DISTANCE MEASURING APPARATUS

• US 3,619,058 A
• Filed: 08/24/1969
• Issued: 11/09/1971
• Est. Priority Date: 11/24/1969
• Status: Expired due to Term

• Current Assignee: Gregory Justice, William R. Hewlett
• Original Assignee: Gregory Justice, William R. Hewlett
• Inventors: Justice, Gregory, Hewlett, William R.
• Primary Examiner(s): Bennett, Jr., Rodney D.
• Assistant Examiner(s): Buczinski, S. C.
• Application Number:
  US04/879,291
• Time in Patent Office: 807 Days
• Field of Search: 324/83,86 356/5 343/7.5,13,113 250/204
• US Class Current: 356/5.12
• CPC Class Codes: G01S 17/32 using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
• CPC Class Codes: G01S 7/4811 common to transmitter and receiver
• CPC Class Codes: G01S 7/4972 Alignment of sensor

Abstract

The phase of a modulated light carrier signal that is transmitted to and reflected back from a distant reflector is compared with a reference modulated light carrier signal to provide a direct readout of distance to the reflector. The reference and reflected light carrier signals are chopped alternately and measured in a signal circuit that reconstructs the phase information on the chopped signals for continuous analysis and readout directly in distance.

Claims

1. Electro-optical distance measuring apparatus comprising:

a light source and signalling means coupled thereto for producing a light beam signal having an intensity which varies between selected values at a predetermined repetition rate;

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

beam-transmitting optical means coupled to receive the first beam for transmitting said first beam of light to a remote reflector disposed at the end of the distance to be measured;

auxiliary optical means coupled to receive the second beam for transmitting the same over an auxiliary light path;

an alternator disposed in the paths of said first and second light beams intermediate said beam-splitter and the beamtransmitting optical means and auxiliary optical means for alternately and cyclically blocking and passing the first and second light beams in phase opposition;

receiver optical means including a photoresponsive detector disposed to receive background illumination modified alternately by the first light beam signal reflected back from said reflector and by the second light beam signal transmitted over said auxiliary light path for operation of the photoresponsive detector under more nearly uniform light bias conditions over a cycle of alternator operation; and

electrical circuit means coupled to said photoresponsive detector for measuring the phase relationship between successive responses of said detector to the light beam signals alternately received thereby.

2. Electro-optical distance measuring apparatus as in claim 1 wherein:

said light source is an electroluminescent diode which is operated alternately unenergized and energized at said predetermined repetition rate; and

said receiver optical means includes an optical mixer for continuously coupling to the photoresponsive detector the background illumination and the alternating light beam signals reflected back from said reflector and transmitted over said auxiliary path.

3. Electro-optical distance measuring apparatus as in claim 2 wherein:

said light source is a gallium arsenide diode which produces light in the infrared region of the radiation spectrum when energized; and

said predetermined repetition rate is a selected multiple of one of about 2.458 kilohertz for English system of distance units and about 1.4985 kilohertz for metric system of distance units.

4. Electro-optical distance measuring apparatus as in claim 1 wherein said electrical circuit means comprises:

a plurality of digit-place selector means for providing the numerical readout in decimal form of the distance to the reflector, each of said selector means including the cardinal numbers in a decade range;

means coupled to each of said selector means for measuring said phase relationship in fixed increments per cardinal number; and

means selectably coupling each of said selector means in sequence to said signalling means for altering said predetermined repetition rate in decadic multiples from the highest repetition rate associated with the least-significant digit-place selector means to the lowest repetition rate associated with the most significant digit-place selector means to control said light source for first producing a light beam signal with intensity that varies at the highest predetermined repetition rate during selection of cardinal numbers provided by the least-significant digit-place selector means, and thereafter for producing a light beam signal with intensity that varies at successively lower decadic multiples of the highest repetition rate for each successively more-significant digit-place selector means during selection of cardinal numbers provided thereby.

