JP5533230B2 - Image reading apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an image reading apparatus including a scanner, a copying machine including the image reading apparatus, and an image forming apparatus including a facsimile.

In recent years, an image reading apparatus having a double-sided simultaneous reading mechanism capable of simultaneously reading both sides of a document has been proposed for the purpose of improving the productivity of document reading, protecting the document, and improving silence.
In such an image forming apparatus, conventionally, a CCD (Charge Coupled Device) is used to read the image on the front side of the document, as in the case of the conventional image forming apparatus. There is an apparatus (for example, refer to Patent Documents 1 and 2) in which a contact image sensor (CIS) is used.
Some CISs have an image processing function inside the CIS module.
In such a CIS, correction between lines within the CIS module is required before image processing. However, in order to reduce the cost by reducing the memory for correction between lines, a fixed resolution in the sub-scanning direction (therefore, accordingly) , The scanning speed is also fixed).

As described above, in the case of the CIS in which the resolution is fixed in advance, the CIS cannot change the resolution mechanically by changing the resolution even if the magnification is designated. This mechanical scaling is to change the image data by changing the resolution at the time of detection by the image sensor.
Therefore, the CIS always reads an image of a document with a fixed resolution (equal magnification) regardless of the scaling factor even when scaling is designated.
Then, the subsequent image processing unit and control unit scales the image data read by the CIS to a designated magnification by an electrical scaling process. The electrical scaling process is to scale the read image to a magnification specified by the image process.
For example, it is assumed that the fixed resolution is 600 dpi and the image data is scaled to 50%.
In this case, if the resolution is variable, the original is read at a resolution of 300 dpi, and the original is read at a reading speed twice as high in the sub-scanning direction as compared with the case of reading the original at a resolution of 600 dpi. Can be done.

However, in the CIS with a fixed resolution, it is not possible to read the original at a resolution of 300 dpi and perform mechanical scaling. After the original is read at a resolution of 600 dpi, the resolution is set to 300 dpi by electrical scaling. You have to zoom in.
Further, if the reading means is different between the front surface and the back surface, the S / N characteristics are also different.
The S / N characteristic is a numerical value representing the quality of a signal, with the S / N ratio dB (decibel) indicating the signal-to-noise ratio of the image sensor as a characteristic value. The larger this value, the lower the noise and the higher quality signal can be obtained.
For this reason, when adaptive processing of a read image by image area separation is performed, an output image is affected by a difference in separation performance.

However, in the conventional technique described above, even when the resolution is fixed, the magnification can be changed by an electric scaling process. However, compared with the case where the mechanical scaling is performed, the original is read. There was a problem that the speed was lowered and the productivity was lowered.
In addition, there is a problem in that the output image quality is affected because there is a difference in the S / N characteristics of the images read on the back side and the front side of the document.
The present invention has been made in view of the above points, and an object of the present invention is to improve the output image quality without causing a difference in the S / N characteristics of the images read on the back surface and the front surface of the document.

  In order to achieve the above-described object, the present invention provides a first reading of first image data that is an image of one side of a document at a first resolution corresponding to a predetermined magnification and a predetermined first reading cycle. The image reading means and the light emitted from the light source are accumulated, and the second image data, which is an image of the other side of the original, is read at a second reading period corresponding to the second resolution fixed in advance and the magnification. A second image reading means; an S / N detecting means for detecting an S / N ratio between the first image data read by the first image reading means and the second image data read by the second image reading means; There is provided an image reading apparatus provided with a control means for varying the light accumulation time at the time of image reading of the second image reading means based on the S / N ratio detected by the S / N detection means.

Further, the second image reading means sets the light accumulation time at the time of reading the second image data within a range below the lower limit value of the second reading cycle based on the S / N ratio of the first image data. Means for variably controlling the light source, based on the S / N ratio of the first image data, controlling the lighting of the light source, and variably controlling the light accumulation time within a range not more than the lower limit value of the second reading cycle. Any one of the means may be provided.
Further, the second image reading means reads one line of the image on the other side of the document according to the line synchronization signal input every second reading cycle, and input is started in synchronization with the line synchronization signal. In addition, it is preferable to have means for lighting the light source in accordance with a lighting signal whose input is terminated below the lower limit value.

