High-Index Glass Ball Retroreflectors for Measuring Lateral Positions.

Area of Science:

• Optics and Photonics
• Metrology and Measurement Science
• Computational Physics

Background:

• Contactless measurement of lateral position is crucial for various industrial and scientific applications.
• Dielectric spheres illuminated by coherent sources produce backscattered luminous signals.
• Existing theories like ray-tracing and Mie scattering are commonly used for optical simulations but may not apply to this specific scenario.

Purpose of the Study:

• To investigate the feasibility of using backscattered luminous signals from dielectric spheres for contactless lateral position sensing.
• To develop and compare novel algorithms for accurately computing the image coordinates of a target point on the sphere.
• To achieve sub-pixel accuracy in determining the lateral position of the optical target.

Main Methods:

• Application of traditional optical theories (ray-tracing, Mie scattering) to analyze backscattered signals from dielectric spheres.
• Development of two original algorithms for calculating image coordinates of a representative point on the sphere.
• Benchmarking algorithm robustness and repeatability using simulated and real images under noisy conditions and varying distances.

Main Results:

• Traditional approaches (ray-tracing, Mie scattering) were found to be unsatisfactory for predicting observed backscattered signals.
• Two novel algorithms were developed and demonstrated capability for accurate image coordinate computation.
• Both proposed algorithms achieved sub-pixel accuracy in determining the lateral position, even under noisy conditions.

Conclusions:

• Novel algorithms offer a more effective solution for contactless lateral position sensing compared to traditional optical theories.
• The developed algorithms provide robust and repeatable sub-pixel accuracy for optical target localization.
• This work presents a significant advancement in non-contact metrology for dielectric spheres.