JP7615590B2 - Light reproduction device, three-dimensional space display system, light reproduction method, and program - Google Patents

Description

The present invention relates to a light reproduction device, a three-dimensional space display system, a light reproduction method, and a program.

Whether it's between family members, close friends, or in the political or business world, it's important to know each other's feelings when communicating. In terms of non-verbal communication, it's necessary to communicate the appropriate conversational interval and personal space without feeling awkward. In addition, it's important to pick up on non-verbal information, such as the other person's facial expressions and gestures, within that distance.

Various technologies are being offered to facilitate smooth communication. For example, in the field of communications technology, 5G low-latency technology can reduce communication delays, allowing online conversations to be spaced in the same way as in real conversations. In addition, three-dimensional measurement technology such as TOF (Time of Flight) can be used to accurately measure the distance between people. However, no technology is known that can seamlessly display a deep space in which an appropriate interpersonal distance (personal space) can be maintained.

In this application, a deep space refers to a space that is larger than the space in which an interpersonal distance of about 1.2 m to about 3.6 m can be maintained, which is mainly applied when people communicate publicly with others. In the following explanation, this deep space in which an interpersonal distance of about 1.2 m to about 3.6 m can be maintained is referred to as a "social distance space."

There are various technologies for displaying three-dimensional images with depth. For example, there are wearable display devices such as head-up displays, polarized glasses, and liquid crystal shutter glasses, as well as technologies such as parallax barrier and lenticular that display three-dimensional images by having two eyes observe different parallax without wearing any equipment. These technologies for displaying three-dimensional images create a sense of three-dimensionality using only parallax. As a result, they require convergence to concentrate the gaze on one point and focus adjustments, which can cause eye strain and nausea. For this reason, they are not suitable as a tool for displaying socially distant spaces with depth.

In response to this, Non-Patent Document 1 discloses a technology for displaying three-dimensional images without the need for convergence or focus adjustment. Non-Patent Document 1 discloses a super multi-eye display and a display (see FIG. 19) that uses a microlens array to record a light field (directional information and intensity distribution on the imaging surface of a digital camera of light rays incident on the imaging surface) and reproduces (displays) the recorded light field. In addition, a static display type light field display (see FIG. 20) in which liquid crystal panels or the like are layered is proposed.

The 3D image display device described in Patent Document 1 discloses a technology for increasing the number of viewpoints sufficiently (super multi-eye). This makes it possible to satisfy the four factors of human 3D perception: binocular parallax, focus adjustment, convergence, and motion parallax. Displaying 3D images using such super multi-eye displays and light field displays achieves natural focus adjustment and convergence by reproducing light rays smaller than the size of the pupil.

Patent Application No. 2007-17634

[online], "Research Trends of Light Field Displays" March 2018, Takafumi Koike, [Retrieved August 3, 2020], Internet <URL: https://home.jeita.or.jp/device/lirec/symposium/fpd/pdf/2018_2a.pdf>

However, super multi-eye displays such as those described in Patent Document 1 reproduce light rays at a size smaller than the pupil size, thereby achieving natural focus adjustment and convergence. Because light rays are controlled over a very small area, the effects of diffraction cause greater blurring the further away from the display surface. For this reason, only objects close to the display can be reproduced, and it is difficult to reproduce a social distance space when the display surface is close to the observer. On the other hand, if the display surface is placed away from the observer and close to the social distance space, the display needs to be larger than the space it is desired to display, which requires high costs and a large installation space.

As described above, when trying to recreate a socially distanced space, conventional light field displays had the problem of significant blurring caused by the effects of diffraction.

The embodiments of the present invention have been made in consideration of the above problems, and aim to provide a light reproduction device, a three-dimensional space display system, a light reproduction method, and a program that can display a space that is primarily about 1.2 m to 3.6 m deep from the display surface (social distance space), or a space that is deeper than that, as a three-dimensional space that provides a natural sense of distance and has little blurring.

In order to solve the above problems, a light reproducing device according to an embodiment of the present invention is a light reproducing device that reproduces light rays virtually emitted from a stereoscopic image when the stereoscopic image is reproduced in a reproduction space, and includes a stereoscopic image display unit that displays the stereoscopic image as at least one of a virtual image and a real image by light rays emitted from each element cell included in an element cell set consisting of a plurality of element cells arranged two-dimensionally corresponding to a reproduction screen, and the stereoscopic image display unit displays the stereoscopic image in an area in the reproduction space where the distance in the depth direction corresponds to a social distance, and the stereoscopic image is displayed in a range from a display surface. The element cells are displayed in a range of at least 1.2 m to 3.6 m in the depth direction, and the size of each element cell in the element cell set and the pitch of the element cells when the element cells are two-dimensionally arranged are values determined according to the degree to which the stereoscopic image displayed in the reproduction space is observed by the observer, and the size of the element cells is determined so that the spread angle of the diffracted light from the element cells is equal to or smaller than the angular resolution according to the eyesight of the observer, the size of the element cells is 0.8 mm or more, and the pitch of the element cells is 1.2 mm or less. Note that the degree to which the stereoscopic image is observed by the observer here indicates the position and range in which the stereoscopic image is displayed, the degree of blurring that the observer tolerates, etc.

According to an embodiment of the present invention, a social distance space can be displayed as a three-dimensional space that provides a natural sense of distance and has little blurring.

1 is a block diagram showing a configuration of a three-dimensional space display system 1 according to a first embodiment. 1 is a diagram illustrating an example in which a three-dimensional space display system 1 according to a first embodiment is applied. FIG. 11 is a block diagram showing the configuration of a three-dimensional space display system 100 according to a second embodiment. 11 is a diagram illustrating an example in which a three-dimensional space display system 100 according to a second embodiment is applied. 10 is a characteristic diagram showing the relationship between the distance from the 3D display 30 to an object to be observed and the magnitude of blurring that occurs when reproducing the object. 1 is a characteristic diagram showing the relationship between the distance from the 3D display 30 to an object to be observed and the resolution (diameter of the circle of confusion) on the retina of an observer who views the reproduced object. 11 is a diagram showing an example of the relationship between size d and pitch p in an element cell. FIG. FIG. 13 is a diagram showing an example in which a point object is reproduced as an object point A'. 11 is a diagram showing an example of the brightness distribution of light rays (reproduced light) reproduced from an element cell; FIG. FIG. 13 is a diagram showing an example in which a point object is reproduced as an object point A″. FIG. 10 is a diagram showing an example in which a plurality of objects are reproduced using the method of FIG. 9 . 11 is a diagram for explaining a method of calculating reconstruction data for a hologram by applying a ray tracing method. FIG. 10 is a schematic diagram showing a manner in which an observer observes a reproduction point through a display surface. FIG. 1 is a schematic diagram showing how light rays reproduced from a display become divergent light, resulting in blurring of the reproduction point. 1 is a schematic diagram for explaining the divergence angle and magnitude of Fraunhofer diffraction by a circular aperture. FIG. 4 is a flowchart showing a flow of processing performed by the three-dimensional display 30 of the embodiment. FIG. 13 is a block diagram showing the configuration of a three-dimensional space display system 1A according to a modified example of the embodiment. 11A and 11B are diagrams illustrating an example in which a three-dimensional space display system 1A according to a modified example of the embodiment is applied. FIG. 1 is a schematic cross-sectional view illustrating the configuration of a conventional light field display using a microlens array. FIG. 1 is a schematic cross-sectional view illustrating the configuration of a conventional static display type light field display in which liquid crystal panels are stacked.

