A holographic device is under development that aims to improve light collection in solar cells. The aim is to explore the potential of using photopolymer holographic optical elements (HOEs) to collect light from a moving source, such as the sun, and redirect it for concentration by a holographic lens. A working range of 45° is targeted for such a device to be useful in solar applications without tracking. A photopolymer HOE is capable of efficiently redirecting light, but the angular selectivity of a single grating is usually of the order of one degree at the thicknesses required for high efficiency. The challenge here is to increase the angular and wavelength range of the gratings so that a reasonable number may be multiplexed and/or combined to create a device that can concentrate light incident from a large range of angles. In this paper, low spatial frequency holographic recording is explored to increase the angular and wavelength range of an individual grating. Ultimately, a combination of gratings will be used so that a broad range of angles of incidence are accepted. A design is proposed for the combination of such elements into a holographic solar collector. The first step in achieving this is optimization of recording at low spatial frequency. This requires a photopolymer material with unique properties, such as a fast monomer diffusion rate. This paper reports results on the efficiency of holograms recorded in an acrylamide-based photopolymer at low spatial frequencies (100, 200, and 300  l/mm). The diffraction efficiency and angular selectivity of recorded holograms have been studied for various photopolymer layer thicknesses and different intensities of the recording beams. A diffraction efficiency of over 80% was achieved at a spatial frequency of 200  l/mm. The optimum intensity of recording at this spatial frequency was found to be 1  mW/cm2. Individual gratings and focusing elements with high efficiency and FWHM angles of 3° are experimentally demonstrated.

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Using acrylamide-based photopolymers for fabrication of holographic optical elements in solar energy applications.

Pressure and temperature variations of natural gas flows in a pipeline may cause partial gas condensation Fluid phase behavior and prevailing conditions often make liquid appearance inevitable, which subjects the pipe flow to a higher pressure loss This study focuses on the hydrodynamic behavior of the common scenarios that may occur in natural gas pipelines For this purpose, a two-fluid model is used The expected flow patterns as well as their transitions are modeled with emphasis on the low-liquid loading character of such systems In addition, the work re-examines previous implementations of two-flow model for gas-condensate flow

Low-Liquid Loading Multiphase Flow in Natural Gas Pipelines

In exemplary implementations of this invention, a manufactured physical object includes surface features that encode information according to a code. Each respective surface feature consists of a bump on, or recess in, a surface of the object. Each respective surface feature by itself, regardless of any state of any other surface feature, encodes a sequence of multiple bits. The sequence is determined, at least in part, by a discrete elevation of the respective surface feature. At least three different discrete elevations of surface features are significant in the code. Also, one or more other parameters of the surface features may be significant in the code, such as discrete rotational orientation, discrete overall shape, discrete color, or presence or absence of the feature.

Methods and apparatus for encoded textures

Recent developments in holographic optical elements (HOEs)

In recent years, holographic optical elements have been introduced in different applications such as high-density data storage, interconnections, spatial and temporal filters and three-dimensional displays. Simultaneously, more sensitive, efficient and durable holographic materials have been developed. Thus it is necessary to analyze the characteristics of these elements in the holographic materials developed. In this paper a method to obtain holographic lenses in a photopolymer is presented. In order to obtain, reconstruct and analyze these lenses, an optical device was designed. Once the holographic lenses are obtained, the device allows us to capture the images provided by these lenses. The imaging quality of these lenses was evaluated by means of the modulation transfer function (MTF) and the contrast. Lenses of different focal lengths were recorded. The holographic lenses obtained had high diffraction efficiency and temporal stability. Moreover, the resolution was greater than that of other lenses wi...

