Performance Evaluation of MTF Peak Detection Methods by a Statistical Analysis for Phone Camera Modules Kwon, Jong-Hoon; Rhee, Hyug-Gyo; Ghim, Young-Sik; Lee, Yun-Woo;
To evaluate the autofocusing performance of recent mobile phone cameras, it is necessary to determine the peak position of the center field MTF (Modulation Transfer Function), -known as the through focus MTF- of the module. However, the MTF peak position found by conventional methods deviates from the ideal position due to the focus scanning resolution of mobile phone cameras. This inaccurate peak position results in false judgements of the optical performance, leading to yield losses or customer complaints. An increase in the focus scanning resolution can address this problem, but the manufacturing UPH (Unit per Hour) level will also unfortunately increase as well, resulting in a loss of manufacturing capabilities. In this paper, several fitting models are studied to find an accurate MTF peak position within a short period of time. With an analysis of a large amount of manufacturing data, it is demonstrated that the fitting methods can reduce false judgements and simultaneously increase the capabilities of the manufacturing system.
Phone camera lens module;MTF peak detection;Autofocusing;Through focus MTF;
J. Conrad, "Depth of field in depth," www.largeformatphotography.info (2006).
M. T. Heath, "Interpolation," in Scientific Computing in Introductory Survey, 2nd ed. (McGraw-Hill, New York, USA, 2001), Chapter 7.
G. Bohm and G. Zech, “Probability distributions and their properties,” in Introduction to Statistics and Data Analysis for Physicists (Deutsches Elektronen-Synchrotron, Hamburg, 2010), Chapter 3.
N. M. Razali and Y. B. Wah, “Power comparisons of Shapiro-Wilk, Kolmogorov-Smirnov, Lilliefors and Anderson-Darling tests,” Journal of Statistical Modeling and Analytics 2, 21-33 (2011).
ISO12233:2000, “Photography-Electronic still-picture cameras-Resolution measurements,” 7-16 (International Standard, Geneva, 2000).
M. Marchywka and D. G. Socker, “Modulation transfer function measurement technique for small-pixel detectors,” Appl. Opt. 31, 7198-7213 (1992).
P. D. Burn, "Slanted-edge MTF for digital camera and scanner analysis," in Proc. IS&T 2000 PICS Conference (Portland, OR, USA, March 2000), pp. 135-138.
S. Najafi and K. Madanipour, “Measurement of the modulation transfer function of a charge-coupled device by the combination of the self-imaging effect and slanted edge method,” Appl. Opt. 52, 4724-4727 (2013).
S. M. Hong and J. H. Jo, “Development of an equipment for measuring the MTF of camera phone lenses,” Korean J. Opt. Photon. (Hankook Kwanghak Hoeji) 18, 31-36 (2007).
J. H. Kwon and H. G. Rhee, “Field curvature correction according to the CMOS image sensor curvature using an air gap optimization,” J. Opt. Soc. Korea 19, 658-664 (2015).