The following describes in detail the embodiments of the present invention with reference to the drawings. The three-dimensional spatial display system 1 is implemented, for example, by an optical device and an electrical circuit. In the drawings described below, the thickness and ratio of components may be exaggerated for ease of viewing, and the number of components may be reduced. Furthermore, the present invention is not limited to the following embodiments as they are, and can be embodied by appropriate combinations and modifications without departing from the spirit of the invention.

Figure 1 is a block diagram showing the configuration of a three-dimensional space display system 1 according to a first embodiment. The three-dimensional space display system 1 includes, for example, a communication unit 10, a stereoscopic camera 20, and a three-dimensional display 30. The communication unit 10 communicates with the outside world via a digital communication network NW.

The stereoscopic camera 20 is a camera that captures a three-dimensional image of an object to be observed, which is a subject, and is, for example, a stereo camera. The stereoscopic camera 20 transfers three-dimensional information of the object to be observed to the three-dimensional display 30 via the communication unit 10. The three-dimensional information here includes at least the incident direction and intensity of light rays incident on the imaging surface from the object, and may be obtained from two or more parallax image series or a combination of two-dimensional images and distance images, or the like, as long as it is information that indicates the space including the object to be observed.

There are various methods for acquiring three-dimensional information. For example, when the stereoscopic camera 20 is a stereo camera, one method is to acquire three-dimensional information by measuring depth information (hereinafter also referred to as depth information, depth distance, etc.) using images captured by each of the two cameras. Another method is to analyze a pattern projected onto an object to be photographed. Another method is a TOF method that measures the distance to an object to be observed by measuring the flight time of light. Any method can be used to acquire three-dimensional information as long as it can measure at least the range of social distance with the required resolution. In particular, the TOF method is preferable because it can accurately measure depth distances of several centimeters to several meters.

It is desirable that the range of space captured by the stereoscopic camera 20 is wide enough to allow the user to recognize the social distance space. For example, a space that extends 3.6 m deep at an angle of ±30 degrees and has an angle of view of 60 degrees or more is preferable. For example, a more realistic space can be captured with an angle of view of 80 degrees or more, equivalent to a wide-angle lens with a focal length of 25 mm in 35 mm film equivalent. Furthermore, it is desirable that the minimum resolution in the angular direction Δα is 0.033 degrees or less, which is a resolution equivalent to a visual acuity of about 0.5.

For example, if the resolution of the stereoscopic camera 20 is high vision (1080 x 1920 pixels), the angle of view must be 73 degrees or less in order to make the minimum resolution in the angular direction Δα 0.033 degrees or less. Also, if the resolution of the stereoscopic camera 20 is 4K (2160 x 3840 pixels), the minimum resolution in the angular direction Δα must be 146 degrees or less. Therefore, when photographing a social distance space with an angle of view of 80 degrees or more, it is desirable to use a stereoscopic camera 20 with a resolution of 4K or more.

The communication unit 10 exchanges three-dimensional information with external devices using a digital communication network NW capable of stably transferring three-dimensional video information. To stably transfer a video including a 4K resolution image and depth information for each pixel, a communication speed of, for example, 25 Mbps or more is desirable. When a mobile communication network is used as the digital communication network, for example, using a standard of 5G or higher makes it easier to exchange information with remote locations.

The three-dimensional display 30 is a computer device such as a PC (Personal Computer), a server device, or a cloud server that displays three-dimensional images. The three-dimensional display 30 includes, for example, a calculation unit 31, a control unit 32, a light source unit 33, a display unit 34, a light control unit 35, and a memory unit 36. Here, the three-dimensional display 30 is an example of a "light reproduction device". The calculation unit 31 is an example of a "signal processing unit". The control unit 32 is an example of a "signal processing unit". The display unit 34 is an example of a "stereoscopic image display unit". The light control unit 35 is an example of a "stereoscopic image display unit".

The calculation unit 31 and the control unit 32 are functional units that perform signal processing, and are realized, for example, by the CPU (Central Processing Unit) of the three-dimensional display 30 executing a program pre-stored in the storage unit 36. In addition, these functional units that perform signal processing may be realized as integrated circuits such as ASICs (Application Specific Integrated Circuits).

The calculation unit 31 calculates the components of the light rays (light ray direction and intensity) to be reproduced (displayed) for each element cell based on the three-dimensional information acquired from the stereoscopic camera 20. The element cells here will be explained in detail later.

The control unit 32 controls the light source unit 33, the display unit 34, and the light control unit 35 to reflect the direction and intensity of the light rays reproduced for each element cell. This makes it possible to display a space with a natural sense of distance and no blur. Note that if the light source unit 33 and the light control unit 35 in the three-dimensional display 30 are passive and do not require control, there is no need for the control unit 32 to control these functional units (the light source unit 33 and the light control unit 35).

When an image is displayed using only three-dimensional information acquired from the outside via the communication unit 10, without using the three-dimensional information acquired from the stereoscopic camera 20, it is possible to omit the stereoscopic camera 20 in the three-dimensional space display system 1. On the other hand, when an image is displayed on the three-dimensional display 30 using only the three-dimensional information from the stereoscopic camera 20, it is possible to omit the communication unit 10 in the three-dimensional display 30.

The light source unit 33 has a light source function including light emitters such as a laser, LED (Light-Emitting Diode), or EL (Electro-Luminescence), and is a functional unit that serves as the light source for the display unit 34. The light control unit 35 controls the direction and intensity of the light emitted by the light source unit 33 according to a control signal from the control unit 32.

The display unit 34 has a display function using display elements such as an LCD (Liquid Crystal Display), an OLED (Organic LED), or a DMD (Digital Mirror Device). The display unit 34 displays an image according to the control of the control unit 32.

The display unit 34 is generally a display device that displays two-dimensional images, such as an LCD, LED, OLED, or DLP (Digital Light Processing). However, this is not limited to this. The display unit 34 may be a type that scans a light source unit 33, such as a laser light source or an LED light source. In the case of a self-luminous device such as an LED or OLED, the display unit 34 has both a light source function and a display function. If the display unit 34 controls the direction of light using a diffraction pattern such as a hologram, the display function and the light control function can be realized in a single device.

