Shinichi Kadowaki

Novel one-beam tracking detection method for dual-layer blu-ray discs

In this paper, we propose a new advanced push–pull (APP) method as a new one-beam tracking detection method suitable for a dual-layer Blu-ray disc (BD) system. This method overcomes two issues. One of them is tracking error signal (TES) offset at the boundary between recorded tracks and unrecorded tracks, and the other is TES offset caused by the stray lights from the other layer of dual-layer discs. The new APP-TES is stable at the boundary in the dual-layer BD system, because the dividing area of a far-field pattern is optimized and the detecting areas are allocated to avoid stray lights from the other layer. Its stable characteristics are confirmed experimentally.

Holographic optical element for an optical disk head with spot-size detection servo optics

A CGH construction of a holographic optical element (HOE) for an optical disk head with spot-size detection by means of superimposing two Fresnel zone plates is studied. Optimum parameter values for the ratio of segment to grating pitch (duty) and grating height are clarified from the viewpoint of total light power efficiency in the round trip optical system. The influences of higher-order diffracted beams near the first-order diffracted beams used to get signals on signal detection are shown to be small. The HOEs with almost optimum parameter values are fabricated and the desired diffracted spots, the expected total light power efficiency, and the small influence of higher-order diffracted beams are observed.

L‐9: Late‐News Paper: Laser Projection Display with Low Electric Consumption and Wide Color Gamut by Using Efficient Green SHG Laser and New Illumination Optics

air-cooled RGB lasers including a compact and efficient green SHG laser and new illumination optics for speckle noise reduction, we developed advanced laser projection engine. A prototype of laser rear projection display with low electric consumption (about 50W) for light sources and wide color gamut (137%NTSC) was realized. 1. Introduction the last decade, several different micro-display technologies (LCD, DMD and LCOS) have been developed and projection displays captured the large screen market for business and home theater. Most projection displays are now using lamps as light sources, such as high-pressure mercury lamps and metal halide lamps. Laser light sources are attractive for projection displays. Projection displays based on RGB lasers can provide extremely wide color expression with the narrow spectrum of lasers. Due to small etendue, laser lights are projected with high efficiency. Lasers have longer life time and faster response time than lamps. As high brightness and high power efficiency of lasers contribute to downsizing systems and improving electric efficiency, laser projection displays will find wide applications (1-3). However, for realizing laser displays there are two problems. The one is a suitable green laser with high efficiency, high power and compact size. As there are no green diode lasers and conventional green lasers for high output power need big mechanisms such as water-cooling devices, it is difficult to downsize and to decrease electric consumption. The other problem is an interference phenomenon called speckle. As lasers have high coherency, speckle noises are superposed on projected images (4). We overcome these problems and demonstrate a laser rear projection display with low electric consumption.

Integrated holographic optical pickup head with wide allowance range

We propose an integrated hybrid device based on spot-size detection method for holographic optical pickup head and discuss allowances of the misalignment with laser and photodetector. The integrated hybrid device with parallel-shaped photodetector is found to permit positional misalignment of over 200 µm.

Lens Shift Correction in Tracking Servo System for Digital Versatile Rewritable Disc

In this paper the development of tracking offset correction for playback of a digital versatile rewritable disc (so called DVD-RAM), is described. The slim drive, having a small optical pick-up head with a small objective lens, is easily influenced by the deviation of the push-pull tracking error signal due to lens shift. The DVD-RAM disk format provides information not only on the amount of lens shift using the push-pull tracking error signal of address marks to correct tracking deviation, but also an opportunity to determine the optimum initial lens position using the differential phase tracking error signal.

Recent advances in optical pickup head with holographic optical elements

Recent advances in optical pickup heads using holographic optical elements (HOEs) are reviewed, with emphasis on a practical servo-signal detection system that can realize compact integration of HOE, laser diode, photodetectors, and objective lens. This paper presents a new type of holographic servo method that employs a blazed HOE placed in close proximity to the objective lens so that wide allowance range of the optical system is maintained, thus allowing the lens and HOE to move simultaneously. The blazed HOE and the integrated optical system are analyzed and discussed in detail.

A very small holographic optical pick-up head with a movable single-assembly optical system

A very small holographic optical pick-up head with a movable single-assembly optical system was proposed. The optical system measures 11 mm(W)×4 mm(D)×4 mm(H) and weighs only 0.34 grams. The basic performance of the optical system mounted on a conventional actuator was demonstrated experimentally.

Computational analysis of a holographic optical head configuration

The best configuration for holographic optical heads for compact disk players is discussed from the viewpoint of considering the misalignment allowance for head components. Focus-error and trackingerror signals of the proposed head configurations are simulated with a ray-tracing method and by using optical cross transfer function theory. The misalignment allowance for the head components, such as the objective lens, the holographic optical element, and the photodetector, are calculated for several configurations. The misalignment allowance is found to increase greatly when the holographic optical element is placed in close proximity to the objective lens and then when this assembly is moved as a unit.

P‐206L: Late‐News Poster: Low Electric Consumption 3.6W Green SHG Laser Light Source Applicable to Laser Projection Systems

Highly-efficient fully air-cooled green laser light source with frequency doubling module is reported. As a result, 3.6 watts green laser light generation with about 9% wall-plug efficiency is achieved. By using fully air-cooled RGB lasers including the green SHG (Second Harmonic Generation) laser and illumination optics for speckle noise reduction, a laser projection engine is prototyped. A laser rear-projection system with this laser projection engine shows several merits; wide color gamut (133%NTSC), 61inch large screen size, and low electric power consumption (less than 100W, at 650cd/m2).

Development of Integrated Optical Unit for Large Storage Capacity Floppy Disk

A small integrated optical unit suitable for a large storage capacity floppy disk drive is proposed. The optical unit is 6.8 mm wide, 3.3 mm deep, and 3.0 mm high. The distance between the laser diode and the focused beam on the disk is only 4.0 mm. The optical unit consists of two components, a lens unit and a laser-detector unit. In this optical unit, with the beam slanting incident on the disk, the reflected beam takes another path. Thus, a diffraction grating, a lens, and a deflector can be integrated into one component. The optical unit allows wide disk tilting of up to 2.4 degrees.