A Research Of Imaging With Liquid Crystal Microlens Array

Liquid crystal lens is a new type of gradient index lens,which can realize functions such as electronically controlled lens and optical axis movement.Liquid crystal lenses can be divided into large-aperture liquid crystal lenses and small-aperture liquid crystal microlenses according to the size of the aperture.The aperture size of the large-aperture liquid crystal lens is at the millimeter level,and the aperture size of the liquid crystal microlens is at the micron level or below.As a research hotspot,large-aperture liquid crystal lenses have been widely used in many imaging fields.However,due to their own characteristics,they usually cannot be used alone.Instead,they appear as a lens group in combination with traditional lenses to undertake the core focusing task.The liquid crystal microlens usually appears in the form of an array due to its small aperture,and,compared with the large aperture liquid crystal lens,its optical power is larger due to its small aperture,and its optical deflection ability is strong,so it can be used in the optical system to undertake the task of independent imaging.This thesis mainly studies the application of liquid crystal microlens array in imaging,and proposes two kinds of liquid crystal microlens arrays with different electrode structures,and then proposes a set of liquid crystal microlens array direct imaging system,and uses the Electronically controlled focusing and large optical power characteristics present an achromatic approach.The main research content of this thesis is:First,the structure and working principle of the liquid crystal microlens array are studied,and the relationship between the small aperture and the large optical power of the liquid crystal microlens array is explained from the theoretical formula of the optical power of the liquid crystal lens.From the perspective of electrode pattern design,the electrode structures of the three-layer electrode structure liquid crystal microlens array and the new liquid crystal microlens array are introduced respectively.The optical characteristics including wavefront and optical power of the two are tested,and the test results show that the wavefront of the liquid crystal microlens array has a phase distribution similar to a parabola,and has the characteristics of large optical power.Second,the chromatic aberration characteristics of liquid crystal microlens arrays are studied.First,the dispersion characteristics of liquid crystals are explained,and the Cauchy expansion formula of liquid crystals with normal dispersion characteristics is given,and the optical power of liquid crystal microlens arrays is deduced theoretically.The formula for the change of degree with wavelength.Then the optical power variation curves of the two liquid crystal microlens arrays in three different wavelength bands were tested,and the test results showed that the optical power decreased with the increase of the wavelength under the same voltage.Finally,a positional chromatic aberration correction method based on liquid crystal microlens array is proposed.Third,the imaging characteristics of the liquid crystal microlens array are studied,and a simple direct imaging system of the liquid crystal microlens array is built.Each unit microlens images different areas of the object,reduces crosstalk between adjacent microlenses through near-parallel light illumination,and stitches all unit images to obtain a complete image.The system requires no additional optics and has a simple and compact structure.The liquid crystal microlens array has a large field of view,and the imaging area is scalable,which provides a new idea for simple microscopic imaging under a large field of view.Using the electronically controlled focusing characteristics of the liquid crystal microlens array to eliminate the positional chromatic aberration of the system,the focused images were collected under the three color channels,and then the channels were merged and the images were stitched.The results show that the image quality has been improved to a certain extent,which provides a new idea for eliminating positional chromatic aberration.