5. Electro-optical distance measuring apparatus as in claim 5 wherein said electrical circuit means produces a pair of continuous wave signals which are separated in phase by a value proportional to the phase relationship between successive responses of said photoresponsive detector to the light beam signals received thereby;

and comprising means coupled to each of said selector means for producing a comparison signal having a value representative of a cardinal number provided by said selector means;

indicator means including a comparison signal input connected to receive said pair of signals for providing an indication of the relationship between the value of said phase separation and the value of a signal applied to said comparison signal input; and

switching means connected to said comparison signal input of the indicator means for applying thereto the selected combination of a comparison signal determined by a given digit-place selector means and the comparison signals determined by successively less-significant digit-place selector means decreased by successive decadic multiples corresponding to the decadic digit-place separation between a less-significant digit-place selector means and said given digit-place selector means.

6. Electrical signalling apparatus comprising:

circuit means producing first and second signals of predetermined frequency during intermittent periods that cyclically alternate at a recurrence frequency which is lower than said predetermined frequency, said first and second signals being separated in phase by a value which is to be measured;

a source of continuous wave signal having a frequency which is related by an integer factor to said predetermined frequency;

a pair of signal channels, each including a signal-controlled phase shifter connected to receive the continuous wave signal from said source, each of said phase shifters including control signal storage means connected to the control signal input thereof and including amplifier means connected to receive the output of the corresponding phase shifter;

a pair of channel selectors operating at said recurrence frequency in synchronism with the cyclically alternating intermittent periods;

a phase detector having one input and having another input connected to receive the first and second signals during the cyclically alternating intermittent periods for producing a control signal representative of the phase relationship of the signals applied thereto;

means including one of said channel selectors for applying to said one input of the phase detector alternately and cyclically selected ones of the outputs of said amplifying means; and

means including the other of said channel selectors connected to receive the control signal from said phase detector for alternately and cyclically applying control signal to the control signal storage means for each of said phase shifters during phase comparison in said phase detector of the output of one of said amplifying means with the corresponding one of the first and second signals applied to said phase detector during an intermittent period for producing at the outputs of said amplifier means a pair of continuous wave signals, each being phase-locked to the corresponding one of the first and second signals.

7. Electrical signalling apparatus as in claim 6 wherein:

said control signal storage means includes an integrator connected to supply to the corresponding phase shifter a continuous control signal having an amplitude that is cyclically determined by the control signal from said phase detector periodically applied through said other channel selector.

8. Electrical signalling apparatus for determining the phase separation of a pair of continuous wave signals, the apparatus comprising:

converter means connected to receive a pair of applied signals for producing a DC output that is proportional to the phase separation of the pair of applied signals substantially over a full cycle of phase separation;

control means manually settable at cardinal numbers over a decade range for producing a DC output proportional to the cardinal number setting of the control means;

output means connected to receive the DC outputs from said converter means and said control means for producing an indication of said DC outputs attaining a predetermined relationship to each other;

phase-shifting means for selectably shifting the phase angle of an input signal by 180* means including said phase-shifting means connected to said converter means for applying thereto a pair of continuous wave signals the phase separation between which is to be determined and for selectively shifting one of said pair or continuous wave signals by 180* with respect to the other of said pair of continuous wave signals; and

means coupling said phase-shifter means to said control means for introducing said 180-degree phase shift in response to the manual setting of said control means to predetermined ones of the cardinal numbers of the decade range for maintaining operation of said converter means substantially within the central region of its phase separation-to-DC output operating range.

9. Electrical signalling apparatus as in claim 8 wherein:

said cardinal numbers in a decade range of said control means are arranged in a first group including the numbers 0, 1, 2, 8 and 9 and in a second group including the remaining cardinal numbers of a decade range not contained in the first group; and

said phase shifting means coupled to said control means selectively introduces 180* phase shift in response to manual setting of said control means on a cardinal number in one of said groups.

10. Electrical signalling apparatus as in claim 9 comprising:

an error-sensing circuit including a logic converter connected to receive signals applied to said converter means for producing a DC logic output which varies in direct proportion to phase separation of said signals in the range from about 0* to about 180* and which varies inversely thereafter in proportion to phase separation of said signals in the range from about 180* to about 360*;

a level-sensing means connected to said logic converter and to said output means for supplying a signal thereto in response to the logic output of said logic converter attaining a selected value to alter the output indication provided by said output means independent of the values of said DC outputs supplied thereto.

11. Electrical signalling apparatus as in claim 10 wherein:

said level-sensing means supplies a signal to said output means for phase separation of signals supplied to said converter means that are represented by settings of said control means at cardinal numbers included in said first group.