Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrometer
Patent
1991-03-05
1993-01-12
Turner, Samuel A.
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrometer
356345, 25022729, G01B 902
Patent
active
051794241
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an optoelectronic apparatus for the remote measuring of a physical size, this apparatus being of the type comprising a light source, a sensor subjected to the physical magnitude to be measured and causing spectral modulation of the luminous flux received from the source, at a frequency depending on the physical magnitude to be measured, as well as means for analysing the luminous flux transmitted by the sensor, for determining the value of the physical magnitude to be measured from the spectral modulation frequency of the luminous flux transmitted by the sensor.
Processes and devices of this type are already known in which sensors are used comprising birefringent elements sensitive to the physical magnitude to be measured. The analysis means generally comprise a demodulating interferometer tuned to the sensor for analysing, for example, a characteristic modulation of a beat frequency between the spectral modulation due to the sensor and that due to the demodulating interferometer.
The invention has as object an apparatus for measuring a physical magnitude at a distance, using means of the above type, i.e. a sensor sensitive to the physical magnitude to be measured, causing spectral modulation of the luminous flux transmitted at a frequency which depends on the value of the magnitude to be measured and analysis means which are static, compact and extremely accurate.
The invention also has as object an apparatus of this type in which the analysis means make it possible to obtain the absolute phase of the luminous flux transmitted by the sensor.
The invention also has as object an apparatus of the above type for multiplexing light sensors of the same type or of different types, situated in the same zone or in different zones.
For this, the invention provides an optoelectronic apparatus for the remote measuring of a physical magnitude, comprising a light source, a sensor subjected to the physical magnitude to be measured and causing periodic spectral modulation of the luminous flux received from the source, at a frequency depending on the physical magnitude to be measured and means for analysing the luminous flux transmitted by the sensor, these analysis means comprising a birefringent element tuned to the sensor and producing an optical difference of path close to that produced by the sensor, characterized in that the analysis means are of the static type and comprise polarization separating cubes associated with photodetectors and data processing means connected to the photodetectors for computing and determining the modulo 2 phase of the analysis signal transmitted by the birefringent element of the analysis means, and in that the apparatus comprises two light sources emitting luminous fluxes centred on different wavelengths, and means for controlling the alternate operation of these two light sources, the difference of the central wavelengths of the two light sources being such that the absolute value of the difference of the phases of the signals transmitted by the birefringent element remains less than .pi. for a given range of values of the physical size to be measured.
The polarization separating cubes which are traversed by the luminous flux coming from the sensor give (except for the coefficients) signals of the type 1.+-.cos.rho. and/or 1.+-.sin.rho., from which the phase of the signal can be determined modulo 2.pi.; such indetermination of 2 k.pi. may be removed by alternately using two light sources whose central wavelengths are relatively close to each other. Thus, the phase difference of the signals corresponding to these two light sources, for the same value of the physical magnitude to be measured, remains less than 2.pi. and the measurement of this phase difference makes it possible to remove the indetermination of 2 k.pi. on the determination of the absolute phase of the signal from the sensor. The knowledge of the value of the absolute phase makes it possible to determine the spectral modulation frequency introduced by the sensor and so, with calibration, to determi
REFERENCES:
patent: 4495411 (1985-01-01), Rashleigh
patent: 4536088 (1985-08-01), Rashleigh et al.
patent: 4609290 (1986-09-01), Cahill
patent: 4814604 (1989-03-01), Lequime
patent: 4867565 (1989-09-01), Lequime
Patent Abstracts of Japan, vol. 9, No. 93, Apr. 23, 1985, p. 351, JP 59-221618, Shimazu Seisakusho K.K.
The International Congress on Optical Science & Engineering, 12-15 Mar. 1990, La Haye, Conference 1267, Paper 1267-39, Session 5, M, Lequime, et al., "A Dual-Wavelength Passive Homodyne Detection Unit for Fiber-Coupled White-Light Interferometers".
Giovannini Hugues
Lecot Catherine
Lequime Michel
Bertin & Cie
Turner Samuel A.
LandOfFree
Optoelectronic apparatus for the remote measuring of a physical does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optoelectronic apparatus for the remote measuring of a physical , we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optoelectronic apparatus for the remote measuring of a physical will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1223422