The Measurement Of Energy Distribution And Size Of Non-diffracting Spots

The optical spot measurement and analysis has been widely applied in various fields,such as micro-machining, optical storage and optical imaging. But at present the usual measurement methods are suitable only for laser beam which is gaussian distribution. The energy distribution of the optical spot affect the imaging qualities in the method of imaging by non-diffracting beam filtering, and the accurate measurement of the energy distributing can optimize the imaging system. The small non-diffracting beam spot is weak ,and it's profile and distribution may be irregular. In our experiment, a pin hole is used to scan the spot accurately in two-dimensional by flexure hinge mechanism, then the energy profiles are obtained after processing the weak current signal from photomultiplier tube. This measurement method is suitable for any spot distribution and can measure small weak spot .The micro-displacement table is a nested flexure hinge, and a pin hole which is attached to the table scans the light spot with a very short step. This method can scan the small and irregular light spot accurately. Both theoretical analysis and experimental results show that the micro-displacement table has high resolution and high displacement precision.The sampled light signal passing through the pin hole is received by a photomultiplier tube, then the signal is processed by a low noise current-to-voltage conversion and amplification circuits. This signal processing method has the characteristics of high sensitivity and low noise, so the measurement system can measure the weak spot.Some non-diffracting spot have been measured with the measuring device, and the 2-d energy profiles and 1-d energy profiles with arbitrary cross-sections have been given after processing the measurement data. The shap and size of spot is obtained by spatial data interpolation. Experiment results show that this measurement method can obtain the exact intensity distribution of the spot, and the measurement results match the theory results very closely.