We design an omnidirectional optical system that is composed of pseudo-Cassegrain collecting mirror part making narrow field of view(FOV) and a reverse pseudo-Cassegrain imaging mirror part, which can be used simultaneously in visible and long wavelength infrared(LWIR) light. The FOV is set to 40° to 110° and the F/number is 1.55. Because a CMOS sensor (CMOSIS, CMV2000) for visible and a micro bolometer sensor (semiconductor device, Bird 384) for LWIR are chosen, respectively, the common size of image should be determined by 5.9 mm × 5.9 mm. After the optimizing design, the ratio of the image height about two cases of 40° and 110° is 48.97 %. We can obtain that two MTFs for visible and LWIR at 20 lp/mm about the FOV of 110° are 0.425 and 0.385, respectively. The total length of this system is about 280 mm. When the MTF at 20 lp/mm and 110° is 0.3, the cumulative probabilities of the tolerance in visible and LWIR are 90.69 % and 99.79 %, respectively. After the athermalization analysis in the temperature range of - 32°C to 55°C, we choose the secondary mirror of the imaging part as a compensator to improve the collapsed MTF.
In the omni-directional optical system used for real-time surveillance, we established the theory of basic optical design for a two-reflector catadioptric omni-directional optical system which has a convex primary mirror and a plane secondary mirror as its reflection imaging part. We also established an algorithm and programmed to analyze the variables of the theory. By using this method, the key optical elements related to the primary and secondary mirrors in the system can be simply and easily designed based on the optical system variables such as radius of curvature for the primary mirror and position of the secondary mirror, and location and radius of entrance pupil of the refractive imaging optics. And we achieved readily and successfully an infrared omni-directional optical system for night vision and surveillance of defense and safety by using the basic design theory.
It is common for many companies to use multiple LEDs to enhance the brightness of a LED lamp and, in general, four LEDs are used in the LED lamp systems. Moreover, the second-lens must be used to obtain a straight uniform illumination from LED lights. Where four LEDs are used, four second-lenses are also assembled conventionally and those four units of second-lenses are manufactured from a single mold and assembled together with the LEDs. However, this study introduces a new method of using the Least Square Method to get a uniform illumination with the divergence angle of 40 degrees with a new single injection molded lens. Thanks to this optical design with a single lens, the assembling process of LED lamp system was simplified by eliminating the complicated assembly procedure. Also, the uniformity of illumination of this newly designed lamp system was less than 14.1%.
Optical vision systems have been developed gradually from wide field of view to all directional field of view for the
purpose of security, surveillance, and teleconferencing. An omnidirectional image of optical vision systems is an image
with 360 degrees field of view in the horizontal plane and wide field in the vertical plane. The fish-eye lens and the
multiple cameras are typically used to get the omnidirectional image. In this paper, we designed and fabricated an
omnidirectional camera lens system (OCLS) with a catadioptic system, which have as following several advantages;
wide vertical field of view (+53 deg ~ -17 deg.), small size, low cost, ease of fabrication, and high resolution images.
In the process of lithography for semiconductor devices, the disuse of semiconductor devices is caused by the several
hundred nanometer size pollutants generated by photochemical reactions, which is called by the haze. Therefore, the real
time visual detection system is needed to inspect hazes before the existence of disuse semiconductor devices. We
proposed and experimentally confirmed the concept of the real time scanning detection system for the defect on the
photo-mask by interference fringes generated between the light wave scattered by small defect on the photo-mask and
the reflected light wave from the rest area of the front surface.
We present the application of ellipsometry to the phase measurement of surface plasmon resonance (SPR) in
biomolecular detection. In this work, the experimental setup for the SPR sensor was based on a custom-built rotating
analyzer ellipsometer, which was equipped with a SPR cell and a microfluidic system. We investigate the sensitivity of
SPR sensor which is dependent on the thickness and roughness of metal film, alignment of optical system, and stability
of microfluidics. In the drug discovery process, to directly monitor the interaction of small molecule-protein, it is
necessary to design a high-sensitivity SPR sensor with a sensitivity of greater than 1 pg/mm2. Our sensor demonstrates a
much better sensitivity in comparison to other SPR sensors based on reflectometry or phase measurements. The results of
calibration indicate that the phase change, δ▵, had an almost linear response to the concentration of ethanol in the
double-distilled water solutions. A quantitative analysis of refractive index variation was possible using the results of the
ellipsometric model fits for the multilayered thin film on the gold film. Thus, this method is applicable not only to sensor
applications, such as affinity biosensors, but also to highly sensitive kinetics for drug discovery. In this paper, we
demonstrate how a custom-built rotating analyzer ellipsometer in the SPR condition can be used to directly obtain the
interactions and binding kinetics of analytes (biotins, peptides) with immobilized ligand (streptavidin, antibody). We
achieved a detection limit of lower than 1.0 x10-7 RIU, which is the equivalent of 0.1 pg/mm2.
