JP7580177B2 - 3D image display device - Google Patents

Description

The present invention relates to a three-dimensional image display device that displays a three-dimensional image by superimposing a group of elemental images made up of elemental images on an integral pattern image.

A wide variety of 3D image display methods are known, including the twin-eye method using 3D glasses. Among them, the integral method has been proposed as a type of light field display that reproduces 3D images by light reproduction (for example, Non-Patent Document 1).

This integral method places a lens array made up of many tiny lenses in front of the display device, allowing it to reproduce natural 3D images with horizontal and vertical parallax. One issue with this integral method is that it is known to be difficult to reproduce high-pixel, high-density 3D images, since the maximum number of pixels in the 3D image is the same as the number of lenses in the lens array.

Generally, the maximum number of pixels in a 3D image is about one hundredth of the number of pixels in the display device. To solve this problem, a conventional technique has been proposed in which multiple display devices are tiled (arranged) (for example, Patent Document 1). With this conventional technique, the number of pixels and display size of a 3D image increase in proportion to the number of display devices. A conventional technique has also been proposed in which 3D images are optically synthesized from multiple display devices (for example, Non-Patent Document 2). With this conventional technique, the number of pixels and pixel density of a 3D image increase in proportion to the number of display devices.

JP 2018-180387 A

Applied Optics, Vol. 45, No. 18, June 2006 IEEE Lasers and Electro-Optics Society Annual Meeting, paper TuW3, Oct. 2007

However, the above-mentioned conventional technology has the problem that the configuration becomes larger and more complex in proportion to the number of display devices. For example, the above-mentioned conventional technology assumes that the number of pixels and pixel density will be improved by about 2 to 4 times by using about 2 to 4 display devices, and it is not practical to increase the number of display devices beyond that.

Therefore, the objective of the present invention is to provide a 3D image display device that has a simple configuration and increases the number of pixels.

To solve the above problems, the three-dimensional image display device according to the present invention is a three-dimensional image display device that displays a three-dimensional image by superimposing an elemental image group made up of elemental images and an integral type pattern image, and is configured to include a storage means, an elemental image group display means, a pattern image display means, and a superimposing means.

According to this configuration, the storage means pre-stores an element image group and a pattern image that minimizes the error between the luminance of the light ray group when the element image group and the pattern image are superimposed and the luminance of the light ray group when a desired three-dimensional image is displayed. Furthermore, the element image group display means displays the element image group stored in the storage means. Then, the pattern image display means displays the pattern image stored in the storage means. Furthermore, the superimposition means superimposes the element image group displayed by the element image group display means and the pattern image displayed by the pattern image display means.

In this way, the 3D image display device superimposes the element image group and the pattern image, thereby increasing the number of pixels of the 3D image to the same level as the pattern image display means. Furthermore, since the 3D image display device does not need to tile the display means, a simple configuration can be realized.

In addition, in order to solve the above-mentioned problems, the three-dimensional image display device of the present invention is a three-dimensional image display device that displays a three-dimensional image by superimposing a group of elemental images made up of elemental images and an integral type pattern image, and is configured to include a memory means, a display means, a first lens array, a second lens array , an image switching means, and a lens array control means .

According to this configuration, the storage means prestores an element image group and a pattern image that minimizes the error between the luminance of the light beam group when the element image group and the pattern image are superimposed and the luminance of the light beam group when a desired three-dimensional image is displayed. The display means displays the element image group or the pattern image stored in the storage means in a time-division manner. The first lens array is composed of first element lenses arranged two-dimensionally, and is switchable between a lens state in which the first element lenses function as convex lenses and a transmission state in which the first element lenses transmit incident light without refracting it . The second lens array is composed of second element lenses arranged two-dimensionally with a lens pitch smaller than that of the first lens array, and is switchable between a lens state in which the second element lenses function as convex lenses and a transmission state in which the second element lenses transmit incident light without refracting it . The image switching means switches the element image group or the pattern image to be displayed on the display means. The lens array control means sets the first lens array in a lens state and the second lens array in a transparent state when the display means displays the elemental image group, and sets the first lens array in a transparent state and the second lens array in a lens state when the display means displays the pattern image.

In this way, the 3D image display device displays the element image group and the pattern image in a time-division manner, thereby increasing the number of pixels of the 3D image to the same level as that of the second lens array. Furthermore, since the 3D image display device does not require tiling of the display means, a simple configuration can be realized.

The present invention provides a three-dimensional image display device with a simple configuration and improved pixel count.

