CN105954993A - Color holographic three-dimensional display method and system based on space division - Google Patents

Abstract

The invention belongs to the field of computational holographic three-dimensional display, and relates to a color holographic three-dimensional display method and system based on space division. The display system uses a CCD camera or computer graphics method to obtain multi-view two-dimensional images of color target objects, and generates a set of target images suitable for phase hologram calculation after preprocessing and transformation; iterative Fourier transform algorithm is used to calculate the corresponding Phase-type hologram; the single-chip spatial light modulator is divided into three sub-areas of red, green, and blue, and each sub-area is loaded with the corresponding red, green, and blue three-color component hologram, and the hologram reproduced by hologram diffraction Features Generate three monochromatic holographic reconstruction images on the reconstruction plane, and directional diffract the pixels of the corresponding reconstruction images to a fixed position to form different viewpoints, obtain multi-view color reproduction images, and realize true-color three-dimensional display; combined with spatial light modulation The device quickly refreshes and loads the hologram, realizing multi-view true color full parallax dynamic holographic three-dimensional reproduction.

Description

A color holographic three-dimensional display method and system based on space division

technical field

The invention relates to a three-dimensional display method, in particular to a spatial light modulator-based holographic three-dimensional display method and device, and belongs to the field of computational holography and three-dimensional display.

Background technique

With the rapid development of display technology and computer science, people have put forward higher requirements for display technology in medical imaging, commercial art, military defense and other aspects. These requirements are far beyond the scope of the current two-dimensional (2D) display. Therefore, true-color three-dimensional (3D) display has become an inevitable requirement of the modern information society and an important goal of the development of modern display technology. As a near-perfect imaging technology, color holographic 3D display can not only provide true-color 3D images that are almost close to the real world, but also provide 3D vision at all viewpoints and at all distances. The reconstructed scene is almost the same as the original Like the scenery, it is the most attractive true color 3D representation. However, the currently constructed systems cannot meet the desired quality and technical requirements of true-color 3D displays. Color holographic displays still face many challenges, and the key problem to be solved is to provide color experience while bringing 3D experience to the observer.

At this stage, scholars have proposed many ways to realize color holographic display, which can be roughly divided into two categories, one is the color information display realized by traditional holographic application of holographic dry plate, and the other is the application of computational holographic light modulation device to carry holographic information. Colored information display for graph implementation.

The traditional holographic method refers to the use of the principle of holographic recording and reproduction to reproduce all the information (including amplitude information and phase information) of a three-dimensional object. experience. The purpose of color holography is to record and reproduce color three-dimensional holographic images, which involves two basic issues: the acquisition of three primary color information and the reproduction of three primary color information. However, when lasers containing three primary colors are used instead of monochromatic lasers for holographic recording, three holograms are obtained on the same holographic dry plate, which are respectively coherently formed by red, green, and blue lasers. , each wavelength of laser will reproduce three holograms with different sizes and slightly different positions, three wavelengths of laser will reproduce nine holograms, they overlap, and the image appears blurred, this phenomenon is called color Therefore, solving color crosstalk is also an important research topic of color holography. Aiming at these two problems, scholars have carried out related research work. For example, in 1962, Soviet scholar Denisyuk first proposed a reflective hologram. When recording, the reference light wave and object information come from both sides of the photosensitive plate, and the photosensitive medium records the interference light field between the object light wave and the reference light wave. Color object information can be observed on the same side as the light source. However, the size of its recorded hologram is restricted by the size of the laser beam, which limits its application in the production of large-area holograms and restricts its application in practice. In 1969, Benton first used the two-step method to make a rainbow hologram. The rainbow hologram is the product of the combination of image holography and slits. It can reproduce holographic information under natural light. The recording optical path may have a greater energy utilization rate, but the disadvantage is that the two-step recording process is cumbersome, and due to the two-step recording, the noise of the hologram is relatively large. In 1978, Chinese-American scholars Chen Xuan and Yang Zhenghuan proposed a step-by-step rainbow holography, which uses a lens to image objects and slits, and places a holographic dry plate between the object image and the slit image. From the perspective of light propagation, through The object light wave of the real slit interferes with the reference light after passing through the lens to form a rainbow hologram, which greatly simplifies the production process and reduces the noise, but the energy utilization rate is low, and the observation range is limited by the relative aperture of the imaging lens, and the production is large. Volumetric objects require high-cost, high-quality, large-aperture lenses. Due to the above shortcomings, the practical range of this manufacturing method is limited. In 2010, Nature magazine reported that Blanche et al. in the United States realized a near-real-time dynamic holographic display with a refresh time of 2 s in a photorefractive polymer, and the display size was 4 inches × 4 inches. The display principle is as follows: the preprocessed two-dimensional images of several perspectives of the three-dimensional object are sequentially loaded on the spatial light modulator to form object light waves, which interfere with the reference light waves on the recording medium to form a holographic unit called Hogel. Control the movement of the recording medium to record the next picture, and proceed in sequence to obtain a holographic volume view composed of holographic units. When the readout light is reproduced, the pictures of several viewing angles of the three-dimensional object will be reproduced, and the human eye will have a three-dimensional effect when observing it. After the erasing light is introduced, the information recorded on the previous medium can be erased to prepare for the display of the next image. In order to realize the color holographic three-dimensional display, the method of angle multiplexing is used in the experiment, and three holograms are written at different angles at the same time, and read out with different color LEDs, and finally the effect of color holographic three-dimensional display can be realized. In fact, the limitation of this type of color holography is mainly reflected in the fact that the recording medium is a traditional optical recording medium, which cannot meet the real-time and dynamic display requirements, thus greatly limiting its application in display.

The computational holography method refers to the use of red (R), green (G), and blue (B) three-color lasers as light sources, and the use of light modulation devices to carry holograms to realize the modulation of laser light, and then realize color holographic display. Among them, the spatial light modulator loaded with hologram is a kind of holographic optical element, which can modulate the amplitude or phase of laser light, and has the potential to reproduce any light field. The advantage of this type of color holographic display is that it can realize dynamic holographic display, and at the same time has the advantages of laser display, such as high spectral brightness, large color gamut, and rich color saturation. The application of such methods to realize color holographic display mainly includes the following methods: time division multiplexing, space division multiplexing, space division and space superposition.

