Proceedings PaperAdvances In Laser Beam Profiling Using A Pyroelectric Staring Array
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Laser beam profiling measurement is a difficult task to perform. Various techniques have evolved over the past twenty years. These have ranged from intercepting the beam with a simple piece of paper and viewing it by eye to x,y scanning of the beam with a simple detector. The drawbacks of these approaches range from inaccuracy to slow capture of data. A need exists for a fast real time detector that can operate in a staring array mode. It must use a wide spectral range to cover lasers operating out of the visual waveband, particularly the middle and far infrared. High definition staring arrays operating at these w.ivelengths are only at the research phase, except one. The pyroelectric vidicon has been commercially available since the 1970's. Not often thought of as a staring array it is however, a very good one. A 16mm slice of D.T.G.S. gives a circular array of approx. 200 by 200 pixels. Spectral response is flat from ipm to 20μm when combined with a ZnSe faceplate. Signal readout is by scanning with an electron beam. These devices are used in low cost thermal imagers operating in the 8-14μm window. We have optimised the tube and camera operation to perform laser beam profiling. These changes take into account the much higher power available from a laser and have concentrated on extending dynamic range. This has lead to a peak signal to peak noise ratio of 30:1. Care has been paid to the optical path to minimise unwanted moire fringes. Maximum power for signal overload and damage threshold have been verified together with ensuring a linear transfer function in the normal operating range. Both C.W. and pulsed lasers can be accommodated. A mechanical shutter allows capture of single pulses from lasers of less than 500Hz rep rate. The research allows TV images of laser profiles. However, other means is display and analysis have been investigated. Firstly a pseudo 3D display utilising an oscilloscope providing real time, low cost performance. Secondly computer analysis of the images allows high accuracy ,nd quantitative data to be extracted. These developments permit laser profiles to be carried out as a matter of routine and at moderate cost.