5A to 5C are diagrams illustrating the superposition of an elemental image group and a light beam group of a pattern image in the first embodiment. 5 is an explanatory diagram illustrating luminance values when an elemental image group and a light ray group of a pattern image are superimposed in the first embodiment. FIG. 5 is a flowchart showing a procedure for generating an element image group and a pattern video in the first embodiment. 1 is a block diagram showing a configuration of a three-dimensional image display device according to a first embodiment. FIG. 11 is a block diagram showing a configuration of a three-dimensional image display device according to a second embodiment. 13 is an explanatory diagram illustrating luminance values when an elemental image group and a light ray group of a pattern image are superimposed in the second embodiment. FIG. FIG. 11 is a block diagram showing a configuration of a three-dimensional image display device according to a third embodiment. In the third embodiment, (a) is an explanatory diagram for explaining a lens state, and (b) is an explanatory diagram for explaining a transmission state. FIG. 13 is a block diagram showing a configuration of a three-dimensional image display device according to a fourth embodiment. FIG. 13A is an explanatory diagram of the fourth embodiment when the second lens array functions as a lens array, and FIG. 13B is an explanatory diagram of the first lens array functions as a lens array.

Each embodiment of the present invention will be described below with reference to the drawings. However, each embodiment described below is intended to embody the technical concept of the present invention, and unless otherwise specified, the present invention is not limited to the following. In addition, the same symbols are used for the same means, and descriptions thereof may be omitted.

First Embodiment
[Principles of increasing pixel count and pixel density]
1 and 2, the principle of improving the number of pixels and pixel density will be described as the premise of the three-dimensional image display device 1 (FIG. 4). For simplicity, only the horizontal direction (x-axis direction) will be described, but the same applies to the vertical direction (y-axis direction).

First, the light beams of the integral type elemental image group will be described. In FIG. 1, in order to simplify the description, the light beams passing through one elemental lens constituting the first lens array 92 are illustrated. As shown in FIG. 1(a), in the integral type stereoscopic display device 90, the first lens array 92 is arranged in front of the first display device 91 that displays the elemental image group, with a focal length f ₁ therebetween. At this time, the light beams from the pixel A of the elemental image group displayed on the first display device 91 are refracted by the facing first lens array 92 and reproduced as parallel light. Here, the angle θ ₁ is the angle formed by the line segment from the pixel A to the lens center C ₁ and the display surface of the first display device 91. This angle θ ₁ is equal to the travel angle of the reproduced parallel light beams. The luminance value of the reproduced parallel light beams is I ₁ (A). The luminance value I ₁ (A) depends on the luminance value of the pixel A of the elemental image group.

Next, the light beam of the pattern image will be described. As shown in FIG. 1B, when the pattern image is displayed, a second lens array 94 is arranged in front of the second display device 93 that displays the pattern image, with a focal length _f2 between them. Here, the lens pitch of the second lens array 94 is smaller than that of the first lens array 92, and is set to, for example, 1/4 of the lens pitch of the first lens array 92 (lens density is four times in one direction). At this time, the light beam from pixel _B of the pattern image displayed on the second display device 93 is refracted by the facing second lens array 94 and reproduced as parallel light. Here, the angle θ2 is the angle formed by the line segment from pixel B to the lens center _C2 and the display surface of the second display device 93. This angle _θ2 is equal to the traveling angle of the reproduced parallel light beam. The luminance value of the reproduced parallel light beam is _I2 (B). The luminance value _I2 (B) depends on the luminance value of pixel B of the pattern image.

The integral type pattern image has the same structure as a general integral type element image group. In other words, the pattern image is a two-dimensional array of element images corresponding to each element lens of the second lens array 94. However, unlike the integral type element image group, the pattern image is an image for optimizing errors, which will be described later, and therefore may not form a three-dimensional image even if displayed alone.

Based on the above definitions, the light beams obtained when the reconstructed light beams in Fig. 1(a) and (b) are superimposed by optical synthesis or time division are shown in Fig. 1(c). The distance between the first lens array 92 in Fig. 1(a) and the second lens array 94 in Fig. 1(b) is d. Here, consider the luminance value L(B, θ) of the light beam traveling at an angle θ from pixel B of the second display device 93. Note that the function L(B, θ) is a scalar function that has two variables as arguments and returns a luminance value. When θ= _θ1 = _θ2 , the traveling angle of this light beam is the same as that of the parallel light beam in Fig. 1(a), so the luminance value L(B, θ) of the superimposed light beam can be expressed as _I1 (A)+ _I2 (B).

Although one light ray has been described above, based on the same principle, the luminance value L(x, θ) of the light ray group when the integral type element image group and the pattern image are superimposed can be obtained at all positions x and angles θ. The desired 3D image can be reproduced by optimizing the luminance values of the element image group and the pattern image so that the error between the luminance value _L (x, θ) of all the light rays and the luminance value Lt(x, θ) of the light ray group of the 3D image to be actually reproduced is minimized. However, the function _Lt (x, θ) is a scalar function that has two variables as arguments and returns a luminance value.

