Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrophotometer
Patent
1987-06-09
1988-07-19
McGraw, Vincent P.
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrophotometer
356323, 356328, G01J 342, G01J 336
Patent
active
047580852
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an optical fiber spectrometer/colorimeter apparatus intended, in particular, for use in an industrial environment.
Conventional good quality spectrometers and colorimeters are often apparatuses which are poorly adapted for use in an industrial environment. In general, accurate measurements can be obtained only by using them in a laboratory, with relatively long calibration operations being necessary prior to use, with samples then being taken for inspection, followed by repetitive measurements which may also take a considerable length of time depending on the amount of energy received by the spectrometer or the colorimeter, such that it is relatively difficult to associate apparatuses of this kind with continuous production lines.
The object of the present invention is a spectrometer/colorimeter apparatus capable of operating both as a spectrometer and as a colorimeter, which is presented in the form of a particularly compact integrated assembly, which is capable of performing calibration operations at regular intervals or at user request, and which is capable of performing very accurate and very rapid repetitive measurements.
To this end, the present invention provides an optical fiber spectrometer/colorimeter apparatus suitable for operating as a spectrometer and as a colorimeter, the apparatus comprising a spectrometer including an inlet and a mosaic of photodetectors, characterized in that it is essentially constituted by the association of a controlling microprocessor and an opto-electronic printed circuit card bearing the following items:
at least two optical fiber measurement paths ending at the inlet of the spectrometer, and fitted with shutters enabling the measurement paths to be switched;
wavelength calibration means for the detectors, comprising two reference emitters connected by optical fiber calibration paths to the inlet of the spectrometer;
the spectrometer and its mosaic of detectors ; and
electronic circuits for reading the detectors.
An apparatus in accordance with the invention thus comprises a single assembly with the following items integrated on a single opto-electronic card: a spectrometer; spectrometer calibration means; and measuring paths which merely need extending by optical fibers to those points at which light spectrum and/or color is to be measured, which points may be at considerable distances from the apparatus.
According to another characteristic of the invention, the detectors form a strip of adequate height relative to the height of the superposed ends of the optical fibers in an inlet slot, and, for example, when the optical assembly of the spectrometer has a magnification ratio of 1/1, their height is equal to the height of said superposed optical fiber ends.
At least four measuring and calibrating paths can thus be provided without it being necessary to interconnect these paths by optical couplers upstream from the inlet slot to the spectrometer and to equip these paths with shutters, which would cause photometric losses to occur in use.
According to yet another characteristic of the invention, the width of the inlet slot is less than the core diameter of the optical fibers, thereby improving the resolution of the apparatus.
According to yet another characteristic of the invention, the measuring path shutters include electrical means for reproducing their positions, thereby making it possible to validate measurements by inspecting the positions of the shutters.
During performing measurements using a spectrometer or a colorimeter comprising a plurality of measurement paths, it is important to be able to verify that only one measurement path is open and that the others are indeed closed.
According to yet another characteristic of the invention, the above-specified measurement paths constitute independent spectrometer measurement paths when the apparatus is operating as a spectrometer, and constitute a reference path associated with a light source and at least one measurement path associated with an object illuminated by said light source when
REFERENCES:
patent: 3874799 (1975-04-01), Isaacs et al.
Ratzlaff "Spectrophotometer Based on a CCD Photoarray Detector", Anal Chem, 1980, 52, 916-920.
Mesures, Regulation, Automatismes", vol. 49, #16, 12-84, pp. 75, 77, 79, 80.
Debrie Jean
Lequime Michel
Millet Jocelyn
Bertin & Cie
McGraw Vincent P.
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