JP2007235833A - Document reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To speedily and stably obtain read images, even if overshoot or light quantity reduction occurs in a lamp which irradiates a document with light, in a document reading apparatus. <P>SOLUTION: A light source 121 irradiates a document to be read with light, while scanning the relevant document in a predetermined direction. Optical systems 122-125 guide reflection light to an image sensor 126. A light-shielding plate 129 is disposed so as to slide, in front of the image sensor 126, on the optical path of reflection light and adjusts the quantity of light to be incident to the image sensor 126. A light quantity adjusting section 160 adjusts the sliding amount of the light-shielding plate 129 so that the output value of the image sensor 126, based on the reflected light reflected from a reference document disposed along with a scanning direction becomes a prescribed value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an original reading apparatus, and more particularly to an improvement of an original reading apparatus that receives reflected light of light irradiated on an original and reads the original.

  This type of document reading apparatus has a configuration in which light is irradiated to a document from a long line lamp (light source) and the reflected light is received for each line by an optical line sensor such as a CCD. The scanner unit is configured.

  In such a document reading apparatus, an electrical signal output from the optical line sensor is used as an auto gain controller so that a stable image can be obtained even if the sensitivity of the optical line sensor varies or the amount of light from the line lamp varies. (AGC) is used for amplification and analog-digital conversion for image processing.

  However, if the AGC gain is set large, the S / N ratio can be improved and a high-quality image can be obtained. However, if the gain is set excessively, the optical line sensor is saturated and the image quality is likely to deteriorate.

Therefore, in the conventional document reading apparatus, the gain in AGC is set to be small. Japanese Patent Laid-Open No. 9-37027 (Patent Document 1) is of this type.
JP-A-9-37027

  However, in the above-described document reading apparatus, overshooting is likely to occur when the line lamp is turned on, and it is necessary to start scanning scanning after a certain period of time when the overshoot has stopped. Reading time could not be shortened depending on the gain setting.

  Further, the light amount of the line lamp tends to gradually decrease after overshooting. For example, when the line lamp is scanned with respect to a long original such as an A3 size original, the amount of light tends to decrease toward the rear end of the original and is uniform. There was room for improvement in obtaining a read image.

  The present invention has been made to solve such a problem, and even when an overshoot occurs in a light source that irradiates light on a document or a light amount decrease occurs after overshoot, a read image is quickly stabilized. An object of the present invention is to provide a document reading device obtained in this way.

  An original reading apparatus according to the present invention is an original reading apparatus that reads an original by receiving reflected light of light radiated on the original in a line shape by an optical line sensor, and reads the original in a predetermined direction with respect to the original. A light source that emits light while scanning, an optical system that guides the reflected light of the document to the optical line sensor, and is slidably disposed in front of the optical line sensor on the optical path of the reflected light. A light-shielding unit that adjusts the amount of light incident on the sensor, a reference document that is arranged along the scanning direction and reflects light from the light source, and an optical line based on reflected light that is reflected from the reference document along with the scanning A light amount adjusting unit that adjusts the light shielding unit so that the output value of the sensor becomes a specified value.

  In the present invention, it is also possible to form the light amount adjusting unit so as to adjust the light shielding unit from the average of the output values obtained during scanning.

  In the present invention, it is also possible to adopt a configuration in which the specified value in the light amount adjustment unit is the output value of the optical line sensor at the rear end in the scanning direction.

  Furthermore, in the present invention, a configuration in which the light shielding portion is a flat light shielding plate is also possible.

  Furthermore, in the present invention, as the light shielding portion, two light shielding plates arranged to be slidable in a direction orthogonal to the optical axis of the light output from the optical system are provided, and these light shielding plates have the optical axes on both sides. A configuration is also possible in which the amount of light is adjusted by sliding displacement in the direction sandwiched between.

  In the present invention, it is also possible to provide a driving means for sliding the light shielding portion in the light amount adjusting portion.

  In addition, the present invention has an auto gain controller that adjusts the gain of the electric signal output from the optical line sensor, and when the auto gain controller adjusts the light amount by the light amount adjusting unit, the gain is set to a constant value. A configuration that is set to 1 is also possible.