Note that the luminance value _Lt (x, θ) of the ray group of the 3D image to be actually reproduced can be the luminance value of the ray group of the multi-viewpoint image. In addition, in 3DCG, the luminance value may be obtained for each ray by ray tracing.

A method for calculating the luminance values of the elemental image group and the pattern image will be described below. As shown in FIG. 2, the display surface of the second display device 93 for the pattern image is on the x-axis, and the first lens array 92 for the elemental image group is spaced a distance d from the second lens array 94. The first lens array 92 is spaced from the first display device 91 by the focal length f ₁ of the first lens array 92. The second lens array 94 is spaced from the second display device 93 by the focal length f ₂ of the second lens array 94. The second display device 93 and the second lens array 94 are located in front of the first display device 91 and the first lens array 92. The left ends of the first display device 91, the first lens array 92, the second display device 93, and the second lens array 94 are in contact with the z-axis in the depth direction. The lens pitches of the first lens array 92 and the second lens array 94 are p ₁ and p ₂ , respectively, and the positions in the z-axis direction are z ₁ and z ₂ , respectively.

Here, the luminance value L(x, θ) when the light ray traveling at an angle θ from the position x of the second display device 93 that displays the pattern image and the light ray of the elemental image group are superimposed is expressed by the following formula (1).

Here, the lower brackets (square brackets) represent the largest integer that does not exceed the real number in the brackets. The brightness value can be found by solving a minimization problem as shown in the following formula (2) so that the error between the brightness value _L (x, θ) of all light rays and the brightness value Lt(x, θ) of the light ray group of the 3D image to be reproduced is minimized. Note that min is a function that returns the minimum value, and R is the entire range of values that the position x and angle θ can take.

The premise for solving the minimization problem is to fix the luminance values of the integral type elemental image group so that a normal 3D image is displayed. In other words, to reproduce the desired 3D image, only the luminance values of the pattern image are optimized without changing the luminance values of the elemental image group. Specifically, based on equation (2), only the luminance values of the pattern image are calculated using an optimization algorithm such as the least squares method.

In addition, when solving the minimization problem, it is necessary to sample the position x and the angle θ a finite number of times. For example, the position x is sampled at the pixel position of the second display device 93. The range of the position x is set to be the same as the display area of the second display device 93. Also, for example, the angle θ is sampled at the progression angle of a line segment drawn from each pixel position of the first display device 91 toward the lens center _C1 of the first lens array 92. The range of the angle θ is set to be equal to or less than the viewing angle of the first display device 91 and the second display device 93. This range of the angle θ is the same as the viewing angle of the three-dimensional image.

Here, the number of samples for the position x and the angle θ are M and K, respectively. In this case, the luminance value L(x, θ) of all light rays and the luminance value _Lt (x, θ) of the light ray group of the 3D image to be reproduced can each be expressed as a column vector having M×K elements. The squared value of the L2 norm of the difference between these two column vectors can be calculated, and an optimization algorithm such as the least squares method can be applied.

The range of the angle θ can be set, for example, based on the condition that a group of light rays from a pixel of the first display device 91 for the elemental image group are incident on only one elemental lens that faces the pixel among the elemental lenses of the first lens array 92, and are not incident on adjacent elemental lenses. In this case, the range of the angle θ is expressed by the following formula (3), where R = f ₁ /p ₁ = f ₂ /p _2. The angle θ is the deviation angle in the polar coordinate system when the position x is translated to the origin of the xz coordinate system in FIG. 2.

Here, in the integral method, the pixel size of the three-dimensional image displayed by the element image group is the same as the size of the element lens constituting the lens array. In other words, the element lens appears to be filled with a single color from the viewer's perspective. For example, the lens size of the first lens array 92 is 1.0 mm x 1.0 mm, the pixel size of the first display device 91 is 50 μm, and the lens size of the second lens array 94 is 0.25 mm x 0.25 mm. In this case, the pixel size of the three-dimensional image is 1.0 mm x 1.0 mm, independent of the pixel size of the first display device 91. When the pattern image displayed by the second display device 93 is superimposed on the pixels of this element image group, a state in which brightness brightness occurs in 0.25 mm units within one pixel of the three-dimensional image is created. If the minimum area in which this brightness brightness occurs is considered to be the pixel size of the three-dimensional image after superimposition, the pixel size of the three-dimensional image can be considered to be 0.25 mm x 0.25 mm. By using this concept, the number of pixels and the pixel density of an integral type three-dimensional image are improved to approximately the same as the number of lenses and the lens density of the second lens array 94.
It should be noted that as the lens pitch _p2 of the second lens array 94 becomes smaller, the number of pixels and pixel density of the three-dimensional image increases, but the depth range in which the number of pixels and pixel density increase becomes narrower.

