Scalloping/Sawtooth Problem

8:13 AM 8/24/2018 A sawtooth pattern has developed in the spectrum. I'm not sure if it's due to the CCD binning not being aligned with the slit. With longer exposure times, there's a more urgent need to close the CCD shutter during readouts and work harder to block off stray light sources.

white light tests

50x lens 50x lens with reversed frame pixel order Post head, pre raman: Direct input to spectrograph 10x lens Post head pre raman: Direct into spectrograph: after fiddling: after adjusting spectrograph: background in each frame looks the same: same image after S-G processing closeup stitching looks but background looks identical, as if the whole sensor is acting like one pixel. Suggests electrical failure at the CCD since the background noise is higher than before. Checking for wiring problems... Not finding wiring problems. Shading the CCD seems to show all pixels responding. I don't know why the spectrum is identical between frames... Notch test. Notch is to the right of the laser line. Cut on at 150 kaysers Source: LED flashlight before Raman filt. Alternating red and blue indicate separate CCD frames. But still shows scalloping/sawtooth pattern. Source: flashlight after Raman filt. The Hamamatsu S7031 is an FFT type (Full-Frame Transfer) CCD which does not have an internal storage register. This requires use of and external shutter mechanism during readouts? Conclusion: scalloping/sawtooth pattern is most likely caused by a yaw and/or roll existing between the slit and the linear CCD. A yaw would probably be a less noticeable than a roll.