Laser imaging and ranging system using one camera

• US 5,162,861 A
• Filed: 04/01/1991
• Issued: 11/10/1992
• Est. Priority Date: 04/01/1991
• Status: Expired due to Fees

• Current Assignee: John Taboada, Tamburino, Louis A.
• Original Assignee: John Taboada, Tamburino, Louis A.
• Inventors: Taboada, John, Tamburino, Louis A.
• Primary Examiner(s): Hellner, Mark
• Application Number:
  US07/677,896
• Time in Patent Office: 589 Days
• Field of Search: 356/1, 356/2, 356/5, 356/141, 356/152, 358/108, 358/125
• US Class Current: 356/5.05
• CPC Class Codes: G01C 3/08 Use of electric radiation detectors

Abstract

A pulsed laser illumination based one camera ranging and imaging system which requires only a single axis optical aperture and is therefore suited to use on aircraft and other space and configuration limited apparatus is disclosed. The invention uses intensity coded partial images of the distant target in a single camera with the partial images being obtained by a distance segregating optical modulation arrangement which separates pixel portions according to their arrival time and thereby the distance of travel from the target. The described system uses pixel by pixel processing of the segregated images as accomplished in an image array processor, for example.

Claims

1. The method for imaging and range mapping of a distal three-dimensional object comprising the steps of:

illuminating the object with a sequence of single optical aperture sourced short duration laser energy optical pulses;

collecting a first frame plurality of object reflected laser energy optical pulses via said aperture onto the retina of an optical to electrical energy transducer device;

collecting a second frame plurality of object reflected laser energy optical pulses via said aperture onto the retina of said optical to electrical energy transducer device;

imprinting a pattern of time dependent optical intensity modulation on the reflected energy pulses of said second frame prior to their retina collection, said modulation including a ramp waveform of predetermined monotonic mathematical character extending over the time interval of target range induced signal delay variation in said reflected pulses; and

comparing the optical intensity determined electrical signals of said first and second frames on a corresponding image pixel basis to generate a sequence of range related pixel values.

2. The method of claim 1 wherein said comparing step includes computing the mathematical ratio of corresponding pixel first and second frame intensity related electrical signals.

3. The method of claim 1 wherein said time dependent intensity modulation is synchronized with the reflected laser optical pulse time following each laser energy optical pulse.

4. The method of claim 1 wherein said time dependent ramp waveform is exponential in nature.

5. The method of claim 1 wherein the ramp waveform modulates said object reflected laser energy optical pulses according to the magnitude of a squared trignometric function.

6. A single camera laser imaging and ranging system comprising the combination of:

pulse operated laser means including a bidirectional single optical aperture member for illuminating a remotely disposed object;

means including a single optical to electrical energy transducing camera member optically communicating with said object via said optical aperture for generating electrical signals representative of object image pixel optical signals;

electrical signal controllable optical modulator means disposed in the optical path intermediate said aperture and camera members for intensity modulating the target generated optical signal received by said camera member;

electrical signal waveform generator means for driving said optical modulator means into a first and second frame of pixels sequential cycle which includes first frame pixel passive optical transmission and time dependent optical intensity modulation of said second frame pixels;

electrical means for recording and mathematically manipulating the pixel signals of said first and second frames into first and second frame pixel comparison based object range signals.

7. The imaging and ranging system of claim 6 wherein said signal waveform generator means includes means for generating a monotonic ramp function having time duration relating to the time of optical signal travel over the range distance interval of said system.

8. The imaging and ranging system of claim 6 wherein said optical modulator means includes optical polarization means.

9. The imaging and ranging system of claim 8 wherein said optical polarization means includes electro-optic cells taken from the group consisting of Pockels cells and Kerr cells.

10. The imaging and ranging system of claim 6 wherein said means for recording and manipulating includes means for computing the mathematical ratio of corresponding second frame and first frame pixel signals.

11. The imaging and ranging system of claim 6 wherein said waveform generator means includes means for generating a time dependent monotonic ramped sawtooth waveform.

12. The imaging and ranging system of claim 6 wherein said laser means also includes a plurality of optical reflector elements.

13. The imaging and ranging system of claim 12 wherein said optical to electrical energy transducing camera member includes a charge coupled device semiconductor array.

14. Laser imaging and ranging apparatus comprising the combination of:

pulsed laser optical means including a single camera member and a first operating cycle portion therein for generating a full image first pixel intensity array representation of a distal target;

first electrical memory means for storing said full image first representation in image pixel organized array;

modulated optical path means including a second operating cycle portion in said camera member for generating a partial image second pixel intensity array representation of said target;

said partial image second representation including a range proportioned pixel intensity modulation relationship with respect to a full image representation of said target;

second electrical memory means for storing said partial image second representation in image pixel organization array; and

mathematical algorithm electrical circuit means for computing the range coded intensity ratio of corresponding image pixels in said first and second electrical memory means.

15. The apparatus of claim 14 wherein said modulated optical path means range proportioned pixel intensity modulation relationship includes a mathematically described ramp function.

16. The apparatus of claim 14 wherein said modulated optical path means includes optical signal polarization means and an electrically controllable Pockels cell polarization rotation member.

17. The apparatus of claim 14 wherein said modulated optical path means includes optical signal polarization means and an electrically controllable Kerr cell polarization rotation member.

18. The apparatus of claim 14 wherein said camera member first and second operating cycle portions are sequentially disposed in time.

19. The apparatus of claim 14 wherein said mathematical algorithm electrical circuit means comprises a programmed digital computer.