CN111176094B - Laser holographic projection display method and device - Google Patents
Laser holographic projection display method and device Download PDFInfo
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- CN111176094B CN111176094B CN202010037679.7A CN202010037679A CN111176094B CN 111176094 B CN111176094 B CN 111176094B CN 202010037679 A CN202010037679 A CN 202010037679A CN 111176094 B CN111176094 B CN 111176094B
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- 238000000034 method Methods 0.000 title claims abstract description 23
- 238000005070 sampling Methods 0.000 claims description 4
- 239000004973 liquid crystal related substance Substances 0.000 claims description 2
- 230000009466 transformation Effects 0.000 claims 1
- 230000000694 effects Effects 0.000 abstract description 3
- 238000005516 engineering process Methods 0.000 abstract description 2
- 230000002688 persistence Effects 0.000 abstract description 2
- 230000000007 visual effect Effects 0.000 abstract description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 238000001093 holography Methods 0.000 description 1
- 238000005286 illumination Methods 0.000 description 1
- 230000002452 interceptive effect Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
- G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
- G03H1/22—Processes or apparatus for obtaining an optical image from holograms
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
- G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
- G03H1/0005—Adaptation of holography to specific applications
- G03H2001/0088—Adaptation of holography to specific applications for video-holography, i.e. integrating hologram acquisition, transmission and display
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Abstract
The invention discloses a laser holographic projection display method, and belongs to the technical field of holographic projection. The speckle problem in the laser holographic projection display technology is solved. The method comprises the following steps: (a) decomposing an image to be displayed into at least 2 sparse two-dimensional sub-images; (b) calculating a sub-hologram corresponding to each two-dimensional sub-image; (c) and projecting the laser onto a spatial light modulator, sequentially loading the sub-holograms corresponding to each two-dimensional sub-image by the spatial light modulator, and projecting the light beams modulated by each sub-hologram to the holographic display medium to form a projected image on the holographic display medium. According to the invention, the image to be displayed is decomposed into sparse subimages, so that no interference is generated between pixel points in each subimage, and therefore, no speckle is generated during the display of the subimages. The sub-images are displayed in time series, and a complete image without speckles is synthesized by using the effect of human visual persistence.
Description
Technical Field
The invention relates to the technical field of holographic projection, in particular to a laser holographic projection display method and device.
Background
The holography technique is a three-dimensional display technique which records all information (including amplitude and phase) of a light wave field from an object by a hologram, and after an illumination light is diffracted on the hologram, the light wave field of the object recorded by the hologram can be restored. Since the restored light wave field is identical to the light wave field when the human eye observes a real object, the observer can see a three-dimensional stereoscopic image of the object. The implementation of holographic techniques relies on the coherence of the light, suitable for the use of laser light sources, and laser holographic projection techniques are considered as the best choice for future three-dimensional display techniques.
In recent years, computer holograms (CGH) have been developed rapidly, and holograms have been acquired without the need of a conventional optical recording process, but instead, they are calculated by a process of simulating propagation of light waves by a computer based on three-dimensional data of virtual objects, so that generation of holograms is simpler and faster. The virtual object mostly adopts a discretized point cloud model, namely a set of a series of spatial sampling points, and the calculation of the hologram can be determined through Fourier transform or Fresnel transform. However, like other laser projection display techniques, computer hologram based display techniques also suffer from the problem of speckle, i.e. the presence of randomly distributed bright eye spots in the reconstructed image. The existence of speckle can reduce the definition of a projected image and seriously affect the display effect of the image.
Disclosure of Invention
The invention provides a laser holographic projection display method for dissipating spots, aiming at solving the problem of speckles in the laser holographic projection display technology.
In order to achieve the purpose, the invention adopts the following technical scheme:
a laser holographic projection display method comprises the following steps:
(a) decomposing an image to be displayed into at least 2 sparse two-dimensional sub-images;
(b) calculating a sub-hologram corresponding to each two-dimensional sub-image;
(c) and projecting the laser onto a spatial light modulator, sequentially loading the sub-holograms corresponding to each two-dimensional sub-image by the spatial light modulator, and projecting the light beams modulated by each sub-hologram to the holographic display medium to form a projected image on the holographic display medium.
The further technical scheme is as follows: the two-dimensional sub-images are generated by spatially sampling the image to be displayed, the pixel intervals of the two-dimensional sub-images in two orthogonal directions are integral multiples of the pixel interval of the image to be displayed, and the two-dimensional sub-images are staggered with each other.
The further technical scheme is as follows: the pixel spacing of the two-dimensional sub-image is determined by the minimum spacing between adjacent pixel points in the sub-image without interference.
The further technical scheme is as follows: the hologram is calculated from the fresnel transform of the two-dimensional sub-images.
The further technical scheme is as follows: the hologram is calculated from a fourier transform of the two-dimensional sub-images.
