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TechnologyTelecentric lens systems for wide-field low-F# monochromatic imagingModern integrating CCD cameras with cooled detectors allow low-light level imaging of atmospheric phenomena. In many cases it is desirable that this imaging be monochromatic, so that spatial spectral data are obtained to relate to various excitation processes.Normal camera lenses have large ray angles to the principal ray throughout their optical path, and so are unsuitable for use with narrow-band interference filters. The shift of transmission wavelength with filter angle increases as the angle squared, so that larger ray angles rapidly requires much wider filters. To overcome this problem, telecentric systems can be designed, where the principal ray of all image-forming cones across the field of view cross the image plane parallel to the optical axis. Thus the maximum ray angles through the filter are determined only by the F-number of the lens. For low-light-level imaging, it is desirable to operate at the lowest F-numbers possible. Lower F-numbers mean higher ray angles through the filter, and so require wider-band filters. However, narrow-band filters are readily available at much larger diamaters than the imaging detectors (for example CCDs). Imaging instrumentation from Keo Scientific are thus designed to form monochromatic images (1.8 - 2.0 nm filter bandwidth) of wide-angle fields (up to 180 degrees fish-eye) onto imaging detectors at effective F-numbers as low as F0.7. There are many possible parameters to vary depending on the application. As there are some limitations determined by the availablility of commercially produced singlets, doublets and camera lenses, Keo Scientific works intimately with a lens-making factory in order to design and grind a variety of special lenses required to meet design goals. Keo Scientific have, through years of experience, an understanding of the many aspects of the design process, and can assist customers in planning an optimal system for their particular application.
Keo Scientific personnel are also actively involved in the design and construction of....
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