Log Book Entry No.103

Created: 28 Jun 2016 16:32:45

Last Revised: 28 Jun 2016 16:32:45

JosephBayley

Aligning Beam Splitter

Please edit and put your text etc. here

Focussing Beam Splitter

• To find best focus should be able to focus onto a single fibre, once one illuminated, in focus. will have to use extension rings for optical fibre.
• CCD camera can then be adjusted until in focus.
• Focus by shifting backwards and forwards on rails.
• Find focus of camera with max intensity and minimum width of laser.
• Use diffuser or neutral density filter, will need neutral density filter.
• Make two plots of intensity on camera and fiber and adjust until peaks overlap.
• Such that there are two plots which look similar to:

Aligning Beam Splitter

• Align by moving the mirror horizontally and vertically until maximum intensity
• possibly get 3 more irises, to control aperture at camera, fibre and entry, to make sure always have good alignment.
• As now in focus, can scan around fibres and find the relative positions compared to the end where they are arranged into line.
  • This could help with finding best position of ray on camera
• Look up mirror and see how much change in angle before lost fibre, one full turn until laser out of view.
• try to get two irises as far away from each other for best alignment.
• once part for CCD arrives, move around and find relative positions on camera to positions on optical fibre.

Relating to telescope

• Have to use larger beam size so that f# is the same as the telescope, f# = 10,
  • currently 3 dioptre lens, so 1/3 m focal length, this means need a beam diameter of 33.3 mm or a longer focal length.
  • as , where f is the focal length, d is the diameter of beam or aperture and f# is the f number.

• consider which camera to be used.
• beam splitter reflects 30% and transmits 70% so check this.

testing intensity

• tested the intensity at reflection and transmission, with diffuser and tissue in front of laser, tissue made intensity vary substantially so averaged over five frames, the reflection intensity was found to be 3% of the transmission intensity, however there could be problems with focus and alignment at the refection, need better analysis of this.
• Intensity_test.zip: Intensity_test.zip

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