Article having a birefringent surface and microstructured features having a variable pitch or angles for use as a blur filter

US7418202B2 · kind B2 · utility

Assignee

• 3M INNOVATIVE PROPERTIES COMPANY · US

Inventors

• Rolf W. Biernath · Wyoming, US
• Robert L. Brott · Woodbury, US
• William W. Merrill · White Bear Lake, US
• John S. Huizinga · Dellwood, US
• William B. Black · Eagan, US

Key dates

• Filing date: Aug 4, 2005
• Grant date: Aug 26, 2008
• Expiry date: Nov 26, 2026

Classification

• Technology area (CPC G): Physics
• CPC primary: G02B27/46
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

An optical low pass filter or blur filter, and method of making the filters, using an article having a birefringent surface for refracting incoming light when used with an image sensor. The birefringent surface of the article, such as a film, is structured or tilted such that, when the blur filter is placed within an optical path between a lens and the image sensor, the birefringent surface causes refraction of a light signal in the optical path into multiple light signals each being incident upon different sub-pixels within the pixels in the image sensor to prevent or reduce artifacts, such as undesirable color moiré effects, in the resulting digital image. The structures on the surface have a variable pitch or angles. The variable pitch can include a periodic, aperiodic, or quasi-aperiodic pitch, to reduce diffractive artifacts in the resulting image.