In the following description, the display surface refers to the surface on which the pattern is displayed by the display device of the display unit 34, and when multiple display devices are used to display an image, refers to the surface closest to the viewer.

The storage unit 36 is configured by a storage medium, for example, a hard disk drive (HDD), a flash memory, an electrically erasable programmable read only memory (EEPROM), a random access read/write memory (RAM), a read only memory (ROM), or any combination of these storage media. The storage unit 36 stores programs for executing various processes of the three-dimensional display 30, and temporary data used when performing various processes. The storage unit 36 stores, for example, three-dimensional information acquired by the stereoscopic camera 20. The storage unit 36 stores the results of calculations performed by the calculation unit 31. The storage unit 36 stores information indicating the direction and intensity of light rays reproduced under the control of the control unit 32.

Figure 2 is a diagram illustrating an example in which the three-dimensional space display system 1 of the first embodiment is applied. The XY directions in Figure 2 indicate planar directions, and the Z direction indicates the vertical direction. The stereoscopic camera 20 is installed so that it can capture an image of the actual space JK to be observed. A plurality of actual images IM (actual images IM-1 to IM-7) are arranged in the actual space JK. The three-dimensional display 30 is installed so that the image to be displayed can be observed by the observer OB.

The stereoscopic camera 20 captures the physical space JK. The three-dimensional display 30 displays a reproduced space SK that reproduces (displays) the physical space JK captured by the stereoscopic camera 20. Note that in the example of FIG. 2, the stereoscopic camera 20 and the three-dimensional display 30 are shown overlapping, but they are in different positions in the Z direction and do not overlap. Also, this example shows a case where the imaging direction of the stereoscopic camera 20 is along the X-axis direction, but this is not limited to this. The position of the stereoscopic camera 20 may be such that it is possible to capture images of the physical space JK to be observed from any position or direction that the observer OB wishes to observe. Also, the number of stereoscopic cameras 20 is not limited to a single one, and multiple stereoscopic cameras 20 may be installed.

In the example shown in this figure, the three-dimensional space display system 1 functions as a three-dimensional image display communicator that realizes communication by having a time lag between the recording (imaging) and playback (display) of three-dimensional information. That is, the three-dimensional information of the physical space JK captured by the stereoscopic camera 20 is temporarily stored in the memory unit 36, and the desired three-dimensional image is then reproduced in the reproduction space SK at any time desired by the observer OB. This allows the observer OB to observe the physical image IM of the physical space JK at the time of imaging at any timing after imaging, even if the observer OB is not present at the time imaging is performed.

Note that, although the above shows an example of recording and playback with a time difference, this is not limiting. For example, the stereoscopic camera 20 and the three-dimensional display 30 may be installed in locations distant from each other, such as an entrance and a living room, and function as a three-dimensional video communicator that enables communication between distant locations where the other person cannot be directly seen. This allows the observer OB to experience (observe) a remote physical space JK without having to travel to the physical space JK.

Here, we will explain in detail the social distance space that is the subject of this application. A social distance space is not a space in which an object (subject) exists near the display, as in the space displayed by a conventional three-dimensional display (stereoscopic image display device). A social distance space is a space in which a subject exists at a position distant in the depth direction in the space displayed by the display. A social distance space is, for example, a space inside a room or a space in a park, and is a space in which an observer (subject) exists within that section. Alternatively, it is a space that is displayed when the display is used as a window and the outside space (such as the space inside a room) is observed through the window.

Edward Hall, an American cultural anthropologist, classifies interpersonal distance (personal space) between people into the following four distance zones:
1) Close distance 2) Personal distance 3) Social distance 4) Public distance

1) Close distance is a distance of about 0 to 0.45 m, which corresponds to the distance at which you can sense the other person's body temperature or smell. Close distance is the distance between two people with whom you have a very intimate relationship, and is an interpersonal distance where communication is mainly based on skin-to-skin contact, such as holding hands, and smell.
2) Personal distance is the distance between you and another person that is about 0.45 to 1.2 meters, and corresponds to the distance you keep between yourself and another person in order to maintain your independence. It is the distance at which you or the other person can reach out and touch each other, and is the interpersonal distance when communicating with a close friend or other person.
3) Social distance is a distance of approximately 1.2 to 3.6 meters between two people, at which it is difficult to touch the other person and is an interpersonal distance that is appropriate for communication in formal settings, such as conversations between colleagues at work.
4) Public distance is a distance of approximately 3.6 m or more from the other person, which is an inappropriate distance for communication between two people, and is the interpersonal distance when communication such as a speech or lecture is taking place.

Figure 3 is a block diagram showing the configuration of a three-dimensional space display system 100 according to the second embodiment. In the three-dimensional space display system 100 according to this embodiment, a plurality of the three-dimensional space display systems 1 shown in Figure 1 are provided, which are connected to each other via a digital communication network NW. This constitutes a three-dimensional image display communicator that enables natural communication between a plurality of remote locations. The three-dimensional information obtained by the stereoscopic camera 20 is compressed and/or converted as necessary by signal processing such as the calculation unit 31, and is transmitted to the communication destination via the communication unit 10.

The communication means used by the communication unit 10 is not particularly limited, but in order to send and receive three-dimensional information, it is preferable to have a communication means capable of transmitting large amounts of information at high speed, such as the 5G communication network mentioned above.

Figure 4 is a diagram illustrating an example in which the three-dimensional space display system 100 of the second embodiment is applied. The X and Y directions in Figure 4 indicate planar directions, and the Z direction indicates the vertical direction. The positions, directions, and number of stereoscopic cameras 20 are the same as in Figure 2, so their explanation is omitted. The same applies to the three-dimensional display 30. In the example of this figure, the three-dimensional space display system 100 functions as a three-dimensional image display communicator that realizes natural communication between two remote locations that are communicatively connected via a digital communication network NW.

That is, the three-dimensional information obtained by capturing images of the members present in the physical space JK-1 by the stereoscopic camera 20-1 is transmitted to the three-dimensional display 30-2 via the digital communication network NW. As a result, the three-dimensional display 30-2 displays a reproduced space SK-1 that is a reproduction of the space captured by the stereoscopic camera 20-1 (physical space JK-1).

Meanwhile, the three-dimensional information obtained by capturing an image of a member (in this example, one person) present in the physical space JK-2 by the stereoscopic camera 20-2 is transmitted to the three-dimensional display 30-1 via the digital communications network NW. As a result, the three-dimensional display 30-1 displays a reproduced space SK-2 that is a reproduction of the space (physical space JK-2) captured by the stereoscopic camera 20-2.

Here, the element cell of this embodiment will be described with reference to FIG. 5. FIG. 5 is a characteristic diagram showing the relationship between the distance from the 3D display 30 to the object to be observed and the magnitude of blurring that occurs when reproducing the object. The horizontal axis of FIG. 5 indicates the distance from the display. The vertical axis of FIG. 5 indicates the magnitude of blurring.

