Maximum Acceptable Tilt Angle for Point Autofocus Microscopy

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Abstract
The complete and accurate acquisition of geometric information forms the bedrock of maintaining high-end instrument performance and monitoring product quality. It is also a prerequisite for achieving the ‘precision’ and ‘intelligence’ that the manufacturing industry aspires to achieve. Industrial microscopes, known for their high accuracy and resolution, have become invaluable tools in the precision measurement of small components. However, these industrial microscopes often struggle to demonstrate their advantages when dealing with complex shapes or large tilt angles. This paper introduces a ray-tracing model for point autofocus microscopy, and it provides the quantified relationship formula between the maximum acceptable tilt angle and the beam offset accepted in point autofocus microscopy, then analyzing the maximum acceptable tilt angle of the objects being measured. This novel approach uses the geometric features of a high-precision reference sphere to simulate the tilt angle and displacement of the surface under investigation. The research findings show that the maximum acceptable tilt angles of a point autofocus microscope vary across different measured directions. Additionally, the extent to which the maximum acceptable tilt angles are affected by the distances of the beam offset also varies. Finally, the difference between the experiment results and the theoretical results is less than 0.5°.
Funding Information
  • National Natural Science Foundation of China (52105043, KM202210005034, PILAB2105, 2021QNRC001)
  • R&D Program of Beijing Municipal Education Commission (52105043, KM202210005034, PILAB2105, 2021QNRC001)
  • State key laboratory of precision measuring technology and instruments (Tianjin University) (52105043, KM202210005034, PILAB2105, 2021QNRC001)
  • Young Elite Scientists Sponsorship Program by CAST (52105043, KM202210005034, PILAB2105, 2021QNRC001)

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