Digital filtering of ghost signal in phase measuring deflectometry

Area of Science:

• Optical Engineering
• Metrology
• Surface Testing

Background:

• Deflectometry is a powerful optical testing technique.
• Ghost reflections are a common challenge in deflectometry, hindering accurate surface analysis.
• Existing methods for ghost reflection removal in optical testing can be complex or limited.

Purpose of the Study:

• To introduce a novel geometric screen modification method for eliminating ghost reflections in deflectometry.
• To demonstrate the effectiveness of the proposed method through simulations and experimental validation.
• To analyze the limitations of the digital masking approach for ghost reflection mitigation.

Main Methods:

• Geometric screen modification by altering the optical layout and illumination source.
• Optical raytrace simulations to predict and verify the reduction of ghost reflections.
• Experimental validation using convex and concave lens samples.

Main Results:

• Successfully bypassed the generation of ghost reflection rays by modifying the optical system geometry.
• Experimental results confirmed the removal of undesired secondary rays for both convex and concave lenses.
• The proposed method offers a flexible approach to system design for ghost reflection avoidance.

Conclusions:

• Geometric screen modification is an effective strategy for ghost reflection removal in deflectometry.
• The described technique enhances the accuracy and reliability of optical surface testing.
• Further investigation into the limitations and broader applicability of digital masking is warranted.