It was reported that the ArF excimer laser mainly used in the process of lithography for semiconductor devices cause
pollutants on a photo-mask by various photochemical reactions, which is called by the haze. Therefore, the real time
detection system on the lithography process is needed in order to inspect the generation of defects containing the haze on
the mass production system before and/or after the generation of defects. We proposed and experimentally confirmed the
concept of the new real time detection system to detect automatically and visually many defects with several hundred
nanometer size generating on a photo-mask by using interference fringes generated by interfering between the light wave
scattered by small defects of a photo-mask and the reflected light wave from the rest area of the front surface. In order to
balance the contrast ration of two interference light waves, we utilized the incident beam with the nearly Brewster angle
on the photo-mask and a linear polarizer aligned in front of the CCD camera. For all of the Cr defects from the size of
0.6 μm to that of 10 μm we succeeded to detect the interference fringes between the scattered beam and the reference
beam.
KRISS Space Optics Research Center has tested large aspheric surfaces by using interferometry and a series of computer-generated hologram (CGH). In this case it is necessary to fabricate various CGHs in the laboratory level. To address this purpose we are developing and improving a simple and precise laser writing system which uses a cylindrical or circular coordinate. In our system 300 mm diameter CGH can be fabricated with 0.8 μm spatial resolution in radial direction. The writing source Ar+ laser is stabilized by intensity feedback, and gives us approximately 800 mW after the stabilization process at 457.9 nm wavelength. The stabilized beam power is controlled again to make 256 different intensity levels. We also used an auto-focusing technique with astigmatic lenses for the purpose of focusing the writing beam on the material surface.
The mobile phone market grows rapidly and the performance estimation about camera module is required. Accordingly, we fabricate the MTF measurement system for a mobile phone lens having extremely small diameter and large f-number. The objective lens with the magnification of X20 for MTF measurement for high resolution lens and a detector of CCD that is pixel size of 7.4 um are adapted to the system. Also, the CCD is translated by using a linear motor to reduce measurement errors. The measurement lens is placed at the most suitable imaging point by a precise auto-focusing motor. The measuring equipment which we developed for off-axis MTF measurement of a mobile phone lens used the multi-square objects. The square objects of measuring equipment are arranged a unit in the on-axis and total 12 units (0.3 field: 4 units, 0.5 field: 4 units, 0.7 field: 4 units) in the off-axis. When the measurement is started, the linear motors of signal detection part are transferred from on-axis to off-axis. And a detected signals from the each square objects are used for MTF measurement. System driver and MTF measure are using application program that developed us. This software can be measure the on-axis and the off-axis sequentially. In addition to that it did optimization of motor transfer for measurement time shortening.
In the simultaneous measurement of the sagittal and tangential modulation transfer function (MTF) of an optical system
by using a square object, we analyze various correction factors due to the irregular illumination of the source, the
rotation of the square object, and the off-axis effect by the object size for the precise measurement of the MTF. These
results can be used in the more exact and effective MTF measurement using the square objects instead of an ordinary
pinhole or slit.
Continuous monitoring of soil movements is important to maintain civil structures. Fiber optic sensors can give the sensing solution for continuous displacement monitoring because they can be multiplexed with various sensors on one line of optical fiber, have the durability to harsh environments, and also are not affected by electro-magnetic effects. In this study, we work on the development of a multiplexed optical loss based fiber optic sensor for measuring displacements using the signal difference between the two reflected signals from a pair of optical connectors with various bending losses between them through an optical time domain reflectometer. We fabricate a multiplexed optical loss based fiber-optic sensor detecting linear displacements of 5 measuring positions of an object by setting these new 5 fiber-optic sensor probes on a single mode fiber simultaneously. We find that these sensors have a good capability to measure the displacements.
Providing marine signal lanterns, Fresnel lens has been adopted to transfer the beam from the lanterns up to 10 nautical miles (18.53 km). The Fresnel lens with diameters of 250 mm was designed by a ray tracing program and optimized by adjusting the groove parameters of the lens. Each optical sag element which is a part of a lens was independently designed by using the analytical method. The angular luminous intensity distributions (ALID) of this lens were calculated by the illumination analysis program considering the ALID of a light bulb. The ALID of a C-8 type bulb (24 W) was measured with a goniophotometer and its luminous flux was measured by an integrating sphere to be 397 lm. At the best alignment of the bulb, the maximum luminous intensity of the lantern was more than 1000 cd for the 250 mm lens. The ALID was investigated as a function of distance from the lens focus to determine the tolerance margin of the alignment. Horizontal deviations of the light bulb from the focus along the optical axis widened the angular FWHM of the vertical ALID. However, vertical deviations caused shifts of the vertical ALID without spreading the angular FWHM. The designed 250 mm aspherical lens of marine signal lantern was made by the injection molding with single peace acryl. We measured the luminous intensity distribution of acryl lens and found that the MLI of the lens was 827 cd. And the full width at half maximum of the diverging angle of the diverging beam was 3.5 deg. Although the measured MLI was 83% of the calculated result, it would be increased with surface polishing of prototype molding pattern.
