Automatic focusing system and focusing method for microscopic Raman spectrometer

The invention provides an automatic focusing system and focusing method for a microscopic Raman spectrometer. The automatic focusing system comprises a laser, a PSD position sensor, a digital-to-analog converter, a processor, a stepping motor and an objective table; the laser emits laser to irradiate a sample on the objective table and then reflect the laser to the PSD position sensor; the PSD position sensor transmits a detected position analog signal to the digital-to-analog converter to convert the detected position analog signal into a digital signal, and the digital signal is calculated by the processor to obtain the position information of the sample; and according to the position information, a pulse is sent to the stepping motor to drive the objective table to focus. According to the invention, the PSD position sensor is utilized to realize the rapid focusing function of the microscopic Raman. Meanwhile, the response speed is high, a complex algorithm is not needed, hardware design is simple, and focu