阅读说明：本技术 一种基于空间光调制器虚拟阵列拼接的全息3d显示系统 (Holographic 3D display system based on virtual array splicing of spatial light modulator ) 是由 王迪 王琼华 李赵松 李楠楠 李移隆 刘超 于 2021-07-19 设计创作，主要内容包括：本发明提出一种基于空间光调制器虚拟阵列拼接的全息3D显示系统,该系统包括激光器、分束器1、分束器2、反射镜1、快门阵列、空间滤波器阵列、固体透镜、光束偏折元件1、空间光调制器、分束器3、光束偏折元件2和反射镜2。其中,激光器用于产生相干光束。分束器1、分束器2和反射镜1用于将激光器产生的光束分为三路平行光并照射快门阵列。快门阵列用于控制三束光按照设定的时间顺序依次通过。空间滤波器阵列和固体透镜用于将通过快门阵列的三束光分别扩束为三束大小相同、强度均匀的平行光束。控制三个时刻的空间光调制器的衍射光在空间上无缝拼接,当切换速度足够快时,根据人眼的视觉暂留效应,观看者看到空间光调制器虚拟阵列拼接后的衍射光。(The invention provides a holographic 3D display system based on virtual array splicing of a spatial light modulator, which comprises a laser, a beam splitter 1, a beam splitter 2, a reflector 1, a shutter array, a spatial filter array, a solid lens, a light beam deflection element 1, the spatial light modulator, the beam splitter 3, the light beam deflection element 2 and the reflector 2. Wherein a laser is used to generate the coherent light beam. The beam splitter 1, the beam splitter 2 and the mirror 1 are used for splitting the light beam generated by the laser into three paths of parallel light and illuminating the shutter array. The shutter array is used for controlling the three beams of light to sequentially pass through according to a set time sequence. The spatial filter array and the solid lens are used for expanding the three beams of light passing through the shutter array into three parallel beams with the same size and uniform intensity. And controlling the seamless splicing of the diffracted light of the spatial light modulator at three moments, and when the switching speed is fast enough, a viewer sees the diffracted light spliced by the virtual array of the spatial light modulator according to the persistence of vision effect of human eyes.)

1. A holographic 3D display system based on virtual array splicing of a spatial light modulator is characterized by comprising a laser, a beam splitter 1, a beam splitter 2, a reflector 1, a shutter array, a spatial filter array, a solid lens, a light beam deflection element 1, the spatial light modulator, the beam splitter 3, the light beam deflection element 2 and the reflector 2; wherein the laser is used to generate a coherent light beam; the beam splitter 1, the beam splitter 2 and the reflector 1 are used for splitting a light beam generated by the laser into three paths of parallel light and irradiating the shutter array; the shutter array is used for controlling the three beams of light to sequentially pass through according to a set time sequence; the spatial filter array and the solid lens are used for expanding the three beams of light passing through the shutter array into three parallel beams with the same size and uniform intensity, namely a light beam I, a light beam II and a light beam III; the light beam deflection element 1 is positioned in the emergent direction of the three parallel light beams and is used for deflecting the light beam I, the light beam II and the light beam III along three specific directions respectively, and the type of the light beam deflection element 1 is the same as that of the light beam deflection element 2;

at T₁At the moment, the shutter array is controlled to enable the light beam (i) to pass through the beam splitter 3 and then irradiate the spatial light modulator, the diffracted light passes through the beam splitter 3, the light beam deflection element 2 and the reflecting mirror 2, and a viewer sees T₁Diffracted light of the temporal spatial light modulator; at T₂At the moment, the shutter array is controlled to make the light beam irradiate the spatial light modulator, the diffracted light passes through the beam splitter 3, the beam deflection element 2 and the reflector 2, and the viewer sees T₂Diffracted light of the temporal spatial light modulator; at T₃At the moment, the shutter array is controlled to enable the light beam (c) to irradiate the spatial light modulator, the diffracted light passes through the beam splitter 3, the light beam deflection element 2 and the reflecting mirror 2, and a viewer sees T₃Diffracted light of the temporal spatial light modulator; and controlling the seamless splicing of the diffracted light of the spatial light modulator at three moments, and when the switching speed is fast enough, a viewer sees the diffracted light spliced by the virtual array of the spatial light modulator according to the persistence of vision effect of human eyes.

