Minimization of mixed-color image noise caused by shape error of polygonal mirror in color-laser printing system

Microsystem Technologies - A color-laser printing system consisting of a tandem laser scanning unit uses four laser diodes and a single polygonal mirror (PM) to expose light onto four...     

Optical system design for light detection and ranging with ultra-wide field-of-view using liquid lenses

The light detection and ranging (LiDAR) technology is based on irradiating near-infrared light and measuring the time-of-flight of the scattered light in an object. This technology is becoming increasingly important, as the requirement of three-dimensional camera technology for future autonomous vehicles is on the rise. In this study, we propose an ultra-wide field-of-view (FOV) optical system for LiDAR that can sequentially scan a beam emitted from a high power laser through a small beam steering system using a liquid lens and a fisheye lens. The proposed optical system consists of a series of liquid lenses for beam steering, a commercial fisheye lens with a wide FOV, and a relay optics to effectively conjugate the intermediate image planes of the two lens systems. To verify theoretical feasibility, we have designed a practical optical system with an FOV of approximately 170°, which is much higher than the FOVs in any other non-rotating LiDAR systems.

     

Improvement of imaging characteristics by pupil apodization in a laser scanning system for electro-photography

It is well known that imaging characteristics such as beam spot size and focal depth can be improved by applying apodization of amplitude and phase at the entrance pupil of an optical system. As an optical system for the electro-photography continuously requires highly resolved dot image and extended focal length to obtain more delicate expression with adequate production stability. Advantages from apodization technique can improve system performance and supply high degree of reliability of the optical system. However, issues on reduction in absolute optical power and on side-lobe of beam spot profile have been technical barrier for its useful implementation to imaging optics for commercial devices. Thorough this paper, theoretical feasibility of application of a pupil apodization to a laser scanning optical unit is mainly discussed in the aspects of optical power reduction and side-lobe of spot profile, as well as enhancement of optical resolution and focal depth. In addition, fundamental experimental results on beam spot profile through focal region are followed to uphold feasibility analysis.

     

Dynamic analysis of multilayer ceramic capacitor for vibration reduction of printed circuit board

Owing to their high permittivity and volumetric efficiency, the demand for multilayer ceramic capacitors (MLCCs) has increased rapidly in recent times. Because of the electromechanical characteristics of BaTiO₃, MLCC vibrates, resulting in printed circuit boards (PCBs) generating acoustic noise. To construct an accurate finite element model of an MLCC, piezoelectric and electrostrictive coefficients were extracted and verified through experiments. The top cover layer thickness and bandwidth were chosen as design parameters to reduce the vibration of PCB. The simulation results indicate that the bandwidth and top cover layer thickness are highly related to the vibration in the top direction and the rotational moment generated from the head surface, respectively. Based on the analysis results, a novel MLCC was suggested and it exhibited reduced vibrational characteristics of PCB about 75 % compared with that of commercial MLCCs.

     

Assembly and evaluation of a SIL optical head for cover-layered incident NFR without disk contact with the bottom surface of a SIL

In the assembly of the solid immersion lens (SIL) optical head for cover-layered incident near-field recordings (NFRs), disk contact with the bottom surface of the SIL has previously been regarded as essential. This is because SIL optical heads are designed to interface with a cover layer. However, SILs can be contaminated and damaged by this contact. We present a new SIL optical head assembly method for cover-layered incident NFRs without disk contact with the bottom surface of the SIL. To achieve this, we added zoom optics to a Twyman–Green interferometer in the measurement beam optical path. Our assembly method eliminates SIL contamination problems and the assembly procedure becomes simple because of removing the disk contact process. In addition, it is not necessary to consider the aberrations induced by disk tilt and cover-layer thickness variation. The SIL optical head assembled by the proposed method has good optical performance satisfying the optical tolerances and the measured wavefront aberration is good agreement with simulations.     