1. Time-division multiplexing: Red (R), green (G), and blue (B) are displayed sequentially at a certain rate, and color information display is realized through the visual persistence effect of the human eye. This method requires the hardware carrying the three-color information to have a high response speed. When the speed reaches a certain level, the human eye perceives a temporally synthesized color image through the integral effect. The color holographic display system based on the time-division multiplexing method has a simple structure and uses fewer devices, especially only one information-carrying medium device is needed to realize color display. However, it needs to accurately ensure the synchronization of the working time of the monochromatic light source and the time of loading the corresponding color component hologram. There is a certain energy loss on the time axis for monochromatic components. At the same time, because of the high-speed switching of three monochrome holograms to synthesize a color holographic reconstructed image, the system also puts forward higher requirements on the response time of the spatial light modulator. For example, the color holographic display system based on time-division multiplexing constructed by Wang Tao et al. in 2011 used an independent RGB three-color laser as a light source, and used a laser-spatial light modulator synchronous control device to control time-sharing illumination and corresponding hologram loading synchronization Finally, the CCD is used to collect the holographic photoelectric reconstruction image to realize the color holographic display.

2. Space division multiplexing: Red (R), green (G), and blue (B) three-color light sources are used to respectively illuminate three spatial light modulators for optical reconstruction, and realize three monochromatic holographic reproductions on the reconstruction plane synthesis of images. During holographic reproduction, the calculated three monochromatic holograms are loaded onto the corresponding spatial light modulators at the same time, and the driving circuit drives the three spatial light modulators to work at the same time. The RGB three-color holographic reproduction image is registered and synthesized in space to obtain a color holographic reproduction image. The color holographic display system based on the space division multiplexing method has higher optical efficiency, and has many advantages in terms of color reproduction and resolution, and is an important direction for the development of color holographic display. However, it should be pointed out that the structure of the system constructed by this method is relatively complex, and many devices are used. For example, three spatial light modulators are required, and color synthesis components are required to synthesize three-color light, which increases the cost of the system, and the system There is also the problem of precise registration when the three monochromatic holographic reconstructed images are synthesized in space. For example, the color holographic display system based on space division multiplexing established by Wang Yue et al. in 2012 borrowed from the structure of commercial projectors. Three pieces of liquid crystal on silicon (LCOS) are arranged in a U shape. Realize color holographic display.

3. Space division: use a single-chip high-resolution spatial light modulator to divide it into three sub-regions: red (R), green (G), and blue (B), and each sub-region is loaded with the corresponding red and green , blue three-color component hologram, using the characteristics of hologram diffraction and reproduction to form a color holographic reproduction image on the reconstruction plane. Although the color holographic display system based on the space division method uses less spatial light modulators, it sacrifices the resolution of the red, green, and blue three-color holograms, which will have a serious impact on the display quality of the holographic reconstructed image. . For example, in the color holographic display system based on space division established by Michal Makowski et al. in 2010, the single-chip spatial light modulator is divided into three areas, and the calculated three-color component holograms are respectively loaded into the corresponding 1/3 area. The function of the aperture makes each laser beam only irradiate 1/3 of the area of the spatial light modulator, and the holographic reproduction method is used to realize the color holographic display, but this method corresponds to the richness of the displayed information and the display quality of the reproduced image is relatively low .

4. Spatial superposition: A three-color holographic reconstruction image is formed at different positions on the same plane, and the interesting color holographic reconstruction image is composed of the overlapping intersection of three monochromatic holographic reconstruction images. For example, in 2004, Japanese scholar Tomoyoshi Ito proposed a method of realizing color holographic display based on a single-chip spatial light modulator. Red, green, and blue LEDs are distributed in space in a right-angled triangle shape, and each hologram reproduces The positions of the three monochromatic holographic reproduction images obtained from the information of the three components are different from each other, and the effective part of the color holographic reproduction image is only the middle synthesis area of the three-color components, and the information of the reproduction image has not been fully utilized, resulting in the loss of a large amount of information. loss, which brings great limitations to the reproduction of complex objects.

The above methods to achieve color holographic display have their own characteristics, but in the face of the massive amount of computing data in 3D object holographic recording, the current system based on these methods cannot meet the desired quality and technical requirements of true color 3D display. In response to this problem, in 2013, Hewlett-Packard used the principle of diffractive optics to design a pixel-type nano-grating directional backlight structure under waveguide backlight illumination, combined with liquid crystal display (LCD) technology to achieve large field of view, full parallax, and high-resolution color display. Naked-eye 3D display, the results of which were published in the journal Nature, has aroused widespread concern in the industry. This new structure is mainly composed of a light guide plate, a collimated light source, a light source coupling device, and nano-grating pixels. The collimated light is incident on the surface of the nano-grating pixel at a specific angle through the coupling device. By designing a nano-grating with a specific period and orientation angle, its outgoing direction can be precisely adjusted to realize the directional export of light, and its direction modulation range is large. The modulation accuracy is high, and the corresponding 3D display system has a large viewing angle and small crosstalk. Moreover, combined with LCD image refresh technology, this system can realize the effect of dynamic three-dimensional display. However, in order to realize true color display, a hexagonal structure light guide plate is used in this article to achieve directional export of red, green and blue light. However, this hexagonal light guide plate does not match the existing flat panel display methods. Moreover, the preparation of nano-gratings by means of electron beam exposure has low production efficiency and high cost, which also limits its application in display.

In China, the research on color dynamic holographic three-dimensional display is still in its infancy, and there are no relatively mature prototypes and engineering applications. In view of this situation, the present invention proposes a color holographic three-dimensional display method and system based on space division, aiming at realizing true-color multi-view dynamic holographic naked-eye three-dimensional display.

Contents of the invention

The object of the present invention is to provide a color holographic three-dimensional display method and system based on space division. Based on the principle of space-divided color holographic display, it overcomes the shortcomings of the existing technology, such as large amount of computing data, slow calculation speed, and difficulty in realizing dynamic 3D display, and aims to design a true-color dynamic holographic 3D display device based on space division to achieve true color. The dynamic holographic three-dimensional display lays a theoretical and experimental foundation for the development of the future true-color three-dimensional video display system.