The multi-configurative microscopic system for inspecting the wire-bonding of reed frame is designed. Object rays is nearly collimated by a objective lens group which is a common lens group of x2 and x6 imaging lens systems and is splitted by two beam-splitters composed of a penta-prism and a refracting prism. And object rays started from the central region and the boundary region(reed frame region) on semiconductor chip(that is, the object) are imaged at the two different imaging planes by x2 and x6 imaging lens groups, respectively. The x6 imaging lens system with a constant object distance and a constant magnification is well designed by general imaging optics system design method. However, since the depth of wire structure on the reed frame has about ±3 mm, in order to observe by a constant magnification and at a fixed imaging plane without the dependency on the variation of objective distance generated by the depth of wire structure on the reed frame, the imaging lens system is composed of two separated groups, which should be moved along nonlinear locus like mechanically compensated zoom lenses. The nonlinear equations for zoom locus are derived by using the Gaussian bracket. Refraction powers and positions of each groups are numerically determined by solving the equations, and initial design data for each groups is obtained by using Seidel third order aberration theory. The optimization technique is finally utilized to obtain this multi-configurative microscopic system.
Two methods to measure the MTF (modulation transfer function) of an optical engine of CRT rear projection HDTV (high definition television) are introduced. A rotating image analyzer on the fluorescent surface with a 2D CCD and a relay lens is used to test in the full-field angle. We developed a software program to automatically locate and measure the position of the maximum value of the MTF at any spatial frequency.
A new synthetic evaluation method for the color display is studied. A testing system to measure the luminance, chromaticity, contrast ratio, uniformity, viewing angle as well as the PMTF (polychromatic modulation transfer function) is presented. The PMTF is calculated from the values of the monochromatic MTFs weighted by the CIE photopic luminous efficiency function of the human visual system. A high-precision XYZ translation stage to move the testing system and a two-axis goniometer to tip and turn the display under test to the desired viewing angle are used.
The analysis of the polychromatic modulation transfer function (PMTF) for evaluating the image quality of the color LCD monitor is presented. The PMTF is easily calculated from the values of the MTF weighted by the overall spectral response of the system. To obtain the spectral response of the monitor, the chromaticity (x, y) and luminance are measured with a spectroradiometer. The variations of the luminance, chromaticity (x, y), and MTF of the color CRT and LCD monitors for different viewing angles are measured. We designed a synthetic equipment that could obtain the chromaticity (x, y), luminance, and MTF of the color monitor simultaneously. The experimental results of several color monitors made in Korea are presented.
A method for measuring the wave front errors and the modulation transfer function (MTF) of the large aperture optics is presented. The large aperture Fizeau interferometer with long optical path difference by using a (phi) 400 mm off-axis parabolic mirror is made. The MTF is measured at the wavelength of the interferometer by changing the laser into the partially incoherent light. A bidirectional shearing interferometer is used for collimation testing. The test results of a (phi) 300 mm Cassegrain type satellite telescope made in Korea are presented.
We propose a method for evaluating the image quality of color LCD monitors by using the polychromatic modulation transfer function (PMTF). The PMTF is calculated from the values of monochromatic MTFs weighted by the overall spectral response of the system. We also propose a method for simulating the PMTF of a color LCD monitor by using three bar targets with different amplitudes. To obtain the spectral response of the color LCD monitor, the chromaticity (x,y) and luminance are measured with a spectroradiometer. The PMTF measuring system with a 2-D cooled charge coupled- device camera, an objective lens and a translator is used to evaluate the color LCD monitor.
We theoretically and experimentally investigate the properties of moire fringes formed by a helical grating illuminated with a white light source, we propose a simple moire method of determining the helicity state and the pitch in a helical winding of wire.
A finite-difference time-domain method is used to examine the optical force acting on a nanometric object in the near zone of a metal slit. Numerical results show that the object of refractive index N equals 1.5 can be trapped near the slit center by the evanescent field gradient force.
We demonstrate a windmill type rotation of combined Mie particles caused by the evanescent field generated at the surface of a Gadolinium Gallium Garnet prism where a linearly polarized Nd:YAG laser beam (of wavelength 532 nm and power 100 mW) is totally reflected. The combined particles (e.g., doublets, triplets or quadruplets) consisting of polystyrene latex (or yeast) spheres with diameters of 3 - 5 micrometers are reported to rotate at 0.1 - 1 rpm in water when the particles are slightly displaced from the center of the evanescent field.
We demonstrate a simple method of determining the absolute order of shadow moire fringes by comparing the fringes with those of a crossed-line grating.
A speckle-photographic method with a diffraction grating is proposed for improving the sensitivity of out-of-plane displacement measurement. This technique is based on the fact that the speckle displacement due to out- of-plane object displacement increases in the higher-order diffracted field.
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