  According to such a document reading apparatus according to the present invention, the document is irradiated with light while scanning the document in a predetermined direction from the light source, and the reflected light of the document is guided from the optical system to the optical line sensor, A light-shielding part is slidably placed in front of the optical line sensor on the optical path of the reflected light, a reference document is arranged along the scanning direction, and the reflected light from the reference document is scanned along with the scanning of the light source. The light amount adjustment unit adjusts the light shielding unit so that the output value of the optical line sensor based on the reference value becomes a specified value. Therefore, in the process of scanning the light source on the read original, the reflected light from the reference original is monitored and Since the output value of the line sensor is stabilized at the specified value, a high-quality read image can be quickly obtained even if an overshoot occurs in the lamp that irradiates light to the document or if the light intensity decreases after the overshoot. Stable obtained.

  In the configuration in which the light amount adjustment unit is formed so as to adjust the light shielding unit from the average of the output values obtained during scanning, even if dust or the like is attached to the reference document or a protruding output value is obtained. Thus, it is possible to prevent malfunction of the light shielding portion due to the output.

  Further, with the configuration in which the specified value in the light amount adjusting unit is used as the output value at the rear end in the scanning direction, the appropriate specified value can be obtained reliably and easily even if the light amount of the light source is reduced.

  Further, in the configuration in which the light shielding portion is a flat light shielding plate, the light shielding plate can be easily slid.

  Furthermore, as the light-shielding portion, two light-shielding plates are provided in a direction orthogonal to the optical axis of the optical system, and the light-shielding plates are formed so as to adjust the amount of light by sliding displacement in a direction sandwiching the optical axis from both sides. Then, the light amount adjustment range can be increased without blocking the central direction of the optical axis.

  Further, in the configuration in which the driving unit for sliding the light shielding unit is provided in the light amount adjusting unit, the driving unit adjusts the sliding amount of the light shielding unit, so that the light amount of light incident on the optical system can be automatically adjusted. .

  Furthermore, in the configuration in which an auto gain controller that adjusts the gain of the electrical signal output from the optical line sensor is provided and the gain of the auto gain controller is set to a constant value, the light amount adjustment unit adjusts the light amount. Since the gain of the auto gain controller is set to a constant value, the light amount can be adjusted with higher accuracy.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic diagram showing an internal configuration of a document reading apparatus according to the present invention.

  In FIG. 1, the document reading unit 100 includes a document cover 110 and a document placement unit 120.

  The document cover 110 includes a document tray 111 on which a plurality of documents (not shown) to be read can be placed, a paper feed roller pair 112 for picking up the placed documents one by one, and a picked-up document. A registration roller pair 113 is provided that transports the document to the document reading position RP and regulates the oblique feeding of the document to adjust the leading edge of the document.

  In the vicinity of the registration roller pair 113, a timing switch 114 used for determining the conveyance timing of the leading edge of the original image to the original reading position RP is disposed.

  The document placement unit 120 is configured such that the light source 121 disposed below the document reading position RP and the reflected light of the document at the document reading position RP pass through optical systems such as mirrors 122, 123, and 124 and a condenser lens 125. And an optical line sensor (image sensor) 126 for receiving light.

  The light source 121 is composed of a line lamp or the like, and is arranged in a direction (main scanning direction) crossing the conveyance direction of the original to be read, and irradiates the original with light in a line shape via a contact glass 127 described later.

  A transparent and rectangular flat contact glass 127 is disposed on the upper surface of the document placing portion 120.

  A reference document 128, which will be described later, is attached to one end in the longitudinal direction on the lower surface of the contact glass 127 along this longitudinal direction (repeating direction of main scanning: sub-scanning direction) (see FIG. 3 described later).

  On the optical path of the reflected light of the document, a light shielding plate 129 is disposed at a position before the condenser lens 125 so as to be slidable in the + z direction or the −z direction which is a direction orthogonal to the optical axis.

  In the automatic reading mode in which the document placed on the document tray 111 is automatically conveyed, the light source 121 emits light to the document conveyed one by one by the paper feed roller pair 112 and the like in a fixed state. The line sensor 126 reads the reflected light, for example, in units of one line.

  In the manual reading mode in which the original placed on the contact glass 127 is read, the light source 121 emits light to the original and receives a driving force from a motor (not shown) in FIG. The optical line sensor 126 receives the reflected light from the original.

  For example, when the light source 121 moves to the position of the light source 121 ′ indicated by a dotted line, the light irradiation stops, receives a driving force from the motor, moves to the left at a constant speed, and the position of the light source 121 indicated by the solid line ( Return to home position.

  The optical line sensor 126 is composed of a CCD (Charge Coupled Device), a CIS (Contact Image Sensor), or the like, receives the reflected light of the original from the light source 121, and outputs an electric signal at a level corresponding to the amount of the reflected light. As a result, the image of the document is read line by line.

