Laser range camera

• US 5,682,229 A
• Filed: 04/14/1995
• Issued: 10/28/1997
• Est. Priority Date: 04/14/1995
• Status: Expired due to Term

• Current Assignee: OSI Defense Systems LLC (OSI Systems Incorporated)
• Original Assignee: Schwartz Electro-Optics Incorporated
• Inventors: Wangler, Richard J.
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US08/422,755
• Time in Patent Office: 928 Days
• Field of Search: 356/5.04, 356/4.01, 356/141.1, 356/4.07, 348/31
• US Class Current: 356/4.01
• CPC Class Codes: G01S 17/14 wherein a voltage or current pulse is initiated and terminated in accordance with the pulse transmission and echo reception respectively, e.g. using counters
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/89 for mapping or imaging

Abstract

A laser range camera provides both imaging and range information using laser radar techniques. A laser transmitter having a fan shaped beam that creates a column shaped beam in a far field is scanned along a single axis within a defined field of view using an acoustical optical device. A staring focal array of multiple line receivers having a long narrow field of view by using a linear array of fiber optics receives reflected energy from the scanned scene and transfers the received information to an avalanche photo diode by bundling the linear array into a circular array for interfacing with the diode. The range and intensity of each pixel within a scene is measured using a CCD measurement system which communicates with the receiver through the electrical signals. Range is determined for each pixel of the scene using the exposure characteristics of a CCD with analog type time of flight measurements. Range and intensity data are stored on odd and even CCD elements and used to display a three dimensional range image.

Claims

1. A range camera comprising:

first light transmitting means for transmitting a series of at least one fan shaped energy beam pulse for illuminating an energy column onto a scene for reflection of the energy column from the scene, the transmitting means providing a start signal representative of a transmission of the beam pulse;

first light receiving means for receiving a portion of the energy reflected from the scene, the receiving means providing a stop signal upon receipt of the reflected energy; and

range measuring means for measuring the range between the camera and the scene, the range measuring means comprising;

second light transmitting means for transmitting an optical source light, the second light transmitting means responsive to the start and stop signals for transmitting the source light and for terminating transmission of source light, respectively; and

second light receiving means for receiving the source light from the second light transmitting means, the second light receiving means including an optical detector positioned for exposure to the source light transmitted from the second light transmitting means during a time period between the start signal and the stop signal, wherein the second light receiving means provides an electrical output signal related to an amount of exposure to the source light, the second light receiving means electrical output signal indicative of the range measurement from the camera to the scene.

2. The camera as recited in claim 1, further comprising scanning means for scanning the beam across the scene.

3. The camera as recited in claim 2, wherein the scanning means comprises an acousto-optical device responsive to a frequency synthesizer for providing the scanning.

4. The camera as recited in claim 1, wherein the first light receiving means further comprises;

optical fibers having one end positioned within a first light receiving means field of view for receiving the reflected energy from the scene, the fibers arranged into multiple fiber line sets, each line set having the one end within a line across the field of view of the first light receiving means, the line orthogonal to the fan shaped beam, the multiple sets covering the field of view; and

an optical device communicating with each fiber line set, the optical device converting a received reflected energy to an electrical signal representative of a location within the field of view and an intensity of the reflected energy for the location.

5. The camera as recited in claim 4, wherein the fibers are positioned within a matrix of 128×

128 fiber ends at the one end and each row of 1×

128 fibers is bundled for communicating with an optical receiving surface of an avalanche photo diode.

6. The camera as recited in claim 1, wherein the second light receiving means comprises a CCD having a linear response to an amount of exposure to the source light received from the second light transmitting means, wherein the CCD provides the electrical output signal in a linear relationship to the amount of exposure.

7. A range camera comprising:

first light transmitting means for transmitting a series of laser beam pulses for illuminating an energy column onto a scene and reflecting therefrom;

scanning means cooperating with the first light transmitting means for scanning the energy column across the scene;

first light receiving mean for receiving reflected beam pulses returning from the scene; and

range measuring means for measuring a range from the camera to the scene, the range measuring means comprising;

second light transmitting means responsive to a transmitted laser beam pulse, the second light transmitting means having an optical source for transmitting a source light in response to the transmitting of each laser beam pulse, the second light transmitting means further responsive to a time of receipt of the reflected beam pulse for a corresponding transmitted pulse for terminating the source light transmission from the second light transmitting means; and

second light receiving means for receiving the source light from the second light transmitting means, the second light receiving means including an optical detector positioned for exposure to the transmitted source light from the second light transmitting means, the second light receiving means providing an electrical output signal relating to an amount of exposure to the source light, the amount of exposure to the source light from the second light transmitting means and thus the output signal indicative of the range measurement from the camera to the scene.

8. The camera as recited in claim 7, wherein the second light receiving means comprises a CCD having a linear response to the amount of exposure, the CCD providing an output voltage for the output signal that has a linear relationship to the amount of exposure, and thus to the range from the camera to the scene.

9. The camera as recited in claim 7, wherein the scanning means comprises an acousto-optical deflector responsive to a frequency synthesizer for providing a beam scanning direction across the scene.

10. The camera as recited in claim 7, wherein the first light receiving means comprises;

a plurality of optical fibers, the fibers having first and second ends, each fiber having its first end positioned within a receiving means focal plane field of view for receiving the reflected beam pulses, the fibers arranged into multiple line sets, each line set having the first end within a line across the field of view of the first light receiving means, the line orthogonal to the scanned beam, the multiple sets covering the field of view, each fiber line set having the second end of its fibers bundled for communicating with an optical device; and

an optical device communicating with each fiber line set through each of the bundled line set second ends, the optical device converting a received reflected energy to an electrical signal representative of a location within the field of view and an intensity of the reflected beam for the location, for providing a set of three coordinates for each reflected beam, a first coordinate defined by the beam scanning, a second coordinate defined by the line set, and a third coordinate defined by the range measurement.