US Government As Represented by the Secretary of the Army

USA As Represented by Secretary of the Navy

Robert S Rohde

Rudolph G Buser

Neal T Nomiyama

Suresh Chandra

Richard H Vollmerhausen

Edwin W Wentworth

Jeffrey L Ahl

J Brian Gillespie

Gregory R Osche

Jack L Kimberly, Jr

William M Decker

Robert G Branigan

The invention provides an array of standard infrared aiming lights mounted n an aircraft and used occasionally by pilots wearing infrared goggles to enhance perception of terrain features on low flying missions.

Terrain cueing

The optical cavity of the present laser has a folded optical path with a pair of reflective diffraction gratings and a gain cell in it. A disk with radially distributed perforations rotates in the optical path between the gratings and the gain cell. The laser wavelength depends upon which perforation is aligned with the slot in a slotted plate also in the optical path. The laser output consists of a sequence of different wavelength but colinear rays.

Laser for providing rapid sequence of different wavelengths

An optical receiver for a pulsed TEA laser output. The output has a high-amplitude portion followed by a lower amplitude tail; information is modulated onto the tail. For the high-amplitude output portion, a photodetector in the receiver is biased to low sensitivity; during the tail of the laser, the bias is increased to increase the photodetector sensitivity.

Modulated TEA laser receiver

Angular movements of an object are detected using a laser beam reflected m a mirror on the object and focussed on the edge of a straight edge in front of a photodetector. The same laser beam may be used with the same photodetector to simultaneously or separately form a Michaelson interferometer for detecting linear movements of the object. Alternatively, two photodetectors may be used such that linear and the combination of rotational and angular movements are detected simultaneously, and three photodetectors are used to detect simultaneously linear, rotational, and the combination of linear and rotational movements. In all embodiments, a telescope multiplies mirror movement by the magnifying power of the telescope.

Optical angular/linear motion detector

A multiple reflections interferometer (MRI) which eliminates the normal angle of incidence requirement of other interferometers, such as the standard Michelson interferometer (SMI), and allows convenient choices of interferometric sensitivities, such as exactly 100 nanometers per cycle or 10 nanometers per cycle using a helium-neon laser. The MRI has the mirror that usually receives the normal incidence beam replaced by a two-mirror wedge produce multiple reflections therein to provide greater displacement sensitivities.

Ultra-high sensitivity interferometer

The tail of a carbon-dioxide (CO.sub.2) transverse electrode discharge at mospheric pressure (TEA) laser pulse optical signal is pulse code modulated by a Pockels Cell. A modulation depth of 100% is obtained to prevent high false alarm rates under dynamic transmission conditions. The device external to the laser cavity will extend the capabilities of the CO.sub.2 TEA laser by using a tail for information transfer while preserving the gain switch spike for rangefinding. A high repetition rate is achieved using a power supply that electrically charges and discharges the Pockels Cell which, in turn, activates the polarization switch.

Pulse code modulation of laser pulse tail

A short pulse CO.sub.2 transverse electrode discharge at atmospheric pressure (TEA) laser device for ranging and target identification which uses an electro-optics Pockels Cell modulator to chop the transmitted laser beam into a train of 0.5 to 2 nanosecond pulses and a broadband receiver for observing the time broadened reflected signals that results from integration of the finite depths of the targets. Because a target has a unique three dimensional profile, the target signature may be identified by comparison with known signatures previously generated by computer simulation or field measurements. The present shortened pulse laser transmitter and a plurality of receiver field-of-view options meet the temporal and signal-to-noise requirements for pattern recognition. The device can be used to provide high accuracy target ranging along with target identification.

Short pulse CO.sub.2 laser for ranging and target identification

A high power laser interrogator with a dedicated receiver transmits a first ulse having a cryptic interrogation meassage therein which is detected by a suitable detector in a retroreceiver aboard a friendly target. At a predetermined time later, a second laser pulse, which is unmodulated, is transmitted to the friendly target. The friendly target has a laser retroreflector receiver/transponder with a modulating device therein which the cryptic interrogation message can only be decoded by a friendly target wherein the retroreflector reflects laser light only when the correct preselected cryptic interrogation message in the first pulse is detected and only during the duration of the unmodulated second pulse. The leading edge of the second pulse is detected and initates the modulation of the modulating device which allows the second pulse to pass therethrough with a preassigned intensity modulation as determined by the transponder. As intensity modulation occurs the pulse is reflected by the retroflector back through the modulator to the dedicated receiver in the laser interrogator, and if the modulation code is the same as preassigned, the target is deemed friendly but if not the target is determined to be an enemy.

Growing community of inventors

Alexandria, VA, United States of America

Robert S Rohde