Display device

Abstract

To enhance the reliability of a display device that displays a three dimentional image.SOLUTION: A display device 10 includes: a first irradiation unit 12 configured to irradiate a first drawing light 18 toward a drawing space 50 and change a first condensing position 28 where the first drawing light 18 is condensed in three dimensions; a second irradiation unit 14 configured to irradiate a second drawing light 20 toward the drawing space 50 from a position opposite the first drawing light 18 and change a second condensing position 30 where the second drawing light 20 is condensed in three dimensions; and a control unit 16 for controlling the first condensing position 28 and the second condensing position 30 so that the relative positions of the first condensing position 28 and the second condensing position 30 satisfy a predetermined condition.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a display device. [Background technology]

[0002] There is a method for generating a three-dimensional image within a display body by irradiating a display body containing a phosphor with excitation light and scanning the focusing position of the excitation light. For example, a configuration has been proposed in which excitation light is irradiated from above and below the display body using multiple irradiation units to improve display accuracy (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-128246 Summary of the Invention [Problem to be solved by the invention]

[0004] When two irradiation units are arranged opposite each other, there is a possibility that light from one irradiation unit may directly enter the inside of the other irradiation unit as stray light, and the incidence of stray light may cause damage to the irradiation unit.

[0005] The present invention has been made in view of the above circumstances, and has an object to provide a technique for improving the reliability of a display device that displays a stereoscopic image. [Means for solving the problem]

[0006] A display device according to one embodiment of the present invention includes a first irradiation unit configured to irradiate a first drawing light toward a drawing space and change a first focusing position where the first drawing light is focused in three dimensions, a second irradiation unit configured to irradiate a second drawing light toward the drawing space from a position opposite the first drawing light and change a second focusing position where the second drawing light is focused in three dimensions, and a control unit that controls the first focusing position and the second focusing position so that the relative positions of the first focusing position and the second focusing position satisfy a predetermined condition.

[0007] Any combination of the above components or mutual substitution of the components or expressions of the present invention between methods, devices, systems, etc. are also valid aspects of the present invention. [Effects of the Invention]

[0008] According to the present invention, the reliability of a display device that displays a stereoscopic image can be improved. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram schematically illustrating a configuration of a display device according to an embodiment. [Figure 2] 3A and 3B are diagrams schematically showing examples of combinations of first coordinate values ​​and second coordinate values. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Specific numerical values ​​and the like shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. Elements not directly related to the present invention are omitted from the drawings. To facilitate understanding of the description, the dimensional ratios of the components in the drawings do not necessarily correspond to the actual dimensional ratios.

[0011] 1 is a diagram schematically illustrating the configuration of a display device 10 according to an embodiment. The display device 10 includes a first irradiating unit 12, a second irradiating unit 14, and a control unit 16. The display device 10 is a so-called volumetric display, and is configured to generate a three-dimensional image 52 in a rendering space 50 located between the first irradiating unit 12 and the second irradiating unit 14.

[0012] The three-dimensional image 52 is composed of a collection of multiple bright spots (or voxels) 54 generated at different three-dimensional positions in a drawing space 50, which is a predetermined space where drawing is performed. Here, the light for generating the bright spots 54 in the drawing space 50 is referred to as drawing light. The multiple bright spots 54 are generated by a first drawing light 18 irradiated from the first irradiator 12 toward the drawing space 50 and a second drawing light 20 irradiated from the second irradiator 14 toward the drawing space 50. Here, the position where the drawing light is focused is referred to as a focusing position. For example, if the first drawing light 18 and the second drawing light 20 are femtosecond lasers, plasma can be generated at the focusing position of the first drawing light 18 or the second drawing light 20 to generate the bright spots 54. In this case, a gas (e.g., air) that serves as a plasma generation source is present in the drawing space 50.

[0013] The multiple bright spots 54 may be generated by light emission from a phosphor instead of by light emission from plasma. In this case, a phosphor may be disposed in the drawing space 50, and the multiple bright spots 54 may be generated by exciting the phosphor with the first drawing light 18 or the second drawing light 20. For example, a display body made of transparent glass or resin containing a phosphor may be disposed in the drawing space 50, and the display body may be irradiated with the first drawing light 18 and the second drawing light 20, thereby generating the multiple bright spots 54 inside the display body and drawing the three-dimensional image 52.

