Today we spent almost all of our time working on the alignment of our setup. In the morning, we figured out that the lens collimator (the cheaper one) was not focusing because it was too close to our source of light. After lengthening the distance, the collimator worked quite a bit better. Unfortunately, the collimator sends out the light over a larger area, so not as much light passed through the monochromator as when it was uncollimated. So after a couple hours, we had to decide to scrap the idea of collimation before the monochromator.
We spent a great deal of time working on the transfer of light from the monochromator to a collimator at the end of it and spent a couple hours making minute changes to the position of the collimator in the x, y, and z-axes and the vertical tilt and horizontal rotation. We did this using stacked manual stages which we could move different parts of to adjust the position. We also discovered that the optical tube between the final collimator and the microscopic lens was too short, as the image of the fiberoptic core from the cable, reflected from the mirror of the collimator, was appearing as a dark spot in our camera view. After switching out the tube, the image appeared more uniform.
After fixing up the alignment to a high degree of accuracy, we experimented with different exposure settings on the camera, allowing it to take in more or less light to reduce saturation in the image. I unfocused our point of light and moved the camera back in over a range of 50 microns, taking 10 pictures at each 5-micron step, recording the distance of the camera and the exposure time setting from the properties and settings on the monitor. Tomorrow we will input all the pictures into MATLAB and crop the images to the right zones so that we can average the sets of pictures for each distance to cancel out most of the noise we received with our signal.
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