Colorful holographic display transverse chromatic aberration compensation method

Abstract

The invention discloses a compensation method for transverse chromatic aberration in color holographic display, and belongs to the technical field of holographic display. The method comprises the following steps: respectively extracting information of three scenes of red, green and blue in a color target image, and carrying out zoom compensation of chromatic aberration of magnification on the information of each channel; respectively calculating sub-holograms under the three channels by adopting an iterative algorithm; any color channel is selected as a reference wavelength, and the transverse chromatic aberration angle compensation amount required by the other two non-reference channels is calculated according to the difference among the red, green and blue wavelengths; the sub-holograms are loaded on the spatial light modulator, and on the basis of time division multiplexing, the transverse chromatic aberration of color holographic display is compensated by adjusting the incident angles of the two non-standard lasers irradiating on the spatial light modulator. The method is efficient, calculation is convenient and fast, compensation errors generated by a traditional method are effectively eliminated through accurate angle compensation, and the method has the advantages of being simple, low in cost, high in reproduction result quality and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of color holographic display, and particularly relates to a compensation method for lateral chromatic aberration of color holographic display. BACKGROUND

[0002] Since the birth of holography, with the continuous development of micro-nano optics and display technology, holographic display technology occupies an important position in the display field due to its unique advantages. Nowadays, single-color display cannot meet the demand, and more complex color holographic display is needed. In the process of color holographic display, the conventional method is to continuously adjust the reconstructed images corresponding to the red, green and blue channels at the target space position, and accurately superimpose them to produce a complete color display result. However, different wavelengths have different refractive indices for optical elements, and the positions and sizes of the reconstructed images of red, green and blue light will be different when they pass through these devices, resulting in magnification chromatic aberration, axial chromatic aberration and lateral chromatic aberration. These chromatic aberrations affect the quality of the color holographic display result.

[0003] Magnification chromatic aberration and axial chromatic aberration have solutions, but lateral chromatic aberration is difficult to solve. For example, the document with the patent announcement number "CN107024849B" discloses a "color computer holographic stray light elimination system and method based on digital lens", which uses a digital lens instead of a Fourier lens, compensates for the magnification chromatic aberration and axial chromatic aberration caused by the difference in wavelength of the red, green and blue three components in color reconstruction by setting the focal length of the digital lens, and then filters through a light barrier to achieve color chromatic aberration compensation and stray light elimination for color computer holographic reconstruction. The lateral chromatic aberration has not been effectively solved.

[0004] Lateral chromatic aberration is usually solved by using an inclined grating, for example, the document with the patent publication number "CN104614868A" discloses a "system and method based on holographic grating achromatism", but the period of the grating must match the period of the hologram, resulting in approximation error and rounding error in the calculation process, and there are problems of low quality and large error of the color holographic display result. SUMMARY

[0005] The present application provides a compensation method for lateral chromatic aberration in color holographic display to solve the technical problems of low quality and large error of the color holographic display result in the prior art.

[0006] In order to achieve the above purpose, the technical scheme provided by the present application is: a compensation method for lateral chromatic aberration in color holographic display, comprising the following steps: Step one, extracting red, green and blue three-color component information in the target image, and calculating a scaling ratio according to the difference between different wavelengths; Step two, the three-channel target information after the scaling compensation of the magnification chromatic aberration is calculated by an iterative algorithm to obtain the corresponding sub-hologram of red, green and blue three components; Step three, taking the reconstructed image of any one color component as a reference, the center positions of the reconstructed images of the other two color components are moved respectively to obtain the compensation angle deviation value; Step four, based on the time division multiplexing holographic display method, the sub-hologram obtained in step two is loaded on the spatial light modulator, and based on the compensation angle deviation value obtained in step three, the incident angles of red, green and blue three colors on the spatial light modulator are adjusted through the half-transmission half-reflection mirror to obtain a colorless and high-quality color holographic display result.

[0007] Further, the scaling ratio in the above step one is shown as formula 1 (1) Wherein, are the wavelengths corresponding to red, green and blue respectively.

[0008] Further, in the above step three, the angle offset required for compensating the lateral chromatic aberration of the remaining two non-reference channels is calculated according to formula (2) (2) In the formula, is the pixel size of the SLM, are the wavelengths corresponding to red, green and blue respectively, and arctan is the inverse tangent function.

[0009] Compared with the prior art, the present application has the following advantages: (1) The present application does not need to perform superposition optimization in the process of designing hologram, and only needs to control the incident angles of different light sources in the holographic display device to compensate the lateral chromatic aberration. The compensation value of the incident angle is derived from the offset between the lateral positions of the red, green and blue reconstructed images, that is, the difference between the diffraction angles corresponding to different wavelengths under the diffraction theory. The present application is simple, efficient, convenient and fast to calculate, and can effectively compensate the position deviation of the reconstructed image caused by the difference between different wavelength light sources in color holographic display.

[0010] (2) The compensation scheme of the present application avoids the approximation error and rounding error caused by the traditional tilted grating compensation method, and can provide high-quality color holographic display results with high precision.

