High-precision automatic focusing method and device with anti-noise capability based on differential confocal detection

Abstract

The invention provides a high-precision automatic focusing method and device with anti-noise capability based on differential confocal detection. The method comprises the steps: a focusing light beam is generated and combined the focusing light beam with a working light beam of an optical system through a lens group composed of a concave lens and an electric control zoom lens; the focusing light beam is reflected by a focusing plane in a focusing object, is returned via an original light path, and is reflected into a differential confocal detection mechanism by the beam splitter for light intensity measurement; in the measurement process, a high-frequency periodic change signal is biased for the electric control zoom lens, and a static differential signal measured by the differential confocal detection mechanism is converted into a dynamic differential signal with anti-noise performance; and according to the differential signal change, a feedback adjustment signal is generated, the defocusing amount is automatically compensated, and automatic focusing is realized. Static light intensity signal differential confocal detection is converted into dynamic light intensity signal differential confocal detection. Through the method, the random error of the system is reduced, the anti-noise performance of the system is improved, and the focusing precision is further improved.

Description

technical field [0001] The invention belongs to the field of optical engineering, in particular to a high-precision autofocus method and device with anti-noise capability based on differential confocal detection. Background technique [0002] Autofocus technology is an important technology applied in imaging optical system and optical processing system. Whether it is an imaging optical system or an optical processing system, before imaging or processing an object, it is necessary to accurately position the focus of the objective lens on the imaging surface or processing surface of the object. The application of autofocus technology in optical imaging system or optical processing system can well meet this requirement. [0003] The current autofocus technology includes confocal intensity detection method, imaging passive detection method, astigmatism method, spot displacement detection method, Moiré fringe method and so on. Among them, the imaging passive detection method an...

AI Technical Summary

Problems solved by technology

The spot displacement detection method is limited by factors such as the diffraction limit and detector position resolution, and the focus accuracy cannot be further improved.

The focus accuracy of the Moiré fringe method is high, but it is difficult to further improve it due to factors such as the processing accuracy of the grating and the flexible selectivity of the grating period, and the focus depth is small

The hardware implementation of the confocal intensity detection method is simple, but when the traditional single detector is used for detection, the detection accuracy is low, the feedback signal is nonlinear, and the adjustment is difficult

When the single detector is improved to dual-detector differential detection, the accuracy can be better improved, but while improving the detection accuracy, the differential system using static light intensity detection has poor anti-interference ability and is easily affected by random errors in the environment

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