Share Email Print
cover

Proceedings Paper

Accurate focusing of knife-edge imaging optical system based on the area under MTF curve
Author(s): Bin Wu; Li-gong Li; Shang-qian Liu; Cheng-ping Ying; Kun-feng Chen
Format Member Price Non-Member Price
PDF $14.40 $18.00
cover GOOD NEWS! Your organization subscribes to the SPIE Digital Library. You may be able to download this paper for free. Check Access

Paper Abstract

The method of knife-edge scanning is always adopted in testing the MTF of infrared focal plane array (IRFPA), and accurate focusing is one of the most important preconditions in the measurement procedure, because the measurement accuracy of MTF is ensured only when IRFPA is placed in the focal plane of the knife-edge imaging optical system. In this paper, a focusing method based on the area value under normalized MTF curve is proposed. Firstly, we analyzed MTF calculation model, which contained derivation of edge spread function (ESF) and then Fourier transformation. In this way, the issue of larger area under normalized MTF curve meant better focusing degree of the measurement system was proved. Next, the quasi-focal plane position of knife-edge optical system was determined according to the output voltage values of pixels of IRFPA. Then a series of MTF curves were measured when IRFPA was placed at different positions located in the optical axis beside the determined quasi-focal plane at an increment of 60 μm. Subsequently, the area under each normalized MTF curve was calculated, and the result showed the area values presented a perfect Lorentzian distribution against the positions of IRFPA. It was concluded the peak position of the fitted Lorentzian curve corresponded to the position of focal plane of knife-edge optical system. With this method, the focal plane position of knife-edge optical system was determined. The method presented here can be used to focus the MTF testing system with a high accuracy, which is good for the following MTF measurement.

Paper Details

Date Published: 21 August 2013
PDF: 6 pages
Proc. SPIE 8908, International Symposium on Photoelectronic Detection and Imaging 2013: Imaging Sensors and Applications, 89081U (21 August 2013); doi: 10.1117/12.2034545
Show Author Affiliations
Bin Wu, Science and Technology on Electronic Test and Measurement Lab. (China)
The 41st Institute of China Electronics Technology Group Corp. (China)
Li-gong Li, The 41st Institute of China Electronics Technology Group Corp. (China)
Shang-qian Liu, Xidian Univ. (China)
Cheng-ping Ying, The 41st Institute of China Electronics Technology Group Corp. (China)
Kun-feng Chen, The 41st Institute of China Electronics Technology Group Corp. (China)


Published in SPIE Proceedings Vol. 8908:
International Symposium on Photoelectronic Detection and Imaging 2013: Imaging Sensors and Applications
Jun Ohta; Nanjian Wu; Binqiao Li, Editor(s)

© SPIE. Terms of Use
Back to Top