Researches On Power Control And Design Of Miniaturized System For Small Defocus Detection In Laser Writing Equipment

Laser direct writing equipment is widely used in manufacturing a variety of diffractive optics devices because of the high diffraction efficiency, the large manufacturing size, the simple process of making and the high precision, and it has become an important tool of manufacturing diffractive optical devices.In this paper, named as"Researches on power control and design of miniaturized system for small defocus detection in laser writing equipment", we focus on two major technique concerns of the laser direct writing equipment. One is the control of the unstable situation in the power of laser beam. We aimed at stabilize the power of laser beam and make it adjustable. The other is to precisely detect the distance between the laser beam focus and the substrate.The paper is organized as follows:Firstly, through analyzing the performance of the laser used in laser direct writing equipment, several advantages and disadvantages of light intensity control methods is compared. The acoustic optical modulator(AOM)is selected as the control device for the power control. The loop power control system based on acoustic optical modulator is constructed with AOM and other suitable devices. Based on the study above,together with the PID control algorithm for the system and the appropriate PC software, the instability of the laser optical power has been ultimately resolved.Secondly, the confocal sensing mechanism and analyze features of ordinary differential confocal and the improved differential confocal is briefly introduced. The advantage of applying differential confocal principle as a means of inspecting focus is presented as well. In this paper, a dynamic small defocus detection device based on the difference Confocal principle is designed. With a method to alignment of the pinhole using three-dimensional displacement platform and stress-free UV adhesive, the pinhole is fixed in the accurate position. Eventually the device for detection the defocus distance of the laser direct writing is completed.Finally, the performance of the laser direct writing optical power control system and miniature defocus detection device through well-designed experiment is tested. According to the experiments data, the power control system for the laser direct writing can control light intensity in the range of 5-100mW and the stability of light intensity from uncontrolled increase in front of±1.2% to±0.2%; The detection distance range of the small device for detection the defocus distance is 20μm, and the resolution of the defocus detection is 10nm. The two subsystems have reached the requirement of the laser writing equipment.