Method and apparatus for detecting defect information in a holographic image pattern
US4811409A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Mar 10, 1986 |
| Grant date | Mar 7, 1989 |
| Priority date | — |
| Expiry date | Mar 10, 2006 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N21/956
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method and an apparatus detect in a light pattern the presence of defects (10') in a photomask (10) to which the light pattern corresponds. An inspection area (36) that includes the light pattern is partitioned into stripe regions (72). The width (70) of a stripe region corresponds to the maximum extent of the image window (54) of a charge-coupled camera device (42) that is employed to scan continuously each stripe region at a nominally constant speed. Each stripe region is divided into a first array (90) of pixel elements (92) arranged in rows (94) and columns (96). The camera device comprises plural light detecting elements (84) that are arranged in a second array (82) of rows (86) and columns (88). The camera continuously traverses the columns of the first array in a direction along the length of the stripe region and acquires in row-by-row fashion quantities of charge which correspond to the intensities of the light present in the pixel elements with which the light detecting elements are aligned. The charge quantity measured for each pixel element in a row is shifted serially along a corresponding column of the second array in synchronism with, but in a direction opposite to…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.