JPH11136473A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader capable of eliminating the influence of stains on a carrying roller surface even when a density read from the carrying roller surface is used as a white reference value, as well as capable of reflecting the secular change of sensor element sensitivity and illumination irregularity on the white reference value. SOLUTION: This image reader has a carrying roller in contact with a sensor so that an original is carried by the carrying roller for reading images. More specifically, the carrying roller 11 whose surface is white is provided on the opposite position of a contact sensor 2, and a control part 1 rotates the carrying rollers 11 to read a picture element density for one line respectively from the plural rotating positions of the carrying roller surface and sets density data for one line for which a value for indicating the whitest value among the read plural picture element densities is obtained as the density data of the picture element as the white reference value. Also, when the setting of the white reference value is instructed by an operation part 7, the white reference value is set.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus used in a facsimile apparatus, a copying machine, and the like, and more particularly to an image reading apparatus that obtains a white reference value and performs shading correction and the like.

[0002]

2. Description of the Related Art In an image reading apparatus in which a reading line is illuminated by a light source and reflected light from the reading line is read by a contact line sensor (hereinafter abbreviated as a sensor) such as a CCD, the sensitivity variation of a sensor element corresponding to a pixel and the illumination. Due to unevenness, the density may differ depending on the position even on the same density paper. For this reason, conventionally, shading correction for correcting the above-described sensitivity variation and illumination unevenness has been performed by reading the density of one line on a clean white tape surface or the like in advance. As shown in FIG. 5, for example, in a configuration in which the original S runs on the sensor by the transport rollers 11a disposed before and after the sensor 2a (before and after the reading line), the white tape 21 is opposed to the sensor 2a. The shading correction is performed using the density read from the white tape 21 as a white reference value. The transport rollers 11a are arranged before and after the sensor 2a in order to prevent the document S from fluttering on the sensor. Further, in order to reduce the number of parts and reduce the cost, a transport roller having a white surface is opposed to the sensor, and the original is transported by the transport roller, and the density read from the surface of the transport roller is defined as a white reference value. A method is also provided (see FIG. 2).

[0003]

However, in the prior art as described above, in which the density read from the surface of the transport roller is used as the white reference value, there is a problem that the white reference value is affected by dirt on the surface of the transport roller. is there. Further, in the method of using the white reference value acquired at the time of shipment in which the surface of the conveying roller is not stained, there is a problem that the white reference value does not reflect the temporal change of the sensor element sensitivity and the temporal variation of the illumination unevenness. An object of the present invention is to solve the above-described problems of the conventional technology, and to eliminate the influence of dirt on the surface of the conveyance roller by using the density read from the surface of the conveyance roller as a white reference value, and to reduce the sensitivity of the sensor element. It is an object of the present invention to provide an image reading apparatus capable of reflecting a change with time of illumination and a change with time of illumination unevenness in a white reference value.

[0004]

According to a first aspect of the present invention, there is provided an image forming apparatus, wherein a transport roller faces a sensor, a document is transported by the transport roller, and an image is read by the sensor. In the reading device, the surface of the conveyance roller provided at the position opposing the sensor is white, and the conveyance roller is rotated, and the pixel density of one line of the conveyance roller surface is read from each of the plurality of rotation direction positions of the conveyance roller, White reference value setting means for setting, as a white reference value, one line of density data in which a value indicating a whitest value among a plurality of read pixel densities is obtained as density data of the pixel for each pixel; It is characterized by that. According to a second aspect of the present invention, in addition to the apparatus configuration of the first aspect, there is provided a white reference value setting instructing unit for instructing the setting of a white reference value. The white reference value setting means is configured to set a white reference value when a value setting is instructed. According to a third aspect of the present invention, in addition to the apparatus configuration of the first aspect, a time counting means for counting an accumulated image reading time or a counting means for counting the number of accumulated image reading pages or the number of accumulated image reading lines is provided. Each time the cumulative image reading time counted by the timing means reaches a predetermined value, or each time the cumulative image reading page number or the cumulative image reading line number counted by the counting means reaches a predetermined value, a white reference is set. The white reference value setting means is configured to set the value.

