JP2002232649A - Image reader, image forming device and image reading method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader, an image forming device and an image reading method, which can correct read image data deterioration that occurs during automatically feeding an original. SOLUTION: Whether reading is made by a platen or automatic document feeding is detected (refer to S-2), when reading by the platen is detected, the light quantity of platen reading is set (S-4), and when reading by automatic document feeding is detected, the light quantity of the automatic document feeding is set (S-3), and original reading is carried out (S-5).

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 such as a scanner for reading an image of an original, which is used in a copying machine or the like, and more particularly to controlling the amount of light applied to the original.

[0002]

2. Description of the Related Art Conventionally, an image reading section in a digital image forming apparatus has a configuration in which an original is irradiated by a light source, and reflected light of the original is converted into an electric signal by a photoelectric conversion element group (CCD) to read image information. ing.

In a digital copying machine for personal use, in order to reduce the size of the apparatus, the distance between the original and the photoelectric conversion element group (CCD) is reduced in an image reading system, and a special lens called a rod lens array is used. 1: 1 optical system is used.

In order to efficiently read a document,
2. Description of the Related Art Many image forming apparatuses equipped with an automatic document feeder that transports a plurality of documents in order on a platen (also referred to as a platen) so that a reading unit surface faces a platen (also referred to as a platen) have appeared. . When such an automatic document feeder is mounted on a personal digital copying machine, the apparatus cannot be designed to be small in a configuration in which a document passes directly on a document table.

Therefore, between the document table and the document conveyance path,
A transparent protective member capable of exposing an original such as a mylar is provided, and the original can be read through the protective member to reduce the size.

[0006]

However, in the above-described document reading section, when the document is read while being pressed by the pressure plate, in the case of reading the document by automatic document feeding, only the thickness of the transparent protective member such as Mylar is used. Since the distance from the optical system to the document is long and the transparent protective member is present, the amount of light is attenuated.

For this reason, when the optical system is a contact type sensor (actual magnification optical system), when the original is read by an automatic document feeder, there is a difference in the amount of light imaged by the photoelectric conversion element. However, there is a problem that the reproducibility of the read image differs depending on the reading unit system.

The present invention has been made under such circumstances, and provides an image reading apparatus, an image forming apparatus, and an image reading method which can correct deterioration of read image data which occurs in automatic document feeding. It is intended to provide.

[0009]

In order to achieve the above object, according to the present invention, an image reading apparatus is configured as described in (1) to (4) below, and an image forming apparatus is configured as described in (5) below. And the image reading method is configured as in the following (6).

(1) Detecting means for detecting whether reading is performed by a pressure plate or reading by automatic document feeding, and light amount controlling means for controlling a light amount for irradiating a document in accordance with a detection result by the detecting means. Image reading device.

(2) A transparent document table, a light source for irradiating the document via the document table, and photoelectric conversion means for receiving the document reflected light including document image information, converting the reflected light into an electric signal, and outputting the signal. An image reading apparatus, comprising: a document pressing member; wherein, in a state where the document is pressed onto the document mounting table by the document pressing member, a document image is read by a document reflected light transmitted through the document mounting table. A first document image reading unit, a loading table on which a plurality of documents are loaded, and a transport that separates and sends out the documents on the loading table one by one and transports them to a transparent transport member that is in contact with the document loading table. Having a separating means, and in a state where the original is passing through the transparent conveying member,
A second document image reading unit that reads a document image by using document reflected light transmitted through the document table and the conveyance member, and a detection unit that detects which of the first and second document image reading units is used; An image reading apparatus comprising: means for controlling a light amount of the light source according to a detection result of the detecting means.

(3) The image reading apparatus according to the above (1) or (2), wherein the light amount control means controls the amount of current by controlling a current value supplied to the light source.

(4) The image reading apparatus according to (1) or (2), wherein the light amount control means controls light amount by controlling a duty ratio for determining a lighting time of the light source.

(5) An image forming apparatus comprising the image reading device according to any one of (1) to (4).