[0014] The first irradiator 12 irradiates the drawing space 50 with a first drawing light 18. The second irradiator 14 irradiates the drawing space 50 with a second drawing light 20. The first irradiator 12 and the second irradiator 14 are arranged to face each other across the drawing space 50. The first drawing light 18 and the second drawing light 20 enter the drawing space 50 from positions facing each other.

[0015] In FIG. 1, the direction from the first irradiating unit 12 to the second irradiating unit 14 is the +z direction, and the directions along a plane perpendicular to the z direction are the x and y directions. Here, the direction in which the drawing light is irradiated is referred to as the irradiation direction. Also, the direction along a plane perpendicular to the irradiation direction is referred to as the in-plane direction. The irradiation direction of the first drawing light 18 toward the drawing space 50 is, for example, the +z direction. The irradiation direction of the second drawing light 20 toward the drawing space 50 is, for example, the -z direction. The in-plane directions are, for example, the x and y directions.

[0016] The drawing space 50 can be defined as, for example, an area in which a bright spot 54 can be generated by the first drawing light 18 or the second drawing light 20. In Fig. 1, the outline of the drawing space 50 is schematically shown by a dashed line, but the outline of the drawing space 50 does not need to be clearly defined. The shape of the outline of the drawing space 50 is not particularly limited.

[0017] The first irradiation unit 12 includes a first light source 22, a first focus adjustment unit 24, and a first scanning unit .

[0018] First light source 22 generates first drawing light 18. First light source 22 generates, as first drawing light 18, an ultrashort pulse laser having a pulse width of, for example, picoseconds or femtoseconds (e.g., 10 fs or more and 100 ps or less). The wavelength of first drawing light 18 is not particularly limited and may be in the infrared wavelength range of approximately 800 nm to 1500 nm, the visible wavelength range of approximately 400 nm to 800 nm, or the ultraviolet wavelength range of approximately 200 nm to 400 nm. The pulse energy of first drawing light 18 is set, for example, to be approximately 1 μJ to 1 mJ so that plasma can be generated at first focusing position 28 where first drawing light 18 is focused.

[0019] The first focus adjustment unit 24 is configured to adjust the focus of the first drawing light 18 and change the z coordinate of the first focusing position 28. The first focus adjustment unit 24 includes, for example, a variable focus lens, and adjusts the focus of the first focusing position 28 by changing the refractive power. Instead of a variable focus lens, the first focus adjustment unit 24 may use a zoom lens configured to be displaceable along the optical path.

[0020] The first scanning unit 26 is configured to two-dimensionally scan the first drawing light 18 and change the x and y coordinates of the first focusing position 28. The first scanning unit 26 includes a galvanometer mirror or a MEMS (Micro Electro Mechanical Systems) mirror that can change the orientation of the mirror that reflects the first drawing light 18. The first scanning unit 26 is configured, for example, to change the orientation of the mirror along two axes, and changes the first focusing position 28 of the first drawing light 18 reflected by the mirror in the x and y directions. The first scanning unit 26 may include a mirror for scanning the first drawing light 18 in the x direction and a mirror for scanning the first drawing light 18 in the y direction.

[0021] The second irradiation unit 14 includes a second light source 32, a second focus adjustment unit 34, and a second scanning unit 36. The second irradiation unit 14 can be configured similarly to the first irradiation unit 12.

[0022] The second light source 32 generates the second drawing light 20. The second light source 32 can be configured similarly to the first light source 22, and can generate the second drawing light 20 having the same characteristics (e.g., wavelength, pulse width, pulse energy) as the first drawing light 18. The second light source 32 generates the second drawing light 20 such that plasma can be generated at the second focusing position 30 where the second drawing light 20 is focused. The second light source 32 may generate the second drawing light 20 having characteristics different from those of the first drawing light 18.

[0023] The second focus adjustment unit 34 is configured to adjust the focus of the second drawing light 20 and change the z coordinate of the second light condensing position 30. The second focus adjustment unit 34 can be configured similarly to the first focus adjustment unit 24.

