# 변이불변 특성이 개선된 광굴절 상관기를 이용한 실시간 광 패턴인식 시스템 구현

• 김성완 (경북대학교 전자전기공학부) ;
• 김철수 (경주대학교 정보통신공학과) ;
• 김종찬 (경북전문대학 전자과) ;
• 김종윤 (경북대학교 전자전기공학부) ;
• 이승희 (대경전문대학 정보통신과) ;
• 김수중 (경북대학교 전자전기공학부)
• Published : 1998.03.01

#### Abstract

In this paper, a new input method is proposed to improve shift-invariant property of a photorefractive correlator andwe implemented real-time optical pattern recognition system using it. In the conventional photorefractive correlator, it is vrey difficult to satisfy the Bragg condition in the pattern recognition process. So, correlation peak is decreased heavily for the shift of input image. If a liquid crystal television(LCTV) without an anlyzer is used as input device, we can get the correlation result regardless of shift of input image because beam path is not changed during storage of holographic filter and correlation process. Also recording time of a holographic matched filter in photorefractive crystal is reduced and the correlation peak is increased because incident beam on the LCTV is transmitted completely. Therefore total optical efficiency is improved. We compared and analyzed the correlation results of proposed photorefractive correlator by computer simulation and optical experiment. We used a BaTiO$_{3}$ single crystal which has high diffraction efficiency in optical experiment.