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雅虎邮箱地址 :  docu_ioi@yahoo PW:zjuopt

雅虎邮箱地址 :  docu_ioi@yahoo.com.cn PW:zjuopt. Chapter 2 System Evaluation. Optical System. basic framework of Optical System. Types of Optical System. Reading/writing system. Image system. Image system. Illumination system. Special optical system.

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雅虎邮箱地址 :  docu_ioi@yahoo PW:zjuopt

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  1. 雅虎邮箱地址:  docu_ioi@yahoo.com.cn PW:zjuopt

  2. Chapter 2 System Evaluation

  3. Optical System

  4. basic framework of Optical System

  5. Types of Optical System

  6. Reading/writing system

  7. Image system

  8. Image system

  9. Illumination system

  10. Special optical system

  11. International optical standards & associations

  12. Optical design flow diagram

  13. Optical design products

  14. Double zoom lenses

  15. Ghost image analysis

  16. Opto-mechanical design

  17. Optical detection

  18. Optical testing

  19. Optical system Imperfection of optical system Ideal point object → optical system → diffused patch of light Reason? • Aberration • Diffraction limitation • Imperfection of the medium • ( air disturbance, anisotropy of the medium)

  20. Means of evaluation: • Resolution(Resolving power): The ability to distinguish the closely spaced lines or points • Transfer function: • Measure of performance of a system • Measure of transfer ability of a system • Let us predict theoretically, confirm or disprove experimentally • can be also to evaluate peripheral components, include: lens, photographic film, CCD, atmosphere, eyes etc.

  21. 2-1 Contrast 1.Object target Must take into account the contrast High contrast: a deep black object on a pure white background Low contrast: a gray object in a fog test chart

  22. USAF 1951 TEST TARGET

  23. USAF 1951 TEST TARGET - w/ Improved Labeling - The chart has direct frequency labeling in c/mm eliminating the need for cross reference documentation of frequencies.- Numeric labeling is enhanced, based on OCR-A extended font for maximum recognition.

  24. USAF 1951 TEST TARGET - w/ Improved Labeling and Features  - The chart has DIRECT frequency labeling in C/MM. - Numeric labeling is enhanced and based on OCR-A extended font. - Bars are laid out in two straight columns, for easier scanning. - Smaller elements have finder squares next to them to aid in determining their locations

  25. RIT ALPHANUMERIC CHART

  26. NBS-1952 RESOLUTION TEST CHART

  27. SAYCE TARGET microdensitometric scanning.  Other reduction ranges, contrasts and materials are available.

  28. STAR SECTOR TARGET

  29. Do you trust your vision ??

  30. Do you still trust your vision ??

  31. 2. Contrast Modulation  A definition for repetitive periodic object or image: a series of dark bars on bright background highest contrast: no contrast: barely visible contrast:

  32. 2-1 Contrast 3.Non-repetitive contrast example--dark letterson a gray background LB—amount of light from background LO-- amount of light from object Object darker than background, C positive Object brighter than background, C negative

  33. 4.Normalized ModulationM For objects of repetitive sinusoidal light distribution ( in most cases) The mean: The variation around the mean:

  34. 2-2 Transfer Function 1.Transfer factor—Modulation transfer factor T The transfer factor is a function of spatial frequency R object image

  35. spatial frequency R: the number of lines, or other detail, within a given length. Unit: 1p/mm or mm-1 Example1: R=4.0mm-1 → 4 pairs of black(lines) and white(intervals) in 1mm; Example2: R=100 mm -1 →100 pairs in 1mm →line width=1/200mm Example3: Line width=interval width=1mm → R=0.5 mm-1

  36. 2-2 Transfer Function 2.Spread Function A point(pixel) → optical system → diffuse patch of light point spread function S(y,z) A line → optical system → line spread function S(z)

  37. Point Spread Function Point Spread Function as a function of the visual angle

  38. The light distribution on image: the Integral form the derivation form: The modulation transfer function: the Fourier transfer of the spread function of that lens

  39. 2-2 Transfer Function 3.Phase transfer & OTF position incorrect (caused by coma, distortion) → dislocation of the image points → dislodged with respect to the ideal position Phase shift: (spatial phase)  is a function of spatial frequency  = f ( R ) Optical transfer function: O. T. F. describes the degration of an image, at different space frequencies

  40. Optical Transfer Function (OTF) The OTF is a complex function that measures the loss in contrast in the image of a sinusoidal target, as well as any phase shifts. The MTF is the amplitude (i.e. MTF = |OTF|) and the Phase Transfer Function (PTF) is the phase portion of the OTF.

  41. Modulation Transfer Function Variation of the Modulation transfer function of the human eye model with wavelength

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