WO2023275960A1

WO2023275960A1 - Optical element and display device

Info

Publication number: WO2023275960A1
Application number: PCT/JP2021/024422
Authority: WO
Inventors: 宗和伊達; 信哉志水; 奏山本
Original assignee: 日本電信電話株式会社
Priority date: 2021-06-28
Filing date: 2021-06-28
Publication date: 2023-01-05

Abstract

The optical element (10) pertaining to the present invention comprises shading parts (11) and transmitting parts (12) repeatedly provided in a prescribed direction and in a prescribed cycle on a plane, and the distribution of expected values of transmittance in the prescribed direction is a repetition of a bell-shaped function distributed in a prescribed cycle.

Description

Optical element and display device

The present disclosure relates to optical elements and display devices.

FIG. 17 is a diagram showing a configuration example of a conventional optical element 10A that functions as a light blocking body that blocks part of incident light and transmits the rest. As shown in FIG. 17, the optical element 10A includes a light blocking portion 11 that blocks light and a transmission portion 12 that transmits light. The light blocking portion 11 and the transmitting portion 12 linearly extend in a predetermined direction (hereinafter referred to as the “Y direction”), and extend in a direction orthogonal to the extending direction of the light blocking portion 11 and the transmitting portion 12 (hereinafter referred to as the “Y direction”). (referred to as "X direction") are repeatedly provided at a predetermined cycle. The optical element 10A has a configuration in which the distribution of the expected value of the transmittance in the X direction repeats two values of "0 (light blocking portion 11)" and "1 (transmitting portion 12)".

The light shielding body shown in FIG. 17 is used, for example, in combination with a two-dimensional display device in which pixels are arranged periodically, for a naked-eye three-dimensional display device that allows an observer to observe a three-dimensional image with the naked eye. However, in such a naked-eye three-dimensional display device, moire occurs due to interference between the periodically arranged pixels and the periodic structure of the light blocking member.

In addition to the naked-eye three-dimensional display device described above, for example, an object having a periodic structure is placed on the opposite side of the user by sandwiching a blind or a heater having electrodes formed periodically on transparent glass. The same problem occurs if you do.

As a technique for suppressing moire, Patent Literature 1 describes a technique in which a diffusion plate is arranged between two periodic structures and scattering by the diffusion plate is used. In addition, Patent Literature 2 describes a technique that utilizes refraction due to a fine concave-convex structure of a transparent body.

JP 2003-066371 A Retable 2007-091373

When the techniques described in Patent Documents 1 and 2 are applied to the naked-eye three-dimensional display device described above, an optical element for scattering or refracting light is provided before and after the light shielding body (optical element 10A) having a periodic structure. It is conceivable to provide more. However, when such an optical element is provided, it is difficult to bring the light shield and the two-dimensional display device into close contact with each other. There is

In addition, as in the technique described in Patent Document 2, when using a fine three-dimensional structure, it is difficult to form a fine structure. In addition, if a general-purpose product is used, even if moire can be suppressed, objects in the background may be displayed as being significantly blurred.

An object of the present disclosure, which has been made in view of the problems described above, is to provide an optical element and a display device capable of suppressing moire while suppressing an increase in size and cost of the device.

In order to solve the above problems, an optical element according to the present disclosure includes a light shielding portion and a transmission portion repeatedly provided in a predetermined direction at a predetermined period on a plane, and the expected value of the transmittance in the predetermined direction is a repetition of the bell-shaped function distributed at the predetermined period.

Also, in order to solve the above problems, a display device according to the present disclosure includes the above-described optical element and a two-dimensional display device, and the optical element is arranged on the front or back surface of the two-dimensional display device.

According to the optical element and the display device according to the present disclosure, it is possible to suppress moire while suppressing an increase in size and cost of the device.

1 is a diagram showing a configuration example of an optical element according to an embodiment of the present disclosure; FIG. FIG. 4 is a diagram showing another configuration example of an optical element according to an embodiment of the present disclosure; FIG. 5 is a diagram showing still another configuration example of an optical element according to an embodiment of the present disclosure; FIG. 5 is a diagram showing still another configuration example of an optical element according to an embodiment of the present disclosure; FIG. 5 is a diagram showing still another configuration example of an optical element according to an embodiment of the present disclosure; FIG. 10 is a diagram showing the shape of the difference between the two error functions shown in Equation 3; FIG. 4 is a diagram showing distribution of expected values of transmittance in the X direction in an optical element according to an embodiment of the present disclosure; 1 is a diagram illustrating a configuration example of a display device according to an embodiment of the present disclosure; FIG. FIG. 4 is a diagram showing another configuration example of a display device according to an embodiment of the present disclosure; FIG. 4 is a diagram showing the relationship between the weighted average of two images and the contour position; It is a figure which shows an example of a structure of a light-shielding body. 6 is a diagram showing an example of the positional relationship between the pixel configuration of the two-dimensional display device shown in FIGS. 3A and 3B and the transmission region of the light shield shown in FIG. 5; FIG. FIG. 7 is a diagram showing a mixture ratio of sub-pixels observed when the transmissive region shown in FIG. 6 is apparently shifted in the horizontal direction; 3B is a diagram showing another example of the pixel configuration of the two-dimensional display device shown in FIGS. 3A and 3B; FIG. It is a figure which shows another example of a structure of a light-shielding body. 9. It is a figure which shows an example of the positional relationship of the pixel structure of the two-dimensional display apparatus shown in FIG. 8, and the transmission region of the light-shielding body shown in FIG. FIG. 10 is a diagram showing a mixing ratio of sub-pixels observed when the transmissive region shown in FIG. 9 is apparently shifted in the horizontal direction; 9. It is a figure which shows another example of the positional relationship of the pixel structure of the two-dimensional display apparatus shown in FIG. 8, and the transmission region of the light-shielding body shown in FIG. It is a figure which shows the spatial frequency characteristic of the optical element used in the 1st Example. FIG. 10 is a diagram showing the degree of suppression of moiré according to the standard deviation σ of the optical element according to the first example. It is a figure which shows the spatial frequency characteristic of the optical element used by the 2nd Example. It is a figure which shows an example of the hardware constitutions of the control part shown to FIG. 3A and 3B. It is a figure which shows the structural example of the conventional optical element.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

