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Construction of a Tabletop Michelson Interferometer (view source)
Revision as of 03:18, 13 July 2009
, 03:18, 13 July 2009no edit summary
* [[Huygens Principle for a Planar Source|Determining the angle of the diffraction minimum for a circular aperture]]
* [[Huygens Principle for a Planar Source|Determining the angle of the diffraction minimum for a circular aperture]]
== Estimating Camera Sensitivity ==
It is critical to understand the sensitivity of the camera to light from the interferometer, given the high intended image acquisition speed. The camera purchased for this setup, Casio EX-F1, has a movie frame rate capability of 1200 Hz. The following information allows an order of magnitude estimate of the sensitivity. (The camera uses a CMOS sensor.)
* a sample CMOS chip, Micron's MT9P401, has sensitivity of 1.4 V/lx·s and supply voltage of 2.8 V yielding 2 lx·s of light energy to saturation.
* Light intensity conversion - 320 lm/W given:
** a 100 W incandescent light bulb is measured to have the perceived intensity of about 1600 lm
** a rough figure of efficiency for a 100 W is 5%
Using these conversions, the sensor pixels saturate at 6.3×10<sup>-3</sup> W·m<sup>2</sup>·s. At 1200 Hz acquisition rate, assuming 100% duty cycle, the saturation figure is 5.2×10<sup>-6</sup> W·m.
Now, let us assume that only about 5% of 1 mW laser light reaches the sensor due to cleanup in the beam expander and the light transmitted through the diamond. If the light is expanded to a 2 cm diameter beam, the beam at the sensor is rated at 1.6×10<sup>-8</sup> W·m<sup>2</sup>
The two order of magnitude shortfall means that very little of the dynamic range of the sensor will be used, leading to a low signal to noise ratio. Increasing the specification of the laser to 5 mW may be called for as a result.
* [[Parts List]]
* [[Parts List]]