In order to achieve the above technical objectives, the principle of using the present invention to realize true-color dynamic holographic three-dimensional display: use the camera to scan and shoot or use commercial software such as 3DS MAX and Maya to obtain the multi-viewpoint color two-dimensional image corresponding to the color three-dimensional object by the method of computer graphics. Image (viewing angle 1, viewing angle 2, ... viewing angle N), decompose each color viewing angle image into red (R), green (G), blue (B) three-color component images (R ₁ , G ₁ , B ₁ ; R ₂ ,G ₂ ,B ₂ ;...R _N ,G _N ,B _N ), and regrouping can get a series of monochrome images (R ₁ ,R ₂ ,...R _N ; G ₁ ,G ₂ ,...G _N ; B ₁ , B ₂ ,...B _N ), after horizontal transformation, vertical transformation and pixel arrangement processing, the target image (R _object , G _object , B _object ) suitable for phase hologram calculation is obtained. The corresponding phase-type holograms (R _H , G _H , B _H ) were calculated by using iterative Fourier transform algorithm (IFTA) programming. Based on the method of spatially partitioning color holographic display, combined with the schematic diagram of the optical path shown in Figure 6, using a single-chip spatial light modulator 6, it is divided into three sub-regions of red (R), green (G), and blue (B) , each sub-region is loaded with the corresponding red, green and blue three-color component holograms (R _H , G _H , B _H ), and three monochromatic holographic reconstruction images are generated on the reconstruction plane by using the characteristics of hologram diffraction reproduction ( R _image , G _image , B _image ), realize color information reproduction. Using the directional diffraction screen 10 based on the pixel-type nano-grating as the directional light-splitting element to separate the holographic reproduction image, form different viewpoints, and obtain multi-view color reproduction images (color viewpoint 1, color viewpoint 2,...color viewpoint N), and realize True color 3D display. At present, the refresh rate of commercial liquid crystal-on-silicon spatial light modulator (LCOS) can reach 75Hz or higher, and can be used in dynamic color video display. Therefore, the phase-type hologram corresponding to the image is calculated by calculating the hologram. When the hologram is reproduced, the red LED light source 13, the green LED light source 14, and the blue LED light source 15 respectively emit red, green, and blue three-color lights. The colored lights are respectively filtered by the corresponding pinholes 2 and collimated by the collimating lens 3 to form collimated plane light waves that enter the corresponding polarization modulation device 4. The polarization modulation device 4 modulates the polarization state of the incident light, and the obtained polarized light enters the The light filter 5 , the red, green and blue three-color reproduced light emitted after being filtered by the light filter 5 respectively enters the three sub-regions of red, green and blue on the spatial light modulator 6 . The red (R), green (G), and blue (B) sub-regions on the single-chip spatial light modulator 6 are respectively loaded with corresponding red, green, and blue three-color component holograms (R _H , G _H , B _H ), red, green, and blue reproduced light are irradiated on the red, green, and blue sub-regions of the spatial light modulator respectively, and three monochromatic holographic reconstructed images (R _image , G _image , _Image B) is separated into different viewpoints after being guided by the directional diffraction screen 10 to realize color three-dimensional display. Accompanied by the fast refreshing and loading of the spatial light modulator 6, the human eyes continuously observe different color parallax images, resulting in a true-color dynamic three-dimensional display effect.

Specifically, the technical scheme adopted in the present invention is:

A color holographic three-dimensional display method based on space division, comprising the following steps:

1). Acquisition steps of multi-view two-dimensional images of colored three-dimensional target objects: using camera scanning and shooting or using computer graphics methods to obtain a sequence of full parallax images of colored three-dimensional objects within a viewing angle range;

2). Image preprocessing transformation step: decompose each acquired color perspective image into red (R), green (G), blue (B) three-color component images (R ₁ , G ₁ , B ₁ ; R ₂ , G ₂ ,B ₂ ;…R _N ,G _N ,B _N ), regrouping the three-color component images can get a series of monochrome images (R ₁ ,R ₂ ,…R _N ;G ₁ ,G ₂ ,… G _N ; B ₁ , B ₂ ,...B _N ), after horizontal transformation, vertical transformation and pixel arrangement processing, the target image (R _object , G _object , B _object ) suitable for phase hologram calculation is obtained;

3). The acquisition step of the phase hologram: the target image (R _object , G _object , B _object ) is used as the data source for calculating the phase hologram, and the corresponding phase hologram is obtained according to the diffraction theory programming calculation;

4). The design and production steps of the directional diffraction screen: according to the position and number of viewpoints, use the generalized grating equation to calculate the period and grid line orientation of the corresponding pixel-type nano-grating, and design the pixel-type according to the color pixel distribution obtained after the pixel arrangement Structural distribution of nano-gratings, using continuous ultraviolet variable space frequency lithography system to fabricate directional diffraction screens based on pixel-type nano-gratings;

5). Holographic reproduction step: build a holographic reproduction display system with the spatial light modulator as the core device and the directional diffraction screen based on the pixel-type nano-grating as the directional light splitting device, and divide the single-chip spatial light modulator into red (R), Green (G) and blue (B) three sub-areas, each sub-area is loaded with corresponding red, green and blue three-color component holograms (R _H , G _H , B _H ), design and manufacture optical filters, filter The size of the light sheet is the same as the size of the spatial light modulator panel. This filter is set in sequence with non-overlapping red filter areas, green filter areas and blue filter areas, corresponding to the red filter, green filter and a blue filter, and the size of the filter for each color is the same as the size of the hologram of the same color component. The optical filter is placed in front of the spatial light modulator to ensure that the optical filter of any color, the hologram of the same color component and the reproduced light are on the same straight line. During the holographic reproduction, the three-color light emitted by the red LED light source, the green LED light source, and the blue LED light source passes through the pinhole, the collimating lens, and the polarization modulation device, and the red, green, and blue three-color reproduced light emitted enters the filter. The reproduced light of red, green and blue emitted after being filtered by the filter is respectively incident on the three sub-regions of red, green and blue on the spatial light modulator. At the same time, the computer loads the calculated red, green, and blue three-color component holograms (R _H , G _H , B _H ) to the red, green, and blue sub-blocks on the spatial light modulator respectively through the drive board. In the region, the reconstructed light wave passes through the spatial light modulator loaded with a hologram, and then the diffracted light wave is imaged on the reconstruction plane, which corresponds to the holographic reconstruction image plane, and three monochromatic holographic reconstruction images are obtained on this plane. At the position of the holographic reproduction image plane, there is a pre-designed and manufactured directional diffraction screen. The nano-grating pixels in the directional diffraction screen diffract the corresponding reproduction image pixels to a fixed position to form different viewpoints and obtain multi-view color reproduction. image, to achieve true color three-dimensional display.

The camera scanning shooting in the step 1) can use a single CCD camera to move horizontally and vertically to shoot the target object, or a two-dimensional array composed of multiple CCD cameras can shoot at different angles.

