Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
1998-10-08
2001-03-20
Lee, John R. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S231100, C033S366001, C033S390000, C356S249000
Reexamination Certificate
active
06204498
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an inclination sensor which utilizes a liquid member having a free surface. In particular, the invention is concerned with an inclination sensor best suited for a surveying instrument and capable of being constituted in a compact form by disposing a half mirror on an optical path of both the liquid member and a light receiving optical system, as well as a surveying instrument using the inclination sensor.
Heretofore, as a device for detecting inclinations of a surveying instrument there has been used such a bubble tube
10000
as shown in FIG.
9
. In the interior of the bubble tube
10000
, bubbles
5000
are sealed and electrodes
6000
and
7000
are formed, to measure a capacitance electrically and thereby determine an inclination.
However, since the outer peripheral portion of the bubble tube
10000
is formed of glass, it is weak against impact and a high mechanical accuracy is required, thus giving rise to the problem that the cost is high.
Further, for measuring inclinations in both X- and Y-axis directions, it is necessary to use two bubble tubes
10000
in two-axis directions, thus causing an increase of cost.
Additionally, the bubble tube
10000
is also influenced by changes in ambient temperature and hence it has so far been required to make correction of temperature changes.
SUMMARY OF THE INVENTION
In the present invention, which relates to an inclination sensor using a liquid member having a free surface, a first optical system collimates light emitted from a light source, a scale pattern allows the light from the first optical system to mass therethrough, a half mirror changes the direction of the light which has passed through the dark field pattern, a first liquid member having a free surface reflects the pattern light thus changed its direction by the half mirror, a second optical system focuses the pattern light reflected by the first liquid member, a light receiving means receives the light image formed by the second optical system, and a processing means calculates an inclination on the basis of a reception signal provided from the light receiving means. The scale pattern is formed by a plurality of slits, and the half mirror is disposed on the optical path of both the liquid member-and the second optical path.
REFERENCES:
patent: 4993162 (1991-02-01), Scholian
patent: 5392112 (1995-02-01), Nakamura
patent: 5513001 (1996-04-01), Ohtomo
patent: 5893215 (1999-04-01), Kumagai et al.
Kumagai Kaoru
Ohtomo Fumio
Baker & Botts L.L.P.
Kabushiki Kaisha Topcon
Lee John R.
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