Optics Lecture 1 Flashcards
The illuminate or luminance distribution of the image of a point source of light
PSF
In the absence of defocus, aberration and scatter, the PSF is
Diffraction limited PSF
Defocus, aberrations and scattered light do what to the PSF
Shorten and broaden
The form of PSF depends upon
Shape and diameter of aperture
What controls impact of ocular aberrations and diffraction on retinal image quality
Pupil size
What size pupil give the best retinal image quality
3mm
3 ways that psf. Can be reduced to a single number that specifes the image quality
Rayleigh’s criterion
Half-width
Strehl ratio
2 point resolution limit occurs when the first minimum of one pattern coincides with the center max of the other pattern
Rayleighs criterion
Diffraction pattern often associated with rayleighs criterion
Airy disk
Width of PSF at half the peak heigh
Half-width
Half width of diffraction limited psf
3.23
What happens to the half-width as you increase aberrations
It increases
Measure of the effect of aberrations on reducing the max or peak value of the PSF
Strehl ratio
The greater the aberrations, the (higher/lower) the strehl ratio and the (better/poorer) the image quality
Lower the ratio
Poorer the image quality
How does the strehl ratio compare to 1
Always less than or equal to
What do aberrations do to the PSF and the max peak height
Spread out PSF
Decrease max peak height
A good, near to diffraction-limited system is that the strehl intensity ration has a value of
.8
Illuminate or luminance distribution in the image of a line source of light
LSF
What is the double pass method
Light distribution of a point source at the retina that cannot directly be measure, so the light passing back out of the eye is measured
Imaging systems ability to distinguish object detail
Resolution
How faithfully the minimum and maximum intensity values are transferred from object plane to image plane
Contrast or modulation
What 2 things are important to understand OTF
Resolution and contrast
OTF=
MTF + PTF
A function of spatial resolution which refers to the smallest line pair the system can resolve
MTF
Due to light attenuation, MTF is normalized to
1
Decrease in amplitude and causes transverse shift of image position is what aberration
Coma
Aberrations that produce a transfer shift produce an effective phase shift in the image known as
Phase transfer function
In an on-axis in a rotationally symmetric optical system, what happens with the phase spatial frequency
There is no change
OTF = MTF –> PTF = 0
For higher levels of defocus, what happens to MTF
Becomes negative
When the MTF is negative, what has happened to the image pattern compared with the object
Reversed contrast
The spatial frequency at which the modulation transfer function first goes to zero is
The resolution limit
Any resolution of higher frequency patterned is called
Spurious resolution
Phenomenon in which the contrast of image of a periodic grating first goes to zero as defocus is increased, them rises at higher levels of defocus
Spurious resolution
