Why is there a brass spacer behind the lens interface on some systems?
The UVCorder™ is designed to use conventional C-mount TV lenses that are much lower cost than quartz UV lenses, and in some cases, actually provide superior image quality. The C-mount back working distance of these lenses assumes that visible light is being imaged. UV light focuses slightly longer than visible light, which sometimes requires that a thin brass shim spacer be placed behind the lens so that the UVCorder™ will properly form an image for targets at infinity. Newer systems are using different lenses that do not require the spacer.
