JP2007279221A - Hologram data creating device, hologram data creating method and hologram data creating program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hologram data creating device, a hologram data creating method and a hologram data creating program for rapidly and accurately creating hologram data so as to display a large quantity of holograms with less degradation of images by a holocorder hologram. <P>SOLUTION: The hologram data creating device 1 is equipped with: a multiplying means 4 which multiplies a phase shift amount according to a phase shift function corresponding to a lens having a principal point at an intersection on an optical axis between an element image disposed on a front focal plane and a lens constituting a lens group opposing and corresponding to the element image, and the luminance data of each pixel in the element image, and then obtains an intensity distribution of the light field after the phase shift having the calculated products as elements; a Fourier transforming means 5 which Fourier transforms the calculated product to obtain an intensity distribution of the light field on a hologram creating plane by each element image; an adding means 6 which calculates the superposed sum of the intensity distributions of the object light fields by the element image to obtain an intensity distribution of the light field on the hologram creating plane; and a hologram data creating means 7 which creates luminance data as hologram data by each pixel to display an image corresponding to interference fringes appearing as the intensity distribution of the light field. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hologram data creation device, a hologram data creation method, a hologram data creation program, and a hologram for creating hologram data for reproducing a three-dimensional image (stereoscopic image) as a hologram so as to be visible on a display of a two-dimensional display screen. The present invention relates to a display system.

  In general, as one technique for displaying an object such as a subject on a display of a two-dimensional display screen as a three-dimensional image (stereoscopic image) so as to be visible, a holographic hologram that creates a hologram from a plurality of element images of the object (For example, see Non-Patent Document 1) is known. This holcoder hologram is used to optically create a hologram from a plurality of element images photographed using the technique of integral photography (see, for example, Non-Patent Document 2).

R.V.Pole, “3-D imagery and holograms of objects illuminated in white light”, Appl. Phys. Lett. Vol. 10, pp. 20-22 (1967) M.G.Lippmann, Comptes-Rendus, 146, pp.446-451 (1908)

  Conventionally, in a holcoder / hologram, coherent light is applied to a multi-viewpoint element image of a subject (object) imaged through a convex lens array, and an image equivalent to the subject is obtained through a convex lens array having the same focal length and arrangement as at the time of imaging. The hologram of the subject imaged under natural light is created by forming interference fringes between the light (object light) constituting the reproduced image and the coherent light as the reference light.

  In the holocorder / hologram as described above, it is necessary to install and adjust the optical system such as the convex lens array and the illumination system for the reference light with high accuracy. Not suitable for cost. Therefore, there is a demand for a technique that can reduce the labor required for installing and adjusting the optical system and the illumination system. Under such circumstances, as is called a computer-generated hologram or a digital hologram, a technique for calculating the propagation of light by using a computer and recording and reproducing the hologram has been developed. However, in order to calculate the propagation of light, the number of data handled is large, and thus a technique for creating hologram data quickly and accurately has not been established.

  Accordingly, the present invention has been made to solve the above-described problems, and generates hologram data quickly and accurately in order to display a large amount of holograms with little image degradation by a holoccoder hologram. An object of the present invention is to provide a hologram data creation device, a hologram data creation method, a hologram data creation program, and a hologram display device.

  The present invention was devised to achieve the above object. First, the hologram data creating apparatus according to claim 1 is an object radiated from each of a plurality of element images representing an object from multiple viewpoints. In order to create hologram data that causes light to enter the lens group and display on the display an image corresponding to the interference fringe between the intensity distribution of the light field generated by superimposing the light emitted from the lens group and the reference light, An element image storage unit, a phase shift setting unit, a multiplication unit, a Fourier transform unit, an addition unit, and a hologram data creation unit are provided.

  In such a configuration, the hologram data creating device uses the phase shift setting means to calculate the intersection point on the optical axis between the element image arranged on the front focal plane and the lens constituting the paired lens group facing this element image. A phase shift amount corresponding to the phase shift function corresponding to the lens as the main point is set in advance.

  Then, the hologram data creation device multiplies the luminance data for each pixel included in the element image by the multiplication means by the phase shift amount set by the phase shift setting means, and uses the product calculated as a result as the element. The intensity distribution of the light field after the phase shift is obtained, and the product calculated by the multiplication means is Fourier transformed by the Fourier transform means to calculate the intensity distribution of the light field on the hologram creation surface for each element image.

  Since the luminance data represents the brightness when displaying the pixels of the element image, the pixels can be formed depending on the degree of brightness in the case of display with monochromatic light. That is, the luminance data size distribution represents the intensity distribution of the light field.

  Next, the hologram data creation device calculates the sum of the superpositions of the intensity distributions of the light fields of the object light for each element image calculated by the Fourier transform means by the adding means, and calculates the light field on the hologram creation surface. The intensity distribution of the light field obtained by superimposing the intensity distribution of the light field calculated by the adding means and the intensity distribution of the light field of the reference light is calculated by the hologram data creating means, and the superimposed light is obtained. Luminance data for each pixel for displaying an image corresponding to interference fringes appearing as a field intensity distribution is created as hologram data.

  Further, the hologram data creating device according to claim 2 is an intersection point according to claim 1, wherein the optical axis of the lens constituting the pair of lens groups facing the element image passes through the element image by the phase shift setting means. The phase shift amount calculated by the phase shift function of the convex lens whose principal point is or a concave lens having the same absolute value as the focal length of the convex lens is set. Therefore, the calculation according to the phase shift function represents the state of light passing through the convex lens or the concave lens.

