• Journal of the Optical Society of Korea
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• v.4 no.2
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• pp.89-93
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• 2000

Recently a new signal processing algorithm for white light interferometry was presented. In this paper, the proposed signal processing algorithm was applied for absolute temperature measurement using white light interferometry. Stability testing and absolute temperature measurement were demonstrated. Stability test demonstrated the feasibility of absolute temperature measurement with an accuracy of 0.015 fringe. The test also showed that the absolute temperature measurement system using white light interferometry is capable of obtaining the theoretical minimum detectable change (0.0005 fringe), which is consistent with the performance predicted by the proposed signal processing algorithm.

• 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.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.110-113
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• 2001

We present an interferometer system, which is able to perform both the phase shifting interferometry and white light interferometry. The interferometer system uses a d.c. motor to control the probe position with an accuracy of 10nm, which shows an outstanding performance on white light interferometry. However, the moving mechanism of d.c. motor is not accurate enough for the phase shifting interferometry that requires a moving precision less than 1 nm. We therefore propose a Fourier transform technique to calculate the phase of interferograms, which is strongly resistant to calibration errors and external vibration. Experimental results show that the Fourier transform technique is capable of reducing the measurement error caused by inaccurate movement within 0.1nm.

• 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.25 no.1
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• pp.85-91
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• 2008

White light scanning interferometry has gotten a firm position in 3D surface profile measuring field. Recently, the LCD industry gave a chance for this technology to enter into real industry fields. It is known that white-light phase-shifting algorithm give a best resolution compare to other algorithms, but there are some problems to be resolved. One of them is 300nm jump in height profile, called bat-wing effect. The main reason of this problem is an ambiguity of phase-peak detection algorithm, and some solution has been proposed, but it didn't work perfectly. In this paper, I will show the cases when these effects are occurred, and these height discrepancies will be almost disappeared when broad-band illuminators are used.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.23-24
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• 2006

We present a dispersive scheme of white-light interferometry that enables not only to perform tomographical measurements of thin-film layers but also to measure a refractive index without mechanical depth scanning. The interferometry is found useful particularly for in-situ 3-D inspection of micro-engineered surfaces such as liquid crystal displays, semi-conductor and MEMS structure, which requires for high-speed implementation of 3-D surface metrology.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.4 s.193
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• pp.21-28
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• 2007

• 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.

• 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.