FIG. 1A is a diagram showing a configuration example of an optical element 10 according to an embodiment of the present disclosure. The optical element 10 according to the present disclosure functions as a light blocking body that blocks part of incident light and transmits the rest.

As shown in FIG. 1A, the optical element 10 according to the present embodiment includes a light blocking portion 11 that blocks light and a transmission portion 12 that transmits light, which are provided on a plane. The light blocking portions 11 and the transmitting portions 12 each extend in a predetermined direction (Y direction) and are alternately provided in a direction (X direction) perpendicular to the extending direction at predetermined intervals. That is, the optical element 10 includes light shielding portions 11 and transmitting portions 12 that are repeatedly provided on a plane at predetermined intervals in a predetermined direction (X direction). In the following description, p is the period in which the light shielding portion 11 and the transmitting portion 12 are repeated.

In the optical element 10 shown in FIG. 1A, the expected value of the transmittance at the peripheral portion of the light shielding portion 11 continuously rises toward the transmitting portion 12 . That is, the transmittance of the light shielding portion 11 is controlled so that the distribution of the expected value of the transmittance in the X direction becomes a bell-shaped function. A bell-shaped function is, for example, a convolution of a rectangular function and a Gaussian distribution.

If the width of the rectangular function is d, the rectangular function is given by Equation 1 below. In Equation 1, x is the coordinate in the X direction.

The Gaussian distribution is expressed by Equation 2 below, where σ is the spread parameter (standard deviation).

The convolution of the rectangular function shown in Equation 1 and the Gaussian distribution shown in Equation 2 is shown in Equation 3 below.

In Equation 3, erf() is the error function, which is shown in Equation 4 below.

The shape of the function shown in Equation 3 is shown in FIG. 2A. As shown in FIG. 2A, the difference in the error functions erf(x) shifted in the x-direction has a bell-like shape.

FIG. 2B is a diagram showing the distribution of expected values of transmittance in the X direction in the optical element 10 according to this embodiment.

As shown in FIG. 2B, in the optical element 10 according to the present embodiment, the distribution of the expected value of the transmittance in the X direction is a bell-shaped distribution with a period p (the repetition period of the light shielding portion 11 and the light transmitting portion 12). is a repetition of the function of Specifically, the transmittance is highest near the center of the transmitting portion 12 in the X direction, and decreases toward the light shielding portions 11 on both sides. As mentioned above, the bell-shaped function is a convolution of a rectangular function with a Gaussian distribution. Therefore, the width of the bell-shaped function in the X direction, that is, the width of the light-transmitting portion 12 is d, which is the same as the width of the rectangular function. Note that FIG. 2B shows an example in which two bell-shaped function waveforms are arranged in the X direction. As a result, the waveform of the bell-shaped function is repeated many times in the X direction.

As shown in FIG. 1A, the optical element 10 in which the transmittance continuously changes in the peripheral portion of the light shielding portion 11 exposes a film of a camera, for example, to light of intensity corresponding to the continuously changing transmittance. can be formed by However, it is not easy to achieve such a change in transmittance with a fine structure with high accuracy. On the other hand, if it is a binary configuration such as transmittance "0" and "1", it can be manufactured at low cost and with high precision using a semiconductor process such as photolithography or high-definition printing technology. . Therefore, if the distribution of the expected value of the transmittance in the X direction can be made to be a repetition of a bell-shaped function distributed with a period p by the distribution of the light shielding portion 11 having a uniform transmittance, it is possible to achieve a lower cost and higher accuracy. Optical element 10 can be fabricated.

FIG. 1B is a diagram showing a configuration example of the optical element 10 in which the distribution of the expected value of the transmittance in the X direction is controlled by the distribution of the light shielding portions 11 with uniform transmittance. FIG. 1B shows an example in which the light blocking portion 11 is formed so that the transmissive portion 12 has a zigzag shape. Specifically, the light shielding portion 11 is formed so that the two curves of the transmissive portion 12 facing each other in the X direction have shapes represented by the two error functions of Equation 3, respectively.

