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Patent highlights

16 Sep 2004

The pick of this week's patent applications including an optical sensor which measures the velocity of an aircraft.

•  Title: Gas velocity sensor
Applicant: BAE Systems, UK
International application number: WO 2004/077067
An optical alternative to the Pitot tubes which measure the velocity of an aircraft is revealed in patent application WO 2004/077067. The system uses a diode-pumped Nd:YLF laser operating at 355 nm to illuminate the air and collection optics to pass the scattered light into a Fabry-Perot interferometer. "If the airstream is flowing, the backscattered light will be subject to a Doppler shift," explain the authors. "This results in concentric rings in the interference pattern shifting to slightly different radii." The changes in the pattern are monitored by a photodetector and the authors use these variations to calculate the velocity of the flowing airstream.

•  Title: Production of tunable picosecond light impulses in a visible spectral range
Applicant: Toptica Photonics AG, Germany
International application number: WO 2004/077142
Toptica of Germany is trying to patent an optical system which produces picosecond pulses at visible wavelengths. The firm reckons such a system is an ideal light source for time-resolved fluorescence spectroscopy. The system uses a laser which emits infrared femtosecond pulses and an optical frequency converter. The authors add that an optical stretcher increases the duration of the visible pulses to a least one picosecond.

•  Title: Laser machining using an active assist gas
Applicant: XSiL Technology, Ireland
International application number: WO 2004/079810
Laser micro-machining firm XSiL is looking to improve the dicing of silicon wafers. The Dublin-based firm uses laser beam of less than 550 nm to dice silicon wafers in the presence of a halogen gas, such as sulphur hexafluoride (SF6). By focusing the laser at a power density above the ablation threshold of silicon, the gas reacts with the workpiece at and around the focal spot. Machining speed and quality are said to increase, boosting the strength of resulting dies.

•  Title: Optical reading apparatus and method of reading data
Applicant: Philips Electronics, the Netherlands
International application number: WO 2004/068177
DVD players and recorders may benefit from apparatus proposed by European electronics giant Philips. The Dutch firm's design uses a nonlinear optical element to improve the signal-to-noise ratio of optical read/write devices. Reflected light from the surface of the optical carrier (for example a DVD disc) passes through the nonlinear element before being focussed on to the detector.

Jacqueline Hewett is technology editor on Optics.org and Opto & Laser Europe magazine.

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