Abstract

We studied the characteristics of annular phase gratings as spatial frequency filters. We first calculated the Fraunhofer diffraction patterns of annular gratings and then got the modulation transfer function (MTF) from the zeroth order Hankel transform of the intensity distribution function. Binaryphase annular grating shows higher diffraction efficiency than binary phase rectangular grating. But the MTF decreases linearly in the low-frequency region as that of rectangular grating does. The diffraction pattern of 4-phase annular grating is similar to that of 2-phase grating and hence MTFs of the two are much alike. For 8-phase annular grating, the 7th order diffracted beam is the lowest one next to the first. Consequently, the diffraction efficiency is very high and the MTF graph is curved upward. The diffracted beams except the first order are negligible and hence the MTF characteristics are more improved in the case of 16-phase grating. But the degree of improvement becomes lowered c(Impaled with 8-phase grating. We made a 16-phase annular grating and measured its MTF. The experimental result agrees well with the calculated one.

Keywords

• Annular grating;
• Optical low-pass filter;
• Modulation transfer function;
• Digital imaging system;
• Aliasing;
• Moire fringe;
• Resolution

File

Download PDF

References

1. CCD Arrays, Cameras, and Displays G. C. Holst
2. Analysis of Sampled Imaging Systems R. H. Vollmerhausen;R. G. Griggers
3. Sampling, Aliasing, and Data Fidelity G. C. Holst
4. U. S. Patent, P.4761682 Optical low-pass filter including 3-crystal plates for solid state color-TV camera T. Asaida
5. Appl. Opt. v.29 Color dependent optical prefilter for the suppression of aliasing artifacts J. E. Greivenkamp https://doi.org/10.1364/AO.29.000676
6. Jpn. J. Appl. Phys. v.35 Grating optical low-pass filter K. Fusisawa;M. Uetsiki;Y. Nishida https://doi.org/10.1143/JJAP.35.1768
7. Opt. Eng. v.42 Grating images of multiphase grating optical low-pass filters Y. H. Oh;J. C. Lee;S. Lim;S. H. Kim;C. S. Go https://doi.org/10.1117/1.1554404
8. Jpn. J. Appl. Phys. v.41 Grating optical low-pass filters with near perfect stop band characteristics C. S. Go;Y. H. Oh;S. Lim;S. Kim;J. C. Lee https://doi.org/10.1143/JJAP.41.L1090
9. 전기전자재료학회지 v.16 no.12S 컴퓨터로 설계한 홀로그램 광 저대역 필터의 특성 분석 김인길;고춘수;임성우;오용호;이재철 https://doi.org/10.4313/JKEM.2003.16.12S.1261
10. Appl. Phys. v.B no.74 The filtering characteristics of simple grating optical low-pass filter J. C. Lee;S. Lim;S. H. Kim;Y. H. Oh;C. S. Go
11. Interduction To Fourier Optics J. W. Goodman
12. Linear Systems, Fourier Transforms, and Optics J. D. Gaskill
13. CCD Arrays, Cameras, and Displays G. C. Holst