JP5099332B2 - Computer-generated hologram - Google Patents

Description

  The present invention relates to a computer-generated hologram and a method for producing the same, and more particularly to a computer-generated hologram capable of reproducing a full-color image and a method for producing the same.

Patent Document 1 discloses a computer generated hologram (computer synthesized hologram) capable of reproducing a full color image under white light and a method for producing the computer generated hologram. The computer generated hologram described in Patent Document 1 is
○ Divide the recording medium into unit areas,
○ In this unit area, three divided areas corresponding to the red area, green area, and blue area are provided.
○ Furthermore, a point light source array having the same number of colors R, G, B information as the divided areas is set on the full color original image surface,
○ Information of each color corresponding to a point light source having RGB color information in a red area, a green area, and a blue area in a unit area is recorded.

  Hereinafter, the manufacturing method will be described. FIG. 17 is a perspective view showing a specific example of the recording method described in Patent Document 1. In FIG. In this example, the original image 10 and the recording medium (recording surface) 20 are each divided in the horizontal direction by a large number of parallel lines (parallel cut surfaces) to define a large number of linear unit areas. That is, as shown in FIG. 17, the original image 10 is divided into a total of M unit areas A1, A2, A3,... Am,... AM, and the recording medium 20 similarly has a total of M unit areas C1. , C2, C3,..., Cm,. When the original image 10 is a stereoscopic image, each of the unit areas A1, A2, A3,..., Am, ... AM is an area obtained by dividing the surface portion of the stereoscopic. Here, the M unit areas on the original image 10 and the M unit areas on the recording medium 20 have a one-to-one correspondence. For example, the mth unit area Am on the original image 10 corresponds to the mth unit area Cm on the recording medium 20.

  The individual unit areas A1, A2, A3, ..., Am, ... AM of the original image 10 are linear areas in which point light sources are arranged in a line. In the example illustrated in FIG. 17, for example, N point light sources Pm1 to PmN are arranged in a line in the m-th unit region Am (Note that depending on the shape of the object of the original image 10, the unit region Am may be For example, if three spheres are arranged, the cut surface has three circular shapes, and point light sources are arranged side by side on each circle.) Further, each unit area C1, C2, C3,..., Cm,... CM of the recording medium 20 is divided into three as shown by broken lines in FIG. Here, the divided areas C1r, C1g, and C1b are divided areas obtained by dividing the unit area C1 shown in FIG.

  Then, the interference fringes for the calculation point Q on an arbitrary divided area in an arbitrary unit area of the recording medium 20 are obtained as follows. Here, Cmr is selected as an arbitrary divided region, but the same applies to Cmg and Cmb. First, a unit area Am on the original image 10 corresponding to the unit area Cm to which the calculation point Q belongs is determined as a calculation target unit area. Then, the object lights Om1r to OmNr of the color R emitted from the point light sources Pm1 to PmN in the calculation target unit area Am (when the divided areas are Cmg and Cmb, the object lights Om1g to OmNg of the color G and the color B, respectively) If the interference fringes formed at the calculation point Q by the combined light including the phases of the object lights Om1b to OmNb) and the reference light Lθmr of the same color R are obtained, the interference fringes at the target calculation point Q are obtained. Here, the reference light Lθmr is a monochromatic parallel ray parallel to the YZ plane. The reference light Lθmr may be oblique reference light instead of being parallel to the YZ plane.

  FIG. 19 is a top view for explaining the concept of such arithmetic processing, and shows a state in which the original image 10 and the recording medium 20 shown in FIG. 18 are viewed from above. As shown in FIG. 19, the object light necessary for obtaining the interference fringes at the calculation point Q is, for the color R divided region Cmr, N point light sources Pm1,..., Pmi,. , PmN is limited to the object light Om1r,..., Omir,..., OmNr of the color R, and for the divided region Cmg of the color G, N point light sources Pm1,. .., OmNg, which is emitted from Pmi,..., PmN, and is limited to only the N point light sources Pm1 in the operation target unit area Am with respect to the divided area Cmb of color B. ,..., Pmi,..., PmN, which is limited to the object light Om1b of color B,..., Omib, ..., OmNb, and it is not necessary to consider the object light from all point light sources constituting the original image 10. . In this way, if predetermined interference fringes are obtained for all the calculation points Q defined on the recording medium 20, the distribution of interference fringes can be obtained on the recording medium 20.

  FIG. 20 is a side view showing a state where a color original image recorded by the method as described above is being reproduced. The recording medium 20 is irradiated with white illumination light Lw (parallel light parallel to the YZ plane) set as virtual illumination with an angle α. Here, a set of point light sources P1 (P11,..., P1i,..., P1N is represented by a point light source P1 in the divided regions C1r, C1g, and C1b positioned above the recording medium 20. The same applies to Pm and PM. ) Are recorded, but during reproduction, the reproduction light of each color component travels in the direction of the virtual viewpoint E as shown in the figure. The same applies to the reproduction light from the divided areas Cmr, Cmg, Cmb located in the middle of the recording medium 20 and the reproduced light from the divided areas CMr, CMg, CMb located below the recording medium 20. Eventually, if the viewpoint is placed at the position of the virtual viewpoint E, reproduction lights of colors R, G, and B related to the point light source P1 are obtained from the divided areas C1r, C1g, and C1b, respectively, and from the divided areas Cmr, Cmg, and Cmb, respectively. The reproduction lights of the colors R, G, B relating to the point light source Pm are obtained, respectively, and the reproduction lights of the colors R, G, B relating to the point light source PM are obtained from the divided regions CMr, CMg, CMb, respectively. A color original image composed of the point light sources P1, Pm, and PM is observed with high color reproducibility.