According to a third aspect of the present invention, there is provided the hologram data creating apparatus according to the first or second aspect, wherein a fast Fourier transform (FFT (Fast Fourier Transform)) process is executed by the Fourier transform means. By the way, when the number of calculation points is N, the calculation amount of the discrete Fourier transform (DFT (Distance Fourier Transform)) is N ² order, whereas the calculation amount of the fast Fourier transform is N * log ₂ N order. Therefore, as the number N of calculation points increases, the degree of reduction in the calculation amount tends to increase. Therefore, the hologram data creation apparatus creates the hologram data quickly and accurately in the creation process of the hologram data having a large amount of data by executing the fast Fourier transform by the Fourier transform means.

  According to a fourth aspect of the present invention, there is provided a hologram data creation method in which light emitted from each of a plurality of element images representing an object from multiple viewpoints is incident on a lens group, and the object light emitted from the lens group is superimposed. In order to create hologram data for displaying on the display an image corresponding to an interference fringe between the intensity distribution of the light field generated by the combination and the reference light, a multiplication step, a Fourier transform step, an addition step, a hologram data creation step, The procedure included.

  In such a procedure, the hologram data creation method is configured by the multiplication means to configure the luminance data for each pixel included in the element image, the element image arranged on the front focal plane, and a pair of lenses facing this element image. Multiply by the phase shift function corresponding to the phase shift function corresponding to the lens whose main point is the intersection on the optical axis with the lens to be used, and the intensity of the optical field after the phase shift using the calculated product as an element The distribution is obtained, and the product calculated in the multiplication step is Fourier-transformed by the Fourier transform means to calculate the intensity distribution of the light field on the hologram creation surface for each element image.

  Then, the hologram data creation method calculates the sum of the superposition of the intensity distributions of the light field of the object light for each element image calculated in the Fourier transform step in the addition step, and calculates the intensity of the light field on the hologram creation surface. And calculating the intensity distribution of the light field obtained by superimposing the intensity distribution of the light field calculated in the adding step and the intensity distribution of the light field of the reference light in the hologram data creation step, and the superimposed light field Luminance data for each pixel for displaying on the display an image corresponding to the interference fringes appearing as the intensity distribution is generated as hologram data.

  The hologram data creation program according to claim 5 makes light emitted from each of a plurality of element images representing an object from multiple viewpoints incident on a lens group, and superimposes object light emitted from the lens group. In order to create hologram data for displaying on the display an image corresponding to the interference fringe between the intensity distribution of the light field generated by the combination and the reference light, the computer is used as multiplication means, Fourier transform means, addition means, hologram data creation means The configuration is to function.

  In such a configuration, the hologram data creation program uses the multiplication means to calculate the luminance data for each pixel included in the element image, the element image arranged on the front focal plane, and the lens group that is paired facing the element image. Multiply by the phase shift amount corresponding to the phase shift function corresponding to the lens whose principal point is the intersection on the optical axis with the constituting lens, and the light field after the phase shift with the calculated product as an element The intensity distribution is obtained, and the product calculated by the multiplying means is Fourier transformed by the Fourier transform means to calculate the intensity distribution of the light field on the hologram creation surface for each element image.

  Then, the hologram data creation program calculates the sum of the superposition of the intensity distributions of the light fields for each element image calculated by the Fourier transform means by the adding means to obtain the intensity distribution of the light field on the hologram creation surface, The hologram data creation means calculates the intensity distribution of the light field obtained by superimposing the intensity distribution of the light field calculated by the adding means and the intensity distribution of the light field of the reference light, and the intensity distribution of the superimposed light field The luminance data for each pixel for displaying an image corresponding to the interference fringes appearing on the display is created as hologram data.

The present invention has the following excellent effects.
According to the first, fourth, or fifth aspect of the invention, there is an effect that the hologram data for displaying a large amount of holograms with little image deterioration can be quickly and accurately produced by the holocorder hologram. . In addition, an optical lens array such as a fly-eye lens or a lenticular lens is not required, the number of parts is reduced, and manufacturing / adjustment work as an optical device is also unnecessary. For this reason, the number of components is reduced and the optical system manufacturing / adjustment work is simplified, which is useful for reducing the manufacturing cost.

  According to the second aspect of the present invention, the phase shift of the intensity distribution of the light field corresponding to the transmission of the optical system of the convex lens or the concave lens can be calculated according to the phase shift function.

  According to the third aspect of the invention, since the fast Fourier transform is performed, the Fourier transform can be efficiently performed as the number of samplings increases, and hologram data having a large amount of data can be efficiently created. .

  The best mode for carrying out the present invention will be described below with reference to the drawings. The present invention relates to a hologram data creation device, a hologram data creation method, a hologram data creation program, and a hologram display device. Here, the configuration and operation of the hologram data creation device will be mainly described.

  FIG. 1 is a block diagram illustrating a configuration of a hologram data creation apparatus according to an embodiment. This hologram data creation device 1 makes an object light emitted from each of a plurality of element images representing an object from multiple viewpoints incident on a lens group, and an optical field generated by superimposing the object lights emitted from the lens group Element image storage means 2, phase shift setting means 3, multiplication means 4, and Fourier transform means 5 in order to create hologram data for displaying on the display an image corresponding to the interference fringes between the intensity distribution of the light and the reference light. And an addition means 6, a hologram data creation means 7, and a hologram data storage means 8.

