Asynchronous LADAR and imaging array
An imaging device comprises of a pixelated array of semiconductor detector elements, in which each detecting element is electrically connected to an integrated circuit, the integrated circuit of each of the pixels comprising a passive signal path and a transient signal path. The passive path provides consecutive frame or scene imaging and the transient path detects the transient electromagnetic events such as laser pulses. The transient path is electrically connected to a timing circuit, the timing circuit for determining the time-of-flight of return pulses emitted from the electromagnetic source detected by the transient signal paths. Wherein the passive path and transient path operate simultaneously enabling simultaneous passive and LADAR imaging.
1. A dual mode imaging device, the device comprising:
a pixelated array of semiconductor detector elements, wherein each pixel of the array has an integrated circuit, the integrated circuits comprising of a passive signal path and a transient signal path, wherein the active signal path triggers readout upon transient event detection;
a timing circuit electrically connected to the transient path, the timing circuit for determining the time-of-flight of pulses emitted from an electromagnetic source; and
wherein the passive path and transient path operate simultaneously, and wherein transient event detection initiates the identification of the location of, and readout of, the signaling transient signal path.
2. The device of claim 1 , wherein the pixelated array is made from a material from the group consisting of indium gallium arsenide (InGaAs), silicon (Si), mercury cadmium telluride (HgCdTe), Indium Antimony (InSb), a group III-V, II-VI super lattice, or quantum well detector, or any combinations thereof.
3. The device of claim 1 , wherein the electromagnetic source is a laser, the laser wavelength peak within the spectral range from about 180 nanometers (nm) to about 15 micrometers (μm).
4. The device of claim 1 , wherein the pixelated array is made from silicon.
5. The device of claim 4 , wherein the device circuits and detector elements are made within the same substrate.
6. The device of claim 1 , wherein each of the pixels has a dedicated time-to-analog converter.
7. The device of claim 1 , wherein the pixelated array is thinned to less than 500 microns thickness and optical radiation enters the device from the side opposite from that containing circuits.
8. The device of claim 1 , wherein the device provides gain to the optical signal through an impact ionization process within the detector material.
9. The device of claim 1 , wherein the circuits of the device are fabricated using CMOS processing.
10. The device of claim 1 , wherein the circuits of the device are fabricated in separate wafers and electrically connected.
11. The device of claim 1 , wherein the gain-bandwidth properties of the passive signal paths is adjustable, individually or in aggregate.
12. The device of claim 1 , wherein the transient signal path includes a circuit, such as a constant fraction discriminator, for correcting variations in event timing resulting from variations in signal amplitude.
13. The device of claim 1 , wherein the detector is sensitive to electromagnetic radiation regions from the group consisting the x-ray, ultraviolet, visible, near-infrared, short infrared, mid-infrared, long infrared, or combinations thereof including laser-lines within those regions.
14. The device of claim 1 , wherein the timing circuit includes a time-to-analog generator, the time-to-analog generator providing an analog-time-signature.
15. The device of claim 14 , wherein the analog-time-signature is a linear temporal function.
16. The device of claim 14 , wherein the timing circuit modifies the analog-time-signature start, profile, duration or combination thereof based on the distance to objects.
17. The device of claim 16 , wherein the time-to-analog converter delays the start of the analog-time-signature and shortens the duration of the analog-time-signature such that range data is more accurate.
18. The device of claim 16 , wherein the time-to-analog converter delays the start of the analog-time signature and alters the duration of the analog-time-signature to allow range-gating.
19. The device of claim 1 , wherein the passive paths and the transient paths are operated by a shared readout decoder block.
20. The device of claim 1 , wherein the transient signal paths of pixels are readout only if a return signal is detected.
21. The device of claim 1 , wherein the readout decoder block comprises of a plurality of sub-decoders, the sub-decoders electrically connected to sub-sections of the pixel array, the sub-decoders reading out through separate outputs from the other sub-sections of the array such that the time required to readout signals is decreased.
22. The device of claim 1 , wherein the transient signal path circuitry include digital flag readout circuitry, the digital flag circuitry operated by an address arbitration control block.
23. The device of claim 22 , wherein the operation of the row or column arbitration circuit logic is initiated by detection of an event in the transient channel of one or more of the pixels in the array.
24. The device of claim 22 , wherein the address arbitration control block reads out transient path signals based on a multi-level hierarchy of processing elements such that processing of signals occurs faster.
25. The device of claim 22 , wherein the address arbitration control block is comprised of a plurality of independent asynchronous sub-arbitrators electrically connected to different portions of the pixel array for the purpose of reducing the time required to determine address locations of pixels detecting events.
26. The device of claim 22 , wherein the logic of the row or column arbitration circuits is sequenced continually while the device is imaging.
27. The device of claim 22 , wherein one or more pixel elements are readout from the passive path signal based on the address of events detected in the address arbitration control.
28. The device of claim 1 , the device further comprising of a reference photodetector, the reference photodetector providing a time-base reference of electromagnetic pulses.
29. The device of claim 1 , wherein the transient path detection threshold level is adjustable.
30. The device of claim 29 , wherein the detection threshold level is adjusted based on the distance to objects in the field-of-view of the device.
31. The device of claim 1 , wherein the imaging device further comprises a controller.
32. The device of claim 31 , wherein the data from both the transient paths and the passive paths are used to track a target emitting or reflecting electromagnetic radiation.
33. The device of claim 31 , where in the controller allows a plurality of programmable operating modes, the modes determining the row and column origin and end readout of pixels in either the passive or transient signal path.
34. The device of claim 31 , wherein one or more symbols are superimposed at one or more addresses of a display of the passive path information, wherein the symbols correspond to the range deduced for objects detected in the respective active path at that address.