Diffraction Spatial Imaging By Using The Technology Of Consecutive Variable-pitch Dot Matrix Grating

In order to fabricate digital dot-matrix hologram with consecutive variable-pitch interference, it is necessary that the mechanism structure, energy efficiency and the optical stability of the laser direct writing system should be considered fully. At present, the reported laser dirrect writing system with a two-beam interference has not achieved consecutive variable grating pitch due to the optical design and fabricating technology. In this paper, we have designed a two-beam interference system by using a LCD-SLM device on Fourier transform optical path. In the system, the LCD-SLM is placed in the front focus plane, and two apertures are opened on the LCD-SLM. When the Hght pass through the apertures, two beams will focus into a small interference dot (grating pixel dot) in the back focus plane. The system has a simple optical configuration, the high stability, the high resolution and adjustable dot size. The consecutive variable grating pitches can be achieved with this system by changing the distances and directions of two apertures. The final patterns written by this technology has the ability of diffraction spatial imaging. Especially, this system is suitable to fabricate the diffraction patterns with hidden information encryption . In addition, we have enumerated the formula of frequency & angle to compute grating pixel dots, written corresponding control programs. Some results ofexperiments are given. Although the efficiency of energy in the Fouriertransform system is low, comparing to ordinary grating-splitting two-beam interference photolithographic system, the exposure rate is still high due to the very small size of dot on the back focus plane.In appendent No.l, we analyzed the fabricating technology of the diffraction grating with non-symmetrical groove. It would be as a reference for fabricating non-symmetrical groove diffraction grating. As an example, we present a method for fabricating a color separate grating. The theory analysis and experiment results are given. The method has not the effect of alignment error as the conventional ways to fabricate binary optics elements (BOB), and can avoid the defects with large field angle imaging in gray-scale mask technology.