Infrared scene projector with current-mirror control electronics

• US 6,627,907 B1
• Filed: 09/29/2000
• Issued: 09/30/2003
• Est. Priority Date: 09/29/2000
• Status: Expired due to Term

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Johnson, William J., Cole, Barrett E.
• Primary Examiner(s): Lee, John R.
• Assistant Examiner(s): Kalivoda, Christopher M.
• Application Number:
  US09/675,750
• Time in Patent Office: 1,096 Days
• Field of Search: 250/495.1, 250/330, 250/455.11, 250/493.1, 250/504.R, 250/334
• 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

Abstract

Infrared scene projectors are useful in testing infrared surveillance and guidance equipment which identify and track objects, such as enemy missiles, based on their infrared emissions or heat-generation characteristics. Infrared scene projectors typically include a thermal pixel array which converts electrical input signals into a desired thermal or infrared image. One problem with conventional thermal pixel arrays is that each pixel has a unique ground voltage based on its point of connection to a ground terminal running through the array, making it difficult to precisely control the pixels. Accordingly, the present inventors devised not only innovative infrared pixel arrays and related control methods, but also infrared scene projectors incorporating them. In one exemplary pixel array, each pixel includes a resistor and a current-mirror circuit which enables control. Operating the array entails receiving a pixel-control voltage, converting the pixel-control voltage to a current, and then coupling the current to the current-mirror circuit in one of the pixels. The current mirror applies an appropriate control current to the resistor and thus enables operation of the pixel independent of ground-voltage variations.

Claims

1. An infrared scene projector comprising:

an array of two or more pixel circuits, with each pixel circuit including an infrared emitter and a current mirror coupled to the emitter;

a voltage-to-current converter having an input node and an output node, with the input node for receiving pixel-control-voltage signals and the output node for outputting a pixel-control current based on the pixel-control-voltage signal; and

a first current router for routing a current based on the pixel-control current to the current mirror in at least a first one of the pixel circuits.

2. The projector of claim 1, wherein the infrared emitter comprises a resistor.

3. The projector of claim 1, wherein the current mirror in each pixel circuit comprises:

a pixel transistor having a control node and a pair of controlled nodes, with a first one of the controlled nodes coupled to the infrared emitter; and

another transistor coupled to the pixel transistor.

4. The projector of claim 3, wherein each pixel circuit further includes:

a capacitor coupled across the control node and a second one of the controlled nodes.

5. The projector of claim 1, wherein the voltage-to-current converter comprises a pair of field-effect transistors coupled in parallel, with each field-effect transistor having a gate coupled to the input node of the converter.

6. The projector of claim 1, the first current router includes a first current mirror circuit selectively couplable to the current mirror circuit in the first one of the pixel circuits.

7. The projector of claim 1, further including a second current router coupled between the voltage-to-current converter and a second one of the pixel circuits.

8. An infrared scene projector comprising:

an array of two or more pixel circuits, with each pixel including an infrared emitter and a current mirror coupled to the emitter; and

a first current router for routing a current based on a pixel-control voltage signal to the current mirror in at least a first one of the pixel circuits.

9. The projector of claim 8, wherein the infrared emitter comprises a resistor.

10. The projector of claim 8, the first current router includes a first current mirror circuit selectively couplable to the current mirror circuit in the first one of the pixel circuits.

11. The projector of claim 8, wherein the first current mirror comprises three field-effect transistors.

12. The projector of claim 8, further including a second current router coupled between the voltage-to-current converter and a second one of the pixel circuits.

13. The projector of claim 8, further comprising a voltage-to-current converter having an input node and an output node, with the input node for receiving pixel-control-voltage signals and the output node for outputting a pixel-control current based on the pixel-control-voltage signal to the first current router.

14. An infrared scene projector comprising:

a voltage-to-current converter having an input node and an output node, with the input node for receiving pixel-control-voltage signals and the output node for outputting a pixel-control current based on the pixel-control-voltage signal; and

an array of two or more pixel circuits, with each pixel including;

an infrared emitter; and

a current mirror couplable to the output node of the voltage-to-current converter.

15. The projector of claim 14, wherein the current mirror in each pixel circuit comprises:

a pixel transistor having a control node and a pair of controlled nodes, with a first one of the controlled nodes coupled to the infrared emitter; and

another transistor coupled to the pixel transistor.

16. The projector of claim 14, wherein each pixel circuit further includes:

a capacitor coupled across the control node and a second one of the controlled nodes.

17. The projector of claim 14, further comprising:

a first current router coupled between the voltage-to-current converter and the current mirror in at least a first one of the pixel circuits.

18. The projector of claim 14, further including a second current router coupled between the voltage-to-current converter and a second one of the pixel circuits.

