The control calculation module 61 obtains detection information for the left and right eyes from the eye-tracking module 6 to obtain the position coordinates of the left and right eyes, and then obtains the corresponding left eye mini-eyebox and right eye mini-eyebox from the left and right eye position coordinates. Then, from these mini-eyebox-display block-backlight source matrix table MT, it finds the display block-backlight source matrix corresponding to the current left eye mini-eyebox and the display block-backlight source matrix corresponding to the current right eye mini-eyebox, selects them to switch the display block and backlight source, shows the entire parallax image virtual image of the left eye to the observer's left eye, and shows the entire parallax image virtual image of the right eye to the right eye, forming a naked-eye stereoscopic image.

[0124] Turning on all switching blocks is equivalent to removing the light-shielding module 4. In this case, only the small eyebox-backlight source matrix table is used, and each eye can correspond to one or more small eyeboxes. The control calculation module 61 obtains detection information for the left and right eyes from the gaze tracking module 6 to obtain the position coordinates of the left and right eyes, and then obtains the corresponding left eye small eyebox and right eye small eyebox from the position coordinates of the left and right eyes. Then, from these small eyebox-backlight source matrix tables MT, it finds the left eye backlight source corresponding to the current left eye small eyebox and the right eye backlight source corresponding to the current right eye small eyebox, and combines the display modules to switch between the left eye backlight source and the right eye backlight source, showing the entire virtual image of the left eye parallax image to the observer's left eye and the entire virtual image of the right eye parallax image to the right eye, forming a naked-eye stereoscopic image.

[0125] If only backlight module 1 and off-axis dual mirror module 2 are present in the projection light path, the directional backlight can penetrate the ray intersection region of the display panel and extend further in the front-to-back direction, so shading module 4 is not present (similar to Figures 17E, 18E, and 19E). Not only is a complete image visible in the eyebox region of the focal plane, but a complete image can also be seen in the intersection region extending forward and backward along the Z axis, i.e., the effective area of ​​the small eyebox extends in the Z axis direction. When the eye moves along the Z axis, it may also enter the small eyebox region. If backlight module 1, off-axis dual mirror module 2, and shading module 4 are present in the projection light path, multiple small eyeboxes of other groups can be defined in a wider area outside the intersection of all beams (see Figures 20E and 21E), allowing a complete image to be seen over a wider range. That is, if the projection light path consists only of backlight module 1 and off-axis dual mirror module 2, the range of the eyebox array extending forward and backward along the Z axis is narrower. When combined with the light-shielding module 4, the formed extended eyebox array has a wider range of extension in the front-to-back direction along the Z axis.

[0126] From a timing perspective, examples of system control switching are shown in Figures 26A to 26D. As shown in Figure 26A, all different display blocks corresponding to the left eye correspond to the same backlight source Led_42, and all different display blocks corresponding to the right eye correspond to the same backlight source Led_62. The control timing is such that, first the parallax image is displayed to the left eye, so the first display block IPS_1 image is switched ON first, then the first switching block TN_1 is switched ON, and finally the backlight source Led_42 is switched ON. At this time, the small eye box EB_V(0,0,0) corresponding to the left eye looks at the image of the first display block IPS_1, and then switches OFF in the reverse order.

[0127] From the moment the image of the first display block IPS_1 starts to switch ON, the image of the second display block IPS_2 switches ON in sequence, followed by the second switching block TN_2, and then the backlight light source Led_42. At this time, the small eye box EB_V(0,0,0) corresponding to the left eye looks at the image of the second display block IPS_2, and then switches OFF in the reverse order.

[0128] After the second display block IPS_2 image starts to switch ON, the third display block IPS_3 image switches ON, then the third switching block TN_3 image switches ON, and finally the backlight light source Led_42 image switches ON in sequence. At this time, the small eye box EB_V(0,0,0) corresponding to the left eye looks at the image of the third display block IPS_3 and switches OFF in the reverse order.

[0129] When the observer is viewing the parallax image with their left eye, the corresponding switching block switches ON after the display block switches ON, and the corresponding display block starts to switch OFF after the switching block switches OFF. The backlight source Led_42 illuminates the entire display 3, but the switching block blocks out the display block being converted or the display block that is not being displayed, so the observer does not see the afterimage of the display block being converted. Also, when displaying the parallax image to the left eye, only the backlight source Led_42 corresponding to the left eye lights up, and when displaying the parallax image to the right eye, only the backlight source Led_62 corresponding to the right eye lights up, so the left and right eyes do not see each other's parallax images, and no crosstalk occurs. The backlight beam penetration time for each display block is controlled to be the same, and the brightness of the entire screen is adjusted to be uniform.

