• Journal of Korea Multimedia Society
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• v.21 no.8
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• pp.864-875
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• 2018

In this paper, we propose a measurement method for height of white light scanning interferometer using deep learning. In order to measure the fine surface shape, a three-dimensional surface shape measurement technique is required. A typical example is a white light scanning interferometer. In order to calculate the surface shape from the measurement image of the white light scanning interferometer, the height of each pixel must be calculated. In this paper, we propose a neural network for height calculation and use virtual data generation method to train this neural network. The accuracy was measured by inputting 57 actual data to the neural network which had completed the learning. We propose two new functions for accuracy measurement. We have analyzed the cases where there are many errors among the accuracy calculation values, and it is confirmed that there are many errors when there is no interference fringe or outside the learned range. We confirmed that the proposed neural network works correctly in most cases. We expect better results if we improve the way we generate learning data.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.63-64
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• 2007

• Journal of the Optical Society of Korea
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• v.18 no.5
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• pp.531-537
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• 2014

Through-silicon vias (TSVs) are fine, deep holes fabricated for connecting vertically stacked wafers during three-dimensional packaging of semiconductors. Measurement of the TSV geometry is very important because TSVs that are not manufactured as designed can cause many problems, and measuring the critical dimension (CD) of TSVs becomes more and more important, along with depth measurement. Applying white-light scanning interferometry to TSV measurement, especially the bottom CD measurement, is difficult due to the attenuation of light around the edge of the bottom of the hole when using a low numerical aperture. In this paper we propose and demonstrate four bottom CD measurement methods for TSVs: the cross section method, profile analysis method, tomographic image analysis method, and the two-dimensional Gaussian fitting method. To verify and demonstrate these methods, a practical TSV sample with a high aspect ratio of 11.2 is prepared and tested. The results from the proposed measurement methods using white-light scanning interferometry are compared to results from scanning electron microscope (SEM) measurements. The accuracy is highest for the cross section method, with an error of 3.5%, while a relative repeatability of 3.2% is achieved by the two-dimensional Gaussian fitting method.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.7
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• pp.605-613
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• 2014

Scanning white-light interferometry is an important measurement option for many surfaces. However, serious profile measurement errors can be present when measuring free-form surfaces being highly curved or tilted. When the object surface slope is not zero, the object and reference rays are no longer common path and optical aberrations impact the measurement. Aberrations mainly occur at the beam splitter in the interference objective and from misalignment in the optical system. Both effects distort the white-light interference signal when the surface slope is not zero. In this paper, we describe a modified version of white-light interferometry for eliminating these measurement errors and improving the accuracy of white-light interferometry. Moreover, we report systematic errors that are caused by optical aberrations when the object is not flat, and compare our proposed method with the conventional processing algorithm using the random ball test.

• Current Optics and Photonics
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• v.3 no.5
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• pp.408-414
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• 2019

In this paper we propose a method to generate a true color image in scanning white-light interferometry (SWLI). Previously, a true color image was obtained by using a color camera, or an RGB multichannel light source. Here we focused on acquiring a true color image without any hardware changes in basic SWLI, in which a monochrome camera is utilized. A Fourier transform method was used to obtain the spectral intensity distributions of the light reflected from the sample. RGB filtering was applied to the intensity distributions, to determine RGB values from the spectral intensity. Through color corrections, a true color image was generated from the RGB values. The image generated by the proposed method was verified on the basis of the RGB distance and peak signal-to-noise ratio analysis for its effectiveness.

• Journal of Technologic Dentistry
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• v.37 no.4
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• pp.213-218
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• 2015

Purpose: The purpose of this study compared of reproducibility of prepared tooth impression scanning utilized with white and blue light scanners. Methods: To evaluate reproducibility with white and blue light scanners, the impression of premolar were rotated by $10^{\circ}{\sim}20^{\circ}$ and scanned. These data were compared with the first 3-D data (STL file), and the error sizes were measured (n=5). Independent t test was used to evaluation the reproducibility of impression of premolar with white versus blue light scanners through discrepancies of mean, RMS (${\alpha}=0.05$). Results: Discrepancies of mean with regard to reproducibility were $11.2{\mu}m$, $5.8{\mu}m$, respectively, with white and blue light scanners (p<0.047). And discrepancies of RMS with regard to reproducibility were $33.4{\mu}m$, $18.8{\mu}m$, respectively, with white and blue light scanners (p<0.045). Conclusion: Our results indicate a good reproducibility of prepared tooth impression digitized with blue light scanner more than that with white light scanner.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.11
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• pp.999-1006
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• 2014

In this investigation, we explain the sub-sampling technique of white light scanning interferometry (WLSI) to improve the measurement speed. In addition to the previous work using Fourier domain analysis, several methods to extract the height from the correlogram of WLSI are described with the sub-sampling technique. Especially, Fourier-inverse Fourier transformation method adopting sub-sampling technique is proposed and the phase compensation technique is verified with simulation and experiments. The main advantage of sub-sampling is to speed up the measurements of WLSI but the precision such as repeatability is slightly poor. In case of measuring the sample which has high height step or difference, the proposed technique can be widely used to reduce the measurement time.

• Applied Microscopy
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• v.41 no.4
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• pp.223-228
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• 2011

White light scanning interferometry has been employed to analyze surface features of diverse specimens. Long established in the field of materials engineering, the technique provides quantitative three-dimensional data as well as qualitative morphological images. It uses white light that is split and reflected from a reference mirror and an object. Merged together, the light generates interference patterns representing topographical contours of the object surface. The amplitude of the z-axis data is differentiated by gray scale. The technique allows the rapid, noncontact, and wide-field measurements for morphometry of biological specimens including chondrocytes, tooth enamel, and plant leaves. Quantification of the dimension of surface structures such as width, length, and elevation angle could be achievable by white light scanning interferometry. The light reflection from plant leaves has been assumed to be sufficient for the technique. Without special specimen preparations like conductive metal coating, the technique can be increasingly used for quantitative three-dimensional surface measurements of biological specimens.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.6
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• pp.694-699
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• 2012

In this paper, semiconductor package inspection results using white light interferometer with large F.O.V., in order to apply semiconductor product inspection process, are shown. Experimental 3D data repeatability test results for the same special bumps of each substrate are shown. Experimental 3D data repeatability test results for all the bumps in each substrate are also shown. Semiconductor package inspection using white light interferometer with large F.O.V. is very important for the fast 3D data inspection in semiconductor product inspection process. This paper is surely helpful for the development of in-line type fast 3D data inspection machine.

• Korean Journal of Optics and Photonics
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• v.15 no.4
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• pp.331-336
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• 2004

The phase change due to the reflection from target surfaces in a white-light interferometer induces measurement errors when target surfaces are composed of dissimilar materials. We prove that this phase change on reflection as the polarization of the white-light changes causes a shift of both envelope peak position and fringe peak position of several tens of nanometers as the polarization of the white-light changes. In addition, we propose a new equation for white-light interference fringes depending on the polarization of the source.