(6) A detecting step for detecting whether reading is performed by a pressure plate or reading by automatic document feeding, and a light amount control step for controlling a light amount for irradiating the document in accordance with the detection result of the detecting step. Image reading method.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to embodiments of a digital copying machine. The present invention is not limited to the form of the device, but is supported by the description of the embodiment,
It can also be implemented in the form of a method.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 1. Configuration of “Digital Copier” as Embodiment 1.1 Overall Configuration FIG. 1 is a block diagram illustrating a configuration of a control system in the digital copier of the present embodiment. As shown in the figure, the apparatus comprises an image reading section, an automatic document feed (hereinafter referred to as DF) section, an image processing circuit, an image output section (printer), a controller, a control operation section, and the like.

Referring to FIG. 1, the copying operation by the digital copying machine will be described first. An image processing circuit (IPU) that reads an original pressed by the pressure plate and the original platen or an original conveyed by the DF unit by the CCD of the image reading unit 1-1, converts the original into an electric signal, and converts the electric signal into image data of the first format
Send to 1-2.

The image processing circuit 1-2 having received the image data of the first format performs each processing (described in detail in 1.6) on the data to generate image data of the second format. The image is transmitted to an image output unit (here, a printer) 1-5. The printer forms an image based on the received image data of the second format, thereby enabling a copying operation.

Reference numeral 1-3 denotes a controller, a ROM 1-3a for storing programs and data therein, and a RAM 1-3b.
The CPU 1-3c in the circuit controls and drives the light amount control circuit 1-7 based on the light amount condition set by the control operation section 1-4.

Hereinafter, the structure of an image reading unit using a pressure plate, D
The configuration of the image reading unit, the configuration of the light amount control unit, the configuration of the image forming unit, the configuration of the image processing unit, and the control processing operation according to the present invention will be described.

1.2 Image Reading Unit Using Pressure Plate The configuration and operation of the image reading unit using the pressure plate and the image data of the first format will be described with reference to FIGS.

An image reading unit using a pressure plate is provided with an original platen glass 4-1 on which an original is placed, a pressure plate 4-2 which is a part of a DF which can press and open the original platen glass 4-1 and optical scanning. It is composed of a system unit 4-5.

A flatbed scanner using an equal-magnification optical system will be described with reference to FIG. A contact image sensor (CS: contact sensor) is taken as an example of the optical system. In the CS, a linear light source 1-8 and a light receiving sensor unit 4-4 (hereinafter, referred to as CCD) are integrally formed by a frame. The original reflected light enters the lens array 4-3 at the same magnification,
The image is read by a CCD 4-4 mounted in a frame with a document width and converted into an electric signal (analog signal). The original image can be read by sliding the CCD 4-4 along the original platen glass 4-1.

The image signal output from the CCD 4-4 is an analog signal representing the density of each pixel, and the signal is converted into multi-valued (binary or more) data for each pixel by an AD converter (ADC). Is done. This multi-value data is defined as image data of the first format. The data is, for example, general black and white octal data, when all 8 bits are "1", completely white (or black), and when all 8 bits are "0", completely black (or white). , The middle of which is gray, and has a gradation proportional to the numerical value.

1.3 Image Reading Unit Using DF Referring to FIGS.
The operation and the image data of the first format will be described.

The DF unit includes a document stacking unit 5-1 for stacking a plurality of document bundles, a document detection sensor 5-2 for detecting the presence or absence of a document,
Separation strip 5 for separating documents so that transported documents are not double fed
-3, a paper feed roller 5-4 for feeding the original, transport rollers 5-5 and 5-6 for transporting the original, a mylar unit 5-7 for reading the original and transporting the original to a discharge tray; It comprises a discharge roller 5-8 for discharging the original, and a discharge tray 5-9 for discharging the read original.

