Artificial target for automatic gain normalization

• US 4,948,964 A
• Filed: 01/14/1988
• Issued: 08/14/1990
• Est. Priority Date: 01/14/1988
• Status: Expired due to Fees

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Texas Instruments, Inc.
• Inventors: Gohlke, Mark A.
• Primary Examiner(s): FIELDS, CAROLYN
• Application Number:
  US07/143,988
• Time in Patent Office: 943 Days
• Field of Search: 250/252.1 A, 250/332, 250/334, 250/351, 250/349, 250/350, 358/113
• US Class Current: 250/350
• CPC Class Codes: G01J 5/0808 Convex mirrors
• CPC Class Codes: G01J 5/0813 Planar mirrors; Parallel phase plates
• CPC Class Codes: G01J 5/0816 using attenuators
• CPC Class Codes: G01J 5/53 Reference sources, e.g. standard lamps; Black bodies
• CPC Class Codes: H04N 25/673 by using reference sources
• 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

The disclosure relates to a system for on-line normalization of the outputs of all of the detector elements of an infrared detector wherein, during the retrace period of the scanning mirror, infrared energy from a controlled thermoelectric source is reflected first from a high reflectivity sector of a rotating mirror and then from a relatively low reflectivity sector of the rotating mirror onto the detector. The detector output for the high and low reflectivity input signals is analyzed on a channel by channel basis by software controlled hardware and the gain of each channel is then adjusted in response thereto by the software controlled hardware individually. In this manner, each channel is caused to provide the same output for an identical input thereto.

Claims

1. A gain normalization system for an infrared detector comprising:

(a) an infrared detector array composed of a plurality of infrared detector elements, each element providing an electrical output parameter corresponding to the energy level of an infrared input applied thereto;

(b) means for applying an identical signal of a first energy level and then an identical signal of a second energy level different from said first energy level to each of said detector elements; and

(c) adjusting means responsive to the electrical outputs of all of said detector elements to individually adjust the values of the output parameters from each of said detector elements;

wherein said means for applying comprises a controllable uniform temperature source and means for successively reflecting a first predetermined magnitude of the energy from said source onto said detector elements followed by reflecting a second predetermined magnitude of the energy from said source onto said detector elements, said second magnitude being different from said first magnitude.

2. A system as set forth in claim 1 wherein said means for successively reflecting comprises a movable mirror having two sectors, each sector having a different reflectivity.

3. A system as set forth in claim 1, further including a scanning mirror for transmitting an infrared scene onto said detector elements, said scanning mirror having a scanning period and a retrace period, said means for applying being operable only during said retrace period.

4. A system as set forth in claim 2, further including a scanning mirror for transmitting an infrared scene onto said detector elements, said scanning mirror having a scanning period and a retrace period, said means for applying being operable only during said retrace period.

5. A system as set forth in claim 1 wherein said adjusting means to adjust said electrical outputs further includes means responsive to said electrical outputs to control said uniform controllable temperature source.

6. A system as set forth in claim 2 wherein said adjusting means to adjust said electrical outputs further includes means responsive to said electrical outputs to control said uniform controllable temperature source.

7. A system as set forth in claim 3 wherein said adjusting means to adjust said electrical outputs further includes means responsive to said electrical outputs to control said uniform controllable temperature source.

8. A system as set forth in claim 4 wherein said adjusting means to adjust said electrical outputs further includes means responsive to said electrical outputs to control said uniform controllable temperature source.

9. A system as set forth in claim 1 further including microprocessor means responsive to the temperature of said controllable uniform temperature source and the temperature of said means for reflecting to control operation of said means responsive to the electrical outputs.

10. A system as set forth in claim 2 further including microprocessor means responsive to the temperature of said controllable uniform temperature source and the temperature of said means for reflecting to control operation of said means responsive to the electrical outputs.

11. A system as set forth in claim 3 further including microprocessor means responsive to the temperature of said controllable uniform temperature source and the temperature of said means for reflecting to control operation of said means responsive to the electrical outputs.

12. A system as set forth in claim 4 further including microprocessor means responsive to the temperature of said controllable uniform temperature source and the temperature of said means for reflecting to control operation of said means responsive to the electrical outputs.

13. A system as set forth in claim 5 further including microprocessor means responsive to the temperature of said controllable uniform temperature source and the temperature of said means for reflecting to control operation of said means responsive to the electrical outputs.

14. A system as set forth in claim 6 further including microprocessor means responsive to the temperature of said controllable uniform temperature source and the temperature of said means for reflecting to control operation of said means responsive to the electrical outputs.

15. A system as set forth in claim 7 further including microprocessor means responsive to the temperature of said controllable uniform temperature source and the temperature of said means for reflecting to control operation of said means responsive to the electrical outputs.

16. A system as set forth in claim 8 further including microprocessor means responsive to the temperature of said controllable uniform temperature source and the temperature of said means for reflecting to control operation of said means responsive to the electrical outputs.

17. A gain normalization system for an infrared detector comprising:

(a) an infrared detector array composed of a plurality of infrared detector elements, each element providing an electrical output parameter corresponding to the energy level of an infrared input applied thereto;

(b) thermal source means for providing predetermined infrared radiations; and

(c) means responsive to said infrared radiations for consecutively providing both a first reference signal and then a second reference signal different from said first reference signal to said infrared detector array.

18. A gain normalization system as set forth in claim 17 wherein said means responsive to said infrared radiations is a movable mirror having two sectors, each sector having a different reflectivity.