2. The holographic 3D display system based on virtual array stitching of spatial light modulators of claim 1, wherein light is selected from the group consisting ofThe beam deflection element 1 and the beam deflection element 2 are both formed by gluing two refraction prisms with refractive index n and wedge angle alpha and flat glass with refractive index n, the refractive index n and the incidence angleThe wedge angle α and the deflection angle δ satisfy the following relationship:

on the premise that the refractive index n and the wedge angle alpha are not changed, the deflection angle delta only follows the incident angleIs changed; by designing the wedge angle alpha, the refractive index n and the incident angleThe light beam I, the light beam II and the light beam III are irradiated on the same area of the spatial light modulator after passing through the light beam deflection element 1 and the beam splitter 3; the light beam I, the light beam II and the light beam III are modulated by the spatial light modulator, continuously spread after penetrating through the beam splitter 3 and irradiate on the light beam deflection element 2; the three beams of diffracted light form three beams of parallel light again after passing through the beam deflection element 2; when the switching speed of the shutter array is fast enough, the splicing effect of the three beams of parallel light is equivalent to spatially forming virtual array splicing of a spatial light modulator with the transverse size of 3 Mxp and the longitudinal size of Nxp, wherein M is the transverse resolution of the spatial light modulator, N is the longitudinal resolution of the spatial light modulator, and p is the pixel pitch of the spatial light modulator; the beam deflecting element 1, the spatial light modulator, the beam splitter 3, and the beam deflecting element 2 are equivalent to a virtual array of spatial light modulators with a transverse size of 3 mxp and a longitudinal size of nxp.

3. The holographic 3D display system based on virtual array stitching of spatial light modulators of claim 1, whereinThe system realizes the large visual area holographic 3D display by the following method: for a 3D object, calculating to obtain a large-size hologram with the resolution of 3 MxN, averagely dividing the large-size hologram into three sub-holograms with the resolution of MxN along the direction of the transverse resolution of the large-size hologram, and recording the three sub-holograms as a sub-hologram 1, a sub-hologram 2 and a sub-hologram 3; t is₁Controlling a shutter array at a moment to enable a light beam (I) to pass through, and simultaneously loading a sub-hologram 1 onto a spatial light modulator; t is₂Controlling the shutter array to make the light beam pass through and simultaneously loading the sub-hologram 2 on the spatial light modulator; t is₃Controlling the shutter array to make the beam pass through and simultaneously loading the sub-hologram 3 on the spatial light modulator; when the switching time is fast enough, the reconstructed 3D object of the large viewing zone is seen at the viewing distance R due to the persistence of vision effect of the human eye;

in the holographic reconstruction process, when the spatial light modulator virtual array with the transverse size of 3 Mxp is irradiated by parallel light, the maximum diffraction angle theta satisfies the following formula:

wherein λ represents a wavelength; according to the principle of holographic diffraction, the object dimension D satisfies the following equation:

D≤θ×Z-3M×p

analyzing the holographic reconstructed image when the viewing distance is R based on the maximum size of the object, and calling a visual area V' in which the complete holographic reconstructed image can be seen as an effective visual area; calculating diffraction positions of the highest point and the lowest point of the object to obtain:

where Z is the diffraction distance of the holographic reconstruction image.

4. Holographic 3D display system based on virtual array stitching of spatial light modulators according to claim 1, characterized in that theThe system realizes large-size holographic 3D display by the following method: for an object with resolution of AxB, firstly, dividing the object equally into three A/3 xB sub-pictures along the transverse resolution direction, respectively calculating the three sub-pictures to obtain three sub-holograms with resolution of MxN, generating a digital lens with focal length of f, and respectively superposing the phase diagram of the digital lens and the three sub-holograms to obtain a hologram 1, a hologram 2 and a hologram 3; t is₁Controlling a shutter array at a moment to enable a light beam (I) to pass through, and simultaneously loading a hologram (1) on a spatial light modulator; t is₂The shutter array is controlled at any moment to enable a light beam to pass through, and meanwhile, the hologram 2 is loaded on the spatial light modulator; t is₃Controlling the shutter array to make the beam pass through and load the hologram 3 on the spatial light modulator; the above processes are repeatedly circulated, when the switching time is fast enough, the holographic reconstruction images of the three sub-pictures are seamlessly spliced in space due to the visual persistence effect of human eyes, and a viewer sees a large-size holographic reconstruction image; at T₁At the moment, the holographic reconstruction image size d using a single spatial light modulator is:

when the switching speed is fast enough, the size of the hologram 1, hologram 2 and hologram 3 holographic reconstruction image mosaic is 3 d.

One, the technical field

The invention relates to a holographic display technology, in particular to a holographic 3D display system based on virtual array splicing of a spatial light modulator.

