Optical electronic distance measuring apparatus with movable mirror

Claim 2

An electronic optical distance measuring apparatus comprising: a plurality of targets mounted on a support frame, said support frame being mounted to ground; three rangefinders arranged in a triangle and mounted on said support frame for measuring distance between said rangefinders and each of said targets, each of said rangefinders including: means for generating a modulated optical signal at a given modulation frequency; means for automatically successively transmitting the optical signal from a reference location to said plurality of targets each of which reflects the received transmitted signal; means for receiving the successively reflected signals from each of said targets at said reference location and for detecting the received signals wherein the detected signals each have a phase difference with the transmitted signal manifesting the distance between the target corresponding to that detected signal and the reference location; means for determining the phase difference between said detected signals and said transmitted signal and generating a phase difference signal for each said detected signals; and means responsive to each of said phase difference signals for automatically determining the distance from said reference location to each said targets from said determined phase difference; and at least two of said rangefinders also being aimable at each of the other rangefinders for measuring respective distances between all said rangefinders to measure said triangle thereof; and a central computer for controlling said rangefinders and effective for computing by trilateration coordinates of each of said targets based on said measured distances between said rangefinders and said targets, and based also upon coordinates of each of said rangefinders to a reference point relative to said ground.

Claim 3

The apparatus of claim 1 wherein said means for transmitting includes movable mirror means including control means for automatically directing said transmitted signal to each said plurality of targets by way of said mirrors.

Claim 4

The apparatus of claim 1 wherein said means for determining phase difference includes means for measuring phase difference from a zero point, said zero point tending to exhibit drift causing error in said determined distance, said means for transmitting including means for transmitting the optical signal to a first reference target for generating a reflected reference distance signal and means responsive to said reference distance signal applied thereto for periodically correcting for said periodic drift.

Claim 5

The apparatus of claim 3 wherein said means for determining the distance includes means responsive to the determined phase difference of said reference distance signal and said optical signal for correcting the determined distance to each said targets.

Claim 6

The apparatus of claim 2 wherein said mirror means includes a mirror, means for rotating the mirror about two orthogonal axes, means for generating a position signal manifesting the position of the mirror about said two axes, said control means including means responsive to said position signal for generating a control input signal to said means for rotating for positioning the mirror to aim the transmitted optical signal at each said plurality of targets.

Claim 7

The apparatus of claim 5 wherein the control means includes means for rotating the mirror to a next selected target of said plurality of targets during said determining said distance from a prior selected target.

Claim 8

The apparatus of claim 6 wherein said control means stops the rotation of said mirror at a selected target prior to moving the mirror to the next target.

Claim 10

The apparatus of claim 3 wherein said detected signals periodically exhibit errors due to atmospheric variations through which said optical signal propagates, said apparatus including a second target located to provide a reference signal manifesting said atmospheric variations, said apparatus including means for periodically transmitting said optical signal to said second target, said means for determining including means for correcting for said atmospheric variations in said determined distance.

Claim 11

The apparatus of claim 1 wherein the means for transmitting the optical signal includes a displacable mirror and control means for selectively displacing the mirror to transmit the optical signal to each said target in a given sequence, said mirror for receiving the reflected signal.

Claim 12

The apparatus of claim 1 wherein said means for determining distance includes means for compensating for atmospheric temperature variations by acoustic thermometry.

Claim 13

The apparatus of claim 1 wherein said means for determining phase difference includes means for generating n clock signals in a first cycle, means for producing an intermediate reference (IF) signal, means responsive to an enable input signal for generating a trigger signal every m first cycles defining a second cycle, means for mixing the received detected signal with said IF signal to produce a detected IF signal, and means responsive to said trigger signal, to said detected IF signal and to said n clock signals for generating n samples of said detected IF signal, anti means responsive to said generated n samples in said m cycles for producing said determined distance.

Claim 14

The apparatus of claim 12 wherein the targets each comprise a retroreflector, the generated n samples comprises a sequence of samples s j , and the Fourier components of the fundamental harmonic for a retroreflector i are: ##EQU3## where m=number of cycles sampled and the detected IF signal amplitude and phase are: ##EQU4##

Claim 15

The apparatus of claim 13 wherein n is >25 and m is>10.

Claim 16

The apparatus of claim 13 wherein the modulation frequency is >1 GHz.

