PROCEEDINGS ARTICLE | September 11, 2013
Proc. SPIE. 8907, International Symposium on Photoelectronic Detection and Imaging 2013: Infrared Imaging and Applications
KEYWORDS: Optical imaging, Infrared imaging, Reflectors, Mirrors, Light sources, Imaging systems, Data acquisition, Infrared radiation, Modulation transfer functions, Stray light
Modulation transfer function (MTF) is one of the most important parameters of infrared focal plane array (IRFPA). A double-knife edge scanning method is proposed for MTF measurement of IRFPA. In this method, a double-knife edge was used as a target, and the IRFPA under test was positioned in the focal plane of the imaging optical system by a 3-axis translation stage. With an IRFPA data acquisition system, the image of the double-knife edge was restored. By scanning in the direction orthogonal to the double-knife edge image, edge spread function (ESF) curve of each pixel swept across the knife-edge image was obtained. MTF could be calculated from the subsequent fitting, differential and Fourier transformation procedures. With double-knife edge scanning, two ESF curves of double-knife edge were obtained simultaneously, and symmetry of the two ESF curves could be used to evaluate the verticality between photosensitive surface of IRFPA and optical axis of the double-knife edge imaging system. In addition, this method can be used to judge the existing of interference from outside such as vibration, stray light and electrical noise. A measurement facility for IRFPA’s MTF based on double-knife edge scanning method was also established in this study. The facility is composed of double-knife edge imaging optical system, 3-axis translation stage and data acquisition system, et al. As the kernel of the facility, the double-knife edge imaging optical system mainly comprises two symmetrical parabolic mirrors coating with reflective material, and the magnification of the optical system is 1 with an operation wavelength range of (1∼14) μm.
