Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Patent
1997-06-30
1998-12-29
Font, Frank G.
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
356406, 356432, 356433, G01N 2125, G01N 2100
Patent
active
058546812
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device and to a method for measuring or detecting optically at least one characteristic or a variation of at least one characteristic of a reacting substance such as its absorbance for example, comprising notably of self-calibration of the device which overcomes possible drifts.
2. Description of the Prior Art
French Patent 701,318 describes a device for measuring optical characteristics of a reacting substance contained in a transparent cell such as its true absorbance. It comprises a light source, a first optical branch and a second optical branch, allowing selective passage of the light through the cell and outside it, an optical system for forming rays that have gone through the first or the second optical branch and a selective optical filter from an array of three selective filters, the first one being centred on a first wavelength corresponding to the isobestic point of the reacting substance, the second on a wavelength situated in a part of the light spectrum where the substance is the most sensitive and the third in another part of the spectrum where the substance is the least sensitive, means for measuring the intensity of the light that has gone through the optical system, and allowing determination of characteristics of the substance by combining intensity values of the light that has gone through the cell containing the substance and a reference cell.
This method used provides accurate and reliable results, but it does not overcome due notably to the aging of the various components and differences in the optical path or paths.
All the drift effects due notably to the aging and to the degradation of the various components of the device and to instabilities due to the optical paths are thus eliminated.
SUMMARY OF THE INVENTION
The object of the invention is to measure or to detect optically at least one characteristic of a reacting substance contained in a transparent cell, or the variations or changes in this substance, such as its true absorbance. The invention comprises at least one light source linked by at least one optical branch to a device allowing selective passage of the incident light coming from the light source through the cell and outside it, at least one reference filter, an optical system for forming rays that have gone through the device allowing selective passage and a selective optical filter, a device for measuring the intensity of the light that has gone through the optical system, a control unit, with the device allowing selective passage being controlled by said control unit and a power supply unit.
The device and the method according to the present invention improves the accuracy of measuring optical characteristics by performing a self-calibration of the device, for example, throughout the making of measurements.
The device for selecting the passage of the light is suited for allowing passage of the incident light through the cell and/or through at least one of the reference filters and/or directly outside the cell and at least one of the filters.
The optical filter can be selected from an array of three selective filters, the first one being centred on a first wavelength corresponding to the isobestic point of the reacting substance, the second on a wavelength in a part of the light spectrum where the substance is the most sensitive and the third in another part of the spectrum where the substance is the least sensitive.
The control unit comprises for example a control processor, a light intensity measuring signal acquisition unit and an interface unit for controlling the selection device.
According to an embodiment, the optical system comprises an optical derivation device for directing towards the three filters the light beams which have gone through the light passage selection device, the measuring device include three detectors for measuring the light that has gone through the three filters, and the electric switching device include elements for connecting intermittently dev
Delignieres Robert
Durand Christian
Font Frank G.
Institute Francais du Petrole
Merlino Amanda
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