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Indexer Position Check for Disk Measurement System

IP.com Disclosure Number: IPCOM000061215D
Original Publication Date: 1986-Jul-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Christie, RA: AUTHOR

Abstract

The procedure measures the distance the center of a disk-holding fixture (hereafter "hub") travels from the "home" position to the center of the x-ray beam within an x-ray fluorescence thickness tester. This parameter is important to the translation of coordinate systems for disk alignment. The problem arises because the hub cannot travel fully under the beam due to the tester's mechanical limitations. This method is essentially that of measuring the distance from "home" to a known point on a special disk (Fig. 1) by the following procedure, then adding the radius of that point to get to the center of the hub. xhome-to-center = xhome-to-point + xpoint-to-center This is down at two places for better accuracy.

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Indexer Position Check for Disk Measurement System

The procedure measures the distance the center of a disk-holding fixture (hereafter "hub") travels from the "home" position to the center of the x-ray beam within an x-ray fluorescence thickness tester. This parameter is important to the translation of coordinate systems for disk alignment. The problem arises because the hub cannot travel fully under the beam due to the tester's mechanical limitations. This method is essentially that of measuring the distance from "home" to a known point on a special disk (Fig. 1) by the following procedure, then adding the radius of that point to get to the center of the hub. xhome-to-center = xhome-to-point + xpoint-to-center This is down at two places for better accuracy. The special disk used in this procedure is one that has had two bands of coating precisely removed with the radius to each coating edge measured to 0.001 inch and inscribed on the disk. As seen in Fig. 1, the coating is removed between A and B and between C and D. To obtain xhome-to-point, the author uses x = x~ + vt. The hub is placed at an x~ so the x-ray beam is just off the edge of the disk. The tester's multichannel analyzer (MCA) is then put into multichannel scaling mode to plot a histogram of x-ray counts versus time. The disk is passed radially under the x-ray beam at a very slow speed v so that an x-ray "profile" of the disk appears on the MCA screen. See Fig. 2 for a sample profile. The points A, B...