Further, the computer generated hologram described in Patent Document 2 emits reproduction light of each color component in the slit group in parallel during reproduction, and the reproduction light travels in the direction of the virtual viewpoint. Eventually, if the viewpoint is placed at the position of the virtual viewpoint, one of the reproduction lights of the colors R, G, and B can be obtained. Since the other two colors have different wavelengths, some aberrations and the like occur. An image close to the original color image to some extent is observed.
JP 2000-214751 A JP 2001-331085 A JP 2002-72837 A JP 2005-215570 A JP 2004-309709 A JP 2004-264839 A "3D Image Conference '99 -3D Image Conference '99-" Lecture Collection CD-ROM (June 30-July 1, 1999, Kogakuin University Shinjuku Campus), Paper "Image Binary CGH by EB Drawing ( 3)-Improvement of stereoscopic effect by hidden surface removal and shading- Junpei Uchiuchi “Holography” pp. 33-36 (Nagisabo Co., Ltd., issued on November 5, 1997)

However, in the computer-generated hologram produced by the manufacturing method of Patent Document 1 and Patent Document 2, the main spatial frequency of each wavelength in the vertical direction changes slightly from the upper end toward the lower end, so that the vertical direction of each wavelength in the divided region It is necessary to recalculate the main spatial frequency of the system, which is computationally intensive.
If the cycle, which is the reciprocal of the main spatial frequency in the vertical direction, is an integral multiple of the address unit at the time of machining (unit for which coordinates can be specified as drawing data for the machined figure), the same pattern may be machined repeatedly. Since the main spatial frequency in the vertical direction is different for each divided area from the upper end to the lower end of the composite hologram, it cannot be set to an integer multiple of the address unit at the time of processing in all the divided areas. It is necessary to calculate and process all the interference fringe patterns up to the lower end, the calculation load increases, and the amount of data for processing increases dramatically, so the processing load increases.

  The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide a computer-generated hologram capable of reproducing a full-color image and suppressing calculation load and processing load. is there.

  The present invention solves the above-described problem, and is a computer composition in which amplitude information and phase information of a color original image expressed by a plurality of wavelengths are recorded on a predetermined recording medium using a calculation using a computer. In a hologram, a large number of linear divided areas are set by dividing the hologram recording surface in the horizontal direction by a large number of parallel cutting planes, and corresponding to periodically different wavelengths in the direction crossing the large number of divided areas. Amplitude information and phase information to be recorded, and when reproduced by a predetermined illumination, the reproduction light of periodically different wavelengths diffracted from the amplitude information and phase information recorded in each divided region, It is configured so as to travel in parallel planes through each of the divided regions on the hologram recording surface.

  The reproduction light is configured to travel in a plane orthogonal to the hologram recording surface.

  In addition, information regarding the same part of the original image is recorded at each point belonging to the same divided area, and information regarding a corresponding different part of the original image is recorded at each point belonging to a different divided area. It is characterized by.

  In addition, the amplitude information and the phase information recorded in each divided region are recorded as interference fringes between the object light and the reference light.

  In addition, the amplitude information and phase information recorded in each divided area are recorded as a three-dimensional cell having a groove on one surface where the phase is recorded by the depth of the groove and the amplitude is recorded by the width of the groove. And

  Further, there are three periodically different wavelengths recorded in the divided areas, which are red, green, and blue wavelengths, respectively.

  According to the present invention, during reproduction, the reproduction light of each color component travels in parallel planes through each divided area on the hologram recording surface, so the same color is used in all divided areas from the upper end to the lower end. Are the same vertical spatial frequency. For example, the red vertical spatial frequencies are all the same in the red segment from the top to the bottom, and the green vertical spatial frequencies are all the same in the green segment from the top to the bottom. The spatial frequency in the vertical direction is the same in all blue divided regions from the upper end to the lower end. Therefore, it is not necessary to recalculate the vertical spatial frequency of the same color for each divided region.

  Also, since the vertical spatial frequency of each color is common to all the divided areas, the vertical spatial frequency of each color in each divided area is constant, and the reciprocal period is also constant. Therefore, if a cycle that is an integer multiple of the processing address is set for each color, the target interference fringe pattern can be processed by repeated processing of the same pattern, and there is no need to calculate the entire interference fringe pattern in the divided area, Calculation load is reduced. Furthermore, the amount of processing data is small, and the processing load is reduced.

  Further, it is not necessary to set the observation distance from the hologram, and it can be produced at any observation position. Further, the viewing area in the vertical direction is widened from the upper end to the lower end of the hologram.

  Hereinafter, a method for producing a computer-generated hologram (CGH) of the present invention and an example of a computer-generated hologram obtained by the method will be described with reference to the drawings. FIG. 1 is a perspective view showing an embodiment of the concept of the recording method according to the present invention. In this embodiment, the original image 10 and the recording medium (recording surface) 20 are divided in the horizontal direction by a large number of parallel lines (parallel cut surfaces) to define a large number of linear divided areas. That is, as shown in FIG. 1, the original image 10 is divided into a total of 3M divided regions A1r, A1g, A1b, A2r, A2g, A2b,..., Amr, Amg, Amb,. The recording medium 20 is similarly divided into a total of 3M divided areas C1r, C1g, C1b, C2r, C2g, C2b,..., Cmr, Cmg, Cmb,. When the original image 10 is a stereoscopic image, each of the divided areas A1r, A1g, A1b, A2r, A2g, A2b,..., Amr, Amg, Amb, ..., AMr, AMg, AMb divides the surface portion of this solid. It becomes the area obtained by. Here, the 3M divided areas on the original image 10 and the 3M divided areas on the recording medium 20 have a one-to-one correspondence. For example, the first (mr-th, hereinafter the same) divided area Amr of the r, g, b repetition numbers of the r, g, b on the original image 10 is the r, g, b on the recording medium 20. This corresponds to the first divided region Cmr in the repetition number m.