[0024] The second scanning unit 36 ​​is configured to two-dimensionally scan the second drawing light 20 and change the x and y coordinates of the second light condensing position 30. The second scanning unit 36 ​​can be configured similarly to the first scanning unit 26.

[0025] The display device 10 may further include a first drawing lens 38 disposed between the first irradiating unit 12 and the drawing space 50, and a second drawing lens 40 disposed between the second irradiating unit 14 and the drawing space 50. Note that the first drawing lens 38 and the second drawing lens 40 may be omitted.

[0026] The first drawing lens 38 focuses the first drawing light 18 scanned by the first scanning unit 26 toward the drawing space 50. The first drawing lens 38 may be formed of, for example, a convex lens with fixed refractive power. The first drawing lens 38 may have the role of improving the telecentricity of the first drawing light 18 scanned by the first scanning unit 26.

[0027] The second drawing lens 40 focuses the second drawing light 20 scanned by the second scanning unit 36 ​​toward the drawing space 50. The second drawing lens 40 may be formed of, for example, a convex lens with fixed refractive power. The second drawing lens 40 may have a role of improving the telecentricity of the second drawing light 20 scanned by the second scanning unit 36.

[0028] The first drawing lens 38 and the second drawing lens 40 can be arranged, for example, on a common optical axis 56. For example, the optical axes of the first drawing lens 38 and the second drawing lens 40 can be aligned with the optical axis 56 extending in the z direction from the first irradiation unit 12 (e.g., the first scanning unit 26) toward the second irradiation unit 14 (e.g., the second scanning unit 36).

[0029] The control unit 16 controls the overall operation of the display device 10. The various functions provided by the control unit 16 can be realized, for example, by a combination of hardware and software. The hardware of the control unit 16 is realized by elements and mechanical devices such as a processor and memory provided in a computer. The software of the control unit 16 is realized by a program executed by a processor, etc.

[0030] The control unit 16 controls the operations of the first irradiating unit 12 and the second irradiating unit 14, and variably controls the first focusing position 28 and the second focusing position 30. The control unit 16 includes a first control unit 42, a second control unit 44, a point cloud data generating unit 46, and a drawing data generating unit 48.

[0031] The first control unit 42 controls the operation of the first irradiator 12. The first control unit 42 controls the first focusing position 28 in three dimensions by controlling the operation of the first focus adjuster 24 and the first scanner 26. Here, the three-dimensional coordinate of the first focusing position 28 is referred to as the first coordinate value. The first control unit 42 determines operating parameters indicating the refractive power of the first focus adjuster 24 and the scanning angle of the first scanner 26 (e.g., the mirror angles in the x and y directions) according to the first coordinate value, and operates the first focus adjuster 24 and the first scanner 26 according to the determined operating parameters. The values ​​of the operating parameters according to the first coordinate value can be determined in advance according to the design of the optical system of the first irradiator 12 and the first drawing lens 38. For example, the first control unit 42 sequentially switches the values ​​of the operating parameters of the first focus adjustment unit 24 and the first scanning unit 26 in accordance with the time-series data of the first coordinate values, thereby sequentially focusing the first drawing light 18 at each of the multiple first focusing positions 28 to generate bright spots 54. Here, the time-series data of the first coordinate values ​​is data including the first coordinate values ​​at a predetermined time and the first coordinate values ​​at times different from the predetermined time.

[0032] The second control unit 44 controls the operation of the second irradiator 14. The second control unit 44 can be configured similarly to the first control unit 42. The second control unit 44 controls the second focusing position 30 in three dimensions by controlling the operation of the second focus adjuster 34 and the second scanner 36. Here, the three-dimensional coordinate of the second focusing position 30 is referred to as the second coordinate value. The second control unit 44 determines operating parameters indicating the refractive power of the second focus adjuster 34 and the scanning angle of the second scanner 36 (e.g., the mirror angles in the x and y directions) in accordance with the second coordinate value, and operates the second focus adjuster 34 and the second scanner 36 in accordance with the determined operating parameters. The values ​​of the operating parameters corresponding to the second coordinate value can be determined in advance depending on the design of the optical system of the second irradiator 14 and the second drawing lens 40. The second control unit 44 sequentially switches the values ​​of the operating parameters of the second focus adjustment unit 34 and the second scanning unit 36 ​​in accordance with the time series data of the second coordinate values, for example, to sequentially focus the second drawing light 20 at each of the multiple second focusing positions 30, thereby generating bright spots 54. Here, the time series data of the second coordinate values ​​is data including second coordinate values ​​at a predetermined time and second coordinate values ​​at times different from the predetermined time.

