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Optical Filters



Colour Enhancement - SpectraPLUS Filters

SPECTRAPLUS is a patented triple bandpass, interference filter coating that enhances colour and improves overall spectral performance. This filter benefits colour imaging systems as well as applications where the eye is the detector. The coating allows transmission of the three bands of pure colour - red, green, and blue - while blocking those intermediate wavelengths that distort the perception or recording of colour. It also eliminates wavelengths in the ultraviolet and near infrared which are detrimental to an accurate colour rendering and visual record.

SPECTRAPLUS offers accurate hue, enhanced saturation, increased colour signal-to-noise, and a resulting improved Modulation Transfer Function (MTF).

We suuply two SPECTRAPLUS coating designs - one is optimised for digital imaging sensors (XB29) and one is optimised for the human eye and film (XB30). All filters are finished to the highest imaging quality standards and are available in stock and custom sizes.

SPECTRAPLUS is protected by U.S. patent #5,646,781.

XB29: Digital Imaging Filter

Overview

The SPECTRAPLUS XB29 filter is specifically designed for use with digital imaging systems and CCD-based cameras. These systems are sensitive to wavelengths beyond the visible which contribute no useful information for colour imaging.

This version of SPECTRAPLUS blocks the crossover regions between blue/green and green/red centered at 490nm and 600nm respectively. To prevent IR saturation of silicon-based sensors, the coating provides a high degree of attenuation in the near infrared region, from 750nm to 1100nm. The XB29 also offers complete attenuation of ultraviolet A and B, and deep blue up to 430nm. These wavelengths may seriously impact apparent colour and reduce image sharpness.

Applications

SPECTRAPLUS XB29 has application in the optical systems of video cameras, remote sensing cameras, digital cameras for still photography, machine vision systems, and CCTV cameras. It eliminates the need for a red blocking filter, typical of CCD cameras. The XB29 is also appropriate for use in any color reproduction process based on digital sensor technology. These applications include pre-press scanners in the commercial printing industry, and desktop scanners and color copiers in the office products industry. As with all interference filters, the coating is most efficient across the entire field of view when the transmitted light is at an angle of incidence no greater than 30°.

XB30: Eye & Film Filter

Overview

The SPECTRAPLUS XB30 filter is optimised for applications where the human eye or photographic film is the detector. Colour imaging is enhanced with increased saturation, accurate hue, and improved contrast and resolution. This version of the SPECTRAPLUS filter has two stop band regions centered at 490nm and 580nm for blocking the prime colour "crossover" wavelengths between blue/green and green/red in the visible spectrum. The XB30 offers high attenuation of ultraviolet A & B. It also attenuates the near infrared in a band centered at 725nm.

Applications

SPECTRAPLUS XB30 has numerous applications in the photography, film, and video industries including: video, motion picture, and slide projection; photography, film, and video lenses; and enlarger lenses. In lenses the coating can be applied to lens elements or used as a discreet filter, both at slightly increased exposure time or lens aperture. In the architectural and theatrical lighting industries the filter can be used as a fixture filter or as a coating on bulbs or reflectors. It also has use in medical and dental lighting (where colour rendition is important). The coating improves "seeing" in ski goggles, sports eyewear, sunglasses, and sports optics especially in low light and flat light conditions. The filter is most effective in applications where the light is collimated, striking the filter at angles of incidence less than 30°.