# Anti-Interference Spectral Confocal Sensors Based on Line Spot

## TL;DR

This paper introduces a new line-spot-based spectral confocal sensor that improves measurement stability and accuracy for applications like battery wafer thickness and surface topography.

## Contribution

A novel line-spot-based spectral confocal sensor design using a binary diffractive lens and cylindrical lens is proposed and validated.

## Key findings

- The proposed sensor achieves a measurement range of 800 μm with a line spot length of 3.8 mm and width of 0.2 mm.
- Calibrated with a nanometer displacement stage, it reaches 30 nm resolution and 0.013 μm standard deviation in stability.
- The sensor shows significantly better dynamic stability than traditional point spectral confocal sensors.

## Abstract

Spectral confocal displacement sensors are non-contact optoelectronic sensors widely utilized for their high accuracy, speed, and ability to measure diverse surfaces. However, challenges including vibration, angular deflection, and surface quality variations can reduce sensor stability and accuracy when performing measurements such as lithium battery wafer thickness, wafer warpage, and optical component surface topography. This study proposes a line-spot-based measurement method using a binary diffractive lens and cylindrical lens with a 20× objective, and then the overall structure is simulated and optimized by using ZEMAX, which realizes a confocal measurement system with a measurement range of 800 μm, line spot length of 3.8 mm, and width of 0.2 mm. The system, calibrated with a nanometer displacement stage, achieved 30 nm resolution and significantly improved dynamic stability (standard deviation (SD) of 0.013 μm) compared to a point spectral confocal sensor (SD of 0.064 μm). The results indicate the proposed sensor exhibits improved stability during scanning measurements.