Further, the second image reading means reads one line of the image on the other side of the document according to the line synchronization signal input every second reading cycle, and input is started in synchronization with the line synchronization signal. In addition, it is preferable to have means for accumulating light emitted from the light source in accordance with a control signal that terminates input below the lower limit.
Further, it is preferable to provide a transport unit that transports the document at a transport speed corresponding to the variable magnification.
Further, it is preferable to provide a scaling unit for electrically scaling the second image data with the scaling factor.

  Further, in the first mode, the first image reading means reads the first image data from one side of the document with the first resolution and the first reading cycle corresponding to the magnification, and in the second mode. The means for reading the first image data from one side of the document at the predetermined first resolution and the first reading period, and the second image reading means in the first mode The second image data is read from the other side of the document at the second reading cycle corresponding to two resolutions and the magnification, and in the second mode, the second resolution and the predetermined second reading cycle are read. Means for reading the second image data from the other side of the document, and the scaling means has means for electrically scaling the first image data read in the second mode with the scaling factor. Have each It may be so.

The first mode may be a productivity mode that prioritizes productivity, and the second mode may be a reusability mode that prioritizes reusability.
Alternatively, the first mode may be a first application mode, and the second mode may be a second application mode.

  Further, in the single-sided reading mode, the first image reading unit reads the first image data from one side of the document at the first resolution and the first reading period corresponding to the magnification, and the double-sided reading mode. The means for reading the first image data from one side of the document at the first resolution and the first reading period determined in advance, and the second image reading means in the double-sided reading mode, the second image reading means. Means for reading the second image data from the other side of the document at two resolutions and a predetermined second reading cycle; and the scaling means for reading the first image data read in the double-sided reading mode. It is preferable to have means for electrically scaling at the scaling factor.

In addition, an image forming apparatus including the image reading apparatus as described above is provided.
Furthermore, the present invention provides an image forming apparatus including the image reading apparatus as described above and a mode input unit that selectively inputs the type of the mode.

  The image reading apparatus and the image forming apparatus according to the present invention can improve the output image quality without causing a difference in the S / N characteristics of the images read on the back surface and the front surface of the document.

FIG. 3 is a block diagram illustrating a functional configuration of an image processing unit and a controller illustrated in FIG. 2. 1 is a diagram illustrating a configuration common to image forming apparatuses according to Embodiments 1 to 7 of the present invention. FIG. 3 is a flowchart showing LED lighting duty adjustment processing in the image forming apparatus shown in FIG. 2. FIG. 3 is a flowchart illustrating a double-sided reading process for a document in the image forming apparatus according to the first exemplary embodiment. FIG. 5 is a timing chart illustrating an example of signals exchanged between the CIS and an input image processing unit when performing the same magnification reading in the processing illustrated in FIG. 4.

FIG. 5 is a timing chart illustrating an example of signals exchanged between the CIS and an input image processing unit when performing variable magnification reading at a variable magnification of 1/2 in the processing illustrated in FIG. 4. FIG. 10 is a flowchart illustrating a double-sided reading process for a document in the image forming apparatus according to the second exemplary embodiment. FIG. 10 is a flowchart illustrating a double-sided reading process for a document in the image forming apparatus according to the third exemplary embodiment. FIG. 10 is a flowchart illustrating document reading processing in the image forming apparatus according to the fourth exemplary embodiment. FIG. 3 is a flowchart showing an electronic shutter duty adjustment process in the image forming apparatus shown in FIG. 2.

