Optics: measuring and testing – Oil testing
Patent
1990-10-22
1993-03-23
McGraw, Vincent P.
Optics: measuring and testing
Oil testing
250576, 324157, 356 72, 356440, G01N 3328, G01N 2188, G01N 2159
Patent
active
051968983
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an optical liquid sensor adapted to measure the degree of degradation or contamination of engine oil, frying oil, water, ink or the like o the concentration of a liquid such as coffee, tea, etc. according to the transmission loss of light, a method of manufacturing said sensor and an automotive oil/battery checker utilizing the same sensor.
BACKGROUND ART
The hitherto-known optical liquid sensor comprises a mirror and a beam splitter as illustrated in FIG. 19. Here, a light output 72 of a light-emitting element 71 passes through a beam splitter 73 (or a photocoupler) and an optical fiber 75 accommodated in a flexible duct 74 and reaches a detection means 76. The detection means 76 comprises said optical fiber 75 and a mirror 77 juxtaposed with an intervening gap .epsilon. which is to be filled up with a liquid substance to be tested (hereinafter referred to as the test liquid) A transmission loss of light attributable to the test liquid occurs in the course of travel of light 72 as it is reflected by the mirror 77 and returns to the optical fiber 75. A reflected light 78 returning to the optical fiber 75 is reflected by the beam splitter 73 and impinges on a light-receiving element 70, the output of which is amplified by an amplifier 80 for detection. This light output has been attenuated according to the transmission loss caused by the test liquid in the gap .epsilon. and the degree of contamination or the concentration of the liquid is determined from the degree of the above attenuation.
In the above optical liquid sensor employing a mirror and a beam splitter, reflection losses at the mirror 77 and beam splitter 73 are fairly large and the sensitivity of the system is as much decreased. Therefore, the use of a high-sensitivity amplifier 80 is essential. Moreover, an expensive beam splitter 73 is an absolute necessity. Thus, the initial cost of the system is high. Furthermore, in the system employing a mirror 77, the distance of travel of light is 2.times..epsilon.. Therefore, when the test liquid is one of large transmission loss, the gap .epsilon. must be so small that it is difficult to fill and remove the test liquid with respect to the gap .epsilon..
Having been accomplished to overcome the abovementioned disadvantages, the present invention has as its object to provide an optical liquid sensor which is highly sensitive and provides ease of filling and removal of the test liquid.
It is another object of the present invention to provide a method of manufacturing such an optical liquid sensor.
A still another object is to provide an automotive oil/battery checker employing the sensor.
SUMMARY OF THE INVENTION
The optical liquid sensor of the present invention comprises a folded-back optical fiber, a light-emitting element disposed at one end of said optical fiber, a light-receiving element disposed at the other end, and a detection means wherein each rod lens and/or a large-diameter glass optical fiber forming a pair is accommodated in juxtaposition with a narrow gap interposed therebetween in a linear segment of a folded-back portion of said optical fiber, with said folded-back portion being hermetically sealed except at an aperture for admitting a liquid to be measured into said narrow gap.
Since the detection means is formed with a narrow gap interposed between two of said rod lens and/or large-diameter glass optical fiber forming the pair in a linear segment of said folded-back region, the loss of light at said narrow gap due to offset of the light path is minimized. Furthermore, the rod lens and/or large-diameter glass optical fiber is chemically stable against a variety of liquids to be measured and this stability also reduces chances for the occurrence of losses of light. Thus, when the rod lens is used, the transmission light through the narrow gap is collimated into a beam of parallel rays, while the large-diameter glass optical fiber offers a large light reception area with respect to said narrow gap, with the result that the loss of li
REFERENCES:
patent: 2889736 (1959-06-01), Borg
patent: 4893935 (1990-01-01), Mandel et al.
patent: 4989942 (1991-02-01), Koenigsberg et al.
Ishihara Akihiro
Masui Tadaaki
Takatori Taizo
Tamura Kunimitsu
McGraw Vincent P.
Tatsuta Electric Wire and Cable Co., Ltd.
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