  The individual divided areas A1r, A1g, A1b, A2r, A2g, A2b,..., Amr, Amg, Amb,..., AMr, AMg, AMb of the original image 10 are linear areas in which point light sources are arranged in a line. It has become. In the example shown in FIG. 1, for example, in the mr-th divided region Amr, point light sources Pmr1 to PmrN that emit N-color R (red) light in a fan shape in a plane including the divided region Amr and the divided region Cmr. Are in a row. Similarly, in the mg-th divided area Amg, point light sources Pmg1 to PmgN that emit N-color G (green) light in a fan shape in a plane including the divided areas Amg and Cmg are arranged in a line. In the mbth divided area Amb, point light sources Pmb1 to PmbN that emit light of N colors B (blue) in a fan shape in a plane including the divided areas Amb and Cmb are arranged in a line.

  And the interference fringe about the calculation point Q in an arbitrary divided area of the recording medium 20 is obtained as follows. Here, Cmr is selected as an arbitrary divided region, but the same applies to Cmg and Cmb. First, a divided area Amr on the original image 10 corresponding to the divided area Cmr to which the calculation point Q belongs is determined as a calculation target divided area. Then, the object lights Omr1 to OmrN of the color R emitted from the point light sources Pmr1 to PmrN in the calculation target divided area Amr (when the divided areas are Cmg and Cmb, the object lights Omg1 to OmgN of the color G and the color B, respectively) If the interference fringes formed at the calculation point Q by the combined light (object light) including the phases of the object lights Omb1 to OmbN) and the reference light Lθmr of the same color R are obtained, the interference at the target calculation point Q is obtained. It is a stripe. Here, the reference light Lθmr is a monochromatic parallel ray parallel to the YZ plane. The reference light Lθmr may be oblique reference light instead of being parallel to the YZ plane.

  FIG. 2 is a top view for explaining the concept of such arithmetic processing, and shows a state in which the original image 10 and the recording medium 20 shown in FIG. 1 are viewed from above. As shown in FIG. 2, the object light necessary for obtaining the interference fringes at the calculation point Q is, for the color R divided region Cmr, N point light sources Pmr1,..., Pmri,. , PmrN emitted from PmrN are limited to only Omr1, ..., Omri, ..., OmrN, and for the divided region Cmg of color G, N point light sources Pmg1, ..., Pmgi, ..., PmgN in the calculation target divided region Amg. , OmgN,..., OmgN emitted from N, and the divided region Cmb of color B is emitted from N point light sources Pmb1,..., PmbN in the calculation target divided region Amb. , Ombi,..., OmbN, and it is not necessary to consider object light from all point light sources constituting the original image 10. In this way, if predetermined interference fringes are obtained for all the calculation points Q defined on the recording medium 20, the distribution of interference fringes can be obtained on the recording medium 20.

  Since the recording method as described above is employed, on the original image 10, M repetitive units each including the R color slice plane, the G color slice plane, and the B color slice plane are arranged in parallel. ing. On the recording medium 20, the repetitive unit in which the R-color slice plane, the G-color slice plane, and the B-color slice plane on which the corresponding RGB interference fringes are respectively recorded is a single unit. It will be arranged in parallel.

  FIG. 3 is a diagram schematically showing a method for producing the computer-generated hologram of the present invention in the above example. As described above, the original image (object) 10 is composed of a large number of linear divided regions A1r in the horizontal direction. , A1g, A1b, A2r, A2g, A2b,..., Amr, Amg, Amb,..., AMr, AMg, AMb, and the recording medium 20 is also divided into areas A1r, A1g, A1b of the original image (object) 10. , A2r, A2g, A2b,..., Amr, Amg, Amb,..., AMr, AMg, AMb, a plurality of horizontal divided regions C1r, C1g, C1b, C2r, C2g, C2b,. It is divided into Cmr, Cmg, Cmb,..., CMr, CMg, CMb. When the divided area A1r, A1g, A1b, A2r, A2g, A2b,..., Amr, Amg, Amb,..., AMr, AMg, AMb of the original image (object) 10 is h / 3, the recording medium 20 The corresponding widths or pitches of the divided areas C1r, C1g, C1b, C2r, C2g, C2b, ..., Cmr, Cmg, Cmb, ..., CMr, CMg, CMb are similarly h / 3. The RGB repetition pitch on the recording medium 20 is h / 3 × 3 = h.

  FIG. 4 is a side view showing a state where a color original image recorded by the method as described above is being reproduced. The recording medium 20 is irradiated with white illumination light Lw (parallel light parallel to the YZ plane) set as virtual illumination with an angle α. Here, in the divided regions C1r, C1g, and C1b positioned above the recording medium 20, a set of point light sources P1r (P1r1,..., P1ri,..., P1rN is represented by a point light source P1r. P1g, P1b, and the like are also included. Similarly, the information of each of the colors R, G, and B of P1g and P1b is recorded, but at the time of reproduction, as shown in the drawing, the information passes through the divided areas C1r, C1g, and C1b on the hologram recording medium 20, respectively. It is configured to travel in parallel planes. In particular, the reproduction light is preferably configured to travel in a plane orthogonal to the hologram recording medium 20.

  The same applies to the reproduction light from the divided areas Cmr, Cmg, Cmb located in the middle of the recording medium 20 and the reproduced light from the divided areas CMr, CMg, CMb located below the recording medium 20.

  In the end, assuming that the virtual viewpoint E is sufficiently separated from the recording medium 20, reproduction lights of the colors R, G, and B relating to the point light sources P1r, P1g, and P1b are obtained from the divided areas C1r, C1g, and C1b, respectively. From the divided areas Cmr, Cmg, Cmb, reproduction lights of the colors R, G, B relating to the point light sources Pmr, Pmg, Pmb are obtained, respectively, and from the divided areas CMr, CMg, CMb, the point light sources PMr, PMg, Reproduced light of colors R, G, and B relating to PMb is obtained, and an original color image 10 composed of point light sources P1r, P1g, P1b, ..., Pmr, Pmg, Pmb, ..., PMr, PMg, PMb is obtained. It will be observed with high color reproducibility.