FIG. 10 is a flowchart illustrating a double-sided document reading process in the image forming apparatus 100 according to the sixth exemplary embodiment. FIG. 12 is a timing chart illustrating an example of signals exchanged between the CIS and the input image processing unit when performing the normal magnification reading in the processing illustrated in FIG. 11. FIG. 12 is a timing chart illustrating an example of signals exchanged between the CIS and the input image processing unit when performing variable magnification reading at a variable magnification of 1/2 in the processing illustrated in FIG. 11.

Hereinafter, embodiments for carrying out the present invention will be specifically described with reference to the drawings.
The image forming apparatus will be described by taking a multifunction peripheral (MFP) having at least one of a printing function, a copying function, and a facsimile function as an example in addition to a scanner function, but is not limited thereto. It is not a thing. For example, a copying machine or a scanner device may be used.
FIG. 2 is a diagram showing a configuration common to the image forming apparatuses according to Embodiments 1 to 7 of the present invention.
The image forming apparatus 100 is a multifunction peripheral (MFP) having at least one of a printing function, a copying function, and a facsimile function in addition to a copying machine (copying machine), a facsimile machine, a printer having a scanner function, and a scanner function. : Multifunction Peripheral).

The image forming apparatus 100 includes an automatic document feeder (Auto Document Feeder: “ADF”) 101, an image reading apparatus 102, and a main body apparatus 103.
The ADF 101 includes an image reading device 102 at a lower portion thereof, and has a function of reversing the document so that the document is conveyed to the image reading device 102 and the image reading device 102 reads images on both sides of the document. . Such an apparatus capable of reading images on both sides of a document is also referred to as an automatic duplex document feeder (abbreviated as “ARDF”).
The image reading device 102 is a scanner device that reads an image of a document conveyed from the ADF 101 or a document placed on a platen glass, and includes two types of light sources that emit light to the document when reading the image. A function of controlling light emission of two types of light sources when reading an image of a document is provided. The image reading apparatus 102 corresponds to a first image reading unit.

The ADF 101 includes a close-contact, equal-magnification image sensor (abbreviated as “CIS”) 3 that reads the back side of a document. The CIS 3 corresponds to a second image reading unit.
The image reading apparatus 102 includes a slit glass 30 through which an original conveyed by the ADF 101 passes, a contact glass 31 on which an original to be read is placed, a reference white plate 32 for generating shading correction data, an image A first carriage 35 having a lamp 33 and a first mirror 34, which are light sources for irradiating light to a document to be read, a second carriage 38 having a second mirror 36 and a third mirror 37, and a CCD image. A lens unit 39 for reducing and imaging reflected light from an original on the sensor 2 and the CCD image sensor 2 are mounted, and image processing output from the CCD image sensor 2 is subjected to predetermined processing and output to the outside. 1 (also referred to as “signal processing board”) 1 and a controller 2.

The lamp 33 may be of any type as long as it is a light source. For example, an LED (Light Emitting Diode) may be used.
Although not shown, the image reading apparatus 102 includes a drive motor that drives the first carriage 35 and the second carriage 38, a home position sensor that detects the home positions of the first carriage 35 and the second carriage 38, and Each unit such as a document detection sensor for detecting a document is also provided.
The image reading apparatus 102 can read the image on the surface of the document by the “place reading method” or the “sheet through reading method”.
In the placement reading method, the lamp 33 is lit, the first carriage 35 and the second carriage 38 are moved and scanned in the sub-scanning direction with respect to the document by the drive motor, and the image of the surface of the document placed on the contact glass 31 is scanned. Is a reading method.

In the case of this placement reading method, the image reading apparatus 102 reads the reference white plate 32 and acquires the data before reading the image of the document, and generates shading correction data.
The image reading apparatus 102 executes a shading correction process in parallel with scanning (reading operation) of the original reading area.
On the other hand, in the sheet-through reading method, the lamp 33 is lit and the first carriage 35 and the second carriage 38 are stopped, and the document transported by the ADF 101 passes the upper surface of the slit glass 30 when the document is transported. This is a reading method for reading the image.
In the case of this sheet-through reading method, the image reading device 102 reads the reference white plate 32 by moving the first carriage 35 and the second carriage 38 below the reference white plate 32 by a drive motor prior to reading the image of the document. The data is acquired, and shading correction data is generated from the data.

