Design And Analysis Of Miniature Diffractive Achromatic Lens Model

The lens is the core component of the imaging system.Currently,most lenses in imaging systems are based on the principle of geometric refraction.Therefore,in order to eliminate aberrations such as chromatic aberration,spherical aberration,coma,field curvature,astigmatism,and distortion,it is necessary to combine multiple lenses with different optical characteristics to eliminate these effects.Therefore,achromatic lenses based on the principle of geometric optics are usually large and bulky,so this lens cannot meet the development requirements of the current imaging system for optical,mechanical,electrical integration and miniaturization;nor can it meet the needs of new imaging systems.For example,the 3D integrated imaging system,which requires lenses such as the compound eyes of flies,is composed of small lens arrays with specific requirements.Therefore,new ideas are needed to design achromatic lenses.With the DOE(Diffraction Optical element),it has recently attracted great attention in the field of computational imaging.Designing a diffractive lens similar to the traditional flat fresnel lens may be a new direction.The surface of this kind of diffractive lens is fine concave and convex corresponding to the height of light wavelength,which can greatly reduce the size and weight of the imaging device.At present,the numerical calculation methods related to diffractive lenses can be roughly divided into two categories.One is to directly adopt the nearfield calculation method based on the vector diffraction theory;based on the consideration of the characteristic size of the lens in the range of the magnitude of the incident light or less than the wavelength of the incident light.The other is similar to the classic computer-generated hologram idea.According to the requirements of far-field design,based on scalar diffraction theory and the use of computational optimization,optical design is performed,and after the color image is obtained,the image is appropriately post-processed(For example,blind deconvolution method).At the same time,due to the development of various optimization algorithms and micronano processing technology,the micro-nano processing technology not only makes the diffraction lens have a smaller volume and weight,but also reduces the difficulty of manufacturing.This provides theoretical and technical support for the design of multiwavelength diffractive lenses.The main research content of the thesis is to study and discuss the feasibility of diffraction achromatic lens.The specific work is as follows:(1)Consider the design of the diffractive achromatic lens as an optimization design problem,construct the design objective function according to known conditions such as the incident member and the desired output light field,and use one or more optimization algorithms,To solve the diffraction structure closest to the idea.In order to achieve the ability to use this diffraction lens to image under various conditions of illumination.(2)The two classic optimization algorithms have been adaptively improved;one is an improved genetic algorithm,and the other is an improved binary search algorithm.Combining these two improved algorithms with scalar diffraction theory makes these two The improved algorithm can be used in the design of diffraction achromatic lens structures.(3)Using the resolution table as the test chart,test the designed structure under the conditions of single wavelength,discrete multi-wavelength,and continuous wavelength of visible light;and test the performance difference of the diffractive achromatic lens under the condition of different thickness of photoresist.