JPH10288939A - Method and apparatus for generating computer generated hologram using depth buffer - Google Patents

Abstract

(57) [Summary] [Problem] To provide a computer generated hologram generating method and apparatus capable of displaying only an object visible from a specific viewpoint and generating a hologram capable of expressing occlusion at high speed. SOLUTION: A display target space is managed in a computer, a depth buffer when a viewpoint is present on a hologram is generated, and information of an object located at a closest distance from the viewpoint is registered in the depth buffer. A point light source is assumed only for the object registered in the depth buffer, and the wavefront on the hologram surface is calculated. After calculating the wavefronts for all objects on the depth buffer, the sum of these wavefronts is taken as the object wavefront at the viewpoint on the hologram surface. Then, the viewpoint is moved on the hologram surface, the object wavefront on the hologram surface is obtained, and interference fringes with the reference light are calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a computer generated hologram generation technique for generating and displaying a hologram by a computer and displaying the generated hologram as a stereoscopic image.

[0002]

2. Description of the Related Art In order to realize a hologram by a computer, a method is first used in which an object is described by a point light source, and an interference fringe between a wavefront from each point light source and a reference light is obtained by numerical calculation. I have. In this calculation method, when a point light source O constituting an object is a distance r from the point light source O, it is defined by the following equation.

O = (a _o / r) e ^jkr (1) Then, the amplitude of the wavefront at the distance r from the point light source O to the hologram surface is calculated. Here, a _o is the luminance of the point light source, λ is the wavelength of light, and k = 2π / λ. Then, a wavefront of the reference light is added to the sum of the amplitude values on the hologram surface obtained from each point light source to generate interference fringes as a hologram.

However, in this method, since the object is described by the point light source, it is not possible to represent the shielding between the objects, and only to describe a transparent object or a wire frame object.

In order to express the occlusion, a line connecting the individual points describing the object is obtained by focusing only on the horizontal parallax, and it is determined which point is occluded by the line.
There has been a method of calculating the wavefront of a point only at an unobstructed point (Yoshikawa, Matsumaru, “Hidden Surface and Shading Process for Electronic Hologram Display”, 1
992 Autumn Meeting of the Institute of Electronics, Information and Communication Engineers, D-229).

[0006]

In order to accurately calculate a hologram, it is necessary to determine the interference of a wavefront caused by a point light source. However, as the shape of an object becomes complicated, it is necessary to express the shape of the object. Therefore, the number of point light sources increases. Since the hologram calculates the wavefront interference of each point light source, an enormous amount of calculation is required as the number of point light sources increases.
Even when calculating an image (interference fringe) of one frame, it took several minutes to several hours. In addition, in the conventional hidden surface elimination method, since the shielding state is investigated for each point, as the number of points increases, the process of detecting the shielding state between points becomes complicated, and only the conventional horizontal parallax is used. It is difficult to simply extend the method of (1) to bidirectional parallax.

It is therefore an object of the present invention to provide a computer generated hologram generating method and apparatus capable of displaying only an object visible from a specific viewpoint and generating a hologram capable of expressing occlusion at a high speed.

[0008]

As a method for solving the above problems, the present invention provides a computer generated hologram generation method for calculating interference fringes between light from an object and reference light by calculating each pixel on a hologram surface. A step of generating a depth buffer as a viewpoint, a step of calculating the sum of wavefronts on the hologram surface when a point light source is located at the position of the object registered in the depth buffer, and Generating a hologram interference fringe by combining the wavefront of the reference light with the sum of the wavefronts.

In the process of obtaining the sum of the wavefronts on the hologram surface when the point light source is located at the position of the object registered in the depth buffer, the point light sources at the position of the object are processed in parallel. After calculating the wavefront at each viewpoint on the hologram surface, the sum of the wavefronts is obtained.

According to another aspect of the present invention, there is provided a computer generated hologram generating apparatus for obtaining an interference fringe between light from an object and reference light by a computer. A means for generating and managing a depth buffer with each pixel on the hologram surface as a viewpoint with reference to a managed display object, a hologram managing means for managing a matrix for hologram calculation, and using the managed matrix, Means for calculating the wavefront and the sum of the wavefronts on the hologram surface when the point light source is assumed to be at the position of the object registered in the depth buffer, and the wavefront of the reference light, and the sum of the calculated wavefronts and Means for synthesizing the wavefront of the reference light.

According to the present invention, a display target space is managed in a computer, a depth buffer is generated when a viewpoint is on a hologram surface, and a point light source is generated only for an object (portion) registered in the depth buffer. And the wavefront on the hologram plane is calculated. After calculating the wavefronts for all objects on the depth buffer, the sum of these wavefronts is
The object wavefront at the viewpoint on the hologram surface. Then, the viewpoint is moved on the hologram surface, the object wavefront on the hologram surface is obtained, and interference fringes with the reference light are calculated.

By using the depth buffer, only objects that can be seen from a specific viewpoint are subjected to the wavefront calculation, so that occlusion can be expressed.

Further, since the invisible part is excluded from the calculation target, the calculation amount can be greatly reduced, and the interference fringes can be generated at high speed.

