Difference between revisions of "Manta G032 camera measurements"
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* <math>I_{x,y}[t]</math> is the number of photoelectrons that are generated during interval <math>t</math>, | * <math>I_{x,y}[t]</math> is the number of photoelectrons that are generated during interval <math>t</math>, | ||
* <math>R_{x,y}[t]</math> is the read noise during time interval <math>t</math>, | * <math>R_{x,y}[t]</math> is the read noise during time interval <math>t</math>, | ||
− | * and <math>D_{x,y}[t] is the number of dark current electrons generated during time interval <math>t</math> | + | * and <math>D_{x,y}[t]<math> is the number of dark current electrons generated during time interval <math>t</math> |
− | The variance | + | The variance <math>P_{x,y}</math> is equal to the noise squared. <math>P_{x,y}</math> is the sum of three terms. The total variance is equal to the sum of the variances of individual term. <math>I_{x,y}</math> is Poisson distributed, so its variance is equal to its mean, <math>\langle I_{x,y} \rangle</math>. The second term has a constant variance that is a property of the camera, <math>N_r</math>. The third term is Poisson distributed, with an average value of <math>I_d \delta t</math>. This gives: |
:<math>\left\langle\left(P_{x,y}-\overline{P_{x,y}}=g\left(\langle I_{x,y}+N_r^2\right)\right)\right\rangle</math> | :<math>\left\langle\left(P_{x,y}-\overline{P_{x,y}}=g\left(\langle I_{x,y}+N_r^2\right)\right)\right\rangle</math> | ||
{{Template:20.309 bottom}} | {{Template:20.309 bottom}} |
Revision as of 19:31, 22 September 2015
Overview
This page contains data from the demo I did in lecture on 9/22/2015 of the Manta G032 camera.
The point was to measure the gain $ g $, dark current $ I_d $, and read noise $ N_r $ of the Manta G032 cameras we use in lab.
Measurement procedure
- Light source directed at the camera so to produce a range of intensities
- 100 frame movie recorded at 20 FPS with an exposure of 150 μs.
- 100 frame dark movie recorded with identical settings.
- Variance of each pixel (noise squared) plotted versus average value (signal).
Calculations
The expression for the value read from pixel $ x,y $ during time interval $ t $ is:
- $ P_{x,y}[t]=g \left(I_{x,y}[t]+R_{x,y}[t]+D_{x,y}(t)) \right) $,
where
- $ I_{x,y}[t] $ is the number of photoelectrons that are generated during interval $ t $,
- $ R_{x,y}[t] $ is the read noise during time interval $ t $,
- and $ D_{x,y}[t]<math> is the number of dark current electrons generated during time interval <math>t $
The variance $ P_{x,y} $ is equal to the noise squared. $ P_{x,y} $ is the sum of three terms. The total variance is equal to the sum of the variances of individual term. $ I_{x,y} $ is Poisson distributed, so its variance is equal to its mean, $ \langle I_{x,y} \rangle $. The second term has a constant variance that is a property of the camera, $ N_r $. The third term is Poisson distributed, with an average value of $ I_d \delta t $. This gives:
- $ \left\langle\left(P_{x,y}-\overline{P_{x,y}}=g\left(\langle I_{x,y}+N_r^2\right)\right)\right\rangle $