Then, the image reading apparatus 102 returns the first carriage 35 and the second carriage 38 to the sheet-through reading position by the drive motor, and then is parallel to the scanning (reading operation) of the document reading area of the document conveyed by the ADF 101. To execute shading correction processing.
In the case of the sheet-through reading method, the image on the back side of the document can be read using CIS3.
That is, in the sheet-through reading method, it is possible to read only the image on the surface of the document, or it is possible to simultaneously read the images on both sides of the document.
The ADF 101 includes a document tray 40 on which a document is placed, a reference white roller 41 provided at a position facing the CIS 3, a paper discharge tray 42 that discharges a document after image reading, and a document transport mechanism 43. Yes. The document transport mechanism 43 corresponds to a transport unit.

The ADF 101 also includes a drive motor that drives the document transport mechanism 43, although not shown.
When the image reading apparatus 102 reads an image of a document by a sheet-through reading method, the document transport mechanism 43 scans the document placed on the document tray 40 with the upper part of the slit glass 30 and the CIS 3 and the reference white roller 41. The paper is conveyed to the paper discharge tray 42 through the facing position.
The CIS 3 includes an LED as the light source 44. As this light source 44, you may use types of light sources other than LED. Further, although not shown, each part such as a lens array and a sensor element is also provided.
When simultaneously reading images on both sides of a document by the sheet-through reading method, the CIS 3 turns on the light source 44, conveys it by the ADF 101, irradiates the back surface of the document that passes under the CIS 3, and reflects the reflected light from the document to the lens. The light is condensed on the sensor element by the array and converted into image data. Thus, the CIS 3 reads the image on the back side of the document conveyed by the ADF 101.

The CIS 3 reads the reference white roller 41 prior to reading the document image, acquires the data, and generates shading correction data based on the data.
The CIS 3 executes a shading correction process in parallel with the scanning (reading operation) of the document reading area.
In this embodiment, an example will be described in which the image reading device 102 reads an image on the front side of a document and the CIS 3 reads an image on the back side of the document. However, the image reading device 102 reads an image on the back side of the document, and the CIS 3 An image on the surface of the document may be read.
Further, the image reading apparatus 102 does not have to have all the above-described configurations as essential configurations, and may be configured such that some of them are omitted.

Next, the main body device 103 of the image forming apparatus 100 prints color image data or monochrome image data read by the image reading device 102 on a sheet.
In the case where the image forming apparatus 100 is a multi-function peripheral, image data received from the outside via a communication function or image data received via the Internet can be printed.
Further, when the image forming apparatus 100 is a multifunction peripheral, the image data read by the image reading apparatus 102 can be sent to an external facsimile apparatus or information processing apparatus by facsimile transmission or communication via the Internet.
The main body device 103 includes a controller 4 that is a control unit that controls printing based on image data read by the image reading device 102.

Further, in response to an instruction based on the image data from the controller 4, electrostatic latent images are respectively formed on the surfaces of four photoconductors (also referred to as “photoconductor drums” in the case of drum-like photoconductors) 51y to 51k. An exposure apparatus 104 including an exposure unit including a plurality of mirrors and lenses to be formed is provided. Each of the photoconductors 51y to 51k is an image carrier on which toner images of yellow (Y), magenta (M), cyan (C), and black (K) are written.
Around each of the photoconductors 51y to 51k, there is a charging device 52y to 52k for charging the surface of each of the photoconductors 51y to 51k, and an electrostatic latent formed on the surface of each of the photoconductors 51y to 51k. Each developing device 53 y to 53 k that visualizes the image with toner of each color and a toner image (visible image) formed on each of the photoreceptors 51 y to 51 k are superimposed on the intermediate transfer belt 50. Each of the cleaning devices 54y to 54k for collecting the toner remaining on the photoconductors 51y to 51k after the transfer is provided.

