Apparatus for correcting theodolites

• US 4,136,955 A
• Filed: 08/27/1976
• Issued: 01/30/1979
• Est. Priority Date: 09/02/1975
• Status: Expired due to Term

• Current Assignee: Kern and Co AG (Hexagon AB)
• Original Assignee: Kern and Co AG (Hexagon AB)
• Inventors: Nunlist, Rene, Aeschlimann, Heinz, Stocker, Rudolf
• Primary Examiner(s): Buczinski, S. C.
• Application Number:
  US05/718,375
• Time in Patent Office: 886 Days
• Field of Search: 33/281-286, 33/291, 33/366, 33/377, 33/391, 33/1 T, 33/1 PT, 250/237 G, 250/231 SE, 356/110, 356/138, 356/140, 356/149, 356/141, 356/152, 356/5
• US Class Current: 356/139.1
• CPC Class Codes: G01C 1/02 Theodolites

Abstract

The corrected values to compensate for errors in instrumental levelling of a theodolite and similar instruments are found by determining angles of elevation and/or horizontal directions, measuring the instrumental levelling errors, and calculating the error free values of the instrument.

Claims

1. Apparatus for providing a relative measure of horizontal and vertical angles between first and second directions, comprising means to aim in said first and second directions, means to generate a periodic moire pattern with a relative position corresponding to the direction of said aiming means, four photoelectric receivers in line for sensing the relative position of said moire pattern, each of said receivers covering one fourth of one moire period and providing one signal of two pairs of electrical output signals in push-pull relationship, two differential amplifier means each connected to one of said push-pull output pairs, the differential output signals being in phase quadrature, a clock oscillator means having two output signals of corresponding phase quadrature, signal multiplier means, multiplying each differential output signal with one of the clock signals, forming two product signals, signal adding means, forming the sum of the two product signals and a phase meter for determining the phase difference between the output of said signal adding means and one of the clock signals, said phase difference being indicative of the relative position of said periodic moire pattern and of the direction of said aiming means.

2. Apparatus for providing a relative measure of horizontal and vertical angles between first and second directions, comprising means to aim in said first and second directions, means to generate a periodic moire pattern with a relative position corresponding to the direction of said aiming means, a self scanned linear photodiode array for sensing the relative position of said moire pattern, a charge amplifier, an integrator and a sample-hold circuit for processing the scanning signal of said array and an analog-digital phase-locked loop circuit (PLL) for determining the relative phase of said scanning signal, said phase being indicative of the relative position of said periodic moire pattern and of the direction of said aiming means.

3. Apparatus for providing a relative measure of horizontal and vertical angles between first and second directions, comprising means to aim in said first and second directions, means to generate electrical output signals indicative of the angle between first and second directions of said aiming means, a liquid mirror, a light source producing a collimated light beam which is reflected from the surface of said liquid mirror, a Schottky-Barrier fotodiode illuminated by said reflected light beam, an electronic processor circuit receiving the output signals of said Schottky-Barrier fotodiode and providing output signals indicative of levelling error and computer means generating from said angle and levelling error horizontal and vertical angles with levelling error compensation.

4. The apparatus according to claim 3, wherein said liquid mirror is housed in a container including a matching prism through which the collimated beam of said light source passes.

5. The apparatus according to claim 3, wherein said computer means for generating horizontal and vertical angles with levelling error compensation comprises a microprocessor means.

6. The apparatus according to claim 3, wherein said Schottky-Barrier fotodiode provides two independent output signals each being indicative of one of two components of levelling error.

7. Apparatus for providing a relative measure of horizontal and vertical angles between first and second directions, comprising means to aim in said first and second directions, means to generate electrical output signals indicative of the angle between first and second directions of said aiming means, a pendulum mounted to the coil of a galvanometric system, a light source, photoelectric receiver means mounted near the end of said pendulum and illuminated by said light source in dependence upon the attitude of said pendulum, a regulating loop circuit receiving the output signals of said photoelectric receiver means and activating said galvanometric coil by a regulating current to maintain said pendulum in a biased angular position, said regulating current being indicative of levelling error, and computer means generating from said angle and levelling error horizontal and vertical angles with levelling error compensation.

8. The apparatus according to claim 7, wherein said galvanometric coil is journalled by a stretched ribbon in a frame.

9. In an apparatus for providing a relative measure of horizontal and vertical angles between first and second directions with means to aim in said first and second directions, means to generate electrical output signals indicative of the horizontal and vertical angles between first and second directions of said aiming means, means to generate electrical output signals indicative of levelling error parallel to the direction of said aiming means and computer means generating, from said signals for the vertical angles and the levelling error, vertical angles with levelling error compensation the improvement comprising means to generate electrical output signals indicative of levelling error at right angles to the direction of said aiming means and computer means generating from said signals for the horizontal and vertical angles and the levelling error parallel and at right angles to the direction of said aiming means horizontal angles with levelling error compensation.