JP2002215008A - Compute hologram data generating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of times of positioning in a forming device (computer hologram forming device) and to reduce the error and noise which are generated in the reproduced image of a finally prepared CGH(Computer Generated Hologram) by realizing prediction of the reproduced image before forming the finally prepared CGH. SOLUTION: With respect to a plurality of inputted visual field images, an elementary region image forming means 1, a CGH data generating means 2, a reproduced image synthesizing means 3 and a correction means 4 correct the error of each of a plurality of elementary region images within the visual field images to generate a plurality of new visual field images, and a plurality of elementary region images is again generated by using these new visual field images. After performing the process a desired number of times, a CGH data coupling means 5 combines elementary region CGH data generated from each element region image at the prescribed position, and generates combined CGH data. A means 6 for preparing data for the forming devices converts the combined CGH data into data for the forming devices.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hologram (CGH: Computer Generat) generated by a visual computer.
The present invention relates to a computer generated hologram data generating method for generating an ed hologram.

[0002]

2. Description of the Related Art A holographic stereogram technique for reproducing different images, such as a stereoscopic image and a moving image, depending on the viewing angle with parallel light, was devised in 1975 by Cross of America Multiplex. A series of photographs having different gaze directions can be obtained by photographing a state in which the object rotates on the turntable with a fixed camera or photographing the object by fixing the object and moving the camera in parallel. Using the light that reaches the hologram film through the slit as the object light and the light that reaches the hologram film directly through the slit as the reference light, the strips and dot-like element areas are lined up on the hologram film. By continuously photographing a series of photographic films while moving the hologram film, images having parallax are sequentially recorded as holograms.

[0003] Computer generated hologram (hereinafter referred to as CGH) using Fourier transform
The method of generating data is introduced in Taniguchi and Yoshikawa, "Computer Synthesized Rainbow Hologram", 3D Image Conference, 7-3 (1996), etc. It is created by extracting an image as a minute element region in the depth direction, generating CGH data for each element region, and combining those CGH data.

FIG. 9 is a schematic diagram for explaining a holographic stereogram based on CGH. Each pixel of the plurality of original images is assigned to a diffraction order, and CGH data having each region for each pixel is generated. A reconstructed image is obtained by looking at a set of diffracted light from each of these regions,
When the reproduced images are output at different orders (diffraction angles), the picture appears to change depending on the light source, the CGH data, and the position of the viewpoint.

[0005]

However, in the conventional computer generated hologram data generation method, a part of a plurality of two-dimensional images is extracted and CGH data is generated for each element region, so that a reproduced image of the CGH data is simulated. However, only a reproduced image of each element region can be obtained, and a reproduced image of the entire original two-dimensional image cannot be obtained. As a result, a reproduced image of CGH data created by performing positioning or the like in the computer hologram forming apparatus may not be able to be predicted. In addition, CG from a plurality of two-dimensional images
When H data is generated, the reproduced image is
An error may occur with a two-dimensional image.

The main reason that the reproduced image of the computer generated hologram does not match the original two-dimensional image and causes an error is that the numerical calculation operation for generating CGH data from the original two-dimensional image is not necessarily a reversible process. This is because it contains uncertain elements. The irreversibility and uncertainty described above depend on the characteristics of the hologram in principle. In other words, the reproduced image obtained from the hologram expresses light as intensity, that is, amplitude information, whereas the hologram itself records the phase information of light, so that a minute image generated when creating hologram data is generated. This is because deviations in numerical values, rounding errors, and the like may cause a large change in a reproduced image.

Therefore, conventionally, in order to reduce an error occurring in a reproduced image, a hologram is actually produced on the basis of the created CGH data, a diffraction image is reproduced by the prototype hologram, and a difference from an original image is examined. Inevitably, a cut-and-try method must be used to correct the original image in accordance with the obtained difference information to reduce errors.

An object of the present invention is to make it possible to predict a reproduced image before forming a CGH to be finally formed, and to reduce the number of times of alignment in a computer generated hologram forming apparatus. It is another object of the present invention to reduce errors and noise generated in a CGH reproduction image that is finally created.

[0009]

In order to solve the above-mentioned problems, the present invention obtains an element area reproduced image from CGH data for each element area and reproduces (simulates) a plurality of original two-dimensional images. , Information for correcting the calculated CGH data is obtained.