The image preprocessing transformation process in the described step 2) is divided into five steps. The first step is to decompose the acquired color perspective image into red (R), green (G), blue (B) three-color component images ( R ₁ ,G ₁ ,B ₁ ; R ₂ ,G ₂ ,B ₂ ;…R _N ,G _N ,B _N ), the second step of regrouping can get a series of monochrome images (R ₁ ,R ₂ ,… R _N ; G ₁ ,G ₂ ,…G _N ;B ₁ ,B ₂ ,…B _N ), the third step is for horizontal transformation, the fourth step is for vertical transformation, and the horizontal transformation and vertical transformation Before the transformation, number the sampled original images, group all the sampled two-dimensional images into a two-dimensional image array, the dimension is I×J, and each image number is X _ij ,i(=1,2 ,...,I) corresponds to the position in the horizontal direction, j (=1,2,...,J) corresponds to the vertical direction, and each image X _ij has the same dimension, which is M×N, that is, the number of pixels in the image is M×N, in the process of horizontal transformation, X _ij whose horizontal dimension is M is expressed as a vector as X _ij =(x _{ij1 ,x ij2 ,} .x _ijk ..,x _ijM ), where the vector x _ijk is an N-order vector, representing the kth column pixel in the image matrix X _ij , extracting a certain pixel column from (x _{ij1 , x ij2 ,} .x _ijk .., x _ijM ), and extracting from all two-dimensional image arrays Extract I pixel columns to form a new image; in the vertical direction transformation process, Y _ij whose vertical dimension is N is represented as Y _ij =(y _{ij1 , y ij2 ,} .y _ijk ..,y _ijN ) ^T , T means to transpose the matrix, where the vector y _ijk is an M-order horizontal vector, representing the kth row of pixels in the image matrix Y _ij , from (y _{ij1 ,y ij2 ,} .y _ijk . .,y _ijN ) Extract a certain pixel row from ^T , extract J pixel rows from the two-dimensional array of all images, and form a new image; use the generated image sequence for the pixel arrangement in the fifth step, and finally obtain the applicable The target image (R _object , G _object , B _object ) calculated by phase type hologram.

The phase-type hologram in step 3) is a phase-type hologram calculated based on the principle of iterative Fourier transform algorithm, which is loaded by the spatial light modulator.

In the holographic reproduction process in the step 5), the spatial light modulator is controlled to quickly refresh and load the phase-type hologram to reproduce the multi-view true-color full-parallax dynamic holographic three-dimensional image of the target object.

Based on the above method, the present invention provides a color holographic three-dimensional display system based on space division, including a red LED light source 13, a green LED light source 14, a blue LED light source 15, and sequentially arranged on the optical axis for displaying the three colors. The pinhole 2 for filtering the light emitted by the LED light source, the collimating lens 3 for changing the light wave passing through the pinhole 2 into a plane light wave, the polarization modulation device 4 for modulating the polarization state of the incident light, and the optical filter 5, The spatial light modulator 6 used to load the phase-type hologram generated by the computer 8 is used to directional diffract the holographic reproduction image of the reconstruction plane to a fixed direction to realize the directional diffraction screen 10 of directional light guide, which is characterized in that: It includes a drive board 7 for driving the spatial light modulator 6 to load a hologram, a computer 8, the drive board 7 and the computer 8 are connected by cables, the pinhole 2 is placed on the object focus of the collimator lens 3, and the filter The red filter area, the green filter area and the blue filter area which do not overlap each other are arranged successively on the light sheet 5, respectively corresponding to the red filter, the green filter and the blue filter, and the size of the filter 5 is The size of the panel of the spatial light modulator 6 is the same, and the size of the filter of each color is the same as the size of the hologram of the same color component. The pixel-type nano-grating is arranged on the directional diffraction screen 10, and the directional diffraction screen 10 is in the light The position on the axis coincides with the reproduced image plane position of the hologram loaded on the spatial light modulator 6 .

In the above technical solution, the red LED light source 13, the green LED light source 14, and the blue LED light source 15 can be replaced by a white LED light source 1 synthesized by red, green, and blue primary color LEDs, and its spectral range is similar to that of the filter used. The light sheet 5 has the same spectral range.

In the above technical solution, the polarization modulation device is a polarizer or a half wave plate.

In a preferred technical solution, the spatial light modulator is a reflective or transmissive spatial light modulator, and the modulation mode is phase modulation.

The period of the pixel-type nano-grating is 0.3-3 microns.

Due to the use of the above-mentioned technical solutions, the present invention has the following advantages compared with the prior art:

1. The color holographic three-dimensional display system provided by the present invention has a simple structure and uses fewer devices, especially only one spatial light modulator is needed, which is beneficial to reduce costs;

2. The color holographic three-dimensional display system provided by the present invention uses the spatial light modulator to quickly refresh and load the hologram, which can realize multi-view true color full parallax dynamic holographic three-dimensional display, which is more in line with the observation habits of human eyes;

3. The color holographic three-dimensional display system provided by the present invention utilizes the characteristics of no conjugate image when the spatial light modulator is loaded with a phase-type hologram to reproduce, and can improve the utilization rate of the spatial bandwidth product of the spatial light modulator;

4. The color holographic three-dimensional display system provided by the present invention uses the directional diffraction screen based on the pixel-type nano-grating as the light-splitting element, which improves the space bandwidth product. Since the period of the nano-grating structure can be 300 nanometers, for visible light wavelengths, the The diffraction angle under the incident angle can reach 90 degrees, and the opening angle of the corresponding viewpoint can be close to 180 degrees, and can actually reach 150 degrees. Therefore, the viewing angle corresponding to the color holographic three-dimensional display method in the present invention is large, and the viewing angle is not limited to horizontal movement Observation, can also rotate observation;

5. The color holographic three-dimensional display system provided by the present invention uses the directional diffraction screen based on the pixel-type nano-grating as a light splitting element to perform wavefront conversion on the incident light and form a viewpoint in front of the diffraction screen, which can ensure that the images of each viewing angle are in space. No crosstalk, improving the accuracy of image separation;

6. The color holographic three-dimensional display system provided by the present invention uses a spatial light modulator to load a hologram to reproduce and obtain a color two-dimensional perspective image, which belongs to frequency domain processing, regardless of whether it uses an image mask or a liquid crystal display (LCD) to directly display the image Both belong to spatial domain processing, so the corresponding color holographic three-dimensional display method of the present invention is more flexible and convenient in processing images in the frequency domain than in the spatial domain.

Description of drawings

Figure 1 is a technical roadmap of color holographic 3D display based on space division;

Fig. 2 is a diagram of a banded arrangement of color pixels;

Fig. 3 is a schematic diagram of the Iterative Fourier Transform Algorithm (IFTA);

4 is a schematic diagram of grating pixel diffraction;

Fig. 5 is a schematic diagram of directional light guide of a directional diffraction screen;

FIG. 6 is a schematic structural diagram of a first embodiment of a color holographic three-dimensional display system based on space division;

FIG. 7 is a schematic structural diagram of a second embodiment of a color holographic three-dimensional display system based on space division;

FIG. 8 is a schematic structural diagram of a third embodiment of a color holographic three-dimensional display system based on space division;

Fig. 9 is a schematic diagram of an optical filter corresponding to the panel of the spatial light modulator;

FIG. 10 is a schematic diagram of loading a three-color hologram on a spatial light modulator after space division.

