Evaluation of a focused laser spot diameter for an optical angle sensor
This paper presents a new method for measurement of a focused laser beam diameter by using a single cell photodiode (PD) for achievement of further higher measurement sensitivity of an optical angle sensor based on laser autocollimation. The proposed method referred to as the PD edge method utilizes an edge of the PD active cell in the same manner as the conventional knife-edge method, which is often employed for the evaluation of light spot diameter. The proposed PD edge method is expected to evaluate the focused laser beam diameter without the influence of light diffraction, which is often observed in the case of knife-edge method. After a description of the proposed PD edge method, its feasibility is demonstrated throughout the experiments by using a developed prototype optical setup.