[Calculation procedure for luminance values of elemental image group and pattern image]
The procedure for calculating the luminance values of the element image group and the pattern image will be described with reference to FIG.
3, various parameters necessary for calculating the luminance value are set in step S1. For example, these parameters include the distance d between the first lens array 92 and the second lens array 94, the focal lengths _f1 , _{f2 of the first lens array 92 and the second lens array 94, the lens pitches p1, p2 , the} positions _z1 , _z2 in the z-axis direction, the number of pixels and the pixel pitch of the first display device 91 and the second display device 93, and the number N of element lenses onto which the light beam group is incident.

In step S2, the luminance value L _t (x, θ) of the group of light rays of the three-dimensional image that is actually to be reproduced is set.
In step S3, the luminance values of the pixels of the element image group and the pattern image are calculated by a minimization problem based on equation (2). Here, it is possible to calculate only the luminance value of the pattern image without changing the luminance value of the element image group.

[Configuration of 3D image display device]
The configuration of the three-dimensional image display device 1 according to the first embodiment will be described with reference to FIG.
The three-dimensional image display device 1 displays a three-dimensional image by superimposing an elemental image group made up of elemental images and an integral type pattern image. As shown in Fig. 4, the three-dimensional image display device 1 includes a storage means 10, an elemental image group display means 11, a pattern image display means 14, and a superimposing means 17.

The storage means 10 is a storage device such as a memory, a hard disk, or an SSD (Solid State Drive) that stores the elemental image group and the pattern image in advance. The elemental image group and the pattern image are generated in advance according to the above-mentioned principle so as to minimize the error between the brightness of the light ray group when the elemental image group and the pattern image are superimposed and the brightness of the light ray group when the 3D image to be reproduced is displayed.

The elemental image group display means 11 displays the elemental image group stored in the storage means 10 , and includes a first display device 12 and a first lens array 13 .
The first display device 12 is a general display device that displays a group of elemental images. For example, the first display device 12 may be a direct-view display device such as a liquid crystal display or an organic electroluminescence (EL) display.
The first lens array 13 has element lenses 13a corresponding to element images arranged two-dimensionally. For example, the first lens array 13 may be a general integral type array in which convex lenses are arranged vertically and horizontally.

The pattern image display means 14 displays the pattern image stored in the storage means 10 , and includes a second display device 15 and a second lens array 16 .
The second display device 15 is a general display device that displays a pattern image. For example, a direct-view display device similar to the first display device 12 can be used as the second display device 15.
The second lens array 16 is a lens array having a smaller lens pitch than the first lens array 13. For example, the second lens array 16 is, like the first lens array 13, an array of element lenses 16a corresponding to a pattern image arranged two-dimensionally.

The superimposing means 17 superimposes the element image group displayed by the element image group display means 11 and the pattern image displayed by the pattern image display means 14. For example, the superimposing means 17 is a beam splitter that optically combines the element image group and the pattern image. A half mirror can be used as this beam splitter.

Here, the distance between the lens array 13 and the superimposing means 17 is D. Also, the distance between the pattern image display means 14 and the superimposing means 17 is D+d. As shown in FIG. 4, the superimposing means 17 is disposed at an angle of 45 degrees to both the elemental image group display means 11 and the pattern image display means 14. The elemental image group display means 11 is disposed on the right side as viewed by viewer α. The pattern image display means 14 is disposed at the back (upper side of the drawing) as viewed by viewer α, sandwiching the superimposing means 17.

Then, a group of light rays of the elemental image group from the elemental image group display means 11 is reflected by the superimposing means 17, and a group of light rays of the pattern image from the pattern image display means 14 passes through the superimposing means 17, and the group of light rays of the elemental image group and the pattern image are optically combined. Then, the group of light sources optically combined by the superimposing means 17 reaches the naked eye of the viewer α.
That is, since the three-dimensional image display device 1 can realize a configuration equivalent to that shown in FIG. 1(c), it is possible to generate elemental image groups and pattern images according to the above-mentioned principle.

[Action and Effects]
In this way, the three-dimensional image display device 1 superimposes the elemental image group and the pattern image, thereby improving the number of pixels and pixel density of the three-dimensional image to approximately the same as the pattern image display means 14 (more precisely, the number of lenses and lens density of the second lens array 16). Furthermore, the three-dimensional image display device 1 does not require tiling of the display means, and therefore can realize a simple configuration.

Second Embodiment
[Configuration of 3D image display device]
The configuration of a three-dimensional image display device 1B according to the second embodiment will be described with reference to FIG.
The three-dimensional image display device 1B displays a three-dimensional image by superimposing an elemental image group composed of elemental images and an integral type pattern image. As shown in Fig. 5, the three-dimensional image display device 1B includes a display means 20, a first lens array 30, a second lens array 40, and a synchronization control device 50.

