Surveying instrument and method

• US 4,113,381 A
• Filed: 11/18/1976
• Issued: 09/12/1978
• Est. Priority Date: 11/18/1976
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Company (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Epstein, James Stephen
• Primary Examiner(s): Buczinski, S. C.
• Application Number:
  US05/742,941
• Time in Patent Office: 663 Days
• Field of Search: 356/5, 356/4, 356/141, 356/152, 356/138, 33/1 T, 33/281-285, 250/231 SE
• US Class Current: 356/5.12
• CPC Class Codes: G01C 3/02 Details
• CPC Class Codes: G01C 3/28 with provision for reduction of the distance into the horizontal plane
• CPC Class Codes: G01S 17/32 using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated

Abstract

A tacheometer utilizes a gallium arsenide laser diode in a phase shifting distance encoder, a sinusoidal interpolator in a phase shifting shaft angle encoder, a mercury pool in a phase shifting two axis off-level encoder, a shared phase to digital decoder and a digital processor, to measure angles and distances corrected for off-level, speed of light variations, refraction and the earth'"'"'s curvature.

Claims

1. Electro-optical distance measuring apparatus comprising:

a light source for producing a light beam signal having an intensity whch varies at a predetermined repetition rate;

a beam-splitter disposed in the path of the light beam signal for producing first and second light beams;

beam transmitting optical means disposed to receive the first beam for transmitting the first beam to a remote reflector spaced away from the apparatus the distance to be measured;

reference optical means disposed to receive the second beam for transmitting the second beam over a reference light path;

alternator means disposed in the paths of the first and second light beams for alternately and cyclically blocking and passing the first and second light beams in phase opposition;

receiver optical means disposed to receive the first light beam reflected from the reflector and the second light beam transmitted over the reference light path for producing first and second electrical signals in response to the first and second light beams respectively;

electrical circuit means coupled to said receiver optical means for generating an output signal in response to the phase relationship between the first and second electrical signals;

amplifier means having a variable amplification coupled to said receiver optical means for amplifying the first and second electrical signals by a selected amplification factor providing first and second amplified signals respectively;

range means coupled to said amplifier means for providing a first range signal in response to the first amplified signal attaining a value outside a first predetermined range and a second range in response to the second amplified signal attaining a value outside a second predetermined range, the first range being larger than and including the values of the second range;

comparator means coupled to said receiver optical means for producing a balance signal in response to a difference between the values of the first and second electrical signals;

light regulator means coupled to said comparator means for regulating the intensity of one of the first and second light beams in response to the balance signal for substantially equalizing the values of the first and second electrical signals; and

control means coupled to said range means and to said amplifier means for adjusting the variable amplification in response to the second range signal for altering the value of the second electrical signal to substantially equal a predefined value.

2. Electro-optical distance measuring apparatus as in claim 1 comprising means coupled to said electrical circuit means and to said range means for inhibiting the generation of the output signal in response to a first range signal being present.

3. Electro-optical distance measuring apparatus as in claim 2 wherein said light regulator means is coupled to said range means and is inhibited from varying the intensity of the one light beam in the presence of the first range signal.

4. A method of controlling the operation of an electro-optical distance measuring apparatus having a photo-sensitive receiver for producing first and second electrical signals in response to first and second light beams respectively, comprising the steps of:

amplifying the first and second electrical signals by a selected amplification factor;

producing a first detect signal in response to the first electrical signal attaining a value outside a first predetermined range;

producing a second detect signal in response to the second electrical signal attaining a value outside a second predetermined range, the first range being larger and including the values of the second range;

selectably regulating the intensity of one of the light beams for substantially equalizing the values of the first and second electrical signals; and

selecting the amplification factor in response to the presence of a second detect signal to alter the value of the second electrical signal to substantially equal a predefined value.

5. A method as in claim 4 comprising the steps of:

generating an output signal indicative of the measured distance in response to the phase relationship between the first and second electrical signals; and

inhibiting the generation of the output signal in response to the presence of a first detect signal.

6. A method as in claim 5 comprising the step of:

inhibiting variation of the regulation of the intensity of the one light beam in response to the presence of the first detect signal.