IR detector system and method
View Patent ↗An Infra Red detector system and method is disclosed. There is benefit in providing signal processing functions into each pixel of a 2D focal plane IR detector for applications such as hostile target detection. The thermal characteristics of muzzle flash or a projectile and it's trajectory for example are distinguishable from background scene. A technique to add a signal detection function to normal IR detector thermal imaging operation to a standard direct inject Integrate While Read (IWR) pixel circuit and for providing target detection at extremely high data rates is described.
1. An infra red (IR) detector system comprising:
at least one comparator;
a Focal Plane Array (FPA) detector pixel, the FPA detector pixel including a circuit having a direct inject transistor, an integration capacitor, a first reset transistor, and an output source follower, the FPA detector pixel also has a skim circuit including a transistor switch connected to a terminal of the direct inject transistor, a storage capacitor connected to the transistor switch, and a second reset transistor configured to reset the storage capacitor, wherein a gate of the transistor switch is configured to receive an intermediate voltage for operating the skim circuit in a skim mode based on a bias property of the transistor switch; and
wherein the at least one comparator detects signals by comparing the signal in the storage capacitor to a reference voltage, which establishes a signal detection threshold for the at least one comparator based on average scene levels, scene offset voltages, and a comparator offset voltage,
wherein the skim circuit is configured to have an Integrate while Read function that enables in-pixel signal processing such that signals over a certain level are identified by the comparator.
2. An IR detector system according to claim 1 comprising:
a control voltage input to set a signal detection threshold of the FPA proportional to an average scene signal level.
3. An IR detector system according to claim 1 in which the skim circuit comprises:
a skim detection transistor to auto detect signals by threshold detection.
4. An IR detector system according to claim 1 in which the skim circuit is configured to receive a DC bias so that a charge can be transferred from the integration capacitor to the storage capacitor.
5. An IR detector system according to claim 1 comprising:
a comparator circuit for generating binary target detection signal information.
6. An IR detector system according to claim 1 comprising:
an output for signal detection data in a digital form.
7. A method for infra red detection in a Focal Plane Array (FPA) having the FPA detector pixel including a circuit having a direct inject transistor, an integration capacitor, a first reset transistor, and an output source follower, the FPA detector pixel also has a skim circuit including a transistor switch connected to a terminal of the direct inject transistor, a storage capacitor connected to the transistor switch, and a second reset transistor configured to reset the storage capacitor, wherein a gate of the transistor switch is configured to receive an intermediate voltage for operating the skim circuit in a skim mode based on a bias property of the transistor switch, the method comprising:
applying an intermediate voltage that is greater than a threshold voltage to the gate of the transistor switch; and
detecting a signal input to the direct inject transistor of the FPA detector pixel by comparing the signal in the storage capacitor to a reference voltage, which establishes a signal detection threshold for the at least one comparator based on average scene levels, scene offset voltages, and a comparator offset voltage.