With the above arrangement, according to the first aspect of the present invention, a value indicating the whitest value among a plurality of pixel densities read from a plurality of rotation direction positions of a conveying roller having a white surface is obtained. The density of one line obtained as the density of each pixel is set as a white reference value. Even if the white surface of the transport roller becomes dirty, that portion is not taken in as a white reference value, and therefore, the white reference value is not affected by such contamination. According to the second aspect of the present invention, the white reference value is set when an instruction to set the white reference value is issued. Updates can be made. According to the third aspect of the present invention, the white reference value is set each time the cumulative image reading time reaches a predetermined value, or each time the cumulative image reading page number or the cumulative image reading line number reaches the predetermined value. Therefore, it is possible to reflect variations in sensor element sensitivity and changes over time in illumination unevenness in the white reference value without troublesomeness, and thus it is possible to reflect it in shading correction and the like.

[0006]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a control system of a facsimile apparatus including an image reading apparatus according to a first embodiment of the present invention. As shown in the figure, the facsimile apparatus includes a control unit 1 for controlling and managing the entire facsimile apparatus, a contact sensor 2 for reading an image on a document, an analog signal output from the contact sensor 2, and a shading correction. Image processing unit 3 for performing image processing, image processing R used for the image processing
AM4, a transport motor 5 for rotating a transport roller to transport a document, a system RAM 6 backed up by a battery used for system control, an operation unit (OPU) 7 including keys and a display device, and images and characters on a recording paper. It has a plotter 8 for outputting, a modem 9 for modulating and demodulating during facsimile transmission and reception, and a network control unit (NCU) 10 connected to a public telephone line and performing line connection control and the like. In addition,
The control unit 1 has a CPU and a R
OM and the like. FIG. 2 shows the structure of the main part of the image reading device of the facsimile machine. As shown in the drawing, the contact sensor 2 and the transport roller 11 are opposed to each other with a contact glass (not shown) interposed therebetween. It is designed to run on top. The surface of the transport roller 11 is white. Note that the white reference value setting means described in the claims section is
It comprises a control unit 1, an image processing unit 3, an image processing RAM 4, a system RAM 8, and the like. The white reference value setting means is constituted by the operation unit 7. The function of the clock means or the counting means is performed by the CPU 1.

According to the facsimile apparatus having the above-described configuration, in this embodiment, the conveying roller 11 having a white surface is used.
The surface density is read and is set as a white reference value for shading correction and the like. Hereinafter, the operation of the first embodiment will be described according to the operation flow shown in FIG. First,
The controller 1 sets the value of the number of comparisons N set in a predetermined area in the system RAM 6 to 0 (S1). Then, with the transport roller 11 stopped, the density of each pixel for one line is read by the contact sensor 2 from the contact roller facing surface of the transport roller 11 (S2). Further, after reading, the control section 1 stores the density data of each pixel digitized by the image processing section 3 in a predetermined area of the image processing RAM 4 (S3). Subsequently, the control unit 1 drives the transport motor 5,
For example, the transport roller 11 is rotated and stopped by 30 degrees (S4). Then, at this position, the density of each pixel for one line is read again from the surface of the conveying roller 11 facing the contact sensor (S5), and the image processing RAM is read for each pixel.
The density data stored in the predetermined area 4 is compared with the newly read density data, and the larger value (in this example, the larger value is whiter) is used as the density data of each pixel. It is stored in the above area (S6).
Further, the value of the number of comparisons N is increased by 1 (S7).

Subsequently, it is determined whether or not the number of comparisons N has reached a predetermined number of times (11 in the example of FIG. 3) (S
8) If not reached (No in S8), repeat from step S4. When the comparison is performed a predetermined number of times (Yes in S8), the operation flow is terminated. As described above, according to this embodiment, the density data of a plurality of lines are read from a plurality of positions that are shifted from each other in the rotation direction on the surface of the white transport roller 11, and each pixel has the whitest data. Is stored as a white reference value in a predetermined area of the image processing RAM 4. Therefore, even if a part of the surface of the transport roller 11 is dirty, the part is excluded from the white reference value, so that the white reference value is not affected by such a dirt. Appropriate shading correction or the like can be performed depending on the value. In addition,
The white reference value obtaining operation in the above operation flow can be performed at the time of shipment or when necessary, by pressing a predetermined key in the operation unit 7, or by selecting a menu displayed on the display device.

