JP2008017430A - Image reader and image-forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten adjustment time, and to restrain deterioration in image quality caused by variations in the quantity of light. <P>SOLUTION: An image reader has a reference white board and connects the output values of image data read by a plurality of image sensors CIS as image data of 1 line. Each image sensor CIS has: a VGA 21-3 for amplifying an output signal from the image sensor CIS, an AGC circuit 21-5 for adjusting the signal amplification factor of a signal amplified by VGA 21-3, and an ADC 21-4 for converting an analog value outputted from the corresponding image sensor CIS to a digital value. When the image sensor reads the reference white board, the AGC circuit 21-5 adjusts the signal amplification factor individually for each image sensor CIS, so that each read value of the image sensor CIS coincides with a prescribed value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a document moving type image reading apparatus including a plurality of image sensors, a copier, a printer, a facsimile including these functions and these functions in order to cope with a large size paper. The present invention relates to an image forming apparatus such as a digital multifunction peripheral.

  Conventional image forming apparatuses for A0 paper size generally use one contact image sensor (hereinafter simply referred to as CIS). In other words, the original is read by using a CIS having a length corresponding to the A0 paper width. However, the CIS corresponding to the A0 paper width is naturally increased in size, and the manufacturing cost is increased and the price tends to increase. For this reason, an image reading device or the like that reads a document by arranging five CISs corresponding to the A4 paper size in a staggered manner is already known.

  On the other hand, it is already known that when an original is read, if the image forming apparatus or the like correctly recognizes a white color as a reference, it affects the finish of image formation. For this reason, an adjustment called white reference adjustment that causes the image forming apparatus or the like to recognize white correctly is essential. Here, the white reference adjustment is an adjustment (gain adjustment) in which a value output from the CIS is increased to a certain output reference value by an amplifier (or signal amplifier) by light emitted from a light source before image formation.

  Until now, only one CIS has been used in a general image forming apparatus corresponding to the A0 paper size. Even if a problem occurs in white reference adjustment, the variation of the white reference in one CIS is It was possible to suppress variations by adjusting in the image processing process, which is a subsequent process (see, for example, JP-A-2001-157006).

  However, in the case of an image reading apparatus in which a plurality of CISs are arranged in a staggered manner to read a document equivalent to the A0 paper size, white reference adjustment of each CIS is performed by the same light emitted from one light source. However, since only one amplifier (or signal amplifier) that adjusts the white reference is provided, the white reference is adjusted to the output reference value for one CIS, but the white reference adjustment is performed up to the output reference adjustment for the other CIS. In some cases, the output maximum values of the respective CISs are not aligned and variations occur.

  Also, the white standard will be different for each CIS, and even if the same white is read, the output image will be different for each CIS. It could have an effect on the finish.

As an invention corresponding to these points, for example, an invention disclosed in Patent Document 2 has been proposed. The present invention suppresses variations in the white reference value of each CIS and can be adjusted so as to have a common white reference value in each CIS. The present invention has a reference white plate and is used for image data read by a plurality of image sensors. An image reading apparatus for reading image data relating to an entire original by connecting output values, and for each image sensor, an A / A that converts a signal amplifying unit and an analog value output from a corresponding image sensor into a digital value. D conversion means, and when each image sensor reads the reference white plate, read control that individually adjusts the amplification factor of the signal amplification means for each image sensor so that the read value by each image sensor is equal to a predetermined value It has a means.
JP 2001-157006 A JP 2005-198258 A

  In the invention described in Patent Document 2, the light source is turned on and off in order for each image sensor to adjust the amplification factor of the signal amplifying unit. Therefore, the adjustment (the more the number of CISs is) Takes time. Further, when adjusting one CIS, the light sources corresponding to the surrounding CIS are turned off, which is different from the situation when the original is actually read. May cause some differences.

  Therefore, a problem to be solved by the present invention is to make it possible to shorten the adjustment time and to suppress a decrease in image quality due to variations in the amount of light.

  In order to solve the above-described problem, the first means includes a reference white plate, and in the image reading apparatus that generates one line of image data by connecting output values of image data read by a plurality of image sensors. Signal amplification means for amplifying the output signal from the image sensor, amplification factor adjustment means for adjusting the signal amplification factor of the signal amplified by the signal amplification means, and the analog value output from the corresponding image sensor as a digital value An A / D conversion means for converting is provided for each of the image sensors, and the amplification factor adjusting means is configured so that when the image sensor reads the reference white plate, each reading value of the image sensor is aligned with a predetermined value. The signal amplification factor is individually adjusted for each image sensor.

