Real-time auto-focusing technique using centroid method for space camera  

作　　者：匡海鹏 李朝辉 刘明 刘刚 修吉宏 翟林培 

机构地区：[1]Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Science [2]Aviation University of Air Force

出　　处：《Journal of Harbin Institute of Technology(New Series)》2007年第4期577-579,共3页哈尔滨工业大学学报（英文版）

摘　　要：A real-time auto-focusing system with auto-collimation method is introduced, which is used in auto-detecting the focus of the space camera with long focus. Auto-focusing is the key technique to ensure high quality in space imaging. It can measure and compensate the defocus caused by the change of temperature and air pressure etc. in space. To solve the problem of auto-focusing with auto-collimation method of the camera whose axis is perpendicular to the ground, it is designed that two small caliber pentagonal prisms are placed in the area of aperture suitable to the camera’s relative aperture based on the theory of auto-focusing with auto-collimation, which can replace the big caliber plane reflector used in other cameras. Using the characteristic of pentagonal prism refracting light vertically, the target slit is imaged in CCD through the two-separated lens. It transforms the detecting of the axial defocusing quantity to the landscape orientation measurement of the faculae’s position in the direction of CCD pixels. The defocusing quantity is obtained by measuring the opposite position of the two faculae on the CCD. The Centroid method is adopted to measure the position of the auto-collimation faculae. The arithmetic error is analyzed especially, and the causation is given. Experiments show that this real-time auto-focusing system using centroid method is reliable and the focusing precision can reach ±0.01 mm.A real-time auto-focusing system with auto-collimation method is introduced, which is used in auto-detecting the focus of the space camera with long focus. Auto-focusing is the key technique to ensure high quality in space imaging. It can measure and compensate the defocus caused by the change of temperature and air pressure etc. in space. To solve the problem of auto-focusing with auto-collimation method of the camera whose axis is perpendicular to the ground, it is designed that two small caliber pentagonal prisms are placed in the area of aperture suitable to the camera’s relative aperture based on the theory of auto-focusing with auto-collimation, which can replace the big caliber plane reflector used in other cameras. Using the characteristic of pentagonal prism refracting light vertically, the target slit is imaged in CCD through the two-separated lens. It transforms the detecting of the axial defocusing quantity to the landscape orientation measurement of the faculae’s position in the direction of CCD pixels. The defocusing quantity is obtained by measuring the opposite position of the two faculae on the CCD. The Centroid method is adopted to measure the position of the auto-collimation faculae. The arithmetic error is analyzed especially, and the causation is given. Experiments show that this real-time auto-focusing system using centroid method is reliable and the focusing precision can reach ±0.01 mm.

关 键 词：AUTO-FOCUSING linear array CCD centroid method 

分 类 号：TP274.5[自动化与计算机技术—检测技术与自动化装置]