In the optical element 10 shown in FIG. 1B, the area of the light blocking portion 11 in the Y direction at each position in the X direction changes according to the distribution shown in FIG. 2B. Therefore, in the optical element 10 shown in FIG. 1B, similarly to the optical element 10 shown in FIG. 1A, the distribution of the expected value of the transmittance in the X direction is a repetition of a bell-shaped function distributed with the period p. In this manner, the expected value of the transmittance in the X direction can be controlled by the area gradation of the light shielding portion 11 in the Y direction.

As shown in FIG. 1B, the optical element 10 in which the expected value of the transmittance in the X direction is controlled by the area gradation of the light shielding portion 11 has a distribution of the expected value of the transmittance in the X direction, for example, as a bell-shaped function. It can be manufactured by forming a thin film of chromium on a glass substrate in accordance with the shape of the light shielding portion 11 that repeats the above. In addition, such an optical element 10 can also be produced using, for example, a high-resolution photomechanical material such as a lith film.

In the optical element 10 shown in FIG. 1B, since the light shielding portion 11 exists in the center of the transmitting portion 12, the light utilization efficiency is lowered. Note that the center of the transmissive portion 12 is a position that is equidistant in the X direction from both ends of the transmissive portion 12 in the X direction.

FIG. 1C is a diagram showing another configuration example of the optical element 10 according to this embodiment. Similar to the optical element 10 shown in FIG. 1B, the optical element 10 shown in FIG. different.

In the optical element 10 shown in FIG. 1C, the outline of the transmission portion 12 has a bell-like function shape. Specifically, the outline of the transparent portion 12 has a shape obtained by normalizing the function of Equation 3 with the maximum value. Also in the optical element 10 shown in FIG. 1C, the distribution of the expected value of the transmittance in the X direction is a repetition of the bell-shaped function distributed with the period p. In addition, as shown in FIG. 1C, since the light blocking portion 11 does not exist in the center of the transmission portion 12, the optical element 10 shown in FIG. can be improved. In addition, in the optical element 10 shown in FIG. 1C, since the transmitting portions 12 are configured such that the shapes having a bell-like outline are continuously arranged in the Y direction, it is assumed that the transmitting portions 12 have a periodic structure in the Y direction. Even when superimposed, it is possible to suppress the occurrence of moire although the degree is weaker than that in the X direction.

In addition, in FIGS. 1B and 1C, an example in which the expected value of the transmittance in the X direction is gradation controlled by controlling the shape of the light shielding portion 11 has been described, but the present invention is not limited to this. For example, the light shielding portion 11 may be composed of minute dots (halftone dots), and the expected value of the transmittance in the X direction may be controlled by the density of the halftone dots.

Also, in the above example, the bell-shaped function is a convolution of a rectangular function and a Gaussian distribution, but it is not limited to this. A bell-shaped function may be any function having a bell-shaped shape, such as, for example, Gaussian, Laurentian or Voigt distributions. Also, the bell-shaped function may be a convolution of a rectangular function and a function having a bell-shaped shape. A function having a bell-shaped shape is, for example, Gaussian distribution, Laurentian distribution or Voigt distribution, but is not limited thereto.

1B and 1C show an example in which the patterns formed by the light blocking portions 11 and the transmitting portions 12 are aligned in the Y direction and have a uniform period, but the pattern is not limited to this. If the distribution of the expected value of the transmittance in the X direction is the same as that of the optical element 10 shown in FIGS. 1B and 1C, for example, as shown in FIG. may be formed. Further, if the distribution of the expected value of the transmittance in the X direction is similar to that of the optical element 10 shown in FIGS. 1B and 1C, for example, as shown in FIG. The width in the Y direction of the portion up to the next turn may be different. By disturbing the period in the Y direction in this way, it is possible to suppress moire with the periodic structure in the Y direction.

FIG. 3A is a diagram showing a configuration example of the display device 100 according to this embodiment.

As shown in FIG. 3A, the display device 100 according to this embodiment includes an optical element 10, a two-dimensional display device 101, a backlight 102, and a control section 103. In the display device 100 shown in FIG. 3A, the optical element 10, the two-dimensional display device 101, and the backlight 102 are arranged in this order as seen from the observer ob. That is, the optical element 10 is provided in front of the two-dimensional display device 101 as seen from the observer ob.

The two-dimensional display device 101 has a configuration in which a plurality of pixels each having a plurality of sub-pixels of a plurality of colors (eg, red, green, and blue) arranged in a predetermined direction are arranged two-dimensionally. The two-dimensional display device 101 modulates light emitted from a backlight 102, which is a surface light source provided on the back side, and emits the light from the front side. The two-dimensional display device 101 and the backlight 102 are, for example, a liquid crystal display, an organic EL (Electro Luminescence) display, a PDP (Plasma Display Panel) display, an LED (Light Emitting Diode) display, etc., but are not limited to these.

The optical element 10 transmits part of the light emitted from the two-dimensional display device 101 and blocks the rest. The light transmitted through the optical element 10 is observed by the observer ob.

In FIG. 3A, an example in which the optical element 10 is provided on the front surface of the two-dimensional display device 101 has been described, but it is not limited to this. As shown in FIG. 3B, the optical element 10 may be provided between the two-dimensional display device 101 and the backlight 102 . That is, the optical element 10 may be provided on the back surface of the two-dimensional display device 101 . In this case, the optical element 10 transmits part of the light emitted from the backlight 102 and blocks the rest. The light transmitted through the optical element 10 is modulated by the two-dimensional display device 101 and observed by the observer ob.

