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Holographic system for automatic surface mapping.
Applied Optics
|February 4, 2010
Summary
This study demonstrates a holographic method for mapping large object surfaces using automatic real image following. The technique achieves high fidelity, even with pulsed lasers, enabling precise digital surface dimension output.
Area of Science:
- Optics and Photonics
- Metrology
- Computer Vision
Background:
- Accurate surface mapping of large objects is crucial for various industrial and scientific applications.
- Traditional methods can be limited in scope, precision, or speed for large-scale diffuse reflectors.
Purpose of the Study:
- To develop and demonstrate a holographic technique for automatic surface mapping of large, diffusely reflecting objects.
- To achieve high-fidelity surface dimension measurements using holographic real images.
Main Methods:
- Utilizing large aperture, low f-number holograms to achieve a shallow depth of focus for real image mapping.
- Employing a sinusoidal optical interference pattern for unambiguous focus detection and automatic focus tracking.
- Scanning the holographic real image with an image dissector on a 3-axis slide system.
- Computer analysis of video signals to control machine motion and record surface dimensions.
Main Results:
- Demonstrated successful application with both continuous wave (cw) and pulsed lasers (Q-switched ruby laser).
- Achieved unity magnification real images with a measured metric fidelity of at least 1 part in 10^4 over a 60-degree object field.
- Prototype machine successfully provided digital output of surface dimensions.
Conclusions:
- The holographic real image following technique is effective for mapping large object surfaces with high precision.
- The method is adaptable for pulsed laser applications, expanding its utility.
- Automated focus detection and computer analysis enable efficient and accurate digital surface metrology.
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