Large area infrared scene emitter RIIC

• US 6,465,798 B1
• Filed: 09/08/1999
• Issued: 10/15/2002
• Est. Priority Date: 04/02/1999
• Status: Expired due to Term

• Current Assignee: FLIR Systems, Inc. (Teledyne Technologies Incorporated)
• Original Assignee: Indigo Systems Corporation (Telecom Eireann)
• Inventors: Hoelter, Theodore R., Woolaway, James T.
• Primary Examiner(s): ANDERSON, BRUCE C
• Application Number:
  US09/391,789
• Time in Patent Office: 1,133 Days
• Field of Search: 250/493.1, 250/495.1, 250/504.R, 250/494.1
• US Class Current: 250/495.1
• 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
• CPC Class Codes: H10N 19/00 Integrated devices, or assemblies of multiple devices, comprising at least one thermoelectric or thermomagnetic element covered by groups H10N10/00 - H10N15/00

Abstract

Analog signal voltages are updated sequentially in a first sample-and-hold circuit, while an emitter element displays a pixel of a first display frame in response to a stored analog signal voltage in an isolated parallel second sample-and-hold circuit. After all unit cells are updated, the switches are reversed for the two parallel sample-and-hold circuits, displaying a pixel of a second display frame in response to an updated stored analog signal voltage in the first sample-and-hold circuit. The operation of the two parallel circuits alternates for each sequential frame. A constant current source in the unit cell provides constant power dissipation and temperature, independent from variations in emitter element current, up to a predetermined constant current limit. For emitter element currents greater than the predetermined limit, an independent current source in the unit cell is automatically activated without involving external control logic. Modular system architecture permits large area displays, 1024×1024 emitter elements and larger, having high data throughput. All-digital signal and control logic interfaces provide versatile operation, wide dynamic range, and noise immunity.

Claims

1. A method of displaying a dynamic infrared image from a two-dimensional array of electricaly resistive infrared emitter elements, comprising:

generating a first electrical current through each said emitter element to an electrical ground terminal in response to a first stored analog signal voltage during a first frame display time;

heating said emitter element in response to said first electrical current, such that said emitter element emits a pixel of said infrared image during said first frame display time;

delivering and storing a second analog signal voltage at each of said emitter elements during said first frame display time, until said second analog signal voltages have been delivered and stored at all of said emitter elements;

transitioning from said first frame display time to a second frame display time substantially following consecutively said first frame display time;

generating a second electrical current through each said emitter element to said electrical ground terminal in response to said second stored analog signal voltage during said second frame display time; and

heating said emitter element in response to said second electrical current, such that said emitter element emits a pixel of said infrared image during said second frame display time;

wherein said first analog signal voltage remains electrically isolated from said second analog signal voltage at each of said emitter elements for all times during said first and said second frame display times.

2. The method of claim 1, wherein said transitioning occurs substantially simultaneously for all of said emitter elements.

3. The method of claim 1, further comprising:

supplying a difference electrical current bypassing said emitter element, such that the sum of said difference current and said first electrical current is substantially a predetermined constant current, independent of said first electrical current, provided that said first electrical current is no greater than said predetermined constant current; and

automatically increasing said first electrical electrical current in response to said first analog signal voltage, above said predetermined constant current.

4. The method of claim 3, wherein said predetermined constant current is selectable by a user.

5. The method of claim 4, wherein said predetermined constant current is digitally programmable.

6. A method of displaying a dynamic infrared image from a two-dimensional array of electrically resistive infrared emitter elements, comprising:

generating a first electrical current through each said emitter element in response to a first stored analog signal voltage during a first frame display time;

heating said emitter element in response to said first electrical current, such that said emitter element emits a pixel of said infrared image during said first frame display time;

supplying a second electrical current bypassing said emitter element, such that the sum of said second electrical current and said first electrical current is substantially a predetermined constant current, independent of said first electrical current, provided that said first electrical current is no greater than said predetermined constant current; and

automatically increasing said first electrical current, in response to said first analog signal voltage, above said predetermined constant current when the value of said first electrical current reaches approximately the value of said predetermined constant current.

7. The method of claim 6, wherein said predetermined constant current is selectable by a user.

8. The method of claim 7, wherein said predetermined constant current is digitally programmable.

9. An apparatus containing a two-dimensional array of infrared emitter elements coupled to a read-in-integrated-circuit, comprising:

a unit cell for each of said emitter elements, each of said unit cells having a first sample-and-hold capacitor interconnected with a signal interconnect line through a first row select switch and interconnected through a first frame enable switch with an emitter driver transistor, said emitter driver transistor having an output interconnected through said emitter element to a circuit ground node; and

a second sample-and-hold capacitor interconnected with said signal interconnect line through a second row select switch and interconnected with said emitter driver transistor through a second frame enable switch.

10. The apparatus of claim 9, further comprising:

a first electrical current source in said unit cell interconnected to said circuit ground node through a first current conducting path including said emitter element and to said circuit ground node through a second current conducting path bypassing said emitter element, such that said second current conducting path includes a conducting channel of a transistor configured to regulate electrical current; and

a second electrical current source electrically independent from said first electrical current source, said second electrical current source interconnected to said circuit ground node through said first current conducting path and said second current conducting path.

11. The apparatus of claim 10, wherein said first electrical current source is a biased transistor connected to a first voltage supply.

12. The apparatus of claim 11, wherein said second electrical current source is a biased transistor connected to a second voltage supply electrically independent from said first voltage supply.

13. The apparatus of claim 9, wherein said two dimensional array contains 1024 emitter elements in each of two substantially perpendicular directions.

14. The apparatus of claim 13, wherein said two dimensional array contains a plurality of substantially identically configured, self-contained array modules, each said array module containing 256 emitter elements in each of two substantially perpendicular directions.

15. The apparatus of claim 9, wherein all electrical data and control logic interfaces to said read-in-integrated-circuit are digital.

16. An apparatus containing a two-dimensional array of infrared emitter elements coupled to a read-in-integrated-circuit, comprising:

a unit cell for each of said emitter elements;

a first electrical current source in said unit cell interconnected to said circuit ground node through a first current conducting path including said emitter element and to said circuit ground node through a second current conducting path bypassing said emitter element, such that said second current conducting path includes a conducting channel of a transistor configured to regulate electrical current; and

a second electrical current source electrically independent from said first electrical current source, said second electrical current source interconnected to said circuit ground node through said first current conducting path and said second current conducting path.

17. The apparatus of claim 16, wherein said first electrical current source is a biased transistor connected to a first voltage supply.

18. The apparatus of claim 17, wherein said second electrical current source is a biased transistor connected to a second voltage supply electrically independent from said first voltage supply.

19. The apparatus of claim 16, wherein said two dimensional array contains 1024 emitter elements in each of two substantially perpendicular directions.

20. The apparatus of claim 19, wherein said two dimensional array contains a plurality of substantially equal sized, self-contained array modules, each said array module containing 256 emitter elements in each of two substantially perpendicular directions.

21. The apparatus of claim 16, wherein all electrical data and control logic interfaces to said read-in-integrated-circuit are digital.