Second, background Art

The holographic display technology capable of reconstructing all wavefront information of any 3D object is considered as one of the most ideal 3D display methods, but is limited by the pixel size of the current spatial light modulator, and the viewing visual area and the display size of the holographically reconstructed image based on a single spatial light modulator are very small at present, so that the viewing requirement is difficult to meet. To solve this problem, researchers have proposed a number of solutions. For example, a spatial multiplexing technique of surface stitching of a plurality of spatial light modulators is used to obtain a holographic reconstructed image of a large view area. Although this technique effectively enlarges the field of view of the holographic reconstruction image, the curved surface stitching of multiple spatial light modulators greatly increases the complexity and cost of the system. In order to reduce the complexity of a system spliced by a plurality of spatial light modulators, researchers expand the visual area of a holographic reconstruction image by continuously loading a plurality of sub-holograms on a single spatial light modulator and combining the time division multiplexing technology of structured light illumination.

On the other hand, since the viewing zone and the size of the hologram reconstruction image are restricted from each other, it is very difficult to enlarge the viewing zone and the size of the hologram reconstruction image. In terms of enlarging the size of the holographic reconstruction image, SeeReal technology, germany, produced a holographic 3D display system with a large display window size of 300mm × 200mm using holographic optical elements. A research team of Poland Wash engineering university provides a hologram algorithm capable of transversely amplifying, translating and rotating the holographic reconstructed image, and finally a large-size color holographic reconstructed image of 50mm multiplied by 100mm is generated. In addition, with the rapid development of the super-surface technology in recent years, there are more and more proposals for enlarging the size of the holographic reconstructed image by using the super-surface material, but the processing flow of the materials specifically involved in the proposals is generally complicated, the material cost is high, and further research is needed in the aspect of the practicability of large-size holographic display.

Third, the invention

The invention provides a full-array splicing method based on a spatial light modulator virtual arrayA 3D display system, as shown in fig. 1, includes a laser, a beam splitter 1, a beam splitter 2, a mirror 1, a shutter array, a spatial filter array, a solid lens, a beam deflecting element 1, a spatial light modulator, a beam splitter 3, a beam deflecting element 2, and a mirror 2. Wherein a laser is used to generate the coherent light beam. The beam splitter 1, the beam splitter 2 and the mirror 1 are used for splitting the light beam generated by the laser into three paths of parallel light and illuminating the shutter array. The shutter array is used for controlling the three beams of light to sequentially pass through according to a set time sequence. The spatial filter array and the solid lens are used for expanding the three beams of light passing through the shutter array into three parallel beams with the same size and uniform intensity, namely a beam I, a beam II and a beam III. The beam deflection element 1 is positioned in the emergent direction of the three parallel beams and is used for deflecting the beam (i), the beam (ii) and the beam (iii) along three specific directions of delta, 0 and delta respectively. The beam deflecting element 1 and the beam deflecting element 2 are of the same type, at T₁At the moment, the shutter array is controlled to enable the light beam (i) to pass through the beam splitter 3 and then irradiate the spatial light modulator, the diffracted light passes through the beam splitter 3, the light beam deflection element 2 and the reflecting mirror 2, and a viewer sees T₁Diffracted light of the temporal spatial light modulator; at T₂At the moment, the shutter array is controlled to make the light beam irradiate the spatial light modulator, the diffracted light passes through the beam splitter 3, the beam deflection element 2 and the reflector 2, and the viewer sees T₂Diffracted light of the temporal spatial light modulator; at T₃At the moment, the shutter array is controlled to enable the light beam (c) to irradiate the spatial light modulator, the diffracted light passes through the beam splitter 3, the light beam deflection element 2 and the reflecting mirror 2, and a viewer sees T₃The diffracted light of the temporal spatial light modulator. And controlling the seamless splicing of the diffracted light of the spatial light modulator at three moments, and when the switching speed is fast enough, a viewer sees the diffracted light spliced by the virtual array of the spatial light modulator according to the persistence of vision effect of human eyes.

The structure of the beam deflecting element 1 and the beam deflecting element 2 is shown in fig. 2, and both the beam deflecting element 1 and the beam deflecting element 2 are formed by gluing two refraction prisms with refractive indexes of n and a wedge angle of alpha and plate glass with the refractive index of n. The angle between the emergent beam and the optical axis is called the deflection angle. Taking the light beam I as an example, the refractive index n and the incident angle can be calculated according to the geometrical optics principleThe wedge angle α and the deflection angle δ satisfy the following relationship:

according to the formula (1), under the premise that the refractive index n and the wedge angle alpha are not changed, the deflection angle delta is only changed along with the incident angleMay vary. By designing the wedge angle alpha, the refractive index n and the incident angleThe light beam I, the light beam II and the light beam III are irradiated on the same area of the spatial light modulator after passing through the light beam deflection element 1 and the beam splitter 3. The light beam I, the light beam II and the light beam III are modulated by the spatial light modulator, continuously spread after penetrating through the beam splitter 3 and irradiate on the light beam deflection element 2. Since the beam deflecting element 2 has exactly the same optical properties as the beam deflecting element 1, the three diffracted lights re-form three parallel lights after passing through the beam deflecting element 2.

