Integrated night vision device and laser range finder

• US 6,121,600 A
• Filed: 07/28/1997
• Issued: 09/19/2000
• Est. Priority Date: 07/28/1997
• Status: Expired due to Term

• Current Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Litton Systems Incorporated (Northrop Grumman Corporation)
• Inventors: Doster, Rodney Lynn, Estrera, Joseph Paul, Morley, Roland M., Saldana, Michael R.
• Primary Examiner(s): Allen, Stephone B.
• Application Number:
  US08/901,423
• Time in Patent Office: 1,149 Days
• Field of Search: 250/214 VT, 313/103 CM, 313/105 CM, 356/5.01, 356/5.03, 356/5.05, 356/5.04
• US Class Current: 250/214.0VT
• CPC Class Codes: G01S 17/86 Combinations of lidar systems with systems other than lidar, radar or sonar, e.g. with direction finders
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/481 Constructional features, e.g. arrangements of optical elements
• CPC Class Codes: H01J 31/507 using a large number of channels, e.g. microchannel plates
• CPC Class Codes: H04N 23/21 from near infrared [NIR] radiation
• CPC Class Codes: H04N 5/33 Transforming infrared radiation cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20

Abstract

An integrated night vision device and laser range finder provides both night-time and day-time imaging by use of an image intensifier tube, as well as providing laser range finding operations both day and night. In a laser range finder mode of operation the device projects a pulse of laser light into a scene being viewed, and a power supply and laser range finder circuit of the device temporarily utilizes the image intensifier tube as a sensor to detect reflected laser light. During laser range finding, imaging is cut off for a very short time interval. Also, during imaging operations, the power supply and laser range finder circuit operates the image intensifier tube in a unique way in order to provide both improved automatic brightness control (ABC) and improved bright-source protection (BSP). The ABC and BSP functions are coordinated with the laser range finding function in order to prevent interference by the ABC or BSP functions with laser range finding operations.

Claims

1. A method of operating a night vision device in order to provide both a visible image using ambient light and range finding using a projected pulse of laser light, said method comprising steps of:

providing the device with an image intensifier tube, and directing ambient light from a scene to the image intensifier tube;

causing the image intensifier tube to responsively provide a visible image of the scene;

projecting a pulse of laser light into the scene, and causing a portion of this pulse of laser light to be reflected from an object in the scene to the image intensifier tube;

in response to the reflected portion of the pulse of light causing said image intensifier tube to provide an electrical output; and

measuring a time interval between projection of said pulse of light and said electrical output indicative of a range from the device to the object.

2. The method of claim 1 further including the step of determining the range between the device and the object using the speed of light as a measuring standard.

3. The method of claim 2 wherein measuring the time interval includes steps of starting a timer upon projection of said pulse of light, and stopping said timer in response to said electrical output from said image intensifier tube.

4. The method of claim 2 further including the step of presenting the range in numerical form to a user of the device.

5. A method of using an image intensifier tube to both provide an image of a scene using ambient light and to measure a range to an object, said method comprising steps of:

utilizing ambient light to cause the image intensifier tube to provide a visible image of the scene,

projecting a pulse of light to the object and causing a portion of this pulse of light to be reflected from the object to the image intensifier tube;

utilizing said image intensifier tube to provide an electrical output in response to receipt of the reflected light;

measuring a time interval from projection of said pulse of light until provision of said electrical output by said image intensifier tube; and

from said time interval determining the range to the object using the speed of light as a measuring standard.

6. The method of claim 5 further including the steps of preparing said image intensifier tube to provide the electrical output by applying a determined high-gain voltage across a microchannel plate of the image intensifier tube preparatory to provision of said electrical output.

7. The method of claim 5 further including the steps of preparing said image intensifier tube to provide the electrical output by first applying a relative positive voltage to a photocathode of the image intensifier tube during projection of said pulse of light, and thereafter applying a constant negative voltage to the photocathode during receipt of reflected light at the image intensifier tube.

8. The method of claim 5 further including the steps of preparing said image intensifier tube to receive reflected light by interposing a spatial filter having a central aperture therein between said object and said image intensifier tube.

9. The method of claim 5 further including the steps of using light of a particular wavelength band to form said light pulse and preparing said image intensifier tube to receive reflected light by interposing between said object and said image intensifier tube an optical band-pass notch filter substantially allowing passage only of light of substantially the same wavelength as the projected light pulse while significantly blocking light of other wavelengths.

10. A method of determining a range from a location to an object comprising steps of:

projecting a pulse of light from the location to the object via an objective lens and causing a portion of this pulse of light to be reflected from the object back to the location and through the objective lens;

providing an image intensifier tube at the location;

utilizing said image intensifier tube to provide a visible image from light received via said objective lens and to provide an electrical output in response to receipt of the reflected light pulse portion;

measuring a time interval from projection of said pulse of light until provision of said electrical output by said image intensifier tube; and

from said time interval determining the range from the location to the object using the speed of light as a measuring standard.