The operation of the document reading unit by the DF will be described below. First, when a document is set on the document stacking section 5-1, the document detection sensor 5-2 detects the document, and the CPU 1-3c recognizes that a start button (not shown) of the control operation section 1-4 has been pressed. Then, the optical scanning system unit 4
-5 is advanced and fixed from the home position (not shown) to the document reading section position, the linear light source 1-8 is turned on, and the feeding of the document is started by the feed roller 5-4.
The document is conveyed while being separated one by one by a separating piece 5-3 and a conveying roller 5-5, and the original is conveyed to a mylar unit 5-7 which is a document reading unit position by a conveying roller 5-6. Platen glass 4-1 and mylar part 5-7 with light of 1-8
And the reflected light of the original is reflected by the mylar unit 5-7,
The lens array 4- at the same magnification through the glass platen 4-1
3 and CC with document width size mounted in the frame
It is read by D4-4 and converted into an electric signal in the same manner as described in section 1.2 above.

After reading the original, the original is discharged onto a discharge tray 5-9 by a discharge roller 5-8.

1.4 Light Amount Control Unit The configuration, operation, and control of the light amount control circuit 1-7 will be described with reference to FIG.

The light amount control circuit 1-7 includes a controller 1-
3, a constant current circuit 3-1 for supplying a constant current to the LED 1-8 based on the set value, and a PWM control circuit 3-2 for driving the constant current circuit 3-1 according to the setting of the controller 1-3. Be composed.

The light quantity control is performed by the following method.

Current value control: The constant current circuit 3-1 controls the LED 1-8 at a constant current according to the set value from the controller 1-3 to control the light amount.

PWM control: The PWM control circuit 3-2 is controlled by the constant current circuit 3-1 according to the set value from the controller 1-3.
The amount of light is controlled by changing the duty ratio of the energization time for driving.

The light amount control may be performed by only one of the controls.

1.5. Image Forming Unit The image forming unit used in the digital copying machine is a device that forms an image image transmitted by an electric signal on plain paper, thermal paper, or the like by means of electrophotography, heat sensitivity, thermal transfer, ink jet, or the like. In this embodiment, an image output unit of an electrophotographic system using a laser beam exposure system will be described with reference to FIGS.
This will be described with reference to FIG. Reference numeral 7-1 denotes a photosensitive drum on which an optical semiconductor layer whose electrical characteristics are changed by light irradiation is formed, and rotates at a constant speed during an image forming operation. Hereinafter, the image forming operation is performed according to the following steps.

(1) Charging: Charging device (charging roller) 7-2
Thereby, the optical semiconductor layer of the photosensitive drum 7-1 is uniformly charged.

(2) Laser exposure: An image pattern (electrostatic latent image) is irradiated toward the photosensitive drum 7-1 by a laser optical system 7-3 (see FIG. 7, detailed description below).

(3) Development: Toner is adhered to the electrostatic latent image by the developing device 7-4.

(4) Transfer: The image is transferred onto a recording material (hereinafter, referred to as recording paper) by a transfer roller 7-5.

(5) Fixing: The recording paper is heated and pressed by a fixing device 7-6 to fix the toner on the recording paper.
The recording paper is discharged onto the discharge tray 7-7.

(6) Cleaning: The toner remaining on the photosensitive drum 7-1 without being completely transferred onto the recording paper is removed by the blade 7
The toner scraped off by -8 is scraped off and accumulated in the waste toner container 7-9.

The image forming operation is performed according to the above steps. The recording paper or recording material is stacked on a paper feed cassette 7-10 or a manual tray 7-11, and is conveyed to the surface of the photosensitive drum 7-1 by a paper feed roller 7-12.

FIG. 7 shows the laser exposure system 7-3.
A detailed description will be given with reference to FIG. As shown in FIG. 7, the laser writing system includes a laser output unit 7-3a and a mirror 7-.
3b. Inside the laser output unit 7-3a, a laser diode 8-1, which is a laser light source,
A rotating polygon mirror (polygon mirror) 8-2 that rotates at a high speed by a motor at a constant speed, a cylindrical lens 8-3 that corrects laser light, and a focus lens 8-4 that connects the laser light onto the photosensitive drum 7-1 are provided. ing. Laser light source 8-
The laser light emitted from 1 is swung right and left (main scanning direction) by the reflection angle of the polygon mirror which changes with the constant speed rotation, and is focused by the focusing lens 8-4.
1 and is turned back by the mirror 7-3b to form a focused image on the surface of the photosensitive drum 7-1. The laser light oscillated right and left in the main scanning direction is exposed and scanned in a direction (main scanning direction) orthogonal to the direction in which the photosensitive drum 7-1 rotates, and is a line unit of an image signal output from an image processing unit described later. Record. At this time, the laser light is turned on / off according to the transmitted second format image data signal. By repeating main scanning at a predetermined cycle corresponding to the rotation speed and the recording density of the photosensitive drum 7-1, an electrostatic image corresponding to the image read by the image reading unit 1-1 is formed on the surface of the photosensitive drum 7-1. A latent image is formed.

