Papers by Keyword: Holography

Abstract: In this paper, we propose a new approach for fabrication processes of microstructures composed of diffractive optical elements (DOE) and security elements. The holographic lithography is combined with laser lithography to obtain highly secured holographic labels for products protection. The secret key is an untraceable and hardly reproducible geometry and can be embedded in the labels or stickers to increase the level of security and diminish the possibility of products counterfeiting. In our process, the holographic structure composed of DOEs, and the key are designed separately by two authorized designers and recombined using double exposure followed by a single development step. The layout of microstructures that composes the security key are known only by the designer.

Abstract: Digital holography can record 3-D image of the object by using one CCD camera. Surface shape can be measured by changing angles of the object-illuminating mirror. But the measured signals are wrapped because of the periodicity of a sinusoidal function, and then phase unwrapping is needed. We have developed a new modified phase unwrapping method and applied it to surface measurement. Unwrapping errors were significantly reduced in comparison to application of the previous method.

Abstract: The relationship of color display system and digital color reconstruction of color holography is discussed based on CIE color matching theory. With the general color display space-sRGB, this research calculated the three primary wavelengths as record and reconstruction wavelength. Based on the relationship between the RGB color values of object and the amplitude of object light, the computation method of three recording primary color and the color values of reconstruction color hologram is presented and verified by the experiment.

Abstract: Two image processing methods for the detection of particle based on digital holography are presented and compared. The image processing methods are developed based on edge detection and threshold based segmentation. The proposed methods have been applied on reconstructed images of holograms of ceramic beads and certified microspheres. Particle size distribution obtained for both methods are found to be in good agreement with the actual size, but the processing speed for threshold based detection has found to be faster in compared to the edge detection method.

Abstract: The paper deals with experimental simulation measuring and the analysis of defect distribution in passenger car tire under dynamic loading. The main reason for detection of defect extension is to recognize an influence of closed air, small bubbles, separations in tire and it is mainly connected with its quality during its service in a vehicle in terms of road safety. This analysis should help constructors to solve critical conditions in tire casing, whether material selection and individual components proportions are suitable and fit or even the whole construction of tire casing is suitable. The reason for detection of internal defects in tire casing is to avoid the wear of those tires which already contain some internal defects and already recognised separations, which could propagate during the movement of vehicles. This is closely connected with the occurrence of tire destruction and the main purpose is to prevent its critical status and later vehicle crash and human life menace.

Abstract: Aiming at the problem that security of digital watermarking is imperfect, a new digital watermarking algorithm based on holography is put forward. In embedment watermarking stage, first, original watermarking information is divided into two parts: amplitude and phase information. Then, a hologram which will be used as new watermarking information is generated by interference of the phase information light and the reference beam, and the amplitude information will be the key when original watermarking is extracted. At last, host image is transformed by the multilevel structures wavelet transform, and the new watermarking information is embedded into its suitable wavelet domain. In extraction watermarking information stage, the original watermarking information is obtained by the extracted watermarking information combined with the amplitude information. The theory and simulation show our algorithm has excellent performance in security, shear resistance and anti interference of white noise.

Abstract: Centrifugal nozzle is an important part of an areoengine in which fuel atomization has strong influence on engine performance. For investigating the fuel spray characteristics, a promising method named off-axis particle holographic measuring system is used here. Characteristics of the nonevaporating spray ejected from a new type of centrifugal nozzle which would be used in the near future are obtained under various injection conditions. By automatic analysis of the holographic reconstructed droplets images, a hollow-cone shape spray with most droplets concentrated in the surface of the cone is observed, and the spray cone angle, droplet sizes and their spatial locations in concerned region are obtained quantitativly. In the near region of the nozzle exit, droplets show greater SMD value, while at a certain distance from the nozzle, the droplets SMD differences become unconspicuous which shows a better atomization. These informations are helpful to understand characteristics of the centrifugal nozzle and offer a database for validating the spray simulation code.

Abstract: According the radial flutter extension structure problems in commonly used fire alarm system, a novel topology structure of fire alarm systems based-on holographic crystal forms was proposed. It was composed of multiple devices, including intelligent fire detectors, which can communicate with each other, record fire information and judge, alarms, security, evacuation lights etc. Each device can record all of the information so as to form the hologram. These devices on each floor level in buildings and decorated with vertical layout in the staircase, so that fire alarm system topology based-on holographic crystal forms was set up. The systems can ensure the normal operation of other devices in case that central control equipment failed in extreme cases. And then the automatic fire safety equipment continued to automatically control fire rescue and guide the staff in the correct escape route. Moreover, when a device or a line goes wrong, only failure equipment or system was cut off line, and others were still able to keep communications. Compared with other methods, this new system does not affect the normal equipment of the work.

Abstract: Ceramics are inorganic materials fabricated by a high-temperature chemical reaction. Most ceramics are oxides, but the term is also used for silicides, nitrides and oxynitrides, hybrids and other inorganic materials. It is convenient to consider ceramics that are essentially silicates, called traditional ceramics, separately from all of the others. In the ceramic industry testing systems are seldom employed for detecting on-line the presence of defects in ceramic tiles. Defects in the ceramic body are usually originated during the pressing stage due to the incorrect use of process parameters or to the improper selection of raw materials. These defects are generally characterized by the inclusion of heterogeneous materials or agglomerates, which decreases the structural strength jeopardizing the final quality of the produced piece. Disagreeable repercussions on the sale market, especially on higher-quality ceramics such as porcelain, are characterized by the lack of specific nondestructive testing (NDT) techniques that “certify”, pre-emptive, the quality of the produced piece. The integration of IRT and HI for the NDT of a green ceramic tile with both fabricated and real defects (cracks caused by the natural shrinkage process), allowed us to produce a clear “defects map”.

Abstract: We show how digital holographic interferometry in the Long Wave InfraRed spectral range (LWIR) can be used for the investigation of mechanical structures. The 10.6 μm radiation is produced by a CO2 Laser. Experimental results showing that the method can be used to locate defects in a panel are presented and advantages and disadvantages of this approach are discussed.