Facsimile and static presentation processing – Static presentation processing – Attribute control
Reexamination Certificate
1998-11-24
2001-09-18
Lee, Thomas D. (Department: 2624)
Facsimile and static presentation processing
Static presentation processing
Attribute control
C358S406000
Reexamination Certificate
active
06292269
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for image reading, and more particularly to a method and apparatus for image reading that detects foreign particles which disturb an image reading operation.
2. Discussion of the Background
Many image reading apparatuses perform various operations for adjusting an image signal from an image sensor before starting the image reading operation. For such an adjusting operation, the image reading apparatus is generally provided with a reference white plate for an image sensor to read a reference white image. Based on the reference white image data for one main scanning length obtained by reading the reference white plate, the image reading apparatus adjusts gains of image signal in order to justify the level of the image signal from the image sensor, or performs a shading correction to correct for signal distortion due to inaccurate optical mechanisms employed therein or variations in optoelectronic conversion components such as a CCD (charge-coupled device), and so forth.
Also, the image reading apparatus is provided with a reference black plate for an image sensor to read a reference black image. Based on the reference black image data for one main scanning length obtained by reading the reference black plate, the image reading apparatus reduces an offset which is previously included in an image signal from the image sensor.
To perform the above-described adjustment and correction, the image reading apparatus is required to read the reference white and reference black plates in an accurate manner. However, even if the image reading apparatus reads the reference white and reference black plates, the reading accuracy may be disturbed by a foreign particle such as dust or the like which is put on the reference white and reference black plates.
More specifically, if a dust particle which is less white is put on the reference white image of the reference white plate, the level of the reference white image reading at the location of the foreign particle may erroneously be decreased. If a dust particle which is less black is put on the reference black image of the reference black plate, the level of the reference black image reading at the location of the foreign particle may erroneously be increased. The image reading apparatus will adjust the image signal based on such an erroneous reference white/black image data. When the image reading apparatus is connected to a printer, for example, the image data may be recorded on a recording sheet with an erroneous black line or the like.
Various solutions for the above-described problem have been introduced. For example, Japanese Patent Publication No. 60-251768(1985) describes a technique in which the image sensor reads a number of times reference white and reference black images in order to reduce an adverse influence to the reference white and reference black image signals by the foreign particle. However, this technique fails in speed, requiring a relatively long time period for completing the adjustment. In fact, causes of the erroneous image data may not be only the foreign particles put on the reference white/black image plate but also those on the interior of the image sensor. The former can be recovered by removing the foreign particles but the latter may need an exchange of the image sensor, for example.
Typically, these problems caused by the inner or outer foreign particles are found only after outputting the image data in a visual form such as a printout form. Yet, an abnormal print generally needs to be analyzed as to what the cause is. The foreign particle may be only one of the causes.
Therefore, at present, there is no image reading apparatus which is capable of detecting a foreign particle such as dust or the like which is put on a reference white/black plate or an image sensor, which disturbs an image reading operation.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a novel image reading apparatus which is capable of detecting foreign particles such as dust or the like that may disturb an image reading operation, in an efficient manner and with a simple structure.
To achieve the above-mentioned object, one example of image reading apparatus according to the present invention includes a reference image plate, an image reading device, a peak value detector, a first memory, a calculator, and an error output controller. The reference image plate has a reference white image on the surface of the plate, and the first memory stores a first reference value. The image reading device reads such a reference white image for one line in a main scanning direction. The peak value detector detects the smallest data among the data which are included in the reference white image read by the image reading device. Then, the calculator compares the smallest data detected by the peak value detector with the first reference value. The error output controller outputs a white image error when the smallest data is smaller than the first reference value.
In one example, the image reading apparatus according to the present invention may includes a second memory for storing a second reference value. By including the second memory to store a second reference value, the image reading apparatus according to the present invention may perform the additional operations. For example, the image reading device may read the reference white image for one line in the main scanning direction at first and second positions which are different from each other. The peak value detector then detects the smallest data among the data which are included in the reference white image read at the first and second positions by the image reading device. Then, the calculator compares each of the smallest data read at the first and second positions with the first reference value, and calculates a difference between the smallest data read at the first and second positions with the second reference value. Finally, the error output controller outputs a white image error caused by an exterior error factor when at least one of the smallest data read at the first and second positions is smaller than the first reference value and when the difference between the smallest data is greater than the second reference value, and outputs a white image error caused by an interior error factor when at least one of the smallest data read at the first and second positions is smaller than the first reference value and when the difference between the smallest data is smaller than the second reference value.
In one example, the image reading apparatus according to the present invention may include a third memory for storing a third reference value. By including the third memory, the image reading apparatus may perform the additional operations. For example, the reference image plate has a reference black image on the surface of the plate. The image reading device reads the reference black image for one line in a main scanning direction in a first condition in which a light source illuminates the reference image plate and in a second condition in which no light source illuminates the reference image plate. The peak value detector detects the greatest data among the data included in the reference black image read in the first and second conditions, respectively, by the image reading device. Then, the calculator compares the greatest data read in the first condition with the greatest data read in the second condition, and calculates a difference between the greatest data read in the first and second conditions with the third reference value. Finally, the error output controller outputs a black image error when the difference is greater than the third reference value.
In one example of the image reading apparatus according to the present invention, the first memory may include a plurality of first reference values which are user selectable.
In another example of the image reading apparatus according to the present invention, the image reading device may be co
Brinich Stephen
Lee Thomas D.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
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