Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Patent
1996-12-24
1998-05-26
Le, Que
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
2505593, 356 306, H01J 4014
Patent
active
057569878
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to a photoelectric displacement detector which receives reference light so as to detect the amount of displacement of a measuring object (an object that is measured) by using, as a basis for measurement, a light receiving position where the reference light is received. The present invention pertains in particular to a photoelectric displacement detector for measuring the amount of settling and the amount of inclination of a tank which vary with the amount of a substance, such as liquid and gas, held in the tank, for measuring the amount of strain and the amount of settling of a building and for measuring the amount of settling of a ground.
2. Description of Related Art
It is known in the art that, in measurement of the amount of strain of a building or in measurement of the amount of settling of a ground, reference laser light is given off from a laser aligner and the survey operator then determines the amount of displacement of a measuring object by making use of the laser light as a reference for measurement. In other words, the survey operator, who has visually confirmed a beam spot of the laser light, places a mark on the measuring object to the center of the beam spot and measures the position of the measuring object by making use of the mark as a reference for measurement. This measurement technique is also employed to determine the amount of shift from the vertical lines of pillars and walls of a building under construction, to determine the amount of strain of a completed building and to determine the amount of displacement of a bridge.
The above-described instrumentation technique, however, has some drawbacks. For example, the use of a beam spot of laser light from a laser aligner as a measurement reference produces the problem that, although it is required to find an exact beam spot center, the beam spot expands as the distance between the laser aligner and a measuring object increases. It is therefore hard for the survey operator to visually find the beam spot center, resulting in poor measurement accuracy. To cope with such a problem, an arrangement, in which a reference laser light beam is detected using a light sensor or the like, may be employed. This arrangement, however, suffers from the problem that, since the survey operator carries out measurement work by making utilization of the center of a beam spot detected by the light sensor as a basic for measurement, the accuracy of measurement may vary with the difference in capability among individual survey operators or with the survey operator's physical conditions. Poor measurement accuracy may result.
SUMMARY OF THE INVENTION
Bearing in mind the above-described problems with the prior art techniques, the present invention was made. It is therefore an object of the present invention to provide an improved photoelectric displacement detector capable of determining a displacement of a measuring object at high accuracy with respect to reference light.
The present invention provides an improved photoelectric displacement detector comprising: receiving reference light, the light receiving surface being divided into light receiving sub-surfaces; output signals from the light receiving sub-surfaces, a difference in the quantity of received light between the light receiving sub-surfaces; means such that the photoelectric conversion means is linearly movable; the photoelectric conversion means; received light quantity difference, detected by the light quantity difference detection means, is cancelled to zero; and photoelectric conversion means at the time when the received light quantity difference is cancelled to zero.
In accordance with the above-described photoelectric displacement detector of the present invention the amount of displacement of a measuring object with respect to a reference light beam can be determined automatically. More specifically, the photoelectric displacement detector, described above, is first fixed to a measuring object and
REFERENCES:
patent: 4269512 (1981-05-01), Nosler
Ferguson Jr. Gerald J.
Le Que
Technical System Co., Ltd.
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