Chromatic Wide-range Microscopy for Full-Field Micro Surface Measurement
Date Issued
2011
Date
2011
Author(s)
Chiu, I-Kai
Abstract
With improvement of fabrication precision and increasing miniaturization of structure, measuring technology has become an important part in industry. non-contact measurement technology is more flexible than contact one, so it has been a trend for developing micro optical measurement technology.
The research was based on “confocal microscopy” theory. Unlike traditional confocal microscope, a pinhole of the microscopic system is replaced by the objective to filter non-axial beam and generate an area light for full-field measurement. By using innovative multi-wavelength light correlation and digital image processing, a 3D-profile can be reconstructed by taking one picture of the measured sample. However, the measuring range is only 5 μm. In order to increase the measuring range, the differential microscopy algorithm was developed in the research. After longitudinal scanning, the depth response curve of any pixel on an image can be acquired and a linear function can be obtained from a sloping side of the depth response curve. Then the 3-D profile can be reconstructed by the linear function. In addition, the microscopy can also be utilized to measure the thickness and refractive index of a transparent plate with the law of refraction.
A compact chromatic wide-range full field 3-D profilometer was developed by a halogen light source and coaxial optical configuration with a 3-chip CCD camera for individual light sensing. A vertical scanning module was invented for auto-focusing and calibration. The scanning range and accuracy of the module are 3 mm and 0.2 μm. From analysis of the measurement results, the 3-D profilometer was confirmed that the accuracy on the height measurement was 0.2 μm.
Subjects
3D Profile reconstruction
differential
chromatic
confocal
transparent plate
refractive index
Type
thesis
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