Further, since the processing in each of the depth buffers is independent, high-speed operation can be performed by parallel processing.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a flow chart for explaining an embodiment of the method of the present invention. In order to explain the present embodiment, consider a system as shown in FIG. As an example,
In order to calculate the interference fringes on the hologram surface 21, the visible space (called a view volume) when the viewpoint 24 is placed at the position of each pixel (i, j) on the hologram surface 21 is assumed to be 22. Then, it is assumed that the depth buffer 23 for generating a projection image that can be seen at the viewpoint 24 (coordinates (i, j) on the hologram surface) is 23. Here, the element (u, v) of the depth buffer 23 corresponds to a minute space (a quadrangular pyramid having the viewpoint as a vertex) 25 that can be seen from the viewpoint 24. The object existing therein becomes the processing target object corresponding to the element (u, v) of the depth buffer.

First, each pixel (i,
j) The corresponding matrix H (p, i, j, c), p =
1,2,3, i = 1, ... I, j = 1, ... J, c = R,
G and B are created. After clearing the contents of the matrix (step 101), each element (i, j) of the matrix
Are sequentially scanned. Here, since the element of p represents a point light source described by a complex amplitude, a place for storing p = 1 (real part), p = 2 (imaginary part), and p = 3 (interference fringe) Has become. Also, c represents the value of the color (RGB component) of the target object.

First, a depth buffer Z (u, v) 23 when the point (i, j) is set as the viewpoint 24 is created (step 102). FIG. 3 is a diagram for explaining an example of registration in the depth buffer, where 31 in FIG. 3A shows the correspondence between the target object in the view volume and the depth buffer, and FIG. 32 is a diagram showing an example of each element value of the depth buffer.

In the depth buffer Z (u, v) 23, as shown at 24 in FIG. 2, each space 25 of the view volume 22 corresponds to each element (u, v). Then, as shown at 31 in FIG.
The object information (position, color information, etc.) at a distance to the closest position to the viewpoint when viewed from is registered (step 103). For example, reference numeral 31 in FIG. 3 is a diagram showing a state in a certain horizontal section in FIG. 2, and the depth buffer Z (u
The object corresponding to the position of (+1, v) 23 includes c, d, and e, and information of the object e closest to the viewpoint is registered in the depth buffer Z (u + 1, v) 23.

Hereinafter, similarly, the depth buffer Z23
For each element (u, v) of, an object visible in each line of sight direction is registered in the depth buffer Z23. As a result, FIG.
A matrix Z in which the distance to the visible object in the line-of-sight direction is registered in each element (u, v) as shown at 32 in (b). (The example of 32 in FIG. 3 is an example in which only the distance information to the hologram surface is presented. However, the degree of the matrix of the depth buffer is increased, or a plurality of pieces of information are stored in the same place using an object-oriented language. It is possible to calculate the wavefront of the light on the hologram surface when there is a point light source at the position of the object registered in each element (u, v) of the matrix Z. (Step 104). At this time, as the surface luminance of the point light source, that is, the amplitude value a, a value corresponding to the luminance of the object surface at the position (or the luminance of each of RGB) is used. When the object O is represented by a polygon or the like, for example, this element (u, v)
Is obtained, and a distance r ′ from the center of gravity to the viewpoint in that area,
The distance r from the hologram surface (i, j) to the object and the luminance (amplitude value) RGB, a _OR , a _OG , a _OB, are determined based on the average luminance value of each color (RGB) (here, The method for determining the distance and the method for determining the attribute information of the object such as the color are not specified in the present embodiment.)

The point light source is represented by (a _OR / r) e ^jkr , (a _OG / r) e ^jkr , (a _OB / r) e ^jkr (2) for each color of RGB. Using the distance r between the position (l, u, v) and each viewpoint (i, j), for example, for red (R), (a _OR / r) e ^jkr (3) is calculated. Similarly, calculation is performed for green (G) and blue (B) (step 105).

After calculation for all u and v (step 106), the sum S (p, u, v, c) of the wavefronts from the object at the viewpoint (i, j) is obtained (step 10).
7).

S (1, u, v, c) = Σ _u , _v (a _Oc / r) cos (kr) (4) S (2, u, v, c) = Σ _u , _v (a _Oc / R) sin (kr) (5) Here, a _Oc represents the amplitude value of the color c = R, G, and B of the object O. In order to generate a full-color image in RGB, Equations that differ only in the value of a _Oc are separately calculated for each of the three patterns.

The above scanning is performed for all (i, j), and the wavefront on the hologram surface due to the light from the object is calculated (step 108). Next, the wavefront (amplitude value: b) of the reference light is calculated as the sum S (p, u, v,
The interference fringe is completed by adding to step c) (step 1).
09). That is, H (1, i, j, c) = (b / r) cos (kr) + S (1, u, v, c) (6) where RGB full color is used, the wavelength of the reference light , So that k is also different,
An interference fringe will be generated. After that, the interference fringes are displayed on a display device, and the three-dimensional images can be presented by full-color holograms by irradiating RGB reference lights and combining the images of the respective colors.