In the display device 100 shown in FIGS. 3A and 3B, the observer ob observes the light transmitted through the transmission portion 12 of the optical element 10 . With such a configuration, according to the display device 100 according to the present embodiment, an image of an object viewed from each viewpoint (hereinafter referred to as a “directive image”) changes as the observation direction (viewpoint position) of the observer ob changes. ) can be observed, motion parallax (change in appearance depending on observation position) can be reproduced. Here, smoother motion parallax can be reproduced by linear blending that smoothly changes the luminance ratio of a plurality of images as the observation position moves. Linear blending will be described below.

FIG. 4 is a diagram showing the relationship between the weighted average of two images (images A and B) and the contour position. When the directional image is displayed so that the image shift width between adjacent viewpoints is a small value of about 3 [arc min], the weighting ratio is between 0 and 1, as shown in FIG. , it changes linearly and continuously, so it is possible to generate an image with an appropriate contour position that matches the position of the viewpoint. That is, by connecting two images with small image shifts at a ratio that varies linearly, an image of an intermediate viewpoint between adjacent viewpoints can be visually perceived. Note that in the case of an image with few high-frequency spatial frequency components, an intermediate viewpoint image is perceived even if the shift width is about 10 [arc min].

Linear blending combining the two-dimensional display device 101 and the light shielding body 20 will be described. First, an example of the configuration of the light shielding body 20 will be described.

FIG. 5 is a diagram showing an example of the configuration of the light blocking body 20. As shown in FIG.

As shown in FIG. 5, the light shielding body 20 includes a light shielding region 21 that blocks light and a plurality of transmission regions 22 that transmit light. The light-shielding region 21 and the transmissive region 22 correspond to the light-shielding portion 11 and the transmissive portion 12 of the optical element 10 according to this embodiment, respectively. In FIG. 5, the transmissive area 22 is hatched diagonally upward to the right, and the light shielding area 21 is outlined. For example, the plurality of transmissive regions 22 have a width of d in the horizontal direction and are arranged in the horizontal direction with a period of n×dp. n is an integer.

FIG. 6 is a diagram showing an example of the positional relationship between the pixel configuration of the two-dimensional display device 101 and the transmissive region 22 of the light blocking member 20 shown in FIG. In FIG. 6, the pixel configuration of the two-dimensional display device 101 has a pixel structure in which a plurality of sub-pixels of different colors are arranged vertically and sub-pixels of the same color are arranged horizontally. FIG. 6 shows a structure in which three primary color sub-pixels of red (R), green (G), and blue (B) are arranged in stripes.

　One pixel px is composed of three sub-pixels, a red sub-pixel R, a green sub-pixel G and a blue sub-pixel B arranged in the vertical direction. Each of the red sub-pixel R, the green sub-pixel G, and the blue sub-pixel B has a horizontally long shape with a width in the horizontal direction longer than the width in the vertical direction. In the following description, the pixel pitch is dp in both the vertical and horizontal directions, that is, the width of each pixel px in the horizontal and vertical directions is dp (square pixel). However, the shape of the pixel px may be a horizontally long shape that is long in the horizontal direction or a vertically long shape that is long in the vertical direction.

As shown in FIG. 6, the transmissive region 22 is arranged so that the entire pixel px can be observed at a predetermined viewpoint.

FIG. 7 shows the mixing ratio of sub-pixels observed through the transmissive area 22 when the transmissive area 22 apparently moves in the horizontal direction from the state shown in FIG. 6 as the viewpoint position changes. It is a figure which shows a change.

In FIG. 7, "0" shown on the horizontal axis indicates the mixing ratio of sub-pixels in the state shown in FIG. When the horizontal axis is "0", the entire red sub-pixel R2, green sub-pixel G2 and blue sub-pixel B2 are observed through the transmissive region 22. FIG. As the viewpoint position changes, as the transmissive region 22 apparently moves to the right in the drawing (corresponding to the right direction in FIG. 7) from the state shown in FIG. Red sub-pixel R2, green sub-pixel G2 and blue sub-pixel B2 are decreased and red sub-pixel R3, green sub-pixel G3 and blue sub-pixel B3 are increased. In addition, as the viewpoint position changes, as the transmissive area 22 apparently moves leftward in the plane of the drawing (corresponding to the leftward direction in FIG. 7) from the state shown in FIG. Observed red subpixel R2, green subpixel G2 and blue subpixel B2 decrease and red subpixel R1, green subpixel G1 and blue subpixel B1 load. By observing the two-dimensional display device 101 through the light blocking member 20 in this manner, linear blending can be achieved for each of red, green, and blue when the viewpoint position moves in the horizontal direction.

FIG. 8 is a diagram showing another example of the pixel configuration of the two-dimensional display device 101. FIG.