That is, according to the present invention, a plurality of diffracted lights are generated by irradiating light to the entire hologram recorded on the medium with element region holograms corresponding to pixels constituting each of the plurality of recorded images. A computer generated hologram data generating method for generating computer generated hologram data in each of the element region holograms of the entire hologram for reproducing one of the plurality of recorded images in accordance with a viewing angle, Image calculation for calculating, for each area hologram, an element area image that is a diffraction image to be reproduced by the element area hologram, using original image data of the plurality of recorded images and diffraction angle information of the plurality of diffracted lights. Step and necessary to reproduce the calculated element region image as a diffraction image, respectively, in the element region hologram The computer generated hologram data, a hologram data calculation step of calculating for each of the element region holograms, and using the calculated computer generated hologram data, a simulating step of simulating the element region images; and Synthesizing each of the element area images for all of the element area holograms to obtain simulated image data of the plurality of recorded images; simulated image data of the plurality of recorded images; A computer generated hologram data generating method is provided, comprising: comparing the original image data of a plurality of recorded images with each of the recorded images to obtain difference information.

Further, according to the present invention, based on the difference information obtained in the comparing step, original image data of the plurality of recorded images is corrected to calculate corrected image data of the plurality of recorded images. Calculating the corrected element area image for each of the element area holograms based on the calculated corrected image data of the plurality of recorded images and the diffraction angle information; and A step of calculating, for each of the element region holograms, computer hologram data corrected in the element region hologram, which is necessary to reproduce an image as a diffraction image, is a preferred embodiment of the present invention.

It is a preferable aspect of the present invention to add a step of combining the calculated computer generated hologram data or the corrected computer generated hologram data with respect to a plurality of element region holograms. .

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS <First Embodiment> A computer generated hologram data generating method according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an example of a computer generated hologram data generation apparatus for realizing the computer hologram data generation method according to the first embodiment of the present invention. The computer generated hologram data generation apparatus 100 for realizing the computer generated hologram data generation method according to the present invention includes an element area image generation unit 1, a CGH data generation unit 2, a reproduced image synthesis unit 3, a correction unit 4, a CGH data combination unit 5, It has data forming means 6 for a forming apparatus (computer hologram forming apparatus). Each of the above means can be controlled by the same control means (CPU), and can be controlled by independent control means.

The element region image generating means 1 is a means for generating an element region image from a plurality of parallax images, which are two-dimensional images, and diffraction angle information corresponding to the parallax images. CGH
The data generation means 2 converts the element area CG from the element area image.
This is means for generating H data and an element area reproduced image. The reconstructed image synthesizing means 3 is a means for generating a reconstructed image corresponding to a parallax image from the element region reproduced image and the diffraction angle information.
The correction unit 4 is a unit that compares the reproduced image and the parallax image, measures an error between the two, and generates a new parallax image in which the error is corrected. The CGH data combining unit 5 combines a plurality of element area CGH data to generate combined CGH data. Forming apparatus data creating means 6 converts the combined CGH data into forming apparatus data.

Next, the processing of data by the above means and the flow of the processed data will be described. FIG. 2 is a flowchart showing a first embodiment of the computer generated hologram data generating method of the present invention. First, in step S1, a flag F = 1 is set as an initial setting. In step S2, a plurality of parallax images and diffraction angle information are input to the element area image generation unit 1. This is, for example, read from a memory (not shown) or input from another external device. In step S3, the element region image generating means 1 generates an element region image based on a plurality of two-dimensional parallax images and diffraction angle information corresponding to the parallax images. Note that, as a plurality of two-dimensional images, for example, images of the same size of 256 gradation gray scales which are different depending on the viewing angle (diffraction angle) are prepared.

For example, when creating a CGH for reproducing four images of different orders, the amount of light reproduced is four minutes when reproducing only one bright point and when reproducing all four bright points. It becomes 1. Therefore, when allocating an image to a diffraction order position, a point (reference point) serving as a reference light is prepared in order to equalize the light amount at the time of reproduction, and the diffracted light is calculated based on the relative light amount as compared with the reference point. Is calculated. The number of images is n, the amount of the image from 0 1 (1 brightest, 0 darkest) normalized normalized to real quantity v _i
Expressed in (i = natural number from 1 to n), the light quantity d _i when allocating the diffraction order (i = natural number from 1 to n) can be determined by the following equations 1 and 2.

[0017]

(Equation 1)

[0018]

(Equation 2)

FIG. 5 is a diagram showing an example of a parallax image.
A plurality of two-dimensional images having different viewing angles for one object are prepared as parallax images. FIG. 6 is a schematic diagram showing the correspondence between a plurality of parallax images and element region images.
The parallax image is decomposed for each pixel, and each pixel of the parallax image has a diffraction angle (± 1 in the example of FIG.
A parallax image having a rotation angle of 4.7 ° is assigned to the ± 10th diffraction order, and a parallax image having a rotation angle of ± 4.4 ° is assigned to the ± 3rd diffraction order. For example, if the size of the two-dimensional parallax image is w pixels in width and h pixels in height, it is assigned to diffraction angles of w × h pixels, and an element region image of w × h pixels is created.

