22 Oct 2004
The pick of this week's applications including a silicon prism that increases light coupling efficiency into a waveguide.
• Title: Permanent light coupling arrangement and method for use with thin silicon optical waveguides
Applicant: SI Optical, Inc, US
International application number: WO 2004/088724
Attaching a trapezoidal-shaped single-crystal silicon prism permanently to a thin silicon optical waveguide can improve light coupling efficiency into the waveguide, say the authors of application number WO 2004/088724. The waveguide is doped to give it a refractive index that is slightly less than the silicon prism coupler, which has a refractive index of 3.5. An evanescent coupling layer is also sandwiched between the prism and the waveguide. This layer has a lower refractive index than the two components surrounding it. The authors also disclose methods of manufacturing the prism.
• Title: Lighting assembly for a luminescence analysis apparatus, in particular a fluorescence microscope, and luminescence analysis apparatus equipped with such a lighting assembly
Applicant: Fraen Corporation, Italy
International application number: WO 2004/088387
An Italian firm is trying to patent a compact LED-based light source for fluorescence microscopes. Typically, fluorescence microscopes use lamp or laser-based sources which are expensive, bulky and consume a lot of energy. The applicants believe their source overcomes these problems. They mount an LED behind a collimator made of a transparent plastic material such as polycarbonate or PMMA. The entire housing can then be plugged in to the microscope to illuminate the sample.
• Title: Means of compensation to increase the contrast ratio of LCoS based video projection systems
Applicant: LightMaster Systems, US
International application number: WO 2004/088362
LightMaster of the US has come up with a way to increase the contrast ratio in LCoS displays. Such displays project the image from a microdisplay onto the screen. The applicants are patenting an arrangement containing a quarter waveplate, a half waveplate and a prism assembly all placed at specific angles with respect to the microdisplay. This is said to perform skew ray compensation as well as reduce residual retardation - two factors known to affect the contrast ratio.