Generally, on a display that allows focus adjustment, as shown in Figure 13, the observer views the space in front of and behind the display surface, and when light rays in the same direction as the light spreading from the reproduction point (the point object to be reproduced) are reproduced in a size smaller than the observer's pupil, the observer can observe as if there were a point light source in space.

However, strictly speaking, the light rays reproduced from the display become spread due to various reasons as shown in Figure 14, which causes blurring in the reproduced image. In particular, when the element cells of the display that determine the direction of the light rays are small, the light will bend around the outside of the aperture due to the effect of diffraction caused by the element cells as apertures, causing it to spread and become blurred.

The spread of diffraction caused by an aperture can be approximated as Fraunhofer diffraction at positions away from the display surface, and in the case of a circular aperture, the spread angle can be calculated from the size of the Airy disk (the bright area that occurs in the center of the diffraction pattern). In other words, the distance between the optical axis and the smallest dark ring that can form in the far field away from the circular aperture can be expressed as follows (see Figure 15) when expressed as the spread angle θ of a ray of light that is parallel to the optical axis and passes through the end face of the circular aperture. Here, in (Equation 1), λ is the wavelength of light, and d is the diameter of the circular aperture.

θ=1.22×λ/d (Formula 1)

An aperture such as the one described above is a unit of area on the display that defines the direction of light rays. This unit is called an "element cell." For example, in a light field display that uses a microlens array (Figure 19), one lens corresponds to an element cell. In the case of a static display type light field display (Figure 20) in which liquid crystal panels or the like are stacked, the pixels of the display used become element cells.

In a light field display, the direction of light rays is controlled for each element cell, so in order to provide focus adjustment functionality, the element cells must be sufficiently smaller than the observer's pupil. The size of a human pupil is generally around 2-8 mm. Therefore, if the size of the element cell is 0.3 mm and the wavelength of light is 500 nm, the spread angle of the light rays can be expressed as follows from (Equation 1).

θ=1.22×500× ^10-6 /0.3
≒2.03× ^10-3 (rad)
≒ 0.12 (degrees)

In other words, in Figure 15, the size of the blur caused by light passing through a 0.3 mm element cell at a distance L = 3.6 m from the surface with the circular opening is 3600 x tan (0.12°) x 2 ≒ 15 (mm), which means the blur spreads over a length of about 15 mm. For example, if a person's face at a distance of 3.6 m is blurred by about 15 mm, the person can be recognized, but it will be difficult to read their facial expression.

Generally, a person with 1.0 vision has an angular resolution of 1/60 degrees with the naked eye. The size d of the element cell that produces the equivalent diffraction spread angle θ can be expressed as follows from (Equation 1), assuming a wavelength of 500 nm.

d=1.22×500×10-6/tan (1/60°)×2
= 4.2 mm

Similarly, the size of an element cell that generates blur, with an angular resolution of 1/60/0.7 degrees, equivalent to that of a person with 0.7 visual acuity, which is a requirement for a driver's license, is 2.9 mm. The minimum visual acuity without the need for glasses is 0.3, and the size of an element cell that generates blur, calculated using a similar method under these conditions, is 1.2 mm. With a visual acuity of 0.2, the size of an element cell that generates blur is 0.8 mm. From this, it can be said that an element cell size d of at least 0.8 mm or more is necessary to keep the blur to an acceptable level when observed.

Figure 5 shows the relationship between the distance L from the display and the degree of blur due to diffraction, with the element cell size d as a parameter. The element cell size d corresponds to d in Figure 15. That is, it is the element cell size d calculated above, and corresponds to the calculated size d = 4.2 mm, 2.9 mm, 1.2 mm, or 0.8 mm depending on the conditions.

As shown in Figure 5, if the distance from the display (L) is the same, the larger the element cell size (d), the smaller the blur. This reflects the fact that in (Equation 1), as d increases, the spread angle θ decreases.

The spacing (pitch p) at which element cells are arranged will now be explained with reference to FIG. 6. FIG. 6 is a characteristic diagram showing the relationship between the distance from the 3D display 30 to the object to be observed and the resolution (diameter of the circle of confusion) on the retina of the observer who views the reproduced object. The horizontal axis of FIG. 6 indicates the distance from the display. The vertical axis of FIG. 6 indicates the diameter of the circle of confusion.

Generally, the size of a human pupil is about 2 to 8 mm, and multiple light rays pass through this pupil to adjust the focus of the eye. To achieve this type of focus adjustment, the element cells must be arranged at a spacing (pitch p) such that light rays from at least two element cells enter the pupil. To achieve a more natural focus adjustment, it is desirable to have a larger number of light rays (number of element cells) entering the pupil. In other words, it is desirable to reduce the spacing (pitch p) between element cells in order to increase the number of element cells.

As shown in Figure 6, if the distance (L) from the observer to the object is the same, the smaller the pitch (p) of the element cells, the smaller the diameter of the circle of confusion. Since the spacing between photoreceptor cells on the human retina is approximately 10 μm (0.01 mm), in order to have better resolution (smaller diameter of the circle of confusion), an element cell pitch p of approximately 0.4 mm or less is required for an object more than 1.2 m away.

In addition, if the application allows for a resolution equivalent to that of a 24-inch XGA (Extended Graphics Array: a standard announced by IBM in 1990) display at a distance of 0.5 m (circle of confusion diameter of approximately 30 μm (0.03 mm) on the retina), then it can be seen that for objects more than 1.2 m away, the pitch p of the element cells should be set to 1.2 mm or less.

In summary, if communication is to be carried out at a social distance (a distance of approximately 1.2 m to 3.6 m from the display), communication without practical problems will be possible if the element cell size d is 0.8 mm or more and the element cell pitch p is 1.2 mm or less.

Note that the horizontal axis in Figure 6 is the distance from the observer to the object, but the distance from which the observer will observe the object in relation to the display surface of the device is not known at the time of design. For this reason, at the time of design, calculations are performed assuming that the observer is closest to the display surface, i.e., the distance from the observer to the object is the distance from the display surface to the object.

Figure 7 is a schematic diagram of a case where the pitch p of the element cells is greater than the size d of the element cells (p ≥ d). This is an example of the element cell size d being 0.8 mm or more and the pitch p of the element cells being 1.2 mm or less, as mentioned above. In this case, since the relationship p ≥ d holds, the element cells do not overlap. As a result, the diffraction grating patterns are also independent and do not overlap.

Figure 8 is a conceptual diagram of a display according to the present invention reproducing a point object as object point A'. Each element cell reproduces the direction of light emitted from object point A' on the display surface. When viewed from various directions above the drawing, the viewer can see as if object point A' exists from each direction.

