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Alternating Drive/Sense Function for Electrodes in a Conductive Ink Sensor Head

IP.com Disclosure Number: IPCOM000040153D
Original Publication Date: 1987-Oct-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 3 page(s) / 94K

Publishing Venue

IBM

Related People

Campbell, AS: AUTHOR [+2]

Abstract

Reading of a pattern of conductive ink on a sheet of paper is obtained by a column of electrodes of a thermal printhead having electrodes alternately used as a driver or a sensor during sensing of single pels (print elements) so that each electrode can effectively function as a sensor rather than only half of the electrodes so functioning. Each of electrodes 1-9 (Fig. 1), for example, of a thermal printhead having forty electrodes arranged in a column is approximately 1/480" by 1/480" but each conductive dot or pel 10 printed on a sheet of paper is approximately 1/240" by 1/240". Each of the pels 10 is shown one-half shaded 11 and one-half blank 12 to illustrate the alternating status of drive and sense of one of the electrodes 1-9 when sensing that pel 10.

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Alternating Drive/Sense Function for Electrodes in a Conductive Ink Sensor Head

Reading of a pattern of conductive ink on a sheet of paper is obtained by a column of electrodes of a thermal printhead having electrodes alternately used as a driver or a sensor during sensing of single pels (print elements) so that each electrode can effectively function as a sensor rather than only half of the electrodes so functioning. Each of electrodes 1-9 (Fig. 1), for example, of a thermal printhead having forty electrodes arranged in a column is approximately 1/480" by 1/480" but each conductive dot or pel 10 printed on a sheet of paper is approximately 1/240" by 1/240". Each of the pels 10 is shown one-half shaded 11 and one-half blank 12 to illustrate the alternating status of drive and sense of one of the electrodes 1-9 when sensing that pel 10. When adjacent electrodes, such as the electrodes 1 and 2, alternately function as a sensor and driver at a high fre-

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quency during a scan so that each of the pels 10 scanned by the electrode 1 has the electrode 1 in a sense mode, as indicated at 11, and in a drive mode, as indicated at 12, with the electrode 1 in a sense mode when the electrode 2 is in a drive mode and vice versa, then the conductive pels 10 will be sensed more reliably during a scan than if the electrode 1 is always in the sense mode and the electrode 2 is always in the drive mode, for example. The pattern shown in Fig. 1 illustrates limitations in the pattern since it has the pels 10 which will not be sensed. As will be apparent, this can be eliminated by providing in each continuous pattern a continuous line of the pels 10 under an odd electrode and under an even electrode, the continuous line under the odd electrode extending as wide as all the pels 10 to be sensed by an even electrode and the continuous line under the even electrode extending as wide as all the pels 10 to be sensed by an odd electrode. The first conductive pel 10a scanned by the electrode 1 cannot be sensed with each of the electrodes 1-9 operating alternately in the sense and drive modes over each of the pels 10.

This is because the only other electrode over one of the conductive pels 10 at this time is the electrode 5. The electrode 5 is always in the same mode as the electrode 1 since alternate electrodes have opposite modes. To sense one of the pels 10, it is not necessary for adjacent electrodes such as the electrodes 1 and 2, for example, to be over the pels 10. It is only necessary that an electrical path exist from one of the even-numbered electrodes over one of the pels 10 at the same time that one of the odd-numbered electrodes is over another of the pels 10 connected to the one pel 10 by the overall pattern of the pels 10. For example, the last of the pels 10 scanned by the electrode 2, pel 10b, is sensed even though the adjacent electrodes 1 and 3 are not over one o...