[0011] (3) The performance requirements of the display device are reduced, which can effectively reduce the investment cost of the equipment. The reproduction result is high in quality under the conditions of simple implementation and low cost. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1is a flow chart of the method adopted by the present application; Figure 2 is a schematic diagram of a display device using the method adopted by the present application; Figure 3 is a color target image in red, green, blue three component separation and magnification chromatic aberration zoom compensation. DETAILED DESCRIPTION

[0013] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further specifically described below through examples and drawings.

[0014] Referring to Figure 1 A compensation method for lateral chromatic aberration in color holographic display, specifically comprising the following steps: Step one, extract the red, green, blue three color component information in the target image, calculate the zoom ratio according to the difference between different wavelengths, take any one color component as the reference, adjust the size of the other two color component target images by proportion, so as to zoom compensate the magnification chromatic aberration, the zoom ratio is shown in formula 1.

[0015] (1) Among them: are the wavelengths corresponding to red, green and blue respectively.

[0016] Step two, calculate the corresponding sub-hologram under the red, green and blue three components by using the traditional GS iterative algorithm for the three-channel target information of the zoom compensated magnification chromatic aberration.

[0017] Step three, take the reconstructed image of any one color component as the reference, respectively move the center position of the reconstructed image of the other two color components, and obtain the angle deviation value to be compensated: In this embodiment, taking the reconstructed image of the blue component as the reference, the angle deviation value to be compensated for the lateral chromatic aberration of the other two non-reference channels is calculated according to formula (2) (2) In the formula, is the pixel size of SLM, are the wavelengths corresponding to red, green and blue respectively, and arctan is the inverse tangent function.

[0018] Step four, based on the time division multiplexing holographic display scheme, load the sub-hologram obtained in step two on the spatial light modulator, adjust the incident angle of red, green and blue three colors on the spatial light modulator through the half-transmission half-reflection mirror based on the compensation angle deviation value obtained in step three, and the reconstructed images of red, green and blue three components on the receiving screen are completely coincided, so that the color holographic display result without chromatic aberration and high quality can be obtained.

[0019] See Figure 2 The system shown consists of three light sources (red, green, and blue), two semi-transparent mirrors, a spatial light modulator, and a receiving screen. The three lasers (red, green, and blue) illuminate the spatial light modulator at different incident angles after passing through the two semi-transparent mirrors, and finally, a color holographic display result is obtained at the receiving screen. Based on the time-division multiplexing holographic display method, the generated sub-hologram is loaded onto the spatial light modulator using a computer.

[0020] See Figure 3 In an example of this invention, a 768×768 color target image "Magic Cube" is used, with red, green, and blue wavelengths respectively. =650nm =520nm =450nm; First, using the blue component as the reference, and the red and green components as non-reference quantities, the red, green, and blue components are extracted from the color target image. The scaling ratio is calculated according to Equation 1. =0.692:0.8:1. After scaling compensation for magnification color difference, three sub-holograms were obtained through iterative optimization calculation. The pixel size d of the spatial light modulator used was 12.5μm. Using the blue channel as the reference, the angles corresponding to the non-reference quantities red and green were calculated according to Equation 2. =0.458°, =0.160°; Red, green, and blue lasers generate parallel light, which, through an adjustable optical path composed of two semi-transparent and semi-reflective mirrors, illuminates the spatial light modulator at different incident angles. The spatial light modulator is a transmissive type with 1024×768 pixels and a reconstruction distance of 700mm. By adjusting the incident angles of the red and green lasers, the reconstructed images corresponding to the red, green, and blue components are made to completely overlap, resulting in a color holographic display effect with no color difference and high quality.

[0021] This embodiment is a description of specific implementations of the present invention, and not a limitation thereof. Those skilled in the art can make corresponding equivalent technical solutions without departing from the scope of the present invention; therefore, all equivalent technical solutions should be included within the protection scope of the present invention.

Claims

1. A method for compensating lateral color difference in a color holographic display, characterized in that: Includes the following steps: Step 1: Extract the red, green, and blue color components from the target image and calculate the scaling ratio based on the differences between different wavelengths; Step 2: Using an iterative algorithm, calculate the sub-holograms corresponding to the red, green, and blue components of the three-channel target information after magnification and color difference scaling compensation. Step 3: Using the reconstructed image of any one color component as a reference, move the center positions of the reconstructed images of the other two color components respectively to obtain the compensation angle deviation value. Step 4: Based on the time-division multiplexing holographic display method, the sub-hologram obtained in Step 2 is loaded onto the spatial light modulator. Based on the compensation angle deviation value obtained in Step 3, the incident angles of red, green and blue on the spatial light modulator are adjusted by a semi-transparent and semi-reflective mirror to obtain a color holographic display result with no color difference and high quality.

2. The method for compensating for lateral color difference in a color holographic display according to claim 1, characterized in that: The scaling ratio in step one is shown in Equation 1. （1） in: These represent the wavelengths corresponding to red, green, and blue, respectively.

3. The method for compensating for lateral color difference in a color holographic display according to claim 1, characterized in that: In step three, the angular offset of the lateral color difference to be compensated for the other two non-reference channels is calculated according to equation (2). θ （2） In the formula, d is the pixel size of the SLM. These represent the wavelengths corresponding to red, green, and blue, respectively, and arctan is the arctangent function.

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