Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1992-07-10
1993-11-09
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
250226, 356448, G01N 2186
Patent
active
052605841
ABSTRACT:
A portable, hand held reflectometer which employs at least one blue light emitting diode for measuring the optical brightness of an opaque material, such as a stack or pad of paper is disclosed. A brightness measuring reflectometer which employs two blue light emitting diodes arranged so as to substantially reduce measured brightness variations caused by changing the orientation of the reflectometer relative to that of the fibers contained in a fibrous material such as paper whose brightness is to be measured is also disclosed. An ultraviolet light source such as a fluorescent lamp is also employed for measuring the brightness of paper or other materials which contain ultraviolet light excitable blue wavelength emitting substances. An electronic circuit for operating the reflectometer is also disclosed which employs a negative feedback circuit for maintaining the intensity of the ultraviolet light source at a relatively constant level.
REFERENCES:
patent: 4761676 (1988-08-01), Wiles et al.
patent: 5021645 (1991-06-01), Satula et al.
patent: 5150174 (1992-09-01), Ryczek et al.
Popson Stephen J.
Richey Kenneth A.
Miller Jr. Maurice L.
Nelms David C.
Technidyne Corporation
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