The display means 20 is a display device that displays the element image group or pattern video stored in the storage means 51 in a time-division manner. Here, since the display means 20 switches between the element image group or pattern video in a time-division manner, it is preferable that the display means 20 is a display device with a high response speed. In this embodiment, the display means 20 displays the element image group or pattern video in a time-division manner in response to a synchronization signal from the video switching means 52 described below. For example, a direct-view display device similar to the first display device 12 in FIG. 4 can be used as the display means 20.

The first lens array 30 is composed of first lens elements 31 arranged two-dimensionally. The first lens array 30 is a lens/transmission switching lens array that can switch between a lens state and a transmission state in response to a synchronization signal from a lens array control means 53 described later. In this embodiment, the first lens array 30 is separated from the display means 20 by a focal length _f1 of the first lens array 30.

The lens state of the first lens array 30 refers to a state in which each of the first element lenses 31 functions as a convex lens for the light of the element image. The transmission state of the first lens array 30 refers to a state in which each of the first element lenses 31 transmits the light of the element image.

For example, the first lens array 30 can use liquid crystal lenses arranged in a two-dimensional array as the first element lenses 31. Here, the liquid crystal lens has liquid crystal sealed in a lens-shaped space, and can switch between the lens state and the transmission state by changing the effective refractive index according to the applied voltage. The liquid crystal lens may also switch between the lens state and the transmission state by changing the polarization state of the incident light.

The second lens array 40 is composed of second lens elements 41 that are two-dimensionally arranged at a lens pitch smaller than that of the first lens array 30. In this embodiment, the second lens array 40 is spaced from the display means 20 by a focal length _f2 of the second lens array 40. In addition, the lens pitch of the second lens array 40 is ¼ of the lens pitch of the first lens array 30.

The second lens array 40 can switch between a lens state and a transmission state in response to a synchronization signal from the lens array control means 53. For example, the second lens array 40 can be a lens/transmission switching lens array similar to the first lens array 30.

The lens state of the second lens array 40 refers to a state in which each second element lens 41 functions as a convex lens for the light of the pattern image. The transmission state of the second lens array 40 refers to a state in which each second element lens 41 transmits the light of the pattern image.

The synchronization control device 50 synchronizes the display timing of the elemental image group or pattern image with the switching timing of the lens state or transmission state of each of the first lens array 30 and the second lens array 40 on a frame-by-frame basis. As shown in FIG. 5, the synchronization control device 50 includes a storage means 51, an image switching means 52, and a lens array control means 53. For example, the synchronization control device 50 performs switching at a speed (e.g., 120 Hz) at which the viewer α does not perceive flicker.

The storage means 51 stores element image groups and pattern images in advance. This storage means 51 is similar to the storage means 10 in FIG. 4, so further explanation is omitted.

The image switching means 52 switches between the element image group or pattern image stored in the storage means 51 and displays them in a time-division manner on the display means 20. Specifically, the image switching means 52 outputs a synchronization signal indicating the display timing of the element image group or pattern image to the display means 20.

The lens array control means 53 sets the first lens array 30 in the lens state and the second lens array 40 in the transparent state when the display means 20 displays a group of elemental images. In addition, the lens array control means 53 sets the first lens array 30 in the transparent state and the second lens array 40 in the lens state when the display means 20 displays a pattern image. Specifically, the lens array control means 53 outputs a synchronization signal indicating the switching timing of the lens state or the transparent state to the first lens array 30 and the second lens array 40 so as to be synchronized with the image switching means 52.

[Time-division display of 3D images]
The time-division display of three-dimensional images will be described with reference to FIG.
As shown in Fig. 6(a), when the first lens array 30 is in the lens state and the second lens array 40 is in the transmission state, the light rays of the elemental images displayed on the display means 20 are refracted by the first elemental lenses 31 and reproduced as parallel light rays. In Fig. 6(a), the second lens array 40 in the transmission state is illustrated by a dashed line.

As shown in Fig. 6(b), when the first lens array 30 is in the transmitting state and the second lens array 40 is in the lens state, the light beams of the pattern image displayed on the display means 20 are refracted by the second element lens 41 and reproduced as parallel light beams. In Fig. 6(a), the first lens array 30 in the transmitting state is shown by a dashed line.
Therefore, when the light beams in Figures 6(a) and 6(b) are displayed in a time-division manner, they become equivalent to the light beams in Figure 1(c). In this way, a three-dimensional image can be displayed according to the above-mentioned principle.

[Action and Effects]
In this way, by superimposing the elemental image group and the pattern image, the three-dimensional image display device 1B improves the number of pixels and the pixel density of the three-dimensional image to approximately the same as the number of lenses and the lens density of the second lens array 40. Furthermore, since the three-dimensional image display device 1B requires only one display means 20, a simpler configuration can be realized.

