Geometrical instruments – Indicator of direction of force traversing natural media – Level or plumb – terrestrial gravitation responsive
Patent
1990-03-26
1992-04-07
Cuchlinski, Jr., William A.
Geometrical instruments
Indicator of direction of force traversing natural media
Level or plumb, terrestrial gravitation responsive
33379, G01C 924
Patent
active
051015706
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to an inclination angle detector which electrically detects an angle of inclination of an object of measurement with respect to the horizontal direction or the direction of gravitation.
2. Background Art
There has hitherto been known one type of conventional inclination angle detector comprising a bubble tube having a transparent container formed such that the inner surface of an upper part thereof has a spherical concave surface, the transparent container having a gas and a transparent liquid sealed therein, a light-emitting unit for emitting light towards the bubble tube from the upper or lower side thereof, a light-receiving element for position detection in four-divided circular form for converting the light transmitted by the bubble tube into an electric signal, and an operating unit for calculating an angle of inclination on the basis of the electric signal so that the light from the light-emitting unit which has been transmitted by the bubble tube is received by the light-receiving element in such a manner that, as shown in FIG. 11 or 12. A change in the light quantity distribution which is caused by changing a relative position of the bubble shadow b on the light-receiving element a in accordance with the angle of inclination is detected in the form of an electrical change by the light-receiving element a and the detected change is subjected to a calculation in the operation unit, thereby photoelectrically measuring an angle of inclination.
The above-described conventional inclination angle detector has, however, a disadvantage in that the results of measurement unavoidably include large errors due to fluctuations in a bubble diameter, the intensity of the light emitted from the light-emitting unit, the photoelectric conversion sensitivity of the light-receiving element, and the like caused by temperature changes, and the like.
Further, since the bubble shadow is circular in shape, there were disadvantages in that, when an angle of inclination increases, a) a sensitivity lowers and, consequently, b) a measuring range is restricted to a narrow one and c) a correction and the like are needed in order to obtain a correct angle of inclination.
The reason why the sensitivity lowers as an angle of inclination increases will be described below. The output of the light-receiving element is proportional to the quantity of light incident on the element, while the quantity of the incident light is proportional to the irradiated area. Therefore, in order to detect an inclination in the direction of X, for example, an area difference M between the two irradiated portions of the light-receiving element divided by the Y-axis may be obtained. The area difference M is given by: ##EQU1## where R=the radius of curvature of the bubble tube.
The inclination detecting sensitivity G is proportional to the quantity obtained by differentiating the area difference M with respect to the inclination .theta..sub.X as follows: ##EQU2##
The inclination detecting sensitivity G may be graphically shown as in FIG. 13.
In other words, when .theta..sub.X =0, G=4Rr, i.e., a maximum value, and as the inclination increases, G decreases, and when ##EQU3##
The fact that the sensitivity changes means that the measured value includes an error unless a sensitivity correction is made. Therefore, in such a condition that G=0, there is no change in the output even if an inclination is given, so that it is practically impossible to carry out measurement.
The above-described fact also applies to the inclination in the direction of Y.
Accordingly, it is an object of the present invention to provide an inclination angle detector which is capable of maintaining a high detection accuracy even under the conditions that there are changes in the bubble diameter, the intensity of the light emitted from the light-emitting unit and the photoelectric conversion sensitivity of the light-receiving unit due to temperature changes.
It is another object of the present invention to provide an inclinati
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G2298A/32 SU-485-308, Building Prod. Res. 26.01.73-SU-875652 (21.01.76)G01c-09/36.
Cuchlinski Jr. William A.
Fulton C. W.
Kabushiki Kaisha Sokkisha
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