The invention also provides a laser holographic projection display device, which is used for projection display of an image to be displayed by the laser holographic projection display method, and comprises the following steps: the device comprises a light source, a collimating lens, a microprocessor, a spatial light modulator and a holographic display medium;
the light source is used for generating laser;
the collimating lens is used for collimating and projecting laser onto the spatial light modulator;
the microprocessor is used for decomposing an image to be displayed into at least 2 two-dimensional sub-images and calculating the hologram of the two-dimensional sub-images;
the spatial light modulator is used for loading the hologram of the two-dimensional sub-image, modulating the laser from the collimating lens and then projecting the laser to a holographic display medium to form a projection image.
The further technical scheme is as follows: further comprising a 4F system disposed between the spatial light modulator and the holographic display medium for projecting light from the spatial light modulator to the holographic display medium.
The further technical scheme is as follows: the 4F system includes a spatial filter on the Fourier plane to block light other than the first order diffracted light from being projected onto the holographic display medium.
The further technical scheme is as follows: the spatial light modulator is a liquid crystal spatial light modulator.
The further technical scheme is as follows: the spatial light modulator is a digital micromirror array.
Compared with the prior art, the invention has the beneficial effects that:
the image to be displayed is decomposed into sparse subimages, so that no interference is generated between pixel points in each subimage, and the display of the subimages does not generate speckles. The sub-images are displayed in time series, and a complete image without speckles is synthesized by using the effect of human visual persistence.
Drawings
FIG. 1 is a laser holographic projection display method in an embodiment of the present invention;
FIG. 2 is a diagram illustrating an embodiment of the present invention in which an image to be displayed is decomposed into sub-images having the same pixel spacing in two orthogonal directions;
FIG. 3 is a diagram illustrating an embodiment of the present invention in which an image to be displayed is decomposed into sub-images having different pixel intervals in two orthogonal directions
Fig. 4 is a laser hologram projection display device in an embodiment of the present invention.
Detailed Description
The present invention will be further described with reference to the following examples, which are intended to illustrate only some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, other embodiments used by those skilled in the art without any creative effort belong to the protection scope of the present invention.
Example 1
As shown in fig. 1, a laser holographic projection display method includes the following steps:
(a) decomposing an image to be displayed into at least 2 sparse two-dimensional sub-images;
the two-dimensional sub-images are generated by spatially sampling the image to be displayed, the pixel intervals of the two-dimensional sub-images in two orthogonal directions are integral multiples of the pixel interval of the image to be displayed, and the two-dimensional sub-images are mutually staggered.
Specifically, in the present embodiment, the image to be displayed is selected as a two-dimensional image, and the pixel interval of the decomposed two-dimensional sub-image is 2 times the pixel interval of the image to be displayed in both orthogonal directions. The decomposition method of the image to be displayed is shown in fig. 2, where 10 is the image to be displayed, 101-104 are 4 sub-images obtained by decomposition, a solid black circle in the sub-image represents a pixel point sampled from the image to be displayed, and a hollow circle represents that the pixel is 0. And the sub-images are mutually staggered and superposed to obtain the original image to be displayed.
Of course, the pixel intervals of the sub-images may be different in the two orthogonal directions, as shown in fig. 3 in the case where the pixel intervals of the sub-images 1001 and 1006 are 2 times and 3 times as large as the image to be displayed 10 in the lateral and longitudinal directions.
In addition, when the image 10 to be displayed is a three-dimensional image, the image should be divided into a plurality of two-dimensional images, and then each two-dimensional image should be decomposed into sub-images.
The pixel spacing of a two-dimensional sub-image is determined by the minimum spacing between adjacent pixel points within the sub-image that does not interfere. Due to diffraction, pixels form Airy spots on the holographic display medium, and in order to prevent adjacent pixels from interfering, the pixel interval should be larger than the diameter of the diffracted Airy spots. In particular implementations, the airy disk size, and thus the minimum value of the pixel spacing, can be determined through testing.
(b) Calculating a sub-hologram corresponding to each two-dimensional sub-image;
in particular, the hologram may be calculated from a fourier transform or fresnel transform of the two-dimensional sub-images.
(c) And projecting the laser onto a spatial light modulator, sequentially loading the sub-holograms corresponding to each two-dimensional sub-image by the spatial light modulator, and projecting the light beams modulated by each sub-hologram to the holographic display medium to form a projected image on the holographic display medium.
According to another aspect of the embodiments of the present invention, there is also provided a laser holographic projection display device, as shown in fig. 4, laser light emitted from a light source 1 passes through a collimating lens 2 to become a collimated beam, and is projected onto a spatial light modulator 4. The microprocessor 3 is used for decomposing the image to be displayed into sub-images according to the method and calculating the corresponding sub-holograms. The sub-holograms loaded on the spatial light modulator modulate the light beam, and the diffracted light is transformed by the 4F system 5 to form a projected image on the holographic display medium 6.