11. A laser range finder and night vision apparatus, said apparatus comprising:

a laser light source for projecting a pulse of laser light from the apparatus toward an object the range to which is to be determined, a portion of the projected laser light illuminating the object and being reflected back toward the apparatus;

an image intensifier tube receiving reflected laser light from the object and responsively providing an electrical output;

said image intensifier tube also providing a visible image of the object and a scene in which said object is located;

a timer device for measuring a time interval from projection of said pulse of laser light until provision of said electrical output by said image intensifier tube; and

a calculator determining the range from the apparatus to the object using said time interval and the speed of light as a measuring standard.

12. The laser range finder of claim 11 further including:

an objective lens receiving light from a scene and directing this light to said image intensifier tube, said image intensifier tube responsively providing a visible image of the scene, and an eyepiece lens providing said visible image to a user of the apparatus.

13. A night vision device comprising:

an objective lens receiving ambient light from a scene;

an image intensifier tube receiving ambient light from the scene via the objective lens and responsively providing a visible image of the scene,

an eyepiece lens providing the visible image to a user of the night vision device;

a laser projecting a pulse of laser light into the scene, a portion of this pulse of laser light reflecting from an object in the scene to provide a reflected laser light pulse;

circuit means causing said image intensifier tube to provide an electrical output in response to receipt of said reflected laser light pulse;

a timer measuring an interval from the time of projection of said pulse of laser light until the time of provision of said electrical output by said image intensifier tube;

a calculator determining range information indicative of the distance from the night vision device to the object using said time interval and the speed of light as a measuring standard; and

means for providing said range information to a user of the device.

14. An integrated night vision device and laser range finder including an image intensifier tube and providing a visible image of a scene and range to an object in the scene, said device comprising:

an image tube power supply section providing respective operating voltage levels for each of;

a photocathode, respective first and a second facial electrodes of a microchannel plate, and an output electrode of the image intensifier tube;

an operator-input device for laser range finding, said operator-input device receiving an operator'"'"'s command to perform a laser range finding (LRF) operation;

a laser providing a laser light pulse projecting into the scene to illuminate the object;

a time-zero detector responsive to projection of said laser light pulse to provide a time-zero output signal;

an interval timer starting in response to the time-zero output signal;

a laser range finding control logic unit for providing operating control commands to said image tube power supply section to in response to a LRF command momentarily suspend imaging operation, and charging the microchannel plate of said image intensifier tube to a high-gain voltage differential between said first and second facial electrodes;

an electrical connection to said output electrode to detect an impulse current indicative of reflected laser light returning to said image intensifier tube from an object in the scene; and

an output device responsive to detection of said impulse current to provide a time-stop command to said interval timer thus measuring a time interval; and

a calculator using said time interval and the speed of light as a measuring standard to determine range to the object.

15. The integrated night vision device and laser range finder of claim 14 further including an actuator moving a filter into an optical pathway leading from the scene to the image intensifier tube in response to a LRF command.

16. The integrated night vision device and laser range finder of claim 15 wherein said filter includes a spatial filter.

17. The integrated night vision device and laser range finder of claim 15 further including an optical spectral band-pass notch filter movable into said optical pathway.

18. A combined night vision and laser range finder device, said device comprising:

an objective lens through which light from a scene being viewed is received, said objective lens directing light from the scene to an image intensifier tube providing a visible image of the scene;

a laser light source projecting a pulse of laser light outwardly through said objective lens in to the scene being viewed;

said image intensifier tube receiving reflected laser light from the object and responsively providing an electrical output; and

means for measuring a time interval from projection of said pulse of laser light until provision of said electrical output by said image intensifier tube; and

for calculating the range from the device to the object using the speed of light as a measuring standard.

19. A method of using an image intensifier tube to alternatingly provide a visible image and an electrical output pulse signal which signal is indicative of a time of receipt of a pulse of reflected laser light, said visible image having a brightness level, said method comprising steps of:

during provision of a visible image with said image intensifier tube, controlling the brightness of said image by control of one or more of the voltage levels applied to a photocathode of the image intensifier tube, and as a voltage differential across a microchannel plate of the image intensifier tube;

preparing the image intensifier tube to alternatively provide said electrical output pulse signal by charging said photocathode to a selected high-response voltage level, and also providing a certain high-gain voltage differential across said microchannel plate;

utilizing the image intensifier tube so prepared to produce said electrical output pulse signal from an output electrode of the image intensifier tube; and

subsequently to production of said electrical output pulse signal, returning said voltage levels substantially to their values existing before preparation of the image intensifier tube to provide the electrical output pulse signal.

20. The method of claim 19 further including the step of effecting a hard turn off of the photocathode of the image intensifier tube prior to charging of said photocathode to said selected high-response voltage level.

21. The method of claim 20 wherein said step of effecting a hard turn off of said photocathode includes the step of conducting said photocathode to a voltage source having a positive value relative to a first face of the microchannel plate.

22. The method of claim 21 wherein said positive voltage level is about +30 volts relative to the first face of the microchannel plate.

23. The method of claim 19 wherein said selected high-gain voltage level for said photocathode is about -800 volts.