Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrometer
Reexamination Certificate
1998-12-29
2001-05-01
Evans, F. L. (Department: 2877)
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrometer
C356S334000
Reexamination Certificate
active
06226084
ABSTRACT:
The present invention relates to a method of wavelength calibration of an optical system, and to selfdiagnosis of such a system comprising such calibration.
BACKGROUND OF THE INVENTION
Prior art spectrophotometer systems frequently make use of a deuterium lamp as a light source. The advantage of such a lamp is that it burns nicely in a continuous manner, and it has a couple of well defined wave length peaks. However, the intensity of a deuterium lamp is relatively low. In a liquid chromatographic system the small flow cells requires high intensity light in order to make adequate detection possible. Also the optical system comprising e.g. fibre optics require much more light than is delivered by a deuterium lamp. Wavelength calibration in such systems is performed by locating a single peak. This inevitably yields problems of accuracy at the short wave and long wave ends respectively of the wave length scale. It is also very important that a selected wave length be reproducible. The reproducibility reachable in calibration should be at least ±2 nm.
U.S. Pat. No. 5,212,537 is directed to a method of calibration for monochromators and spectrophotometers, using a continuous light source, a tungsten filament mercury vapour lamp, having two sharp intensity peaks. The location of the peaks is identified by measuring the width of said peaks at half height, and the midpoint of this width is taken as the location of the peak. This technique would not be possible to use in connection with a flash lamp, e.g. a Xenon lamp, since the intensity of the peaks fluctuates.
U.S. Pat. No. 5,268,737 is directed to calibration of a spectrophotometer. As the source of continuous light, a deuterium lamp and a tungsten lamp is used. A point of reference is determined by using zero order light. This would not be possible in connection with the use of optical fibres for transmission.
SUMMARY OF THE INVENTION
The object of the invention is to provide an improved calibration method for a spectrophotometer system, wherein the drawbacks of the prior art systems are remedied.
This object is achieved with the method of the present invention.
The advantage of the method as claimed is that by virtue of the high brightness of the flash lamp used in the method, the amount of light introduced in the system is increased, and that the accuracy in the calibration is ascertained over the entire wavelength region of interest.
REFERENCES:
patent: 4565447 (1986-01-01), Nelson
Amersham Pharmacia Biotech AB
Evans F. L.
Malia Victoria M.
Ronning, Jr. Royal N.
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