In step S4, the CGH data generating means 2 generates element area CGH data from the element area image generated by the element area image generating means 1, and reproduces (simulates) an element area reproduced image. Step S5
In FIG. 1, the element area CGH data is stored in a memory or the like (FIG. 1).
(Not shown). It should be noted that the element area images exist for the number of pixels, and it is necessary to generate the element area CGH data of all the element area images and reproduce (simulate) the element area reproduced images.

FIG. 7 is a diagram showing element area CGH data generated from an element area image. The generated element area CGH data has the arrangement information of the diffracted light corresponding to the diffraction angle of the desired diffraction grating, and corresponds to the interference pattern shown in the element area CGH data of FIG. It is generated by calculating the phase distribution using Fourier transform / inverse transform. The method of generating the element area CGH data is introduced in, for example, “Recent Trends in Computer Holograms”, Oplus E, November 1996.

In step S6, it is determined whether or not the flag F = N. N is the number of times the light amount error is corrected, and can be set to an arbitrary value. If the result of determination in step S6 is that flag F ≠ N (that is, flag F <N), then in step S7, 1 is added to the value of flag F, and flag F = F +
Let it be 1. In step S8, the reproduced image synthesizing unit 3 synthesizes the element area reproduced images for all the pixels generated by the CGH data generating unit 2 based on the diffraction angle information, and reproduces the image corresponding to the parallax image. Generate an image.

An element area image and an element area CGH shown in FIG.
As can be seen from the correspondence with the data, even if a reproduced image is simulated from the element area CGH data using the Fourier transform, only a few pixels of light spots can be obtained, and a reproduced image similar to the original image cannot be obtained. Can not. In order to obtain a reproduced image by calculation, it is necessary to calculate a reproduced image using Fourier transform for all the element area CGH data corresponding to each pixel, collect light spots of diffraction orders, and reconstruct the reproduced image. There is. Also,
Since the light quantity at the light spot is given as a spectral ratio, it is necessary to calculate the light quantity of the reconstructed reproduced image from the light quantity at the light spot.

Let n be the number of images and normalized light quantity d ′ _i (i = 1 to n) obtained by normalizing the light quantity of the light spot of the diffraction order to a real number from 0 to 1 (1 is the brightest and 0 is the darkest). When the light amount of the light spot of the reference light is represented by d ′ ₀ , the light amount v ′ _i (a natural number of i = 1 to n) when viewed as a reproduced image is
It can be obtained by the following equations (3) and (4).

[0025]

(Equation 3)

[0026]

(Equation 4)

Subsequently, in step S9, the correcting means 4 compares the reproduced image generated by the reproduced image synthesizing means 3 with the first input parallax image to measure an error, and in step S10, calculates the error. Generate a new corrected parallax image. The new parallax image generated by the correction unit calculates the difference between each pixel between the original two-dimensional image (parallax image) and the reproduction image simulation result of the CGH data, adds the difference to the original image, and sets the light amount of each pixel to 0 to 255. Is normalized. Then, the new parallax image is set as the parallax image input in step S1, and the process returns to step S1 again. When the stereoscopic hologram is created, the distribution of the light amount generated between the original image and the simulation result of the reproduced image is large. The gap can be corrected.

By repeating the above process, if all the values of the flag F for each of the plurality of element areas are determined to be F = N in step S6, the CGH data combining means 5 determines in step S11. , CG
The plurality of element area CGH data generated by the H data generating means 2 and stored in the memory are combined to form a combined CGH.
Generate data. By combining a plurality of element area CGH data at predetermined positions in the horizontal or vertical direction, a method of scanning the drawing direction in the horizontal or vertical direction can be used in the forming apparatus (computer hologram forming apparatus), The number of times of alignment can be reduced.

FIG. 8 is a schematic diagram for explaining the combination of element area CGH data in the horizontal direction. As shown in FIG. 8, when a plurality of element area CGH data are combined in the horizontal direction in step S11, horizontally long data is created. This eliminates the necessity of performing a horizontal alignment process between element regions in the forming apparatus, and makes it possible to perform a positional adjustment only by a vertical alignment. Although FIG. 8 shows only the case where the connection is performed in the horizontal direction, the connection is also performed in the vertical direction in the same manner as in the horizontal direction, and vertically long connection data is created. It is not necessary to perform a direction alignment process.