19. An infrared scene projector comprising:

an array of two or more pixel circuits, with each pixel circuit including an infrared emitter;

a voltage-to-current converter having an input node and an output node, with the input node for receiving pixel-control-voltage signals and the output node for outputting a pixel-control current based on the pixel-control-voltage signal; and

a first current router for routing a current based on the pixel-control current to at least a first one of the pixel circuits.

20. The projector of claim 19, wherein each pixel includes an infrared emitter and a current mirror coupled to the emitter.

21. The projector of claim 19, wherein the voltage-to-current converter comprises a pair of field-effect transistors coupled in parallel, with each field-effect transistor having a gate coupled to the input node of the converter.

22. The projector of claim 19, wherein the first current router includes a first current mirror circuit selectively couplable to the current mirror circuit in the first one of the pixel circuits.

23. The projector of claim 22, wherein the first current mirror comprises three field-effect transistors.

24. An infrared scene projector comprising:

an array of two or more pixel circuits, with each pixel including an infrared emitter; and

one or more current mirrors coupled to the infrared emitter of each of the pixel circuits.

25. The projector of claim 24, wherein each pixel circuit includes a pixel transistor having a control node and a pair of controlled nodes, with a first one of the controlled nodes coupled to the infrared emitter;

and

wherein at least one of the current mirror comprises the pixel transistor of one of the pixel circuits and another transistor coupled to the pixel transistor.

26. The projector of claim 24, wherein the other transistor is within the pixel circuit.

27. The projector of claim 24, wherein the other transistor is outside the pixel circuit.

28. The projector of claim 24, further comprising

a first current router for routing a current to one or more of the current mirrors.

29. An infrared scene projector comprising:

an input node for receiving voltage control signals;

a voltage-to-current converter circuit for converting received voltage control signals to a control current;

an array of infrared pixel circuits, each pixel circuit comprising an infrared emitter and a current-mirror circuit; and

means for routing the control current to the current mirror circuit in one of the pixel circuits.

30. An infrared scene projector comprising:

first and second supply nodes;

an array of two or more pixel circuits, with each pixel circuit comprising;

an infrared emitter having first and second emitter nodes, with the first emitter node coupled to the first supply node;

a pixel control transistor having a pixel control node and a pair of pixel controlled nodes, with the pair of controlled nodes coupled between the second emitter node and the second supply node;

a capacitor having first and second capacitor nodes, the first capacitor nodes coupled to the pixel control node and the second capacitor node coupled to one of the pixel controlled nodes;

first, second, and third transistors having respective first, second, and third control nodes and respective first, second, and third pairs of controlled nodes, with one of the first pair of controlled nodes coupled to the second capacitor node and one of the second pair of controlled nodes coupled to the first capacitor node, with the first control node coupled to the other of the first pair of controlled nodes, to the other of the second pair of controlled nodes, and to one of the third pair of controlled nodes, and with the second control node coupled the third control node; and

a voltage-current-converter having an input and an output, with the output coupled to the other of the third pair of controlled nodes; and

an input node for receiving pixel control voltages, the input node coupled to the input of the voltage-to-current converter.

31. A method for transferring or handling pixel-intensity signals in an infrared pixel array, the method comprising:

converting a pixel control voltage to a control current outside a pixel circuit;

routing a current based on the control current to the pixel circuit; and

applying a current based on the routed current to an infrared emitter in the pixel circuit.

32. The method of claim 31, wherein routing the current based on the control current to the pixel circuit comprises:

selecting the pixel circuit; and

mirroring the current to the pixel circuit in response to selecting the pixel circuit.

33. The method of claim 31, further comprising converting the routed current to a voltage across a pixel control transistor.

34. The method of claim 31, wherein converting the routed current to the pixel control voltage comprises charging a capacitor coupled to a gate of the pixel control transistor.

35. The method of claim 31, wherein applying the current based on the routed current comprises applying the current based on the routed current to two or more pixel circuits concurrently.

36. A method for transferring or handling pixel-intensity signals in an infrared pixel array, the method comprising:

converting a pixel control voltage to a control current outside a pixel circuit;

routing a current based on the control current to the pixel circuit; and

applying a current based on the routed current to an infrared emitter in the pixel circuit; and

wherein routing the current to the pixel circuit comprises;

selecting the pixel circuit; and

mirroring the current to the pixel circuit in response to selecting the pixel circuit.

37. A method for transferring or handling pixel intensity signals in an infrared pixel array, the method comprising:

converting a pixel control voltage to a control current outside a pixel circuit;

routing a current based on the control current to the pixel circuit; and

applying a current based on the routed current to an infrared emitter

wherein converting the routed current to the pixel control voltage comprises

charging a capacitor coupled to a gate of the pixel control transistor.