Design On The Directional Backlight Module Of Crosstalk Eliminated Glasses-free Three-dimensional (3D) Displayer

In recent years,with the rapid development of 3D technology,the method of realizing glasses-free 3D display becomes diversified.The glasses-free 3D display based on lenticular grating is widely researched due to the advantages of keeping the original resolution ratio of liquid crystal panel unchanged,not high matching requirements,omitting special processing for video images.But conventional directional backlight technology has the following shortcomings: great changes of viewing brightness in viewpoint area,large crosstalk in parallax images.In this paper,a new scheme of directional backlight glasses-free 3D display is proposed,which uses a butterfly-shaped light source array structure to produce the directional backlight transverse flat-top beam.It is used to solve the problems of the crosstalk and viewing brightness change in viewpoint area of directional backlight glasses-free 3D display.Firstly,the paper describes the design on the directional backlight module of crosstalk eliminated glasses-free 3D display.Directional backlight module by the uniform back light,LCD(Liquid Crystal Display)panel column and cylindrical lens array.In order to make the intensity distribution of the location of the view point uniformly,a structure of butterfly-shaped LCD panel has been proposed and used to design the module of the directional backlight glasses-free 3D display.By analyzing the causes of the appearance of crosstalk,according to the imaging optics principle of off-axis rays,the parameter calculating formula of the off-axis optical system which is consist of LCD panel of butterfly column unit and cylindrical lens.Then,the ray tracing TracePro software was used to simulate the designed backlight module.The simulation results show that,the directional backlight of the glasses-free 3D displayer can eliminate the crosstalk.The crosstalk of the glasses-free 3D display is less than 0.5% for the 90% viewing area of the view plane,the 10% peak width of the beam crosstalk area ratio is 0.The 90% peak width of the light beam is 1.37 times larger than that of the common liquid crystal cell structure,and the problem on the large fluctuations of image brightness in different location is improved.Secondly,the paper describes a scheme of using butterfly-shaped hole mask butterfly unit instead of LCD panel column structure,to minimize the structural complexity of LCD butterfly unit.Based on the generalized Huygens-Fresnel diffraction integral and multiple wavelength superposition principle,we deduce the diffraction field distribution formula of beam passing through cylindrical lens with the butterfly liquid crystal switch unit as the light source.Placing the butterfly liquid crystal switch unit on the cube focal plane of the cylindrical lens,we simulate transverse optical field energy distribution under cylindrical lens with different focal lengths and different transmission distance,and analyzes the butterfly-shaped parameter(the ratio of height to length in butterfly-shaped center)of transversal intensity distributions flattened factor F.Results show that when the width of butterfly-shaped light source unit is 0.05 mm,the range in 4~12 mm focal length f cylindrical lens output beam transverse flat characteristics;Transmission distance of 500~2000 mm flat factor within the scope of basic remains unchanged;Butterfly parameter affecting F is larger,the smaller the beta,transverse diffraction light field at the center of the light intensity is smaller,as the beta decreases,and transverse diffraction light field F first increases then decreases,and beta = 0.4~0.6 between maximum.At the end of the paper,the experimental devices and the experimental results of the horizontal flat-top beam generated by the butterfly-shaped light source array in the directional backlight module are described.We use plane white LED light sources,the butterfly-shaped aperture array diffraction mask plate and the cylindrical lens array as the experimental device to test and verify the relationship between the transverse light intensity distribution and the distance and the influence of the pinhole butterfly-shaped parameters on the transverse light intensity distribution.It is shown that the white light flat-topped beams of can be obtained when the concavity of butterfly-shaped holes change among 0.5-0.66.The width of the horizontal flat-topped beam increases with the increasing of transmission distance,moreover,the flat top factor is almost unchanged.It is also found that the refractive and dispersive dispersion of the cylindrical lens can cancel out each other,so that the horizontal flat-toped white beams is basically dispersionless.