In this embodiment, as explained in FIG. 6, it is assumed that the pitch p of the element cells is sufficiently small compared to the size of the pupil. Also, as explained in FIG. 5, it is assumed that the size d of the element cells is a size that causes little blurring due to diffraction. Therefore, the conditions necessary for stereoscopic vision, such as convergence, focus adjustment, and binocular parallax, are reproduced without any contradiction for the observer OB. Therefore, the observer OB does not experience eye strain. In other words, it is possible to reproduce a natural and comfortable space even in a space that is not close to the display surface or is far from the display surface.

On the other hand, as shown in Figure 8, the light beam emitted from each element cell has a width equal to the size of the element cell (d) plus the spread due to diffraction (Δα). Therefore, while there is no problem when observing a space far from the display surface, the resolution of the object decreases when observing an object close to the display surface.

There are several possible ways to address this issue. For example, as shown in Figure 9, it is possible to give the brightness distribution of the light rays reproduced from the element cell a characteristic distribution. Figure 9 is a diagram showing an example of the brightness distribution of the light rays (reproduced light) reproduced from the element cell. The upper part of Figure 9 is a characteristics diagram showing the relationship between the position within the element cell and the brightness of the reproduced light. The lower part of Figure 9 is a schematic diagram showing an image of the brightness distribution of the reproduced light emitted from the element cell.

As shown in Figure 9, the brightness of the light beam reproduced from the element cell is distributed so that it is brighter at the center and darker as it moves from the center to the periphery. In this way, it is possible to improve the resolution of the reproduced object. Creating such a brightness distribution of the light beam can be achieved by varying the diffraction efficiency within the element cell so that the transmittance of the interference fringe pattern recorded in the element cell decreases from the center to the periphery.

As a method of preventing a decrease in resolution, it is possible to adjust the size of object point A'' due to the rays of reconstructed light reproduced from each element cell, as shown in Figure 10. That is, an element cell is formed on the display surface, recording a spherical wave diverging from object point A'', that is, an interference fringe between the wavefront from the object point and the reference light. This makes it possible to reduce the size of object point A'' due to the rays reproduced from each element cell to the diffraction limit of the size d of the element cell, as shown in Figure 10.

One way to achieve this is, for example, to use a CGH (Computer-Generated Hologram) calculated for each element cell. With this method, a hologram of the wavefront and reference light is calculated when the light from the object reaches the position of the element cell. With this method, it is sufficient to perform calculations for each element cell. Therefore, the amount of calculations is smaller than with normal CGH calculations, as described below, and parallel calculations are also possible, allowing for high-speed calculations.

In this case, it is possible for just one element cell to fulfill the focus adjustment function. Therefore, even if the pitch p of the element cells is 1.2 mm or more, natural stereoscopic vision is possible. However, in order to smoothly change the image as the observer OB moves his/her viewpoint, it is desirable for the pitch p of the element cells to be equal to or smaller than the pupil size. For this reason, it is desirable for the pitch p of the element cells to be at least 7 mm or less, and preferably 2 mm or less. In other words, if the element cells are holograms that record spherical waves from an object, a higher resolution stereoscopic image can be observed by setting the element cell size d to 1.2 mm or more (equivalent to 0.5 visual acuity) and the element cell pitch p to 2 mm or less.

The manner in which multiple objects are reproduced using the method of FIG. 10 will be explained with reference to FIG. 11. In each element cell of the display surface, interference fringes between the spherical waves diverging from each point on the surface of the object and the reference light are recorded. From object B', which is relatively close to the display surface, a spherical wave diverging from a nearby light point is reproduced. On the other hand, from object C', which is relatively far from the display surface, a spherical wave diverging from a distant light point is reproduced. In this way, the wavefront is recorded differently depending on the distance from the display surface to the object.

In this embodiment, the interference fringes between the spherical waves emanating from each point on the surface of the object and the reference light are digitized through a stereoscopic camera 20. This is similar to conventional digital holograms, but this embodiment is characterized by sampling the object. That is, as shown in FIG. 11, the points at which the object is sampled are resolved at an angle of Δα from each element cell position.

As a result, while conventional digital holograms require wavefront calculations at a sampling pitch on the order of μm, the method of this embodiment only requires sampling at a pitch of a few mm to a few cm. This makes it possible to reduce the enormous amount of calculations required in conventional methods.

In addition, with the method of this embodiment, the sampling interval (sampling pitch) increases the further away from the display surface. This makes the method of this embodiment suitable for reproducing a wide space away from the display surface.

In a holographic stereogram, a three-dimensional image is created to reproduce the direction of light rays. This makes it possible to create data for displaying a three-dimensional image from images of an object taken from multiple directions. Therefore, using CG (computer graphics) techniques, which have been researched in various ways, it is possible to reproduce not only the shape of an object, such as a glossy or transparent object, but also its texture. Furthermore, by capturing an image of the actual object, it is also possible to reproduce a three-dimensional image of the actual object.

For example, a method of calculating a hologram pattern by applying ray tracing, which is one of the CG techniques, will be described with reference to FIG. 12. First, the center of each element cell is set as the starting point of the light ray emitted by the ray tracing method. Next, the ray tracing method is performed with the center of each element cell as the starting point to find the intersection between the light ray and the object to be the subject. This results in a set of point light sources from different viewpoint positions for each element cell, making it possible to create a pattern of element cells with parallax up, down, left, and right. The object (subject) here may be a three-dimensional object created based on three-dimensional information obtained from information captured by the stereoscopic camera 20, or may be a virtual object created using CAD (computer-aided design) or the like. In addition, if only the direction of the light ray is considered in this calculation, the image will be reproduced by the light ray as shown in FIG. 8. On the other hand, if both the direction of the light ray and the distance to the object point are considered in this calculation, the image will be reproduced by the light ray as shown in FIG. 10 or FIG. 11.

Here, the flow of processing performed by the 3D display 30 of the embodiment will be explained using the flowchart in FIG. 16. FIG. 16 shows the flow of calculation processing for a hologram pattern when the direction of the light ray and the distance to the object point are taken into consideration.

First, the three-dimensional display 30 obtains three-dimensional information of the object to be displayed on the display (step S10). Next, the three-dimensional display 30 determines the position of the center of the element cell to be calculated (step S11), and determines the intersection points between the object and each line that is emitted from the starting point and differs in angle by Δα, starting from the center position of the element cell (step S12). The three-dimensional display 30 then determines the intersection points with each object as object points, and determines the sum of the complex amplitudes of the spherical waves emanating from each object point at the element cell position (step S13). Note that the complex amplitudes determined here may be within the range of the size of the element cell.

The three-dimensional display 30 performs the above steps (steps S11 to S13) for all element cells (steps S14 and S17).

Then, the three-dimensional display 30 obtains the complex amplitude on the display surface by calculating the sum of the complex amplitudes of all element cells (step S15). Next, the three-dimensional display 30 obtains the pattern of interference fringes between the wavefront of the reference light and the complex amplitude on the display surface (step S16). This allows the three-dimensional display 30 to obtain the pattern of the hologram to be displayed on the display.

