Optical electronic distance measuring apparatus with movable mirror

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.

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.