[0033] The point cloud data generation unit 46 generates point cloud data indicating the three-dimensional coordinate values ​​of a plurality of bright points 54 that constitute the three-dimensional image 52 to be displayed. The point cloud data generation unit 46 generates the point cloud data based on three-dimensional data of the three-dimensional image 52 provided, for example, from an external device (not shown). The point cloud data indicates, for example, a plurality of coordinate values ​​for drawing the contour of the three-dimensional image 52. The point cloud data generation unit 46 may generate point cloud data corresponding to a plurality of frames in order to draw the three-dimensional image 52 as a moving image. The point cloud data generation unit 46 may also acquire the point cloud data of the three-dimensional image 52 provided from an external device (not shown).

[0034] The drawing data generation unit 48 generates drawing data indicating a combination of first coordinate values ​​and second coordinate values ​​from the point cloud data generated by the point cloud data generation unit 46. The drawing data indicates a combination of three-dimensional coordinate values ​​of the first focusing position 28 and the second focusing position 30 to be drawn at a predetermined timing. The drawing data includes time-series data of the combination of the first coordinate values ​​and the second coordinate values.

[0035] The drawing data generation unit 48 separates the multiple coordinate values ​​included in the point cloud data into first coordinate values ​​and second coordinate values. In other words, the drawing data generation unit 48 separates the multiple bright spots 54 for generating the 3D image 52 into bright spots 54 generated at the first focusing position 28 and bright spots 54 generated at the second focusing position 30. The drawing data generation unit 48 separates the multiple coordinate values ​​so that the number of first coordinate values ​​is equal to the number of second coordinate values. The drawing data generation unit 48 can separate the multiple coordinate values ​​according to the coordinate values. For example, the drawing data generation unit 48 can divide the drawing space 50 into a first region and a second region and define coordinate values ​​present in the first region as first coordinate values ​​and coordinate values ​​present in the second region as second coordinate values.

[0036] The drawing data generation unit 48 determines a combination of the first light focusing position 28 and the second light focusing position 30 to be drawn at a predetermined timing based on the separated first coordinate value and second coordinate value. Here, the relative positional relationship between the first light focusing position 28 and the second light focusing position 30 and the relative positional relationship between the first coordinate value and the second coordinate value are referred to as relative positions. The drawing data generation unit 48 generates drawing data so that the relative positions of the first coordinate value and the second coordinate value combined at the predetermined irradiation timing satisfy predetermined conditions. The drawing data generation unit 48 determines the combination of the first coordinate value and the second coordinate value so that the first drawing light 18 does not directly enter the inside of the second irradiation unit 14 (e.g., the second scanning unit 36) and the second drawing light 20 does not directly enter the inside of the first irradiation unit 12 (e.g., the first scanning unit 26). The drawing data generation unit 48 may set the first timing for irradiating the first focus position 28 and the second timing for irradiating the second focus position 30 to be the same timing. The drawing data generation unit 48 may set the first timing for irradiating the first focus position 28 and the second timing for irradiating the second focus position 30 to be timings that fall within a predetermined time interval.

[0037] The drawing data generation unit 48 may determine a combination of the first coordinate value and the second coordinate value so that the distance between the first coordinate value and the second coordinate value in an in-plane direction (e.g., the x direction and the y direction) is equal to or greater than a predetermined threshold. Here, the predetermined threshold can be determined in advance according to the design of the optical system of the display device 10 so that the first drawing light 18 passing through the first focusing position 28 does not directly enter the inside of the second irradiator 14 (e.g., the second scanning unit 36) and the second drawing light 20 passing through the second focusing position 30 does not directly enter the inside of the first irradiator 12 (e.g., the first scanning unit 26). The predetermined threshold can be set appropriately according to optical parameters such as the beam size, numerical aperture (NA), effective aperture (clear aperture), F-number, and telecentricity of the first irradiator 12 and the second irradiator 14. The drawing data generation unit 48 may store the predetermined threshold. The drawing data generation unit 48 may determine a combination of the first coordinate value and the second coordinate value so that the relative position indicated by the in-plane distance between the first coordinate value and the second coordinate value is equal to or greater than a predetermined threshold value, and generate drawing data.