Claim 17

An electronic optical distance measuring apparatus for automatically measuring distances to a plurality of targets comprising: a plurality of retroreflector targets mounted on a support frame, said support frame being mounted to ground; three rangefinders arranged in a triangle and mounted said support frame for measuring distance between said rangefinders and each of said targets, each of said rangefinders including: means for generating a modulated infrared signal at a given modulation frequency; means for automatically successively transmitting in a given sequence the optical signal from a reference location to each of said plurality of retroreflector targets each of which reflects the received transmitted signal to the reference location; means including a mirror at the reference location having automatically controlled different switched positions for receiving the reflected signals from each said plurality of targets at said reference location in accordance with the switched mirror position and means for detecting the received signals wherein the detected signals each have a phase difference with the transmitted signal manifesting the distance between the target corresponding to that detected signal and the reference location; means for determining the phase difference between each said detected signals and said transmitted signal and for generating a phase difference signal for each said detected signals; means responsive to said generated phase difference signals for determining the distance from said reference location to each said targets from said determined phase differences; and means for correcting said phase difference signals for errors; and at least two of said rangefinders also being aimable at each of the other rangefinders for measuring respective distances between all said rangefinders to measure said triangle thereof; and a central computer for controlling said rangefinders and effective for computing by trilateration coordinates of each of said targets based on said measured distances between said rangefinders and said targets, and based also upon coordinates of each of said rangefinders to a reference point relative to said ground.

Claim 18

An electronic optical distance measuring apparatus for automatically measuring distances to a plurality of targets comprising: a plurality of retroreflector targets mounted on a support frame, said support frame being mounted to ground; three rangefinders arranged in a triangle and mounted said support frame for measuring distance between said rangefinders and each of said targets, each of said rangefinders including: means for generating a modulated infrared signal at a given modulation frequency; means for automatically successively transmitting in a given sequence the optical signal from a reference location to each of said plurality of retroreflector targets each of which reflects the received transmitted signal to the reference location; means including a mirror at the reference location having automatically controlled different switched positions for receiving the reflected signals from each said plurality of targets at said reference location in accordance with the switched mirror position and means for detecting the received signals wherein the detected signals each have a phase difference with the transmitted signal manifesting the distance between the target corresponding to that detected signal and the reference location; means for determining the phase difference between each said detected signals and said transmitted signal and for generating a phase difference signal for each said detected signals; means responsive to said generated phase difference signals for determining the distance from said reference location to each said targets from said determined phase differences; and means for correcting said phase difference signals for errors; and at least two of said rangefinders also being aimable at each of the other rangefinders for measuring respective distances between all said rangefinders to measure said triangle thereof; and a central computer for controlling said rangefinders and effective for computing by trilateration coordinates of each of said targets based on said measured distances between said rangefinders and said targets, and based also upon coordinates of each of said rangefinders to a reference point relative to said ground.

Claim 19

The apparatus of claim 16 wherein said means for correcting the phase difference signals includes means for automatically periodically correcting said phase difference.

Claim 20

The apparatus of claim 17 including a reference retroreflector positioned at a first fixed reference distance value from said reference location, said means for correcting including determining said fixed reference distance with said means for determining the distance and comparison means for comparing the resulting determined fixed distance value with the actual distance value to said reference retroreflector and means responsive to the compared values for determining the error therebetween.

Claim 21

The apparatus of claim 16 further including means for correcting said detected received signals i:or atmospheric caused deviations in said detected received signals.

Claim 22

The apparatus of claim 19 wherein said means for correcting for atmospheric caused deviations includes a reference retroreflector spaced in ambient atmosphere from said reference location a distance value comparable approximately to at least the distance value to be determined in said ambient atmosphere, said means for determining the distance including comparison means for comparing the resulting determined distance value with the actual distance value to said reference retroreflector and means responsive to the compared values for determining the error therebetween.

Claim 23

The apparatus of claim 16 wherein said plurality of targets define a surface of revolution.

Claim 24

The apparatus of claim 21 wherein the surface of revolution is a three dimensional parabolic surface, and said targets being located in an array at the surface of said parabolic surface.

Claim 25

The apparatus of claim 21 including means at the focus of said parabolic surface for receiving radio waves incident on said parabolic surface.