Among them, angle of view 1, angle of view 2, ... angle of view N are multi-view color two-dimensional images corresponding to color three-dimensional objects, and R _i , G _i , _Bi are the red (R), green (G), and blue (B) three-color component images, R _objects , G _objects , and B _objects are target images suitable for phase-type hologram calculations, and R _H , G _H , B _H are corresponding phases Type hologram, R _image , G _image , and B _image are three monochrome holographic reconstruction images on the reconstruction plane, color viewpoint 1, color viewpoint 2,...color viewpoint N is the color viewpoint image obtained on the observation plane;

I is the amplitude distribution of the hologram, I' is the constrained amplitude of the hologram, O is the amplitude distribution of the reproduced image, O' is the amplitude distribution of the target image, is the phase distribution of the hologram, In order to reproduce the phase distribution of the image, FFT is a fast Fourier transform, IFFT is an inverse fast Fourier transform, and e is a mathematical constant;

xyz is the space Cartesian coordinate system, _ki and k _d are the effective wave vectors of the incident wave and the transmitted wave respectively, G is the grating vector, α ₁ and β ₁ are the angles between the incident light and the x-axis and y-axis respectively, α ₂ and β ₂ are the angles between the diffracted light and the x-axis and y-axis respectively;

1-white LED light source, 2-pinhole, 3-collimator lens, 4-polarization modulation device, 5-optical filter, 6-spatial light modulator, 7-drive board, 8-computer, 9-holographic reproduction image , 10-directional diffraction screen, 11-observation plane, 12-beam splitting prism, 13-red LED light source, 14-green LED light source, 15-blue LED light source;

The Red area is a red filter, the Green area is a green filter, and the Blue area is a blue filter;

R _H is a red component hologram, G _H is a green component hologram, and B _H is a blue component hologram.

detailed description

The "a color holographic three-dimensional display method and system based on space division" of the present invention will be further described below in conjunction with the drawings and embodiments.

Embodiment 1: A color holographic three-dimensional display method and system based on space division. Figure 1 is the overall technical roadmap of the present invention, including the following steps:

Step 1), acquisition of multi-view two-dimensional images of colored three-dimensional objects. A full parallax image sequence of a color three-dimensional object within a viewing angle can be obtained by using a camera to scan and shoot or using commercial software such as 3DSMAX and Maya by means of computer graphics.

Step 2), image preprocessing transformation. Decompose each acquired color perspective image into red (R), green (G), blue (B) three-color component images (R ₁ , G ₁ , B ₁ ; R ₂ , G ₂ , B ₂ ; ... R _N ,G _N ,B _N ), regrouping the three-color component images can get a series of monochrome images (R ₁ ,R ₂ ,…R _N ; G ₁ ,G ₂ ,…G _N ; B ₁ ,B ₂ , ...B _N ), after horizontal transformation, vertical transformation and pixel arrangement processing, the target image (R _object , G _object , B _object ) suitable for phase hologram calculation is obtained.

Step 3), calculation of the phase hologram. The target image (R _object , G _object , B _object ) is used as the data source to calculate the phase hologram, and the corresponding phase hologram is calculated by using iterative Fourier transform algorithm (IFTA) programming according to the diffraction theory.

Step 4), design and manufacture of the directional diffraction screen. According to the position and number of viewpoints, use the generalized grating equation to calculate the corresponding grating pixel period and grid line orientation, adjust the groove depth, duty cycle and other parameters to optimize the diffraction efficiency, and design pixel-type nano-gratings according to the color pixel distribution obtained after pixel arrangement The structural distribution of the pixel-type nano-grating is established, and the directional diffraction screen based on the pixel-type nano-grating is fabricated by using the continuous ultraviolet variable space frequency lithography system.

Step 5), holographic reproduction. Build a holographic display system with the spatial light modulator as the core device and the directional diffraction screen based on the pixel-type nano-grating as the directional light-splitting device, apply the method of space division to carry out holographic reproduction experiments, and control the rapid response of the spatial light modulator to the phase-type hologram Refresh and load to realize the effect of true-color dynamic holographic three-dimensional display.

The multi-view two-dimensional image of the color three-dimensional object described in step 1) is obtained by a single CCD camera moving along the horizontal direction and the vertical direction to shoot the target object, or a two-dimensional array composed of multiple CCD cameras is obtained by shooting at different angles. The method of computer graphics can be used to obtain directly from the three-dimensional model of the target.

The image preprocessing transformation described in step 2) is divided into five steps. The first step is to decompose each color perspective image acquired into red (R), green (G), blue (B) three-color component images (R ₁ ,G ₁ ,B ₁ ; R ₂ ,G ₂ ,B ₂ ;…R _N ,G _N ,B _N ), the second step of regrouping can get a series of monochrome images (R ₁ ,R ₂ ,…R _N ; G ₁ ,G ₂ ,…G _N ;B ₁ ,B ₂ ,…B _N ), the third step is to perform horizontal transformation, the fourth step is to perform vertical transformation, the fifth step is to arrange pixels, and finally The target image (R _object , G _object , B _object ) suitable for phase hologram calculation can be obtained, and the order of the third step and the fourth step can be exchanged.

Taking any one of the three colors of red (R), green (G), and blue (B) as an example, the process of horizontal transformation and vertical transformation is described in detail: before transformation, it is necessary to sample the original image Numbering, grouping all the sampled two-dimensional images into a two-dimensional image array, the dimension is I×J, each image number is X _ij , i (=1,2,...,I) corresponds to the level The position in the direction, j (=1,2,...,J) corresponds to the vertical direction, and the dimensions of each image X _ij are the same, which is M×N, that is, the number of pixels in the image is M×N.

In the process of horizontal direction transformation, X _ij whose dimension is M in the horizontal direction is expressed as X _ij =(x _{ij1 ,x ij2 ,} .x _ijk ..,x _ijM ) in the form of a vector, where the vector x _ijk is a N The order vector represents the pixel in the kth column of the image matrix X _ij , therefore, at this time, X _ij =(x _{ij1 ,x ij2 ,} .x _ijk ..,x _ijM ) is a two-dimensional image composed of M pixel columns image. The process of horizontal transformation is: extract a certain pixel column from (x _{ij1 , x ij2 ,} .x _ijk .., x _ijM ), extract I pixel columns from all two-dimensional image arrays, and form a new image, For example, when j=1, extract the first column of each of X ₁₁ , X ₂₁ ,...,X _I1 and arrange them in sequence as (x ₁₁₁ ,x ₂₁₁ ,x ₃₁₁ ,...,x _I11 ), forming New image matrix, denoted as Y ₁₁ ; extract each second column in X ₁₁ , X ₂₁ ,...,X _I1 , and arrange them in sequence as (x ₁₁₂ ,x ₂₁₂ ,x ₃₁₂ ,...,x _I12 ) , forming a new image matrix, denoted as Y ₁₂ ; and so on until Y _1M =(x _11M , x _21M , x _31M ,...,x _I1M ). At this time, a set of new two-dimensional image sequences, Y ₁₁ , Y ₁₂ , . . . , Y _1M , are obtained. For each j=1, 2, . . . , J, repeat the above steps to obtain J sets of new two-dimensional image sequences. The horizontal transformation of an image array can be expressed as:

