• Journal of the Optical Society of Korea
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• v.20 no.4
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• pp.481-487
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• 2016

This study presents a new optical system for a combiner-type head-up display (HUD) with a cylindrical lens as an asymmetrical aberration corrector, instead of a freeform mirror. In the initial design process based on off-axial aberration analysis, we obtain an off-axis two-mirror system corrected for linear astigmatism and spherical aberration by adding a conic secondary mirror to an off-axis paraboloidal mirror. Thus, since the starting optical system for an HUD is corrected for dominant aberrations, it enables us to balance the residual asymmetrical aberrations with a simple optical surface such as a cylinder, not a complex freeform surface. From this design process, an optical system for an HUD having good performance is finally obtained. The size of the virtual image is 10 inches at 2 meters away from a combiner, and the area of the eye box is 130×50 mm².

• Journal of the Optical Society of Korea
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• v.13 no.2
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• pp.184-192
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• 2009

There are total eight degrees of freedom in designing a three-mirror system. If we correct four kinds of third order aberrations and the system should have the specified effective focal length, the remaining three degrees of freedom can be used for selecting a suitable configuration for a specific application. We suggest an analytic design procedure for a three-mirror telescope system which has a suitably sized secondary mirror and proper separations between mirrors, and is corrected for four kinds of third order aberrations, spherical aberration, coma, astigmatism, and field curvature. Two design examples are shown. One has a compact configuration with off-axial field, the other has relatively long configuration with annular ring field.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.49.1-49.1
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• 2018

The MATS (Mesosphere Airglow/Aerosol Tomography Spectroscopy) satellite is the next Swedish science microsatellite. We report optical performance test results of the limb telescope, which is the major payload. This telescope is designed with "linear astigmatism-free" (LAF) off-axis optical system in order to have high optical performance across the wide field of view. We measured Modulation Transfer Function (MTF) and Encircled Energy Diameter (EED) of the limb telescope. Full field imaging tests show expected results without linear astigmatism across the full field of view ($5.67^{\circ}{\times}0.91^{\circ}$). Since the amount of stray light is from the earth and the sun, we also simulated and measured the stray light in the field image.

• Korean Journal of Optics and Photonics
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• v.8 no.1
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• pp.73-79
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• 1997

We analyzed the variation of the focus error signal with the effect of land and groove, wavefront error, and optical system parameter variation for the knife-edge and astigmatism methods on the Land/Groove recordable optical disc, using a numerical simulation method. We verified causes of the zero-cross-shift that took place by the effect of land and groove by analyzing the diffraction beam including defocus wavefront errors. We also found that the sensitivty of the focus error signal was reduced by the effect of land and groove in the astigmatism method, as in the analysis of the focus error signal with the each order of the diffraction beam.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.7
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• pp.87-94
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• 2008

The displacement sensor using optical pickup head is presented. The measuring principle of optical pickup head in focusing direction is adopted to measure displacement. The preliminary tests were carried out to verify the feasibility of the optical pickup head as a displacement sensor and optical pickup head showed about $8\;{\mu}m$ measuring range and 10nm resolution. The methodology to expand measuring range is proposed and proved its validity. The proposed displacement sensors are applied to AFM(Atomic Force Microscope) probe head to measure the deflection of micro-cantilever.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.79.1-79.1
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• 2019

The Schwarzchild-Chang telescope is a confocal off-axis two mirror telescope with D = 50 mm, F = 100 mm and FOV = 8 ° × 8 °. Unlike common off-axis telescopes, the mirrors of the Schwarzchild-Chang telescope share their focal points to remove the linear astigmatism. In this poster, we show the alignment process of the Schwarzchild-Chang telescope with wavefront measurement and the sensitivity table method. Wavefront is measured using the Shack-Hartmann sensor, and Zernike polynomials are obtained from measured wavefront. Sensitivity table method is to calculate alignment errors from the Zernike coefficients. As a result, we evaluate tilt, decenter, and despace of each mirror of linear astigmatism-free con-focal off-axis system.

• Journal of the Semiconductor & Display Technology
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• v.22 no.3
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• pp.52-61
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• 2023

We designed a novel ultra-miniaturized microcolumn structure having an stigmator to significantly improve throughput per unit time, which is the biggest disadvantage of microcolumns. We adopted the structure of the stigmator in the form of an electrostatic octupole electrode, and used an electrostatic quadrupole deflector with a relatively simple structure considering the increase in wiring due to the introduction of the stigmator. We have dramatically reduced the effect of astigmatism that occurs when the electron beam probe is scanned to the periphery of the target by introducing the stigmator between the control electrode and the deflector. As our numerical analysis simulation results, the field of view obtained as a result of this study is about 46.3% improved compared to our previous study, and the electron beam probe size of less than 10 nm was achieved in the entire field of view.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.1
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• pp.77-81
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• 2008

Purpose: This study was to investigate the refractive state of an asian population (male: 39, female: 53) from 21 to 30 years old who visited the A optical shop at jongnogu in seoul. Methods: The visual acuity test was performed by the object and subject method. Results: Among the 184 eyes, myopia is 83.16% and emmetropia is 16.84%, respectively. As for the equivalent spheric power of myopic abnormal refractive eyes, the -m0.5Dt < spheric equivalent ${\leq}$ -2.00Dt was 40.53%, the -2.00Dt < spheric equivalent ${\leq}$ -6.00Dt was 51.63% and anything over the -6.00Dt was 7.85%. The percentages of with-the-rule, against-the-rule and oblique astigmatism among people with astigmatism were 46.67%, 35.56% and 7.77%, respectively. The average of pupillary distance in male (64.5${\pm}$2.9 mm) was greater than that in female (61.9${\pm}$2.3 mm). Conclusions: Korean opticians were provided some useful information about making up a prescription by this research.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.4
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• pp.141-143
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• 2008

Purpose: This study investigated visual acuity and refractive error in elementary schoolchildren and examined relationship between visual acuity and refractive error. Methods: Naked visual acuity and refractive error for selected 200 schoolchildren (400 eyes) of 1st, 3rd and 6th grades. Results: The refractive error in hyperopia was gradually decreased and visual acuity was increased as higher grade. The regression line of Y=2.1471X-3.1484 (F=313.9377, P<0.001) and closed inter-relationship were found between visual acuity and refractive error in myopia. The regression line equation of Y=-0.6854X+1.1764 (F=7.054, P<0.01) and closed inter-relationship were found between visual acuity and refractive error in hyperopia. The relationship between visual acuity and refractive error in astigmatism was Y=2.2509X-2.8738 (F=21.7952, P<0.001) and closed inter-relationship was found. Conclusions: Myopia, hyperopia and astigmatism showed closed inter-relationship with visual acuity.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.4
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• pp.9-12
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• 2008

Purpose: Current gas-mask is very uncomfortable structure for spectacles wearer. Improving this problem can aid military men and firemen to protect themselves and rescue other person. Methods: we changed the structure from dual type of outward lens and inward lens into a single type structure. we attached acrylic frame to gas-mask instead of outward lens and protected the gas inflow by shutting the gab of lens and frame using silicon shield, and made the frame "S" style for removing astigmatism and maintaining of vertex distance. Results: It was possible to correct visual acuity and gas shield, and could changed the lens like a common spectacles. The new type of gas-mask spectacles could remove 0.53D~1.78D astigmatism occurred from the slant of eyesight and lens surface, 0.07D~0.66D overcorrection occurred from short vertex distance, and 0.1D~0.3D astigmatism occurred from pantoscopic angle. Conclusion: Because new type of gas-mask spectacles had clear visual field, it was expected to improve fighting power and rescue ability.