In the laser output unit 7-3a, a beam sensor 8-5 for generating a main scanning synchronization signal (BD signal) is disposed at a position near one end of the photosensitive drum 7-1 where the laser beam is irradiated. Have been. Based on the main scanning synchronization signal, control of image recording start timing in the main scanning direction and generation of a control signal for inputting and outputting an image signal described later are performed.

1.6. The image processing performed by the image processing unit 1-2 will be described.
To convert image data in the first format representing the density of each pixel transmitted from the image reading unit 1-1 (scanner) into image data in the second format and transmit it to the image forming unit (printer) 1-5 Image processing necessary for (1) shading correction, (2) AE processing, (3) scaling processing, (4) filter processing, (5) density processing, and (6) gradation processing.
The process is basically performed according to the steps shown in FIG. Next, each process will be described.

(1) Shading correction: Corrects uneven irradiation of a light source for irradiating a document and variation in sensitivity of a CCD.

(2) AE processing: background removal (removal of background in color original), AI contrast processing (correction to optimal density according to original type).

(3) Magnification processing: Processing for changing the reading density of an image and performing data interpolation using the read image data.

(4) Filter processing: The sharpness of characters in the image is enhanced (edge enhancement) in the filter processing unit, and the noise component in the image is removed (smoothing).

An example of the filtering process will be described. The filter is generally a two-dimensional matrix,

[0052]

(Equation 1)

Is given as follows: Here, A is a coefficient of the matrix, and a, b, c, d, and e are integers, which can be arbitrarily set according to the processing to be executed together, and a value as a filter for performing edge enhancement, smoothing, and the like is set in advance. I have. Also, a plurality of combinations (patterns) of the numerical values can be set.

(5) Density processing: The level of the digital signal is converted from luminance data to density data in accordance with the information of the copy density button or the result of the AE processing and output.

The density conversion process is a process for converting luminance data into predetermined density data. The image data read by the reading unit is processed as quantized luminance data, and the density data corresponding to the luminance data is converted. This is performed using table data for performing the operation. Therefore, it is realized by changing the coefficient for converting the luminance data into the density data, that is, by having a plurality of tables.

(6) Gradation processing: Binarization or multi-value processing is performed according to the recording method of the image forming unit.

The binarization processing is roughly classified into a simple binarization processing method and a binary pseudo halftone processing method (dither method) according to its purpose. The former is to binarize (determine) whether or not to print characters and line drawings in dots for each pixel with a certain threshold value, and to reproduce the resolution information of the original more faithfully. It is an object of the present invention to more faithfully reproduce the gradation information of a halftone image represented by. Various methods have been proposed and implemented as a pseudo halftone processing method, but all of these methods express halftone in a pseudo manner by the number of black (recording) dots per unit area. Here, an error diffusion method will be described as an example. However, the present invention is not limited to this method, and all gradation processing can be applied.

The error diffusion method (Error Diffusi)
On: ED method), a binarization error generated around an arbitrary pixel of interest is weighted by an error filter, and is distributed to the neighboring pixels to be binarized and corrected. Therefore, after error correction, binarization is performed at a fixed threshold.

The feature of this method is that the binarization error is spatially diffused and distributed two-dimensionally, so that it has good tone reproducibility and relatively good resolution reproducibility. Further, the effect of suppressing moiré is large even for a halftone original. This weighting factor,
The binarization threshold can be set arbitrarily, and is set according to the resolution and gradation of the reading unit.

