Target tracking device and method

Abstract

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 including 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, amplifying and optimising the impulse response of the position sensitive device such that the flight vehicle is guided toward the target. 
     
     
         2 . A 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 . A target tracking device according to  claim 1 , in which a higher than recommended bias voltage is applied to the position sensitive detector thereby improving the temporal response of the detector and hence the effectiveness of the tracking device. 
     
     
         4 . A target tracking device according to  claim 1 , in which position is extrapolated independently of output magnitudes by suitable analysis of temporal response variation across the device. 
     
     
         5 . A 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. 
     
     
         6 . 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. 
     
     
         7 . A target tracking device according  claim 1 , in which the temperature of the position sensitive device is maintained at a constant temperature, thereby enabling operation of the device over a greater range of external environmental conditions. 
     
     
         8 . A target tracking device according to  claim 1 , in which the optimum signal level for the device is attained by constantly varying attenuation of the incident radiation via an iris or any other physical means of reducing the signal reaching the PSD. 
     
     
         9 . A target tracking device according to  claim 1 , in which the position sensitive detector could be hybridised with the control circuitry to provide speed of read out advantage and reduction of noise on the signal. 
     
     
         10 . 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.   
     
     
         11 . A method according to  claim 9  further comprising the step of analysing temporal response variation across the device such that position is extrapolated independently of output magnitudes. 
     
     
         12 . (canceled)