Browse Prior Art Database

Electro Optical Comparator

IP.com Disclosure Number: IPCOM000092459D
Original Publication Date: 1966-Nov-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Rottmann, HR: AUTHOR

Abstract

The apparatus measures the spacing between edges 1 and 2 of two opaque regions of partially transparent element 3. The device is useful, for example, in inspecting optical masks of the type that are used in photoetching.

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Electro Optical Comparator

The apparatus measures the spacing between edges 1 and 2 of two opaque regions of partially transparent element 3. The device is useful, for example, in inspecting optical masks of the type that are used in photoetching.

The apparatus includes two photocells 4 and 5 and an optical system that focuses light from test element 3 onto the photocells. The optical system includes microscopes 6 and 7, positioned near element 3, and fiberoptics 8 and 9 that transmit light from microscopes 6 and 7 to the region of photocells 4 and 5. Element 3 can be held in the position shown. For continuous inspection it can be mounted on a conveyor to move past microscopes 6 and 7 at a moderate speed.

A shutter mechanism interrupts the light on photocells 4 and 5. The shutter system includes movable belt 12. This belt has two groups of slits 13. Pairs of slits are spaced apart to be simultaneously between fiberoptics 8 and 9 and photocells 4 and 5. The spacing between pairs of slits differs by predetermined increments. Each pair of slits that is spaced together closer than edges 1 and 2 causes both photocells 4 and 5 to be illuminated at the same time. Each pair of slits that is spaced farther than edges 1 and 2 causes only one photocell at a time to be illuminated. The pairs are spaced progressively farther apart. Therefore as the belt moves past fiberoptics 8 and 9, there is a transition from a state in which both photocells 4 and 5 are simultaneously illum...