Abstract A system for creating a topographical map of a terrain. The terrain is periodically illuminated by high-intensity light pulses. The light reflected by the terrain is gated in synchronism with the transmitted pulses. Accordingly, certain elevated areas will return light pulse echos which are gated out at the receiver so that dark contour lines appear on the map of the terrain. The light pulses may be generated by passing continuous light through an electronic shutter which may consist of a Pockels or Kerr cell followed by a light polarization selective element which passes light only of a certain plane of polarization. Alternatively, a mode-locked laser may be used as a light source. The light at the receiver may be similarly gated by an electronic shutter, such as a gated image converter or a Kerr cell, used in conjunction with polarizers.
The method of preparing a two-dimensional topographical map of a terrain to be mapped which comprises the steps of: a. generating intensive light pulses at a periodic and constant rate, the duration of each pulse being substantially equal to the period between two successive pulses; b. directing said light pulses toward the terrain to be mapped; c. receiving light pulses reflected by the terrain in the vicinity of the pulse generator; and d. periodically gating the received light pulses in synchronism with the transmitted light pulses and at a fixed rate, whereby a flat image of the terrain may be viewed having dark contour lines corresponding to elevational areas having a round trip time such that said returning light pulses are not received.
Claim 2
Independent Claim
123 words
The method of preparing a two-dimensional topographical map of a terrain to be mapped which comprises the steps of: a. generating intensive light pulses at a periodic and constant rate, the duration of each pulse being substantially equal to the period between two successive pulses; b. directing said light pulses toward the terrain to be mapped; c. receiving light pulses reflected by the terrain in the vicinity of the pulse generator; and d. periodically gating the received light pulses in synchronism with the transmitted light pulses and at a fixed rate, whereby a flat image of the terrain may be viewed having dark contour lines corresponding to elevational areas having a round trip time such that said returning light pulses are not received.
Claim 3
Dependent Claim
97 words
The method defined in claim 1 wherein the intensive light pulses are generated by periodically and for equal time intervals shifting the plane of polarization of a continuous light beam, passing light pulses having a first predetermined plane of polarization for directing them toward the terrain to be mapped, deflecting light pulses having the second, different plane of polarization, time delaying the deflected light pulses for a period of time equal to the time duration of a shift of the plane of polarization of the light, and recombining the deflected light pulses with the passed light pulses.