Third Embodiment
[Configuration of 3D image display device]
With reference to FIG. 7, the configuration of a three-dimensional image display device 1C according to the third embodiment will be described with respect to differences from the second embodiment.
The three-dimensional image display device 1C differs from the second embodiment in that it performs time-division display according to the polarization direction. As shown in Fig. 7, the three-dimensional image display device 1C includes a display means 20, a synchronization control device 50C, a polarization switching element 60 ( ₆₀₁ , ₆₀₂ ), a first lens array 70, and a second lens array 80. In this three-dimensional image display device 1C, the display means 20, the polarization switching element ₆₀₂ , the second lens array 80, the polarization switching element ₆₀₁ , and the first lens array 70 are arranged in this order from the front side.
The display unit 20 is the same as that in the second embodiment, and therefore a description thereof will be omitted.

First, each unit other than the synchronous control device 50C will be described.
The polarization switching elements 60 are disposed in front of the first lens array 70 and the second lens array 80, respectively, and switch the polarization direction of light from the display means 20. In this embodiment, the polarization switching element _60-1 is disposed in front of the first lens array 70, and the polarization switching element _60-2 is disposed in front of the second lens array 80. The polarization switching element 60 switches the polarization direction to horizontal polarization or vertical polarization in response to a synchronization signal from the lens array control means 53C described later.

The first lens array 70 is configured such that the first element lenses 71 are composed of a polarizing diffractive lens 72 and a convex lens 73. In other words, the first lens array 70 has the polarizing diffractive lenses 72 and convex lenses 73 arranged two-dimensionally as the first element lenses 71.

The polarized diffractive lens 72 is a lens whose focal length changes between positive and negative depending on the polarization direction. For example, the polarized diffractive lens 72 can be made of a periodically oriented liquid crystal polymer (Optica, Vol. 2, No. 11, pp. 958-964, November 2015). In addition, a polarized diffractive lens whose focal length changes between positive and negative depending on the direction of circular polarization instead of linear polarization may be used as the polarized diffractive lens 72. In this case, the polarization switching element 60 switches the light from the display unit 20 to right-handed circular polarization or left-handed circular polarization.
The convex lens 73 is disposed for each polarizing diffractive lens 72, and is, for example, a general convex lens. Here, the convex lens 73 is disposed after the polarizing diffractive lens 72.

In the second lens array 80, the second element lens 81 is composed of a polarizing diffractive lens 82 and a convex lens 83. In addition, the lens pitch of the second lens array 80 is smaller than that of the first lens array 70. For example, the lens pitch of the second lens array 80 is 1/2 that of the first lens array 70. In other respects, the second lens array 80 is similar to the first lens array 70, so further explanation will be omitted.

In addition, the first lens array 70 and the second lens array 80 can be combined with polarization switching elements 60 ₁ and 60 ₂ arranged in front of each other, making it possible to switch between the lens state and the transmission state in the same way as in the second embodiment, as will be described in detail later.

The synchronization control device 50C synchronizes the display timing of the elemental image group or pattern image with the switching timing of the lens state or transmission state of each of the first lens array 70 and the second lens array 80 on a frame-by-frame basis, and includes a storage means 51, an image switching means 52, and a lens array control means 53C. Note that the storage means 51 and the image switching means 52 are the same as those in the second embodiment, and therefore a description thereof will be omitted.

The lens array control means 53C sets the first lens array 70 in the lens state and the second lens array 80 in the transmission state when the display means 20 displays the elemental image group. Also, the lens array control means 53C sets the first lens array 70 in the transmission state and the second lens array 80 in the lens state when the display means 20 displays a pattern image. Specifically, the lens array control means 53C outputs a synchronization signal indicating the switching timing of the lens state or the transmission state to the polarization switching elements _60-1 , _60-2 so as to be synchronized with the image switching means 52.

[Switching between lens state and transmissive state]
Switching of the lens state or the transmission state in the first lens array 70 will be described in detail with reference to Fig. 8. Note that in Fig. 8, for ease of viewing the drawing, only three first lens elements 71 are shown.

The polarizing diffraction lens 72 has the characteristic that its focal length switches between positive and negative depending on the polarization direction of the incident light beam. Here, the focal length of the convex lens 73 is f. Furthermore, the focal length of the polarizing diffraction lens 72 when a horizontally polarized light beam is incident is +f, and the focal length of the polarizing diffraction lens 72 when a vertically polarized light beam is incident is -f.

As shown in FIG. 8(a), when the polarization switching element 60 switches the polarization direction of the incident light to horizontal polarization, the incident light is focused at the focal length f/2 of the first lens element 71 composed of a polarizing diffractive lens 72 and a convex lens 73. In other words, the first lens array 70 is in a lens state and functions as a lens array.