In the example shown in FIG. 8, the two-dimensional display device 101 has a pixel structure in which a plurality of sub-pixels of different colors are arranged horizontally and sub-pixels of the same color are arranged vertically. FIG. 8 shows a structure in which three primary color sub-pixels of red (R), green (G), and blue (B) are arranged in stripes. The pixel configuration of the two-dimensional display device 101 shown in FIG. 8 corresponds to the vertical stripe pixel configuration according to Example 2, which will be described later.

　One pixel px is composed of three sub-pixels, a red sub-pixel R, a green sub-pixel G and a blue sub-pixel B arranged in the horizontal direction. Each of the red sub-pixel R, the green sub-pixel G, and the blue sub-pixel B has a vertically elongated shape in which the width in the vertical direction is longer than the width in the horizontal direction. In the following description, the pixel pitch is dp in both the vertical and horizontal directions, that is, the width of each pixel px in the horizontal and vertical directions is dp (square pixel). However, the shape of the pixel px may be a horizontally long shape that is long in the horizontal direction or a vertically long shape that is long in the vertical direction.

In the following, linear blending in the case of combining the two-dimensional display device 101 having the pixel configuration shown in FIG. 8 and the light blocking member 20 shown in FIG. 9 will be described as an example. First, the structure of the light shielding body 20 will be described.

As shown in FIG. 9, the light shielding body 20 includes a light shielding region 21 that blocks light and a plurality of transmission regions 22 that transmit light. The light-shielding region 21 and the transmissive region 22 correspond to the light-shielding portion 11 and the transmissive portion 12 of the optical element 10 according to this embodiment, respectively. In FIG. 9, the transmissive area 22 is hatched diagonally upward to the right, and the light shielding area 21 is outlined. The plurality of transmissive regions 22 are arranged, for example, in the horizontal direction with a period of n/3dp. n is an integer. However, the pitch at which the plurality of transmissive regions 22 are arranged may be a non-integer multiple of the horizontal width of the pixel px.

The transmissive region 22 has a width (dp/C) corresponding to 1/C of the width of the pixel px in the horizontal direction (C is the number of colors of the sub-pixels forming the pixel), and has a width greater than the width of the sub-pixel in the vertical direction. have a long width. The width of the sub-pixel includes the width of the sub-pixel, and the width of the transmissive region 22 in the lateral direction is obtained by considering the processing error of the transmissive region 22 or the diffraction of light passing through the transmissive region. contains a width slightly smaller than the lateral width of the It should be noted that when the light shielding body 20 as a whole is reduced or enlarged, the transmissive area 22 is also reduced or enlarged. Here, if D is the width of the sub-pixel, D' is the width of the transmissive region, x is the distance between the two-dimensional display device 101 and the light shielding member 20, and L is the optimum viewing distance, then D is the width of the pixel pd and D is the width of the light shielding region. The relationship with the width D' is represented by Equation 5 below.

Here, generally, the distance x between the two-dimensional display device 101 and the light shielding body 20 is about several mm (for example, about 2 mm). Also, the optimum viewing distance L is about several meters (for example, about 1 m). Therefore, the distance between the width D of the sub-pixel and the width D' of the transmissive region 22 is very small. "A width slightly smaller than the width of the sub-pixel in the horizontal direction" means that the distance x between the two-dimensional display device 101 and the light shielding member 20 as defined by Equation 5 and the optimum viewing distance L It includes a range smaller than the width D of the sub-pixel. In the above example, the pixel configuration of the two-dimensional display device 101 is a vertical stripe in which sub-pixels of the same color are arranged in the vertical direction. However, the pixel configuration is not limited to this. The pixel configuration of the two-dimensional display device 101 may be horizontal stripes in which sub-pixels of the same color are arranged horizontally. Even if the pixel configuration of the two-dimensional display device 101 is horizontal stripes, the width of the transmissive region 22 may include a width slightly smaller than the width of the sub-pixels.

In the example shown in FIG. 8, the pixel px is composed of a red sub-pixel R, a green sub-pixel G and a blue sub-pixel B, so C=3. Therefore, the transmissive region 22 is an opening having a horizontal width of dp/3 and a vertical width longer than the pixel width. In the example shown in FIG. 9 , the vertical width of the transmissive region 22 is the vertical width of the light blocking member 20 .

FIG. 10 is a diagram showing an example of the positional relationship between the pixel configuration of the two-dimensional display device 101 shown in FIG. 8 and the transmissive region 22 of the light shield 20 shown in FIG. As shown in FIG. 10, the transmissive region 22 is arranged so that the entire red sub-pixel R2 can be observed at a predetermined viewpoint. In the example shown in FIG. 10, the pitch at which the plurality of transmissive regions 22 are arranged is an integral multiple of the horizontal width of the pixel px.

FIG. 11 shows the mixing ratio of the sub-pixels observed through the transmissive area 22 when the transmissive area 22 apparently moves laterally from the state shown in FIG. 10 as the viewpoint position changes. It is a figure which shows a change.

