This study investigates the characteristics of luminescent solar concentrators (LSCs) with structured gratings. By creating the optical model, the characteristics of the proposed LSC were simulated. They consist of the analyses of different grating periods and dye combinations. The LSC devices were fabricated and verified. The results show that the simulation and experiment have good consistence.
This study proposes a Fresnel lens with multiple focus modes by combining the technology of polymer stabilized liquid crystals (PSLC) with the novel electrode design, which contains the Fresnel zone electrodes and complementary electrodes. The device was fabricated according the methods including the photolithography for the electrode patterns, the LC cell assembly, and the UV exposure for the PLSC curing. Experimental results show that the diffraction effects of the lens can be switched under different operation modes. It can accordingly provide three focal lengths of 25 cm, 32 cm, and 39.5 cm.
This paper presents an optical head design that minimizes the component number and miniaturizes the head dimension
by using a novel reflective prism-type holographic optical element (PT-HOE) for the next-generation high-density bluelight
system with small form factor (SFF). The PT-HOE combines four functions, serving as a folding mirror, a beamsplitter,
an aberration correction element, and a servo-signal generation device, which are generally required for a
conventional optical pickup head (OPH). It greatly simplifies the system complication and assembly procedure of an
OPH. Simulations give the satisfactory results and show the feasibility for realizing a high-density SFF OPH with a
simple and compact configuration.
KEYWORDS: Servomechanisms, Head, Semiconductor lasers, Digital video discs, Digital signal processing, Control systems, Objectives, Laser systems engineering, Interference (communication), Optical engineering
The conventional measuring system of laser feedback noise for an optical pickup was specifically implemented only for laser diodes by using a static optical system. With no closed-loop servo control, it is impossible to measure the genuine laser noise distribution of a pickup while operating in an optical drive. By modifying the optical system of a commercial pickup, this study built up a system that was integrated with precision mechanical design, optical design, servo control design, and opto-electronic signal inspection for providing dynamic real-time laser feedback noise measurement. Using this system, some experimental results have been observed. The laser feedback noise is responsible to the focusing point within the linear range of an optical pickup head. It has the maximum value while the lens is on the best focus. The higher the environmental temperature, the noisier the laser output will be. Besides, the central frequency of noise is dependent on the disk rotation speed, and the noise level is reducible by increasing the disk rotation speed.
The conventional measuring system of laser feedback noise for an optical pickup was implemented specifically only for laser diodes by using a static optical system. With no close-loop servo control, it is impossible to measure the genuine laser noise distribution of a pickup while operating in an optical drive. With modifying the optical system of a commercial pickup, this study was integrated with precision mechanical design, optical design, servo control design, and opto-electronic signal measurement for providing a dynamic real-time laser feedback noise measurement system. With this system, some experimental results were obtained. The laser feedback noise is responsible to the focusing point within the linear range of an optical pickup head. It has the maximum value while the lens is on the best focus. The central frequency of noise is dependent on the disk rotation speed and the noise level is reducible by increasing the disk rotation speed.
This paper presents a novel light modulator based on the technologies of liquid crystal diffractive optical elements (LCDOE) for a recordable optical pickup head with switching capability on single-beam data writing and multiple-beam data retrieving. The method of Dammann's phase grating was adopted on the LCDOE pattern design for generating seven diffracted orders. The diffraction pattern was etched on transparent conducting glass substrate to act as the electrodes of the modulator and the LCDOE was made by the fabrication processes of liquid crystal devices.
The experimental results show that the multiple-beam LCDOE has the function of generating seven diffracted beams with equal light intensities while applying a voltage to the device. By adjusting the amplitude of the voltage, that accordingly changes the difference between the refractive indices of the ordinary and the extra-ordinary rays, the diffraction efficiency can be properly optimized. The switching capability is controllable by turning the voltage on or off. Besides, the polarization-selective effect is verified and an advanced multiple-beam pickup design in integrated type is also proposed.
This module combined the techniques of MEMS, near-field optics, fly head, and multiple beam. It organized the optical component and waveguide into a substrate. It integrated the multiple beam optical module for near-field high density recording, used the optics characteristic of the diffractive optical element, (DOE), generate multiple beams equally on the module, and reduce the spot size by using the near field optics. Simultaneously, quite a bit of information is recorded on the tracks of high density optical discs.
This paper addresses the design and construction of an interesting polarization-switched diffractive optical element (DOE) that generates multiple beams incident on the disk and acts as a beamsplitter and servo-generating element for light returning from the disk. In this way, data speed is increased proportional to the number of beams on the disk, and, by combining three functions into a single optical element, allows a more compact and lightweight pickup to be realized. The polarization-switched DOE is constructed as a sandwich of two pieces of some birefringent material, with one rotated by 90 degrees relative to the other so that the ordinary and extraordinary axes are interchanged, and with a common index-match layer between them. A diffractive pattern is etched into each of the two birefringent pieces. Linearly polarized light traveling from the laser towards the disk is diffracted into multiple beams by one of the diffractive patterns while experiencing no diffraction from the other. Travelling the roundtrip from the DOE to the disk and back to the DOE, the light traverses a quarter-wave retarder two times thereby rotating its polarization direction by 90 degrees. It now experiences no diffraction from the multiple beam diffraction layer, but is diffracted by the second diffraction layer, which steers it onto the photodetectors and alters the beam to create useful focus and tracking error signals. This design is important in that it provides a way for two diffractive surfaces, each acting independently with high efficiency on orthogonal polarizations of light, to be combined into a single element. Implementation and application to a multiple-beam holographic pickup head module are presented.
We describe the design of a single diffractive LCD element placed adjacent to the objective lens that can be addressed to provide the required spherical aberration (SA) compensation for a plurality of disk substrate thicknesses. It is now commonplace that optical disk drives must be able to handle disks of more than one substrate thickness. The major problem is compensating for the SA introduced when the highly corrected objective lens is used with a disk substrate thickness other than that which it was specifically designed for. An abundance of methods for solving this problem in the specific case of CD/DVD backward compatibility exist in the literature; we use an active device to extend this to include HD-DVD as well.