  The optical line sensor 126 outputs an electrical signal of a level based on the reflected light from the region of the reference original 128 arranged on the contact glass 127 in the image for each line. In the present invention, the output value is used, and details will be described later.

  The document reading apparatus 100 includes a plurality of paper feeding cassettes, a plurality of paper feeding rollers, a transfer roller, a photosensitive drum, a developing device, an exposure device, a fixing roller, a discharge port, a discharge tray, and the like (images). Forming apparatus) is generally connected, but since it is a known one, its illustration and description are omitted.

  FIG. 2 is a configuration diagram of the light shielding plate 129. In FIG. 2, the longitudinal direction of the optical line sensor 126 is the x direction, and the direction orthogonal to each of the x and y directions is z in the plane in which the optical axis direction of the reflected light of the document is the y direction and the y direction is the normal line. The direction.

  As shown in FIG. 2, the light shielding plate 129 is disposed on the upstream side of the condenser lens 125 on the optical path of the reflected light and in the vicinity of the condenser lens 125. A columnar member 131 having a longitudinal direction in the z direction is formed on one side of the light shielding plate 129 in the x direction, and a rack gear 132 having a longitudinal direction in the z direction is formed on the other side.

  A pinion gear 133 is attached to the tip of the rotating shaft of the motor M1, and this pinion gear 133 is engaged with the rack gear 132 so that the light shielding plate 129 slides in the + z direction or the −z direction under the torque of the motor M1. It has become. An example of the motor M1 is a stepping motor.

  The light shielding plate 129 is made of a plastic material having a black surface and a flat plate shape, and the length in the x direction is selected to be longer than that of the condenser lens 125.

  Therefore, as the light shielding plate 129 slides in the + z direction, the amount of light guided to the optical line sensor 126 decreases, and as the light shielding plate 129 slides in the −z direction, the amount of light guided to the optical line sensor 126 increases.

  FIG. 3 is a view when the contact glass 127 is viewed from above. As shown in FIG. 3, it can be seen that a strip-shaped reference document 128 is attached to one end in the longitudinal direction (y direction) of the contact glass 127. The reference document 128 is made of, for example, a member such as uniform white plastic, and an electric signal is output from the optical line sensor 126 based on the reflected light in the width direction (x direction).

  That is, in the reflected light line a of the line portion in FIG. 3, an electric signal based on the reflected light of the region portion b corresponding to the width of the reference document 128 is used for adjusting the light shielding plate 129.

  4 is a block diagram showing an electrical configuration of the document reading apparatus shown in FIG. The document reading unit 100 includes an optical line sensor 126, an AFE (analog front end) 140, an image processing unit 150, a light amount adjustment unit 160, an image memory 170, and a control unit 180. In FIG. 4, only the present invention is shown.

  The optical line sensor 126 outputs, to the AFE 140, an electrical signal indicating the image density of the original read line by line under the control of the control unit 180.

  The AFE 140 amplifies an analog electric signal (hereinafter, referred to as “analog output value”) output from the optical line sensor 126 under the control of the control unit 180, and the like. Gain controller) 142 and A / D converter 143, and separately outputs output values based on reflected light from the reference document 128 together with document image data for each line.

  The CDS processing unit 141 performs correlated double sampling on the analog output value output from the optical line sensor 126 to remove fixed pattern noise.

  The AGC 142 is output from the CDS processing unit 141 using the gain determined by the image processing unit 150 so that the analog output value becomes an appropriate level for A / D conversion by the A / D converter 143. Amplifies the analog output value.

  The A / D converter 143 converts the analog output value amplified by the AGC 142 into a digital electrical signal (hereinafter referred to as “digital output value”), and outputs the document image data to the image processing unit 150 to be a reference document. The output value based on the 128 reflected light is output to the light amount adjusting unit 160.

  The image processing unit 150 performs predetermined image processing on the digital image data output from the A / D converter 143 and outputs the result to the image memory 170.

  The light amount adjustment unit 160 operates with an output value based on the reflected light from the reference document 128 for each line when the control unit 180 is set to a light amount adjustment mode to be described later. A comparison unit 162 and a reference value storage unit 163 are included.

  The light amount adjustment unit 160 includes a mechanism for adjusting the light shielding plate 129 in addition to a motor M1 described later.

  The average value calculation unit 161 calculates an average value of digital output values of each pixel in one line for the reference document 128 portion output from the A / D converter 143, and calculates an average value for a plurality of lines. You may do it.