  In FIG. 4, only the reproduction light from the divided areas Cmr, Cmg, and Cmb seems to travel at the virtual viewpoint E. However, in actuality, due to the wavelength dispersion of the hologram recording medium 20, a predetermined wavelength is obtained. Since light having a slightly shifted wavelength travels from the upper divided areas C1r, C1g, C1b to the lower divided areas CMr, CMg, CMb to the virtual viewpoint E, the original image (object) ) The image from the upper end to the lower end of 10 can be seen.

  As described above, during reproduction, the reproduction light of each color component passes through each of the divided regions Cmr, Cmg, Cmb on the hologram recording medium 20 and travels in parallel planes. In all the divided areas Cmr, Cmg, and Cmb, the same vertical frequency is used for the same color. That is, the vertical spatial frequency of red R is the same in the red R divided region Cmr from the upper end to the lower end, and the vertical spatial frequency of green G is all in the green G divided region Cmg from the upper end to the lower end. The spatial frequency of the blue B in the vertical direction is the same in the blue B divided region Cmb from the upper end to the lower end. Therefore, there is no need to recalculate for each divided region for the vertical spatial frequency of the same color.

  In particular, when the reproduction light is configured to travel in a plane orthogonal to the hologram recording medium 20, it is not necessary to consider the angle at which the reproduction light travels, and the calculation load is further reduced.

  Further, it is not necessary to set the observation distance from the hologram, and it can be produced at any observation position. Furthermore, in the case of the upper end, it can be seen from above as compared to the case where light is directed toward the line of sight, and in the case of the lower end, it is also visible from below as compared with the case where light is directed toward the line of sight. Wide viewing area.

  In the present embodiment, the original image 10 is sampled at different positions for the colors R, G, and B. However, the original image 10 is sampled at a common position for the colors R, G, and B. The light source positions of the colors R, G, and B may be determined by moving in parallel from the sampling position.

  In this case, first, as shown in FIG. 5, the slice plane and the unit area are determined for the original image 10, and divided into a total of M unit areas A1, A2, A3,. A common sampling position is determined for R, G, and B.

  Next, as shown in FIG. 6, divided areas A1r, A1g, A1b,... Amr, Amg, Amb,... AMr, AMg, AMb corresponding to the colors R, G, B are respectively determined, and the divided areas A1r, A1g are determined. , A1b,... Amr, Amg, Amb,... AMr, AMg, AMb are translated from the common sampling position shown in FIG.

  In this way, a total of M unit areas A1, A2, A3,..., Am,... AM are divided into the divided areas with respect to the original image 10, and the colors R, G, and B are sampled at a common position. The occurrence of deviation can be eliminated.

  Further, with respect to the original image 10, as shown in FIG. 7, instead of the point light sources P1r, P1g, P1b,... Pmr, Pmg, Pmb, ... PMr, PMg, PMb, the line light sources L1r, L1g, L1b,. , Lmg, Lmb,... LMr, LMg, LMb may be applied.

  A case where such line light sources L1r, L1g, L1b,... Lmr, Lmg, Lmb,... LMr, LMg, LMb are applied will be described.

  In this case, first, a slice plane and unit areas A1, A2, A3,... Am,... AM are defined for the original image 10, and each unit area A1, A2, A3,. Dividing into divided regions A1r, A1g, A1b,... Amr, Amg, Amb,.

  Then, as shown in FIG. 8, for example, consider a case where interference fringes between the object light from the line light source Lmri and the reference light Rφ are recorded on the recording medium 20.

  Here, it is assumed that the line light source Lmri is composed of a line segment that is parallel to the recording surface 20 and has a length h. More specifically, in the example shown in FIG. 8, the line light source Lmri is defined so as to be parallel to the Y axis, and the center of the line light source Lmri comes to the position of the reference point Pmri of the point light source in the unit area. It is like that. Here, since the XYZ three-dimensional coordinate system is defined so that the divided areas Amr and Cmr are parallel to the X axis and the recording surface 20 is on the XY plane, the line light source Lmri is parallel to the Y axis. The line light source Lmri is a linear light emitting element having a uniform intensity, and the intensity value may be determined based on, for example, the pixel value of the reference point Pmri on the original image 10. In general, the light from the line light source is light that spreads so that the wavefront becomes a cylindrical shape. When object light traveling from the line light source Lmri on the reference point Pmri is projected onto the XZ plane, a dashed line in FIG. A projected image as shown in FIG. 10 is obtained. When this is projected onto the YZ plane, a projected image as shown by a one-dot chain line in FIG. 10 is obtained.

  In other words, when the system shown in FIG. 8 is observed from above, the object light from the line light source Lmi spreads radially as shown in FIG. 9, but when this system is observed from the lateral direction, The object light from the line light source Lmri is light that travels in the horizontal direction as shown in FIG. Eventually, the object light from the line light source Lmi reaches only the unit region Cmr having the width h in the Y-axis direction without any limitation on the spread angle. Thus, the intensity of the interference wave between the object light from the line light source Lmri and the reference light Rφ is calculated for each calculation point in the unit area Cmr, and interference fringes are recorded in the unit area Cmr. Become.

  In FIG. 8, for convenience of illustration, interference fringes between the object light from the line light source Lmri defined on the i-th reference point Pmri on the unit line segment Amr and the reference light Rφ are recorded in the unit region Cmr. Although only the state is shown, actually, N reference points Pmr1 to PmrN are defined on the unit line segment Amr, and the line light sources Lmr1 to LmrN are defined at the positions of the respective reference points. (Each line light source has a length h and is arranged in a direction parallel to the Y axis so that its center is on the unit line segment Amr). Therefore, in the unit area Cmr, interference fringes between the object light from the N line light sources Lmri to LmrN and the reference light Rφ are recorded in an overlapping manner.

