Abstract: An apparatus and method for measuring air currents on the surface of a substrate, which can accurately measure the magnitude and direction of air currents on the surface of a wafer with wafer-type air current measurement sensors, are provided. The apparatus includes: a first air current measurement module measuring a magnitude of air currents on a surface of a first substrate, which is processed in accordance with a semiconductor manufacturing process; a second air current measurement module measuring a movement direction of the air currents; and a power module supplying power to the first and second air current measurement modules, wherein the first air current measurement module, the second air current measurement module, and the power module are mounted on a second substrate, which has the same shape as the first substrate.

Abstract: A video image projection apparatus is disclosed. The apparatus uses a laser as a light source and modulates the light beam using a modulator according to an image signal. The apparatus projects the modulated light to a screen using a light scanning system. The laser display system includes three primary color laser light sources, an optical system needed for three-color light combining/separation, a light modulator loading the image signal into the three-color laser, and a driving circuit driving the system by processing the video signal electronically. A hybrid video laser color mixer has a structure that combines very small-sized hybrid light beam combining/separation optical elements and a 3-channel light modulator. It allows the size of the image projection apparatus to be about 6 by 5 by 3 centimeters. Additionally, the light alignment of the elements is close to self-alignment.

Abstract: A laser video projector for projecting an image to a plurality of screens is provided. It is possible to display an identical image to a plurality of screens by modulating light from the light source by an acousto-optic modulator (AOM) according to a video signal and projecting video information to a plurality of screens using a scanner.

Abstract: A light separation apparatus using a flat plate including a wide band anti-reflection coating film, first and second dichroic mirrors, a wide band high-reflection coating film, an anti-reflection coating film, and a material forming the flat plate. The wide band anti-reflection coating film allows an incident light beam generated by a light source to penetrate into the material at a first angle without reflection. The first dichroic mirror allows only a light beam with a first wavelength to penetrate at the first angle and reflects light beams with other wavelengths at the second angle. The high-reflection coating film reflects at a second angle the light beam reflected by the first dichroic mirror. The second dichroic mirror allows only a light beam with a second wavelength to penetrate outside the material at the first angle so that it is parallel to the light beam with the first wavelength penetrated through the first dichroic mirror.

Abstract: A light combining apparatus using two flat plates combines three separate light beams having blue, green and red wavelengths to a single combined light beam for a light source by an easier and simple small-sized device and makes the combined light beam smoothly enter the place for implementing the final information. The apparatus includes a reflection mirror for reflecting light beams with all of the wavelengths, at least one filter for transmitting only at least one light beam with a specific wavelength and reflecting light beams with the other wavelengths, and a medium located between the reflection mirror and the filter, through which the incident light beams and the reflected light beams pass, wherein the three light beams are combined into a single light beam within the medium which single light beam then exits the apparatus. A method of combining separate light beams having different wavelengths is also disclosed.

Abstract: An apparatus for separating an incident light beam from a light source into three light beams having different colors by a mirror mechanism constructed in a particular way. The apparatus separates white-light into three colors of red, green, and blue and includes a first dichroic mirror, a wide band high-reflection mirror, a second dichroic mirror, and a material of air or gas. The first dichroic mirror allows only a light beam with a first wavelength to penetrate and reflects light beams with other wavelengths, from the incident light beam. The wide band high-reflection mirror reflects the light beam reflected from the first dichroic mirror within the material, and is positioned such that it is parallel to the first dichroic mirror and is spaced therefrom by a predetermined interval.

Abstract: A beam path expander for a large-area laser projection display system having a small compacted optical system includes an incidence plane forming an anti-reflection plane to admit light having a specific wavelength into a medium without reflection, a first total reflection plane that is cut into the beam path expander at a total reflection angle determined by the refractive index of the medium for total-reflecting the light admitted from the incidence plane in the medium, a second total reflection plane that is cut into the beam path expander at a total reflection angle for total-reflecting the light reflected from the first total reflection plane at the total reflection angle in the medium, n third total reflection plane(s) (n=0, 1, 2, . . .

Abstract: A light combining apparatus using a flat plate operating to combine at least two incident light beams entering the flat plate at a first angle with respect to the vertical direction on an incidence plane with wavelengths different from each other.

Abstract: A second harmonic generation apparatus provides a polarization element transmitting only light polarized in an extra-ordinary axis direction on the proceeding path of a second harmonic emitted from a resonator. The light polarized in the extra-ordinary axis direction is transmitted to a beam splitter, and a part of the polarized light is fed back to a feedback circuit, so that the temperature of a non-linear birefringent crystalline element inside resonator can be stably controlled and the output second harmonic can be stably produced.

Abstract: A second harmonic generation method and apparatus is capable of stabilizing an output. The apparatus provides a first beam splitter on the proceeding path of a second harmonic output, and other beam splitters on the proceeding path of the reflecting beam of the second harmonic and that of the transmitted beam. A second and third beam splitters are arranged on the proceeding paths of the second harmonic output and the beam separated from the second harmonic output to satisfy ##EQU1## where K is a constant, R.sub..parallel. is reflectivity with respect to p-polarization parallel to the incident surface of the first and second beam splitter, and R.sub..perp. is reflectivity with respect to s-polarization perpendicular to the incident surface of the first and second beam splitters.

Abstract: A second harmonic generator for generating a stable harmonic includes an input mirror and an output mirror for providing a resonating section which is optically confined, second harmonic generation elements for generating a second harmonic using an externally applied pumping energy, and a casing for supporting the optical components. A temperature regulating device for mode selection is provided under the nonlinear birefringent crystalline device. A temperature correction device is provided in the peripheral surface of the casing for correcting the temperature of the casing. A controller senses the temperature of the casing and maintains the sensed temperature within a preset temperature range. Such a structure can generate a stable harmonic output even with large changes in ambient temperature. Particularly, the desired light output can be obtained within a short time.