$\left(\begin{array}{cccc}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 11</span>}}& {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}& <span\; class="notranslate">\; ...</span>& {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}\mathrm{<span\; class="notranslate">\; J</span>}}\\ {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}& {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; two</span>}}& <span\; class="notranslate">\; ...</span>& {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; J</span>}}\\ <span\; class="notranslate">\; ...</span>& <span\; class="notranslate">\; ...</span>& <span\; class="notranslate">\; ...</span>& <span\; class="notranslate">\; ...</span>\\ {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}& {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}& <span\; class="notranslate">\; ...</span>& {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}\mathrm{<span\; class="notranslate">\; J</span>}}\end{array}\right)<span\; class="notranslate">\; \&DoubleRightArrow;</span>\left(\begin{array}{cccc}{\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; 11</span>}}& {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}& <span\; class="notranslate">\; ...</span>& {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}\mathrm{<span\; class="notranslate">\; m</span>}}\\ {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}& {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; two</span>}}& <span\; class="notranslate">\; ...</span>& {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; m</span>}}\\ <span\; class="notranslate">\; ...</span>& <span\; class="notranslate">\; ...</span>& <span\; class="notranslate">\; ...</span>& <span\; class="notranslate">\; ...</span>\\ {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; J</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}& {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; J</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}& <span\; class="notranslate">\; ...</span>& {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; J</span>}\mathrm{<span\; class="notranslate">\; m</span>}}\end{array}\right)$

The transformation principle of the vertical direction is similar to the transformation process of the horizontal direction. During the transformation process of the vertical direction, Y _ij whose vertical dimension is N is expressed as a vector as Y _ij =(y _{ij1 ,y ij2 ,} .y _ijk ..,y _ijN ) ^T , T means to transpose the matrix, where the vector y _ijk is an M-order horizontal vector, which represents the k-th row of pixels in the image matrix Y _ij , therefore, at this time, Y _ij =(y _ij1 , y _ij2 ,.y _ijk ..,y _ijN ) ^T is a two-dimensional image composed of N pixel rows. The process of vertical transformation is: extract a certain pixel row from (y _{ij1 , y ij2 ,} .y _ijk .., y _ijN ) ^T , extract J pixel rows from the two-dimensional array of all images, and form a new Image, the specific process is similar to the horizontal direction transformation until a new set of two-dimensional image sequences, Z _M1 , Z _M2 ,..., Z _MN , are obtained. The vertical transformation of an image array can be expressed as:

$\left(\begin{array}{cccc}{\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; 11</span>}}& {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}& <span\; class="notranslate">\; ...</span>& {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}\mathrm{<span\; class="notranslate">\; J</span>}}\\ {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}& {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; two</span>}}& <span\; class="notranslate">\; ...</span>& {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; J</span>}}\\ <span\; class="notranslate">\; ...</span>& <span\; class="notranslate">\; ...</span>& <span\; class="notranslate">\; ...</span>& <span\; class="notranslate">\; ...</span>\\ {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}& {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}& <span\; class="notranslate">\; ...</span>& {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; J</span>}}\end{array}\right)<span\; class="notranslate">\; \&DoubleRightArrow;</span>\left(\begin{array}{cccc}{\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; 11</span>}}& {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}& <span\; class="notranslate">\; ...</span>& {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}\mathrm{<span\; class="notranslate">\; N</span>}}\\ {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}& {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; two</span>}}& <span\; class="notranslate">\; ...</span>& {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; N</span>}}\\ <span\; class="notranslate">\; ...</span>& <span\; class="notranslate">\; ...</span>& <span\; class="notranslate">\; ...</span>& <span\; class="notranslate">\; ...</span>\\ {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}& {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}& <span\; class="notranslate">\; ...</span>& {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; N</span>}}\end{array}\right)$

At this time, three sets of image arrays (respectively denoted as mapr, mapg, and mapb) are obtained, which will be applicable to the pixel arrangement in the fifth step, wherein: The fifth step is to arrange the pixels. It is necessary to select an appropriate pixel arrangement method. In this embodiment, a strip arrangement method is selected. As shown in Figure 2, the color pixel distribution map(k,l) obtained after the arrangement satisfies: Therefore, the finally obtained target images (R _objects , G _objects , B _objects ) suitable for phase hologram calculation are: where t is a positive integer.

The principle of the iterative Fourier transform algorithm (IFTA) described in step 3) is shown in Figure 3, through multiple iterations of Fourier transform and its inverse transform, until the amplitude distribution obtained on the reproduced image plane is consistent with the desired Until the similarity of the obtained amplitude distribution is as expected, that is, to make the reconstructed image plane (Fourier transform plane) output the required target image, at this time, the phase distribution on the holographic plane can be obtained, and the phase type corresponding to the target image can be obtained. Hologram.

The calculation method of grating pixel period and grid line orientation described in step 4) is as follows: according to the position and number of viewpoints, calculate the period and grid line orientation of each grating pixel, specifically the schematic diagram of grating pixel diffraction can be established, as shown in Figure 4 As shown, assume that the incident ray is a plane wave:

U _i (r) = A _i (r) exp(-ik _i r) (1)

Similarly, the transmitted wave passing through the nanograting pixel unit can be expressed as:

U _d (r) = A _d (r) exp(-ik _d r) (2)

Among them, A _i (r) and A _d (r) are the amplitudes of the incident wave and the transmitted wave, respectively; _ki and k _d are the effective wave vectors of the incident wave and the transmitted wave, respectively. According to the Ramennes theory, for the nano-grating pixel shown in Figure 4, the relationship between the incident light wave and its first-order diffracted light can be written as:

k _d =k _i −G (3)

Among them, G is the grating vector, its value |G|=2π/Λ, Λ is the period of the grating pixel, |k _i |=n2π/λ, |k _d |=2π/λ, combined with the equation

(3), the grating period in the x direction and y direction can be expressed as:

$\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; \&Lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; cos\&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; cos\&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

$\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; \&Lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; cos\&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; cos\&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

Among them, Λ _x and Λ _y are the components of the grating period in the x direction and the y direction respectively; n is the effective refractive index of the diffraction screen; α ₁ and β ₁ are the angles between the incident light and the x axis and the y axis respectively, α ₂ and β ₂ are the angles between the diffracted light and the x-axis and y-axis, respectively. Combining equations (4) and (5), the grating period and the angle between the grating vector and the y-axis can be calculated as:

$\mathrm{<span\; class="notranslate">\; \&Lambda;</span>}<span\; class="notranslate">\; =</span>\sqrt{\frac{{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; cos\&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; cos\&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; cos\&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; cos\&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

After calculating the grating pixel period and grating line orientation corresponding to each coordinate according to this method, the directional diffraction screen based on the pixel-type nano-grating can be efficiently produced by using the continuous ultraviolet variable space frequency lithography system, and the directional diffraction screen guides light As shown in Figure 5, after the incident light enters the diffraction screen, each pixel grating diffracts the corresponding incident light to a fixed direction to realize directional light guide.

