Systems and methods for active SWIR imaging using germanium receivers
An active imaging system comprising an illumination source for emitting a radiation pulse towards a target resulting in radiation reflected from the target, a receiver comprising one or more germanium photodiodes for receiving the reflected radiation, and a method for using same.
1. An active imaging system comprising:
a) an imaging system illumination source for emitting a radiation pulse towards a target resulting in reflected radiation from the target, wherein the illumination source comprises a Q-switched (QS) laser; and
b) a receiver comprising one or more germanium (Ge) photodiodes (PDs) for receiving the reflected radiation
wherein the receiver is configured to be activated for an integration period during which the dark current power of the Ge PDs does not exceed the kTC noise power of the Ge PDs and to be deactivated after the integration period ends.
2. The system of claim 1 , wherein the illumination source operates in the shortwave infrared (SWIR) spectral band.
3. The system of claim 2 , wherein the QS laser is an active QS laser.
4. The system of claim 2 , wherein the QS laser is a passive QS laser.
5. The system of claim 4 , wherein the passive QS laser comprises a saturable absorber.
6. The system of claim 5 , wherein the saturable absorber is selected from the group consisting of: Co2+:MgAl2O4, Co2+:Spinel, Co2+:ZnSe and other cobalt-doped crystals, V 3+ :YAG, doped glasses, quantum dots, semiconductor saturable absorber mirror (SESAM), and Cr4+YAG saturable absorber.
7. The system of claim 4 , further comprising a QS pulse photodetector for detecting of a radiation pulse emitted by the passive QS laser.
8. The system of claim 1 , wherein the receiver is configured to be activated at a time sufficient for the radiation pulse to travel to a target and return to the receiver.
9. The system of claim 1 , wherein the receiver produces electrical signals in response to the reflected radiation received by the Ge PDs, wherein the electrical signals are representative of imagery of the target illuminated by the radiation pulse.
10. The system of claim 9 , wherein the electrical signals are processed by one of an internal image processor or an external image processor into an image of the target.
11. The system of claim 10 , wherein the image of the target is processed to provide one or more of forward collision warning, lane departure warning, traffic sign recognition, and detection of pedestrians or oncoming vehicles.
12. A method for performing active imaging comprising:
a) releasing a light pulse by an illumination source of an imaging system comprising an active Q-switch (QS) laser;
b) after a time sufficient for the light pulse to travel to a target and return to the QS laser, activating a receiver comprising one or more Ge photodiodes (PDs) for an integration period during which a dark current power of the Ge PDs does not exceed a kTC noise power of the Ge PDs for receiving a reflected light pulse reflected from the target; and
c) deactivating the receiver after the integration period ends.
13. The method of claim 12 , wherein the illumination source operates in the shortwave infrared (SWIR) spectral band.
14. The method of claim 12 , wherein the receiver produces electrical signals in response to the reflected light pulse received by the Ge PDs wherein the electrical signals are representative of imagery of the target illuminated by the light pulse.
15. The method of claim 14 , wherein the electrical signals are processed by one of an internal image processor or an external image processor into an image of the target.
16. The method of claim 15 , wherein the image of the target is processed to provide one or more of forward collision warning, lane departure warning, traffic sign recognition, and detection of pedestrians or oncoming vehicles.
17. A method for performing active imaging comprising:
a) pumping a passive Q-switch (QS) laser comprising a saturable absorber to cause release of a light pulse when the saturable absorber is saturated;
b) detecting the release of the light pulse by a QS pulse photodetector;
c) after a time sufficient for the light pulse to travel to a target and return to the QS laser based on the detected light pulse release, activating a receiver comprising one or more germanium (Ge) photodiodes (PDs) for an integration period during which the dark current power of the Ge PDs does not exceed the kTC noise power of the Ge PDs for receiving the reflected light pulse; and
d) deactivating the receiver after the integration period ends.
18. The method of claim 17 , wherein the QS laser operates in the shortwave infrared (SWIR) spectral band.
19. The method of claim 17 , wherein the saturable absorber is selected from the group consisting of Co2+:MgAl2O4, Co2+:Spinel, Co2+:ZnSe, other cobalt-doped crystals, V 3+ :YAG, doped glasses, quantum dots, semiconductor saturable absorber mirror (SESAM) and Cr4+YAG saturable absorber.
20. The method of claim 17 , wherein the receiver produces electrical signals in response to the reflected light pulse received by the Ge PDs wherein the electrical signals are representative of imagery of the target illuminated by the light pulse.
21. The method of claim 20 , wherein the electrical signals are processed by one of an internal image processor or an external image processor into an image of the target.
22. The method of claim 21 , wherein the image of the target is processed to provide one or more of forward collision warning, lane departure warning, traffic sign recognition, and detection of pedestrians or oncoming vehicles.