  Further, as shown in FIG. 7, 3M unit line segments A1r, A1g, A1b, .about.Amr, Amg, Amb, .about.AMr are arranged on the original image 10 so as to be parallel to each other with a predetermined pitch h. , AMg, AMb are defined (both are line segments or curve segments parallel to the XZ plane), and a plurality of reference points are defined on all of these unit line segments. A line light source perpendicular to the unit line segment (parallel to the Y axis) is defined. Accordingly, for all 3M divided regions C1r, C1g, C1b, .about.Cmr, Cmg, Cmb, .about.CMr, CMg, CMb shown in FIG. 7, the corresponding unit line segments A1r, A1g, A1b, .about.Amr, Amg are respectively obtained. , Amb, .about.AMr, AMg, AMb, interference fringes between the object light from the line light source defined at a plurality of reference points and the reference light are recorded.

  FIG. 11 is a model showing the reason why the same interference fringe pattern repeats when a line light source is used. First, from the line light source Lmri, the object light O is irradiated in the right direction in the figure from any part. Here, the line light source Lmri is a light source having a uniform intensity in the length direction, and is parallel to the recording medium 20, so that any one of the unit areas having the length h on the recording medium 20 can be used. Regarding the position, the object light O is irradiated under the same conditions, and the amplitude intensity and the phase are exactly the same. As described above, the interference fringe pattern is formed in the unit area even though the object light O is irradiated under the same conditions because the phase of the reference light Rφ is different in each part.

  Now, as illustrated, five light beams R1 to R5 are considered as light beams constituting the reference light Rφ. Originally, the reference light Rφ is a spatially coherent light, so that the phases of these five light beams are all aligned. However, since it is incident on the recording medium 20 at an oblique angle φ, the optical path lengths to reach the recording surface 20 are different from each other, and the phases at the arrival points F1 to F5 are different from each other. For example, the optical path length of the luminous flux R2 is longer than the optical path length of the luminous flux R1 by a predetermined length, and the optical path length of the luminous flux R3 is longer than the optical path length of the luminous flux R2. Here, if this optical path length difference is exactly one wavelength, the phase of the reference light Rφ is different by 2π at the points F1 and F2, and the reference light Rφ is also different at the arrival points F2 and F3. The phase is different by 2π. As a result, the phase of the reference light Rφ is shifted by 2π between the five arrival points F1 to F5. For this reason, the same interference fringe pattern having the period d appears repeatedly on the recording medium 20 four times.

  When this principle is applied to the divided areas for the same colors for the colors R, G, and B, the vertical spatial frequency of the color R is common to the divided areas Cmr, and the vertical spatial frequency of the color G is the divided area. Since the common spatial frequency of Cmg and the vertical spatial frequency of color B are common to the divided region Cmb, the spatial frequency of each of the colors R, G, and B is constant, and the reciprocal period is also constant. Therefore, if a cycle that is an integral multiple of the processing address is set for each of the colors R, G, and B, the target interference fringe pattern can be processed by repeating the same pattern, and all of the divided regions Cmr, Cmg, and Cmb can be processed. It is not necessary to calculate the interference fringe pattern, and the calculation load is reduced. Furthermore, the amount of processing data is small, and the processing load is reduced.

  Next, a method for producing the computer-generated hologram (CGH) according to the present invention will be described with reference to a flowchart.

  A method for producing CGH is well known (for example, see Non-Patent Document 1). As an example of CGH, a binary hologram that records the intensity distribution of interference fringes, and a reproduced image has only a horizontal parallax, An outline of the case of observation with white light from above will be described. As shown in FIG. 12, the shape of the object (original image 10) to be converted to CGH is defined in step ST1. Next, in step ST2, the spatial arrangement of the object, the CGH surface (the recording surface of the recording medium 20), and the reference light is defined. Next, in step ST3, the object is divided into the divided regions in the vertical direction by slicing on the horizontal plane, and further replaced with a set of point light sources (point light source array) on the slice plane. Then, in step ST4, based on these spatial arrangements, the intensity of interference fringes between the light reaching from each point light source constituting the object and the reference light is calculated at each sample point of the divided area defined on the CGH plane. To obtain interference fringe data. Next, in step ST5, the obtained interference fringe data is quantized, and then converted into EB drawing rectangular data in step ST6. In step ST7, the data is recorded on the medium by the EB drawing apparatus to obtain CGH. .

  In the above method, the amplitude and phase of the object light at the calculation point Q on the divided area may be recorded in addition to the method of recording with interference fringes due to interference with the reference light as described above. As described in 2 and 3, the phase may be recorded by the depth of the groove of the three-dimensional cell having a groove on one surface, and the amplitude may be recorded by the width of the groove.

  Alternatively, as described in A.N. W. You may make it record an amplitude and a phase by the method of Lohmann etc., the method of Lee, etc.

  Further, the color of the point light source array arranged in each divided region of the original image 10 is not limited to the three primary colors of RGB as described above, and may be a combination of other colors (wavelengths), and further, three colors. Instead, it may be two colors or four or more colors. When two colors are used, the amount of data can be reduced as compared with three colors. In the case of four or more colors, the color gamut can be expanded compared to three colors.

  Next, it is also possible to apply the method of colorization with high resolution of the computer-generated hologram as in the present invention to other types of computer-generated holograms.

