Tilt detecting device

• US 6,248,989 B1
• Filed: 04/28/1998
• Issued: 06/19/2001
• Est. Priority Date: 05/09/1997
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Topcon
• Original Assignee: Kabushiki Kaisha Topcon
• Inventors: Ohishi, Masahiro
• Primary Examiner(s): Le, Que T.
• Assistant Examiner(s): Luu, Thanh X.
• Application Number:
  US09/067,747
• Time in Patent Office: 1,148 Days
• Field of Search: 250/205, 250/231.1, 250/577, 333/79, 333/662.3, 333/661.2, 333/661.3, 333/661.4, 333/661.6, 356/139.1, 356/436, 356/148, 356/249, 356/138, 200/61.52
• US Class Current: 250/205
• CPC Class Codes: G01C 15/004 Reference lines, planes or sectors
• CPC Class Codes: G01C 2009/066 optical
• CPC Class Codes: G01C 9/06 Electric or photoelectric indication or reading means
• CPC Class Codes: G01J 1/32 adapted for automatic variation of the measured or reference value regulation of light intensity G05D25/00

Abstract

The tilt detecting device of the present invention comprises a light transmission type electric bubble tube, a light source for emitting detection light to the electric bubble tube, a photodetector element for detecting emitted light amount for detecting an amount of light emitted from the light source, and a tilt detection control unit for controlling the emitted light amount of the light source to a constant level based on photodetection signal from the photodetector element for detecting emitted light amount, and causes of error are eliminated.

Claims

1. A tilt detecting device, comprising a bubble tube having an upper side and a lower side, a light source arranged on one of said upper or lower sides of said bubble tube, a pair of photodetector elements arranged on a side of said bubble tube opposite to said light source for receiving a transparent light beam, each of said pair of photodetector elements generating an output signal, a photodetector element for detecting the amount of light from said light source, a light source driving unit for controlling the amount of light emitted from said light source at a constant level based on the output signals from said photodetector element for detecting the amount of light, and a tilt detection unit for controlling said light source on and off and for detecting the tilt based on the output signals from said pair of photodetector elements both when said light source is turned on and when said light source is turned off such that the amount of light is controlled at a constant level.

2. A tilt detecting device according to claim 1, wherein the voltage difference of said photodetector elements is calculated both when said light source is turned on and when said light source is turned off, and the tilt according to the photodetection amount is detected based on said voltage difference.