The above is the minimum image processing for configuring the digital copying machine. However, this control block configuration may change its processing order or configuration depending on the type of copying machine (color or black and white), the relationship with other image processing / editing, and the like.

[0061] 2. Control Processing Operation According to the Present Invention A control method of the digital copying machine of the present embodiment will be described with reference to the flowchart of FIG. The controller 1-3 performs control based on the detection result based on the flowchart shown in FIG. FIG. 8 is a flowchart showing the control processing operation according to the present invention. This operation is performed in the ROM
3a based on the program stored in
3c.

First, an outline of the control flow will be described. First, the processing conditions in the light amount control are set for the CPU 1-3 for reading the platen document and reading the DF document, respectively.
The setting is made by the control operation unit 1-4 connected to the terminal c (see step 1, referred to as S1 in the figure, and so on). And
Before performing the image reading operation, read the original with the pressure plate
Whether the original is read by the DF or not is detected based on the output of the pressure plate and the presence / absence detection of the DF original (step 2).
As a means for detecting the presence or absence of a document, the detection means for reading the pressure plate may be a method using a photosensor mounted below the platen glass 4-1 or a linear light source 1-8 prior to the actual reading of the document. And scanning from the leading edge to the trailing edge of the document, and detecting the presence or absence of image light from the document by the CCD 4-4. At the time of DF reading, a photo sensor is used.

These examples of document presence / absence detection do not limit the present invention. Based on the detection result, the processing conditions of the pressure plate reading unit are set in advance when the reading unit type is a pressure plate, and the setting conditions of the DF reading unit are set in the CPU 1-3c when the reading unit type is DF reading. Is R
Read from the table area of OM1-3a (Step 4
Or 3).

The read processing conditions are as follows:
The light source 1-8 is controlled based on the set light amount condition, and a document image is read by the image reading unit 1-1 based on the set light amount condition. And perform an image processing operation.

Next, control in the embodiment using the light amount control method described in 1.4 will be described.

First, the current value control will be described.

A current value corresponding to each light amount condition of the pressure plate reading section and the DF reading section is set by the control operation section 1-4 connected to the CPU 1-3c (step 1). DF
The image signal of the first format in the reading unit is output to a mylar unit 5-
7, the distance from the linear light source 1-8 to the document and the distance from the document to the CCD 4-4 are longer than those of the pressure plate reading unit, so that the light amount of the document image formed on the CCD 4-4 is reduced and the reading is performed. It is expected that the entire original will be dark.

Accordingly, the current value corresponding to the light amount of the DF reading unit is set so that the light amount is larger than the current value of the pressure plate reading unit.

Before the operation of the image reading section, whether the reading section type is a pressure plate or a DF is detected by the above-described method (step 2). Based on the detection result, D
If it is the F reading section format, the DF set in step 1
The current value corresponding to the light amount of the reading unit, or the current value corresponding to the light amount of the pressure plate reading unit for the platen reading unit type is CP
U1-3c reads from the table area of ROM1-3a (step 3 or 4).

The constant current circuit 3-1 is driven and controlled by the read current values to control the LED 1-8, which is a light source, to execute the operation of reading the original image (step 5).

Next, the PWM control will be described.

First, as described above, the duty ratio for determining the lighting time of the light source is set in the pressure plate reading unit and the DF reading unit. The image signal of the first format in the DF reading section is transmitted by the mylar section 5-7 because the distance from the linear light source 1-8 to the document and the distance from the document to the CCD 4-4 are longer than those in the pressure plate reading section. It is expected that the amount of light of the original image formed at -4 will decrease, and that the entire scanned original will be dark.

Therefore, the setting value of the duty ratio of the light amount condition of the DF reading unit is set so that the lighting time of the light source is longer than the setting value of the duty ratio of the pressure plate reading unit, and the light amount is increased ( Step 1).

Before the operation of the image reading section, whether the reading section type is a pressure plate or a DF is detected by the above-mentioned method (step 2). Based on the detection result, D
If it is an F reading unit, the duty ratio of the DF reading unit set in step 1 is used. If it is a pressing plate reading unit, the duty ratio of the pressing plate reading unit is set.
-3a is read from the table area (step 3 or 4).