The intermediate transfer belt 50 transfers a single-color toner image written on any one of the photoreceptors 51y to 51k, or superimposes a toner image of each color written on each of the photoreceptors 51y to 51k. It is a transcript. The intermediate transfer belt 50 corresponds to a transfer unit.
In the case of color printing, the image forming apparatus 100 transfers the toner images written on the photoconductors 51y to 51k to be superimposed on the intermediate transfer belt 50, thereby forming a color toner image. In the case of monochrome printing, the black toner image written on the photoreceptor 56k is transferred to the intermediate transfer belt 50 to form a monochrome toner image.
On the other hand, the sheet (transfer sheet) P conveyed from the sheet feeding tray 56 by the conveying unit 57 is temporarily stopped at the registration roller unit 58, and is re-fed in synchronization with the rotation of the intermediate transfer belt 50. The toner image on the intermediate transfer belt 50 is transferred onto the paper P by the unit 59. The paper P on which the toner image has been transferred is subjected to fixing processing by the fixing device 60, and finally discharged to the paper discharge storage portion 62 by the paper discharge means 61.

FIG. 1 is a block diagram showing a functional configuration of the image processing unit 1 and the controller 4 shown in FIG.
The image processing unit 1 of the image reading apparatus 102 includes a CPU (Central Processing Unit) 10, a CPU memory 11, data conversion units 12 and 13, a memory 14, a memory control unit 15, an input image processing unit 16, An S / N detection unit 17 and a bus connecting these units are provided. The S / N detection unit 17 corresponds to an S / N detection unit, and the input image processing unit 16 corresponds to a scaling unit.
The CCD image sensor 2 converts reflected light of the light irradiated on the surface of the document into image data (image signal), and converts the image data on the surface of the document into analog-digital (A / D) conversion processing, signal amplification processing, Then, a predetermined process such as a shading process is performed and output to the data conversion unit 12.

On the other hand, the CIS 3 converts the reflected light of the light irradiated on the back side of the document into image data (image signal), and converts the image data on the back side of the document to A / D conversion processing, signal amplification processing, shading processing, and the like. Predetermined processing is performed and output to the data converter 13.
The data conversion unit 12 converts the format of the image data input from the CCD image sensor 2 into a format compatible with the input image processing unit 16 and outputs the format to the memory control unit 15.
The data conversion unit 13 converts the format of the image data input from the CIS 3 into a format compatible with the input image processing unit 16 and outputs it to the memory control unit 15.
The memory control unit 15 temporarily writes the image data input from the data conversion unit 12 and the data conversion unit 13 to the memory 14, reads the written image data from the memory 14, and inputs the input image processing unit 16 and the S / N detection unit. 17 to transfer.

The input image processing unit 16 performs image processing due to input characteristics such as γ correction and MTF (Modulation Transfer Function) correction, scaling processing, and the like on each image data transferred from the memory control unit 15. To the controller 4. Further, the input image processing unit 16 outputs the image data transferred from the controller 4 to the output image processing unit 5.
The S / N detection unit 17 detects S / N characteristics (noise) between the image data on the front side of the document and the image data on the back side of the document.
The S / N detection unit 17 is shown as an example in FIG. 1 and may be located anywhere in the data path from the CCD image sensor 2 and the CIS 3 to the image processing unit 1.

Here, it is assumed that the image reading apparatus 102 has a variable resolution.
For this reason, the CPU 10 controls a drive motor (not shown) to transport the document to the document transport mechanism 43 at a transport speed corresponding to the variable magnification, and the image reading device 102 changes the resolution to the variable magnification. By scanning the surface of the original and reading the image data, the magnification can be changed mechanically.
For example, when 50% zooming is designated, the CPU 10 causes the document transport mechanism 43 to transport the document at twice the transport speed in the case of the same magnification scanning, and the image reading apparatus 102 reads the resolution at the same magnification. When the image data is read by scanning the surface of the original in half of the case, the magnification can be mechanically changed by 50%.
The CIS 3 performs line-to-line correction before performing the image processing as described above. In order to reduce the cost by reducing the memory for line-to-line correction, the CIS 3 has a fixed resolution (in the sub-scanning direction of the document). It is assumed that the scanning is performed at a scanning speed.

