The main focus of this analysis is on the error after calibration of spectral confocal sensors. Each sensor is measured using an interferometer and a high-precision length measuring machine, ensuring that the laser path of the spectral confocal sensor is centered on the measuring probe to guarantee the installation precision during measurement. Then, by replacing the flatness deviation, calibration of the spectral confocal sensor is performed. The measurement data is processed using the least squares method to obtain the discrete systematic errors of the measurement database. The results show that the discrete systematic error after calibration with the high-precision length measuring machine is 0.030%, and the analytical linear error during calibration with the laser interferometer is 0.038%. By using the least squares method for data processing and calculating the discrete systematic errors, the parallelism error and systematic errors of the spectral confocal sensor during calibration are reduced, improving the calibration accuracy of the spectral confocal sensor.

Keywords: Metrology; Spectral Confocal; Non-contact Measurement; Error Analysis; Calibration

As a new type of high-precision sensor, the measurement accuracy of spectral confocal sensors can reach up to ±0.02%. Initially developed in France, compared to grating scales, capacitive sensors, or inductive differential transformer displacement sensors, their advantages in displacement measurement are more pronounced. Nowadays, due to the high precision and non-contact measurement capabilities of spectral confocal sensors, their applications in geometric high-precision measurement are becoming increasingly widespread, such as measuring displacements of diffuse reflection and planar reflection surfaces, flatness measurement, thickness measurement of plastic films and transparent materials, and surface roughness measurement.

In terms of displacement measurement, since the advent of spectral confocal sensors, their fundamental function has been to measure displacement. Ma Jing et al. analyzed the scattering objective lens of spectral confocal sensors and developed the structure of the scattering objective lens, enhancing various characteristics of spectral confocal sensors; Bi Chao et al. used spectral confocal sensors to achieve high-precision and efficient measurement of the gaps in aircraft engine motor rotors. In terms of flatness measurement, Wei Hengzheng et al. analyzed the detection errors of spectral confocal sensors, and in the study of planar detection errors, they used spectral confocal sensors to measure the flatness of a circular flat crystal, obtaining the planar detection error value.

In terms of measuring the thickness of plastic films and transparent materials, Zhu Wanbin et al. explained the measurement error introduced by the different refractive indices of transparent plates when measuring the flatness of transparent plates and performed compensation; Cao Taiteng et al. based on three-dimensional data precision measurement machine vision technology, used spectral confocal sensors to detect the thickness of transparent materials and the thickness of curved glass surfaces. In terms of surface roughness measurement, Shen Xueqin et al. explained the advantages and disadvantages of different measurement methods for measuring surface roughness, ultimately choosing a measurement method based on spectral confocal sensors and conducting related experiments, providing a new method for high-precision measurement of surface roughness; Lin Jiejun et al. used the spectral confocal method to measure the surface roughness of roughness samples and explained their measurement uncertainty.

This article uses the least squares method to calculate the calibration error and performs discrete systematic error calculations, reducing the error after calibration of spectral confocal sensors, and explores the changes in the calibration error of spectral confocal sensors under different precision standards, which is of great significance for future applications and research of spectral confocal sensors.

Suzhou Chuangshi Intelligent Technology Co., Ltd. (hereinafter referred to as: Chuangshi Intelligence), is a research and technology-driven company dedicated to the development, production, sales, and after-sales of precision detection systems and high-precision laser distance-displacement sensors. The company is located in the Suzhou Wuzhong Science and Technology Park, with a team of doctors and postgraduate elites from top universities around the world. The company has applied for more than ten patents. Adhering to the principle of "technology-driven, demand-oriented, customer-first service," the company is committed to becoming a "precision measurement expert" with "Chinese own brand," willing to work with various parties to innovate and change the industrial development of high-end instruments and high-precision sensors worldwide.

TronSight Intelligence has currently launched two product series of spectral confocal displacement sensors and laser triangulation speed sensors, has established strategic partnerships with several universities and industry leaders, and is widely used in academic research, precision machinery manufacturing, 3C electronics, automotive, metal, semiconductor, new energy, and municipal testing fields. Customers have responded warmly and have received widespread acclaim.

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