Concave optics

Mountain Instruments offers concave optics that can be tailored to specific customer requirements. These include various coatings, mirrors, lenses, windows, prisms, polarization optics, UV and IR optics and optical filters. In the field of concave optics, we distinguish between bi- and plano-concave optics.

Plano-concave optics

Plano-concave lenses convert incident parallel beams into divergent beams.  Like plano-convex lenses, these lenses minimize aberrations at absolute conjugate ratios of more than 5 or less than 1/5. Plano-convex lenses with parallel beams should be inserted into the curved side of the lens.

Biconcave optics

These lenses are similar to plano concave lenses and are best used with absolute conjugate ratios between 1/5 and 5. Biconcave glass lenses are concave on both sides and have negative focal lengths. The lenses diverge collimated incident light and form virtual images that are seen through the lens. They are used e.g. in laser beam expanders, optical character readers, viewers and projection systems.

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Example specification for a biconcave component

Material: BK7 – quartz glass – quartz – Mf2G
Focal length: +/- 2%.
Design Wavelength: 546.1 nm
Diameter tolerance: 0.2 mm
Centering: < 5 angular minutes
Wavefront distortion: λ/10
Effective opening: 90 % of diameter
Surface quality: S/D 10-5
Anti-reflection coating: Yes / No / on request