Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Reexamination Certificate
1999-05-25
2003-12-02
Lee, Thomas D. (Department: 2622)
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
C358S474000, C382S274000
Reexamination Certificate
active
06657748
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an image reading apparatus, image reading method, and storage medium and, more particularly to, an image reading apparatus, image reading method, and storage medium, capable of reading an image, obtained by, e.g., an optical scanner, converting the image into electric image signals by an image sensor, digitizing the electric image signals by an analog-digital (A/D) converter, and transferring the digitized signals to an external device, and a user-friendly image reading apparatus, image reading method, and storage medium capable of obtaining image data of good quality by constantly performing optimum shading correction by reducing undesirable effects caused by, e.g., deterioration of a light source.
Conventionally, an image reading apparatus capable of transferring image data to a host computer is provided with a white shading correction board. Using the shading correction board, so called shading correction for correcting variation in various characteristics of optical sub-system and variation in output signals from respective photoelectric conversion elements of an image sensor, thereby eliminating reading irregularity (spots), is commonly performed. Shading correction data for each color component used in the shading correction is usually generated as data of a single line by operating acquired data of several lines.
Further, in a conventional image reading apparatus, an on-period of a light source, such as an LED, used for reading a standard white board for shading correction, and shading correction data obtained on the basis of the read data are transferred to a host computer in advance and, when reading an image, the on-period of the light source and the shading correction data used as a reference level, for instance, are loaded down from the host computer, then shading correction is performed, using the shading correction data, on image data obtained by reading an original image while turning on the light source for the on-period.
Further, in the conventional reading apparatus, various image processings, such as shading correction, are applied to electric signals generated by scanning the original image. The shading correction data is generated each time an original is read, or in response to a manual instruction by a user when the user determines on the basis of deterioration of quality of a read image that the shading correction is necessary.
An example of a conventional image reading apparatus is explained below.
FIG. 11
is a block diagram illustrating a brief configuration of an image reading apparatus, such as an image scanner. In the image reading apparatus, digital image data is generated by processing signals outputted by an image sensor
1041
and outputted to a host computer
1048
, such as a personal computer.
The image reading apparatus includes the image sensor
1041
which scans an original with light, receives reflected light from the original, and converts the light into analog electric signals, an analog circuit
1042
which processes the analog signals outputted from the image sensor
1041
, an analog-digital (A/D) converter
1043
for converting analog image signals outputted from the analog circuit
1042
into digital image signals, a digital processing circuit
1044
for applying predetermined digital signal processes to the digital image signals, RAM
1045
for storing the processed digital image data, a CPU
1046
for controlling the overall operation of the image scanner
1041
, and an interface unit
1047
for controlling an interface with an external device (host computer, in this case), as shown in FIG.
11
.
In the apparatus shown in
FIG. 11
, when a command for reading an original is inputted from the host computer
1048
, the CPU
1046
controls the image sensor
1041
to read a reference board in advance of reading an image area of the original, generates reference data, and stores the reference data in the RAM
1045
. Thereafter, the CPU
1046
performs predetermined calculation based on the reference data and generates shading correction data, and stores the data in the RAM
1045
. Then, the reading of the image area of the original is initiated as well as read image is corrected using the shading correction data.
In a case where the image reading apparatus does not generate shading correction data each time an original is read, a command for generating shading correction data is provided in a software installed on the host computer
1048
, and the user instructs to generate the shading correction data by operating the host computer
1048
when necessary.
However, in an image reading apparatus adopting a line sequential reading method, data of only one color component out of three color components, namely, red (R), green (G) and blue (B), is acquired by reading a single line (acquired data is called “shading data” hereinafter); accordingly, in order to obtain shading data of all the three color components, it is necessary to scan an identical line three times. In addition, since it is necessary to acquire shading data of n lines (n is a positive integer, 2 or greater) for each color component, memory having a capacity of storing data of (n+1) lines×3 color components, where “1” corresponds to data of calculation result, is needed for generating shading correction data. Further, in a case of sharing a memory area for storing acquired shading data of n lines and sequentially generating shading correction data of the respective colors, the required capacity of the memory for generating shading correction data is to store data of (n+3) lines, namely, n lines of data of a single color component and generated shading correction data of the respective three color components. In this case, a white shading board having an effective area width corresponding to 3×n lines is necessary, which requires a space for accommodating the board, and makes it difficult to reduce the size of an image sensing apparatus.
Further, there is a problem in which proper shading correction is not performed using shading data loaded down from the host computer when the quantity of light illuminating an original has been changed due to, e.g., deterioration of a light source.
Further, it is necessary to read a reference board or a white board and generate reference data, then perform predetermined calculation by a CPU using the reference data in order to generate shading correction data, and write the shading correction data in the RAM in advance of reading an image. Therefore, if the shading correction data is generated each time an image is read, it takes extra time for generating the shading correction data in addition to reading the original.
Especially, when reading a color image, it is necessary to generate image data of the respective R, G and B color components, therefore, for generating shading correction data for the respective R, G and B color components, it takes three times longer than time for generating shading correction data for a black-and-white image. Furthermore, when a high-density image sensor is used, since a large number of pixels are arranged in the sensor, it requires longer time to generate the shading correction data.
Accordingly, it is stressful for a user if shading correction data is generated each time an original is read since it takes a longer time for reading the original.
Meanwhile, in a case where a user instructs to generate shading correction data by operating a computer, the user must evaluate deterioration of image quality, which requires that the user have a skill of a certain level and perform extra work.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above situation, and has as its object to provide an image reading apparatus, an image reading method, and a storage medium capable of outputting image signals to which shading correction has been applied using a minimum memory area and a white shading correction board of a minimum width.
According to one aspect of the present invention, the foregoing object is
Amimoto Mitsuru
Fukawa Kimihiko
Okita Hisao
Sakai Takashi
Canon Kabushiki Kaisha
Lee Thomas D.
Morgan & Finnegan L.L.P.
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