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

2. Chapter 2 System Evaluation

3. Optical System

4. basic frameworkbasic framework of Optical System

5. Types of Optical System

6. Reading/writing system

7. 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

16. Ghost image analysis

18. Opto-mechanical design

19. Optical detection

20. Optical testing

27. Imperfection of optical system Ideal point object → optical system → diffused patch of light Reason? 1. Aberration 2. Diffraction limitation 3. Imperfection of the medium ( air disturbance, anisotropy of the medium) Optical system

28.  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. Means of evaluation:

29. 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

30. MICROCOPY TEST TARGET Data: Conforms to NIST/NBS 1010A, & ANSI/ISO test chart #2; frequency shown in cycles per mm and changes by an average of 12.2% per step; image overall 38mm x 45mm Notes: Read direct resolution; ideal for evaluation of Optical / Mechanical Systems where reduction and low resolution is of interest.

31. Data: Designed to MIL-STD-150A; frequency changes by 6 √2 progression; image overall 71mm x 58mm; also available in custom sizes and contrasts. Ideally suited for Imaging materials, Visual resolution or Optical systems. USAF 1951 TEST TARGET

32. Data: Layout and features are the same as provided in the traditional USAF 1951 Test Target (T-20) meeting all requirements specified in MIL-STD-150A. The following improvements have been made: 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.

33. Data : All bars and spaces are the same as provided in the traditional USAF 1951 Test Target chart T-20, meeting all requirements as specified in MIL-STD-150A. The following are improvements: 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

34. Data: Alphanumeric configuration with frequency range 1-18 cycles/mm in 25 groups. Overall image area of 50 x 50mm is divided into 4 quadrants. Available in custom sizes and contrasts. RIT ALPHANUMERIC CHART Note s: Especially useful in Optical / Visual evaluation or where cross consistency among users is important.

35. Data : The NBS-1952 Resolution Test Chart is described in the NBS circular 533, 1953 in the section titled Method of Determining the Resolution Power of Photographic Lenses. The design features of this target reduce edge effects, minimize spurious resolution and permit single pass scanning. NBS-1952 RESOLUTION TEST CHART Notes : The NBS method of using this chart to test lenses involves placing the chart at a distance from the lens equal to 26 times the focal length of the lens, resulting in a 25x reduction. The reduction effective frequency is 12 to 80 cycles per mm.

36. Data : Frequency range in c/mm (20:1). Other frequencies are available on request. Note s: Each bar and space is progressively smaller in a log manner. Peaked groups every 10 bars. Ideally suited for SAYCE TARGET microdensitometric scanning. Other reduction ranges, contrasts and materials are available.

37. Data: Wedge shaped segments with 45 equal bar and space widths over a 360 circumference (8 degrees per cycle or 4 degrees per spoke). Image size is 50mm in diameter. STAR SECTOR TARGET Note s: An ideal target for detecting Optical Astigmatism, Focus Errors and other aberrations. Can easily be incorporated into complete target arrays.

38. Do you trust your vision ??

39. Do you still trust your vision ??

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

41. 2-1 Contrast 3.Non-repetitive contrast example -- dark letters on 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

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

43. 2-2 Transfer Function 1.Transfer factor —Modulation transfer factor T The transfer factor is a function of spatial frequency R imageobject

44. 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 spatial frequency R:

45. 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)

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

47. 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

48. 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

49. 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.

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

51. 2-2 Transfer Function Both T(R) and  (R) are the function of spatial frequency: Ideal perfect lens: T(R ) = 1, and  (R) = 0 At all spatial frequency Practical lens: at low spatial frequency: R<10mm -1 T(R ) → 1, and  (R) → 0 at high spatial frequency: R>100mm -1 T(R )↓→ 0, and  (R) ↑ → 1

52. 2-3The experiment of MTF 1—light source 2—slit 3—lens under test 4—rotating drum 5—photo-detector 6—reference grid Before adding the lens, put the grid on the drum, record the signal as object; After adding the lens, form image of slit on the drum, record the signal as image. MTF total =MTF lens1  MTF lens2  ……  MTF film

53. Example Photographs are taken from a high-altitude aircraft of a cruise ship, the MTF of a typical camera lens is that show in figure ship brightness: 5 units, the ocean: 2 units contrast: chose the focal length for the image size. Image 0.5mm R=1, T=0.8, → M’=0.8  0.43=0.34 Image 0.05mm R=10, T=0.7, → M’=0.7  0.43=0.3 OK to be seen Image 0.005mm R=100, T=0.2, → M’=0.2  0.43=0.086 cannot be seen

54. Home work: Question 1, 2, 3, 4, 5