  The element image storage means 2 is luminance data for each pixel included in an element image for forming an intensity distribution of a light field corresponding to radiated light emitted from an element image representing an object from multiple viewpoints according to integral photography. Is memorized. The stored luminance data is output to the multiplication means 4. The element image storage unit 2 acquires luminance data from the imaging device 9 that captures an object.

Here, an image forming surface is taken on the x ₀ -y ₀ plane of the x ₀ axis and the y ₀ axis, and the object light emitted from the element image i formed on the image forming surface is reflected on the x ₀ -y ₀ plane. The complex amplitude distribution of the emitted light from the element image i when traveling in the orthogonal z-axis direction is represented by O (x ₀ , y ₀ ).

  The element image storage means 2 stores a plurality of luminance data for each pixel constituting the element image i for each frame. Here, each frame means to the extent that they are associated with each other, and the stored areas do not necessarily have to be the same.

  Further, the element image i is not limited to a multi-viewpoint image obtained by actual photography of an object by integral photography, but may be a CG (Computer Graphic) or a multi-viewpoint image of a handwritten object. In the case of actual shooting, a CCD (Charge-Coupled Device) image sensor is placed on the focal plane of a convex lens array such as an eyelet lens or a lenticular lens, and the object of the subject is photographed. That is, the multi-viewpoint element image i is photographed using the parallax of the pitch interval of each convex lens of the convex lens array. Here, the recording principle of the element image i will be described.

FIG. 2 is a schematic diagram illustrating the principle of element image recording by the integral photography technique. In this schematic diagram, a lens group L in which a plurality of convex lenses L ₁ ... Are arranged on the same plane, and a rear focal plane (right side in FIG. 2) of each convex lens L ₁ of the lens group L. An element image group recording surface R formed in parallel to the plane is arranged. Furthermore, the subject (object) X is disposed on the front side (left side in FIG. 2) of the convex lenses L _1.

Here, it is assumed that all the convex lenses L ₁ have the same characteristics (focal length, aperture, etc.). On the element image group recording surface R, an inverted image O (↓) of the subject X is formed for each convex lens L ₁ . Therefore, one inverted image O (↓) of the subject X is recorded on the element image group recording surface R by the number of convex lenses L ₁ . Its inverted image O (↓) is an image viewed object X from each corresponding main point direction of the convex lens L _1, referred to as the image and the element image i. In addition, between the adjacent convex lens L _1, because of the parallax, each element image i is images of different viewpoints to be photographed, i.e., a collection of the element images i is the image of the multi-view.

  On the element image group recording surface R, a plurality of unillustrated CCDs (Charge Coupled Devices) (see the imaging device in FIG. 1) for inputting the luminance data of the pixels for each inverted image O (↓) formed are arranged. ing. Each CCD performs photoelectric conversion and stores luminance data for each pixel in a storage medium (not shown). Then, the luminance data is transmitted to the hologram data creation device 1 through various transmission paths and stored in the element image storage means 2. Further, the data may be provided to the hologram data creation apparatus 1 via a portable storage medium.

Next, the principle of optically reproducing a hologram from a plurality of element images i will be described. FIG. 3 is a schematic diagram for explaining the principle of optically reproducing a hologram from a plurality of element images. In this schematic diagram, a lens group M in which a plurality of convex lenses M ₁ having the same characteristics as the convex lens L ₁ are arranged on the same plane, and an element image group display located on the front focal plane (left side in FIG. 3) of the lens group M are displayed. A surface (element image group forming surface (image forming surface)) T and a hologram recording surface U are mainly arranged on the rear side (right side in FIG. 3).

  The luminance data of the pixels of each element image i recorded on the element image group recording surface R (see FIG. 2) is displayed on the element image group display surface T. At this time, since each element image i is recorded as an inverted image O (↓) on the element image group recording surface R, the element image i is converted to an erect image O (↑) and is displayed on the element image group display surface T. Display as.

Then, with respect to the element images display surface T, is irradiated with coherent light O _C from the opposite side to the lens group M, the light O _T passing through the element images display surface T is incident on the lens group M. The light O _M emitted from each convex lens M ₁ becomes light corresponding to the object light due to the optical characteristics of the lens group M, and as a result, the subject X is originally at the position (focal length) where the subject X exists. A reconstructed image (virtual image) X _V is formed.

Therefore, the same light as the coherent light O _C, when it is applied to the hologram recording surface U as a reference beam O _r, in the hologram recording plane U, interference fringes of the object light and the reference light, that is, the hologram is recorded. The content described above is the principle of the holocorder / hologram.

Next, returning to FIG. The phase shift setting means 3 is a phase corresponding to a lens whose principal point is the intersection on the optical axis between the element image arranged on the front focal plane and the lens constituting the paired lens group facing this element image. A phase shift amount corresponding to the shift function is set. The set phase shift amount is output to the multiplication means 4. The convex lens M _i is an optical system that transmits object light and shifts the phase.

  The multiplication unit 4 multiplies the luminance data stored in the element image storage unit 2 by the phase shift amount set by the phase shift setting unit 3, and thereby uses the product calculated as a result as a phase. The intensity distribution of the light field after the shift is obtained. The multiplication means 4 is expressed in an integrated manner with the Fourier transform means 5 in terms of algorithm.

