Satoshi Yanase

Focus tuning by liquid crystal lens in imaging system.

A quantitative study of the focus tuning by a liquid crystal lens in an imaging system composed of a camera module and the liquid crystal lens that performs the focusing function is reported. The resolving capability of the imaging system is investigated by analyzing the image of an ISO12233 chart formed by the system. Measurements show that with the focus tuning by the liquid crystal lens, the resolving power of the system can be very close to that of the camera module.

Low-Voltage-Driving Liquid Crystal Lens

An approximately 1 µm-thick thin insulation film is introduced into a liquid crystal lens cell, replacing the substrate between the patterned electrode and the liquid crystal layer. The distance between the electrodes decreases markedly, and the driving voltages decreases from several tens of volts to only approximately 3 V.

High recording performance of Co–Cr medium sputter‐deposited at high Ar pressure and high substrate temperature

Co–Cr films were prepared by sputter deposition at a high Ar pressure of 70 Pa with elevated substrate temperatures up to 400 °C. Films of 100 nm thickness were deposited using a 19 at. % Cr–Co target onto a well c‐axis oriented Ti underlayer prepared on glass disk substrates. The perpendicular coercivity, Hc⊥, of the films increased from 660 to 1940 Oe with increasing temperature. The films with high Hc⊥ exhibited a dense fine microstructure with distinct grain boundaries. The recording performance of the disk samples were measured by using a metal in gap type ring head, comparing with that of conventional Co–Cr films deposited at a low Ar pressure of 0.2 Pa. It was found that the high pressure deposited Co–Cr film exhibited higher output by more than 2 dB at the densities below 320 kFRPI (flux reversals per inch) compared with the conventional film with the same high coercivity. The D50* of as high as 250 kFRPI and the highest recordable density of over 600 kFRPI were confirmed for the new type of Co–Cr...

Molecular Orientation States and Optical Properties of Liquid Crystal Microlenses with an Asymmetric Electrode Structure

Liquid crystal (LC) microlenses are prepared using a pair of substrates with an asymmetric hole-patterned electrode structure. Their molecular orientation states and optical properties are studied by a simulation using the three-dimensional finite difference method (3D-FDM), and are also experimentally confirmed. It is found that a retardation distribution including two lens profiles for the center and outer regions of the hole-pattern is formed by the asymmetric electrode structure of the LC microlens. Focusing properties obtained in the experiments mainly correspond to those at the center region of the hole-pattern calculated by the molecular orientation simulation. Lens power can be improved and a bifocal lens can be achieved by using the asymmetric electrode structure and optimizing the combination of the hole-pattern diameters in the LC microlens.

Study on recording beyond 10 Gbit/in.2 with Co–Cr based perpendicular recording media

Recording of beyond 10 Gbit/in.2 was studied with Co–Cr based perpendicular recording media and ring heads. A simple recording simulation based on an M–H loop sheared by the demagnetizing field in the film suggested that a steeper M–H loop slope in the medium results in a higher output and resolution. It was found that recording with a metal in gap head with a gap length of as small as 0.15 μm on a Co–Cr20–Nb4–Pt5 medium with an M–H loop slope of 1.5/4π emu/Oe cm3 exhibited a high output and a high resolution. The obtained high signal-to-noise ratio and resolution suggested a possibility of recording beyond 10 Gbit/in.2 for a track pitch of 0.4 μm.

Relationship between lens properties and director orientation in a liquid crystal lens

Abstract Lenses with a homogeneously aligned liquid crystal having a Fresnel structure have been prepared by using a nematic with a positive dielectric anisotropy. Their focal length can be varied continuously from the value fe for an extraordinary ray to f o for an ordinary ray by applying an electric field across the lens cell. The effective refractive index of the lens where the director is aligned perpendicular to the grooves of the Fresnel structure becomes smaller than when the director is aligned parallel to the grooves. Then the liquid crystal lens has a characteristic aberration which could not be observed in a conventional glass lens; that is, the focal length of the lens becomes different according to the incidence of rays on the different parts of the lens. The properties of the liquid crystal lens can be improved by making the director orientation axially symmetric, in the form of a concentric circle, but the polarization component rotated 90° from the incident extraordinary ray appears when ...

Liquid-crystal variable-focus lenses with a spatially-distributed tilt angles

A pretilt angle controlling method by the density of rubbings using a tiny stylus is proposed. The control of the surface pretilt angle is achieved by rubbing a side-chain type polyimide film for a homeotropic alignment. Smooth liquid crystal (LC) director distribution in the bulk layer is successfully obtained even though the rough surface orientation. This approach is applied to LC cylindrical and rectangular lenses with a variable-focusing function. The distribution profile of the rubbing pitch (the reciprocal of the rubbing density) for small aberration is determined to be quadratic. The variable focusing function is successfully achieved in the LC rectangular lens, and the voltage dependence of the focal length is tried to be explained by the LC molecular reorientation behavior.

Variable-Focus Liquid Crystal Lenses Used in Imaging Systems as Focusing Elements

Liquid crystal (LC) lenses that have hole-patterned electrodes and are driven by two voltages used as imaging devices are reported. Two different LC lenses are applied in image formation systems. One LC lens is used with a polarizer in a relay lens scope, and another LC lens that is polarization independent is used in a TV lens. Both LC lenses play roles of focusing elements in lens systems; objects are separately brought into focus by the LC lenses. Very sharp black-and-white and color images are formed by the systems.

Measurement of Optical Aberrations of Liquid Crystal Lens

The dependences of the optical aberrations of the recently proposed low-voltage-driving liquid crystal lens on the amplitudes and frequency of the driving voltages are studied. The analysis results of the root mean square aberration of the lens suggest driving parameters that ensure both low aberrations and a wide focus range.

Molecular Orientation Analysis of a Design Concept for Optical Properties of Liquid Crystal Microlenses

The relationship between a liquid crystal (LC) molecular orientation state and the focusing properties of LC microlenses prepared using a pair of hole-patterned electrodes are studied. In particular, in order to obtain a large optical effect, molecular orientation and retardation distributions in the LC microlenses with a thick LC layer are investigated by experiments and simulations using the finite difference method (FDM). It is found that the LC microlens functions not only as a converging lens at a low applied voltage but also as a diverging lens at a high applied voltage. The focal length of the LC microlens with D/t of 1/1 is shorter than that with 1/2, where D is the pattern diameter and t is the LC thickness. Dependences of the converging and diverging properties on the D/t values are successfully explained by the FDM simulations of the LC molecular orientation. In the case of large D/t values, the middle region of LC layers mainly contributes to the effective refractive index distribution of the LC microlens. On the other hand, the contribution of both surface regions is dominant when D/t becomes small. It seems that the LC molecular orientation outside the circular-pattern affects effectively to that inside the region with decreasing D/t values.