Specifically, the laser in the present invention may employ a laser diode, for example, a blue laser diode having a center wavelength of 465 nm. The spatial light modulator may employ a digital micromirror array (DMD) with an image resolution of 1920 x 1080. The 4F system consists of two lenses with the same focal length, e.g. 50 mm. The holographic display medium may be a holographic film with a glass substrate.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (7)
1. A laser holographic projection display device, characterized by: the method comprises the following steps: the device comprises a light source, a collimating lens, a microprocessor, a spatial light modulator and a holographic display medium;
the light source is used for generating laser;
the collimating lens is used for collimating and projecting laser onto the spatial light modulator;
the microprocessor is used for decomposing an image to be displayed into at least 2 two-dimensional sub-images and calculating the hologram of the two-dimensional sub-images;
the spatial light modulator is used for loading the hologram of the two-dimensional sub-image, modulating the laser from the collimating lens and then projecting the laser to a holographic display medium to form a projection image;
the laser holographic projection display method realized by the laser holographic projection display device comprises the following steps:
(a) decomposing an image to be displayed into at least 2 sparse two-dimensional sub-images; the two-dimensional sub-images are generated by spatially sampling an image to be displayed, the pixel intervals of the two-dimensional sub-images in two orthogonal directions are integral multiples of the pixel interval of the image to be displayed, and the two-dimensional sub-images are mutually staggered; the pixel spacing of the two-dimensional sub-images may be different in two orthogonal directions; the pixel interval of the two-dimensional sub-image is determined by the minimum interval without interference between adjacent pixel points in the sub-image;
(b) calculating a sub-hologram corresponding to each two-dimensional sub-image;
(c) and projecting the laser onto a spatial light modulator, sequentially loading the sub-holograms corresponding to each two-dimensional sub-image by the spatial light modulator, and projecting the light beams modulated by each sub-hologram to the holographic display medium to form a projected image on the holographic display medium.
2. Laser holographic projection display of claim 1, wherein said hologram is calculated from a fresnel transformation of said two-dimensional sub-images.
3. Laser holographic projection display of claim 1, wherein said hologram is calculated from a fourier transform of said two-dimensional sub-image.
4. The laser holographic projection display of claim 1, further comprising a 4F system disposed between the spatial light modulator and the holographic display medium for projecting light from the spatial light modulator to the holographic display medium.
5. The laser holographic projection display of claim 4, wherein the 4F system comprises a spatial filter on a Fourier plane to block light other than first order diffracted light from being projected onto the holographic display medium.
6. Laser holographic projection display of claim 1, wherein said spatial light modulator is a liquid crystal spatial light modulator.
7. A laser holographic projection display of claim 1, wherein said spatial light modulator is a digital micro-mirror array.
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| GB2604119B (en) * | 2021-02-24 | 2023-10-11 | Envisics Ltd | Holographic projection |
| CN116009374B (en) * | 2023-03-23 | 2023-06-13 | 北京深光科技有限公司 | Laser-based three-dimensional holographic imaging method, three-dimensional holographic imaging device and equipment |
| CN117572632B (en) * | 2024-01-17 | 2024-04-02 | 中国科学院长春光学精密机械与物理研究所 | Discrete modulation method and system suitable for pyramid wavefront sensor |
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| DE102006062376A1 (en) * | 2006-12-19 | 2008-06-26 | Seereal Technologies S.A. | Method and apparatus for reducing speckle |
| CN101622568A (en) * | 2007-03-02 | 2010-01-06 | 朗讯科技公司 | Speckle reduction in laser-projector images |
| CN106227016A (en) * | 2016-07-28 | 2016-12-14 | 东南大学 | A kind of non-iterative complex amplitude modulation holographic projection methods |
| WO2017114789A2 (en) * | 2015-12-28 | 2017-07-06 | Seereal Technologies S.A. | Display device and method for optimizing the image quality |
| CN108287414A (en) * | 2017-12-28 | 2018-07-17 | 上海慧希电子科技有限公司 | Method for displaying image and its storage medium and system |
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| CN209400843U (en) * | 2019-03-12 | 2019-09-17 | 深圳大学 | A kind of holographic projector |
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|---|---|---|---|---|
| DE102006062376A1 (en) * | 2006-12-19 | 2008-06-26 | Seereal Technologies S.A. | Method and apparatus for reducing speckle |
| CN101622568A (en) * | 2007-03-02 | 2010-01-06 | 朗讯科技公司 | Speckle reduction in laser-projector images |
| WO2017114789A2 (en) * | 2015-12-28 | 2017-07-06 | Seereal Technologies S.A. | Display device and method for optimizing the image quality |
| CN106227016A (en) * | 2016-07-28 | 2016-12-14 | 东南大学 | A kind of non-iterative complex amplitude modulation holographic projection methods |
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