  The Fourier transform means 5 performs Fourier transform on the product calculated by the multiplication means 4 to calculate the intensity distribution of the light field on the hologram creation surface (see FIG. 4) for each element image. Next, algorithms of the multiplying unit 4 and the Fourier transform unit 5 will be described. The multiplication unit 4 and the Fourier transform unit 5 perform an operation according to the algorithm of the following equation (1).

Here, C ₃ is a constant. O (x ₀ , y ₀ ) is light from the element image i (light field intensity distribution (complex amplitude distribution)). If f ² / (d−f) is F, exp {jk [(x ₀ + y ₀ ) / 2F]} including this focal length F is different from the actual phase shift function of the convex lens M ₁ , and the amount of calculation It is a phase shift function for the reduction of. f indicates the distance between the convex lens M ₁ and the element image forming surface T. d indicates the distance between the convex lens M ₁ and the hologram creation surface W. k is a constant.

Therefore, Equation (1) represents the Fourier transform of the product of the intensity distribution O (x ₀ , y ₀ ) of the light field and the phase shift function of the lens at the focal length F. Then, the intensity distribution h (x ₂ , y ₂ ) of the light field is calculated by this Fourier transform. That is, the multiplication unit 4 and the Fourier transform unit 5 conceptually divide the algorithm according to the equation (1) into two steps. Hereinafter, the physical meaning of the formula (1) and the calculation method thereof will be described. Here, the description will be given focusing on the element image i.

FIG. 4 is a schematic diagram illustrating an optical system in which light radiated from an element image is propagated to a hologram creation surface via a convex lens. The element image group forming surface T is divided into pixel group regions (not shown) of the element images i-1, i, i + 1. Further, the convex lenses M _i−1 , M _i , and M _{i + 1} are arranged so as to be paired with each element image i−1, i, i + 1. Further, the hologram creation surface W is arranged on the right side in FIG. 4 with convex lenses M _i−1 , M _i , and M _{i + 1} interposed between the element image forming surface T and the hologram creation surface W.

Therefore, the intensity distribution E ₃ of the light field for each of the element images i−1, i, i + 1 formed on the element image group forming surface T is incident on each convex lens M _i−1 , M _i , M _{i + 1} . The light field intensity distribution E ₃ is calculated by the light propagation calculation α.

<Light propagation calculation α>
As shown in FIG. 4, the light O (x _0, y ₀₎ emitted from the element image i, the intensity distribution of the light field to make the incident surface of the element images i and pair of convex M _i E ₃ = f _i ( x ₁ , y ₁ ) is calculated by equation (2).

Here, C ₁ is a constant. Further, the distance between the element image i and the convex lens M _i is defined as the focal length f of the convex lens M _i . The reason why the distance between the element image and the convex lens coincides with the focal length of the convex lens is that a reproduced image with relatively good image quality can be obtained in a wide range in the depth direction. Therefore, this setting is very suitable for stereoscopic display applications, and such a setting is generally used frequently. When calculating the propagation of light, an approximate expression in the Fresnel region (herein referred to as “Fresnel approximate expression”) of the Fresnel Kirchoff equation is usually used. For this reason, the Fresnel approximate expression is used in the expression (2) for the calculation in which the light from the element image i, O (x ₀ , y ₀ ) propagates the distance f to the incident surface of the convex lens M _i . .

Next, each convex lens M _i−1 , M _i , M _{i + 1} receives light of the intensity distribution E ₃ of the light field, and generates an intensity distribution E ₄ of the light field shifted in phase on the exit surface. The intensity distribution E ₄ of the light field is calculated by the phase shift calculation β of each convex lens M _i−1 , M _i , M _{i + 1} .

<Lens phase shift calculation β>
The intensity distribution E ₄ = f ₀ (x ₁ , y ₁ ) of the light field on the exit surface of the convex lens M _i is expressed by equation (3). The expression (3), a convex lens M _i optical field intensity distribution E ₃ = f _i at the incident surface of the (x _1, y _1), the product of the phase shift function of the convex lens M _i is the intensity distribution of the optical field E ₄ is shown. In Expression (3), the term (3 ′) represents the phase shift function of the convex lens M _{i with} the focal length f.

Then, the intensity distribution E ₄ of the light field propagates to the hologram creation surface W. Therefore, on the hologram creating surface W, an optical field intensity distribution E ₅ is generated by superimposing the optical field intensity distributions E ₄ . The intensity distribution E ₅ = h (x ₂ , y ₂ ) of the light field is calculated as that on the hologram creation surface W that is a distance d away from the intensity distribution E ₄ = f ₀ (x ₁ , y ₁ ) of the light field. The Similar to the calculation of the light field intensity distribution E ₃ from the element image i, the expression of the light field intensity distribution E ₄ to the light field intensity distribution E ₅ is expressed by Expression (4) using the Fresnel approximate expression. Given.

Actually, the intensity distribution E ₄ ′ of the light field generated on the hologram creating surface W by the light generated from each pixel on the intensity distribution E _{4 of the} light field is obtained, and the intensity distribution E ₄ of the light field is obtained for all the pixels. Add '. Here, a calculation region of (x ₂ , y ₂ ) on the hologram creation surface W for light generated from each pixel on the light field intensity distribution E ₄ in the calculation of Expression (4) will be described.

FIG. 5 is a schematic diagram for explaining a region on the hologram creation plane W of the intensity distribution of the light field for each pixel in the optical system shown in FIG. As shown in FIG. 5, in order aliasing components in the interference fringe does not occur, as the pixel Sf resulting intensity distribution E ₄ of the optical field, tilt reference beam O _r straight line hologram forming surface W is a traveling direction of the It may be distributed in a range D _m centering on a point intersecting with. The range D _m is expressed by Expression (5) and Expression (6).