In FIG. 11, "0" shown on the horizontal axis indicates the mixing ratio of sub-pixels in the state shown in FIG. When the horizontal axis is "0", the entire red sub-pixel R2 is observed through the transmissive region 22. FIG. As the viewpoint position changes, as the transmissive region 22 apparently moves rightward in the plane of the drawing (corresponding to the rightward direction in FIG. 11) from the state shown in FIG. The number of red sub-pixels R2 to be used decreases and the number of green sub-pixels G2 increases. In addition, as the viewpoint position changes, as the transmissive area 22 apparently moves leftward in the plane of the drawing (corresponding to the leftward direction in FIG. 11) from the state shown in FIG. The observed red subpixel R2 decreases and the blue subpixel B1 increases. By observing the two-dimensional display device 101 through the light blocking member 20 in this manner, linear blending can be achieved for each of red, green, and blue when the viewpoint position moves in the horizontal direction.

As described above, the light-shielding region 21 and the transmissive region 22 of the light-shielding body 20 correspond to the light-shielding portion 11 and the transmissive portion 12 of the optical element 10 according to the present embodiment, respectively, and the light-shielding portion and the light-transmitting portion is repeated alternately in a predetermined direction. Therefore, the display device 100 including the optical element 10 can also achieve linear blending.

Note that in FIG. 10, the pitch at which the transmissive regions 22 are arranged is an integral multiple of the horizontal width of the pixel px. That is, the transmissive regions 22 are arranged with a period of n/3dp in the horizontal direction. However, as shown in FIG. 12, the pitch at which the transmissive regions 22 are arranged may be a non-integer multiple of the horizontal width of the pixel. In such a configuration, the colors of the sub-pixels observed through the two transmissive regions 22 arranged adjacent to each other in the horizontal direction are different from each other. In the example shown in FIG. 12, the entire red sub-pixel R2 is observed through one transmissive region 22 (the transmissive region 22 arranged on the left side in FIG. 12), and is laterally adjacent to the one transmissive region 22. The entire green sub-pixel G7 is observed through the transmissive area 22 (the transmissive area 22 arranged on the right side in FIG. 12). Since n is not a multiple of 3, the colors of the sub-pixels observed through the three adjacent transmissive areas 22 are different. , can prevent color shading.

In this embodiment, an example in which one pixel is composed of sub-pixels of three primary colors is used, but the present invention is not limited to this. It may be composed of sub-pixels of four colors.

Referring to FIGS. 3A and 3B again, the control unit 103 controls the display of the two-dimensional display device 101. FIG. Specifically, the control unit 103 displays the pixels of the image from a predetermined viewpoint on the pixels of the two-dimensional display device 101 that are observed through the transmission unit 12 from that viewpoint. By doing so, it is possible to reproduce the motion parallax caused by the change of the viewpoint position, thereby realizing a more realistic image display.

Note that the control unit 103 can display an image with an angle of parallax of 10 minutes or less, more preferably 5 minutes or less between images displayed in a combination of adjacent sub-pixels (combination of sub-pixels with consecutive numbers). preferable. Image parallax is the amount of deviation δ between images of viewpoints located next to each other on the screen, which is expressed as an angle when viewed from a distance L from an assumed observation position to display device 100, and is expressed below. be done.

In the present embodiment, an example in which video display is performed using linear blending to reproduce motion parallax caused by a change in viewpoint position has been described. It is also possible to display images that are not displayed.

Next, suppression of moiré by the optical element 10 according to this embodiment will be described using the display device 100 shown in FIG. 3A as a specific example.

(First embodiment)
As the two-dimensional display device 101, a panel of RGB horizontal stripes with a pixel pitch dp of 96 μm (a panel in which sub-pixels of the same color are arranged in the horizontal direction and sub-pixels of different colors forming one pixel are arranged in the vertical direction) is used. prepared. Also, an optical element 10 was prepared in which the width of the transmitting portion 12 in the X direction (=the width d of the rectangular function) was 96 μm and the period p=7d=762 μm. A bell-shaped function is a convolution of a rectangular function and a Gaussian distribution. Note that any of the optical elements 10 shown in FIGS. 1A to 1E may be used because the distribution of expected transmittance values is the same.

A display device 100 in which the prepared optical element 10 is arranged in front of the prepared two-dimensional display device 101 with a predetermined interval so that the pixel stripes of the two-dimensional display device 101 and the stripes of the transmission part 12 are orthogonal to each other. prepared. That is, the width of the transmissive portion 12 (the width d of the rectangular function) is such that a plurality of sub-pixels of different colors forming the two-dimensional display device 101 are arranged in a direction perpendicular to the direction in which the light shielding portions 11 and the transmissive portions 12 are repeated. A display device 100 having a pitch (width) substantially equal to that of a pixel or a sub-pixel constituting the pixel was prepared. In such a display device 100, when the optical element 10A shown in FIG. 17 was used in place of the optical element 10 according to the present embodiment, moire was severely generated.

On the other hand, when the optical element 10 according to the present embodiment was used, moire was slightly observed when σ=0.25d, but almost no moire was observed when σ=0.375d.

FIG. 13 is a graph showing spatial frequency characteristics of the optical element 10 used in this example.

The waveform shown in FIG. 13 shows the spectral envelope that indicates the spatial frequency characteristics. Corresponding to the period p in the actual optical element 10, this envelope is applied with a comb function consisting of a line spectrum with an interval of 1/p (an interval of 1 on the scale of the graph in FIG. 13). The line spectrum frequencies are indicated by white triangles attached to the upper frame of the graph.

