Facsimile and static presentation processing – Static presentation processing – Memory
Reexamination Certificate
1999-09-22
2001-02-13
Coles, Edward L. (Department: 2722)
Facsimile and static presentation processing
Static presentation processing
Memory
C358S001150, C358S451000, C358S451000, C358S451000, C358S500000
Reexamination Certificate
active
06188489
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an image forming apparatus such as a digital copying machine for creating an image signal by reading an image of a document or the like by use of a scanner, for example, and then forming an image on paper according to the image signal by use of a laser printer.
Generally, in a digital copying machine or the like dealing with image information, an image signal read by use of reading means such as a scanner is converted into a proper form, for example, multi-density form depending on the service objective. At this time, if the entire portion or part of the read image is too light or too dark, an input image is subjected to a process for adjusting the density characteristic and then output by use of a laser printer. Conventionally, the adjustment of the density characteristic is generally made by use of a conversion table in which the relation between the density of the input image signal and the corresponding density of the output image signal is set.
The adjustment method using the conversion table necessitates a memory of a large capacity as a memory for storing conversion tables as the number of types of the conversion tables increases and the number of multi-density levels of the image increases. If the multi-density data is expressed by eight bits, it is necessary to store 8-bit values obtained after conversion and used for the adjustment for each of 256 densities which can be represented by eight bits in order to adjust the density characteristic of the image signal.
Therefore, one conversion table necessitates a capacity of 8 bits×256, and if a plurality of conversion tables are used, a memory of extremely large storage capacity is required. For example, when the density adjustment is made by use of a manual density setting button for each mode such as a photographic mode or character mode, a memory of extremely large storage capacity is required.
Further, a method using a circuit for deriving values to be stored into the conversion table on the real time basis instead of previously storing the conversion tables in the memory is provided. When the linear conversion is made, a table value deriving circuit used for this purpose can be made relatively small in scale and simple in construction, but if the conversion is made according to a complicated curved line or a curved line which cannot be expressed by an equation, a circuit complicated in construction and large in scale is necessary or the conversion cannot be attained by use of a circuit.
Further, generally, values actually converted by use of the conversion table are not values which are linearly changed before and after the conversion, and they vary along a curved line expressed by a complicated equation or cannot be expressed by an equation in most cases.
In addition, when the density adjustment is made by use of values stored in the conversion table, the content of the adjustment is limited to a range defined by the values in the conversion table and the degree of freedom of the density adjustment becomes low.
An object of this invention is to provide an image forming apparatus in which the storage capacity of a memory for storing density adjustment tables can be reduced and the density adjustment can be performed with a relatively high degree of freedom.
BRIEF SUMMARY OF THE INVENTION
An image forming apparatus of this invention comprises generation means for generating an input image signal corresponding to the density of an image; setting means for setting the density of an output image corresponding to the input image signal generated by the generation means; storage means for storing at least two sets of first density characteristic adjusting data each indicating the correspondence relation between the input image signal and the output image signal for image formation according to the density of the output image; creation means for creating second density characteristic adjusting data corresponding to the density of the output image set by the setting means by use of the two sets of first density characteristic adjusting data stored in the storage means; conversion means for converting the input image signal generated by the generation means into an output image signal by use of the second density characteristic adjusting data created by the creation means; and image forming means for forming an image on an image recording medium based on the output image signal converted by the conversion means.
An image forming apparatus of this invention comprises reading means for reading a document to generate an input image signal; setting means for setting the density of an output image corresponding to the input image signal generated by the reading means; storage means for storing three sets of first density characteristic adjusting data of dark reference, standard and light reference corresponding to the output image density and each indicating the correspondence relation between the input image signal and the output image signal for image formation; creation means for creating second density characteristic adjusting data corresponding to the density set by the setting means by use of two sets of first density characteristic adjusting data among the three sets of first density characteristic adjusting data of dark reference, standard and light reference stored in the storage means; conversion means for converting the input image signal generated by the reading means into an output image signal based on the second density characteristic adjusting data created by the creation means; and image forming means for forming an image corresponding to the output image signal converted by the conversion means on an image recording medium.
An image forming method of this invention comprises the steps of: generating an input image signal corresponding to the density of an image; setting the density of an output image corresponding to the input image signal; storing at least two sets of first density characteristic adjusting data each indicating the correspondence relation between the input image signal and the output image signal for image formation according to the density of the output image; creating second density characteristic adjusting data corresponding to the density of the output image by use of the two sets of first density characteristic adjusting data; converting the input image signal into an output image signal by use of the second density characteristic adjusting data; and forming an image on an image recording medium based on the output image signal.
An image forming method of this invention comprises the steps of: designating, in an adjusting mode, one of two sets of density characteristic adjusting data stored in a storing means for representing the correspondence relation between the density of an input image signal and the density of an output image signal for image formation; modifying the contents of the designated density characteristic adjusting data into desired data in the adjusting mode; converting the input image signal into the output image signal in accordance with the modified density characteristic adjusting data and the other of the two sets of density characteristic adjusting data in an ordinary mode; and forming an image in accordance with the converted output image signal.
An image forming method of this invention comprises the steps of: designating, in an adjusting mode, one of first printing mode and second printing mode and one of two sets of density characteristic adjusting data stored in a storing means corresponding to the first printing mode and the second printing mode, respectively, and representing the correspondence relation between the density of the input image signal and the density of an output image signal for image formation; modifying, in the adjusting mode, the contents of the designated density characteristic adjusting data into desired data; converting the input image signal into the output image signal in accordance with the density characteristic adjusting data corresponding to one printing mode and the other o
Coles Edward L.
Foley & Lardner
Kabushiki Kaisha Toshiba
Lamb Twyler
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