On the other hand, as shown in FIG. 8(b), when the polarization switching element 60 switches the polarization direction of the incident light to vertical polarization, the focal length of the polarizing diffraction lens 72 is negative, so the lens action is cancelled out between the polarizing diffraction lens 72 and the subsequent convex lens 73. In other words, the first lens array 70 is in a transmissive state, and the incident light passes through without being refracted.

In the three-dimensional image display device 1C, the focal length of the polarizing diffraction lens 72 when a horizontally polarized light beam is incident may be -f, and the focal length of the polarizing diffraction lens 72 when a vertically polarized light beam is incident may be +f. In this case, when the polarization switching element 60 switches the polarization direction of the incident light to horizontally polarized light, the first lens array 70 is in a transmitting state, and the incident light passes through without being refracted. On the other hand, when the polarization switching element 60 switches the polarization direction of the incident light to vertically polarized light, the first lens array 70 is in a lens state and functions as a lens array.
In addition, the second lens array 80 can be switched between a lens state and a transmission state based on the same principle as the first lens array 70 .

[Action and Effects]
In this way, in the same manner as in the second embodiment, the three-dimensional image display device 1C improves the number of pixels and pixel density of the three-dimensional image to approximately the same as the number of lenses and lens density of the second lens array 80. Furthermore, since the three-dimensional image display device 1C requires only one display means 20, a simpler configuration can be realized.

Fourth Embodiment
[Configuration of 3D image display device]
With reference to FIG. 9, the configuration of a three-dimensional image display device 1D according to the fourth embodiment will be described with respect to differences from the third embodiment.
The three-dimensional image display device 1D is different from the third embodiment in that it includes only one polarization switching element 60D. As shown in Fig. 9, the three-dimensional image display device 1D includes a display unit 20, a synchronization control device 50D, a polarization switching element 60D, a first lens array 70, and a second lens array 80.
The display unit 20, the first lens array 70 and the second lens array 80 are similar to those in the third embodiment, and therefore the description thereof will be omitted.

First, the polarization switching element 60D will be described.
The polarization switching element 60D is disposed between the display means 20 and the second lens array 80, and switches the polarization direction of light from the display means 20. In other words, unlike the third embodiment, no polarization switching element is disposed between the first lens array 70 and the second lens array 80. Note that the configuration of the polarization switching element 60D itself is similar to that of the third embodiment, and therefore further description will be omitted.

The synchronization control device 50D synchronizes the display timing of the elemental image group or pattern image with the switching timing of the lens state or transmission state of each of the first lens array 70 and the second lens array 80 on a frame-by-frame basis, and includes a storage means 51, an image switching means 52, and a lens array control means 53D. Note that the storage means 51 and the image switching means 52 are the same as those in the second embodiment, and therefore a description thereof will be omitted.

The lens array control means 53D sets the first lens array 70 in the lens state and the second lens array 80 in the transmission state when the display means 20 displays a group of elemental images. The lens array control means 53D also sets the first lens array 70 in the transmission state and the second lens array 80 in the lens state when the display means 20 displays a pattern image. Specifically, the lens array control means 53D outputs a synchronization signal indicating the switching timing of the lens state or the transmission state to the polarization switching element 60D so as to be synchronized with the image switching means 52.

[Switching between lens state and transmissive state]
The switching of the lens state or the transmission state in the first lens array 70 and the second lens array 80 will be described in detail with reference to FIG.
10, the first lens array 70 is in a transmitting state when the incident light is horizontally polarized and in a lens state when the incident light is vertically polarized, and the second lens array 80 is in a lens state when the incident light is horizontally polarized and in a transmitting state when the incident light is vertically polarized. Also, the polarizing diffractive lenses 72, 82 are designed so that the polarization directions of the incident light and the outgoing light are the same. The principle by which the first lens element 71 and the second lens element 81 are switched between the lens state and the transmitting state is the same as in the third embodiment.

As shown in FIG. 10(a), when the polarization switching element 60D switches the polarization direction of the incident light to horizontal polarization, the front-stage second lens array 80 goes into a lens state, and the rear-stage first lens array 70 goes into a transmitting state. In other words, in the three-dimensional image display device 1D, the front-stage second lens array 80 functions as a lens array for horizontally polarized incident light.

10B, when the polarization switching element 60D switches the polarization direction of the incident light to vertical polarization, the front-stage second lens array 80 is in a transmitting state, and the rear-stage first lens array 70 is in a lens state. That is, in the three-dimensional image display device 1D, the rear-stage first lens array 70 functions as a lens array for vertically polarized incident light.
[Action and Effects]
In this way, in the three-dimensional image display device 1D, similarly to the third embodiment, the number of pixels and pixel density of the three-dimensional image are improved to approximately the same as the number of lenses and lens density of the second lens array 80. Furthermore, since the three-dimensional image display device 1D requires only one polarization switching element 60D, a simpler configuration can be realized.

