Circuit for studying the spatial profile of a laser beam using a closed‐circuit television camera

A circuit for studying the laser beam spatial intensity profile using a closed‐circuit television camera (CCTV) has been developed. The camera gives an output proportional to the laser beam intensity in the form of a composite video signal. The circuit can select any scan line and the intensity variation along that line can be displayed on an oscilloscope. The circuit also generates a trigger pulse for firing the laser synchronized with the selected scan line. It can be operated in either a single‐shot or repetitive mode. The circuit can be used for both pulsed and cw lasers. The dynamic range, resolution, linearity, and accuracy of measurement all depend on the CCTV camera and the oscilloscope used. The dynamic range and resolution for our particular vidicon is limited to 5 and 12 lp/mm (line pairs/mm), respectively, for a 15‐ns excitation pulse and to 10 and 18 lp/mm for cw and long pulse signal.