First, a case where the present invention is applied to the computer-generated hologram proposed in Patent Document 4 will be described. As shown in FIG. 13, the virtual point light source group 11, the CGH 12, and the observer M are arranged in the plus direction along the z axis in this order, and the virtual point light source group 11 and the CGH 12 are separated by a large number of slice planes perpendicular to the y axis. In the slice plane, the incidence of the object wave from the virtual point light source Q _i (x ₁ , y ₁ , z ₁ ) to the CGH 12 is limited. In the slice plane, the object wave 1 that is emitted from the virtual point light source Q _i (x ₁ , y ₁ , z ₁ ) in the parallax 1 direction is detected at the pixel position i of the _first image I _1, for example, the character “A”. A wave having density as an amplitude, and a wave having density as an amplitude at the pixel position i of the second image I _2, for example, the letter “B”, are applied to the object wave 1 that appears in the parallax 2 direction. The object wave 1 exiting in eight directions is a wave having an amplitude at the pixel position i of the eighth image I _8, for example, the letter “H” as an amplitude, and these “A”, “B”,. The object wave 1 having the density at the pixel position i of “H” at the same time according to the parallax direction is synthesized. By recording the phase and amplitude of the object wave 1 holographically images I _1, I ₂ vary depending on the parallax direction, · · ·, I _m is selectively reproducible CGH12 obtained.

  In other words, a virtual point light source group is spatially set on the side opposite to the hologram viewing side, and a large number of parallel slice planes crossing the surface of the virtual point light source group and the hologram surface are set, The radiance angle distribution of diverging light that diverges from each virtual point light source of the point light source group to the observation side in the slice plane is angle-divided, and within each divided angle, a separate position located on the surface of the virtual point light source group The divergent light that is set to be equal to the divergent light that diverges in the slice plane from the point that has the amplitude equal to the density of the pixel at the virtual point light source position of the image or a value that has a certain relationship with the density is the object light As a computer-generated hologram recorded at any position on the diverging light incident side of the virtual point light source group.

Further, another computer-generated hologram proposed in Patent Document 4 is arranged in the order of CGH 12, virtual condensing point group 13, and observer M in the plus direction along the z axis, as shown in FIG. The CGH 12 and the virtual condensing point group 13 are divided by a large number of slice planes perpendicular to the y axis, and object waves are incident from the CGH 12 to the virtual condensing point Q _i (x ₁ , y ₁ , z ₁ ) in the slice plane. Limited. In the slice plane, the object wave 1 that once converges to the virtual condensing point Q _i (x ₁ , y ₁ , z ₁ ) and exits in the direction of parallax 1 has the first image I _1, for example, the letter “A”. The wave having the density at the pixel position i as an amplitude is used, and the wave 1 having the amplitude at the pixel position i of the second image I _2, for example, the character “B”, is used as the wave for the object wave 1 that appears in the parallax 2 direction. Similarly, the object wave 1 that appears in the direction of parallax 8 is a wave having the density at the pixel position i of the eighth image I _8, for example, the letter “H” as an amplitude, and these “A” and “B” , ..., the object wave 1 having the density at the pixel position i of "H" at the same time according to the parallax direction is synthesized. By recording the phase and amplitude of the object wave 1 holographically images I _1, I ₂ vary depending on the parallax direction, · · ·, I _m is CGH12 is obtained.

  That is, a virtual condensing point group is spatially set on the observing side of the hologram, and a large number of parallel slice planes crossing the hologram surface and the virtual condensing point group surface are set. The brightness angle distribution of convergent light incident on the virtual condensing point of each light spot group from the side opposite to the observation side in the slice plane is angle-divided, and within each divided angle, the surface of the virtual condensing point group is divided. Convergent light that is set to be equal to the converged light that converges to a point having an amplitude equal to the density of the pixel at the virtual condensing point position of a separate image or a value that is in a fixed relationship with the density of the image at the virtual condensing point. Is a computer-generated hologram recorded at any position on the convergent light incident side of the virtual condensing point group.

In such a computer-generated hologram proposed in Patent Document 4, in order to be able to record and reproduce a full-color image, the plane of CGH 12 intersects with each slice plane as described with reference to FIGS. The region is divided into three divided regions parallel to the slice plane, while the RGB color light is diverged from the virtual point light source Q _i (x ₁ , y ₁ , z ₁ ) to produce R, G, and B colors. The components are separately incident on the three divided areas and recorded, or the virtual condensing point Q _i (x ₁ , y ₁ , z ₁ ) has R, G, and B from the three divided areas of the CGH 12, respectively. Although the color components may be condensed, in this method, as in the computer-generated hologram of FIGS. 1 to 4, when an object having a fine structure is to be recorded on the recording medium, When the width of the unit area to be set is determined, the resolution is set to that width. It will be constant.

  Therefore, the density of the slice plane perpendicular to the y-axis is tripled, and RGB is periodically assigned to the slice plane in a direction orthogonal to the slice plane, and the virtual point light source diverges in the R slice plane. In the slice plane of G, the light or the light condensed on the virtual condensing point is color R, and in the slice plane of B, the light diverging from the virtual point light source or the light focused on the virtual condensing point is color G Then, the light diverging from the virtual point light source or the light condensed to the virtual condensing point is set to color B, so that the resolution of the reproduced image is the virtual point light source group as in the computer-generated hologram of FIGS. 11 or the density of the light condensing points set in the virtual condensing point group 13, so that the density of the point light sources or the condensing points is the same if the dimensions (widths) of the divided regions on the surface of the CGH 12 are the same. Is 3 times the resolution, the resolution is It is possible to record the object with no longer fine structure. However, the reproducibility of the color pattern is about the same.

  In the computer-generated hologram in which the complex amplitude of the object light is recorded and a plurality of images can be selectively reproduced according to the observation direction, a virtual point light source group is spatially set on the side opposite to the observation side of the hologram, and A plurality of parallel slice planes crossing the plane of the virtual point light source group and the plane of the hologram are set, and light of different wavelengths is periodically assigned to the slice planes in a direction perpendicular to the slice plane, In the slice plane, the wavelength of the light diverging from the virtual point light source is set to the assigned wavelength, and the diverging light diverging from the virtual point light source of each virtual point light source group in the slice plane to the observation side in the slice plane. The radiance angle distribution is angle-divided, and within each division angle, the density of the corresponding wavelength of the pixel at the virtual point light source position of a separate image located on the surface of the virtual point light source group or the density thereof is the same. The divergent light set to be equal to the divergent light diverging in the slice plane from the point having the amplitude equal to the value in the relationship is recorded as object light at any position on the diverging light incident side of the virtual point light source group. This is a computer-generated hologram.

