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Laser Printing of Subscripts and Superscripts

IP.com Disclosure Number: IPCOM000051318D
Original Publication Date: 1981-Jan-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 3 page(s) / 34K

Publishing Venue

IBM

Related People

Knudson, RL: AUTHOR

Abstract

Printing by a laser scan on an electrostatic photoconductor erases the area that is not to be printed. As a result, once an area has been scanned, images (dark areas) cannot be replaced on the discharged surface. When scan-generating documents vertically from the top down, a super script, encountered on a line after the space above it has been erased, cannot be printed.

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Laser Printing of Subscripts and Superscripts

Printing by a laser scan on an electrostatic photoconductor erases the area that is not to be printed. As a result, once an area has been scanned, images (dark areas) cannot be replaced on the discharged surface. When scan- generating documents vertically from the top down, a super script, encountered on a line after the space above it has been erased, cannot be printed.

This is not a problem where sufficient memory space is available to format an entire page before starting to print the page.

As the source characters are received by line (horizontally), the partial index-coded characters can be arranged so that superscripts appear to be subscripts from the line above. Subscripts present no problem because they are generated in the non-scanned area on a lower line.

Where there is only enough memory space to process one line at a time, the following scheme is a solution to the problem and provides for multiple levels of indexing.

Each text line is scanned and, if it contains multiple character levels, the line is segmented into chains of text segments corresponding to each level. Each occurrence of a partial index code represents a change in level. When the scan is finished, the range of levels is completely defined as are the contents of the line.

Two tables - a line table and a level pointer table - are used to effect the chaining of line segments. The level pointer table contains as many entries as there are levels per line. Each entry in the level pointer table represents the sequence number in which the corresponding level was encountered. This will be clarified by an example. For subscripts and superscripts, i.e., half-indexed forward and half-indexed reverse characters, only three levels are required. For mathematical formulae, tensor notation, and the like, more than three levels are required. For example, an exponent may be itself raised to a power or be represented by a subscripted or superscripted variable.

The line table essentially contains two entries per line character. In addition to the character itself, a tag entry is used to point to the next table entry having the same level as the present entry.

It is also necessary to keep track of the escapement information for a line to be able to determine the relative position of each segment in the line. This will be assume...