A new interferometric vibration sensor for testing both vibration and subsidiary resonance that have detrimental effects on the servo performance of the optical pickup actuator is presented. Experimental results of slim optical pickup actuators obtained from the sub-resonance tester such as the interferometric vibration sensor are presented. It can be also used for other applications in the R&D domain and production environments with a low price and compact size.
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.
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.
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.
Moiré fringes of elongated circular gratings to precisely measure the linear displacements are presented. The moving direction of a grating can be easily determined and the moving displacement can be measured within the accuracy of 1/10 pitch of the grating by using moiré fringes of elongated circular gratings.