  The second means is characterized in that in the first means, adjustment is performed when the amplification factor adjusting means turns on all the light sources.

  The third means is characterized in that in the first means, the gain adjustment means performs adjustment when the light source corresponding to the image sensor is turned on.

  According to a fourth means, in any one of the first to third means, the light source is provided for each of the image sensors.

  A fifth means is characterized in that, in the first or second means, one light source is provided in common to each of the image sensors.

  A sixth means is characterized in that in any one of the first to fifth means, a storage means for storing an individual gain setting value for each image sensor adjusted by the gain adjustment means is provided. To do.

  The seventh means is the sixth means wherein the storage means stores the latest set value when the last update is performed, each image sensor reads the reference white plate again, and the amplification factor adjusting means When adjusting the amplification factor, the adjustment is performed after reflecting the set value.

  The eighth means is characterized in that, in any one of the first to seventh means, the plurality of image sensors are arranged in a staggered pattern in the main scanning direction.

  A ninth means is characterized in that the image forming apparatus includes the image reading apparatus according to any one of the first to eighth means.

  In the embodiment described later, the reference white plate is denoted by reference numeral 4a, the image sensor is denoted by the contact image sensors CIS1 to CIS1, the amplifying means is a variable gain amplifier (VGA) 21-3, and the amplification factor adjusting means is an AGC circuit 21-5. Further, the A / D conversion means is an analog-digital conversion circuit (ADC) 21-4, the light source is 11, 12, 13, the storage means is the image memory 31, the image reading apparatus is 205, and the image forming apparatus is Each corresponds to reference numeral 200.

  According to the present invention, when the image sensor reads the reference white plate, the signal amplification factor is individually adjusted for each image sensor so that the read values of the image sensor are aligned with a predetermined value. It is possible to shorten the image quality, and it is possible to suppress a decrease in image quality due to a variation in the amount of light.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating a schematic configuration of a reading unit of an image reading apparatus according to the present embodiment, and FIG. 2 is a plan view of FIG. In these drawings, a front conveying roller (conveying roller: referred to as front in the figure) 2, a contact glass 5, a reading back member 4, and a rear conveying roller across an original conveying path from the upstream side to the downstream side in the original conveying direction. (Conveying roller: referred to as “rear” in the figure) 6 is provided, and a document insertion sensor 1 is disposed upstream of the front conveying roller 2 and a registration sensor 3 is disposed downstream. The contact glass 5 is provided to face the reading back member 4, and the first to third contact image sensors CIS 1, 2, 3 are arranged on the back side of the contact glass 5. As shown in FIG. 2, the first to third three contact image sensors CIS1, CIS2, and CIS3 are arranged in a staggered manner in the main scanning direction, and the reading ranges of the adjacent contact image sensors are adjacent to each other. R1, R2 and R3 are arranged overlapping in the main scanning direction. Of the three contact image sensors CIS1, CIS2, and CIS3, the second contact image sensor CIS2 is provided on the most upstream side in the sheet conveying direction, and the first and third image sensors are separated by a distance L in the sub-scanning direction. Contact image sensors CIS1 and CIS3 are arranged. In FIG. 2, R1 ′, R2 ′, and R3 ′ are document reading ranges.

  In the reading apparatus having such a configuration, the document 7 is inserted into the front conveying roller 2 from the left side in FIG. 1 (from the lower side in FIG. 2). When the document insertion sensor 1 detects a document, a front conveyance roller 2 and a rear conveyance roller 6 are rotated by a conveyance motor (not shown), and a document illumination light source (not shown) in the contact image sensors CIS1, 2 and 3 is turned on. Thereafter, the registration sensor 3 detects the leading edge of the document 7 and sequentially recognizes the position of the document 7 in the transport path. The image (lower surface) of the document 7 is read by the second contact image sensor CIS2 and then read by the first and third contact image sensors CIS1 and CIS3. The read signal of the second contact image sensor CIS2 is delayed by the time required for the sub-scanning between the second and first contact image sensors CIS2 and CIS1, and the signals of the third and first contact image sensors CIS1 and CIS3 are delayed. The read signal is delayed by the time required for sub-scanning between CIS3 and CIS1, and the signals of the first and third contact image sensors CIS1, 2, 3 are combined to obtain a read signal that is made into one line. The image of the document 7 is sequentially read while moving in the sub-scanning direction, and is discharged through the rear conveyance roller 6. In FIG. 2 (when the operation is viewed from the top), the document is conveyed from the bottom to the top.

