Browse Prior Art Database

Image Rotator for Page Printer

IP.com Disclosure Number: IPCOM000101489D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 4 page(s) / 140K

Publishing Venue

IBM

Related People

Howell, JH: AUTHOR [+2]

Abstract

Disclosed is an image rotator which permits feeding paper into a page printer sideways, wide side first, thus increasing printer throughput.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Image Rotator for Page Printer

       Disclosed is an image rotator which permits feeding paper
into a page printer sideways, wide side first, thus increasing
printer throughput.

      In a known page printer a representation of the page to be
printed, a bit map, is developed in memory with "one" representing
black and "zero" representing white image pixels.  The bit map is
read, serialized by bit, to a laser thus transferring the image to
the surface of a drum. The drum is inked and the image is transferred
to the paper as it passes under the drum.

      Fig. 1 shows the bit map memory addressing scheme by 8-bit
bytes.  The top left corner of the map is address zero. For normal
printing page data, where the top of the page feeds under the drum
first, the bit map is serialized, and presented to the print engine,
moving left to right, top to bottom.  Raster pitch (RP) is the number
of addressable bytes representing one horizontal scan line.  In this
known printer the controller reads successive 32-bit words (4
sequential bytes) from bit map memory to a serializer. The bits are
then clocked out of the serializer shift register to the laser so as
to apply the image to the paper the same way it is written in the
bit map.  Each 32-bit word is accessed by addressing its 0 bit, the
first bit of the first byte.

      It is apparent that to properly orient the image on paper fed
sideways, where the top of the page is to the right and the left edge
of the page feeds under the drum first, it is necessary to serialize
the bit map moving bottom to top, left to right.  Fig. 2 shows the
resulting page rotated serialization.  It is seen that because of the
bit map architecture, each bit in the top row is the 0 bit of a
32-bit 4-byte map word which is now oriented vertically with respect
to the page. Therefore, in scanning the top row each access reads out
a 32- bit word (bytes 1, 2, 3, and 4) of which only the 0
bit is significant and to be serialized.  It is seen that the next
lower row of bits are the 1 bits of the same 32-bit map words, and
that they may be selected and serialized in a repeated scan of the
first row. In each succeeding scan of the first row the next bit is
serialized.  After serializing the words represented by bytes 1, 2,
3, and 4, serialization continues by accessing words represented by
bytes 5, 6, 7, and 8, and then continues in the same manner with each
succeeding four-byte swath.  It is seen that in this page rotated
serialization, each 32-bit word must be accessed 32 times in order to
serialize all 32-bits.  It is further seen that in scanning in this
manner the addresses of sequential bits within the bit map are
effectively one raster pitch apart.  It is apparent that to operate
in this mode would result in seriously degrading the efficiency of
the serializer.

      Referring to Fig. 3, it is...