Long-focus depth super-resolution secondary confocal measuring apparatus

Abstract

The invention discloses a long focal length super resolution two-time confocal measuring device, comprising a laser device, a collimation extender lens group, a polarizing beam splitter, a quarter wave plate, a super resolution filter, an adjustable stop, and a splitter, which are arranged on one optical path. The long focal length super resolution two-time confocal measuring device further comprises a data processing device for attaining and recording the optical signals detected by a point detector when a focusing objective lens is driven by a micro-drive apparatus to be different positions, and converting a plurality of optical signals of the detector into phase values via four-step phase shifting method. The invention pupil filter to compress the transverse diffraction mode of measurement light spot, and expand axial diffraction mode, thereby improving transverse resolution and expanding axial measurement range without reducing axial resolution.

Description

technical field [0001] The invention belongs to the technical field of high-resolution optical microscopic measurement, and can be applied to ultra-precise non-contact rapid and large-scale scanning measurement of three-dimensional microstructure measurement, micro-step, micro-groove line width, depth and surface shape measurement. Background technique [0002] Confocal scanning measurement is one of the important technical means to measure three-dimensional microstructure, micro-step, micro-groove line width, depth and surface shape in the fields of micro-optics, micro-mechanics and micro-electronics. The basic idea is to suppress stray light by introducing a pinhole detector, and produce axial tomography capability. The shortcoming of this technology is that the measurement sensitivity of axial response signal is not high near the quasi-focus area of ​​the measurement surface, so it is only suitable for Defocus displacement measurement. The differential confocal scanning ...

AI Technical Summary

Problems solved by technology

The basic idea is to suppress stray light by introducing a pinhole detector, and produce axial tomography capability. The shortcoming of this technology is that the measurement sensitivity of axial response signal is not high near the quasi-focus area of ​​the measurement surface, so it is only suitable for Defocus displacement measurement

However, confocal and differential confocal systems have the following problems that need to be solved urgently: First, because the principle of displacement sensing is based on the relationship between displacement and intensity, it is easily affected by factors such as light intensity fluctuations and background light interference, and the measured Differences in surface reflectance, the influence of the measured workpiece tilt and surface profile changes, introduce large measurement errors, which restricts the application of confocal measurement technology in large surface reflectance changes and surface profile measurements

However, the lateral resolution of the secondary confocal measurement based on phase-shifting interference is limited by the size of the Airy disk, and the axial response range does not exceed the axial focal depth range of the Airy disk.

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