  The computer-generated hologram, in which the complex amplitude of another object beam is recorded and a plurality of images can be selectively reproduced according to the observation direction, has a virtual condensing point group spatially set on the observation side of the hologram, and A large number of parallel slice planes crossing the plane of the hologram and the plane of the virtual focal point group are set, and light of different wavelengths is periodically assigned to the multiple slice planes in a direction perpendicular to the slice plane. In the slice plane, the wavelength of the light focused on the virtual focal point is set to the assigned wavelength, and each slice of the virtual focal point group in the slice plane is moved from the side opposite to the observation side to the slice plane. The brightness angle distribution of the convergent light incident on is divided into angles, and within each divided angle, the corresponding wavelength of the pixel at the virtual condensing point position of a separate image located on the surface of the virtual condensing point group is divided. Concentration or constant with that concentration Computer composition in which convergent light set to be equal to convergent light that converges to a point having the same amplitude as the relevant value is recorded as object light at any position on the convergent light incident side of the virtual condensing point group It becomes a hologram.

Next, a case where the present invention is applied to a computer-generated hologram proposed in Patent Document 5 will be described. As illustrated in FIG. 15, the virtual point light source group 11, the object 100, the CGH 12, and the observer M are arranged in the plus direction along the z axis in this order, and the virtual point light source group 11 and The object 100 and the CGH 12 are separated, and the incidence of the object wave from the virtual point light source Q _i (x ₁ , y ₁ , z ₁ ) to the CGH 12 is limited within the slice plane. In the slice plane, a large number of virtual point light sources Q _i (x ₁ , y ₁ , z ₁ ) are set on the opposite side of the observation side of the three-dimensional object 100 that can be recorded and reproduced as CGH 12, and each virtual point light source Q the luminance angular distribution of the divergent light emanating from _i, is set to equal through the three-dimensional object 100 from the viewing side and the luminance angular distribution of the three-dimensional object 100 surface when viewed virtual point light source Q _i, this By diverging the diverging light from the virtual point light source Q _{i on} the surface of the CGH 12 and recording the superimposed phase and amplitude in a holographic manner, a CGH 12 capable of reproducing the three-dimensional object 100 is obtained. .

  In other words, a virtual point light source group is spatially set on the side opposite to the hologram viewing side, and a large number of parallel slice planes crossing the surface of the virtual point light source group and the hologram surface are set, The luminance angle distribution of the divergent light that diverges from each virtual point light source of the point light source group to the observation side within the slice plane, and the object surface to be recorded when the virtual point light source is viewed within the slice plane from the observation side The divergent light that diverges from each virtual point light source is superimposed on each other and recorded as object light at any position on the observation side of the virtual point light source group. This is a computer-generated hologram.

Further, another computer-generated hologram proposed in Patent Document 5 is as shown in FIG. 16 in the order of CGH 12, object 100, virtual condensing point group 13, and observer M in the plus direction along the z axis. The CGH 12, the object 100, and the virtual focal point group 13 are separated by a large number of slice planes that are arranged perpendicular to the y axis, and the virtual focal point Q _i (x ₁ , y ₁ , z ₁ ) from the CGH 12 in the slice plane. Incidence of object waves is limited. Within the slice plane, a large number of virtual condensing points Q _i (x ₁ , y ₁ , z ₁ ) are set on the observation side of the three-dimensional object 100 that can be recorded and reproduced as CGH 12, and each virtual condensing point Q _{i is set.} Is set to be equal to the luminance angle distribution of the surface of the three-dimensional object 100 when the three-dimensional object 100 is viewed through the virtual condensing point Q _i from the observation side. The three-dimensional object 100 can be reproduced by superimposing the convergent lights incident on the virtual condensing point Q _i on the surface of the CGH 12 and recording the superimposed phase and amplitude in a holographic manner. CGH12 is obtained.

  That is, a virtual condensing point group is spatially set on the observing side of the hologram, and a large number of parallel slice planes crossing the hologram surface and the virtual condensing point group surface are set. The luminance angle distribution of convergent light incident on each virtual condensing point of the light spot group from the side opposite to the observation side in the slice plane is as viewed from the observation side in the slice plane through the virtual condensing point. It is set to be equal to the luminance angle distribution on the surface of the object to be recorded, and the converging light incident on each virtual condensing point is superimposed on each other as the object light on the side opposite to the observation side of the virtual condensing point group This is a computer-generated hologram recorded at any one of the positions.

  Also in this case, as in the case of FIGS. 1 to 4, the density of the slice plane perpendicular to the y-axis is tripled, and RGB is periodically assigned to the multiple slice planes in a direction perpendicular to the slice plane. Within the R slice plane, the light diverging from the virtual point light source or the light converging to the virtual condensing point is color R, and within the G slice plane, the light diverging from the virtual point light source or the virtual condensing point is collected. The light to be emitted is color G, and within the slice plane of B, the light that diverges from the virtual point light source or the light that converges to the virtual condensing point is color B, so that the computer-generated hologram of FIGS. Similarly, since the resolution of the reproduced image is determined by the density of the point light source or the condensing point set in the virtual point light source group 11 or the virtual condensing point group 13, the size (width) of the divided area on the surface of the CGH 12 is set. If the same, the density of the point light source or the focal point Amount that has a three-fold, it is possible to record an object resolution with high becomes fine structure. However, the reproducibility of the color pattern is about the same.