[0038] The drawing data generation unit 48 may generate drawing data so that the distance between the first focus position 28 and the second focus position 30 is equal to or greater than a predetermined threshold. The drawing data generation unit 48 may generate drawing data at a predetermined timing so that the distance between the first focus position 28 and the second focus position 30 is equal to or greater than a predetermined threshold. The drawing data generation unit 48 may change the combination of the first coordinate value and the second coordinate value of the generated drawing data while maintaining the distance between the first focus position 28 and the second focus position 30 at a predetermined timing so that it is equal to or greater than the predetermined threshold.

[0039] FIG. 2 is a diagram illustrating an example of a combination of first and second coordinate values. FIG. 2 shows the drawing space 50 as viewed along the optical axis 56. A dashed line 64 indicates a range within which the distance from a first coordinate value 60 in the in-plane directions (x and y directions) is equal to or greater than a predetermined threshold value r. FIG. 2 also illustrates two second coordinate values ​​62a and 62b. One of the second coordinate values ​​62a can be combined with the first coordinate value 60 because the distance ra from the first coordinate value 60 in the in-plane direction is equal to or greater than the predetermined threshold value r. The other second coordinate value 62b cannot be combined with the first coordinate value 60 because the distance rb from the first coordinate value 60 in the in-plane direction is less than the predetermined threshold value r. In the example of FIG. 2, the positions of the first coordinate value 60 and the second coordinate values ​​62a and 62b in the irradiation direction (e.g., the z direction) need not be considered. The drawing data generation unit 48 determines the first and second coordinate values ​​that can be combined.

[0040] The drawing data generation unit 48 may use a fixed value as the predetermined threshold r, or may use a variable value determined depending on at least one of the first coordinate value and the second coordinate value. For example, the drawing data generation unit 48 may use a predetermined threshold r that varies depending on either the x-component or the y-component of the first coordinate value or the x-component or the y-component of the second coordinate value. For example, the drawing data generation unit 48 may increase the predetermined threshold r as the first coordinate value or the second coordinate value is closer to the optical axis 56. This is because, when the first condensing position 28 or the second condensing position 30 is closer to the optical axis 56, the drawing light is more likely to be directly incident on the opposing irradiation unit. On the other hand, the drawing data generation unit 48 may decrease the predetermined threshold r as the first coordinate value or the second coordinate value is farther from the optical axis 56. This is because, when the first condensing position 28 or the second condensing position 30 is farther from the optical axis 56, the drawing light is tilted with respect to the optical axis 56, making it difficult for the drawing light to be directly incident on the opposing irradiation unit. For example, the drawing data generating unit 48 may set a predetermined threshold value r as a function of the distance from the optical axis 56 to the first coordinate value or the second coordinate value.

[0041] The marking data generation unit 48 may use a predetermined threshold value r that varies depending on the z-component of the first coordinate value or the z-component of the second coordinate value. For example, the marking data generation unit 48 may use a threshold value r that varies depending on the first numerical aperture of the first irradiator 12 that varies depending on the z-component of the coordinate of the first focusing position 28 and the second numerical aperture of the second irradiator 14 that varies depending on the z-component of the coordinate of the second focusing position 30. For example, the marking data generation unit 48 may increase the predetermined threshold value r as the first numerical aperture increases because the first focusing position 28 is closer to the first irradiator 12. For example, the marking data generation unit 48 may increase the predetermined threshold value r as the second numerical aperture increases because the second focusing position 30 is closer to the second irradiator 14. This is because, when the numerical aperture is large, the beam size of the marking light after passing through the focusing position becomes relatively large, making it more likely to be directly incident on the opposing irradiator. On the other hand, the drawing data generation unit 48 may set the predetermined threshold value r smaller, for example, as the first condensing position 28 is farther from the first irradiator 12 and the first numerical aperture becomes smaller. The drawing data generation unit 48 may set the predetermined threshold value r smaller, for example, as the second condensing position 30 is farther from the second irradiator 14 and the second numerical aperture becomes smaller. This is because, when the numerical aperture is small, the beam size of the drawing light after passing the condensing position becomes relatively small, making it difficult for the drawing light to directly enter the opposing irradiator. For example, the drawing data generation unit 48 may set the predetermined threshold value r as a function of the z-component of the first coordinate value or the z-component of the second coordinate value.