Design and fabrication of diffractive optical elements by use of gray-scale photolithography

Diffractive optical elements (DOEs) are key components in the miniaturization of optical systems because of their planarity and extreme thinness. We demonstrate the fabrication of DOEs by use of gray-scale photolithography with a high-energy-beam sensitive glass photomask. We obtained DOE lenses with continuous phase profiles as small as 800 microm in diameter and 5.9 microm in the outermost grating pitch by selecting a suitable optical density for each height level and optimizing the process variables. Microlenses patterned with eight levels and replicated by UV embossing with the polymer master mold showed a diffraction efficiency of 81.5%, which was sufficiently high for the devices to be used as optical pickups. The effects of deviations in diffraction efficiency between the DOE height and profile design were analyzed.     

Enhancing performance of ZnO dye-sensitized solar cells by incorporation of multiwalled carbon nanotubes

ABSTRACT: A low-temperature, direct blending procedure was used to prepare composite films consisting of zinc oxide [ZnO] nanoparticles and multiwalled carbon nanotubes [MWNTs]. The mesoporous ZnO/MWNT films were fabricated into the working electrodes of dye-sensitized solar cells [DSSCs]. The pristine MWNTs were modified by an air oxidation or a mixed acid oxidation treatment before use. The mixed acid treatment resulted in the disentanglement of MWNTs and facilitated the dispersion of MWNTs in the ZnO matrix. The effects of surface property and loading of MWNTs on DSSC performance were investigated. The performance of DSSCs was found to depend greatly on the type and the amount of MWNTs incorporated. At a loading of 0.01 wt%, the acid-treated MWNTs were able to increase the power conversion efficiency of fabricated cells from 2.11% (without MWNTs) to 2.70%.     

Thickness tolerance compensation of SIL first surface near-field recording with replicated lens on SIL

In this paper, we propose a novel optics design for improving the thickness tolerance of a super-hemispherical solid immersion lens (SIL) that is usually used in near-field recording for high data density. To obtain the improved thickness tolerance of a SIL and a high numerical aperture simultaneously, an aspheric replicated lens is added on the SIL. Using an additional aspheric replicated lens, spherical aberration which induces the tight thickness tolerance of the SIL is effectively reduced, therefore it was able to improve the thickness tolerance of the SIL, maintaining high NA equal to that of super-hemispherical SIL. In addition, in this paper, other various tolerances such as decenter and tilt are considered to make sure of the possibility of fabrication.     

Design of near-field recording optics using truncated hemispherical SIL with cover-layer incident dual recording layers

In this paper, we propose a novel optics design for media inside near-field recording (NFR) using a truncated hemispherical solid immersion lens (HMS). To obtain strong advantage of data protection and high data capacity simultaneously, a truncated HMS based near field optics with cover-layer incident dual recording layers is designed. In this design, to improve the small optical tolerance of the truncated HMS unit and to adjust dual focusing positions, an additional aspheric lens surface is added on top of the truncated HMS and it is combined with zoom optics composed of two single lenses having a low numerical aperture (NA). Also, to compensate for chromatic aberration, which is a serious problem for optics using a blue laser diode, a diffractive optical element is also designed. Using zoom optics, an additional aspheric lens surface, and a diffractive optical element together, the wavefront aberration and chromatic aberration are effectively reduced in a broad range of cover-layer thicknesses and wavelength variations. In addition, in this paper, the effect of a gap induced aberration is investigated by analyzing the different behavior of each TM and TE wave for the cover-layer incident NFR optics.Paper presented at the 15th Annual Symposium on Information Storage and Processing Systems, Santa Clara, CA, USA, 28–29 June, 2005.     

Effects of fabrication errors in the diffractive optical element on the modulation transfer function of a hybrid lens

Diffractive optical elements (DOEs) are often used to improve the performance of optical systems. However, when a blazed DOE is machined, shape errors can be generated in the discontinuity region of the DOE due to the finite radius of the processing tool. We simulated the effects of this shape error on the optical path and modulation transfer function (MTF) in a hybrid lens for a compact camera module. The decrease rate of the MTF was larger in the low-spatial-frequency domain and when the light entered at a low incident angle.