Next, an embodiment of the computer generated hologram generating apparatus according to the present invention having the above-described characteristic portions will be described. FIG. 4 is a block diagram showing the configuration. In FIG. 4, reference numeral 41 denotes a depth buffer generation unit that generates and manages a depth buffer; 42, a wavefront calculation unit that calculates a wavefront of light; 43, a display space management unit that manages a display object;
44 is a wavefront synthesizing means for synthesizing a wavefront, and 45 is a hologram surface information managing means for managing a hologram calculation matrix.

An operation example of the embodiment having the above configuration will be described.

The display space management means 41 manages various attributes of the object such as position information of the display object. When the system such as the position of the hologram is set by the hologram surface information management means 45, first, the coordinate system and matrix corresponding to the hologram are initialized by the hologram surface information management means 45. When a viewpoint corresponding to each pixel on the hologram surface is determined, the depth buffer generation unit 41 refers to the display space management unit 43 and generates a depth buffer at the viewpoint. The wavefront calculation means 42 calculates the wavefront of light when it is assumed that a point light source is located at the position of the object registered in each element of the depth buffer. At this time,
The luminance information of the object is used as the amplitude value of the wavefront based on the information of the display space management unit 43. Wavefront synthesis means 4
In step 4, after calculating for all the elements of the depth buffer, the total sum is obtained. When the same processing is completed for all viewpoints, first, the wavefront calculation means 42 calculates the wavefront of the reference light, and the wavefront synthesis means 44 executes a synthesis operation of the reference light and the object light.

According to the above-described control mode, it is not necessary to decompose the object as a group of point light sources, and the resolution is coarser for a farther object.
It can be calculated efficiently. Here, the resolution of an object at a longer distance becomes coarser, as shown in FIG.
This is because the elements (u, v) of the depth buffer correspond to the bottom surface of the quadrangular pyramid whose vertex is at the viewpoint 24, and the farther the distance, the larger the bottom surface (rougher the resolution).

Since the processing in each depth buffer is independent, parallelization is possible. By performing the calculation of the wavefront from each viewpoint in parallel with the hardware processing for preparing the depth buffer, high-speed processing is possible. Thus, a computer generated hologram can be generated, and a moving image hologram can be realized.

[0030]

As described above, according to the present invention, it is possible to reduce the amount of calculation and to display only an object that can be viewed from a specific viewpoint by excluding a shielded object from calculation objects. .

Further, the processing in the present invention can be parallelized, and the calculation of the wavefront at each viewpoint is performed in parallel with the hardware processing for preparing the depth buffer, so that the computer generated hologram can be generated at high speed. And a moving image hologram can be realized.

The object to be displayed does not need to be described by a point light source, and a model generated by polygons can be used. Conventional CG data can be easily converted into a hologram.

[Brief description of the drawings]

FIG. 1 is a flow chart illustrating an exemplary embodiment of a method according to the present invention.

FIG. 2 is a diagram showing a system for explaining the embodiment.

FIGS. 3A and 3B are diagrams for explaining a registration method for a depth buffer in the embodiment. FIG.

FIG. 4 is a block diagram showing an embodiment of the apparatus of the present invention.

[Explanation of symbols]

21 Hologram Surface 22 View Volume 23 Depth Buffer 24 Viewpoint 25 Depth Buffer-View Volume Corresponding to Element 31 Corresponding Example of Target Object and Depth Buffer in View Volume 32 Example of Each Element Value of Depth Buffer 41 depth buffer generating means 42 wavefront calculating means 43 display space managing means 44 wavefront synthesizing means 45 hologram surface information managing means

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Satoshi Suzuki 3-19-2 Nishi Shinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation

Claims (3)

[Claims] 1. A computer generated hologram generating method for calculating interference fringes between light from an object and reference light, the method comprising: generating a depth buffer from each pixel of a hologram surface as a viewpoint; and registering a depth buffer registered in the depth buffer. A process of calculating the sum of the wavefronts on the hologram surface when there is a point light source at the position of the object; and combining the wavefront of the reference light with the obtained value of the sum of the wavefronts from the object. A method for generating a computer generated hologram using a depth buffer, comprising: generating an interference fringe; 2. A process for obtaining a sum of wavefronts on a hologram surface when a point light source is located at a position of an object registered in the depth buffer, includes: 2. The computer generated hologram generating method using a depth buffer according to claim 1, wherein after calculating a wavefront at each viewpoint on the hologram surface, a sum of the wavefronts is calculated. 3. A computer generated hologram generating apparatus for obtaining an interference fringe between light from an object and reference light by a computer, comprising: means for managing a display object; and each of a hologram surface with reference to the managed display object. Means for generating and managing a depth buffer from the viewpoint of pixels, hologram managing means for managing a hologram calculation matrix, and a point light source at a position of an object registered in the depth buffer using the managed matrix. Means for calculating the wavefront on the hologram surface and the sum of the wavefronts, and the wavefront of the reference light, and means for combining the calculated sum of the wavefronts and the wavefront of the reference light. A computer generated hologram generator using a depth buffer.