In the process shown in the above flowchart, the sum of the complex amplitudes is calculated (step S15) rather than the sum of the interference fringe patterns for each element cell, and then the interference fringe pattern with the reference light is calculated (step S16). In this way, the 3D display 30 can record and play back a 3D image of an object as information including both the direction of the light rays and the distance to the object point.

In the process shown in the above-mentioned flowchart, the sum of the complex amplitudes of the element cells is calculated, and then the interference pattern with the reference light is calculated, but this is not limited to the above. The three-dimensional display 30 may calculate the sum of each interference pattern after determining the interference pattern with the reference light for each element cell. In this case, the three-dimensional display 30 can perform calculations for each element cell. This makes parallel calculations easier and reduces the time required for calculations.

The recorded stereoscopic image (three-dimensional information of an object) may be a stereogram that takes into account only horizontal parallax, but to make focus adjustment more effective, it is preferable to use a stereogram that has parallax in both the horizontal and vertical directions. In addition, in the above-mentioned embodiment, circular cells are used as element cells, but this is not necessary. The shape of the element cells may be a polygonal shape such as a triangle, square, pentagon, or hexagon, or may be a star, ellipse, rectangle, or other shape.

In addition, it is preferable to use a monochromatic light source such as a laser or LED as a light source for reproducing a holographic stereogram, or a light source that combines a normal light source with a filter. This is to prevent blurring caused by differences in diffraction angles due to wavelengths.

When using a laser light source as the light source, it is desirable to take measures to reduce the coherence. This is to reduce noise caused by speckle. Possible methods for reducing the coherence of a laser light source include passing the light through an optical fiber, vibrating the light source, changing the optical path length, inserting a moving diffusing element into the optical path, and combining multiple light sources.

In the above, the social distance is set to a distance of approximately 1.2 m to approximately 3.6 m, but it is not necessary for all objects reproduced in the space to exist within this distance range. It is sufficient that the object to be observed exists at least within this social distance range. Furthermore, the reproduced object (object) is not limited to a person, but may be an animal or a robot. Furthermore, the reproduced object (object) may be a two-dimensional image reproduced in the space. Furthermore, it may be a building that suggests the presence of a communication target, such as a desk, chair, or table placed in the space. Furthermore, the reproduced object does not have to be something that directly communicates. For example, the natural ground that is observed when remotely operating heavy machinery may exist within the social distance range. The same applies to remote surgery, the operation of a robot arm in outer space, and the operation of an unmanned reconnaissance aircraft in the military.

As explained using Figures 5 and 6, the present invention makes it possible to reproduce a wide space with little blurring even when the depth of the space exceeds 3.6 m. For example, the present invention can be used to express a space that exceeds social distance, such as a wide space such as a landscape or a space that includes large objects such as a building or large plants and animals.

In addition, when observing the display through an optical system such as an eyepiece, the conditions of the size d of the element cells and the pitch p of the element cells may be corrected based on the magnification of the optical system. For example, consider a case where the size d of the element cells is 1.0 mm and the pitch p of the element cells is 1.2 mm when the distance from the display is a social distance of approximately 1.2 m to 3.6 m and there is no eyepiece. In this case, when this embodiment is applied to a head-mounted display or the like and the magnification of the eyepiece attached to the head-mounted display or the like is 2x, the three-dimensional display 30 corrects the size d of the element cells to 1.0/2 = 0.5 mm and the pitch p of the element cells to 1.2/2 = 0.6 mm. Conversely, when the magnification of the optical system is 0.5 using a reduced optical system, the three-dimensional display 30 corrects the size d of the element cells to 1.0/0.5 = 2.0 mm and the pitch p of the element cells to 1.2/0.5 = 2.4 mm.

In other words, the corrected size d# and corrected p# are expressed by the following formulas. In the formulas below, d is the size before correction, p is the pitch before correction, and BR is the magnification of the optical system such as the eyepiece lens.

d#=d/BR
p#=p/BR

When observing the display surface directly without using eyepieces, it is desirable to be able to observe with both eyes simultaneously in order to obtain the effect of convergence. Since the average interocular distance is approximately 60 mm, it is desirable for the size of the display surface to be at least 60 mm in the long axis direction.

(Modification of the embodiment)
Here, a modified example of the embodiment will be described. This modified example differs from the above-described embodiment in that a virtual object (hereinafter, a virtual object) is reproduced in the reproduction space. The virtual object is, for example, a virtual character.

Figure 17 is a block diagram showing the configuration of a three-dimensional space display system 1A in a modified example of the embodiment. The three-dimensional space display system 1A includes, for example, a communication unit 10 and a three-dimensional display 30. In other words, in this modified example, it is possible to omit the stereoscopic camera 20.

The communication unit 10 acquires three-dimensional information of a virtual object from the outside. The virtual object includes not only the object to be observed, but also three-dimensional information of the reproduced space, such as the background. The three-dimensional display 30 uses the three-dimensional information of the virtual object acquired via the communication unit 10 to reproduce and display, for example, the space in which the virtual object exists at a social distance.

Alternatively, the three-dimensional display 30 may be provided with a functional unit that creates three-dimensional information of a virtual object. Alternatively, the three-dimensional display 30 of this modified example may use three-dimensional information of a virtual object that is stored in advance in the storage unit 36. In this case, the communication unit 10 can be omitted in the three-dimensional space display system 1.

Figure 18 is a diagram illustrating an example in which a three-dimensional space display system 1A in a modified embodiment is applied. In Figure 18, a reproduction space SK in which a three-dimensional image of a virtual object generated by the configuration shown in Figure 17 exists as a reproduction image SIM (in this example, reproduction images SIM1 to SIM7) can be displayed on a display. In this way, by using the three-dimensional display 30 of this modified embodiment, more natural communication can be carried out in a social distance space with depth that allows social distance with non-existent people, such as people or characters created in a virtual space, or avatars of communication partners sent from other systems.

The means of communication in this modified example is not limited to a specific means. For example, the three-dimensional space display system 1A may be applied as a means of communicating with a character. The character here is a virtual character displayed as a virtual object.

In this case, the three-dimensional space display system 1 includes, for example, a live camera and a processor that performs signal processing to display a three-dimensional space image in which a character has a predetermined reaction. The live camera captures an image of the user. The processor recognizes the gestures of the user from the image captured by the live camera, determines the reaction that the character should have based on the gesture, and displays an image of the character having the determined reaction. This makes it possible to communicate with the character through gestures.

Alternatively, the three-dimensional space display system 1A includes a microphone, a speaker, and a processor that performs signal processing to display a three-dimensional space image in which a character has a specified reaction. The user's voice is input to the microphone. The processor determines a voice response in response to the user's voice input from the microphone, and outputs the determined response from the speaker. The processor also determines a reaction to be made by the character in response to the user's voice, and displays an image of the character having the determined reaction. This makes it possible to communicate with the character through voice.