In step S12, the forming apparatus data creating means 6 converts the combined CGH data into forming apparatus data. The forming apparatus data is data that can be read by a forming apparatus (not shown) that performs fine processing and printing, such as a laser processing machine, an etching apparatus, and an imagesetter. The forming apparatus records a hologram on an arbitrary object by using the forming apparatus data, and performs step S1.
Regarding the data obtained by converting the combined data of the element area CGH data combined in step 1 to be usable in step S12, a desired stereoscopic image is obtained by referring to the reproduced stereoscopic image.

As described above, in the first embodiment, with respect to the input visual field image, the element region image generating means 1,
The CGH data generating unit 2, the reproduced image synthesizing unit 3, and the correcting unit 4 correct each error of the plurality of element regions by a predetermined number of times, and then combine the respective element regions by the CGH data combining unit 5, and The data creating means 6 converts the combined CGH data into forming apparatus data.

<Second Embodiment> FIG. 3 is a block diagram showing an example of a computer generated hologram data generating apparatus for realizing a computer generated hologram data generating method according to a second embodiment of the present invention. A computer generated hologram data generation apparatus 100 for realizing the computer generated hologram data generation method of the present invention further includes an error determination unit 7 in addition to the first embodiment shown in FIG. Error determination means 7
Calculates a difference between the original parallax image or the new parallax image generated by the correcting unit 4 and the reproduced image output by the reproduced image synthesizing unit 3, and calculates an error of the calculated error. Is a means for determining whether the value is larger or smaller. As in the first embodiment, each unit can be controlled by the same control unit (CPU), or can be controlled by independent control units.

Next, the processing of data by the above means and the flow of the processed data will be described. FIG. 4 is a flowchart showing a second embodiment according to the computer generated hologram data generating method of the present invention. In the following description, a detailed description of steps for performing the same operation as in the first embodiment will be omitted. Step S2
In 1 (corresponding to step S2 of the first embodiment), a plurality of parallax images and diffraction angle information are input to the element region image generating means 1. In step S22 (corresponding to step S3 of the first embodiment), the element region image generation unit 1 performs a process on the basis of a plurality of two-dimensional parallax images and diffraction angle information corresponding to the parallax images. Generate an element area image.

In step S23 (corresponding to step S4 in the first embodiment), the CGH data generating means 2
Generates element area CGH data from the element area image generated by the element area image generation means 1 and reproduces (simulates) an element area reproduced image. In step S24 (corresponding to step S5 in the first embodiment), the element area CGH data is stored in storage means (not shown in FIG. 3) such as a memory. Note that, as in the first embodiment, the element area images exist for the number of pixels, and it is necessary to generate the element area CGH data of all the element area images and reproduce (simulate) the element area reproduced images. There is. In step S25 (corresponding to step S8 in the first embodiment), the reproduced image synthesizing unit 3 sets the C
A reproduced image corresponding to a parallax image is generated by synthesizing element region reproduced images for all pixels generated by the GH data generating means 2.

In step S26 (corresponding to step S9 in the first embodiment), the error judging means 7 compares the parallax image as an original image with the reproduced image output by the reproduced image synthesizing means 3 and compares them. The error is calculated, and step S27
In, it is determined whether the error is smaller than a desired error. That is, for example, whether the magnitude of the error between the new parallax image input to the elemental area image generating means 1 immediately before that and the reproduced image output by the reproduced image synthesizing means 3 falls within a desired error range. By determining
A method of measuring the convergence of an error is possible. In FIG. 4, “calculated error <desired error”, but “calculated error ≦ desired error” is also possible. Also, an arbitrary value can be set as the desired error, and a storage means such as a memory (FIG.
(Not shown).

If the calculated error is larger than the desired error, the correcting means 4 returns to step S28 (corresponding to step S10 of the first embodiment).
A new parallax image in which the error measured in step 26 is corrected is generated, and the process returns to step S21 again as in the first embodiment.

On the other hand, if the calculated error is smaller than the desired error, in step S29 (corresponding to step S11 in the first embodiment), the CGH data combining means 5 A plurality of element area CGH data generated and stored in the memory are combined to generate combined CGH data, and in step S30 (corresponding to step S12 in the first embodiment), a forming apparatus (computer hologram forming apparatus) Data creation means 6
The combined CGH data is converted into data for a forming apparatus (computer hologram forming apparatus).