Therefore, when reading both sides of a document by the sheet-through reading method, the CIS 3 always reads image data on the back side of the document with a fixed resolution (equal magnification).
Even with this reading method, the magnification can be electrically reduced (reduced), but the reading speed of the document is lowered and the productivity is lowered as compared with the case where mechanical magnification is performed.
Therefore, in the first embodiment, the CPU 10 controls a drive motor (not shown) to transport the document to the document transport mechanism 43 at a transport speed corresponding to the variable magnification, and the CIS 3 reads the read line cycle corresponding to the variable magnification. Then, the back side of the document is scanned to read the image data, and the input image processing unit 16 electrically scales the read image data.
For example, when 50% scaling is designated, the CPU 10 causes the document transport mechanism 43 to transport the document at twice the transport speed in the case of the same magnification scanning, and the CIS 3 performs the scanning line cycle of the same magnification. The input image processing unit 16 electrically scales the read image data to 50%.

In this way, even when the resolution is fixed and electrical scaling is performed, it is possible to prevent a decrease in document reading speed and a decrease in productivity, and the same production as when mechanical scaling is performed. Can keep sex.
However, simply shortening the reading line period in accordance with the variable magnification (reduction ratio) also shortens the light accumulation time of the light emitted from the light source 44 of the CIS3. For example, reading of a decrease in S / N characteristics, etc. This causes a change in characteristics and causes deterioration (change) in image quality.
Therefore, in the first embodiment, the lighting of the light source 44 of the CIS 3 is controlled to control the light accumulation time to a constant value that is equal to or less than the lower limit value of the reading line cycle.
In this way, even if the reading line cycle is changed according to the magnification, the light accumulation time can be kept constant, and changes in reading characteristics and image quality deterioration can be prevented.

The output image processing unit 5 of the main body device 103 performs image processing according to output characteristics such as filter processing and color space conversion processing on the image data input from the input image processing unit 16 and outputs the processed image data to the LD driver 6. .
The LD driver 6 of the main body device 103 drives the light emission of the LD, which is a light source (not shown) of the exposure device 104, in accordance with the image data input from the output image processing unit 5, and the laser light is sent to each of the photoconductors 51y to 51k. Irradiate.
An electrostatic latent image is formed on each of the photoconductors 51y to 51k, the image is transferred to a sheet through transfer and fixing, and a print sheet is output.
The CPU 10 controls the other parts of the image processing unit 1, the entire image reading apparatus 102 and the ADF 101, and the CIS 3 of the ADF 101 using the CPU memory 11 as a work area.

The CPU 10 also communicates with the CPU 20 of the controller 4 and controls to transmit and receive various data.
Note that the CPU 10 may perform a scaling process performed by the input image processing unit 15 in hardware, in software.
The controller 4 of the main body device 103 includes a CPU 20, an image controller 21 connected to the CPU 20, and an input / output (I / O) controller 22 connected to the CPU 20.
The image controller 21 stores the image data transferred from the input image processing unit 16 in a storage device such as a hard disk drive (HDD) (not shown). The image data stored in the storage device is read out and transferred to the image processing unit 1.

The I / O controller 22 is connected to the operation display unit 7 (not shown in FIG. 2) of the image forming apparatus 100, and outputs operation information input from the operation display unit 7 to the CPU 20 and is output from the CPU 20. The displayed display information is output to the operation display unit 7.
The operation display unit 7 inputs various kinds of operation information including an input instruction to start reading a document and an input of a reading mode, and displays various kinds of display information. The operation display unit 7 corresponds to mode input means.
The CPU 20 controls each unit of the controller 4, communicates with the CPU 10 of the image processing unit 1, transmits operation information input from the operation display unit 7 via the I / O controller 22 to the CPU 10, and receives information from the CPU 10. Receive.