In the case of the optical element 10A shown in FIG. 17, it is the envelope of the sinc function indicated by σ=0. The spatial frequency is 1/d, that is, the envelope is attenuated while crossing the X-axis at the position of 7 on the scale of the horizontal axis. 1/d is the spatial frequency corresponding to the pixel pitch of the two-dimensional display device 101 . Including high frequencies, the black triangles attached to the upper frame of the graph indicate spatial frequencies corresponding to the pixel pitch of the two-dimensional display device 101 .

Since moire occurs where white triangles and black triangles match, it is considered effective to remove moire by suppressing spatial frequency components of 1/d or higher.

As shown in FIG. 13, high-frequency components remained until σ≦0.25d, and moiré was observed to some extent. However, when σ≧0.375d, harmonic components with a frequency of 1/d or more were almost completely suppressed, and moire was also suppressed.

Whether it is necessary to suppress moire depends on the conditions of use. be. Further, even if moiré is conspicuous, if σ=0.5d, moiré can be sufficiently suppressed. Therefore, in the optical element 10 according to the present embodiment, when the bell-shaped function is the convolution of the rectangular function and the Gaussian distribution, the standard deviation σ of the Gaussian distribution is 0.25d to 0.5d. preferable.

When the optical element 10 is used in the display device 100, if σ is too large, multiple directional images are mixed and sufficient depth cannot be displayed. When the optical element 10 with σ=0.375d was produced and the display device 100 was used, a good three-dimensional image without moire could be observed with the naked eye.

FIG. 14 is a graph showing the degree of occurrence of moire depending on the magnitude of σ. In FIG. 14, the horizontal axis represents σ, and the vertical axis represents the amplitude of moire at σ=0 corresponding to the optical element 10A shown in FIG. , indicates the relative value of the moire amplitude. It can be considered that the value on the vertical axis is proportional to the moire intensity.

As shown in FIG. 14, the moire amplitude decreases to about 29% at σ=0.25d, to about 6% at σ=0.375d, and to about 6% at σ=0, compared to the case of σ=0. It was confirmed that it decreased to about 0.7% at 0.5d.

(Second embodiment)
The two-dimensional display device 101 has a pixel pitch dp of 96 μm and an RGB vertical stripe panel (a panel in which sub-pixels of the same color are arranged vertically and sub-pixels of different colors forming one pixel are arranged horizontally). prepared. Also, an optical element 10 was prepared in which the width of the transmissive portion 12 in the X direction (=the width d of the rectangular function) was 32 μm and the period p=7d=224 μm. A bell-shaped function is a convolution of a rectangular function and a Gaussian distribution. Note that any of the optical elements 10 shown in FIGS. 1A to 1E may be used because the distribution of expected transmittance values is the same.

A display device in which the prepared optical element 10 is arranged in front of the prepared two-dimensional display device 101 with a predetermined interval so that the pixel stripes of the two-dimensional display device 101 and the stripes of the transmission part 12 are parallel. 100 were prepared. That is, the display device 100 was prepared in which the width of the transmissive portion 12 (the width d of the rectangular function) is substantially equal to the pitch (width) of the sub-pixels of the pixels forming the two-dimensional display device 101 . In such a display device 100, when the optical element 10A shown in FIG. 17 was used in place of the optical element 10 according to the present embodiment, moire was severely generated.

FIG. 15 is a graph showing the spatial frequency characteristics of the optical element 10 used in this example.

The waveform shown in FIG. 15 shows a spectrum envelope indicating spatial frequency characteristics. Corresponding to the period p in the actual optical element 10, this envelope is applied with a comb function consisting of a line spectrum with an interval of 1/p (an interval of 1 on the scale of the graph in FIG. 15). The line spectrum frequencies are indicated by white triangles attached to the upper frame of the graph.

In the case of the optical element 10A shown in FIG. 17, it is the envelope of the sinc function indicated by σ=0. The spatial frequency is 1/d, that is, the envelope is attenuated while crossing the X-axis at the position of 7 on the scale of the horizontal axis. 1/3d is the spatial frequency corresponding to the pixel pitch of the two-dimensional display device 101 . When harmonics are included, the black triangle attached to the upper frame of the graph indicates the spatial frequency corresponding to the pixel pitch of the two-dimensional display device 101 .

Since moire occurs where white triangles and black triangles coincide, it is considered effective to remove moire if spatial frequency components of 1/d or higher are suppressed, as in the first embodiment. Although the spatial frequency of the panel also includes a component of 1/d or less, it does not contribute to the generation of moire since the white triangle and the black triangle do not match. Therefore, the value of σ is the same as in the first embodiment.

As shown in FIG. 15, harmonic components remained until σ≦0.25d, and moire was observed although there was a difference in degree. However, when σ≧0.375d, harmonic components with a frequency of 1/d or more were almost completely suppressed, and moire was also suppressed.

In addition, in the first and second embodiments described above, the bell-shaped function is a convolution of a rectangular function and a Gaussian distribution. The point is that it is sufficient to attenuate high-frequency components above a specific frequency, so other bell-shaped functions with smooth tails on the high-frequency side may be used.

