Front-End Circuit for Photomultiplier Tube Signal Readout Based on Recognition of Traffic Signal Images

Abstract

Photoelectric sensing technology plays a crucial role in vehicular equipment, which is equipped with various photoelectric devices to perceive the surrounding environment and avoid traffic lights and vehicles. This research selects the Hamamatsu H9500, a 256-channel, position-sensitive photomultiplier tube, as the test unit. It aims to simplify signal readout while improving the spatial resolution of the photodetector. This research focuses on designing a charge distribution circuit named Discretized Positioning Circuit (DPC) for the photomultiplier tube, with an additional charge-sensitive front-end amplification and shaping circuit. This circuit can convert the weak current signals from the H9500 into voltage signals. The shaping part of the circuit employs an active CR-RC circuit with weak signal amplification capabilities. This circuit is deployed within the photomultiplier tube, strategically positioned on vehicles to recognize various traffic sign images. The front-end shaping circuit is tested in the experiments, which converts square wave voltage into pulse current using a capacitor. It is observed that the current signal has a certain width and the voltage waveform of the CR differential circuit can be obtained by increasing the input impedance to 1 MΩ. During input voltage amplitude testing, the corrected output signal voltage shows a good linear relationship with the input square wave voltage. This designed front-end shaping circuit is used for signal readout in photomultiplier tubes and deployed in vehicular equipment to collect image information of traffic signs. After image processing, satisfactory recognition results are achieved.