FIG. 4 is a flowchart showing the operation of the second embodiment of the present invention. In this embodiment, the white reference value is automatically acquired and updated every time the cumulative number of read pages reaches a predetermined value. Hereinafter, the operation of this embodiment will be described with reference to FIG. As shown in FIG. 4, the cumulative read page number N of a predetermined area of the system RAM 6 is:
First, it is set to 0 (for example, at the time of shipment) (S11). Thereafter, every time one page of the image is read, the cumulative read page number N is incremented by one (S12 → S13 → S
12), a predetermined number of pages set in advance (3 in the example of FIG. 4).
When it reaches (00 pages) (Yes in S13), the white reference value obtaining operation (white reference data reading operation) shown in the first embodiment (FIG. 3) is started (S14). Instead of counting the number of cumulative read pages, the number of cumulative read lines may be counted, and when the value reaches a predetermined value, the white reference value obtaining operation may be started. Alternatively, the time required from the start of reading to the end of reading may be measured, and the white reference value obtaining operation may be started when the cumulative reading time obtained by calculating the cumulative value reaches a predetermined value. As described above, in this embodiment, the white reference value is automatically updated each time a predetermined amount of reading is performed. Can be reflected in the white reference value, and thus can be reflected in shading correction and the like. In the above description, the sensor is not limited to the contact sensor.

[0010]

As described above, according to the present invention,
According to the first aspect of the present invention, a value indicating the whitest value among a plurality of pixel densities read from a plurality of rotation direction positions of a conveying roller having a white surface is obtained as a density of each pixel. Since the density is set as the white reference value, even if the white surface of the conveying roller becomes dirty, the portion is not taken in as the white reference value, and therefore, the white reference value is not affected by such a stain. According to the second aspect of the present invention, the white reference value is set when an instruction to set the white reference value is issued. Updates can be made.
According to the third aspect of the present invention, the white reference value is set each time the cumulative image reading time reaches a predetermined value, or each time the cumulative image reading page number or the cumulative image reading line number reaches the predetermined value. Therefore, it is possible to reflect the variation of the sensor element sensitivity and the temporal change of the illumination unevenness in the white reference value without any trouble, and therefore, it can be reflected in the shading correction and the like.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a facsimile apparatus according to a first embodiment of the present invention.

FIG. 2 is a structural explanatory view of a main part of the image reading apparatus according to the first embodiment of the present invention.

FIG. 3 is an operation flowchart of the image reading apparatus according to the first embodiment of the present invention.

FIG. 4 is an operation flowchart of an image reading apparatus according to a second embodiment of the present invention.

FIG. 5 is a structural explanatory view of a main part of an image reading apparatus showing an example of a conventional technique.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 control unit, 2 contact sensor, 3 image processing unit, 4 image processing RAM, 5 transport motor, 7 operation unit, 11
Transport rollers.

Claims (3)

[Claims] 1. An image reading apparatus in which a transport roller is opposed to a sensor and a document is transported by the transport roller and an image is read by the sensor, a transport roller having a white surface provided at a position facing the sensor and the transport roller. Is rotated, and the pixel density on the surface of the transport roller for one line is read from each of the plurality of rotation direction positions of the transport roller, and for each pixel, the value indicating the whitest value among the read pixel densities is calculated. An image reading apparatus comprising: a white reference value setting unit configured to set, as a white reference value, one line of density data obtained as pixel density data. 2. A white reference value setting instructing means for instructing setting of a white reference value, wherein the white reference value setting means is provided when the setting of the white reference value is instructed by the white reference value setting instructing means. The image reading apparatus according to claim 1, further comprising a function of setting a white reference value. 3. The image processing apparatus according to claim 1, further comprising: a timer for counting an accumulated image reading time, or a counting unit for counting the number of accumulated image reading pages or the number of accumulated image reading lines, wherein the white reference value setting unit is clocked by the timing unit. A function of setting a white reference value every time the cumulative image reading time reaches a predetermined value or each time the number of cumulative image reading pages or the number of cumulative image reading lines counted by the counting means reaches a predetermined value. The image reading device according to claim 1, wherein: