Brightness tracking light sensor

• US 8,860,831 B1
• Filed: 02/21/2013
• Issued: 10/14/2014
• Est. Priority Date: 02/21/2013
• Status: Active Grant

• Current Assignee: Elbit Systems of America LLC (Elbit Systems Limited)
• Original Assignee: Exelis Incorporated (L3Harris Technologies, Inc.)
• Inventors: Bowen, James Hoge, Burton, Thomas Douglas, Hines, Kevin Patrick
• Primary Examiner(s): CHEN, CHIA WEI A
• Application Number:
  US13/772,689
• Time in Patent Office: 600 Days
• Field of Search: 3482221-2291, 348/216.1, 348/217.1, 345/7, 359/629, 359/431
• US Class Current: 348/217.1
• CPC Class Codes: H04N 23/11 for generating image signals from visible and infrared light wavelengths
• CPC Class Codes: H04N 23/45 for generating image signals from two or more image sensors being of different type or operating in different modes, e.g. with a CMOS sensor for moving images in combination with a charge-coupled device [CCD] for still images
• CPC Class Codes: H04N 23/70 Circuitry for compensating brightness variation in the scene

Abstract

A brightness tracking system for an optical device includes a first imager for viewing a target of interest, a second imager for viewing the same target of interest, and a photodiode circuit. The photodiode circuit (a) measures brightness levels of the target of interest received from the first imager, and (b) controls output brightness of the second imager, based on the measured brightness levels received from the first imager.

Claims

1. An optical device comprising:

a first imager for viewing a target of interest and providing a first output image to a viewer,

a second imager for viewing the target of interest and providing an output signal,

a display for receiving the output signal and providing a second image to the viewer,

a beam splitter positioned to receive the first and second images and transmit the first and second images to the viewer, and

a photodiode circuit positioned adjacent the beam splitter for measuring brightness levels of the first output image, and providing the brightness levels to the second imager,

a blanking circuit providing a trigger for starting a blanking interval on the display,

wherein the photodiode circuit is configured to receive the trigger and start measuring the brightness levels of the first output image in synchronism to the blanking interval on the display,

wherein the second imager receives the brightness levels and, in response, controls intensity levels of the second image.

2. The optical device of claim 1 wherein

the beam splitter is positioned perpendicular to a line-of-sight of the viewer.

3. The optical device of claim 1 wherein

the beam splitter includes one of a prism and a waveguide optic.

4. The optical device of claim 1 including:

a condenser lens positioned between the beam splitter and the photodiode circuit for directing light received by the beam splitter toward the photodiode circuit.

5. The optical device of claim 1 including:

a band pass filter positioned between the beam splitter and the photodiode circuit for reducing light received from the second image.

6. The optical device of claim 1 wherein

the first imager includes an image intensification tube for a night vision goggle system.

7. The optical device of claim 1 wherein

the first imager includes a camera operating at visible wavelengths.

8. The optical device of claim 1 wherein the second imager includes a thermal camera operating at infrared wavelengths.

9. A brightness tracking system comprising:

a first imager for viewing a target of interest,

a second imager for viewing the target of interest, and

a circuit for

(a) measuring brightness levels of the target of interest received from the first imager, and

(b) controlling output brightness of the second imager, based on the measured brightness levels received from the first imager, and

wherein the second imager includes

(a) a display driver for providing an image of the target of interest on a display, and

(b) a blanking trigger for blanking the display during an interval period, and

the circuit is configured to measure the brightness levels of the target of interest in synchronism with the blanking trigger.

10. The brightness tracking system of claim 9 including a beam splitter for

(a) directing light from the first and second imagers toward a viewer, and

(b) directing light from the first and second imagers toward the circuit,

wherein the circuit is configured to measure the brightness levels of the target of interest received from the first imager.

11. The brightness tracking system of claim 10 including

a condenser lens positioned between the beam splitter and the circuit for directing light from the beam splitter toward the circuit.

12. The brightness tracking system of claim 10 including

a band pass filter positioned between the beam splitter and the circuit for reducing light from the second imager directed toward the circuit.

13. The brightness tracking system of claim 9 wherein

the second imager includes a display which directs the light from the target of interest toward the viewer, and

the circuit controls output brightness of the display.

14. The brightness tracking system of claim 13 including

a notch filter positioned between the display and the viewer for attenuating the output brightness of the second imager.

15. The brightness tracking system of claim 9 wherein

the first imager includes an image intensification tube, and

the second imager includes a thermal camera.

16. The brightness tracking system of claim 9 wherein

the circuit includes a photodiode for measuring the brightness levels of the target of interest.

17. A brightness tracking system comprising:

a first imager for viewing a target of interest,

a second imager for viewing the target of interest, and

a circuit for

(a) measuring brightness levels of the target of interest received from the first imager, and

(b) controlling output brightness of the second imager, based on the measured brightness levels received from the first imager;

a beam splitter for

(a) directing light from the first and second imagers toward a viewer, and

(b) directing light from the first and second imagers toward the circuit,

wherein the circuit is configured to measure the brightness levels of the target of interest received from the first imager;

the second imager includes a display which directs the light from the target of interest toward the viewer, and

the circuit controls output brightness of the display;

the second imager includes

(a) a display driver for providing an image of the target of interest on a display, and

(b) a blanking trigger for blanking the display during an interval period, and

the circuit is configured to measure the brightness levels of the target of interest in synchronism with the blanking trigger.