Although each embodiment of the present invention has been described in detail above, the present invention is not limited to the above-described embodiments, and also includes design modifications and the like within the scope of the present invention that do not deviate from the gist of the present invention.
In the lens array, a thinner diffractive lens may be used instead of the convex lens.As the polarization switching element, a liquid crystal panel having a high response speed such as an OCB type may be used.
Furthermore, the range of the angle θ set when solving the optimization problem may be different from that in equation (3).

In the three-dimensional image display device according to the first embodiment, the positions of the first lens array and the second lens array may be interchanged. Furthermore, in the three-dimensional image display device according to the first embodiment, the first lens array and the second lens array may be optically combined so that they are on the same plane.

1, 1B, 1C, 1D Three-dimensional image display device 10 Storage means 11 Element image group display means 12 First display device 13 First lens array 13a Element lens 14 Pattern image display means 15 Second display device 16 Second lens array 16a Element lens 17 Superimposition means 20 Display means 30 First lens array 31 First element lens 40 Second lens array 41 Second element lens 50, 50C, 50D Synchronization control device 51 Storage means 52 Image switching means 53, 53C, 53D Lens array control means 60, 60 ₁ , 60 _Two- polarization switching element 70 First lens array 71 First element lens 72 Polarizing diffractive lens 73 Convex lens 80 Second lens array 81 Second element lens 82 Polarizing diffractive lens 83 Convex lens 90 Stereoscopic display device 91 First display device 92 First lens array 93 Second display device 94 Second lens array

Claims (6)

A three-dimensional image display device that displays a three-dimensional image by superimposing an elemental image group composed of elemental images and an integral type pattern image,
a storage means for storing in advance the elemental image group and the pattern image that minimizes an error between a luminance of a group of light rays when the elemental image group and the pattern image are superimposed and a luminance of a group of light rays when a desired three-dimensional image is displayed;
an element image group display means for displaying the element image group stored in the storage means;
a pattern image display means for displaying the pattern image stored in the storage means;
a superimposing means for superimposing the element image group displayed by the element image group display means and the pattern image displayed by the pattern image display means;
A three-dimensional image display device comprising: the elemental image group display means comprises a first display device that displays the elemental image group, and a first lens array in which elemental lenses corresponding to the elemental images are two-dimensionally arranged;
the pattern image display means includes a second display device that displays the pattern image, and a second lens array having a smaller lens pitch than the first lens array;
2. The three-dimensional image display device according to claim 1, wherein the superimposing means is a beam splitter that optically combines the group of elemental images and the pattern image. A three-dimensional image display device that displays a three-dimensional image by superimposing an elemental image group composed of elemental images and an integral type pattern image,
a storage means for storing in advance the elemental image group and the pattern image that minimizes an error between a luminance of a group of light rays when the elemental image group and the pattern image are superimposed and a luminance of a group of light rays when a desired three-dimensional image is displayed;
a display means for displaying the element image group or the pattern image stored in the storage means in a time division manner;
a first lens array including first lens elements arranged two-dimensionally, the first lens elements being switchable between a lens state in which the first lens elements function as convex lenses and a transmission state in which the first lens elements transmit incident light without refracting the light ;
a second lens array including second lens elements arranged two-dimensionally at a lens pitch smaller than that of the first lens array, the second lens elements being switchable between a lens state in which the second lens elements function as convex lenses and a transmission state in which the second lens elements transmit incident light without refracting it ;
an image switching means for switching the element image group or the pattern image to be displayed on the display means;
a lens array control means for controlling the first lens array to be in a lens state and the second lens array to be in a transmission state when the display means displays the elemental image group, and for controlling the first lens array to be in the transmission state and the second lens array to be in a lens state when the display means displays the pattern image;
A three-dimensional image display device comprising: the first lens array is constituted by a liquid crystal lens as the first element lens,
4. The three-dimensional image display device according to claim 3 , wherein the second lens array is configured with a liquid crystal lens as the second element lens. a polarization switching element disposed in front of the first lens array and the second lens array, respectively, for switching a polarization direction of light from the display means;
The three-dimensional image display device according to claim 3, characterized in that the first element lens and the second element lens are composed of a polarizing diffractive lens whose focal length changes positive or negative depending on the polarization direction, and a convex lens arranged for each of the polarizing diffractive lenses. a polarization switching element disposed between the display means and the second lens array and switching a polarization direction of light from the display means;
The three-dimensional image display device according to claim 3, characterized in that the first element lens and the second element lens are composed of a polarizing diffractive lens whose focal length changes positive or negative depending on the polarization direction, and a convex lens arranged for each of the polarizing diffractive lenses.

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