Optical Touch Screen Based On Grating Waveguides

Novel portable electronic products,such as wearable devices,smart phones and tablets which have brought great convenience to mankind in various fields are developing rapidly in recent years.Within the products,touch technology as a kind of interaction with display systems is playing a more and more significant role.The judgment of touch technology is often connected with people's experience and the steps that pursing high efficiency,light weight and low power consumption will never be stopped.However,for the current dominating touch technology,whether resistive touch screen or capacitive touch screen has some shortcomings.Optical touch technology with high stability,high transmittance and large size operation is attracting more and more attentions of domestic and foreign researchers.In this paper,by taking the advantages of grating waveguide's coupling property and flat waveguide's touch method,we discover a new kind optical touch technology suitable for remote sensing.Dielectric grating waveguides are incorporated to realize an optical touch panel device.A green laser pointer is applied as the touch source,and the green light illuminating on the surface of gratings introduces an increase of the optical signal propagating in the planar waveguide.Characteristics of the transparent touch panel are investigated in simulation and experiment.The proposed device,featured with compact structure,transparency and remote sensing,affords a new method of 3-D interaction with multimedia.The main research works are listed as below:The first part is the theoretical background of grating waveguide including the parameters of gratings,Bragg phase matching conditions or grating equation,and the use of wave vector diagram.We emphasized on the introduction of Finite Difference Time Domain(FDTD)and Rigorous Couple Wave Analysis(RCWA)which is important for the next simulation.Secondly,we talked about the affection of grating period and incident angle of touch source with coupling property.The affection can divide the coupling state into four types: free space coupling,substrate coupling,guide modes coupling and none coupling.The thickness of waveguide was also studied by the equation of guided modes.Thirdly,based on the coupled light's characteristics,circuit driver system of the touch screen was designed including optical signal detection,signal amplification,signal processing and controller design.Finally,the samples of touch screen were fabricated using laser interference with measured spectra matching to the simulations.Furthermore,we combined the touch screen and circuit driver system to test the function of optical touch screen based on grating waveguide.It was revealed that the new touch technology could support both single point and multipoint touch.The response time in microseconds was also investigated.