Holographic lens recorded on photopolymers: fabrication and study of the image quality

Multilevel storage is the easiest two-dimensional storage technology. On the basis of recording and read-out optical
system of Digital Versatile Disc (DVD), by the method of multilevel run-length coding, the storage capacity can be
increased by 60 percent of DVD9's, reaching 14 Giga Bytes.
In order to meet the requirement of a 10 -4 raw Bit Error Rate (BER) of data readout, this paper presents a method of
multilevel run-length coding with changeable level numbers. This method can take advantage of run-length redundancy
to the utmost and reduce Inter-Symbol Interference (ISI) caused by multilevel run-length. Multilevel run-length coding
uses the method of two steps modulation. This paper introduces a coding method of DK (1, 9) and R=1 code rate.
Realized by Pulse Width Modulation, multilevel run-length modulation coding with changeable level has good
symmetry. Its readout characteristics are the same as that of DVD with normal run-length modulation, therefore the
servo control system needn't be changed. Also the signal can be recognized in two aspects respectively, run-length and
level. In the sample disc, average raw BER in the two aspects is less than 10 -3 .
Multilevel run-length modulation coding could be applied in various systems of run-length modulation coding. On the
basis of the structure and characteristics of the primitive system, the comprehensive efficiency of coding could be
increased by 33 to 50 percent.

Theory and practice of multilevel method in high-definition discs

A holographic element for the common CD pick-up to play DVD is designed in this paper. The focus of holographic element is the same as that of the objective lens of CD player. The holographic element is fixed before the objective lens. The focus of DVD player with this holographic element is 8.5 mm, the number aperture is 0.75, and the focusing beam spot is 0.5 um. DVD player with the holographic element is characteristic of compensating the main optical error met in the common CD player well.

Holographic element for CD pickup-to-play DVD

The present invention provides a multilevel read-only optical disk and the method for producing the same The multilevel read-only optical disk comprises a plurality of the recording pits, each of the longitudinal sections of the recording pits has a multilevel arbitrary shape; the areas of the longitudinal sections of the recording pits are not identical each other; the area of each of the longitudinal sections of the recording pits is defined by the following formula: S=∫h(x)dx, where S represents the area of each of the longitudinal sections of the recording pits, x represents the coordinate value along the width direction of the recording pits, h(x) represents the pit-depth distribution function of the longitudinal sections of the recording pits and the region of the integration covers the whole longitudinal sections of the recording pits Furthermore, the run length of the multilevel read-only optical disk is limited The present invention obtains the advantage of both multilevel storage technology and run length limited (RLL) codes They can improve prominently the storage capacity and data transfer rate of read-only optical disk without changing the wavelength of the laser and optical numerical aperture, and are most compatible with the conventional read-only optical disk system

Multilevel read-only optical disk and method for producing the same

Jitter is defined by the variation of each pit length and timing variations between data and clock frequency on discs. As a comprehensive item, it relates with error rate directly. In this paper, the definition, determined and influence factors of jitter n are analyzed. According to the analysis, measurement methods of jitter are provided. The precision of a method. The method's precision and demand are calculated and explained in detail.

Analysis and study on measurement of jitter and its precision

In Blu-ray Disc Optical Pick-up, the collimating and beam shaping play a significant role for laser beam process. So this
paper firstly gives out a collimating and beam shaping system according to China manufacture situation. And then based
on Laser Optics and Fourier Optics, this paper improves the calculation method of energy coupling efficiency for
collimator lens. At last, it builds a simple Interference Instrument which is used for adjusting the collimator lens and
beam shaper. This apparatus is built based on the theory of interference theory. The simplest example of an
electromagnetic wave is the plane wave. The plane wave is produced by a monochromatic point source at infinity and is
approximated by a collimated light source. Here the paper uses this Interference Instrument to assemble the collimator
lens with laser diode and check the quality of the beam shaping. Meanwhile this collimating and beam shaping system
can be produced easily in China, as it is suitable for Chinese optical element manufacture skill lever and can be precise
assembled by using simple instruments. So it will make that producing BD OPU in China with a lower cost comes true.

Longfa Pan

Papers

Theory and practice of multilevel method in high-definition discs

Holographic element for CD pickup-to-play DVD

Multilevel read-only optical disk and method for producing the same

Analysis and study on measurement of jitter and its precision

Collimating and Beam Shaping System for BD Optical Pick-up