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Compensation of a Multiplexed Array Recording Head for Magnetic Printing

IP.com Disclosure Number: IPCOM000059889D
Original Publication Date: 1986-Feb-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 3 page(s) / 63K

Publishing Venue

IBM

Related People

Kahwaty, VN: AUTHOR

Abstract

Array recording heads used in high speed magnetic printing require a stationary recording head with the number of recording elements equal to the product of the word and bit line drivers. Magnetic printing systems using post head elements as the pel (picture element) recording device have been described in the literature [1,2]. The bitlines are generally the high duty cycle lines in the array multiplexing operation, for example, a magnetic recording head with 4096 elements will require a minimum of 64-word and 64-bit drivers to multiplex address any head element in the array. To address all the heads in the array, for one writing cycle, each word driver is addressed once while the bit drivers are addressed 64 times (equal to the number of word drivers).

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Compensation of a Multiplexed Array Recording Head for Magnetic Printing

Array recording heads used in high speed magnetic printing require a stationary recording head with the number of recording elements equal to the product of the word and bit line drivers. Magnetic printing systems using post head elements as the pel (picture element) recording device have been described in the literature [1,2]. The bitlines are generally the high duty cycle lines in the array multiplexing operation, for example, a magnetic recording head with 4096 elements will require a minimum of 64-word and 64-bit drivers to multiplex address any head element in the array. To address all the heads in the array, for one writing cycle, each word driver is addressed once while the bit drivers are addressed 64 times (equal to the number of word drivers). Hence, the bit drivers contain the data to be printed while the word drivers physically locate the data in the head array. A simple array multiplexed magnetic print head is shown in Fig. 1; the bit line wires are B1 through B8, and the word line wires are W1 through W. The head is composed of eight by M recording elements designated E11 through E8M. Considerable variability between recorded pels from individual head elements has been noted. It has also been found that overall pel intensity can be controlled over some range by adjusting driving currents; however, pel-to-el variability is still present. The cause of this variability is attributed to variations in head element magnetic parameters and driver circuit availability. A method has been devised to electrically compensate each head element in the array to produce the same spot intensity. In the case of magnetic printing, this compensation can be accomplished automatically with a method to be described. Since the magnetic print head is array multiplexed, by adding correction currents to the bit lines when write data is present, it is possible to compensate each recording head element individually. A circuit method for driving bit line wires is shown in Fig. 2, where one of eight bit drivers is shown. The bidirectional bit driver 1 is composed of two identical driver transistors 2 and 3 which are wound with different winding directions through a toroid 4 and share a current- limiting resistor 5. The bit line wire 6 interconnects E11 through E1M head elements and is wound on the toroid 4. Therefore, the bit wire is essentially the secondary of a transformer, with the primary side driven by the bit drivers. If we assume a lossless transformer, the bit wire current will be the algebraic sum of the primary currents. Hence, correction currents can be added by the addition o...