Surface inspection tool

US6704435B1 · kind B1 · utility

Assignee

• International Business Machines Corporation · US

Inventors

• Wayne Isami Imaino · San Jose, US
• Anthony Juliana, Jr. · San Jose, US
• Milton Russell Latta · San Jose, US
• Charles H. Lee · Kannapolis, US
• Wai Cheung Leung · San Jose, US
• Hal J. Rosen · Los Gatos, US
• Steven W. Meeks · Fremont, US
• Richard Sonningfeld · San Jose, US

Key dates

• Filing date: Apr 28, 1997
• Grant date: Mar 9, 2004
• Expiry date: Apr 15, 2020

Classification

• Technology area (CPC G): Physics
• CPC primary: G01N21/9506
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A laser based inspection tool (LIT) for inspecting planar surfaces is described. In a preferred embodiment the LIT can simultaneously inspect both planar surfaces of disks for use in disk drives. In one embodiment of the invention, the incident beam is directed onto the surface to be inspected at an angle slightly offset from perpendicular so that the reflected beam is physically separated from the incident beam. The reflected beam is routed to a detector which converts the intensity of the reflected into an analog signal. The analog signal is sampled and digitized to generate pixel data stored in a buffer. Various analyses are performed on the data including calculating a rate of change in the pixel data. If the rate of change in the pixel data exceeds a selected threshold that indicates a possible defect if it occurs in the data area of the disk.