Browse Prior Art Database

Scan Pitch Control for Raster Scanners

IP.com Disclosure Number: IPCOM000078486D
Original Publication Date: 1973-Jan-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Gilkinson, JL: AUTHOR

Abstract

This control system provides accurate spacing of vertical scans over a wide range of scan head speeds. The scheme allows real-time adjustment of the scanning pitch to provide width normalization of data being scanned.

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Scan Pitch Control for Raster Scanners

This control system provides accurate spacing of vertical scans over a wide range of scan head speeds. The scheme allows real-time adjustment of the scanning pitch to provide width normalization of data being scanned.

An input pulse train is generated from optical sensors located on moving scan head 1. The sensors detect high-resolution markings 2 on a stationary emitter bar 3, that is parallel to the scanner's traverse path. The scan pitch controller (SPC) contains logic circuitry, to provide a scanning pitch that is proportional to the pitch of the high-resolution emitter bar 3. Font and normalization criteria are also fed into SPC.

Fig. 2 shows the SPC which consists oi counters and a register. f(0) represents a basic clock frequency which is much higher than the emitter frequency, f(1) or the scanning frequency f(2). Each counter is incremented once per cycle of the previous counter. The output frequency of a counter is equal to the input frequency divided by its modulo. Counter 2 is driven at the frequency f(0)/M(1) and is used to measure the period of the emitter signal. The lead edge of an emitter pulse, causes the contents of the counter 2 ("N") to be placed in the register and then resets the counter to zero. The number N is, therefore, inversely proportional to the emitter frequency. Counter 3 is a variable-modulo counter which samples the data register once per cycle. Counter modulos M(1) and M(2) are determined b...