Nanyang Technological University

Ntu Ventures Pte. Ltd.

Datamark Technologies Pte Ltd

Siu Chung Tam

Yee Loy Lam

Yan Zhou

Yuen Chuen Chan

Anthony Tung Shuen Ho

Zhisheng Yun

Jian Hui Gu

Boon Siew Ooi

A method for embedding an entire image, audio or video watermark sequence within another image, audio or video data sequence with minimum loss of data quality is presented. The method exploits the de-correlation property of data coefficients in the orthogonal transform domain, similar to the application in data compression through transform coding. The present invention describes the usage of a Discrete Cosine Transform as the embedding domain. However, other orthogonal transforms such as Fourier, Walsh-Hadamard, Haar, Sine and Wavelet can also be used for this operation. A unique key derived adaptively from spatial locations registering the thresholds of the ac transform energies is used to unlock or de-watermark the embedded image or audio sequence. Moreover, an exponential filter has been developed to compress and expand the watermark coefficients prior to the embedding and retrieval process. The method can be used in resolving multimedia copyright protection issues arising on the Internet and in the music industry, such as the inclusion of a company's logo or an artist's recorded voice. The method can also be incorporated as a built-in feature for digital recording devices, such as still and video cameras, as well as more recent devices such as VCD and DVD players. Moreover, the method can be applied to the commercial and service sectors, where security in transmission and reception of private information in terms of speech or image is of the utmost importance.

Methods for embedding image, audio and video watermarks in digital data

A semiconductor wafer with variable transmittance, serves as a saturable absorber for performing passive Q-switching in a laser system to produce laser pulses having defined output characteristics. By translating or rotating the semiconductor saturable absorber, loss properties of a laser cavity may be altered. In this manner, the output characteristics of the laser pulses can be varied without changing other parameters of laser operation. The output characteristics may include pulse duration, pulse repetition rate, peak power and average output power of the laser pulses. The semiconductor wafer can be made of doped or undoped GaAs, AlGaAs, InP, etc. Furthermore, the tunable Q-switch may simultaneously serve as an output coupler for the laser cavity.

Semiconductor passive Q-switch providing variable outputs

A pumping module for use in a solid state laser comprises an annular array of laser diode segments ( ) forming a passage ( ), each segment ( ) comprising an extended body supporting a laser diode array ( ) that extends along the longitudinal axis of the segment ( ) for directing light into the passage ( ) from an inner face ( ) of the annular array, wherein adjacent side faces of any two segments ( ) in the annular array are in sealing engagement. The inner faces ( ) of the array of segments ( ) form a continuous surface so that coolant can flow between a laser rod and the segments ( ) to reduce localized heating.

Pumping source

The present invention provides a novel technique based on gray scale mask patterning ( ), which requires only a single lithography and etching step ( ) to produce different thickness of SiO implantation mask ( ) in selected regions followed by a one step IID ( ) to achieve selective area intermixing. This novel, low cost, and simple technique can be applied for the fabrication of PICs in general, and WDM sources in particular. By applying a gray scale mask technique in IID in accordance with the present invention, the bandgap energy of a QW material can be tuned to different degrees across a wafer ( ). This enables not only the integration of monolithic multiple-wavelength lasers but further extends to integrate with modulators and couplers on a single chip. This technique can also be applied to ease the fabrication and design process of superluminescent diodes (SLDs) by expanding the gain spectrum to a maximum after epitaxial growth.

Quantum well intermixing

A method for sensing and analyzing topographic properties of an aspheric test element is disclosed. The principle of the measurement technique is to immerse the element under test into a container filled with liquid crystal. A polarized plane wave passes through front and back precisely processed glass plates of the container sandwiched between a polarizer and an analyzer. The two side plates are not transited by the plane wave of light but are deposited with conductive layers in order to generate an electrical field between them. This DC (direct current) external electrical field is supplied to help to align the molecular direction of the liquid crystal. In a thus-induced desired configuration, the molecular direction of liquid crystal is aligned to be perpendicular to the incident plane wave front. As the plane light wave propagates through the liquid crystal in the container, it will be divided into ordinary and extraordinary beams. These two beams will create interference behind the analyzer. In the presence of the aspheric optical element under test, which is not a uniaxial crystal, a compensatory interferogram will be formed. Analysis of the interferogram will allow the user to determine the topographic surface profile of the aspheric element under test.

Growing community of inventors

Singapore, Singapore

Siu Chung Tam