[0042] The first control unit 42 can control the operation of the first irradiation unit 12 according to the time-series data of the first coordinate values ​​included in the drawing data. The second control unit 44 can control the operation of the second irradiation unit 14 according to the time-series data of the second coordinate values ​​included in the drawing data. The drawing data is configured so that the relative positions of the first coordinate values ​​and the second coordinate values ​​at a predetermined timing satisfy a predetermined condition, so that the relative positions of the first focus position 28 and the second focus position 30 at a predetermined timing also satisfy the predetermined condition. In other words, the control unit 16, including the first control unit 42 and the second control unit 44, controls the first focus position 28 and the second focus position 30 according to drawing data in which the relative positions of the first focus position 28 and the second focus position 30 combined at a predetermined timing of irradiation satisfy the predetermined condition. As a result, even when the first irradiation unit 12 and the second irradiation unit 14 are arranged opposite each other, the first drawing light 18 can be prevented from directly entering the interior of the second irradiation unit 14 (e.g., the second scanning unit 36), and the second drawing light 20 can be prevented from directly entering the interior of the first irradiation unit 12 (e.g., the first scanning unit 26).

[0043] According to this embodiment, it is possible to prevent damage to the internal optical system of the first irradiator 12 or the second irradiator 14 caused by the drawing light directly incident from the opposing position, thereby improving the reliability of the display device 10. Furthermore, by arranging the first irradiator 12 and the second irradiator 14 opposite each other, it is possible to limit the irradiation direction of the drawing light to a direction along the optical axis 56. As a result, when the three-dimensional image 52 is observed from around the optical axis 56, it is possible to prevent the drawing light from being directed toward the observer, thereby improving safety. Furthermore, by using the first irradiator 12 and the second irradiator 14 in combination, it is possible to increase the number of drawn bright spots 54 per unit time, thereby improving the display accuracy of the three-dimensional image 52.

[0044] The present invention has been described above with reference to the above-mentioned embodiments, but the present invention is not limited to the above-mentioned embodiments, and appropriate combinations or substitutions of the configurations shown in each display example are also included in the present invention. [Explanation of symbols]

[0045] 10...display device, 12...first irradiation section, 14...second irradiation section, 16...control section, 18...first drawing light, 20...second drawing light, 28...first focusing position, 30...second focusing position.

Claims

1. a first irradiating unit configured to irradiate a first drawing light toward a drawing space and to change a first light condensing position at which the first drawing light is condensed in three dimensions; a second irradiating unit configured to irradiate the drawing space with second drawing light from a position opposite to the first drawing light, and to three-dimensionally change a second light condensing position at which the second drawing light is condensed; a control unit that controls the first and second focusing positions so that the relative positions of the first and second focusing positions satisfy a predetermined condition. Display device.

2. the control unit generates drawing data of a combination of first coordinate values ​​indicating the first focusing position and second coordinate values ​​indicating the second focusing position, and controls operations of the first irradiation unit and the second irradiation unit in accordance with the drawing data; the drawing data is generated so that the relative positions of the first coordinate values ​​and the second coordinate values ​​combined at a predetermined timing of irradiation satisfy the predetermined condition. The display device according to claim 1 .

3. the predetermined condition is a condition that the first drawing light that has passed through the first light collecting position does not directly enter the inside of the second irradiation unit, and the second drawing light that has passed through the second light collecting position does not directly enter the inside of the first irradiation unit.

3. The display device according to claim 1 or 2.

4. the control unit controls the first condensing position and the second condensing position so that a distance between the first condensing position and the second condensing position in an in-plane direction perpendicular to an irradiation direction of the first drawing light or the second drawing light is equal to or greater than a predetermined threshold.

3. The display device according to claim 1 or 2.

5. the control unit varies the predetermined threshold value depending on coordinate values ​​of at least one of the first light-focus position and the second light-focus position. The display device according to claim 4 .

Images