An approach with the capability of matching partial word image is proposed in this paper, to facilitate the issues of document image retrieval, such as detection of user-speci ed query words, and similarity measurement between documents. Each word image is represented by a feature string. Then, an inexact string matching technology is utilized to measure the similarity between the two feature strings generated from two word images, based on which we can estimate how one word image is relevant to the other one and thereby decide whether one is a portion of the other word. The approach is applied to two issues in the area of document information retrieval: word spotting and document similarity measurement. Experimental results on real document images show that it is a promising approach.
This paper reports the design, modeling, fabrication and testing of a novel variable optical attenuator for multi-channel power equalizers to be used in dense wavelength division multiplexed (DWDM) systems. The attenuator is fabricated by silicon surface micromachining technology and is then manually assembled and integrated with two single mode optical fibers that act as optical input and output. A 40 × 40 ?m2 mirror coated with gold is driven by a proprietary drawbridge structure to cut partially into the light path between two fibers, enabling the attenuation. The attenuator has a dimension of 0.6 × 1 mm2 excluding the fibers. It has 1.5 dB insertion loss and 45 dB attenuation range, and requires only 8 V driving voltage, showing that it is promising for DWDM applications. Optical and mechanical models of the attenuator have also been established. Although the models are developed with the initial intention of modeling the MEMS attenuator, they are also available to the other types of devices in which the preconditions of the models are satisfied.
The out-radial movements of pickup head in optical data storage systems are studied, and its influences on Push-pull track error signals and Differential Phase Detection (DPD) track error signals are analyzed.
Vibration analysis is an integral part of the design process for precise components, especially for higher density optical disk drives (e.g. DVD ROM/RAM). The designer often encounters challenges arising due to undesirable vibration modes in the components. The demands for precise track accessing and focusing are of importance in higher density optical disk drives. However, structural resonant vibration of mechanical components in the optical pickup head limits the tracking and focusing servo performances. Such tighter design specifications require the designer to have in-depth understanding of how structured resonance of the actuator in the optical pickup head responds to its tracking or focusing mechanism.