Recommendations for Selecting Lens Glass in the Design of a 3D Camera Protective Case

Knowledge Base
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For applications requiring protection on 3D cameras on-site, a 3D camera can be placed inside a protective enclosure with glass windows.

Recommendations

Key point Recommendation
Glass material Germany’s Schott BK7 or N-BK7 (BK7 is environmentally friendly) / Chengdu Guangming’s K9 or H-K9L (K9 is environmentally friendly)
Glass surface type Flat glass, high flatness, not suitable for tempered glass
Glass thickness 1–3mm (as thin as possible while maintaining high flatness)
Glass coating Double-sided AR coating (visible light transmittance ≥ 98.5%)
Mounting Glass window should be positioned close to the camera window, surface should be as parallel to the camera window as possible, avoiding deformation due to external forces

Additional Info: Introduction to Glass Selection

The material, surface type, and installation of the glass window all impact the imaging performance of the lens, which directly affects the measurement results of the 3D camera.

To minimize the impact on the measurement results, the glass window needs to meet the following requirements:

  • Low refractive index
  • High Abbe number
  • Low absorption rate
  • High optical uniformity
  • High flatness

According to the above requirements, we selected from commonly used optical glasses those two:

  • Germany’s Schott’s BK7 and N-BK7 (BK7 is environmentally friendly)
  • Chengdu Guangming’s K9 and H-K9L (K9 is environmentally friendly)

The glasses mentioned above are equivalent, with a refractive index of 1.52 and an Abbe number of 64.2. Their positions in the Abbe diagram are as follows.

K9 glass

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BK7 glass

Abbe-Diagram nd-νd
Description of symbols
image N-glasses
image P-glasses
image Classical crown and flint glasses
image Glass available as N-glasses or classical flint glasses
image Glasses suitable for precision molding
image HT - High transmittance glasses
image HTultra - Ultra high transmittance glasses
image Radiation resistant glasses
image Available in step 0.5

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For more information on technical details of Germany’s Schott glasses, please refer to Optical Glass: Technical Details.