[Example 1]
Next, the image forming apparatus 100 according to the first exemplary embodiment will be described.
In the image forming apparatus 100 of the first embodiment, the light source 44 of the CIS 3 is an LED, and the light accumulation time is controlled by controlling the lighting of the LED.
First, the CIS3 LED lighting duty adjustment process performed before normal use in the image forming apparatus 100 according to the first embodiment will be described.
FIG. 3 is a flowchart showing the LED lighting duty adjustment processing in the image forming apparatus 100.
The process shown in FIG. 3 is for the case where the light source 44 is an LED, and an input reference document is placed on the document tray 40 of the ADF 101, and the input image processing unit is based on the operation information input from the operation display unit 7. 16 is executed when an adjustment start is input from the operation display unit 7 in a state where the LED lighting duty adjustment mode of the light source 44 is set in the CPU 10.

Further, as an operation specification, when the range of mechanical magnification is 50 to 100% (resolution: equivalent to 300 to 600 dpi) and the image reading apparatus 102 performs the same magnification reading, the reading linear velocity is 300 mm / sec, An example in which the front side scanning line period is 141 μsec, the front side scanning resolution is 600 dpi, the back side scanning line period is 141 μsec, and the back side scanning resolution is 600 dpi is described, but the present invention is not limited to this example.
Further, the back side reading CIS3 is a 1 × magnification sensor, and has a higher S / N characteristic than the reduction optical system on the front surface, and can obtain an S / N characteristic equivalent to that on the front surface when the light accumulation time on the back surface is less than the lower limit setting. It shall be possible.
When the CPU 10 accepts an adjustment start instruction input from the operation display unit 7 via the CPU 20 in step (indicated by “S” in the drawing) 1, the CPU 10 changes the LED lighting duty (back lamp lighting basic duty) of the light source 44. Lower limit value (adjustment reference value) of back side scanning line cycle (scanning line cycle of the back side of the document): 70 μsec, and proceeds to step 2.

In step 2, the reading linear velocity of the front and back surfaces is set to 300 mm / sec, and the process proceeds to step 3.
In step 3, the reading line period on the front surface and the back surface is set to 141 μsec, and the process proceeds to step 4. In step 4, the shading correction is set to OFF, and the process proceeds to step 5.
In step 5, the lamp 33 and the light source 44 are turned on, and the process proceeds to step 6.
In step 6, the reference document set on the document tray 40 of the ADF 101 is conveyed, and reading of the images on the front and back surfaces of the reference document is started to acquire the image data on the front surface and the image data on the back surface. move on.
In step 7, the S / N detector 17 detects S / N characteristics (ratio of signal level and noise component (standard deviation, peak / bottom)) from the image data on the front surface and the image data on the back surface, respectively. Proceed to step 8.

It is assumed that the density of the reference document is set to the upper limit of the density range that can be read by the document reading apparatus 102.
In step 8, the reading of the front and back images of the reference document is finished, and the process proceeds to step 9. In step 9, the lamp 33 and the light source 44 are turned off, and the process proceeds to step 10.
In step 10, LED lighting Duty: Tadi is calculated so that the S / N characteristic detected for the image on the front side of the reference original and the S / N characteristic detected for the image on the back side of the reference original are equal to each other. move on.
For the processing of Step 10, simply, the LED lighting duty is calculated so that the sensor output level becomes a constant value (the sensor output target value on the back surface converted from the sensor output level on the front surface). The calculated value may be stored in the memory.

In this case, when the LED lighting duty is 70 μsec and the sensor output level is Vini, if the target output level is Vtgt, the LED lighting duty is calculated as 70 × Vtgt / Viniμsec.
In step 11, LED lighting Duty: Tadi in which the S / N characteristics of the front and back images are equal is stored in the memory, and the process proceeds to step 12.
In step 12, the shading correction is set to ON, and this adjustment process is terminated.
In the above-described adjustment process, the reference document is read. However, if a reference white plate for shading correction is used instead of the reference document, it is necessary to prepare a reference document for adjustment. In addition, even in the user's usage environment, adjustments can be made during the initialization operation when the power is turned on.

