Research On Diffractive Optical Element Applied To Direct Laser Backlight

In recent years,as the mainstream flat panel display technology,liquid crystal display(LCD)technology has attracted the attention of people from all walks of life.However,with the continuous advancement of technology,the traditional light-emitting diode-based backlight module has been unable to meet people's demand on high color gamut.Compared with traditional light sources,lasers can provide light with narrow spectrum and high color purity,which can significantly improve the color performance of a LCD when applied to a backlight module.Diffractive optical element(DOE)has the advantages of small size,light weight,high diffraction efficiency,and high dispersion performance.It is different from traditional optical elements that can achieve miniaturization,arraying,and integration of optical systems.It has a very wide range of applications in the field of beam shaping and wavefront transformation.In this paper,DOE is used as a laser shaping element,which can expand the input laser spot and shape it to form a uniform surface light source.In order to further improve the performance of a laser backlight module based on DOE,this paper makes the deep studies on some common problems caused by DOE processing,inclduing:1.Normally,when fabricating DOE,it is necessary to binarize its continuous phase data.The binarized phase data obtained by the existing algorithm tends to have poor performance.The numerical optimization algorithm including the simulated annealing and the regional iterative binarization optimization algorithm based on error diffusion are used to improve the optical performance of a binarized DOE.Computer simulation results and actual optical reconstruction results show the effectiveness of the proposed algorithm.2.Aiming at the problem that the DOE with large pitches can not precisely regulate the input light field,the paper firstly re-establishes the simulation model and then analyzes the cause of the error.Combining the algorithm,some improvement suggestions are introduced.Both the simulation and experiment results prove that the proposed algorithm can effectively improve the optical quality of the output light field.3.The paper analyzes DOE phase and output light field errors caused byinsufficient steepness.By establishing an accurate model for simulating the shape of a DOE after processing,the corresponding optimization algorithms are proposed to effectively improve DOE optical performance.