Research On The Thickness Measurement System With Dual-Optical Path White Light Micro Interference

Liquid crystal display(LCD)is widely used in intelligent electronic products because of its small size,low power consumption and convenient interface control.The thickness and uniformity of the LCD have a direct impact on the definition performance of the display,so it is significant to measure the thickness of the LCD.In this paper,the principle and characteristics of common thickness measurement methods are analyzed and compared,According to the characteristics of the LCD and the measurement requirements,a new system of the thickness measurement with Dual-Optical Path white light Micro interference is designed,the main contents are as follows:1.The system uses the Mirau interference light path,it is divided into two same and symmetrical devices,a unified coordinate system is established to determine the corresponding position relationship of the left and right device.Two beams of white light are respectively focused on the left and right surfaces of the measured object,and two CCD are used to collect the white light interference image formed on the respective surface of the object,through analyzing the white light interference image on two CCD in the unified coordinate system,we can get the thickness of the measured object.2.Based on the measurement principle,selecting the white light source,Mirau interference microscope,image acquisition device and other optical elements to design interferometric optical imaging system,designing erection bracing structure for each optical element and the adjusting mechanical structure for the whole system.3.The white light interference image is processed by MATLAB,which realizes the function of extracting the center of the cross line,calculating the slope for any direction of the stripe and so on.Especially presents a method of three color separation to extract zero level fringe center of the white light interference,compared with the existing methods,this new method is based on the physical nature of white light interference fringes,the position of the zero level fringe center will be more simple and reliable.4.After the light path adjustment,system calibration and thickness measurement for the system of the thickness measurement with Dual-Optical Path white light Micro interference,the reliability of the system is verified by comparing with the Vertical length measuring instrument of 0.1?m accuracy,the measurement resolution can reach 0.4nm,the relative thickness measurement range for measured surface is about 0-8?m,basically meet the measurement requirements of liquid crystal display.