Dome for photonics module requirements

[originalfoo]

Specifications

Note: Incomplete and likely to change

• Wavelengths: IR, Vis, UV -- depends what optics are in the dome
  • Will need to know which wavelengths are blocked to assess if they will cause problems with any of the photonics
• Internal coating: Preferably anti-reflective (≤2% reflection)
• External coating: Ideally hydrophobic
  • Need to check optical transparency properties of hydrophobic coatings
  • Need to check that hydrophobic coating won't bork the rainlight sensor
• Transmittance: ≥ 98%
• Diameter tolerance: ±0.1mm or better
• Thickness tolerance: ±0.2mm or better
• Weight: As light as possible (drone mode)

[originalfoo]

Should ideally have a lip around base, like this, to ensure it can be firmly held in place (the photonics module has to be hermetically sealed).

Unlike CCTV camera domes, which face down, this one will face up. So when the outer sheath is placed over it (around the edge, pushing down on the lip when screwed on to base of photonics module), there is risk that grime will build up where the outer sheath meets the dome. Is there a way to avoid that?

[originalfoo]

Needs to handle being used at sea.

[originalfoo]

Via @ZiadJ - this dome is almost the exact shape required:

However it is perhaps too big (depends on final size of the heliospectrometer = hyperspectral camera, its lenses and heliotrope).

There are a few other issues with it:

• Small bumps in the lip may cause problems with hermetic sealing
• 4 screw holes instead of 3 indicates it's designed for basic deployments (security cams); stresses associated with drone or ship deployment would likely crack it
• No anti-reflective coating
• It blocks UV which would prevent UV sensors from working to full potential