• Journal of the Korean Society of Clothing and Textiles
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• v.27 no.5
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• pp.554-559
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• 2003

A newly developed contact angle measurement instrument by laser beam projection allows for rapid and direct determination of contact angles. The instrument may have a possibility to characterize newly developed nano-fibers. When the laser beam impinges on an edge of an interface of liquid and solid, projected beam were split across and made two straight lines on a tangent screen. From the result, it could measure the contact angle directly by reading the angle between two split beams. The purpose of this study was to prove reliability and reproducibility of the contact angle measurement instrument by laser beam projection compare to the conventional one by microscope through the comparative experiment and questionnaire. Test samples were selected by consideration of hydrophilic and hydrophobic, such as nylon 6 and polypropylene, respectively. The laser contact angle measurement has accurate, fast and convenient method to measure contact angle, and it can be a unique method to characterize nano-fibers.

• Laser Solutions
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• v.17 no.3
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• pp.19-23
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• 2014

To directly engrave circuit-line patterns as wide as $6{\mu}m$ in a buildup film to be used as an IC substrate, we applied a projection ablation technique in which an 8 inch dielectric ($ZrO_2/SiO_2$) mask, a DPSS 355nm laser instead of an excimer laser, a ${\pi}$-shaper and a galvo scanner are used. With the ${\pi}$-shaper and a square aperture, the Gaussian beam from the laser is shaped into a square flap-top beam. The galvo scanner before the $f-{\theta}$ lens moves the flat-top beam ($115{\mu}m{\times}105{\mu}m$) across the 8 inch dielectric mask whose patterned area is $120mm{\times}120mm$. Based on the results of the previous research by the authors, the projection ratio was set at 3:1. Experiments showed that the average width and depth of the engraved patterns are $5.41{\mu}m$ and $7.30{\mu}m$, respectively.

• Laser Solutions
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• v.16 no.3
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• pp.27-31
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• 2013

To engrave high-density circuit-line patterns in IC substrates, we applied a projection ablation technique in which a dielectric ($ZrO_2/SiO_2$) mask, a DPSS UV laser instead of an excimer laser, a refractive beam shaping optics and a galvo scanner are used. The line/space dimension of line patterns of the dielectric mask is $10{\mu}m/10{\mu}m$. Using a ${\pi}$ -shaper and a square aperture, the Gaussian beam from the laser is shaped into a square flap-top beam; and a telecentric f-${\theta}$ lens focuses it to a $115{\mu}m{\times}105{\mu}m$ flat-top beam on the mask. The galvo scanner before the f-${\theta}$ lens moves the beam across the scan area of $40mm{\times}40mm$. An 1:1 projection lens was used. Experiments showed that the widths of the engraved patterns in a buildup film ranges from $8.1{\mu}m$ to $10.2{\mu}m$ and the depths from $8.8{\mu}m$ to $11.7{\mu}m$. Results indicates that it is required to increase the projection ratio to enhance profiles of the engraved patterns.

• Journal of Power System Engineering
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• v.3 no.2
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• pp.79-83
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• 1999

We implemented a system that can change laser beam directions rapidly by controlling the galvano-mirror, on which a mirror is mounted, with a computer. We show that a laser projection can be realized by programming our system properly, and that it can also be used for multiplexing 2-dimensional image information in the data storage of holographic memories efficiently.

• Proceedings of the Korean Fiber Society Conference
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• 2003.10a
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• pp.103-103
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• 2003

A newly developed contact angle measurement instrument by laser beam projection allows for rapid and direct determination of contact angles. From the result of comparative experiment and questionnaire, the laser contact angle.

• Laser Solutions
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• v.15 no.4
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• pp.16-19
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• 2012

Due to the fact that the dimensions of circuit lines of IC substrates have been forecast to reduce rapidly, engraving the circuit line patterns with laser has emerged as a promising alternative. To engrave circuit line patterns in an IC substrate, we used a projection ablation technique in which a metal (INVAR) mask and a DPSS UV laser instead of an excimer laser are used. Results showed that the circuit line patterns engraved in the IC substrate have a width of about 15um and a depth of $13{\mu}m$. This indicates that the projection ablation with a metal mask and a DPSS UV laser could feasibly replace the semi-additive process (SAP).

