Bispectral fluorescence, also know as bispectral fluorescence colorimetry, is a method of determining both the luminous and reflected component of materials that exhibit fluorescence. This technique requires a double monochromator system, with both monochromatic illumination and a monochromator for the reflected/emitted light to separate the fluorescent and reflected components on the output side. This technique is the only way to fully characterize materials such as high visibility safety materials ("daylight fluorescents") and for the optical brighteners used in the textile and paper industries.

Avian Technologies is the only laboratory in the world to offer bispectral fluorescence measurements at both directional/directional (45/0) and hemispherical (d/8) geometries. We provide measurement services as well as calibration of artifacts traceable to KCL, the national laboratory of Finland, one of only three laboratories in the world to offer bispectral fluorescence measurements. Our instruments are:

• A Labsphere BFC-450 Bispectral Fluorescence Colorimeter. This instrument, which won a Photonics Spectra "Product of the Year" award, was the first commercial instrument to measure bispectral fluorescence. The instrument illuminates the sample with a circumferential beam at 45 degree incidence and collects at normal. The geometry of the instrument meets CIE 15.2 optical specifications for a 45/0 instrument.
• Minolta CM3800d Fluorescence Colorimeter. This is the first and only commercial sphere-based instrument designed to measure bispectral fluorescence. The instrument was designed primarily for the paper and textile industries but can be used to measure the bispectral fluorescence of almost any material. The instrument uses a xenon source for illumination and a 150 mm integrating sphere in the specular included mode for collection. Spot size is approximately 1 cm. diameter.

Measurements can be provided that give full bispectral data for total spectral radiance and the radiance of the reflected and fluorescent components, colorimetric data, along with ISO brightness.

For further information and an introduction to bispectral fluorescence, see A. Springsteen"An Introduction to the Measurement of Color of Fluorescent Materials", Analytical Chimica Acta, Vol. 380 (1999) and related articles in the same volume. See also: slp.nist.gov/appearance/springsteen.pdf and J. Leland, N. Johnson and A. Arecchi "Principles of Bispectral Fluorescence Colorimetry" in A.V. Arecchi (Ed.) Photometric Engineering of Sources and Systems, 29-30 July 1997, 3140, 76-87, San Diego, USA.