Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrometer
Reexamination Certificate
1998-10-20
2002-09-17
Evans, F. L. (Department: 2877)
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrometer
C356S334000
Reexamination Certificate
active
06452674
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a wave correction apparatus, and relates in particular to a compact wavelength correction apparatus which automatically detects and compensates for wavelength deviation.
2. Description of the Related Art
As known generally, optical spectrometer or spectrum measuring device is an apparatus for determining wavelength or frequency components contained in a beam of light output from a light source.
Spectrum measuring device is comprised by an input slit for inputting light to be analyzed, a diffraction grating element for spectral dispersion of input light, and an output slit for outputting only a portion of the waves separated by the diffraction grating.
To determine a spectrum of light used for communication purposes, for example, the operator first decides the frequency range to be scanned, and while rotating the diffraction grating with respect to the input light, wave components output from the output slit are measured against time.
The angular frequency of the diffraction grating and the optical frequency are related directly one on one so that the output data is related to the spectrum of the input light.
Lately, because of advances in optical communication technologies, high precision is demanded in spectrometer performance, and as the spectrum measuring precision is increased, it has become necessary to take into account possible errors in measurements introduced by changes in ambient conditions of the measuring apparatus (for example, temperature variations within the spectrometer).
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an wavelength correction apparatus that enables a deviation between a testing wavelength and a reference wavelength to be compensated on-site, automatically, using an in-situ spectrometer installed within the apparatus.
The object has been achieved in a wavelength correction apparatus for correcting a deviation of a testing wavelength from a reference wavelength, comprising: a reference light source for emitting reference light of a specific wavelength; a light input terminal for inputting a testing light whose wavelength is to be measured and compensated, if required; an optical switch for receiving the testing light and the reference light and outputting one of either the testing light or the reference light from an output terminal; a control section for controlling operations of the reference light source and the optical switch; and an optical spectrum measuring device for measuring optical spectrum output from the optical switch, and for activating the control section at scheduled times specified by an operator.
According to the apparatus, corrective steps can be taken automatically at any desired time, therefore, correction process is significantly facilitated and made more convenient.
Also, because the reference light source is a type that permits a compact arrangement, the installation space need not be very large, making the apparatus quite adaptable to many practical situations.
Also, because the correction process can be carried out automatically at any desired time, the process can be carried out even when the apparatus is being used to perform spectral measurements.
The optical spectrum measuring device may be comprised by: an optical element for transforming light input from an input section into parallel light; a diffraction grating for receiving the parallel light and producing spatially separated waves; an optical condensing element for concentrating the spatially separated waves on an output slit; a photodetector forconverting light exiting from the output slit into electrical signals; a conversion section for converting analogue signals output from the photodetector into digital signals; and a processing section for varying an orientation angle of the diffraction grating and for performing computational processing of the digital signals so as to produce an optical spectrum of the testing light.
The optical spectrum measuring device may include a timer means having calendar functions, and may operate the control section according to signals output from the timer means at schedules times.
The optical spectrum measuring device may include a timer means having calendar functions, and may operate the control section when signals output from the timer means indicates that a specific time interval has elapsed since the apparatus was powered.
The reference light source may be comprised by: a light emitting diode for emitting light of specific wavelengths; an optical element for transforming light output from the light emitting diode into parallel light; a gaseous absorption cell for absorbing light of a specific wavelength from light transmitted through the optical element; a condensing element for concentrating the light transmitted through the gaseous absorption cell for input into the optical switch.
REFERENCES:
patent: 4681444 (1987-07-01), Ferber et al.
patent: 4779216 (1988-10-01), Collins
patent: 5557404 (1996-09-01), Matsui et al.
patent: 3641017 (1986-12-01), None
patent: 19639939 (1996-09-01), None
patent: 0618653 (1997-07-01), None
patent: 0800066 (1997-10-01), None
patent: 2293650 (1996-04-01), None
Ando Electric Co. Ltd.
Evans F. L.
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