Here, d indicates the distance between the convex lens M _i and the hologram creation surface W. θ represents the maximum value of the light divergence angle so that no aliasing component occurs in the interference fringes, and θ = λ / p. λ indicates the wavelength of light. p indicates the sampling (pixel) interval of the hologram creation surface W. Assuming that the wavelength of light λ is constant, the calculation region is expanded as the pixel interval p of the hologram creation surface W becomes smaller or the distance d between the convex lens M _i and the hologram creation surface W becomes larger from Equation (6). In FIG. 5, although the calculation area is drawn in one dimension (vertical direction), since it is actually a two-dimensional plane (including horizontal and vertical), the entire calculation area is enlarged by the square of equation (6). To do.

  By the way, when formula (2), formula (3), and formula (4) are put together, it can be seen that formula (1) is shown. That is, the algorithm according to Expression (1) has a smaller amount of calculation than an algorithm that requires three-stage calculation processing of Expression (2), Expression (3), and Expression (4). Therefore, according to the present invention, the amount of calculation can be reduced theoretically without causing deterioration of the hologram reproduction image.

  The patent applicant replaces the optical processing in the holcoder / hologram with processing by a computer in accordance with a three-stage algorithm of formula (2), formula (3), and formula (4), and calculates hologram data by calculation from a plurality of element images. Have already been filed as Japanese Patent Application Nos. 2004-315360 and 2005-133532.

  However, although the technique of Japanese Patent Application No. 2004-315360 is for speeding up the calculation, the approximation calculation is applied to the light propagation calculation, so that the degradation of the reproduced image can be avoided theoretically. could not.

  Further, in the technique of Japanese Patent Application No. 2005-133532, the calculation speed is increased without using approximation, but the position of the hologram creation surface is limited to the rear focal plane of the convex lens constituting the lens group. . In addition, since the level difference of the hologram data to be created becomes very large in the hologram, such an electric display device such as a liquid crystal panel used for hologram data display in electronic holography has such a large level difference. It was difficult to accurately display the data held.

  On the other hand, in the case of following the algorithm of the expression (1) as in this embodiment, since approximation is not used as described above, the reproduction image is not deteriorated and is limited to the rear focal plane. There is nothing. Next, returning to FIG. 1, the description will be continued.

The adding means 6 calculates the sum of the superpositions of the light field intensity distributions E ₄ (FIGS. 4 and 5) for each of the element images i (FIG. 2, etc.) calculated by the Fourier transform means 5 to obtain the hologram creation surface. The intensity distribution E ₅ of the light field for each frame in W is assumed. The calculated intensity distribution E ₅ of the light field is output to the hologram data creation means 7.

Hologram data creation means (hereinafter abbreviated as “creation means”) 7 is an intensity of the light field obtained by superimposing the intensity distribution E ₅ of the light field calculated by the addition means 6 and the intensity distribution of the light field of the reference light. The distribution is calculated, and luminance data for each pixel for displaying an image corresponding to interference fringes appearing as an intensity distribution of the superimposed light field on a display (not shown) is created as hologram data. The creating unit 7 samples the distribution calculated as the light field intensity distribution E ₅ by the adding unit 6 and determines the luminance data (luminance value) for each pixel. For example, the creating unit 7 calculates an average value of the intensity distribution E ₅ of the light field for each region corresponding to the pixel, and uses the average value as luminance data of each pixel.

  The hologram data storage means 8 stores the hologram data created by the hologram data creation means 7 for each frame. Here, “for each frame” means to the extent that they are associated with each other, and the stored areas do not necessarily have to be the same.

  Next, processing according to the algorithm of the expression (1) of the embodiment will be described with reference to FIG. 1 as appropriate. FIG. 6 is a conceptual diagram for explaining the main processing flow of the hologram data creation apparatus of the embodiment. First, the multiplication means 4 reads the luminance data of the element image i from the element image storage means 2 (S10). Then, the multiplying unit 4 reads the phase shift amount obtained from the phase shift function set from the phase shift setting unit 3 and multiplies the luminance data for each element image by the phase shift amount (S20).

At this time, the phase shift function is a function for reducing the amount of calculation, which is different from the phase shift function of the actual convex lens M ₁ , and shifts the phase of the lens at the focal length [f ² / (df)]. This is a function equivalent to Next, the Fourier transform means 5 calculates the Fourier transform of the product by the multiplication means 4 (S30). Then, the hologram data creation apparatus 1 executes S10, S20, and S30 according to the algorithm of Expression (1) for all the element images for each frame. The value calculated each time is accumulated in a memory (not shown). Then, the adding means 6 adds the Fourier transform values for all the element images (S40). Thereby, the intensity distribution E _{5 of the} light field created on the hologram creating surface W is calculated.

In the hologram data creating apparatus 1, the hologram data creating means 7 calculates the intensity distribution of the light field obtained by superimposing the light field intensity distribution E ₅ calculated by the adding means 6 and the light field intensity distribution of the reference light. Luminance data for each pixel for displaying an image corresponding to an interference fringe that is calculated and displayed as an intensity distribution of the superimposed light field on a display (not shown) is created as hologram data and stored in the hologram data storage unit 8. For example, the hologram data creating means 7 calculates an average value of the intensity distribution E ₅ of the light field for each region corresponding to the pixel, and uses the average value as luminance data of each pixel.