When the switching speed of the shutter array is fast enough, the splicing effect of the three parallel lights is equivalent to spatially forming virtual array splicing of the spatial light modulator with the transverse size of 3M × p and the longitudinal size of N × p, wherein M is the transverse resolution of the spatial light modulator, N is the longitudinal resolution of the spatial light modulator, and p is the pixel pitch of the spatial light modulator. Thus, the beam deflecting element 1, the spatial light modulator, the beam splitter 3 and the beam deflecting element 2 are equivalent to a virtual array of spatial light modulators with a transverse dimension of 3M × p and a longitudinal dimension of N × p.

The system provided by the invention realizes large visual area holographic 3D display by the following method: as shown in FIG. 3, for a 3D object, a hologram such as an angular spectrum algorithm is usedThe large-size hologram with a resolution of 3 mxn is obtained by the calculation of the image algorithm, and is divided into three sub-holograms with a resolution of M × N on average along the direction of the lateral resolution of the large-size hologram, which are referred to as sub-hologram 1, sub-hologram 2 and sub-hologram 3. T is₁Controlling a shutter array at a moment to enable a light beam (I) to pass through, and simultaneously loading a sub-hologram 1 onto a spatial light modulator; t is₂Controlling the shutter array to make the light beam pass through and simultaneously loading the sub-hologram 2 on the spatial light modulator; t is₃Controlling the shutter array to make the beam pass through and simultaneously loading the sub-hologram 3 on the spatial light modulator; when the switching time is fast enough, the reconstructed 3D object of the large viewing zone is seen at the viewing distance R due to the effect of persistence of vision of the human eye.

As shown in fig. 4, when a virtual array of spatial light modulators with a lateral size of 3M × p is illuminated by parallel light during holographic reconstruction, the maximum diffraction angle θ satisfies the following equation:

where λ represents the wavelength. According to the calculation of the holographic diffraction principle, the object size D satisfies the following formula:

D≤θ×Z-3M×p (3)

where Z is the diffraction distance of the holographic reconstruction image. And analyzing the holographic reconstruction image when the viewing distance is R based on the maximum size of the object, and calling the visual area V' capable of seeing the complete holographic reconstruction image as an effective visual area. Calculating diffraction positions of the highest point and the lowest point of the object to obtain:

in conventional holographic display systems, reconstruction is usually performed using a single spatial light modulator, and when the viewing distance is R', the size of the effective viewing zone is denoted by V ":

therefore, compared with the traditional holographic display system, when the diffraction distance and the viewing distance of the holographic reconstruction image are the same, the system of the invention realizes the expansion of the effective visual area by more than 3 times.

The system provided by the invention realizes large-size holographic 3D display by the following method: as shown in fig. 5, for an object with a resolution of a × B, the object is first divided equally into three sub-pictures of a3 × B along the transverse resolution direction, the three sub-pictures are respectively calculated by using a hologram algorithm such as an angular spectrum algorithm to obtain three sub-holograms with a resolution of M × N, blazed gratings are correspondingly loaded on the three sub-holograms to generate a digital lens with a focal length f, and the phase diagram of the digital lens and the three sub-holograms are respectively superimposed to obtain a hologram 1, a hologram 2, and a hologram 3. T is₁Controlling a shutter array at a moment to enable a light beam (I) to pass through, and simultaneously loading a hologram (1) on a spatial light modulator; t is₂The shutter array is controlled at any moment to enable a light beam to pass through, and meanwhile, the hologram 2 is loaded on the spatial light modulator; t is₃Controlling the shutter array to make the beam pass through and load the hologram 3 on the spatial light modulator; and repeatedly circulating the processes, changing the imaging positions of the holographic reconstructed images by changing the blazed gratings of the holograms loaded on the spatial light modulator, and when the switching time is fast enough, realizing seamless splicing of the holographic reconstructed images of the three sub-pictures in space due to the visual persistence effect of human eyes, so that a viewer sees a large-size holographic reconstructed image.

