Laser image contrast enhancement system

US6366403B1 · kind B1 · utility

Assignee

• The United States of America as represented by the Administrator of the National Aeronautics and Space Administration · US

Inventors

• Robert L. Kurtz · Barberton, US
• Richard R. Holmes · Guntersville, US
• William K. Witherow · Huntsville, US

Key dates

• Filing date: Feb 12, 2001
• Grant date: Apr 2, 2002
• Expiry date: Feb 12, 2021

Classification

• Technology area (CPC F): Mechanical Engineering; Lighting; Heating
• CPC primary: F27D2021/026
• WIPO field: Audio-visual technology
• WIPO sector: Electrical engineering

Abstract

An optical image enhancement system provides improved image contrast in imaging of a target in high temperature surroundings such as a furnace. The optical system includes a source of vertically polarized light such as laser and a beam splitter for receiving the light and directing the light toward the target. A retardation plate is affixed to a target-facing surface of the beam splitter and a vertical polarizer is disposed along a common optical path with the beam splitter between the retardation plate and the target. A horizontal polarizer, disposed in the common optical path, receives light passing through a surface of the beam splitter opposed to the target-facing surface. An image detector is disposed at one end of the optical path. A band pass filter having a band pass filter characteristic matching the frequency of the vertically polarized light source is disposed in the path between the horizontal polarizer and the image detector. The use of circular polarization, together with cross polarizers, enables the reflected light to be passed to the detector while blocking thermal radiation.