Here, a procedure for calculating the intensity distribution E ₅ of the light field according to the algorithms of the equations (2), (3), and (4) will be described as a comparative example. FIG. 7 is a conceptual diagram illustrating the processing flow of the comparative example. In the following description, it is assumed that a processing unit (not shown) executes each procedure. First, the processing unit reads the luminance data of the element image i from the element image storage unit (S10). The light propagation calculation α is executed to calculate the intensity distribution of the light field propagating to the distance f by the Fresnel approximation (S50).

Next, the processing unit multiplies the result of the light propagation calculation α by the phase shift function (phase shift amount) of the convex lens at the focal length f according to the phase shift calculation β of the lens (S51), and transmits the convex lens. The state of the intensity distribution of the light field is obtained. Subsequently, the processing unit calculates the intensity distribution of the light field propagating from the convex lens to the distance d by the light propagation calculation γ using the Fresnel approximate expression (S52). And a process part performs S10, S50, S51, and S52 according to the algorithm of Formula (2), Formula (3), and Formula (4) about all the element images for every frame. The value calculated each time is accumulated in a memory (not shown). Then, the adding means 6 adds the calculated values for all the element images (S40). Thereby, the intensity distribution E _{5 of the} light field created on the hologram creating surface W is calculated.

  Below, the modification of embodiment is demonstrated. Differences from the above-described embodiment will be mainly described, and common points will be omitted.

[Modification 1]
FIG. 8 is a conceptual diagram showing a first modification of the processing of FIG. In the first modification, S15 is performed between S10 and S20, and S31 is performed instead of S30. In S15, the multiplication unit 4 performs interpolation of sample points. This sample point interpolation is a process of interpolating the number of sample points of the element image i. Here, the interpolation processing is inserted before multiplying the phase shift function of the convex lens (S20), but it may be after multiplying the phase shift function of the convex lens (S20). Therefore, the sample point interpolation process only needs to be performed before Fourier transform.

S31 is a fast Fourier transform (FFT) calculation. When the number of calculation points is N, in the normal Fourier transform, the calculation amount is N ² order, whereas in the FFT calculation, the calculation amount is N * log ₂ N order, and as the calculation point N increases, The degree of calculation amount reduction increases. In addition, in the calculation of FFT, it is necessary to match the number of sample points of the function to be Fourier-transformed and the function to be transformed, whereas in Equation (1), the function to be Fourier-transformed is an element image, The function corresponds to the intensity distribution E ₅ of the light field. Calculation range of the intensity distribution E ₅ of the optical field, on the basis of the equation (1), when a constant wavelength sampling interval and the light of the hologram created surface W, the convex lens M _i - distance between the hologram forming surface W is larger Enlargement, that is, the number of sample points increases.

Therefore, when the intensity distribution E ₅ of the light field is calculated using FFT, it is necessary to increase the number of sampled pixels of the element image i according to the expansion of the calculation range by the distance between the convex lens M _i and the hologram creation surface W. There is. Therefore, it is assumed that S15 is inserted before the Fourier transform process.

If the sampling interval of the hologram creation surface W and the light wavelength λ are constant, the calculation range of the intensity distribution E ₅ of the light field on the hologram creation surface W is calculated from the convex lens M _i -hologram creation surface according to Equation (1). It can be seen that the larger the distance between W is, the larger the calculation amount is. Therefore, if the distance between the convex lens M _i and the hologram creation surface W is shortened, the amount of calculation is reduced. Such a case will be described as modified examples 2 and 3.

[Modifications 2 and 3]
FIG. 9 is a schematic diagram illustrating the virtual optical system of the second and third modifications. Similar to FIG. 4, the element image group formation surface T is divided into pixel group regions (not shown) of the element images i−1, i, i + 1. Further, the convex lenses M _i−1 , M _i , and M _{i + 1} are arranged so as to be paired with each element image i−1, i, i + 1. The hologram creation surface W is disposed on the right side in FIG. 9 in contact with the exit surfaces of the convex lenses M _i−1 , M _i , and M _{i + 1} .

Therefore, the intensity distribution E ₃ of the light field for each of the element images i−1, i, i + 1 formed on the element image group forming surface T is incident on each convex lens M _i−1 , M _i , M _i−1 . The light field intensity distribution E ₃ is calculated by the light propagation calculation α. Next, each convex lens M _i−1 , M _i , M _{i + 1} receives light of the intensity distribution E ₃ of the light field, and generates an intensity distribution E ₄ of the light field shifted in phase on the exit surface. The intensity distribution E ₄ of the light field is calculated by the phase shift calculation β of each convex lens M _i−1 , M _i , M _{i + 1} .

In this case, since the hologram creation surface W is arranged immediately after the convex lens, the calculation of the intensity distribution of the light field of the object light on the hologram creation surface W does not require Equation (4). It can be calculated in (3). For this reason, the amount of calculation can be reduced. In this case, the intensity distribution E ₄ of the light field on the exit surface of the convex lens coincides with the intensity distribution E ₅ of the light field on the hologram creating surface W. The calculation of only equations (2) and (3) corresponds to the case where d = 0 in equation (1), and the intensity distribution E ₄ (= E ₅ = h (x ₂ , y ₂ )) can be calculated by equation (7).