In addition, in this modified example, the virtual object may not be CG (Computer Graphics), but may be a live-action video image captured in advance by a stereoscopic camera or the like. Even in such a case, it is possible to interact (communicate) with the virtual object by switching the video image played as a reaction in response to gestures, voice input, or other input from the user as described above.

In addition, if the virtual object reproduced (displayed) by the three-dimensional space display system 1A is a stationary object, the display unit 34 of the three-dimensional display 30 may be configured to display an unchanging (static) image such as a printed matter.

The image displayed by the display unit 34 of the three-dimensional display 30 may be an image in which a hologram pattern is drawn using a fine patterning device such as an electron beam drawing device, or an image in which the drawn hologram pattern is replicated. In this way, by using a fixed hologram pattern (still image) as the image to be displayed, it is possible to reproduce a large space at low cost. In this case, the display unit 34 controls the direction of light by the hologram pattern. The display unit 34 displays the hologram pattern as at least one of a virtual image or a real image by the light beam emitted by each element cell. Therefore, the display function and the light control function are realized by one device. In such a case, it is not possible to make the virtual character displayed as a virtual object react, but it is possible to establish pseudo-audio communication with the virtual object as described above. In addition, the light control unit 35 may display a still image such as a fixed hologram pattern together with the display unit 34 or instead of the display unit 43. The display unit 34 is an example of a "stereoscopic image display unit". The light control unit 35 is an example of a "stereoscopic image display unit". Additionally, an image in which a hologram pattern is drawn is an example of a "stereoscopic image." An image in which the drawn hologram pattern is replicated is an example of a "stereoscopic image."

As described above, the three-dimensional display 30 of the embodiment reproduces light rays virtually emitted from a three-dimensional image when the image is reproduced in a reproduction space.

The three-dimensional display 30 of the embodiment includes a display unit 34 and/or a light control unit 35. The display unit 34 and/or the light control unit 35 are an example of a "stereoscopic image display unit." The display unit 34 and/or the light control unit 35 displays a stereoscopic image as at least one of a virtual image and a real image by light emitted by each element cell included in an element cell set consisting of a plurality of element cells arranged two-dimensionally corresponding to a reproduction screen. The display unit 34 and/or the light control unit 35 displays the stereoscopic image in an area in which the distance in the depth direction in the reproduction space corresponds to the social distance. In the three-dimensional display 30, the size d of the element cells and the pitch p of the element cells are values determined according to the degree to which the stereoscopic image reproduced in the reproduction space is observed by the observer. The stereoscopic image is reproduced in an area in which the distance in the depth direction in the reproduction space corresponds to the social distance.

As a result, the three-dimensional display 30 of the embodiment can determine the size d of the element cells and the pitch p of the element cells so that a three-dimensional image at a social distance in the reproduction space can be clearly seen by the observer OB. Therefore, the social distance space can be reproduced as a three-dimensional space that provides a natural sense of distance and has little blurring.

The three-dimensional display 30 of the embodiment also includes a calculation unit 31 and/or a control unit 32. The calculation unit 31 and/or the control unit 32 are an example of a "signal processing unit." The calculation unit 31 and/or the control unit 32 calculate the direction of the light ray to be reproduced for each element (element cell) of the element cell group. The element cells are arranged two-dimensionally corresponding to the reproduction screen. The element cells correspond to each element obtained by dividing a group of multiple light rays emitted from the surface of the three-dimensional image according to the position on the reproduction screen where each light ray reaches. This provides the same effect as described above.

In addition, in the three-dimensional display 30 of the embodiment, the size d of the element cell is determined according to the amount of blurring that occurs in the reproduced three-dimensional image. This allows the size d of the element cell to be determined so that the amount of blurring is kept to an acceptable level, making it possible to reproduce a three-dimensional image with little blurring.

The pitch p of the element cells is determined according to the resolution on the retina of the observer who views the reproduced three-dimensional image. This allows the pitch p of the element cells to be determined so that focus adjustment is possible, making it possible to reproduce a three-dimensional image that the observer OB can focus on.

The three-dimensional space display system 1 (1A, 100) and the three-dimensional display 30 in the above-mentioned embodiment may be realized in whole or in part by a computer. In that case, a program for realizing this function may be recorded in a computer-readable recording medium, and the program recorded in the recording medium may be read into a computer system and executed to realize the function. Note that the term "computer system" here includes hardware such as an OS and peripheral devices. Furthermore, the term "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, and storage devices such as hard disks built into a computer system. Furthermore, the term "computer-readable recording medium" may include a medium that dynamically holds a program for a short period of time, such as a communication line when a program is transmitted via a network such as the Internet or a communication line such as a telephone line, and a medium that holds a program for a certain period of time, such as a volatile memory inside a computer system that is a server or client in such a case. Furthermore, the above-mentioned program may be a program for realizing a part of the above-mentioned function, or may be a program that can realize the above-mentioned function in combination with a program already recorded in the computer system, or may be a program that is realized using a programmable logic device such as an FPGA.

The above describes an embodiment of the present invention in detail with reference to the drawings, but the specific configuration is not limited to this embodiment, and includes designs that do not deviate from the gist of the present invention.

1, 1A, 100...3D space display system, 10...communication unit, 20...stereoscopic camera, 30...3D display (light reproduction device), 31...arithmetic unit (signal processing unit), 32...control unit (signal processing unit), 33...light source unit, 34...display unit (stereoscopic image display unit), 35...light control unit (stereoscopic image display unit), 36...storage unit

Claims (11)