It is also possible to use a computer 200 capable of executing program instructions in order to function as the control unit 103 of the display device 100 described above. FIG. 16 is a block diagram showing a schematic configuration of a computer 200 functioning as the control unit 103. As shown in FIG. Computer 200 may be a general purpose computer, special purpose computer, workstation, personal computer (PC), electronic notepad, or the like. Program instructions may be program code, code segments, etc. for performing the required tasks.

As shown in FIG. 16, the computer 200 includes a processor 210, a ROM (Read Only Memory) 220, a RAM (Random Access Memory) 230, a storage 240, an input section 250, an output section 260, and a communication interface ( I/F) 270. Each component is communicatively connected to each other via a bus 290 . The processor 210 is specifically a CPU (Central Processing Unit), MPU (Micro Processing Unit), GPU (Graphics Processing Unit), DSP (Digital Signal Processor), SoC (System on a Chip), etc. may be configured by a plurality of processors of

The processor 210 executes control of each configuration and various kinds of arithmetic processing. That is, processor 210 reads a program from ROM 220 or storage 240 and executes the program using RAM 230 as a work area. The processor 210 performs control of each configuration and various arithmetic processing according to programs stored in the ROM 220 or the storage 240 . In this embodiment, the ROM 220 or storage 240 stores the program according to the present disclosure.

The program may be stored in a storage medium readable by the computer 200. Programs can be installed in the computer 200 using such a storage medium. Here, the storage medium storing the program may be a non-transitory storage medium. The non-temporary storage medium is not particularly limited, but may be, for example, a CD-ROM, a DVD-ROM, a USB (Universal Serial Bus) memory, or the like. Also, this program may be downloaded from an external device via a network.

The ROM 220 stores various programs and various data. RAM 230 temporarily stores programs or data as a work area. The storage 240 is configured by a HDD (Hard Disk Drive) or SSD (Solid State Drive) and stores various programs including an operating system and various data.

The input unit 250 includes one or more input interfaces that receive user's input operations and acquire information based on the user's operations. For example, the input unit 250 is a pointing device, keyboard, mouse, etc., but is not limited to these.

The output unit 260 includes one or more output interfaces that output information. For example, the output unit 260 is a display that outputs information as video or a speaker that outputs information as audio, but is not limited to these. Note that the output unit 260 also functions as the input unit 250 in the case of a touch panel type display.

The communication interface 270 is an interface for communicating with an external device.

As described above, the optical element 10 according to the present embodiment includes the light blocking portions 11 and the transmitting portions 12 that are repeatedly provided in a predetermined direction on a plane with a predetermined period. The distribution of expected transmittance values in a given direction is a repetition of a bell-shaped function distributed at a given cycle.

Since the distribution of the expected transmittance value is a repetition of a bell-shaped function, it is possible to suppress high-frequency components above a predetermined value that cause moiré, so that the occurrence of moiré can be suppressed. In addition, since there is no need to separately provide other optical elements, it is possible to suppress an increase in the size of the device, and it is possible to relatively easily fabricate by printing or the like, so an increase in the cost required for fabrication can be suppressed. be able to.

Although the above-described embodiments have been described as representative examples, it will be apparent to those skilled in the art that many modifications and substitutions can be made within the spirit and scope of the present disclosure. Therefore, this invention should not be construed as limited by the above-described embodiments, and various modifications and changes are possible without departing from the scope of the claims. For example, it is possible to combine a plurality of configuration blocks described in the configuration diagrams of the embodiments into one, or divide one configuration block.

REFERENCE SIGNS LIST 10 optical element 11 light shielding section 12 transmission section 100 display device 101 two-dimensional display device 102 backlight 103 control section 20 light shielding body 21 light shielding region 22 transmission region 200 computer 210 processor 220 ROM
230 RAM
240 storage 250 input unit 260 display unit 270 communication I/F
290 passes

Claims

Equipped with a light shielding portion and a transmission portion repeatedly provided in a predetermined direction at a predetermined cycle on a plane,
The optical element, wherein the distribution of expected values of transmittance in the predetermined direction is a repetition of a bell-shaped function distributed at the predetermined period.
In the optical element according to claim 1,
The optical element, wherein the bell-shaped function is a Gaussian distribution, a Lorentian distribution or a Voigt distribution.
In the optical element according to claim 1,
The optical element, wherein the bell-shaped function is a convolution of a rectangular function with a Gaussian distribution, a Lorentian distribution or a Voigt distribution.
In the optical element according to claim 3,
The bell-shaped function is a convolution of a rectangular function and a Gaussian distribution,
The optical element, wherein the standard deviation σ of the Gaussian distribution is 0.25d to 0.5d, where d is the width of the rectangular function.
In the optical element according to any one of claims 1 to 4,
The optical element, wherein the expected value of the transmittance is controlled by the area gradation of the light shielding portion.
In the optical element according to claim 5,
The optical element, wherein the outline of the transmission portion is the shape of the bell-shaped function.
An optical element according to any one of claims 1 to 6 and a two-dimensional display device,
A display device, wherein the optical element is arranged on the front or back surface of the two-dimensional display device.
The display device according to claim 7,
the bell-shaped function is a convolution of a rectangular function and a function having a bell-shaped shape;
The display device, wherein the width of the rectangular function is substantially equal to the pitch of the pixels forming the two-dimensional display device or the sub-pixels forming the pixels.