Here, C ₄ is a constant.
[Modification 2]
FIG. 10 is a conceptual diagram showing a second modification of the process of FIG. This modified example 2 is processing according to the algorithm of Expression (7). Equation (7), when arranged hologram forming surface W immediately after the convex M _i, is to compute the intensity distribution E ₄ of the optical field of the object beam at the hologram production plane W. This expression (7) indicates that the element image i (S10) has the same focal length as the focal length of the convex lens M _i and has a negative sign, that is, a phase shift function of a concave lens having a focal length of (−f). After the multiplication (S21), the obtained product is subjected to Fourier transform processing (S32). Then, the sum of all element images i is calculated (S40), and the intensity distribution E ₅ (= E ₃ = h (x ₂ , y ₂ )) of the light field on the hologram creation surface W is calculated.

[Modification 3]
FIG. 11 is a conceptual diagram of Modification 3 showing a modification of the processing of FIG. The third modification is a case where a fast Fourier transform process is applied to the Fourier transform calculation of Expression (7). In general, in integral photography, the size of the element image i matches the size of the convex lens. When the hologram creation surface W is arranged immediately after the convex lens M _i , the calculation range of the intensity distribution E ₄ of the light field is the same as the size of the element image i. In the calculation of Expression (7), if it is assumed that the element image i and the intensity distribution E ₄ of the light field are sampled at the same sample interval, the number of sample points is the same.

  Therefore, in this embodiment, without interpolating the number of sample points of the element image i (S10) read from the element image storage means 2, the shift function of the concave lens is multiplied (S21), and the fast Fourier transform (FFT) is performed. The calculation algorithm (S33) can be applied, and the calculation speed can be further increased.

  In the description of this embodiment, the description has been made using the intensity distribution of the light field that travels only in one direction (right direction) parallel to the drawing. However, since the intensity distribution of the light field propagates in a three-dimensional space and the calculation region is actually spread over the space, it is desirable to consider the direction perpendicular to the drawing. The vertical direction can also be described in the same manner as in the horizontal direction described above.

  Therefore, in this embodiment, the amount of calculation can be reduced without causing deterioration in the reproduced image. Further, by applying fast Fourier transform (FFT) to the Fourier transform calculation, the amount of calculation can be further reduced. Further, it is possible to effectively execute processing for creating a large amount of hologram data. Therefore, the possibility of becoming an effective technique for a moving image holography apparatus or the like can be expected.

[Outline of hologram display system]
Next, a hologram display system that receives hologram data from the hologram data creation apparatus 1 and displays a hologram based on the hologram data will be described. FIG. 12 is a block diagram illustrating an outline of the hologram display system according to the embodiment. The hologram display system 10 mainly includes a frame memory 11, an image forming unit 12, a reproduction illumination light irradiation unit 13, and a display control unit 14. The hologram data creation device 1 and the hologram display system 10 are connected via various communication lines and broadcast waves.

  The frame memory 11 stores the hologram data created by the hologram data creation device 1 for each frame. The image forming means (device) 12 forms an image corresponding to the object light according to the hologram data created by the hologram data creating device 1 on the image forming surface. The image forming means 12 may be any display as long as it has an image forming surface such as an LCD (Liquid Crystal Display) and a structure capable of irradiating the image forming surface with reproduction illumination light. .

  The reproduction illumination light irradiation means (device) 13 irradiates the image formed by the image forming means 12 with reproduction illumination light from a predetermined direction. Therefore, a hologram is reproduced as a virtual image by interference fringes (holograms) between object light and reference light by an image formed on an image forming surface (not shown). The display control unit 14 controls operations of the frame memory 11, the image forming unit 12, and the reproduction illumination light irradiation unit 13.

  Here, the hologram display system 10 and the hologram data creation device 1 are configured separately, but the hologram display system 10 and the hologram data creation device 1 may be integrated.

[Other variations]
In the hologram data creation apparatus 1 of this embodiment, a CPU (Central Processing Unit) (arithmetic unit) (not shown) of a general computer (not shown) sequentially executes a hologram data creation program developed in a memory (not shown). Thus, it functions as multiplication means 4, Fourier transform means 5, addition means 6 and hologram data creation means 7. The hologram data creating apparatus 1 includes a memory (not shown) for temporary storage. The element image storage unit 2, the phase shift setting unit 3, and the hologram data storage unit 8 are HDD (Hard Disk Drive) or the like. A storage medium read / write device is provided. Further, the present invention is not limited to connecting directly to a computer via an interface, and may be connected to another computer via various networks such as a LAN (Local Area Network) and the Internet. Each of the means may be configured as an electronic circuit, particularly an IC chip.

Moreover, although the said embodiment demonstrated the hologram of monochromatic light, it is possible to apply similarly to the hologram of multicolor light (color). In this case, the hologram data may include red, green, and blue color data for each pixel.
Further, in the above embodiment, the creation of hologram data in the case of light has been described. However, since the hologram is also generated by a wave such as an electric field or a sound field having a wavelength other than light, the present invention is also applied when the wave is replaced with a wave other than light. Belongs to the range.