  In the computer-generated hologram capable of reproducing the three-dimensional object by recording the complex amplitude of the object light described above, a virtual point light source group is spatially set on the side opposite to the hologram viewing side, and the surface of the virtual point light source group and the hologram A number of parallel slice planes are set across the plane, and light of different wavelengths is periodically assigned to the slice planes in a direction perpendicular to the slice plane. Let the wavelength of the diverging light be the assigned wavelength, and the luminance angle distribution of the diverging light diverging from each virtual point light source of the virtual point light source group in the slice plane to the observation side in the slice plane is When the virtual point light source is viewed in the slice plane, it is set to be equal to the luminance angle distribution of the corresponding wavelength on the surface of the object to be recorded, and the divergent light emitted from each virtual point light source is mutually The superimposed becomes recorded in any position of the virtual point light source group of the observation side as the object beam computer generated holograms.

  In another computer-generated hologram in which the complex amplitude of another object beam is recorded and a three-dimensional object can be reproduced, a virtual condensing point group is spatially set on the observation side of the hologram, and the hologram surface and the virtual condensing point group A large number of parallel slice planes are set across the plane, and light of different wavelengths is periodically assigned to the slice planes in a direction perpendicular to the slice plane. The angle of convergent light incident on the virtual condensing point of each group of virtual condensing points in the slice plane from the side opposite to the observation side in the slice plane. The distribution is set to be equal to the luminance angle distribution of the corresponding wavelength of the object surface to be recorded when viewed in the slice plane from the observation side through the virtual condensing point, and each virtual condensing point Convergent light incident on A computer generated hologram comprising recorded in any position of the side opposite to the viewing side of the virtual condensing point group as the object light to be superimposed on each other.

  As described above, the computer-generated hologram and the manufacturing method thereof according to the present invention have been described based on the embodiments. However, the present invention is not limited to these embodiments, and various modifications are possible.

It is a perspective view which shows one Example of the concept of the recording method of the computer-generated hologram by this invention. It is a top view for demonstrating the concept of the arithmetic processing of FIG. It is a figure which shows typically the preparation methods of the computer-synthesis hologram of this invention of FIG. 1, FIG. It is a side view which shows the state which is reproducing | regenerating the color original image recorded by the method of FIG. It is a figure which shows the sampling point common to RGB on an original image. It is a figure which shows the sampling point of each RGB which translated the sampling point of FIG. It is a figure which shows each linear light source of RGB on an original image. 3 is a perspective view illustrating a method for recording object light from a linear light source on an original image on a recording surface 20. FIG. It is a figure which shows the advancing direction of the object light irradiated from a point light source. It is a figure which shows the advancing direction of the object light irradiated from a line light source. It is a side view which shows the advancing direction of the reproduction | regeneration light at the time of recording the interference fringe of the object light from a linear light source, and reference light. It is a flowchart for demonstrating the outline | summary of the preparation process of the computer composition hologram by this invention. It is a figure for demonstrating the principle of another type of computer-synthesis hologram to which the method of this invention is applicable. It is a figure for demonstrating the principle of another type of computer-synthesis hologram to which the method of this invention is applicable. It is a figure for demonstrating the principle of another type of computer-synthesis hologram to which the method of this invention is applicable. It is a figure for demonstrating the principle of another type of computer-synthesis hologram to which the method of this invention is applicable. It is a perspective view which shows the recording method of the conventional computer composition hologram. FIG. 10 is a plan view showing a state in which each unit area of a recording medium is divided into three to form divided areas in a conventional example. It is a top view for demonstrating the concept of the arithmetic processing of FIG. FIG. 18 is a side view showing a state where a color original image recorded by the method of FIG. 17 is being reproduced.

Explanation of symbols

10 ... Original image 20 ... Recording medium (recording surface)
100 ... Objects A1r, A1g, A1b, A2r, A2g, A2b, ..., Amr, Amg, Amb, ..., AMr, AMg, AMb ... Original image divided regions C1r, C1g, C1b, C2r, C2g, C2b, ..., Cmr, Cmg, Cmb,..., CMr, CMg, CMb, divided regions Pmr1 to PmrN of the recording medium, point light sources Pmg1 to PmgN that emit light of color R, point light sources Pmb1 to PmbN that emit light of color G, Point light source Q that emits light ... Calculation points Omr1 to OmrN ... Object light Omg1 to OmgN of color R ... Object light Omb1 to OmbN of color G ... Object light Lθmr of color B ... Reference light Lw ... White illumination light P1r (P1r1, ... , P1ri,..., P1rN)) Point light source P1g that emits light of color R (P1g1,..., P1gN). Source P1b (P1b1, ..., P1bi, ..., a set of P1bN) ... points emit light of color B light source

Claims (6)

In a computer-generated hologram that records amplitude information and phase information of a color original image expressed by a plurality of wavelengths on a predetermined recording medium using a calculation using a computer,
A large number of linear divided areas are set by horizontally dividing the hologram recording surface by a large number of parallel cut surfaces,
Amplitude information and phase information corresponding to periodically different wavelengths in a direction crossing a large number of divided regions are recorded,
When reproduced by a predetermined illumination, the reproduction light having periodically different wavelengths diffracted from the amplitude information and the phase information recorded in each divided area passes through each divided area on the hologram recording surface, respectively. A computer-generated hologram characterized by being configured to travel in parallel planes.   The computer-generated hologram according to claim 1, wherein the reproduction light is configured to travel in a plane orthogonal to the hologram recording surface.   Information about the same part of the original image is recorded at each point belonging to the same divided area, and information about a corresponding different part of the original image is recorded at each point belonging to a different divided area. The computer-generated hologram according to claim 1 or 2, characterized in that   4. The computer-generated hologram according to claim 1, wherein amplitude information and phase information recorded in each divided area are recorded as interference fringes between object light and reference light.   The amplitude information and the phase information recorded in each divided area are recorded as a three-dimensional cell having a groove on one surface where the phase is recorded by the depth of the groove and the amplitude is recorded by the width of the groove. The computer-generated hologram according to any one of claims 1 to 4.   6. The computer-generated hologram according to claim 1, wherein there are three periodically different wavelengths recorded in the divided areas, and the wavelengths are red, green, and blue, respectively.

Images