The structure diagram of the first embodiment of the color holographic three-dimensional display system described in step 5) uses the spatial light modulator as the core device and the directional diffraction screen based on the pixel-type nano-grating as the directional light splitting device is shown in Figure 6, Including 13-red LED light source, 14-green LED light source, 15-blue LED light source, 2-pinhole, 3-collimator lens, 4-polarization modulation device, 5-optical filter, 6-spatial light modulator , 7-driving board, 8-computer, 9-holographic reconstruction image, 10-directional diffraction screen, 11-observation plane. In the holographic reproduction experiment, the single-chip spatial light modulator 6 is divided into three sub-areas of red (R), green (G), and blue (B), and each sub-area is loaded with corresponding red, green, and blue three-color components. Holograms (R _H , G _H , B _H ), as shown in Figure 10, wherein the spatial light modulator 6 can be a variety of pure phase modulation spatial light modulators, such as transmissive or reflective, here the transmissive The phase modulation type spatial light modulator is taken as an example for convenient explanation of the present invention. Secondly, design and make a filter with a structure as shown in Figure 9, the size of the filter 5 is the same as the size of the panel of the spatial light modulator 6, the filter 5 includes a red filter, a green filter and Blue color filter, and the size of the filter for each color is the same as the size of the hologram of the same color component. The optical filter 5 is placed in front of the spatial light modulator 6 to ensure that the optical filter of any color, the hologram of the same color component and the reproduced light are on the same straight line. The red LED light source 13 , the green LED light source 14 , and the blue LED light source 15 respectively emit red, green, and blue three-color lights. After the three-color lights are filtered by corresponding pinholes 2, the reproduced light has spatial coherence and time coherence. After passing through the pinhole 2, the light wave passes through the collimating lens 3 to form a collimated plane light wave and enters the polarization modulation device 4. The polarization modulation device 4 modulates the polarization state of the incident light, and the obtained polarized light enters the filter 5, passes through The red, green and blue reproduced light emitted by the filter 5 is respectively incident on the red, green and blue sub-regions of the spatial light modulator 6 . At the same time, the computer 8 loads the calculated red, green, and blue color component holograms R _H , G _H , and B _H to the red, green, and blue blocks of the spatial light modulator 6 through the drive board 7, respectively. In the sub-region, the reconstructed light wave passes through the spatial light modulator loaded with the hologram, and then the diffracted light wave is imaged on the reconstruction plane, which corresponds to the holographic reconstruction image plane 9, on which three monochromatic holographic reconstruction images are obtained. At the position of the holographic reproduction image surface 9, there is a pre-designed and manufactured directional diffraction screen 10, and the nano-grating pixels in the directional diffraction screen 10 diffract the corresponding reproduction image pixels to a fixed position to form different viewpoints and obtain multiple Perspective color reproduction image. The human eyes can observe different color parallax images in the observation plane 11 composed of viewpoints, so as to produce the feeling of true-color stereoscopic display. With the rapid refresh loading of the hologram by the spatial light modulator, the human eyes can observe the effect of true-color dynamic holographic three-dimensional display.

Embodiment 2: FIG. 7 is a schematic structural diagram of the second embodiment of the color holographic three-dimensional display system based on space division provided by the present invention. Its specific structure is similar to that of the first embodiment, and its implementation principle is the same as that of the first embodiment of the present invention. The two embodiments are the same. However, in this embodiment, the light source is a white LED light source 1 synthesized by red, green and blue primary color LEDs, and its spectral range is required to be the same as that of the optical filter 5 used.

Embodiment 3: FIG. 8 is a schematic structural diagram of the third embodiment of the color holographic three-dimensional display system based on space division provided by the present invention. Its specific structure is similar to that of the second embodiment, and its implementation principle is the same as that of the first embodiment of the present invention. The two embodiments are the same. However, in this embodiment, the spatial light modulator 6 is a reflective phase modulation spatial light modulator, and an additional dichroic prism 12 needs to be added.

To sum up, the present invention discloses a color holographic three-dimensional display method and system based on space division. In the present invention, the method of space division is used to realize true-color holographic three-dimensional display, which brings 3D experience to observers and provides color experience at the same time. Combined with the spatial light modulator to quickly refresh and load the hologram, it can realize true-color dynamic holographic three-dimensional display, which has the characteristics of simple system structure, less components, fast refresh speed, small crosstalk, and large viewing angle.

Claims (10)

1. the color hologram 3 D displaying method divided based on space, comprises the following steps:

1). the obtaining step of color three dimension target object various visual angles two dimensional image: utilize camera-scanning shooting or make to use tricks The method of calculation machine graphics obtains 3 D color object image with complete parallax sequence in an angular field of view；

2). Image semantic classification shift step: be that red (R), green (G), blue (B) are trichroism by the every width color viewing angle picture breakdown obtained Component image (R₁,G₁,B₁；R₂,G₂,B₂；…R_N,G_N,B_N), trichroism component image is grouped again can obtain a series of Monochrome image (R₁,R₂,…R_N；G₁,G₂,…G_N；B₁,B₂,…B_N), after horizontal transformation, vertically conversion and pixel arrangement process Obtain being applicable to the target image (R that phase-type hologram calculates_Thing,G_Thing,B_Thing)；

3). the obtaining step of phase-type hologram: by target image (R_Thing,G_Thing,B_Thing) as the data calculating phase-type hologram Source, obtains corresponding phase-type hologram according to diffraction theory program calculation；

4). the design and fabrication step of orientation diffraction screen (10): according to position and the number of viewpoint, utilize broad sense grating equation meter Calculating cycle and the grid line orientation of corresponding pixel type nanometer grating, the colour element obtained after arranging according to pixel distribution designs The structure distribution of pixel type nanometer grating, utilizes continuous ultraviolet emptying frequency etching system to make and based on pixel type nanometer grating determines To diffraction screen (10)；