• Current Optics and Photonics
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• v.1 no.1
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• pp.23-28
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• 2017

The laser has been regarded as the potential illumination source for the next generation of projectors. However, currently the major issues in applying the laser as an illumination source for projectors are beam shaping and laser speckle. We present a compact solution for both issues by using a vibrating diffractive optical element (DOE). The DOE is designed and fabricated, and it successfully transforms the circular Gaussian laser beam to a low speckle contrast uniform rectangular pattern. Under a vibration frequency of 150 Hz and amplitude of $200{\mu}m$, the speckle contrast value is reduced from 67.67% to 13.78%, and the ANSI uniformity is improved from 24.36% to 85.54%. The experimental results demonstrate the feasibility and potential of the proposed scheme, and the proposed method is a feasible approach to the miniaturization of laser projection display illumination systems.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.10
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• pp.64-74
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• 2007

Because of the size and environment in the shipbuilding process, the portable type robot is required for the automatic seam tracking. For this reason, the structure of laser sensor should be considered in the initial design step and the coordinate transformation between welding robot and laser sensor, which is joint finder, must be identified exactly and the real time tracking algorithm based on these consideration could be developed. In this research, laser displacement sensor in which its structure is laser beam's vertical projection, is developed to recognize the location of weld joint. In practical applications, however, images of weld joints are often degraded because of the surface specularity or spatter. To overcome the problem, the constrained joint finding algorithm is proposed. In the approach of coordinate conversion rule for the visual feedback control among welding torch, robot body and laser sensor is applied by the same reference point method. In the real time seam tracking algorithms we propose constrained sampling method which uses look ahead distance. The RLS(Recursive Least Square) filter is applied to obtain the smooth tracking path from the sensitive edge data. From the experimental results, we could see the possibility that the developed laser sensor with proposed processing algorithm and real time seam tracking method can be used as a welding under the shipbuilding condition.

• Korean Journal of Optics and Photonics
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• v.24 no.5
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• pp.224-230
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• 2013

Laser Lift-Off (LLO) is a process that removes a GaN or AIN thin layer from a sapphire wafer to manufacture vertical-type LEDs. It consists of a light source, an attenuator, a mask, a projection lens and a beam homogenizer. In this paper, we design an attenuator and a projection lens. We use the 'ZEMAX' optical design software for analysis of depth of focus and for a projection lens design which makes $7{\times}7mm^2$ beam size by projecting a beam on a wafer. Using the 'LightTools' lighting design software, we analyze the size and uniformity of the beam projected by the projection lens on the wafer. The performance analysis found that the size of the square-shaped beam is $6.97{\times}6.96mm^2$, with 91.8 % uniformity and ${\pm}30{\mu}m$ focus depth. In addition, this study performs dielectric coating using the 'Essential Macleod' to increase the transmittance of an attenuator. As a result, for 23 layers of thin films, the transmittance total has 10-96% at angle of incidence $45-60^{\circ}$ in S-polarization.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1335-1336
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• 2008

A compact diode-pumped microchip(DPM) green light source which consist of pump LD, $Nd:YVO_4$, KTP and a built-in thermoelectric element has been fabricated for laser projection display. The volume of the source is as small as $0.7\;cm^3$ and we obtained the output power of 25mW with the average electric power consumption in pump LD of 304mW which correspond to the electrical-to-optical efficiency of 7.8%. Another approach using quasi phase matching(QPM) technique has been attempted. We obtained the output power of 90mW of green beam with 350mW pumping of a $Nd:YVO_4$ laser with 20-kHz rep. rate and 10-ns pulse duration. Detailed characteristics and issues of the DPM and QPM green light sources will be addressed.