Target tracking device and method
A target tracking device incorporating a Position Sensitive Detector (PSD) 1 is described. A target is illuminated by a laser of a suitable wavelength. The target reflects the laser radiation and the reflected radiation is incident on a flying vehicle carrying a target tracking device. The PSD in the device outputs a signal representative of the position of the incident laser spot. The output signal is input into control electronics, the control electronics incorporating a resistive transimpedance amplifier. A higher than usual bias voltage is applied to the PSD yielding improved pulse response of the target tracking device. Therefore, the tracking device is particularly suited for use with a target marking laser having a short pulse duration.
1. A target tracking device for a flight vehicle comprising:
a position sensitive detector for detecting radiation reflected off the target, the detector having at least two signal outputs, the signal outputs being processed by control electronics, the control electronics sampling and amplifying the impulse response of the position sensitive device such that the flight vehicle is guided toward the target; and
a voltage source that applies a bias voltage to the position sensitive detector.
2. The target tracking device according to claim 1 , in which the control electronics includes a resistive transimpedance amplifier, the amplifier sampling pulses and outputting signals representative of the position of the incident radiation on the detector.
3. The target tracking device according to claim 1 , wherein the voltage source is an external source whose bias voltage improves a temporal response of the detector.
4. A target tracking device according to claim 3 , in which the bias voltage applied to the position sensitive detector is variable in real time in response to the signal level the position sensitive detector is experiencing, thereby acting as a dynamic range control for the device.
5. The target tracking device according to claim 1 , wherein the control device extrapolates position independently of output magnitudes by suitable analysis of temporal response variation across the device.
6. The target tracking device according to claim 1 , in which the control electronics comprises AC peak detecting circuitry, for detecting the pulses output by the position sensitive detector.
7. The target tracking device according to claim 1 , comprising:
a thermoelectric cooler that maintains the position sensitive device at a constant temperature, thereby enabling operation of the device over a greater range of external environmental conditions.
8. The target tracking device according to claim 1 , comprising:
an iris of an optical lens system that constantly varies an attenuation of the incident radiation to attain an optimum signal level at the position sensitive detector.
9. The target tracking device according to claim 1 , in which the position sensitive detector is hybridised with the control circuitry to provide speed of read out advantage and reduction of noise on the signal.
10. The target tracking device according to claim 1 , wherein the voltage source is a bias generation circuit that applies a bias voltage to the position sensitive detector.
11. The target tracking device according to claim 10 , wherein the bias generation circuit is included in the control electronics.
12. A method of tracking a target comprising the steps of
(a) illuminating the target with radiation of a suitable wavelength;
(b) detecting radiation reflected or emitted by the target using a position sensitive detector;
(c) inputting the pulses output by the position sensitive detector in response to the incident radiation, into a resistive transimpedance amplifier; and
(d) analysing the data output by the amplifier using suitable control electronics, the subsequent data produced being used to alter the trajectory of a flight vehicle incident on the target.
13. The method according to claim 12 further comprising the step of analysing temporal response variation across the device such that position is extrapolated independently of output magnitudes.
14. A method of tracking a target comprising the steps of:
(a) illuminating the target with radiation of a specified wavelength;
(b) detecting radiation reflected or emitted by the target using a position sensitive detector;
(c) inputting the pulses output by the position sensitive detector in response to the incident radiation, into a resistive transimpedance amplifier; and
(d) analysing the data output by the amplifier using control electronics, wherein the data produced from the analysis is used to alter a trajectory of a flight vehicle guided towards the target.