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Automatic Skew Compensation for Scanning Device

IP.com Disclosure Number: IPCOM000039503D
Original Publication Date: 1987-Jun-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 3 page(s) / 43K

Publishing Venue

IBM

Related People

Quinn, PA.: AUTHOR

Abstract

There is automatic compensation for paper misalignment in a printer or typewriter for the purpose of reading information from the paper with a scanning device, which is a forty electrode printhead. (Image Omitted) When a paper is placed in a typewriter or printer for the purpose of scanning information printed on the paper, registration of the paper with a scanning head, which is a forty electrode printhead having the electrodes arranged in a vertical column, becomes critical. If the paper is misaligned, errors in reading the printed information can occur. The printed information on the paper consists of eight bits with each of the seven character bits being five electrodes high and three electrodes wide.

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Automatic Skew Compensation for Scanning Device

There is automatic compensation for paper misalignment in a printer or typewriter for the purpose of reading information from the paper with a scanning device, which is a forty electrode printhead.

(Image Omitted)

When a paper is placed in a typewriter or printer for the purpose of scanning information printed on the paper, registration of the paper with a scanning head, which is a forty electrode printhead having the electrodes arranged in a vertical column, becomes critical. If the paper is misaligned, errors in reading the printed information can occur. The printed information on the paper consists of eight bits with each of the seven character bits being five electrodes high and three electrodes wide. The most significant bit, which is the eighth bit, functions as the alignment bit and is three electrodes high and three electrodes wide. Since most typewriters and printers use only seven bits for ASCII code, the eighth bit is free. An additional bit would be required for an eight-bit system, and there would have to be either more than forty electrodes in the printhead that is scanning the printed information or the height of each character bit would have to be reduced. As shown in the flowchart of Fig. 1, there is an automatic insert of the paper to be read with less than its normal automatic insert by N steps. Thus, the paper will not be at its uppermost position. Accordingly, the paper will be advanced upwardly one step until both an A signal, which is at electrode 2 (Fig. 2) of the printhead used as a sense line, and a B signal, which is at electrode 4 of the printhead used as a sense line, are both up with an electrode 3 of the printhead functioning as a driver line for the two sense lines. When this occurs, the paper will be in its uppermost position. Then, the paper is scanned as the carrier moves to the right. At any time that both the A and B signals are not present, the paper is moved either up one step if the A signal is not present or down one step if the B signal is not present. This relationship of the signals to the electrodes is shown in Fig. 2 wherein the alignment bit has an inked surface 10, when the paper is properly aligned, passing beneath the electrodes 2, 3, and 4 of the printhead during movement of the carrier. The circuit of Fig. 3 is employed to determine whether the paper is properly aligned. The A signal is sensed on a line 11 and supplied through an inverter 12 to a latch 13, which is a flip flop. The latch 13 has a low on its output line 14 and a high on its output line 15 when it is in its initia...