Optics: measuring and testing – Refraction testing – Refractive rod engages specimen
Patent
1988-05-03
1990-06-26
Evans, F. L.
Optics: measuring and testing
Refraction testing
Refractive rod engages specimen
25022725, 25022731, 250577, 250905, 356375, 73293, G01N 2141
Patent
active
049366815
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an optical sensor for converting a physical value into an electric output signal, comprising a light source from which a beam of light rays is coupled into a first surface, preferably a first front face of a photoconductive body, the light rays being totally reflected by one boundary surface of, or coupled out from the said body in response to a given physical value and the totally reflected light rays being directed to a second rear face provided preferably opposite the said first face, and comprising further a plurality of light-sensitive elements for detecting the angular range covered by the beam after it has been totally reflected or coupled out as described.
A sensor of this type has been known from "Patents abstracts of Japan", June 21, 1980, Vol. 4/87.
The known sensor serves for measuring the concentration of the electrolyte of a lead storage battery. It comprises a light source emitting a diverging beam of rays which passes a diaphragm and impinges upon an inclined lateral surface of a prismatic photoconductive body. A lower, elongated boundary surface of the body is provided adjacent the electrolyte to be measured. The light rays of the diverging beam of rays impinging upon the lower boundary surface are either totally reflected by the latter or coupled out from the body into the electrolyte, depending on their angle of impingement and the density of the electrolyte. The totally reflected light rays impinge upon another, likewise inclined boundary surface of the prismatic body carrying a gate consisting of light-sensitive elements. Depending on the density of the electrolyte to be measured, the boundary between the light rays of the beam which are still totally reflected or, on the other hand, coupled out varies at the lower interface between the prismatic body and the electrolyte with the effect that the corresponding boundary line of the totally reflected light rays impinging upon the gate of light-sensitive elements changes, too. Given the fact that a partial beam is always reflected by the lower boundary surface, even if a certain amount of light rays is coupled out, one obtains an intensity curve rising abruptly from a relatively low signal level to a relatively high signal level, viewed over the length of the gate of light-sensitive elements. The known sensor now picks up the amplitude of the light rays impinging upon the different elements of the gate and uses the respective position on the gate of the abrupt rise of the signal level as a measure indicative of the density of the electrolyte.
However, it is a drawback of this known sensor that it must be adjusted very precisely because due to the single total reflection of the light rays by the prismatic body even very slight maladjustments of the impinging beam of light rays may already seriously invalidate the measuring results. In addition, the known sensor is connected with the disadvantage that in practice the density of the electrolyte is measured only in a point-like area, namely in a very small portion of the length of the boundary surface where the transition between total reflection and coupling out varies so that the measuring results are characteristic of the condition of the whole electrolyte contained in a vessel, for example in a storage battery, if the electrolyte contained in the battery actually exhibits uniform density. However, this is not always the case in practice because on the one hand lighter, for example warmer portions of the electrolyte tend to collect in the upper portion of the storage battery, while heavier portions will settle at the bottom, and in addition considerable variations in density over the volume of the battery may result from movements of the type occurring, for example, in motor vehicles. The known sensor is not capable of measuring the acid density between the plates of an accumulator, and its installation in pipes is difficult, too. Another disadvantage of the known sensor lies in the fact that it is always suited for a single measuring task only, namely for m
REFERENCES:
patent: 4544840 (1985-10-01), Keller
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