A light beam reproducing device for reproducing light beams virtually emitted from a stereoscopic image when the stereoscopic image is displayed in a reproduction space, comprising:
a stereoscopic image display unit that displays the stereoscopic image as at least one of a virtual image and a real image by light rays emitted from each element cell included in an element cell set consisting of a plurality of element cells that are two-dimensionally arranged corresponding to a reproduction screen on which the plurality of light rays emitted from the surface of the stereoscopic image reach;
Equipped with
the stereoscopic image display unit displays the stereoscopic image in an area in the reproduction space where a distance in a depth direction corresponds to a social distance,
the stereoscopic image is displayed within a range of at least 1.2 m to 3.6 m in the depth direction from the display surface;
a size of an element cell which is each element in the element cell set, and a pitch of the element cells when the element cells are two-dimensionally arranged are values determined according to a degree to which the stereoscopic image displayed in the reproduction space is observed by a viewer,
a size of the element cell is determined so that a spread angle of diffracted light from the element cell is equal to or smaller than an angular resolution according to the visual acuity of the observer;
The size of the element cell is 0.8 mm or more, and the pitch of the element cell is 1.2 mm or less.
Light reproduction device. A light beam reproducing device for reproducing light beams virtually emitted from a stereoscopic image when the stereoscopic image is displayed in a reproduction space, comprising:
a stereoscopic image display unit that displays the stereoscopic image as at least one of a virtual image and a real image by light rays emitted from each element cell included in an element cell set consisting of a plurality of element cells that are two-dimensionally arranged corresponding to a reproduction screen on which the plurality of light rays emitted from the surface of the stereoscopic image reach;
Equipped with
the stereoscopic image display unit displays the stereoscopic image in an area in the reproduction space where a distance in a depth direction corresponds to a social distance,
the stereoscopic image is displayed within a range of at least 1.2 m to 3.6 m in the depth direction from the display surface;
a size of an element cell which is each element in the element cell set, and a pitch of the element cells when the element cells are two-dimensionally arranged are values determined according to a degree to which the stereoscopic image displayed in the reproduction space is observed by a viewer,
a size of the element cell is determined so that a spread angle of diffracted light from the element cell is equal to or smaller than an angular resolution according to the visual acuity of the observer;
The size of the element cell is 1.2 mm or more, and the pitch of the element cell is 7 mm or less.
Light reproduction device. a signal processing unit that divides a set of a plurality of the light rays emitted from a surface of the stereoscopic image in accordance with a position on the reproduction screen, associates each element of the element cell set with each of the divided elements of the plurality of the light rays, and calculates one or more components of the light rays to be reproduced for each element of the element cell set,
3. The light reproducing device according to claim 1 or 2 . the pitch of the element cells is determined according to a resolution on the retina of an observer who observes the displayed stereoscopic image when the stereoscopic image is displayed in an area in a reproduction space where the distance in the depth direction corresponds to a social distance;
The light reproducing device according to any one of claims 1 to 3. The size of the element cell is determined to be smaller than the pitch of the element cell.
5. The light reproducing device according to claim 1. The element cell is a hologram that records a wavefront from a stereoscopic image.
6. A light reproducing device according to claim 1. A light beam reproduction device according to any one of claims 1 to 6 ; a stereoscopic camera that outputs three-dimensional information of a stereoscopic image to the light beam reproduction device;
A three-dimensional space display system comprising: A light beam reproduction method for a light beam reproduction device having a stereoscopic image display unit which reproduces light beams virtually emitted from a stereoscopic image when the stereoscopic image is displayed in a reproduction space, and displays the stereoscopic image as at least one of a virtual image and a real image by light beams emitted from each element cell included in an element cell set consisting of a plurality of element cells two-dimensionally arranged corresponding to a reproduction screen, comprising:
the stereoscopic image display unit displays the stereoscopic image in an area in the reproduction space where the distance in the depth direction corresponds to a social distance;
the stereoscopic image is displayed within a range of at least 1.2 m to 3.6 m in the depth direction from the display surface;
a size of an element cell which is each element in the element cell set, and a pitch of the element cells when the element cells are two-dimensionally arranged are values determined according to a degree to which the stereoscopic image displayed in the reproduction space is observed by a viewer,
a size of the element cell is determined so that a spread angle of diffracted light from the element cell is equal to or smaller than an angular resolution according to the visual acuity of the observer;
The size of the element cell is 0.8 mm or more, and the pitch of the element cell is 1.2 mm or less.
Light reproduction method. A light beam reproduction method for a light beam reproduction device having a stereoscopic image display unit which reproduces light beams virtually emitted from a stereoscopic image when the stereoscopic image is displayed in a reproduction space, and displays the stereoscopic image as at least one of a virtual image and a real image by light beams emitted from each element cell included in an element cell set consisting of a plurality of element cells two-dimensionally arranged corresponding to a reproduction screen, comprising:
the stereoscopic image display unit displays the stereoscopic image in an area in the reproduction space where the distance in the depth direction corresponds to a social distance;
the stereoscopic image is displayed within a range of at least 1.2 m to 3.6 m in the depth direction from the display surface;
a size of an element cell which is each element in the element cell set, and a pitch of the element cells when the element cells are two-dimensionally arranged are values determined according to a degree to which the stereoscopic image displayed in the reproduction space is observed by a viewer,
a size of the element cell is determined so that a spread angle of diffracted light from the element cell is equal to or smaller than an angular resolution according to the visual acuity of the observer;
The size of the element cell is 1.2 mm or more, and the pitch of the element cell is 7 mm or less,
Light reproduction method. a computer of a light beam reproduction device including a stereoscopic image display unit which reproduces light beams virtually emitted from a stereoscopic image when the stereoscopic image is displayed in a reproduction space, and displays the stereoscopic image as at least one of a virtual image and a real image by light beams emitted from each element cell included in an element cell set consisting of a plurality of element cells arranged two-dimensionally corresponding to a reproduction screen;
a signal processing means for dividing a set of a plurality of said light rays emitted from a surface of said stereoscopic image in accordance with a position on said reproduction screen, for associating each element of said element cell set with each of said divided elements of said plurality of said light rays, and for calculating one or more components of said light rays to be reproduced for each element of said element cell set;
A program that functions as
the stereoscopic image display unit displays the stereoscopic image in an area in the reproduction space where a distance in a depth direction corresponds to a social distance,
the stereoscopic image is displayed within a range of at least 1.2 m to 3.6 m in the depth direction from the display surface;
a size of an element cell which is each element in the element cell set, and a pitch of the element cells when the element cells are two-dimensionally arranged are values determined according to a degree to which the stereoscopic image displayed in the reproduction space is observed by a viewer,
a size of the element cell is determined so that a spread angle of diffracted light from the element cell is equal to or smaller than an angular resolution according to the visual acuity of the observer;
The size of the element cell is 0.8 mm or more, and the pitch of the element cell is 1.2 mm or less.
program. a computer of a light beam reproduction device including a stereoscopic image display unit which reproduces light beams virtually emitted from a stereoscopic image when the stereoscopic image is displayed in a reproduction space, and displays the stereoscopic image as at least one of a virtual image and a real image by light beams emitted from each element cell included in an element cell set consisting of a plurality of element cells arranged two-dimensionally corresponding to a reproduction screen;
a signal processing means for dividing a set of a plurality of said light rays emitted from a surface of said stereoscopic image in accordance with a position on said reproduction screen, for associating each element of said element cell set with each of said divided elements of said plurality of said light rays, and for calculating one or more components of said light rays to be reproduced for each element of said element cell set;
A program that functions as
the stereoscopic image display unit displays the stereoscopic image in an area in the reproduction space where a distance in a depth direction corresponds to a social distance,
the stereoscopic image is displayed within a range of at least 1.2 m to 3.6 m in the depth direction from the display surface;
a size of an element cell which is each element in the element cell set, and a pitch of the element cells when the element cells are two-dimensionally arranged are values determined according to a degree to which the stereoscopic image displayed in the reproduction space is observed by a viewer,
a size of the element cell is determined so that a spread angle of diffracted light from the element cell is equal to or smaller than an angular resolution according to the visual acuity of the observer;
The size of the element cell is 1.2 mm or more, and the pitch of the element cell is 7 mm or less.
program.

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