Description

This chapter entails the re-definition of the requirement for VPH grism

Tasks

[x] Look into whether apex angle affects image quality (check scientific requirements) at all - sept 30
[x] Determine next steps into determining a required apex angle
- [x] reach out to Wasatch to see if they can provide any support
  - [x] how apex angle affects diffraction efficiency
  - [x] 900-1700 - update spectral range, confirm with Wasatch
[ ] look into critical angle
[x] look into index modulation (data sheets) which one we’re using
[ ] If yes,
- [ ] Look into how image quality is impacted - oct 7
  - [ ] Read on literature concerning this in hyperspectral systems
- [x] look into impact on efficiency
- [ ] Create requirement in Requirements Model: Optics

→ How it affects image quality, if at all:

main finding: efficiency, angular dispersion, and view through apex side is magnified while the other side is compressed
If you decrease the prism angle and hence the grating frequency, you may see a small boost in diffraction efficiency. If the grating spatial frequency needs to increase, the average diffraction efficiency will start to decrease
- Typically apex angle will be defined by Wasatch’s design, but can be altered depending on our dispersion requirements.

changing the apex angle of the prism requires a change to the spatial frequency of the grating in order to maintain a straight-pass geometry
- the change in apex angle will determine the change in grating frequency
decreasing the prism angle decreases the grating frequency → may see small boost in diffraction efficiency
bandwidth of the grating isn’t well centred for 900-1700nm passband
- exit angle for shortest wavelength would leave the grism at 85 degrees → they can’t procure an AR coating that would work across this range
GRISM REDESIGN:
- 400 l/mm grating with centre wavelength 1300nm

Next Steps