Research On Exit Pupil Brightness Uniformity Of Holographic Optical Waveguide Display Module

In recent years,the field of near-eye display has been developing.Augmented reality display devices capable of superimposing virtual information in the real environment have gradually become a hot research topic for more and more experts and scholars.In order to meet most consumers higher demands for small size and light weight of head-mounted display devices,optical module for augmented reality display based on holographic optical waveguide technology have been rapidly developed.This set of optical module combines holographic gratings with transparent waveguide materials,which can realize the function of augmented reality displaying while reducing the total number of optical elements and effectively reducing the size and weight of the integral device.However,most augmented reality products using holographic optical waveguide technology are based on high-precision nano lithography technology to make holographic gratings,while the method of making holographic grating by means of experimental exposure is not common.In addition,due to the characteristics of optical waveguide display method,the brightness uniformity of the transmission image decreases transparently after exiting from the expanded exit pupil portion.At present,the solution to this problem is to optimize the diffraction efficiency of the coupling grating so as to change the light intensity distribution of the outgoing light.However,due to the complexity of the experimental process,the research results in many academic article papers only stay at the software simulation stage and do not actually produce holographic gratings that meet the conditions.To solve the above problems,a holographic optical waveguide display module based on augmented reality equipment is designed and fabricated in this article.The module can not only expand the exit pupil in one-dimensional direction,but also improve the display quality of the output image and increase the exit pupil brightness uniformity to 57.14%.In terms of the structural design of the display module,based on the holographic optical principle and the display principle of the holographic optical waveguide system,a structural design scheme of a holographic optical waveguide display module including a coupled grating,a waveguide material and a coupled grating is proposed.In terms of the production scheme of the display module,firstly,the relationship between the diffraction efficiency and the exposure amount of the CH-RD silver-salt red plate is obtained through the exposure experiment,which provides a basis for the design of the display module exposure scheme.Then,based on the structural design scheme and the diffraction efficiency law curve,the exposure schemes of the control group and the experimental group were formulated,and the problems such as the appropriate construction method of the light path and the angle of light incidence were determined.Finally,according to the experimental scheme,the coupled grating and the coupled grating were recorded on the same silver salt dry plate material by exposure method,and a holographic optical waveguide display module was fabricated.Finally,the performance test and parameter analysis of the manufactured holographic optical waveguide display module were carried out.The experimental results show that the manufacturing scheme proposed in this paper can improve the exit pupil brightness uniformity of the holographic optical waveguide display module to 57.14%,achieving the expected research objectives.