Image analysis – Image transformation or preprocessing – Changing the image coordinates
Reexamination Certificate
1998-09-22
2001-09-18
Lee, Thomas D. (Department: 2724)
Image analysis
Image transformation or preprocessing
Changing the image coordinates
C358S451000, C358S474000
Reexamination Certificate
active
06292594
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an image reading device for reading image by scanning a document, an image forming apparatus such as a digital copying machine which forms an image by using the image reading apparatus, and an image forming method.
Conventionally, the change of the image magnification rate in the sub-scanning direction in a digital copying machine (DPPC) is performed by changing a scanning speed of a scanner for scanning a document in accordance with the magnification rate. The scanning speed of the scanner is determined by variably controlling the rotation number of a motor for driving the scanner. Accordingly, in changing the magnification rate in the sub-scanning direction, the number of effective data in the main scanning direction is determined by variably controlling the rotation number of the motor within the available magnification range defined in the specification of the machine.
According to the conventional method as mentioned above, the scanner must be controlled to change the scanning speed every time when the magnification rate is desired to be changed in order to obtain the set magnification rate. The scanner is controlled by changing the rotation number of the motor for driving the scanner in accordance with the desired magnification rate.
In a middle or low speed DPPC machine which is not required so high speed scanning operation (i.e., in a machine the scanning speed of the scanner of which is relatively low when the scanning speed is set at the highest level at which the image reduction rate is largest) within a variable range of the rotation number of the motor (i.e., within a variable range of the scanning speed of the scanner), the scanning speed of the scanner is reasonable in mechanical point of view with respect to the driving specification of the motor.
However, in a high-speed machine, the operation speed of the scanner is so high that some functional problems will occur. For example, due to the limitation generated by the acceleration condition of a stepping motor which drives a scanner, a necessary run-up distance of the scanner cannot be secured in the scanning width in the sub-scanning direction. In addition, the vibration of a carriage will be generated by the high-speed scanning operation, thereby the image obtained by the scanning will be distorted. According to the conventional method, the above-mentioned problems will be made so critical.
BRIEF SUMMARY OF THE INVENTION
The object of the present invention is to provide an image reading apparatus capable of suppressing or preventing the problems generated due to the high-speed operation of a scanner, and an image forming apparatus and an image forming method.
The above-mentioned object of the present invention is attained by an image reading apparatus comprising scanning means for scanning a document by irradiating the document with a light beam, first control means for controlling a scanning speed of the scanning means at a constant level, reading means for reading reflected light from the document scanned by the scanning means by receiving the light and photoelectrically converting the reflected light into an electric charge signal corresponding to an image on the document so as to accumulate the electric charge signal, and setting means for setting a magnification rate of the image read by the reading means, second control means for controlling processing of the electric charge signal photoelectrically converted and accumulated in the reading means with a cyclic period determined in accordance with the magnification rate set by the setting means.
The above-mentioned object of the present invention is attained by an image reading apparatus comprising setting means for setting a magnification rate for magnification rate change operation such as reduction, non-reduction/magnification, and magnification, scanning means for scanning a document by irradiating the document with a light beam, first control means for controlling a scanning speed of the scanning means at a constant level, photoelectric conversion means for receiving reflected light from the document scanned by the scanning means, and for photoelectrically converting the reflected light into an electric charge signal to accumulate it, second control means for variably controlling a period of time during which the reflected light converted into the electric charge signal is accumulated in a photosensing section of the photoelectric conversion means in accordance with the magnification rate set by the setting means, image processing means for processing image on the basis of the electric charge signal accumulated in the photoelectric conversion means and processed during the period of the time controlled by the second control means, image forming means for forming image on an image forming medium on the basis of image data processed by the image processing means.
The above-mentioned object of the present invention is attained by an image forming method of forming image on an image forming medium by using setting means for setting a magnification rate for magnification rate change operation such as reduction, non-reduction/magnification, and magnification; scanning means for scanning a document by irradiating the document with a light beam; and photoelectric conversion means for receiving reflected light from the document scanned by the scanning means and for photoelectrically converting the reflected light into an electric charge signal to accumulate it, wherein the scanning speed of the scanning means is switched to be set at a constant level or variable in accordance with the magnification rate set by the setting means, when the scanning speed of the scanning means is set at the constant level by the switching means, the scanning speed of the scanning means is controlled at the constant level irrelevant to the magnification rate set by the setting means, and when the scanning speed of the scanning means is set variable, the scanning speed of the scanning means is controlled to be variable in accordance with the magnification rate set by the setting means, when the scanning speed of the scanning means is set at the constant level, a period of time during which the reflected light converted into the electric charge signal is accumulated in a photosensing section of the photoelectric conversion means is variably controlled in accordance with the magnification rate, and when the scanning speed of the scanning means is set variable, the period of time during which the reflected light converted into the electric charge signal is accumulated in a photosensing section of the photoelectric conversion means is set at a constant value, image processing is executed during one of the variably controlled period of time and the constant period of time on the basis of the electric charge signal accumulated in the photoelectric conversion means, and an image is formed on the image forming medium on the basis of the processed image data.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
REFERENCES:
patent: 5856879 (1999-01-01), Suzuki et al.
patent: 6032864 (2000-03-01), Hamasuna
patent: 04-233874 A (1992-08-01), None
patent: 7-336506 (1995-12-01), None
Foley & Lardner
Kabushiki Kaisha Toshiba
Lee Thomas D.
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