  The side (the lower surface in the figure) facing the contact image sensors CIS1 to CIS3 of the reading back member 4 is formed as a white plate and functions as a reference white plate 4a. The reference white plate 4a is a reference for the white level of the image reading apparatus. The output level when the reference white plate 4a is read is determined in advance. This output level is hereinafter referred to as a white level target value.

  FIG. 3 is a block diagram showing an electrical configuration of the image reading apparatus. In the figure, the image reading apparatus includes first to third contact image sensors CIS1 to CIS1 to 1 to N reading pixels, first to third light sources 11, 12, and 13, respectively. The first to third signal processing blocks 21, 22, and 23 provided for each of the third to third CISs 1 to 3, the image memory 31, the timing control unit 32, and the memory 33 are configured. The first to third contact image sensors CIS1 to CIS1 to the first to third light sources 11, 12, and 13 are arranged in a staggered manner as shown in FIG. The contact image sensor 22 is provided on the upstream side in the sheet conveyance direction (upstream side in the sub-scanning direction) than the first to third contact image sensors 21 and 23. Each of the first to third signal processing blocks 21, 22, and 23 includes a signal amplification unit and an A / D conversion unit.

  The first to third light sources 11 to 13 are turned on by lighting control from the timing control unit 32. The first to third CISs 1 to 3 are imaging elements that convert optical signals (images) into electrical signals. The first to third signal processing blocks 21, 22, and 23 are used to amplify electrical signals, D conversion is performed and a read signal is output. The image memory unit 31 stores image data obtained by the image reading process, and transfers the data to the image processing unit of the image forming apparatus.

  FIG. 4 is a block diagram showing details of the signal processing block. In the signal processing block, signal processing from the output of the CIS to obtaining a digital image signal is executed. Since all of the first to third signal blocks 21 to 23 have the same configuration, the first signal processing block 21 that processes the output of the first image sensor CIS1 is shown here as a representative.

  The signal processing block 21 has a clamp circuit (CLMP circuit) 21-1 for defining the input terminal potential after AC coupling, and a sample hold circuit (SH circuit) 21 for extracting only the signal component of the output signal of the image sensor. -A variable gain amplifier (VGA) 21-3 that amplifies the signal after SH with a specified amplification factor, and is output as a digital image signal through an analog-digital conversion circuit (ADC) 21-4. The AGC circuit 21-5 detects the peak data of one line and adjusts the gain of the VGA so that the peak value becomes the white level target value. That is, the signal processing block 21 performs adjustment so that the output level when the reference white plate 4a is read becomes the white level target value. In the reference white plate 4a adjustment, for example, the user or the like starts up the image forming apparatus first in the morning. This is done every time when the power is turned on or when the power is turned off once in the energy saving mode.

  Note that the clamp circuit 21-1, the sample hold circuit 21-2, and the AGC circuit 21-5 are connected to a target & interface circuit (TG & I / F) 21-6, respectively. CLMPIN, SH, MCLK, SCLK, SD, CS, and SHGT signals are input to the TG & I / F circuit 21-6. Further, the signal processing block 21 itself is configured as one signal processing IC (ASIC) so that the signal processing of the three CISs 1 to 3 can be performed together.

  In the image reading apparatus configured as described above, an image corresponding to one output line of the CIS as shown in FIG. 4 is added to the signal processing blocks 21, 22, and 23 from the output of the CIS shown in FIG. An automatic gain adjustment (AGC) circuit 215 that detects the maximum value of data and changes the gain of the amplifier so that the value approaches the specified value is provided, so that the AGC circuit 21-5 reads the reference white plate 4a. The gain of the amplifier (variable gain amplifier-VGA 21-3) is adjusted individually for each CIS so that the output data is aligned to a predetermined value. Thereby, the gain of VGA21-3 can be adjusted for each CIS individually.

  Further, since the AGC circuit 21-5 is provided in the signal processing block 21 and has an automatic gain adjustment function, the gain adjustment of the VGA 21-3 of each CIS can be performed simultaneously. Thereby, the time of gain adjustment can be shortened. That is, the gain adjustment of all the VGAs 21-3 can be performed in the time required for the gain adjustment of one VGA 21-3.

  Further, when the gain of the VGA 21-3 is adjusted individually for each CIS so that the output data when the reference white plate 4a is read is aligned with a predetermined value, the VGA 21-3 is individually set for each CIS with all the light sources turned on. Adjust the gain. In this way, adjustment can be performed in the same environment as the actual operation, and deterioration in image quality due to variations in the amount of light can be suppressed.

