Incremental printing of symbolic information – Thermal marking apparatus or processes – Density control
Reexamination Certificate
1999-05-17
2001-12-11
Le, N. (Department: 2861)
Incremental printing of symbolic information
Thermal marking apparatus or processes
Density control
Reexamination Certificate
active
06330012
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image forming system, and more particularly to an image forming system which can form a plurality of identical images arranged in a row or rows.
2. Description of the Related Art
There has been known an image forming system such as a printer (e.g., a thermal printer, a stencil printer and the like) or a copier which reproduces or outputs an image, for instance, on a printing paper on the basis of an image signal read out from an original, for instance, by a CCD line sensor.
For example, in a stencil printer, an image on an original is read out from the original by an image read-out section, whereby an image signal representing the image is obtained. Then a stencil master material is perforated in an imagewise pattern on the basis of the image signal by an image writing section comprising a thermal head and a platen roller, thereby making a stencil master. The stencil master is wound around a printing drum and ink is transferred through the stencil master to printing papers which are supplied between the printing drum and a press roller pressed against the printing drum. In this manner, the image on the original is printed.
In such a stencil printer, it is sometimes necessary to print an image of an original of a small size (e.g., B6 size) a plurality of times on a larger size printing paper (e.g., of B4 size), for instance, so that four copies of the image are printed on the larger size printing paper side by side in two rows. Such function will be referred to as “contiguous multi-imaging”, and the image a plurality of copies of which are to be printed on a printing paper will be referred to as “the image to be multiplied”, hereinbelow. When performing contiguous multi-imaging, a line memory such as a RAM has been generally used in order to form a plurality of copies arranged side by side in the direction of the main scanning.
Specifically, as disclosed, for instance, in Japanese Utility Model Publication No. 1(1989)-45170, a plurality of duplicates of image data are made on the line memory by handling the image data as single-bit serial data (binary image data) and storing the same image data at a plurality of addresses by address control of the line memory, and the line memory is thus caused to store image data for contiguous multi-imaging. Accordingly a line memory which is of a single bit in data width is employed.
A thermal head which is employed as an output head in making a stencil master comprises a linear array of a plurality of heater elements each corresponding to one picture element. The heater elements are selectively energized according to image data while the thermal head is being moved relative to a stencil master material in the direction of sub-scanning (the direction substantially perpendicular to the direction in which the linear array of the heater elements extends) to make a stencil master by perforating the stencil master material in an imagewise pattern line by line on the basis of the image data. When the stencil master is made by use of such a thermal head, there has been a problem that heat energy gradually accumulates in each heater element as the stencil master making progresses. This becomes more serious as the stencil master making speed is increased since heat energy generated in the heater element when perforating along a certain line cannot be sufficiently dissipated before starting perforation along the next line. As a result, heat energy accumulates in each heater element according to its heat history and fluctuation in energy condition is generated among the heater elements, which results in deterioration in image quality. When the stencil master making speed is increased by dividing the heater elements of one thermal head into a plurality of blocks which can be driven separately from each other and driving the blocks in parallel, the aforesaid problem is somewhat alleviated. However as the stencil master making speed is further increased, the problem arises again.
There has been proposed “heat-history-based control” in order to overcome the aforesaid problem due to the heat history of each heater element. That is, in the heat-history-based control, heat history of each heater element and those around the heater element is stored in a line memory such as a RAM, and power to be applied to each heater element for perforation of a given line is controlled taking into account the heat history of the heater element and those around the heater element so that the heat energy in the heater elements is uniformed. The heat-history-based control becomes more essential to an image forming system using such a thermal head as the image forming speed increases. See, for instance, Japanese Unexamined Patent Publication Nos. 60(1985)-161163 and 2(1990)-8065.
There has been a demand for a stencil printer which can perform the contiguous multi-imaging at a high speed. In order to meet this demand, the stencil printer must be provided with both the contiguous multi-imaging function and the heat-history-based control function. Such a stencil printer may be realized by separately providing the stencil printer with both a memory for contiguous multi-imaging and a memory for heat-history-based control.
FIG. 13
is a block diagram showing the part for executing contiguous multi-imaging and heat-history-based control of a stencil printer system provided with both a memory for contiguous multi-imaging and a memory for heat-history-based control. In the heat-history-based control of this system, heat-history-based correction image data is made on the basis of the image data for a current line (the line to be formed next) and that for the preceding line and heat-history-based control is performed according to the heat-history-based correction image data. In this system, binary image data in the form of single-bit serial data is input into a data control means
80
for the contiguous multi-imaging. The image data input into the data control means
80
is stored in a RAM
82
at addresses designated by an address control means
84
. Normally the address control means
84
increments the address one by one and input image data is stored in the RAM
82
as single-bit data. When a contiguous multi-imaging is on, the image data for the image to be multiplied is stored in a plurality of addresses the number of which is designated by the address control means
84
according to the number of the copies to be formed in the contiguous multi-imaging mode (this number will be referred to as “the number of multiplication”, hereinbelow). In this case, though the identical image data is stored at different addresses, the image data is stored at each address as single-bit data.
A data control means
90
for heat-history-based control reads out data in sequence from the RAM
82
and stores the data in a RAM
92
which functions as a two-line memory. At this time, the single-bit data read out from the RAM
82
is divided by the number of blocks (four in this particular example) in the thermal head into four image data fractions which are contiguous in the direction in which the thermal head extends (the direction of the main scanning), and the image data fractions are recorded in the RAM
92
at different bits, whereby the single-bit data read out from the RAM
82
is stored in the RAM
92
as four-bit (equal to the number of blocks in the thermal head) data.
Then a heat-history-based correction image data making section
64
of an output control means
66
reads out the preceding line image data and the current line image data from the RAM
92
and makes heat-history-based correction image data. As shown in
FIG. 14
, the heat-history-based correction image data is obtained by taking a Boolean intersection of inverted preceding line image data and the current line image data. A data selecting section
67
of the output control means
66
inputs the heat-history-based correction image data made by the heat-history-based correction image data making section
64
into a TPH drive section
72
of a head dri
Feggins K.
Le N.
Nixon & Peabody LLP
Riso Kagaku Corporation
Studebaker Donald R.
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