Browse Prior Art Database

Photoelectric Measurement of Gap Angle and Cap Length of Ferrite Cores

IP.com Disclosure Number: IPCOM000074687D
Original Publication Date: 1971-May-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Nauth, HG: AUTHOR

Abstract

In magnetic heads for disk storage, the read/write gap of the tiny ferrite core must be perpendicular to the reference side plane of the core. The length of the R/W gap which is to be about a few microns must also be exactly controlled. The specifications for the gap angle, as well as for the gap length, are so narrow that previous less exact measuring methods result in high costs for scrap, measuring time, and manpower.

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Photoelectric Measurement of Gap Angle and Cap Length of Ferrite Cores

In magnetic heads for disk storage, the read/write gap of the tiny ferrite core must be perpendicular to the reference side plane of the core. The length of the R/W gap which is to be about a few microns must also be exactly controlled. The specifications for the gap angle, as well as for the gap length, are so narrow that previous less exact measuring methods result in high costs for scrap, measuring time, and manpower.

For mass production, gap angle and gap length are simultaneously measured by two photoelectric microscopes placed along the same optical axis perpendicularly to the reference side plane of the cores. The ferrite cores are moved serially across the optical axis with a velocity of more than 10 cm per second. When the scanning light beam of each microscope detects the first gap edge of a moving core, the beam is electrically deflected to follow this edge. Thereafter, one of the scanning microscopes releases the first edge of the gap and follows the second one. The difference of the currents deflecting the light beams is a measure first of the gap angle and then of the gap width.

The upper drawing perspectively shows ferrite core 1 with gap 2 moving across the optical axis of the two adjacent photoelectric microscopes M1, M2. Coaxial light beams 3, 4 represent very narrow light spots scanning independently of each other along the two side planes of the ferrite core.

If the angle between gap and reference plane 5 differs from 90 (top view of the core in lower drawing), corresponding edges K1, K1' on opposite side planes of the core are displaced by a distanc...