  Further, when the gain of the VGA 21-3 is adjusted individually for each CIS so that the output data when the reference white plate 4a is read is aligned to a predetermined value, only the light source corresponding to each CIS is turned on. The gain of the VGA 21-3 can be adjusted individually. In this way, it is possible to cope with energy saving driving such as reading only by driving only the minimum necessary CIS by setting the document size and the like.

  In the example of FIG. 3, the light sources 11, 12, and 13 exist for each of the CISs 1, 2, and 3. When the light source is provided for each CIS in this way, the optimum gain adjustment of the amplifier can be performed for each CIS, and energy saving drive can be supported. On the other hand, if the light source is one common source for each CIS, the manufacturing cost can be reduced.

  When each CIS reads the reference white plate 4a, it has an image memory 31 for storing a set value when the amplification factor of the VGA 21-3 is individually adjusted for each CIS so that the read value by each CIS is aligned with a predetermined value. When the latest setting value (when the last update of the setting value is performed) is stored and the power is turned on again, each CIS reads the reference white plate 4a again and adjusts the amplification factor of the VGA 21-3. Adjusts after reflecting the latest set value. That is, the latest set value is stored, and when each CIS reads the reference white plate 4a again and adjusts the gain of the VGA 21-3, such as when the power is turned on, the adjustment is performed after reflecting the set value. As a result, it is possible to perform the adjustment from the adjustment close to the aim in advance, thereby further reducing the time required for the adjustment.

FIG. 5 is a diagram showing a schematic configuration of a wide digital copying machine as an image forming apparatus according to an embodiment of the present invention. In the figure, an image forming unit 200 is mounted on a paper feeding unit 100, and a reading unit (scanner unit) 300 is mounted on the image forming unit 200, thereby constituting a digital copying machine as a whole. Hereinafter, the configuration of each part will be described together with the operation.

First, a document is placed on the document table 301 of the reading unit 300, and this document is read one by one.
Feed the paper. Image information is read from a fed document by a contact image sensor (CIS) 302, and is discharged onto a discharge tray after the image is read. The document on the document table 301 is aligned in the width direction (the end in the direction orthogonal to the transport direction) by a side fence (not shown), fed by the feed roller 303, and transported to the lower side of the contact image sensor 302. The A document width detection sensor and a document length detection sensor are provided on the document table 301. The size of the document sent from the document table 301 is detected by both sensors. The document under the contact image sensor 302 is exposed by a light source such as an LED array or a fluorescent lamp, and the reflected light is imaged on the image sensor through the rod lens array, and photoelectric conversion is performed by the image sensor. After the document reading is completed, the document is discharged onto the discharge tray by the transport roller 304 and the discharge roller 305. In FIG. 5, the arrangement of the contact image sensor 302 is opposite to that in FIG. 1, but the vertical position is a relative story as long as they face the document surface of the read document.

The image forming unit 200 includes a developing unit 201, a fixing unit 202, and a paper discharge unit 203. An image signal read by the contact image sensor 302 is subjected to image processing.
Optical writing is performed on the photoconductor 205 uniformly charged by the charger. By this optical writing, an electrostatic latent image is formed on the photosensitive member 205. The electrostatic latent image is developed with toner by a developing device 201 provided on the downstream side of the LED writing unit 204 in the rotation direction of the photoconductor, and the toner image on the recording paper fed from the paper feeding unit 100 is developed. After being transferred by the transfer unit 209 and separated from the photosensitive member 205 by the separation unit 210, the fixing device 2 is moved by the conveyance belt 211.
It is conveyed to 02. The toner image transferred onto the recording paper is transferred by the fixing device 202, the original image is copied, and the recording paper on which the image is formed is discharged via, for example, the paper discharge sensor 216 of the paper discharge unit 203. The paper is discharged onto a paper discharge tray 206 on the upper surface of the image forming unit 200 by a paper roller 213.

The paper feed unit 100 has two upper and lower roll paper trays 101 and 102. The roll paper trays 101 and 102 can be pulled out from the apparatus housing in the left direction in the figure, and are configured to perform roll paper setting and jam processing with the tray being pulled out. Two roll papers can be set on each of the roll paper trays 101 and 102.

