Browse Prior Art Database

Sequential Optical Inspection Technique

IP.com Disclosure Number: IPCOM000095117D
Original Publication Date: 1965-Sep-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Rottman, HR: AUTHOR

Abstract

Printed circuit boards are inspected by optically comparing each board with the board just previously inspected.

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Sequential Optical Inspection Technique

Printed circuit boards are inspected by optically comparing each board with the board just previously inspected.

The drawing shows identical printed circuit boards 1, 2, and 3. Board 3 has defect 4 which is to be identified by inspection. In operation, the boards are moved from station to station by manual or automatic devices, not shown, and compared at inspection station 5. Each board is compared with the preceding board, and if these are identical, is then compared with the succeeding board. Any mismatch is indicative of a defect.

Boards 1 and 2 are mounted in a fixed relationship to one another at inspection station 5, where they are subjected to identical optical scans by scanning mechanism 6. Boards 1 and 2 are transparent while the printed circuits on them are not. As the optical scanning takes place, photomultipliers 7 and 8 receive transmitted light signals characteristic of the related boards.

Since boards 1 and 2 are identical, they provide identical signals to photomultipliers 7 and 8 during each interval of scanning.

These equal signals are applied to Exclusive-Or 9 in which they cancel. After completion of the inspections of boards 1 and 2, board 1 is accepted, board 2 is moved to the left scanning position and board 3 is moved into the right scanning position. Scanner 6 begins a scan of the boards, providing for a time similar transmitted light signals to photomultipliers 7 and 8. When the scan reaches the de...