Younghun Yu

The influence of carbon content in carbon-doped silicon oxide film by thermal treatment

Abstract Carbon-doped silicon oxide (SiOC) low- k dielectric film was deposited on a p-type Si(100) substrate with mixture of bis-trimethylsilylmethane (BTMSM) and oxygen by inductively coupled plasma chemical vapor deposition (ICPCVD). Electron density and electron temperature of ∼10 12 cm −3 and 1.6 eV, respectively, were obtained at low pressure (

Tilt Aberration Compensation Using Interference Patterns in Digital Holography

We present a numerical procedure that compensates for tilt phase aberration in in-line digital holography by computing the period of interference patterns in the reconstructed phase image. This method enables the reconstruction of correct and accurate phase information, even if strong tilt aberrations exist. Example applications of tilt aberration compensation are shown for a tilted plate, a micro-lens array, and a thin film transistor. This method is convenient because it uses only one hologram and no hardware to minimize the tilt aberration.

Dual-wavelength Digital Holography Microscope for BGA Measurement Using Partial Coherence Sources

Dual-wavelength holography has a better axial range than single-wavelength holography, allowing unambiguous phase imaging. Partial coherence sources reduce coherent noise, resulting in improved reconstructed images. We measured a ball-grid array using dual-wavelength holography with partial coherence sources. This holography method is useful for measurement samples that exhibit coherence noise and have a step height larger than the single wavelength used in holography.

Three-dimensional Information and Refractive Index Measurement Using a Dual-wavelength Digital Holographic

Digital holographic microscopy allows optical path difference measurement. Optical path difference depends on the both refractive index and morphology of sample. We developed a dual-wavelength in-line digital holographic microscope that can measure simultaneously the refractive index and morphology of a sample, providing highly precise three-dimensional information. Here we propose theoretical and experimental methods for dual-wavelength in-line digital holographic microscopy. The measured data were reasonable, although there was data error. By improving the experimental method, we could measure the refractive index more precisely and obtain more accurate three-dimensional information on samples.

Study on Digital Holography with Conjugated Hologram

In this paper we have applied phase conjugated holographyto DHM (digital holography microscopy) to remove phase aberration and noise. Generally,digital holographyincludes the phase information of the object, phase aberration terms introduced by the measurement system and noise terms (DC term and twin images). These aberrations and noise terms decrease the quality of the reconstructed phase image. We could obtain a conjugated hologram which includes only phase information of object. Experimentally we show that distortion of image and aberration of phase in a measurement system are removed using the conjugation hologram.

Three-dimensional measurements by using deflectometry and the double Hilbert transform

An improved phase retrieval method based the Hilbert transform is introduced to quantitatively calculate the phase distribution from the distorted fringe pattern. Also phase measurement deflectomety is widely used in specular-type samples. The background noise or background should be suppressed prior to applying Hilbert transform. In this process, a method for suppressing the background noise the double Hilbert transform, fast, automated, which requires only one image, is presented. The method is easy to implement, and measurements can be conducted. We used the double Hilbert transform method to retrieve the phase and suppressed the background in computer simulations and experiments involving the phase measuring deflectometry method.

Determining the Refractive Index Distribution of an Optical Component Using Transmission Deflectometry with Liquids

Phase-measuring deflectometry is a full-field gradient measuring technique that lends itself very well to testing specular optical surfaces. We have measured the deformation of the surface of a lens by transmission deflectometry with liquids. In this study, a method is proposed for measuring the refractive index distribution of a transparent object component. The proposed method combines transmission deflectometry with liquids. The deformed fringe patterns of a sample immersed in different fluids are recorded, and then the three-dimensional phase information of the sample is reconstructed numerically. We have used phase-shifting and temporal phase-unwrapping methods to retrieve the phase from the measured deformed fringe pattern, and we have used a least-squares method to find the height information of the specular surface from the calculated slope. In particular, we have proposed a theoretical model for determining the refractive index of sample and planar convex lens are demonstrated experimentally.

Determining the Refractive Index and Three-Dimensional Shape of an Optical Component using Digital Holographic Microscopy with Liquid

In this study a method is proposed for measuring both the refractive index and the shape of a transparent object. The proposed method combines a digital holographic microscope with a liquid. The holograms of a sample immersed in different liquids are recorded and then the three-dimensional phase information of the sample is reconstructed numerically. In particular, we have proposed a theoretical model for determining both the refractive index and shape of a sample, and micro-corner cubes are examined experimentally. Keywords: Holography, Digital holography, Corner cubeOCIS codes: (090.0090) Holography; (090.1760) Computer holography; (070.0070) Fourier optics and signal processing

Determining Two-Sided Surface Profiles of Micro-Optical Elements Using a Dual-Wavelength Digital Holographic Microscope With Liquids

In this paper, a method is proposed for simultaneously measuring the front and back surface profiles of transparent micro-optical components. The proposed method combines a dual-wavelength digital holographic microscope with liquids to record holograms at different wavelengths, and then numerically reconstructs the three-dimensional phase information to image the front and back sides of the sample. A theoretical model is proposed to determine the surface information, and imaging of an achromatic lens is demonstrated experimentally. Unlike conventional interferometry, our proposed method supports nondestructive measurement and direct observation of both front and back profiles of micro-optical elements.

Aspheric Lens Measurements by Digital Holographic Microscopy and Liquid

Digital holographic microscopy allows optical path difference measurement. Optical path difference depends on both the refractive index and the morphology of the sample. When interference fringes are very closely spaced, the phase data contain high frequencies where 2π ambiguities cannot be resolved. The immersion testing method, which is a transmission test while the sample is immersed in liquid, is very effective in reducing high frequency fringes in transmission measurements so that large dynamic range testing is possible for a non-null configuration. We developed a digital holographic microscope using liquid that can measure the high numerical aperture aspheric morphology of a sample. This system provides highly precise three-dimensional information on the sample. By improving the experimental method, choosing liquids which have similar refractive index to the sample, we can measure more accurate three-dimensional information on the samples.Keywords: Holography, Digital holography, Aspheric lensOCIS codes: (090.0090) Holography; (090.1760) Computer holography; (070.2590) Fourier transforms