• International Journal of Precision Engineering and Manufacturing
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• v.1 no.1
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• pp.49-55
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• 2000

The semiconductor industry relies on digital optical imaging for the overlay metrology of integrated circuit patterns. One critical performance demand in the particular application of digital imaging is placed on the edge resolution that is defined as the smallest detectable displacement of an edge from its image acquired in digital from. As the critical feature size of integrated circuit patterns reaches below 0.35 micrometers, the edge resolution is required to be less than 0.01 micrometers. This requirement is so stringent that fundamental behaviors of digital optical imaging need to be explored especially for the precision coordinate metrology. Our investigation reveals that the edge resolution shows quasi-random characteristics, not being simply deduced from relevant opto-electronic system parameters. Hence, a stochastic upper bound analysis is made to come up with the worst edge resolution that can statistically well predict actual indeterminate edge resolutions obtained with high magnification microscope objectives.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.139-140
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• 2008

• Journal of the Optical Society of Korea
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• v.7 no.3
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• pp.131-134
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• 2003

We demonstrated an optical frequency synthesizer based on a femtosecond (fs) mode-locked Ti:sapphire (Ti:s) laser by simultaneously stabilizing the carrier-offset frequency, $f_{ceo}$, and repetition rate, $f_{ rep}$, referenced to the Cs atomic frequency standard. By using two wide-band digital phase-detectors we realized a phase-coherent link between $f_{rep} and f_{ceo} with the relation f_{ceo} = f_{AOM} 5/6f_{rep} ≡ 0, where f_{AOM} = 5/6f_{rep}$ is the phase-locked driving frequency of an acousto-optic modulator (AOM) in a self-referencing interferometer and $f_{rep}$ = 100 MHz. As a result, we could stabilize all components of the fs laser comb at once with an equal frequency separation $f_{rep}$ = 100 MHz with $f_{ceo}$ = 0. In our optical frequency synthesizer, the frequency of the nth component ($f_{n}$) is given exactly by the simple relation $f_n = nf_{rep}$, enabling us to use the fs laser comb as a frequency ruler in the optical frequency metrology.

• Proceedings of the Optical Society of Korea Conference
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• 1999.08a
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• pp.30-31
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• 1999

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.5 no.1
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• pp.33-42
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• 1996

The high coherence of laser beam has made it possible to observe interference effects even in the light scattered from rough surfaces. That's why, when object with a scattering surface is illuminated with laser light, we do see a speckled appearance due to random interference. This sort of unique property of laser speckle has bruht into existence the new noncontaciting techniques such as speckle metrology method of measuring deformation, displacement, and vibration etc of objects with high optical sensitivity. The measurable range of speckle metrology especially used to measure in -plane information, however, is limited by some factors, the so-called strain, rotation tilt of surface and out of displacement perpendicular to the plane of analysis This restrictions severly limits the measurable range of speckle metrology by causing the decorrelation of speckle patterns. It is the purpose of this paper to give a survey on the measurable limitation of speckle photography method that is one of speckle metrology. Namely we will discuss the mutual relationships and problems of each limitations adding the restriction on the largest and smallest displacement measurable with speckle methods.

• Proceedings of the Optical Society of Korea Conference
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• 2007.07a
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• pp.23-24
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• 2007

• Proceedings of the Optical Society of Korea Conference
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• 2006.02a
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• pp.107-108
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• 2006

• Proceedings of the Optical Society of Korea Conference
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• 2008.02a
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• pp.273-274
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• 2008

• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.21-22
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• 2006

• Current Optics and Photonics
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• v.5 no.1
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• pp.40-44
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• 2021

In this paper, LED arrays with segmented mirrors and a mask are presented as a new dark-field illuminator for reflective Fourier ptychographic microscopy (FPM). The illuminator can overcome the limitations of the size and the position of samples that the dark-field illuminator using a parabolic mirror has had. The new concept was demonstrated by measuring a USAF 1951 target, and it resolved a pattern in group 10 element 6 (274 nm) in the USAF target. The new design of the dark-field illuminator can enhance competitiveness of the reflective FPM as a versatile measurement method in industry.