KEYWORDS: Laser systems engineering, Laser scanners, Sensors, RGB color model, Projection systems, Control systems, Magnetism, Chemical oxygen iodine lasers, Mathematical modeling, System identification
Galvanometric scanning systems are high inertial behavior and high-speed movement widely that be used in laser marking, drilling, full screen projecting and so on. Therefore, the presented galvanometric scanning system and its applications for laser projector system. In includes a galvanometric unit, motor, position detector and control circuit. All components were discussed and developed by this study. The magnetic rotor and a stator magnet are the main components of the scanner system. The moving magnet is composed of NdFeB material and the stator consists of the coil. In addition, the moving capacitive sensor is used to receive signal feedback. The driver is assembled by the high response performance OP-amplifier circuit. Finally, frequency domain methods were used to identify the scanning system.
An absolute measurement method involving a computer-generated hologram to facilitate the identification of manufacturing form errors and mounting- and gravity-induced deformations of a 300-mm aspheric mirror is proposed. In this method, the frequency and magnitude of the curve graph plotted from each Zernike coefficient obtained by rotating the mirror with various orientations about optical axis were adopted to distinguish the nonrotationally symmetric aberration. In addition, the random ball test was used to calibrate the rotationally symmetric aberration (spherical aberration). The measured absolute surface figure revealed that a highly accurate aspheric surface with a peak-to-valley value of 1/8 wave at 632.8 nm was realized after the surface figure was corrected using the reconstructed error map.
Considering the system performance of the projection lens, not only surface quality of the optics shall be concerned, misalignment between each optics and the wavefront distortion contributed by the mounting stress and gravity are also the factors degraded the optical performance. This article introduces the opto-mechanical design and stress-free assembly process of the reflective mirror subsystem with 300 mm in outer diameter of an I-line lithographic projection lens.
The flexure with mounting position pass through the center gravity of the mirror can be adopted as supporting mechanism to prevent the gravity distortion. The distortion due to temperature difference can be avoided by adopting CLERACREAM®-Z glass ceramic and INVAR for material of reflective mirror and supporting flexure respectively. The adjustment mechanism of the mirror subsystem integrates the concepts of Kinematic and exact constraint to provide six degrees of freedom (6DoF) of posture adjustment of the mirror. Furthermore, the assembly process of the flexure which minimizes the mounting stress on the mirror is presented. In the end of this article, interferometric performance test of the reflective mirror after opto-mechanical assembly compared with the measurement result in manufacturing stage is also presented. With the proposed opto-mechanical design and stress-free mounting process of the mirror, the surface distortion contributed by the amount of mounting stress and gravity effect is less than P-V 0.02 wave @632.8 nm.
The radius of curvature is one of the most important specifications for spherical optics [1]. There are several methods and devices currently on the market that can be used to measure it, including optical level, non-contact laser interferometer (Interferometer), a probe-contact profiler (Profilometer), the centering machine and three-point contact ball diameter meter (Spherometer). The amount that can be measured with a radius of curvature of the lens aperture range depends on the interferometer standard lens f / number and lens of R / number (radius of curvature divided by the clear aperture of the spherical surface ratio between them). Unfortunately, for lens with diameter greater than 300 mm, the device is limited by the size of the holding fixture lenses or space. This paper aims to provide a novel surface contour detection method and machine, named “CMM spherometry by probe compensation,” to measure the radius and thickness of the curvature of the optical surface by a coordinate measurement machine (CMM). In order to obtain more accurate optimization results, we used probe and temperature compensation to discuss the effect. The trace samples and the measurement results of CMM and the centering machine, which has top and bottom autocollimators, are compared.
This study proposes an absolute measurement method with a computer-generated hologram (CGHs) to assist the identification of manufacturing form error, and gravity and mounting resulted distortions for a 300 mm aspherical mirror. This method adopts the frequency of peaks and valleys of each Zernike coefficient grabbed by the measurement with various orientations of the mirror in horizontal optical-axis configuration. In addition, the rotational-symmetric aberration (spherical aberration) is calibrated with random ball test method. According to the measured absolute surface figure, a high accuracy aspherical surface with peak to valley (P-V) value of 1/8 wave @ 632.8 nm was fabricated after surface figure correction with the reconstructed error map.
Dual-photoresist complementary lithography technique consisting of inorganic oxide photoresist and organic photoresist is applied to produce the submicron pit array patterns on a sapphire surface. The oxide photoresist is patterned by direct laser writing, and the developed pit size decreases to a smaller value than the laser spot size due to the thermal lithography. The oxide photoresist possesses strong etching resistance against oxygen plasma but shows no resistance against chlorine plasma. During the ion-coupled-plasma reactive-ion-etching process, chlorine plasma is a necessary component to etch the sapphire. Moreover, the characteristics of organic resist are opposite those of oxide photoresist and possess moderate resistance against chlorine plasma but no resistance against oxygen plasma. The thermal and developing characteristics of oxide photoresist are reported in this study. The dependence of laser power on the developed mark sizes and morphologies is examined by atomic force microscopy. The temperature distribution on the photoresist structure during the laser writing is simulated, and the thermal lithography concept is introduced to explain the effect of power on the developed oxide mark width. Images of patterned pit array on a commercial 4-inch-diameter sapphire substrate are also shown.
Dual photoresist complimentary lithography technique consisting of inorganic oxide photoresist and organic photoresist is applied to produce the sub-micro pit patterns on a sapphire surface. The oxide photoresist is patterned by the direct laser writing and the developed mark size decreases to a smaller value than the laser spot size due to the thermal lithography. The small developed pit diameter is one of the advantages using oxide photoresist. The oxide photoresist possesses strong etching resistance against the oxygen plasma but shows no resistance against the chlorine plasma. The chlorine plasma is a necessary component to etch the sapphire during the ion-coupled-plasma reactive-ion-etching process because of sapphire’s mechanical hardness and chemical stability. However, the characteristics of organic resist SU8 are opposite to that of oxide photoresist and possess moderate resistance against chlorine plasma but show no resistance to oxygen plasma. The thermal and developing characteristics of oxide photoresist are reported here. The dependence of the laser power on the developed mark sizes and morphologies is illustrated by atomic force microscopy. The temperature distribution on the photoresist structure during the laser writing is simulated. Images of patterned pits on the large commercial sapphire substrates are also shown.
Ceramics are commonly used as substrates in electrically insulated integrated circuit, printed circuit board, and lightemitting
diode industries because of their excellent dielectric and thermal properties. However, brittle materials (e.q.,
ceramic alumina, sapphire, glass, and silicon wafer) are difficult to fabricate using wheel tools. Laser material processes
are preferred over traditional methods because they allow noncontact processing, avoid tool wear problems, and achieve
high speed, high accuracy, and high resolution. Laser material processes also exhibit minimal residual thermal effects
and residual stress. This study investigated the laser drilling of Al2O3 ceramic material (with a thickness of 380 μm and
hole diameters of 200, 300, and 500 μm, respectively) by using a laser milling method. The macro- and micro-hole
milling performance depended on various parameters including the galvanometric scan speed and milling time. A 3D
confocal laser scanning microscope and a field-emission scanning electron microscope were used to measure the surface
morphology, taper angle, and melted residual height of the machined surface after laser milling. The edge quality and
roundness of laser milling were also observed using image-processing edge-detection technology.
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