Then, the PWM control circuit 3-2 is driven and controlled by the read duty ratio, and the light source LE
D1-8 is controlled to execute a document image reading section operation (step 5).

As described above, according to the present embodiment,
When reading an original while pressing it with a pressure plate, in the case of reading an original by automatic original feeding, the distance from the optical system to the original becomes longer by the thickness of a transparent protective member such as Mylar,
In addition, because of the presence of the transparent protective member, the amount of light is attenuated,
By correcting by the controller by an amount corresponding to the amount of attenuation, it is possible to prevent the signal level of the output image from lowering.

Since the present invention relates to an image reading apparatus, it is not limited by the output form of the image output unit. That is, the image output unit is not limited to the image forming apparatus (various printers) as described in the embodiment, but may be any of a display device (various displays) for displaying images and a recording device (various memories) for recording images. It is applicable also in.

Further, the control of the light quantity is not limited to the control of the light source, but may be carried out, for example, by adopting a method of controlling the light quantity by an appropriate means in the middle of the optical path.

[0079]

As described above, according to the present invention,
It is possible to correct the deterioration of the read image data which occurs at the time of automatic document feed, and prevent the signal level of the output image from lowering.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a control system according to an embodiment.

FIG. 2 is a diagram showing a configuration of an image reading unit using a pressure plate.

FIG. 3 is a diagram illustrating a configuration of an image reading unit using a 1: 1 optical system (CS).

FIG. 4 is a diagram showing a configuration of an image reading unit using an automatic document feeder.

FIG. 5 is a block diagram illustrating a configuration of a light amount control unit.

FIG. 6 is a cross-sectional view illustrating a configuration of an image output unit.

FIG. 7 is a diagram showing details of a laser optical system.

FIG. 8 is a flowchart showing the operation of the embodiment.

FIG. 9 is a diagram showing processing in an image processing circuit.

[Explanation of symbols]

 1-7 Light control circuit 1-8 Linear light source 4-1 Original platen glass 4-2 Pressure plate 4-4 Light receiving sensor (CCD) 5-7 Mylar

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H076 AA58 BA07 BA17 BA24 BA36 BA47 BA59 BA63 BA64 BA65 BA87 BA95 BB02 DA03 DA19 DA22 5B047 AA01 BA01 BA02 BB02 BC18 CA19 CB04 CB05 CB11 DB01 5C072 AA01 BA17 CA02 CA04 NA01 EA05 LA04

Claims (6)

[Claims] A detecting means for detecting whether reading is performed by a pressure plate or reading by automatic document feeding; and a light amount controlling means for controlling a light amount for irradiating the document in accordance with a detection result by the detecting means. An image reading apparatus comprising: A transparent document table, a light source for irradiating the document via the document table, and photoelectric conversion means for receiving a document reflected light including document image information, converting the reflected light into an electric signal, and outputting the signal. An image reading apparatus, comprising: a document pressing member, wherein a document image is read by a document reflected light transmitted through the document mounting table in a state where the document is pressed onto the document mounting table by the document pressing member. 1
A document image reading unit, a loading table on which a plurality of documents are loaded, and a transport separation unit that separates and sends out the documents on the loading table one by one and transports the document to a transparent transport member that is in contact with the document loading table. A second document image reading unit for reading a document image by document reflection light transmitted through the document placing table and the transport member while the document is passing through the transparent transport member; A detecting unit for detecting whether the original image reading unit is the first or the second, and a light amount controlling unit for controlling a light amount of the light source according to a detection result of the detecting unit. Image reading device. 3. An image reading apparatus according to claim 1, wherein said light amount control means controls light amount by controlling a current value supplied to said light source. 4. An image reading apparatus according to claim 1, wherein said light amount control means performs light amount control by controlling a duty ratio for determining a lighting time of said light source. 5. An image forming apparatus comprising the image reading device according to claim 1. 6. A detecting step for detecting whether reading is performed by a pressure plate or reading by automatic document feeding, and a light amount controlling step for controlling a light amount for irradiating a document in accordance with a result of the detection in the detecting step. An image reading method, comprising: