Theoretical Analysis And Numerical Simulation Of Dual-band Grating Color Separation Imaging System

The color separate imaging has been drawing more attentions due to its good color reproduction and detail resolution, which can be used for imaging, display, spectral analysis and other fields. But there are still many problems on the existing products. looking for a reasonable separation structure and improve energy efficiency is the main issues to be resolved of this project.Photographic color separation imaging used on the cameras and other products has some technical about the wide spectrum (400nm-700nm) and wide angle spatial separation of light, which can receive a three-channel(RGB) non-interference images, while increasing the image resolution as much as possible. Based on the diffraction grating principle, this paper propose the phase grating to separate spatial colors, and analyze the feasibility of using the phase grating in photographic equipment. The present method provides a theoretical basis of improving the multi-CCD imaging device and restore spatial resolution.The main objective of the project is the spatial separation of wide-angle wide spectrum incident light. Existing separation methods using diffraction grating generally discuss the wave field based on the parallel incident light conditions, to the case of non-parallel incident light there is a little discussion. To simplify the theoretical model, this paper firstly derived a dual wavelength and wide-angle incident angle wave field function. Then an analysis the amount of wave field broadening and offset is present, and the corresponding compensation methods is calculate as well. Finally, this paper analyze grating parameters and diffraction efficiency based on the incidence of dual-band wide-angle light.Based on the Fresnel diffraction theory and the angular spectrum theory and combined with fractional Talbot effect theory, the paper derived the dual-wavelength and wide-angle incident light wave field distribution function diffracted by a step phase grating, and calculated the amount of wide-angle incident wave field’s broadening and offset compared with the parallel incident light condition. By adjusting the width of grating steps, the new grating parameters can achieve a good spatial separation of dual-wavelength wide-angle incident light. The diffraction efficiency of image plane is calculated, and we change parts of the grating structure(increasing grating steps numbers) to maintain receiving light intensity coincident.The dual-band (red and blue wavelength band) factor is added to the incident condition to calculated dual-band wide-angle incident wave field distribution, which has gained the corresponding relevance between the wide-band incident and the wave field distribution. By changing the phase grating shape, each one band can focus on the image plane with one pixel horizontal distance gap to another band. Grating step height and other parameters has further optimized to ensure the light intensity between adjacent pixels of a single band, which can result a clear dual-color separation image. The result provide a miniaturize and process feasibility solution for various types of color separation applications with wide-angle and wide wavelength band incident conditions.