5). reconstruction of hologram step: build with spatial light modulator (6) as core devices, orientation based on pixel type nanometer grating Diffraction screen (10) is the reconstruction of hologram display system of orientation optical splitter part, monolithic spatial light modulator (6) is divided into red (R), Green (G), blue (B) three pieces of subregions, every piece of subregion loads corresponding red, green, blue three colouring component hologram (R_H,G_H,B_H), if Counting and make optical filter (5), the size of optical filter (5) is equivalently-sized with spatial light modulator (6) panel, this optical filter (5) Set gradually the red filter district of non-overlapping copies, green filter district and blue filter district, the most corresponding Red lightscreening plate, green filter Mating plate and blue color filter, and the optical filter size of each color and same color component hologram is equivalently-sized.Filter Sheet (5) is placed in the front of spatial light modulator (6), it is ensured that random color optical filter, same color component hologram and reproduction light Three is on the same line.During the reconstruction of hologram, red-light LED light source (13), green light LED light source (14), blue light LED light source (15) are sent out Three coloured light gone out red, green, blue three color reproduction light of outgoing after pin hole (2), collimating lens (3), Polarization Modulation device (4) enters Being incident upon optical filter (5), after optical filter (5) filters, the red, green, blue three color reproduction light of outgoing is incident to spatial light modulation respectively Three pieces of subregions of red, green, blue on device (6).Meanwhile, computer (8) by drive plate (7) by calculated red, Three colouring component hologram (R green, blue_H,G_H,B_H) three pieces of subregions of red, green, blue of being respectively loaded in spatial light modulator (6), Reproduce light wave and image in reconstruction plane by diffraction light wave after being loaded with the spatial light modulator of hologram, i.e. corresponding to holography again Existing image planes (9), obtain three monochromatic holographic reconstructed images on that plane.And in reconstruction of hologram image planes (9) position, be provided with in advance The orientation diffraction screen (10) designed and produced, the nanometer grating pixel in orientation diffraction screen (10) is by corresponding reproduction image pixel It is diffracted into fixing position, forms different viewpoints, obtain various visual angles color reconstructed image, it is achieved true color 3 D stereo shows.

A kind of color hologram 3 D displaying method divided based on space the most according to claim 1, it is characterised in that: institute The step 1 stated) in camera-scanning shooting can use single ccd video camera moving camera shooting mesh both horizontally and vertically Mark thing, it is also possible to the two-dimensional array being made up of multiple ccd video cameras shoots in different angles.

A kind of color hologram 3 D displaying method divided based on space the most according to claim 1, it is characterised in that: institute The step 2 stated) in Image semantic classification conversion process be divided into five steps, the first step will obtain every width color viewing angle picture breakdown For red (R), green (G), blue (B) trichroism component image (R₁,G₁,B₁；R₂,G₂,B₂；…R_N,G_N,B_N), second step is grouped again A series of monochrome image (R can be obtained₁,R₂,…R_N；G₁,G₂,…G_N；B₁,B₂,…B_N), the 3rd step carries out the change of horizontal direction Changing, the 4th step carries out the conversion of vertical direction, and before horizontal transformation and vertical conversion, the original image obtaining sampling enters Line number, all two dimensional images sampling obtained are organized as a two-dimensional image array, and dimension is I × J, and every piece image is compiled Number it is X_ij, i (=1,2 ..., I) position of corresponding horizontal direction, j (=1,2 ..., J) corresponding vertical direction, every piece image X_ijDimension is identical, and the pixel count for M × N, i.e. image is M × N, in the horizontal direction in conversion process, is M by horizontal direction dimension X_ijIt is expressed as X in the way of vector_ij=(x_ij1,x_ij2,.x_ijk..,x_ijM), wherein vector x_ijkIt is a N rank vector, represents Image array X_ijMiddle kth row pixel, from (x_ij1,x_ij2,.x_ijk..,x_ijMA certain pixel column is extracted, from whole two dimensional image battle arrays in) Row extract I pixel column, forms a width new images；In vertical direction conversion process, it is the Y of N by vertical direction dimension_ijWith The mode of vector is expressed as Y_ij=(y_ij1,y_ij2,.y_ijk..,y_ijN)^T, T represents matrix carries out transposition, wherein vector y_ijkIt is one Individual M rank horizontal vector, represents image array Y_ijMiddle row k pixel, from (y_ij1,y_ij2,.y_ijk..,y_ijN)^TThe a certain pixel of middle extraction Go, from all images two-dimensional array, extract J pixel column, form a width new images；The image sequence of generation is used for the 5th The pixel arrangement of step, finally gives and is applicable to the target image (R that phase-type hologram calculates_Thing,G_Thing,B_Thing)。

4. according to a kind of color hologram 3 D displaying method divided based on space one of claims 1 to 3 Suo Shu, its feature Be: described step 3) in phase-type hologram be that the phase-type calculated based on iterative Fourier transform algorithm principle is complete Breath figure, loads for spatial light modulator.

5. according to a kind of color hologram 3 D displaying method divided based on space one of claims 1 to 3 Suo Shu, its feature Be: described step 5) in reconstruction of hologram process, control spatial light modulator and the fast refresh of phase-type hologram loaded, The full parallax of the various visual angles true color dynamic hologram three-dimensional image of reproducing object.

6. the color hologram three-dimensional display system divided based on space, including red-light LED light source (13), green light LED light source (14), blue light LED light source (15), and set successively on optical axis for three-color LED light source (13), (14), (15) are sent The pin hole (2) that is filtered of light, for the light wave after needle passing hole (2) being become the collimating lens (3) of plane light wave, use In the Polarization Modulation device (4) of modulation incident light polarization state, optical filter (5), spatial light modulator (6), orient diffraction screen (10), It is characterized in that: also include, for driving spatial light modulator (6) to load the driving plate (7) of hologram, computer (8), driving Plate (7) is connected by cable with computer (8), and described pin hole (2) is placed in the object focus of collimating lens (3), filters The red filter district of non-overlapping copies, green filter district and blue filter district is set gradually, the most corresponding red filter on sheet (5) Sheet, green color filter and blue color filter, the size of optical filter (5) is equivalently-sized with spatial light modulator (6) panel, and The optical filter size of each color is equivalently-sized with same color component hologram, and described orientation diffraction screen (10) is upper to be arranged Pixel type nanometer grating, orientation diffraction screen (10) position on the optical axis hologram that load upper with spatial light modulator (6) Reproduce image planes position to overlap.

A kind of color hologram three-dimensional display system divided based on space the most according to claim 6, it is characterised in that: institute The red-light LED light source (13) stated, green light LED light source (14), blue light LED light source (15) could alternatively be by Red Green Blue The white LED light source (1) of LED synthesis, and its spectral region is identical with the spectral region of optical filter (5) used.

A kind of color hologram three-dimensional display system divided based on space the most according to claim 6, it is characterised in that: institute The Polarization Modulation device (4) stated is polaroid or 1/2nd wave plates.

A kind of color hologram three-dimensional display system divided based on space the most according to claim 6, it is characterised in that: institute The spatial light modulator (6) stated is reflection-type, or the spatial light modulator of transmission-type, and modulating mode is phase-modulation.

10., according to a kind of color hologram three-dimensional display system divided based on space one of claim 6～9 Suo Shu, it is special Levy and be: the described pixel type nanometer grating cycle is 0.3～3 micron.