Claim 26

An electronic optical distance measuring apparatus comprising: means for generating a modulated infrared (IR) signal at a given modulation frequency; a plurality of retroreflector targets mounted on a support frame, said support frame being mounted to ground; three rangefinders arranged in a triangle and mounted on said support frame for measuring distance between said rangefinders and each of said targets, each of said rangefinders including: means for automatically and successively transmitting the signal from a reference location to said plurality of retroreflector targets each of which reflects the received transmitted signal to the reference location; said means for transmitting including a movable mirror for directing said IR signal successively to each of said targets and for receiving the successively reflected signals at said reference location; means for detecting the received signals wherein the detected signals each have a phase difference relative to the transmitted signal manifesting the distance between the target corresponding to that detected signal and the reference location; means for generating a reference intermediate frequency (IF) signal at a frequency substantially less than the given frequency; means for reducing the frequency of said detected received signals to said IF frequency to produce an IF detected signal; means for determining the phase difference between each said IF detected signals and said reference IF signal and for generating a phase difference signal manifesting those differences; means responsive to each said phase difference signals for automatically determining the distance from said reference location to each said targets from said determined phase differences, said determined distance having a value tending to include errors; and means including a reference retroreflector in the ambient atmosphere responsive to said transmitted signal for generating a reference distance signal and means responsive to said generated reference distance signal for correcting said determined distance errors; and at least two of said rangefinders also being aimable at each of the other rangefinders for measuring respective distances between all said rangefinders to measure said triangle thereof; and a central computer for controlling said rangefinders and effective for computing by trilateration coordinates of each of said targets based on said measured distances between said rangefinders and said targets, and based also upon coordinates of each of said rangefinders to a reference point relative to said ground, and said central computer also being effective for adjusting coordinates of said targets to predetermined positions.

Claim 27

An electronic optical distance measuring apparatus comprising: means for generating a modulated infrared (IR) signal at a given modulation frequency; a plurality of retroreflector targets mounted on a support frame, said support frame being mounted to ground; three rangefinders arranged in a triangle and mounted on said support frame for measuring distance between said rangefinders and each of said targets, each of said rangefinders including: means for automatically and successively transmitting the signal from a reference location to said plurality of retroreflector targets each of which reflects the received transmitted signal to the reference location; said means for transmitting including a movable mirror for directing said IR signal successively to each of said targets and for receiving the successively reflected signals at said reference location; means for detecting the received signals wherein the detected signals each have a phase difference relative to the transmitted signal manifesting the distance between the target corresponding to that detected signal and the reference location; means for generating a reference intermediate frequency (IF) signal at a frequency substantially less than the given frequency; means for reducing the frequency of said detected received signals to said IF frequency to produce an IF detected signal; means for determining the phase difference between each said IF detected signals and said reference IF signal and for generating a phase difference signal manifesting those differences; means responsive to each said phase difference signals for automatically determining the distance from said reference location to each said targets from said determined phase differences, said determined distance having a value tending to include errors; and means including a reference retroreflector in the ambient atmosphere responsive to said transmitted signal for generating a reference distance signal and means responsive to said generated reference distance signal for correcting said determined distance errors; and at least two of said rangefinders also being aimable at each of the other rangefinders for measuring respective distances between all said rangefinders to measure said triangle thereof; and a central computer for controlling said rangefinders and effective for computing by trilateration coordinates of each of said targets based on said measured distances between said rangefinders and said targets, and based also upon coordinates of each of said rangefinders to a reference point relative to said ground, and said central computer also being effective for adjusting coordinates of said targets to predetermined positions.

Claim 28

The apparatus of claim 24 wherein said means for determining phase difference includes means for determining phase from a zero reference, said errors being due to drift of the zero reference, said reference retroreflector being located for providing a distance value sufficient to provide said reference distance signal.

Claim 29

The apparatus of claim 24 wherein said plurality of retroreflector targets are located in a variable ambient atmosphere such as to be subject to refractive index errors caused by such atmospheric variables, said reference retroreflector being located for providing a distance value sufficient to provide said reference distance signal, said means for correcting including means for correcting for said refractive index errors.

Claim 30

The apparatus of claim 24 wherein said rangefinders have reference locations defining a plane, and further including means for aiming the IR signal from each said rangefinder at the same retroreflector target in a given sequence and means for determining the distance to the same target from each said rangefinder reference location.

Claim 31

The apparatus of claim 27 including a local computer for controlling said mirror and for determining said distances to said same target and said central computer is responsive to said determined distances for performing said trilateration computation on said determined distances from each said plurality of rangefinders for each said targets.

Claim 32

The apparatus of claim 24 including means for displacing the mirror to a position to transmit and receive said IR signal from a given target in a first period, said means for determining the distance including means for determining said distance from a prior received reflected IR signal in a second period after said mirror has reached said position.

Claim 33

The apparatus of claim 29 including means for displacing and determining said distance in said first and second periods in a plurality of periods per second.

Claim 34

The apparatus of claim 25 wherein said means for providing said reference signal provides said reference signal at about twice per minute.

Claim 35

The apparatus of claim 26 wherein said means for providing said reference distance signal provides said reference distance signal at about once a minute.