• Journal of Korean Ophthalmic Optics Society
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• v.10 no.4
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• pp.347-355
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• 2005

We investigate the distribution of central spot and the encircled energy in order to assess the performance of central obstructed optical system having central obstruction, when the central obstruction and the degree of truncated Gaussian amplitude of incident beam change. When the radius of central obstruction increases the radius of central spot on the image plane decreases, and when the degree of truncated Gaussian amplitude of incident beam increases the radius of central spot on the image plane increases. As the central obstruction and the degree of truncated Gaussian amplitude of incident beam increase, the depth of focus increases and the encircled energy of central spot decreases. We know from theses results that the effect of Gaussian factor is small as the central obstruction increases. These results was applied to develope the large optical reflection system.

• Korean Journal of Optics and Photonics
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• v.4 no.4
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• pp.428-433
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• 1993

The second harmonic of Q-switched Nd:YAG laser beam with gaussian mode is cut off by pinhole of a certain radius and its central portion passed through pinhole is focused by converging lens. It is confirmed that the shape of this beam in focal region is central symmetric but non-gaussian. Change of transmittance due to self-focusing is investigated by scanning (z-scan) $CS_2$ of 1 mm thickness in the focal region. It is found that the observed results can be consistently explained by Fresnel theory within 1.5% accuracy and efficiency of self-focusing depends on spatial shape of incident beam.

• Journal of Welding and Joining
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• v.25 no.3
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• pp.85-91
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• 2007

The conventional study on the laser surface transformation hardening has been carried out with a beam of the specified shape and uniform power-intensity distribution in order to ensure the uniformity of the hardening depth. Two types of beams - the circular gaussian beam and rectangular beam of the uniform power-intensity distribution were used in this study. we were supposed to optimize the process parameters and to compare the hardening results with two optics respectively. As a result, the hardness distribution of the hardened zone was similar in both cases and the hardened phase by the rectangular beam was denser than that by the circular gaussian beam.

• Korean Journal of Optics and Photonics
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• v.5 no.4
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• pp.453-456
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• 1994

Variations in the amplitude and phase distributions of an incident Gaussian beam are derived analytically when it propagates through a photorefractive crystal in the presence of another strong beam and resulting photorefractive grating that is phase shifted by other than 90.deg. relative to the intensity grating. In the presence of the photorefractive grating the beam is shown to propagate along a straight line in a new direction with an increased wave number.

• Korean Journal of Optics and Photonics
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• v.7 no.3
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• pp.200-206
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• 1996

When a Gaussian beam is incident to a planar dielectric interface at an angle other than Brewster angle or the critical angle of total reflection, we derive the six nonspecular effects of rotation, lateral shift, focal shift, Rayleigh length change, magnitude and phase changes in the complex amplitude of the reflected beam simultaneously by taking account of the boundary condition. In the derivation we assume a Gaussian beam of fundamental mode to emerge from the interface and then match at the interface the constant, linear, and quadratic variations of the amplitude and phase of the reflected beam with those of the incident beam multiplied by the reflection coefficient. Our calculation shows that the six nonspecular effects can result from a linear variation of the natural logarithm of the reflection coefficient at the interface.

• Korean Journal of Optics and Photonics
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• v.32 no.6
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• pp.276-285
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• 2021

This paper reports the study of the line-beam optical system of the laser lift-off (LLO) equipment used in the OLED manufacturing process. To obtain both a long process depth and a narrow width of the line beam, even with the poor M² value of the laser source, the research is focused on the optical system, including the beam transformation unit (BTU). We also propose optical configurations for the super-Gaussian distribution and the fiber-based BTU for the flat-top distribution.

• Journal of Korean Ophthalmic Optics Society
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• v.5 no.1
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• pp.13-18
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• 2000

In this paper, we use the C light which is a daylight and consider the incident beam having the Gaussian amplitude. We investigated the illuminance distributions and the variation in chromaticity of optical system having the truncated Gaussian amplitude on the focal plane and along the optical axis using the C light source. We also use the three sensitivity functions of human eye(CIE 1931) for wavelengths which are from 380nm to 780nm. When the truncation grade of incident beam having Gaussian amplitude decreases, the size of central spot on the focal plane and the depth of focus along the optical axis decrease, and the variation in chromaticity on the focal plane and along the axis increases rapidly. As the illuminance on the focal plane decreases the variation in chromaticity of optical system increases rapidly, and as the depth of focus increases the variation in chromaticity of optical system decreases.

• Current Optics and Photonics
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• v.7 no.6
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• pp.701-707
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• 2023

In laser imaging, accurate extraction of the laser's center is essential. Several methods exist to extract the laser's center in an image, such as the geometric mean, the parabolic curve fitting, and the Gaussian curve fitting, etc. The Gaussian curve fitting is the most suitable because it is based on the physical properties of the laser. The width of the Gaussian laser beam depends on the distance from the laser source to the target object. It is assumed in general that the distance remains constant at a laser spot resulting in a symmetric Gaussian model for the laser image. However, on a curved surface of the object, the distance is not constant; The laser beam is narrower on the side closer to the focal point of the laser light and wider on the side closer to the laser source, which causes the distribution of the laser beam to skew. This study presents a modified Gaussian model in the laser imaging to incorporate the slant angle of a curved object. The proposed method is verified with simulation and experiments.

• 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.

• Current Optics and Photonics
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• v.1 no.2
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• pp.150-156
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• 2017

A diffraction limited optical system for head mounted displays (HMDs) was designed. This optical system consists of four modules, including 1:5 mm and 5:30 mm beam expanders, polarization grating-polarization conversion system (PG-PCS) and refractive/diffractive projection optical module. The PG-PCS module transforms the unpolarized Gaussian beam to a linearly polarized beam and it simultaneously homogenizes the spatial intensity profile. The optical projector module has a $30^{\circ}$ field of view, a 22 mm eye relief, and a 10 mm exit pupil diameter with a compact structure. Common acrylic materials were utilized in the optical design process; therefore, the final optical system was lightweight. The whole optical system is suitable for a 0.7 inch liquid crystal on silicon microdisplay (LCOS) with HDTV resolution ($1920{\times}1080$) and $8.0{\mu}m$ pixel pitch.