At T₁At the moment, the holographic reconstruction image size d using a single spatial light modulator is:

when the switching speed is fast enough, the size of the hologram 1, hologram 2 and hologram 3 holographic reconstruction image mosaic is 3 d. Compared with the traditional holographic display system based on a single spatial light modulator, the system disclosed by the invention realizes the enlargement of 3 times of the size of the holographic reconstruction image.

Description of the drawings

FIG. 1 is a schematic structural diagram of a holographic 3D display system based on virtual array splicing of a spatial light modulator.

Fig. 2 is a schematic structural diagram of a beam deflecting device according to the present invention.

FIG. 3 is a method of generating sub-holograms for 3D display of large field holograms in accordance with the present invention.

Fig. 4 is a schematic diagram of a 3D holographic display with a large viewing area according to the present invention.

FIG. 5 is a method for generating a large-sized holographic 3D display hologram according to the present invention.

The reference numbers in the figures are as follows:

(1) a laser, (2) a beam splitter 1, (3) a beam splitter 2, (4) a mirror 1, (5) a shutter array, (6) a spatial filter array, (7) a solid lens, (8) a beam deflecting element 1, (9) a spatial light modulator, (10) a beam splitter 3, (11) a beam deflecting element 2, (12) a mirror 2, (13) a 3D object, (14) a3 mxn spatial light modulator, and (15) a hologram reconstruction image.

It should be understood that the above-described figures are merely schematic and are not drawn to scale.

Fifth, detailed description of the invention

The following describes an embodiment of a holographic 3D display system based on virtual array stitching of spatial light modulators in detail, and further describes the present invention. It should be noted that the following examples are only for illustrative purposes and should not be construed as limiting the scope of the present invention, and that the skilled person in the art may make modifications and adaptations of the present invention without departing from the scope of the present invention.

The relevant device parameters and structure parameters actually adopted by the system are as follows: the wavelength of the laser is 532 nm; the focal length of the solid lens is 300 mm; the beam splitter 1 and the beam splitter 2 have the size of 12.7mm × 12.7mm × 12.7mm, and the beam splitter 3 has the size of 25.4mm × 25.4mm × 25.4 mm; the shutter array consists of three shutters with the same type, and the light-emitting aperture of each shutter is 5 mm; the spatial light modulator has a pixel count of 1920 × 1080, a size of 12.29mm × 6.91mm, a pixel pitch of 6.4 μm, and a refresh rate of 60 Hz. The refractive index n of the refraction prism is 1.516, the wedge angle alpha is 4 degrees, and the deflection angle delta of the generated light beam is 2 degrees; the distance from the beam deflection element 1 to the spatial light modulator is 400 mm; the diffraction distance of the holographic reconstructed image was 200 mm.

In order to realize large-view holographic 3D display, a 'teapot' with the resolution of 320 x 240 is used as a recorded 3D object, a hologram with the resolution of 5760 x 1080 is generated by calculation through an angular spectrum algorithm, and is averagely divided into three sub-holograms with the resolution of 1920 x 1080 and then sequentially loaded on a spatial light modulator. At T₁Loading a first sub-hologram at moment, and controlling a shutter to enable a light beam I to pass through; at T₂At the moment, a second sub-hologram is loaded, and the shutter is controlled to let the light beam pass through, at T₃Loading a third sub-hologram at the moment, and simultaneously controlling a shutter to enable a light beam (c) to pass through; due to the persistence effect of human vision, the holographic reconstruction image of the 'teapot' with a large visual area can be seen. By calculation, when the viewing distance is 950mm, the size of the effective viewing zone is 234.4 mm. When the virtual array splicing of the spatial light modulator is not used, the size of the effective visual area is 25.5 mm. The effective visual area is enlarged by 9.2 times through virtual splicing.

To achieve large-size holographic 3D display, a "train" with a resolution of 2160 × 1080 is taken as a recorded 3D object, divided into three sub-pictures with a resolution 720 × 1080, and the focal length of the digital lens is set to be 500 mm. Three holograms with the resolution of 1920 multiplied by 1080 are obtained by calculation through an angular spectrum algorithm. At T₁At the moment, loading a first hologram, and controlling a shutter to enable a light beam (I) to pass through; at T₂At the moment, a second hologram is loaded, while the shutter is controlled to let the beam (T) pass through₃Loading a third hologram at the moment, and simultaneously controlling a shutter to enable a light beam (c) to pass through; the above process is repeatedly circulated. Due to the persistence effect of human eyes, the size of the holographic reconstruction image of the 'train' is 124.7mm, which is enlarged by 3 times compared with the size of the holographic reconstruction image of the 'train' when virtual splicing is not used.