Multi-functional day/night observation, ranging, and sighting device with active optical target acquisition and method of its operation

• US 5,973,315 A
• Filed: 02/18/1998
• Issued: 10/26/1999
• Est. Priority Date: 02/18/1998
• Status: Expired due to Term

• Current Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Litton Systems Incorporated (Northrop Grumman Corporation)
• Inventors: Epperson, Michael Charles, Saldana, Michael R., Porter, Jerry Dayton
• Primary Examiner(s): Lee, John R.
• Application Number:
  US09/025,165
• Time in Patent Office: 615 Days
• Field of Search: 250/214 VT, 250/214 AL, 250/214 R, 250/207, 313/523, 313/529, 313/537, 313/103 CM, 313/105 CM, 313/324, 313/525, 313/526, 313/527, 313/528, 315/158, 315/159, 315/307, 348/216, 348/217, 359/353, 359/356, 359/400, 359/419
• US Class Current: 250/214.0VT
• CPC Class Codes: F41G 3/06 with rangefinder rangefinders per se G01C
• CPC Class Codes: F41G 3/165 using a TV-monitor
• CPC Class Codes: H01J 2231/50015 Light
• CPC Class Codes: H01J 2231/50063 Optical
• CPC Class Codes: H01J 29/98 Circuit arrangements not adapted to a particular application of the tube and not otherwise provided for

Abstract

A multi-function day/night observation, ranging, and sighting device with active acquisition of optical targets includes a single objective lens and a single eyepiece lens and provides an image of a scene. The single objective lens leads to a visible-light first optical path and to an invisible-light second optical path. The invisible-light second optical path includes an image intensifier tube providing a visible image. The first and second optical paths converge with visible images provided by each pathway being overlaid at a reticule plane. A single light path leads from the reticule plane to the eyepiece lens. A laser provides pulses of laser light projected into the scene via the single objective lens, and the image intensifier tube is used as a detector for a portion of the laser light pulses reflected from an object in the scene in order to provide both a laser range finding function and an active optical target acquisition mode. The device includes a light-emitting display visible through the eyepiece lens providing ranging information superimposed over the image of the scene as seen by a user of the device. Methods of the device'"'"'s operation are also disclosed.

Claims

1. A viewing device having an objective lens receiving light from a distant scene, an image intensifier tube receiving the light and responsively providing a visible image, and an eyepiece lens presenting the visible image to a user of the device;

a laser projecting pulses of laser light into the scene, and circuit means for gating operation of the image tube in time-delayed synchronization with the pulses of laser light to provide an image of a retro-reflective object in the scene;

the circuit means including means for gating the image tube at a rate sufficiently high to provide an image of the scene which is substantially free of flicker, and for operating the laser at an effective pulse repetition rate sufficiently slow that the retro-reflective object in the scene does flicker;

whereby the retro-reflective object appears as a blinking source of illumination in the scene.

2. A method of operating a viewing device having an objective lens receiving light from a distant scene, an image intensifier tube receiving the light and responsively providing a visible image, and an eyepiece lens presenting the visible image to a user of the device;

a laser projecting pulses of laser light into the scene, and circuit means for gating operation of the image tube on and off in time-delayed synchronization with the pulses of laser light to provide an image of the scene;

the method including steps of;

providing circuit means for gating the image tube at a rate sufficiently high to provide an image of the scene which is substantially free of flicker, and

providing time control signal means for operating the laser to provide the laser light pulses at an effective pulse repetition rate sufficiently slow that a retro-reflective object in the scene does flicker and appears as a blinking source of illumination.

3. A circuit for a viewing device having an image intensifier tube with a photocathode, a microchannel plate, and an output electrode, said circuit comprising:

a first voltage supply for providing a voltage to said photocathode;

a first switch controlling connection of said photocathode with said first voltage supply;

a second voltage supply for providing a variable differential voltage across said microchannel plate;

a third voltage supply for providing a fixed high-gain voltage across said microchannel plate;

a second switch controlling connection of said microchannel plate with said third voltage supply;

a laser for controllably producing a pulse of laser light; and

a timing signal generator controlling opening and closing of said first and second switches and operation of said laser to produce pulses of laser light in timed relationship with connection of said first voltage supply to said photocathode and of said third voltage supply to said microchannel plate respectively.

4. The circuit of claim 3 further including a fourth voltage supply for providing a fixed lower voltage for connection to said photocathode, and a third switch controlling connection of said fourth voltage supply to said photocathode.

