Image analysis – Image sensing – Sensor control
Reexamination Certificate
2000-11-20
2001-10-16
Johnson, Timothy M. (Department: 2623)
Image analysis
Image sensing
Sensor control
C358S486000, C382S167000
Reexamination Certificate
active
06304683
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a technique for scanning originals with an image sensor, such as CCDs (charge-coupled devices).
2. Description of the Related Art
An image scanning apparatus generally illuminates an original with light and introduces light reflected from the original (or transmitted through the original) into a first-dimensional CCDs, in order to read image signals of the original from the first-dimensional CCDs. The respective elements of the first-dimensional CCDs do not have identical sensitivity characteristics. Even when light enters all the elements homogeneously, there is a scatter in the output level of the elements. Shading correction is a typical procedure to correct the scatter in the sensitivity characteristics of the respective elements of the one-dimensional CCDs. The process of shading correction scans a white reference plate (or a black reference plate) prior to the scan of the original, and generates coefficient data used for correcting the sensitivities of the respective elements of the one-dimensional CCDs, based on the output signals with respect to the reference plate from the one-dimensional CCDs. The process of shading correction corrects the output signals of an image obtained by scanning the original with the coefficient data.
It is here assumed that a plurality of originals are set on an original tray. The plurality of originals have different scanning resolutions and different widths. It is accordingly required to set a scanning angle of the one-dimensional CCDs for each original. The ‘scanning angle’ here represents an angle of a possible shooting range of the first-dimensional CCDs. The coefficient data used for correcting the sensitivities depend upon the scanning angle of the one-dimensional CCDs. The prior art technique accordingly carries out the shading correction for each of the plurality of originals set on the original tray, prior to the scan of the original.
As mentioned above, the prior technique requires the shading correction every time when the target of the scan is moved to a next original among the plurality of originals set on the original tray. This means that the process of scanning the white reference plate and updating the coefficient data used for correcting the sensitivities should be carried out for each original. This undesirably lengthens the total time required for scanning images.
SUMMARY OF THE INVENTION
The object of the present invention is thus to shorten the total time required for scanning images of a plurality of originals set on an original tray.
The above and the other related objects is realized by a first image scanning apparatus for optically scanning images of a plurality of originals set on an original tray, the first image scanning apparatus including: a light source which illuminates each of the original; a lens which condenses light from the each of original to condensed light; and a liner image sensor, arranged at a position of concentration of the condensed light, comprising a plurality of light-receiving elements arrayed in a primary scanning direction for converting light to electrical signals.
The first image scanning apparatus further includes:
a scanning range specifying unit which adjusts relative positions of the lens, the liner image sensor and the original tray so that a scanning range of the linear image sensor in the primary scanning direction includes at least two of the plurality of originals;
a color reference data generating unit which obtains an output signal of the linear image sensor for a preset color reference while the scanning range of the linear image sensor is fixed to what has been specified by the scanning range specifying unit, and generating color reference data for correcting sensitivity of each light-receiving element of the linear image sensor on the basis of the output signal;
a secondary scanning unit which moves the original tray relative to the linear image sensor in a secondary scanning direction while the scanning range of the linear image sensor is fixed to what has been specified by the scanning range specifying unit; and
an electrical signal correction unit which corrects an electrical signal, which is output from the linear image sensor as the original tray is moving in the secondary scanning direction, with the color reference data generated by the color reference data generating unit.
In the first image scanning apparatus of the present invention, the scanning range specifying unit adjusts the relative positions of the optical lens, the linear image sensor and original tray, so that a scanning range of the linear image sensor in the primary scanning direction includes at least two of the plurality of originals. While the scanning range of the linear image sensor is fixed to what has been specified by the scanning range specifying unit, the color reference data is generated by the color reference data generating unit, and the images of at least two originals are read by the linear image sensor as the original tray is moving in the secondary scanning direction. The electrical signal correction unit corrects the electrical signals output from the linear image sensor as the color reference data. Namely the same color reference data generated by the color reference data generating unit can be applied to correct the electrical signals representing the images of at least two originals.
This structure effectively reduces the generating cycles of the color reference data used for correcting the sensitivities of the linear image sensor to be less than the number of the originals, thereby shortening the total time required for scanning the plurality of originals set on the original tray.
In accordance with one preferable application, the secondary scanning unit successively scans at least two originals one by one in the secondary scanning direction while the scanning range of the linear image sensor is fixed to what has been specified by the scanning range specifying unit. In this application, the first image scanning apparatus further includes:
a data extraction unit which extracts image data of an original currently being scanned by the secondary scanning unit from the electrical signal corrected with the color reference data; and
a memory which stores the extracted image data.
In this preferable structure, the secondary scanning unit successively reads at least two originals one by one in the secondary scanning direction. The required capacity of the memory accordingly corresponds to the image data of one original. This structure reduces the required capacity of the memory for storing the image data.
In accordance with another preferable application, the first image scanning apparatus further includes a pre-scan unit which scans a whole image representing all the plurality of originals set on the original tray at a predetermined resolution. In this application, the scanning range specifying unit includes:
a computation unit which specifies an angle of view of the linear image sensor and a specific position of the linear image sensor in the primary scanning direction to attain the scanning range, on the basis of the whole image obtained by the pre-scan unit; and
an optical system shifting unit which adjusts the relative positions of the lens, the linear image sensor and the original tray in order to attain the angle of view and the specific position specified by the computation unit.
In the first image scanning apparatus of this structure, it is preferable that the computation unit includes:
a trimming unit which specifies an effective range of each of the original as a trimming area of each of the original, on the basis of the whole image obtained by the pre-scan unit; and
a unit which calculates an angle of view and the specific position of the linear image sensor from the trimming area of each of the original specified by the trimming unit.
In the first image scanning apparatus of the above preferable structure, the secondary scanning unit successively scans the at least two originals one by one
Kiyohara Satoru
Muraji Kunio
Dainippon Screen Mfg. Ltd.
Johnson Timothy M.
Ostrolenk Faber Gerb & Soffen, LLP
LandOfFree
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