High pulse repetition frequency electro-optical viewing system

• US 3,902,803 A
• Filed: 06/25/1973
• Issued: 09/02/1975
• Est. Priority Date: 02/02/1972
• Status: Expired due to Term

• Current Assignee: Louis J. Lego Jr
• Original Assignee: Louis J. Lego Jr
• Inventors: Lego, Louis J. Jr.
• Primary Examiner(s): Wilbur, Maynard R.
• Assistant Examiner(s): Buczinski, S. C.
• Application Number:
  US05/373,062
• Time in Patent Office: 799 Days
• Field of Search: 250/217SS,553 178/6.8 356/4,5 343/7.3
• US Class Current: 356/5.04
• CPC Class Codes: G01S 17/18 wherein range gates are used
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G02B 23/12 with means for image conversion or intensification

Abstract

A system is provided including a pulsed source of radiation and a gated sensor for responding to optical returns from a predetermined range. A high pulse repetition rate and short duty cycle are employed in order to obtain real time response from the receiver. The receiver is gated with a wave form having a sharp rise time to provide the capability of backlighting selected targets and improving resolution.

Claims

1. An electro-optical viewing system comprising, in combination:

illumination means adapted for pulsed operation;

photosensitive receiving means adapted for gated operation and including scanning means for sequentially reading out incremental portions of an imaged viewing area in accordance with a raster pattern which is regenerated at a predetermined frequency; and

timing means for generating a first pulse train for pulsing said illumination means and a second pulse train synchronized with said first pulse train for gating said receiving means, the repetition rate of pulses in said pulse trains being substantially in excess of the frequency at which said scanning raster pattern is regenerated such that the image at each said viewing area increment is renewed a substantial number of times during the interval between successive readouts of said increment by said scanning means.

2. The electro-optical viewing system set forth in claim 1 wherein:

said receiving means includes photosensitive image generation means having an electrical output characteristic which saturates in response to a predetermined level of input radiation; and

said illumination means includes means for fixing the amplitude of the illumination pulses at a level such that pulses reflected to said receiving means from a typical target range during said interval between successive readouts deliver a level of power to said receiving means sufficient to saturate only those areas of said image generation means illuminated by the brightest portions of the image embodied in said input radiation.

3. The electro-optical viewing system set forth in claim 1 wherein:

the repetition rate of pulses in said pulse trains Is more than 500 times greater than the regeneration frequency of said scanning raster pattern.

4. The electro-optical viewing system set forth in claim 1 wherein:

said scanning means comprises beam deflection means for moving a readout beam through a raster pattern comprising a plurality of parallel scan lines and means for blanking said beam during a blanking interval occuring after generation of each scan line, and said timing means comprises means for generating each pulse of said second pulse train during a blanking interval.

5. The electro-optical viewing system set forth in claim 1 wherein:

said scanning means comprises beam deflection means for moving a readout beam through a raster pattern comprising a plurality of parallel scan lines and means for blanking said beam during a blanking interval occuring after generation of each scan line, and said timing means comprises means for generating a pulse of said second pulse train during each of said blanking intervals.

6. The electro-optical viewing system set forth in claim 1 wherein said illumination means includes a radiation source constructed and arranged to cast an illumination beam geometrically coincident with the shape of said imaged viewing area.

7. The electro-optical viewing system set forth in claim 6 wherein said radiation source comprises:

an array of radiation emitting diodes arranged in the same aspect ratio as that of said imaged viewing area;

a rectangular quartz rod arranged to optically integrate the radiation output of said diode array; and

a lens system for projecting the output of said quartz rod onto a target area.

8. An electro-optical viewing system comprising, in combination:

a. a pulsed illuminator;

b. a gated receiver;

c. a timing unit coupled to said illuminator and said receiver and including means for sweeping said receiver at a high frequency such that said receiver provides a real time display and further including means for synchronizing the pulsing of said illuminator and the gating of said receiver within each sweep cycle, said timing unit providing a pulse repetition frequency exceeding 10 KHz; and

d. said timing unit including further means for gating said receiver and providing a receiver gate pulse having a width of less than 1 microsecond, whereby improved range resolution and foul weather response is provided.

9. A system according to claim 8 in which said timing unit includes means for generating illuminator control pulses of shorter duration than said receiver gate pulses.