[0130] As shown in Figure 26B, to increase the brightness of the image observed by the human eye, the time it takes for the backlight light source to penetrate the display block can be increased by synchronously lengthening the time it takes for the switching block in Figure 26A to switch ON and the time it takes for the backlight light source to switch ON, thereby improving brightness. In other words, the brightness of the image can be changed by changing the length of the projection time of the light from the display block. The longer the display time for the backlight light source to pass through the display block, the brighter the image becomes, and the shorter the display time for the backlight light source to pass through the display block, the lower the image brightness becomes. Here, there is no temporal overlap between each switching block, and this is applicable when the display blocks correspond to the same backlight light source or to different backlight light sources. The backlight beam penetration time for each display block is controlled to be the same, and the brightness of the entire image is adjusted to be uniform.

[0131] As shown in Figure 26C, if all display blocks of the same eye correspond to the same backlight source, in order to further improve the brightness of the image, the time it takes for the switching block to turn ON is extended, the switching block is turned ON after the display block has turned ON, the switching block is turned OFF just before the display block has turned OFF, the backlight source is turned on simultaneously with the first switching block TN_1 turning ON, and is turned off only when the third switching block turns OFF. The backlight beam penetration time for each display block is controlled to be the same, and the brightness of the entire image is adjusted to be uniform.

[0132] As shown in Figure 26D, if all display blocks of the same eye correspond to different backlight sources, each backlight source changes the brightness of the image by either turning on the backlight source for the entire duration that the corresponding switching block is on, or turning on the backlight source for a partial duration that the corresponding switching block is on. The longer it takes for the backlight source to pass through the display block, the brighter the image becomes, and the shorter it takes for the backlight source to pass through the display block, the less bright the image becomes. The backlight beam penetration time for each display block is controlled to be the same, so that the brightness of the entire screen is uniform.

[0133] In this way, the afterimage and crosstalk problems of naked-eye stereoscopic image display devices can be effectively resolved, reducing the likelihood of causing dizziness in the observer and improving the quality of the observed image.

[0134] By combining all of the above technical features, this system improves upon the problems faced by conventional glasses-free stereoscopic image display devices, eliminates afterimages and crosstalk, enhances image brightness, equalizes screen brightness, avoids image flicker, and expands the visible area, thereby realizing a glasses-free stereoscopic image display device that best meets the requirements of moving objects such as vehicles, ships, and aircraft. [Explanation of symbols]

[0135] [Conventional technology] 01 Backlight source 03 Display Panel 5. Concave imaging mirror 6. Eye-tracking module 61 Control and calculation module 7. Imaging semi-reflecting mirror G_im Image (Virtual Image) B Directional backlight beam D Directional imaging beam EB iBox EBA eyebox array WS windshield C Combiner E_L Eye position E_R Eye position EB_L Left eye small eye box EB_R Right eye small eye box [The present invention] 1 Backlight Module 1_im Backlight light source virtual image 10 Backlight Light Source Arrays 11. Backlight light source array 10_im Backlight light source array virtual image 10_re Backlight light source array real image 12 Conical Light Cup Array 13 LED 13T Polarizing Lens Array 13L Focusing Lens Array 14. Focusing lens 2-axis off-axis dual mirror module 21 First Mirror 22 Second curved mirror 221 Boundary 3 displays 31 Main display module 32 Lower polarizer 33 Liquid crystal layer 34 Upper polarizer 4. Light-blocking module 42 Lower polarizer 43 Liquid crystal layer 44 Upper polarizer 45 Reflective polarizer 5. Concave imaging mirror 6. Eye-tracking module 61 Control and calculation module 7. Imaging semi-reflecting mirror B Backlight Beam BFP Backlight Focusing Surface D Image beam EB Small Eyebox EB_1, EB_2, EB_3, EB_11~EB144, EB_V Small eyebox EB_1V, EB_2V, EB_3V, EB_123_123V, EB_123_321V Small Eyebox EB_L Small Eyebox EB_R Small Eyebox EBA eyebox array EBA_V Extended iBox Array E_L Left eye position E_L' Left eye position E_R Right eye position E_R' Right eye position G_im Image (Virtual Image) IFP image focal plane IPS_1 display block IPS_2 display block IPS_3 display block IPS_1_im Image virtual image IPS_2_im Image virtual image IPS_3_im Image virtual image Led_1, Led_2, Led_3, Led_11~Led144 Backlight Light Sources LED_L Backlight Light Source LED_R Backlight Light Source MC mirror center MT Small Eyebox - Display Block - Backlight Light Source Matrix Table OA optical axis OCA Optical Adhesive pix_p pixels pix_t pixels TN_1 Switching Block TN_2 Switching Block TN_3 Switching Block