5. The circuit of claim 3 further including a high-resistance connection from said first voltage supply to said photocathode in parallel connection with said first switch.

6. The circuit of claim 3 including a sensor for providing a T0 signal upon said laser providing a pulse of laser light, an amplifier for providing a Tstop signal upon said image intensifier tube receiving a reflected portion of a laser pulse, a timer starting upon said T0 signal and stopping upon said Tstop signal to provide a time interval measurement, and a calculator providing a range output in response to said time interval measurement.

7. The circuit of claim 3 further including a manual input device for altering said variable differential voltage provided by said second voltage supply.

8. A day/night imaging device comprising:

an objective lens receiving light from a distant scene;

an eyepiece lens providing an image of the distant scene;

an image intensifier tube receiving light via said objective lens and responsively providing a visible image available at said eyepiece lens;

a power supply circuit selectively providing in a first mode of operation a variable differential voltage from a first microchannel plate voltage converter to a microchannel plate of the image intensifier tube, said power in a second mode of operation said power supply circuit alternatingly supplying differing voltage levels from a pair of photocathode voltage converters in a duty cycle to a photocathode of the image intensifier tube;

said power supply circuit further including a timing signal generator for connecting said first microchannel plate voltage converter and said pair of photocathode voltage converters to said microchannel plate and to said photocathode respectively in timed relationship.

9. The device of claim 8 further including manually-adjustable means for allowing a user of the device to adjust said duty cycle.

10. The device of claim 8 further including an automatic brightness control circuit effective to reduce said differential voltage in response to a current signal from said image intensifier tube.

11. The device of claim 8 further including another voltage converter circuit for supplying a constant high-gain voltage across said microchannel plate.

12. The device of claim 8 further including a laser light source for projecting timed pulses of laser light into the scene, and a timing control connection from said timing signal generator for controlling projection of laser light pulses from said laser.

13. The device of claim 10 further including a laser range finder control logic circuit, said laser range finder control logic circuit having an input to said microchannel plate voltage converter circuit effective upon operation of a laser range finding command signal to temporarily discontinue reduction of said differential voltage on said microchannel plate during a certain time interval.

14. The device of claim 13 wherein said laser range finder control logic circuit includes a microprocessor-based circuit implementing a high-speed timer, and a range calculator for laser range finding operations by use of said pulse of laser light.

15. A day/night viewer apparatus, said apparatus comprising:

an image intensifier tube providing an image having a brightness level;

a laser providing pulses of laser light projected into and illuminating said scene;

a power supply circuit for said image intensifier tube, said power supply circuit including a pair of alternative means for controlling brightness of said image provided by said image intensifier tube, one of said alternative means being operational in a day-time imaging mode, and the other of said alternative means being operational in a night-time imaging mode, respectively;

said one alternative means of said pair including a microchannel plate voltage converter circuit providing a differential voltage on a microchannel plate of said image intensifier tube, and a control circuit responsive to a current level from said image intensifier tube to control image brightness of said tube by selective reduction of said differential voltage, another voltage converter circuit providing a high-gain differential voltage across said microchannel plate, and a switch controlling connection of said another voltage converter circuit to said microchannel plate;

said other alternative means of said pair including a pair of photocathode voltage converter circuits, one of said pair of photocathode voltage converter circuits providing a negative voltage and the other providing a voltage which is positive relative to a first face of said microchannel plate, a switching network alternating connection of said photocathode of said image intensifier tube between said pair of voltage converter circuits in a duty cycle; and

a timing signal generator controlling opening and closing of said switch and of said switching network and of operation of said laser to produce pulses of laser light in timed relationship with connection of said photocathode voltage converter circuit to said photocathode and of said microchannel plate voltage converter circuit and of said another microchannel plate voltage converter circuit to said microchannel plate respectively.

16. A method of operating a viewing device in order to provide a highly conspicuous image of a retro-reflective object in a scene, said method comprising steps of:

providing an image intensifier tube receiving light from the scene and responsively providing a visible image;

utilizing a laser to project repetitive pulses of laser light into the scene;

providing circuit means for gating operation of the image tube on and off to provide an image of the scene which is substantially free of flicker;

providing the laser light pulses at a pulse repetition rate sufficiently slow that a retro-reflective object in the scene does visibly flicker;

whereby said retro-reflective object appears as a blinking source of illumination in said scene.