It is a block diagram which shows the structure of the hologram data production apparatus of embodiment. It is a schematic diagram explaining the recording principle of the element image by integral photography technology. It is a schematic diagram explaining the principle which optically reproduces a hologram from a plurality of element images. It is a schematic diagram explaining the optical system which the light radiated | emitted from the element image propagates to a hologram preparation surface via a convex lens. FIG. 5 is a schematic diagram for explaining a region on a hologram creation plane W of an intensity distribution of a light field for each pixel in the optical system shown in FIG. 4. It is a conceptual diagram explaining the flow of the main processes of the hologram data production apparatus of embodiment. It is a conceptual diagram explaining the flow of a process of a comparative example. It is a conceptual diagram which shows the modification 1 of the process of FIG. It is a schematic diagram which shows the virtual optical system of the modifications 2 and 3. FIG. It is a conceptual diagram which shows the modification 2 of the process of FIG. It is a conceptual diagram of the modification 3 which shows the deformation | transformation of the process of FIG. It is a block diagram explaining the outline | summary of the hologram display system carrying the hologram data production apparatus of embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hologram data creation apparatus 2 Element image storage means 3 Phase shift setting means 4 Multiplication means 5 Fourier transform means 6 Addition means 7 Hologram data creation means 8 Hologram data storage means 10 Hologram display system 11 Frame memory 12 Image formation means 13 Reproduction illumination light Irradiation means 14 Display control means E ₅ Light field intensity distribution i Element image M Lens group M _i Convex lens O (↓) Inverted image O (↑) Erect image O _r Reference light O _c Coherent light p Pixel spacing R Element image group recording Surface T Element image group forming surface (image forming surface)
U Hologram recording surface W Hologram creation surface X Subject (object)

Claims (5)

Interference between the reference light and the intensity distribution of the light field generated by superimposing the object light emitted from each of the multiple elemental images that represent the object from multiple viewpoints. A hologram data creation device for creating hologram data for displaying an image corresponding to stripes on a display,
According to a phase shift function corresponding to a lens whose principal point is an intersection on the optical axis between the element image arranged on the front focal plane and a lens constituting the pair of lenses facing the element image. Phase shift setting means for setting the phase shift amount;
By multiplying the luminance data for each pixel included in the element image by the phase shift amount set by the phase shift setting means, the light field after the phase shift having the product calculated as a result as an element is obtained. A multiplication means for obtaining an intensity distribution;
Fourier transform means for Fourier transforming the product calculated by the multiplication means to calculate the intensity distribution of the light field on the hologram creation surface for each element image;
An adding means for calculating the sum of the superposition of the light field intensity distributions of the object light for each of the element images calculated by the Fourier transform means to obtain the light field intensity distribution on the hologram creating surface;
A light field intensity distribution obtained by superimposing the light field intensity distribution calculated by the adding means and the light field intensity distribution of the reference light is calculated, and interference fringes appearing as the intensity distribution of the superimposed light field are calculated. Hologram data creating means for creating brightness data for each pixel for displaying a corresponding image on a display as hologram data;
A holographic data creation device comprising: The phase shift setting means includes a convex lens whose optical axis with the lens constituting the pair of lenses facing the element image is the intersection point passing through the element image, or the focal length of the convex lens and the absolute distance The amount of phase shift calculated by the phase shift function of the concave lens with the same value is set,
The hologram data creation device according to claim 1. The Fourier transform means performs a fast Fourier transform process;
The hologram data creation device according to claim 1 or 2, characterized in that: Interference between the reference light and the intensity distribution of the light field generated by superimposing the object light emitted from each of the multiple elemental images that represent the object from multiple viewpoints. A hologram data creation method for creating hologram data for displaying an image corresponding to a stripe on a display,
The luminance data for each pixel included in the element image, and the intersection point on the optical axis between the element image arranged on the front focal plane and the lenses constituting the lens group that is opposed to the element image are mainly used. A multiplication step of multiplying the phase shift function according to the phase shift function corresponding to the lens as the point, and obtaining the intensity distribution of the light field after the phase shift using the product calculated as a result,
Fourier transform step of calculating the intensity distribution of the light field on the hologram creation surface for each element image by Fourier transforming the product calculated in this multiplication step;
Calculating the sum of the superposition of the light field intensity distributions of the object light for each element image calculated in the Fourier transform step, and adding the light field intensity distribution on the hologram creation surface;
A light field intensity distribution obtained by superimposing the light field intensity distribution calculated in the adding step and the light field intensity distribution of the reference light is calculated, and interference fringes appearing as the intensity distribution of the superimposed light field are calculated. Hologram data creation step of creating luminance data for each pixel for displaying a corresponding image on a display as hologram data;
A method for creating hologram data, comprising: Interference between the reference light and the intensity distribution of the light field generated by superimposing the object light emitted from each of the multiple elemental images that represent the object from multiple viewpoints. In order to create hologram data that displays an image corresponding to the stripes on the display,
The luminance data for each pixel included in the element image, and the intersection point on the optical axis between the element image arranged on the front focal plane and the lenses constituting the lens group that is opposed to the element image are mainly used. Multiplication means for multiplying the phase shift function according to the phase shift function corresponding to the lens as the point, and obtaining the intensity distribution of the light field after the phase shift using the product calculated as a result,
Fourier transform means for Fourier transforming the product calculated by the multiplication means to calculate the intensity distribution of the light field on the hologram creation surface for each element image,
An adding means for calculating a sum of superposition of the intensity distributions of the light field of the object light for each element image calculated by the Fourier transform means to obtain an intensity distribution of the light field on the hologram creating surface;
A light field intensity distribution obtained by superimposing the light field intensity distribution calculated by the adding means and the light field intensity distribution of the reference light is calculated, and interference fringes appearing as the intensity distribution of the superimposed light field are calculated. Hologram data creation means for creating brightness data for each pixel for displaying a corresponding image on a display as hologram data,
Hologram data creation program characterized in that it functions as

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