Claims

1. A naked-eye stereoscopic image display device equipped with a segmented backlight suitable for use in combination with an imaging semi-reflecting mirror, A backlight module that includes a backlight source array composed of multiple backlight sources and emits a directional backlight beam, A display comprising a main display module and a light-shielding module that overlap each other, wherein the main display module alternately displays a left-eye parallax image and a right-eye parallax image, and the directional backlight beam forms an image beam after it has passed through, A concave imaging mirror that reflects the aforementioned image beam, Includes, The main display module defines a plurality of display blocks, and the light-shielding module defines a plurality of switching blocks, each of which switching blocks corresponds to one of the display blocks, and when the main display module displays an image, at least one of the switching blocks is selected in a time-division manner, the display block projects the image beam in a time-division manner, and the remaining switching blocks shield the display blocks in the main display module that are still being switched or have not yet been switched. A naked-eye stereoscopic image display device with a segmented backlight, wherein the equivalent distance between the virtual image of the backlight array and the imaging concave mirror is greater than the focal length of the imaging concave mirror, the directional backlight beam is reflected by the imaging concave mirror and the imaging semi-reflector, then projected onto and focused on the backlight focusing surface to form a real image of the backlight array corresponding to the virtual image of the backlight array, each of the backlight sources forms an independent small eyebox, all of the small eyeboxes constitute the real image of the backlight array, and define an eyebox array.

2. The naked-eye stereoscopic image display device with a split backlight according to claim 1, wherein the equivalent distance between the main display module and the imaging concave mirror is smaller than the focal length of the imaging concave mirror, and the left-eye parallax image and the right-eye parallax image form virtual images of the left-eye parallax image and the right-eye parallax image, respectively, on the side of the imaging semi-reflecting mirror away from the eyebox array.

3. The naked-eye stereoscopic image display device with a segmented backlight according to claim 1, wherein the effective area of ​​each small eye box extends to both sides of the backlight focusing surface, and the small eye box gradually shrinks along the front-to-back direction of the backlight focusing surface.

4. When the main display module displays the left-eye parallax image or the right-eye parallax image, at least one of the switching blocks is switched to the display block capable of projecting one of the parallax images, and the remaining switching block shields the display block that displays the other parallax image, as described in claim 1, a naked-eye stereoscopic image display device with a split backlight.

5. The naked-eye stereoscopic image display device with a split backlight according to claim 1, wherein the liquid crystal switching speed of the main display module is slower than the liquid crystal switching speed of the light-shielding module.

6. The naked-eye stereoscopic image display device with a split backlight according to claim 1, wherein the light-receiving side of the main display module overlaps with the light-shielding module.

7. A naked-eye stereoscopic image display device with a split backlight according to claim 1, wherein there is an optical adhesive between the main display module and the light-shielding module, and there is no polarizer between the optical adhesive and the liquid crystal layer of the main display module.

8. A naked-eye stereoscopic image display device with a segmented backlight according to claim 1, wherein there is an optical adhesive between the main display module and the light-shielding module, and there is no polarizer between the optical adhesive and the liquid crystal layer of the light-shielding module.

9. The naked-eye stereoscopic image display device with a segmented backlight according to claim 1, wherein the imaging semi-reflecting mirror is a front glass or a combiner.

10. The naked-eye stereoscopic image display device with a segmented backlight according to claim 1, wherein the length of time the switching block is ON, or the length of time the backlight light source is ON, is controlled to correspond to a preset brightness.

11. A naked-eye stereoscopic image display device with a segmented backlight according to claim 1, wherein at least one of the display blocks projects the image beam in combination with a plurality of different backlight sources, defines a plurality of smaller eye boxes in a separate group outside the space of the eye box array on both sides in the front-to-back direction of the backlight focusing surface, and the plurality of smaller eye boxes in the separate group and the eye box array jointly form an extended eye box array.

12. It further includes an eye-tracking module and a control calculation module, The eye-tracking module detects the relative position information between the left and right eyes and the eye-tracking module, The control calculation module is connected to the backlight module, the display, and the eye-tracking module, and acquires detection information from the eye-tracking module, acquires the left eye position and the right eye position, and after acquiring the left eye sub-eyebox and the right eye sub-eyebox based on the left eye position, the right eye position, and the eyebox array or extended eyebox array, it acquires the corresponding left eye matrix and right eye matrix according to the sub-eyebox-display block-backlight light source matrix table. The naked-eye stereoscopic image display device with a split backlight according to claim 1 or 11, comprising the left-eye matrix and the right-eye matrix, the display block, the switching block and the backlight source, respectively configured to project the image beam of the left-eye parallax image to the left-eye position and the image beam of the right-eye parallax image to the right-eye position.

13. A naked-eye stereoscopic image display device with a split backlight according to claim 11, which corresponds to the amount of eye displacement, wherein the amount of eye displacement includes displacement in a two-dimensional direction or displacement in a three-dimensional direction, by switching between different small eye boxes in the eye box array or the extended eye box array.

14. The naked-eye stereoscopic image display device with a divided backlight according to claim 12, wherein the eye box array or the extended eye box array defines 2n+1 adjacent small eye boxes corresponding to the left eye position or the right eye position, n > 0 and n is a positive integer, the central small eye box among the 2n+1 small eye boxes is aligned with the pupil of one eye, and the other 2n small eye boxes are distributed above and below or to the left and right of the central small eye box.

15. A naked-eye stereoscopic image display device with a split backlight according to claim 12, wherein the switching interval time for each of the display blocks of the main display module to project the image beam to the same eye position is shorter than 41.67 ms.

Images