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Browse Prior Art Database

Nonius Based Digital Position Sensor

IP.com Disclosure Number: IPCOM000052555D
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 3 page(s) / 51K

Publishing Venue

IBM

Related People

Goetze, V: AUTHOR [+3]

Abstract

For different applications, for example, in sensors of all types, highposition signals are required. These signals are generated by reference grid of relatively high precision and one or several photoscan cells.

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Nonius Based Digital Position Sensor

For different applications, for example, in sensors of all types, highposition signals are required. These signals are generated by reference grid of relatively high precision and one or several photoscan cells.

Such an arrangement consisting of one or several individual cells operated in parallel, which is subsequently referred to as scan cell 2, scans reference grid 1 in the direction of arrow 3. The size or length L of scan cell 2 is chosen to differ respectively from the spacing of the light fields 4 and the dark fields 5 and the reflecting and non-reflecting line areas of reference grid 1. Length L of the scan cell is, for example, one pel (picture element). At a desired resolution of 600 pel/inch this corresponds to a length of 42.3 Mum. In contrast to this, the spacing of the light fields 4 and the dark fields 5 of reference grid 1 is chosen to be, for example, 1.25 pel Delta 63.5 Mum, so that the periodicity of reference grid 1 is unequal to the scanning periodicity.

Scanning is effected in the rhythm of the scan pulses specified on arrow 3 in lines D, D' and E, F. Thus, reference grid 1 is scanned first, for example, when scan cell 2 in the position shown in line C is exactly between points 0 and 1 of arrow 3 in line C. In this first scan, cell 2 detects in the manner of instantaneous exposure the percentage of light reflected from areas 4 and 5. In actual fact, scan cell 2 is positioned above reference grid 1, a section of which is shown in line B, where scan cell 2 is positioned beside reference grid 1 for clarity's sake. In scan 2, line E, scan cell 2 is between positions 1 and 2 of arrow 3 in line D, if the relative speed between reference grid 1 and cell 2 has remained unchanged. This continues analogously for the further scan pulses 3, 4, 5, etc.

The output signals of scan cell 2 are fed to a threshold logic. Without position errors, i.e., ideal scan times, shown in lines B and C, an ideal bit pattern is obtained after evaluation. This is determined by the periodicity of reference grid 1 and the scanning times as well as the line width and the size of the scan cell. The length of the bit pattern is given by the nonius period m. The scanning period corresponds to size L of the scan cell. The periodicity of reference grid 1 is denoted by p, so that the nonius period is obtained from the relation m . L = n . p, where m and n are integers which are as small as possible.

In the case of the...