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Simultaneous real-time imaging of surface and subsurface structures from a single space-frequency multiplexed
Toshihiko Nakata1, Takanori Ninomiya
1Production Engineering Research Laboratory, Hitachi Ltd., 292 Yoshida-cho, Totsuka-ku, Yokohama 244-0817, Japan. nakata@perl.hitachi.co.jp
Applied Optics
|October 6, 2005
Summary
A novel parallel photodisplacement technique enables simultaneous real-time imaging of surface and subsurface structures. This advancement simplifies optical systems and accelerates defect detection in materials science.
Area of Science:
- Optics and Photonics
- Materials Science
- Non-Destructive Testing
Background:
- Traditional imaging techniques often require separate systems for surface and subsurface analysis.
- Optical alignment and system complexity can be significant challenges in interferometric imaging.
Purpose of the Study:
- To develop a simplified, real-time imaging technique for simultaneous surface and subsurface analysis.
- To enable rapid detection of subsurface defects using a single interferogram.
Main Methods:
- A parallel photodisplacement technique using a space-frequency multiplexed interferogram.
- Excitation of linear photodisplacement with a line-focused, intensity-modulated laser.
- Detection via a parallel heterodyne interferometer and a charge-coupled device linear image sensor.
- Optimization of control signal frequencies for orthogonal space-frequency multiplexing.
Main Results:
- Simultaneous real-time imaging of reflectivity, topography, and photodisplacement achieved.
- Demonstrated detection of subsurface lattice defects.
- Remarkable imaging speed of 0.26 seconds per 256 x 256 pixel area.
Conclusions:
- The developed technique significantly simplifies optical systems and alignment.
- It offers a promising approach for high-speed, nondestructive hybrid surface and subsurface inspection.
- Potential applications in materials analysis and quality control.