  The comparison unit 162 compares the specified value as the reference value stored in advance in the reference value storage unit 163 with the average value calculated by the average value calculation unit 161, and drives the motor M1 so that both values match. Then, the light shielding plate 129 shown in FIG. 2 is controlled to slide in the + z direction or the −z direction.

  The specified value stored in the reference value storage unit 163 is a digital output value that should be output by the A / D converter 143 based on the reflected light from the reference document 128 when the light source 121 moves to the rear end in the sub-scanning direction. The value measured experimentally beforehand is adopted.

  The control unit 180 is formed from a CPU, a ROM, a RAM, and the like, and controls the entire document reading apparatus. In the present embodiment, in particular, the optical line sensor 126, the AFE 140, the image processing unit 150, the light amount adjustment unit 160, and the image memory 170. A clock signal for synchronizing the signals is output to synchronize the operations of these blocks.

  FIG. 5 is a flowchart showing light amount adjustment processing in the document reading apparatus. For example, it is assumed that the light amount adjustment mode is performed under the control of the control unit 180 in the process of turning on the power of the document reading apparatus and reading the document.

  First, in step S1, the image processing unit 150 sets the gain of the AGC 142 to a predetermined value. Here, as the gain value set by the image processing unit 150, a predetermined value is adopted when the light amount adjustment unit 160 adjusts the light amount, and a constant value is set while the light amount adjustment is performed. .

  In step S <b> 2, the control unit 180 emits light from the light source 121 to one line including the reference document 128, and the optical line sensor 126 receives the reflected light and outputs an analog output value for one line to the AFE 140. .

  The AFE 140 performs the above-described processing on the analog output value to generate a digital output value, and sequentially outputs the digital output value based on the reflected light from the reference document 128 to the average value calculation unit 161.

  In step S3, the average value calculation unit 161 adds the digital output value of each pixel corresponding to the width of the reference document 128 for one line, and divides the added value by the corresponding number of pixels to calculate the digital output value. An average value for each pixel is calculated.

  Here, the average value calculation unit 161 may calculate an average value for the past digital output values of two or more lines along the sub-scanning direction for the reference document 128.

  In step S4, the comparison unit 162 compares the specified value stored in the reference value storage unit 163 with the average value calculated by the average value calculation unit 161, and the average value calculated in step S5 is compared with the specified value. The light shielding plate 129 is slid so that

  Here, the comparison unit 162 slides the light shielding plate 129 with a predetermined step width, and the optical line sensor 126 reads one or more lines of the reference document 128 each time the light shielding plate 129 is slid, and calculates an average value. Each time the light shielding plate 129 is slid, the calculating unit 161 calculates an average value of the digital output values for each pixel.

  Further, the comparison unit 162 may reduce the step size for sliding the light shielding plate 129 as the average value calculated by the average value calculation unit 161 approaches the specified value.

  The comparison unit 162 may slide the light shielding plate 129 so that the average value calculated by the average value calculation unit 161 is within a certain specified range including the specified value.

  As described above, in the document reading apparatus according to the present invention, when the optical line sensor 126 reads the reflected light obtained from the reference document 128 in the process of scanning the light source 121 in the sub scanning direction with respect to the document to be read. Since the slide amount of the light shielding plate 129 is adjusted so that the amount of light incident on the condenser lens 125 becomes a predetermined value, even if an overshoot occurs in the light source 121 that irradiates light on the document, the received light amount is suppressed. Light can enter the condensing lens 125, and it is not necessary to start reading after the overshoot is settled. The reading can be started quickly, and the image reading can be shortened.

  Even if the light amount decreases after overshooting, the optical line sensor 126 can receive light with a stable amount of received light in the sub-scanning process of the light source 121, and a uniform high-quality image can be obtained in the entire area of the read original.

  In addition, if the output value at the rear end in the sub-scanning direction is used as the specified value in the light amount adjusting unit 160, the specified value can be easily obtained in the process of sub-scanning the light source 121 in advance, and the state with the lowest light amount is specified Therefore, a read image can be obtained reliably and stably.

  In addition, since the data based on the light reflected from the reference document 128 is averaged to obtain data for adjusting the position of the light shielding plate, erroneous detection can be avoided even if dust or the like adheres to the reference document 128.

  By the way, although one light shielding plate 129 is used in the above-described embodiment, the present invention is not limited to this, and two light shielding plates may be used.

