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Image Quality Which Metric Should I Choose

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Image quality criteria defines the imaging performance of an optical system ... Opto-mechanics: Tolerancing, statics, deflections, thermal effects, vibration ... – PowerPoint PPT presentation

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Title: Image Quality Which Metric Should I Choose


1
Image Quality Which Metric Should I Choose?
  • Jed Hancock
  • Optical Sciences 521

2
Image Quality Criteria
  • Image quality criteria defines the imaging
    performance of an optical system
  • This is how you know you are done
  • Most often a complex process
  • The criteria is usually described by multiple
    image quality metrics (WFE, MTF, etc)

3
Image Quality Metrics
  • Evaluation of metrics
  • Typically modeled (ray trace codes) then tested
    (calibration)
  • Image quality is affected by the mechanics
  • Optical engineers tool bag
  • Opto-mechanics Tolerancing, statics,
    deflections, thermal effects, vibration
    isolation, material properties, precision
    adjustments, mounting of lenses, windows,
    mirrors..

4
Spot Diagrams
  • Effective for applications where ( ¼ ?)
  • Specific types of aberrations can be determined
  • Geometric or RMS radius
  • Geometric metric

5
Ensquared Energy
  • Geometric estimate of energy on a pixel
  • Imaging and non-imaging applications where (¼ ?)
  • Geometric metric

6
Wavefront Error
  • Optical path difference between the actual wave
    and reference wave
  • Measured in the exit pupil plane
  • Aberrations can be determined by wave fan plots
  • Geometric metric

7
Modulation Transfer Function
  • The optical transfer function (OTF) is the
    autocorrelation of the complex
  • pupil function and it is also the Fourier
    transform of the point spread function
  • The MTF is the modulus of the OTF
  • Extended scenes, small aberrations, complete
    system analysis
  • Geometric and diffraction metric

8
Point Spread Function
  • The point spread function captures diffraction
    effects or the wave
  • nature of light
  • Small aberrations ( ¼ ?)
  • Youngs double pin hole experiment
  • Diffraction metric

9
Strehl Ratio
  • Best for small aberrations ( ¼ ?)

10
Geometric vs. Diffraction
11
Choose Appropriate Metrics
  • Often times more than one image quality metric
    should make up the
  • criteria, this depends on the application
  • If WFE were the only image quality metric chosen,
    the effect of an
  • obscured aperture on image quality could be
    overlooked
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