Facsimile and static presentation processing – Natural color facsimile – Scanning
Reexamination Certificate
1999-08-03
2003-01-28
Lee, Cheukfan (Department: 2722)
Facsimile and static presentation processing
Natural color facsimile
Scanning
C358S505000, C358S524000, C358S513000
Reexamination Certificate
active
06512605
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of The Invention
The present invention relates to an image reading apparatus and image reading method. More specifically, this invention concerns an image reading apparatus, for example, an image scanner having a plurality of sensor lines disposed in parallel at a specific interval or one stripe-type sensor line and the image reading method.
2. Description of The Prior Art
A known type of image reading apparatus such as an image scanner has three sensor lines disposed at a specific interval for three kinds of colors—red, green and blue. The method of simultaneously reading the color data covered under the three sensor lines is called the three line simultaneous reading technique.
FIG.
2
(
a
) is a conceptual presentation of the arrangements of the image sensor array of the three line simultaneous reading type. The sensor line to read red data is made up of a plurality of R sensor elements; the sensor line to read green data, of a plurality of G sensor elements; and the sensor line to read blue data, of a plurality of B elements.
It is understood that the main scanning direction corresponds to the direction in which the sensor elements of a kind are arranged to form a sensor line and the sub-scanning direction to the direction in which the image sensor array is moved for scanning.
Shown in
FIG. 16
is a system diagram of the prior art apparatus for reading color images by scanning the document with such image sensor arrays.
To be more specific, three color data picked up by an image sensor array
100
are read by line reading means
102
. The color data thus read are not uniform in output level among the sensor elements because of ununiformity in the amount of light from the light source, sensor element sensitivity and the like even when the document has an uniform shade, such as a sheet of black, white paper. This output data difference in output level among the sensor elements is corrected by shading correction means
105
, and the color data read is accumulated in a color data delay buffer
1600
. This color data delay buffer
1600
holds color data as they are inputted until after the other color data for one picture element are inputted. When all the three color data for one picture element or the same position on the document are ready, those data are mapped at a position on an image memory
110
by same picture element data mapping means
1601
.
The line reading means
102
is made up of three amplifiers
103
a,
103
b,
103
c
that amplify the respective color data picked up by the image sensor array
100
and an analog to digital (A/D) converter circuit
104
for converting the analog values of those amplifiers to digital values.
The prior art image reading apparatus thus configured reads an image the following way:
First, the image sensor array
100
made up of red, green and blue sensor lines, each having sensor elements lined up, read color data simultaneously. The respective color data read are referred to shading correction means
105
through the amplifiers
103
and A/D converter circuit
104
. The shading correction means
105
then subjects data of each color to shading correction. The color data thus obtained are mapped into the image memory
110
for display on CRT or the like.
Now, the mapping of color data into the image memory space will be explained.
Let it be supposed that the color data of a document at a point given by coordinates (X, Y) are to be read using an image sensor array in which red, green and blue sensor lines are disposed from the starting point in the sub-scanning direction in that order as shown in FIG.
2
(
a
).
First, a specific B sensor element, a constituent in the sensor line for blue, reads a blue data C-B as shown in FIG.
3
(
a
). This blue data C-B is then stored at the read color data delay buffer
1600
as shown in FIG.
16
.
In the next step, as a specific G sensor element, a constituent in the sensor line for green, gets to the position given by the same coordinates (X, Y) on the document, the sensor element reads the green data C-G. This C-G is also stored at the read color data delay buffer
1600
.
When a specific R sensor element, a constituent in the sensor line for red, reaches the same position given by coordinates (X, Y) on the document, the red data C-R is read in and then mapped by the same picture element mapping means
1601
into the image memory
110
at the identical coordinates along with the blue data C-B and the green data C-G that have been stored by the color data delay buffer
1600
.
As set forth above, the respective color data from a specific position on the document are held in the color data delay buffer
1600
until all three color data for that position are read. Then the three color data are simultaneously brought into the same position in the image data memory space.
There are also other types of apparatuses for inputting images by the image scanner. They include:
(1) Light source switching type which uses a light source having the spectral characteristics of the primary colors for color images and one image sensor array for black and white. The light source is switched on for three primary colors one after another to separate the image data on the color document into three primary color data.
(2) Stripe image sensor array type in which a three-color stripe filter is pasted over the light intake face of the sensor unit. In this type, a set of separated color data is simultaneously read from the start in the main scanning direction using an image sensor array in which sensor elements to detect red, green and blue are disposed in a stripe. The image reading apparatus using an image sensor array of the stripe type is configured as in FIG.
17
. The principle is disclosed in Japanese patent application laid open unexamined under No. 1-237619.
The image sensor array
1400
of the stripe type is constituted as shown in FIG.
2
(
b
). Following this image sensor array
1400
, second line reading means
1401
reads red, green and blue data almost simultaneously. And the green scanned position detection means
1700
detects all the scanned positions of the green data on the line.
Then, a red element and a blue element placed on the two sides of each green element read red and blue data respectively. And those red and blue data as well as the green data as a set are mapped on the image memory
110
at the coordinates for the picture element for the green data as if the red and blue data both shared the same picture element position with the green data.
With the image sensor array of the stripe type as in (2), a set of neighboring red, green and blue color data, which are actually read at different positions in the main scanning direction are mapped into the image memory as color data at one and the same position, to input an image.
It has been pointed out that the image reading apparatus of the three-line simultaneous reading type has the following problems:
The time required to obtain three color data at the same position on the document increases with these distances—the distance between the G sensor line and the R sensor line which shall be given as d-GR picture elements distance and the distance between the G sensor line and the B sensor line as d-GB picture elements distance. To keep with an increase in distance, the read color data delay buffer
1600
would have to be increased in size. Even if the distances between the sensor lines are fixed, the buffer
1600
would have to be larger in size for a larger resolution of the image sensor array.
Another point is that to make it easy for the user to input an image, it is desirable that the scanning direction is not restricted. For the scanning image sensor array is not always moved in one direction but possible to be changed. It is possible that the unit is moved back. In the mapping method as in
FIG. 3
, the color data to be held in the read color data delay buffer
1600
has to be changed and adapted to the scanning direction in such a case, which makes the image inputting circuit very complicated.
With the stripe
Kojima Akio
Kuwahara Yasuhiro
Watanabe Tatsumi
Lee Cheukfan
McDermott & Will & Emery
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