  FIG. 6 is a view showing a light shielding portion composed of two light shielding plates. As shown in FIG. 6, the light shielding unit 400 is disposed at a position in front of the condenser lens 125 on the optical path of the reflected light of the document, and is arranged in the x direction between the two light shielding plates 401 and 402 and the light shielding plates 401 and 402. It includes light shielding side plates 403 and 404 provided on both sides.

  The light shielding plates 401 and 402 and the light shielding side plates 403 and 404 have a flat plate shape, and are made of a member such as black plastic, like the light shielding plate 129 shown in FIG.

  Columnar members 405 and 406 having a longitudinal direction in the z direction are attached to one side of the light shielding plates 401 and 402 in the x direction.

  In addition, rack gears 407 and 408 having a longitudinal direction in the z direction are attached to the other side of the light shielding plates 401 and 402. The rack gears 407 and 408 are meshed with pinion gears 409 and 410 attached to the ends of the rotation shafts of the motors M2 and M3, and the light shielding plates 401 and 402 are driving forces of the motors M2 and M3 controlled by the light amount adjustment unit 160. In response, it slides in the + z direction or the −z direction to be positioned.

  As shown in FIG. 6, if the light shielding plates 401 and 402 slide so as to sandwich the optical path from the vertical direction with respect to the optical path of the reflected light of the original, the reflected light of the original is guided to the center of the condenser lens 125. The adjustment range can be further expanded.

  The document reading apparatus according to the present invention is not limited to an image scanner unit, and can be widely applied to image forming apparatuses such as a copying machine, a facsimile machine, and a digital multifunction machine.

1 is a diagram showing a schematic configuration of a document reading apparatus according to the present invention. It is a perspective view which shows the light-shielding plate used for this invention. It is a figure when the contact glass used for the document reading apparatus which concerns on this invention is seen from upper direction. 1 is a block diagram showing an electrical configuration of a document reading apparatus according to the present invention. 6 is a flowchart for explaining the operation of the document reading apparatus according to the present invention. It is a figure which shows the light-shielding part comprised from two light-shielding plates.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Document reading part 110 Document cover 111 Document tray 112 Feed roller pair 113 Registration roller pair 114 Timing switch 120 Document placing part 121, 121 'Light source 122, 123, 124 Mirror (optical system)
125 condenser lens (optical system)
126 Optical line sensor (image sensor)
127 Contact glass 128 Reference document 129, 401, 402 Light shielding plate (light shielding portion)
131 Columnar member 132 Rack gear 133 Pinion gear 140 AFE (analog front end)
141 CDS processing unit 142 AGC (auto gain controller)
143 A / D converter 150 Image processing unit 160 Light amount adjustment unit 161 Average value calculation unit 162 Comparison unit 163 Reference value storage unit 170 Image memory 180 Control unit 400 Light shielding units 403 and 404 Light shielding side plates 405 and 406 Columnar members 407 and 408 Rack gear 409, 410 Pinion gear M1-M3 motor

Claims (7)

An original reading device that reads an original by receiving reflected light of a light irradiated in a line shape on an original to be read by an image sensor,
A light source that emits light while scanning the original in a predetermined direction of the original;
An optical system for guiding reflected light of the document to the image sensor;
A light-shielding unit that is slidably disposed in front of the image sensor on the optical path of the reflected light, and adjusts the amount of light incident on the image sensor;
A reference document that is arranged along the scanning direction and reflects light from the light source;
A light amount adjustment unit that adjusts the light shielding unit so that an output value from the image sensor based on reflected light reflected from the reference document in association with the scanning becomes a specified value;
An original reading apparatus comprising: The document reading apparatus according to claim 1, wherein the light amount adjusting unit adjusts the light shielding unit based on an average of the output values obtained during the scanning. The document reading apparatus according to claim 1, wherein the light amount adjustment unit sets the output value at the rear end in the scanning direction as the specified value. The document reading apparatus according to claim 1, wherein the light shielding portion is a flat light shielding plate. The light-shielding portion has two light-shielding plates slidably arranged in a direction perpendicular to the optical axis of light output from the optical system, and these light-shielding plates slide in a direction sandwiching the optical axis from both sides. 5. The document reading apparatus according to claim 1, wherein the light amount is adjusted by being displaced. The document reading apparatus according to claim 1, wherein the light amount adjustment unit includes a driving unit that slides the light shielding unit. An auto gain controller for adjusting a gain of an electric signal output from the image sensor;
7. The document reading apparatus according to claim 1, wherein the auto gain controller is configured to set a gain to a constant value when the light amount is adjusted by the light amount adjusting unit.

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