Each roll paper 103-106 wound around the paper tube is a pair of paper holders 107-1
10 is set in the paper feeding unit 100. Paper feed rollers 111 to 11 for each roll paper
4 is disposed near the roll paper. The roll papers sent out by the paper feed rollers 111 to 114 are roll cutter units 115 and 11 provided on the front side of the tray (left side in the figure).
6 is cut into a predetermined length and sent to the image forming unit 200. The cut and fed roll paper is synchronized with the image forming timing by the registration roller 208, guided to the photoconductor 205, and the image formed on the photoconductor 205 is transferred by the transfer unit 209 and separated. Separated from the photosensitive member 205 by the unit 210 and guided to the fixing unit 202 by the transport belt 211,
The image is thermally fixed. The roll paper on which the image is fixed is discharged by discharge rollers 212 and 213 that form a discharge unit 203. The paper discharge direction is switched by the branch claw 214 and is discharged to a paper discharge tray 206 on the upper surface of the image forming unit 200 or a paper discharge tray (not shown) behind the image forming unit 200.

Paper discharge sensors 215 and 216 are provided between the fixing unit 202 and the paper discharge roller 212, and between the paper discharge roller 212 and the paper discharge roller 213, respectively. The paper discharge sensors 215 and 216 discharge the roll paper. It is possible to determine whether or not the unit 203 exists.

Although not shown, the image forming unit 200 includes a drive control unit that drives the paper discharge rollers 212 and 213, and the reading unit 300 includes an operation start instruction and repeat information about the roll paper to be conveyed. An operation unit is provided for inputting copy and long sheet passing information.

The fixing unit 202 is supplied with AC power from a fixing roller in which a release layer is disposed on a metal tube, a pressure roller in which a rubber layer and a release layer are disposed on a metal tube, and AC power supply means for supplying AC power. A main heating unit for heating, an auxiliary power source, an auxiliary heat generating unit heated by being supplied with electric power supplied from auxiliary power, an electromagnetic motor for giving a rotational driving force to the fixing roller, and a charging voltage of the auxiliary power source A voltage sensor for detecting, temperature detecting means for detecting the surface temperature of the fixing roller / pressure roller, a relay gear for transmitting the rotational drive of the electromagnetic motor to the fixing roller, and the electromagnetic motor via the relay gear It is composed of a fixing drive gear for transmitting the obtained rotational force to the fixing roller.

  The present invention is not limited to the present embodiment, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims.

It is a figure which shows schematic structure of the reading part of the image reading apparatus which concerns on this embodiment. It is a top view of FIG. It is a block diagram which shows the electric constitution of an image reading apparatus. It is a block diagram which shows the detail of the signal processing block in FIG. 1 is a diagram illustrating an example of a system including an image reading device and a wide-width image forming device.

Explanation of symbols

4 Reading back member 4a Reference white plate 11, 12, 13 Light source 21, 22, 23 Signal processing block 21-3 Variable gain amplifier (VGA)
21-4 Analog to Digital Conversion Circuit (ADC)
21-5 AGC circuit 31 Image memory 32 Timing control unit 200 Image forming apparatus 205 Image reading apparatus CIS, CIS1 to 3 Contact type image sensor

Claims (9)

In an image reading apparatus having a reference white plate and connecting image data output values read by a plurality of image sensors to one line of image data,
Signal amplification means for amplifying the output signal from the image sensor, amplification factor adjustment means for adjusting the signal amplification factor of the signal amplified by the signal amplification means, and the analog value output from the corresponding image sensor as a digital value A / D conversion means for converting to each image sensor,
The gain adjustment means adjusts the signal gain individually for each image sensor so that each read value of the image sensor is equal to a predetermined value when the image sensor reads the reference white plate. A featured image reading apparatus.   2. The image reading apparatus according to claim 1, wherein the amplification factor adjustment unit performs adjustment when all light sources are turned on.   2. The image reading apparatus according to claim 1, wherein the amplification factor adjustment unit performs adjustment when a light source corresponding to the image sensor is turned on.   The image reading apparatus according to claim 1, wherein the light source is provided for each of the image sensors.   The image reading apparatus according to claim 1, wherein one light source is provided in common for each of the image sensors.   6. The image reading apparatus according to claim 1, further comprising storage means for storing individual gain setting values for each image sensor adjusted by the gain adjustment means.   The storage means stores the latest set value when the last update is performed, each image sensor reads the reference white plate again, and the amplification factor adjustment unit performs the adjustment when the amplification factor is adjusted. The image reading apparatus according to claim 6, wherein the adjustment is performed after the value is reflected.   The image reading apparatus according to claim 1, wherein the plurality of image sensors are arranged in a staggered manner in the main scanning direction.   An image forming apparatus comprising the image reading apparatus according to claim 1.

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