As described above, in the second embodiment, the element area generating means 1 and the CG
H data generation means 2, reproduced image synthesis means 3, correction means 4,
After correcting each error of the plurality of element areas to within a predetermined error range by the error determination means 7, the CGH data combining means 5 combines the element areas, and the forming apparatus data creating means 6 creates the combined CGH data. Is converted into data for a forming apparatus.

In the first and second embodiments, images having parallax in the left and right directions are prepared and arranged in the diffraction order in the left and right direction. However, images in the vertical direction are also prepared and the images are prepared in the upper and lower diffraction orders. By arranging, it is possible to create a CGH that has a three-dimensional effect also in the upper and lower directions. Also, instead of a parallax image, 2
By arranging completely different images in the left and right diffraction orders, CGHs with different images seen on the right and left sides can be created, or moving images can be prepared and sequentially arranged in the left, right, upper and lower diffraction orders, and the CGH can be obtained. Play a movie by moving it left or right or up and down C
It is also possible to create GH or the like.

It is also possible to create a program including an instruction for executing each step described in the first and second embodiments, and to execute this program by a computer. That is, the present invention also relates to a recording medium on which a program for implementing the computer generated hologram data generation method of the present invention is recorded.

[0041]

As described above, according to the present invention,
Since the reproduced image of the element area CGH data is calculated and combined to simulate the reproduced image, the CG finally created
A reproduced image is predicted before H is formed, and the number of times of alignment in the forming apparatus can be reduced. In addition, by correcting the parallax image based on the result of the simulation, it is possible to reduce errors and noises that occur in a CGH reproduction image that is finally created. In the correction of the parallax image, it is possible to perform the correction a desired number of times or to perform the correction until the parallax image falls within a desired error range. Further, by combining the element area CGH data in the horizontal direction or the vertical direction, a method of scanning the drawing direction in the horizontal direction or the vertical direction in the forming apparatus can be used.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a computer generated hologram data generation device for implementing a first embodiment of a computer generated hologram data generation method according to the present invention.

FIG. 2 is a flowchart showing a first embodiment of the computer generated hologram data generation method of the present invention.

FIG. 3 is a block diagram showing an example of a computer generated hologram data generation device for realizing a computer hologram data generation method according to a second embodiment of the present invention.

FIG. 4 is a flowchart showing a second embodiment according to the computer generated hologram data generating method of the present invention.

FIG. 5 is a diagram illustrating an example of a parallax image.

FIG. 6 is a schematic diagram showing correspondence between a plurality of parallax images and element region images.

FIG. 7 is a diagram showing element area CGH data generated from an element area image.

FIG. 8 is a schematic diagram for explaining horizontal combination of element area CGH data.

FIG. 9 is a schematic diagram for explaining a holographic stereogram by CGH.

[Explanation of symbols]

Reference Signs List 1 element area image generating means 2 CGH data generating means 3 reproduced image synthesizing means 4 correcting means 5 CGH data combining means 6 data generating means for forming apparatus (computer hologram forming apparatus) 7 error determining means

Claims (3)

[Claims] 1. A viewing angle by irradiating an entire hologram recorded on a medium with an element area hologram corresponding to each pixel constituting each of a plurality of recorded images to generate a plurality of diffracted lights, A computer generated hologram data generating method of generating computer generated hologram data in each of the element region holograms of the entire hologram for reproducing one of the plurality of recorded images according to the following: An element region image that is a diffraction image to be reproduced by the element region hologram, an image calculation step of calculating using the original image data of the plurality of recorded images and the diffraction angle information of the plurality of diffracted lights; The computer generated hologram data in the element region hologram necessary for reproducing each of the element region images as diffraction images. A hologram data calculating step of calculating for each of the element region holograms; a simulating step of simulating each of the element region images using the calculated computer generated hologram data; and a simulating of each of the simulated element regions. Synthesizing an image for all the element region holograms to obtain simulated image data of the plurality of recorded images; simulated image data of the plurality of recorded images; and the plurality of recorded images A comparison step of comparing the original image data with each other for each recorded image to obtain difference information. 2. correcting the original image data of the plurality of recorded images based on the difference information obtained in the comparing step to calculate corrected image data of the plurality of recorded images; Calculating a corrected element region image for each of the element region holograms based on the corrected image data of the plurality of recorded images and the diffraction angle information, and using the corrected element region image as a diffraction image Calculating the corrected computer generated hologram data in the element area hologram required for reproduction for each of the element area holograms. 3. The computer generated hologram data according to claim 1, further comprising a step of combining the calculated computer generated hologram data or the corrected computer generated hologram data for a plurality of the element region holograms. Generation method.