Next, processing for reading both sides of a normal document in the image forming apparatus 100 according to the first embodiment will be described.
FIG. 4 is a flowchart illustrating document double-sided reading processing in the image forming apparatus 100 according to the first exemplary embodiment.
In the double-sided reading process of the original, the operation display unit is set in a state where the original is placed on the original tray 140 of the ADF 101 and the double-sided reading mode is set by the input image processing unit 16 based on an input from the operation display unit 7. 7 starts when a document reading start is input.
Further, when the range of the magnification ratio for mechanical scaling is 50 to 100% (resolution: equivalent to 300 to 600 dpi) and the image reading apparatus 102 performs the same magnification reading, the scanning linear velocity of the original is 300 mm / sec. An example in which the reading line cycle on the front side of the document is 141 μsec, the reading resolution on the front side of the document is 600 dpi, the reading line cycle on the back side of the document is 141 μsec, and the reading resolution on the back side of the document is 600 dpi will be described. It is not limited to.

First, when the CPU 10 receives a reading start input of a document from the operation display unit 7 via the CPU 20, in step 21 (indicated by “S” in the drawing) 21, the LED lighting duty: Tadi (μsec) (stored in the memory). Set the LED lighting duty of the light source (in this case, the LED) of the CIS 3 to a value equal to or less than the lower limit value of the back side scanning line cycle.
For example, when the lower limit of the back side scanning line cycle (scanning line cycle of the back side of the document) is 70.5 (= 141 × (1/2)) μsec, the CPU 10 turns on the LED lighting duty of the LED that is the light source 44 of the CIS3. Is set to Tadi (μsec) adjusted to 70 μsec or less.
In step 22, the CPU 10 sets the surface reading line period (the reading line period on the surface of the document, corresponding to the “first reading period”) to 141 μsec, and proceeds to step 23.
In step 23, the CPU 10 determines whether or not a scaling input for inputting a scaling ratio is performed from the operation display unit 7 before inputting the reading start of the document. Step) Proceed to Step 24, and if zooming input is not performed (in the case of N), proceed to Step 31.

In step 24, the CPU 10 sets a reading linear velocity (corresponding to the conveyance speed): 300 / magnification / magnification mm / sec according to the magnification / magnification input from the operation display unit 7 and received via the CPU 20.
In other words, the CPU 10 sets a reading linear speed: 300 / magnification / magnification mm / sec, which is a speed obtained by dividing 300 mm / sec, which is a reading linear speed when carrying out equal magnification reading, by a magnification.
For example, when the variable magnification is 1/2 (50%), the CPU 10 sets the reading linear velocity to 600 (= 300 / (1/2)) mm / sec.
Here, in this processing example, since the variable magnification range is 50 to 100%, the reading linear velocity is set in the range of 300 to 600 mm / sec.
Then, the process proceeds to Step 25.

In step 25, the CPU 10 receives the back side scanning line period (corresponding to the scanning line on the back side of the document, the second scanning period) according to the scaling factor input from the operation display unit 7 and received through the CPU 20. Set magnification μsec.
That is, the CPU 10 sets a back side scanning line cycle of 141 × variable magnification μsec, which is obtained by multiplying 141 μsec, which is the back side scanning line cycle in the case of performing equal magnification reading, by a variable magnification.
For example, when the variable magnification is 1/2 (50%), the CPU 10 sets the back surface scanning line cycle to 70.5 (= 141 × (1/2)) μsec.
Here, in this processing example, since the variable magnification range is 50 to 100%, the back side scanning line cycle is set in the range of 70.5 to 141 μsec, and the lower limit value of the back side scanning line cycle is 70.5 μsec. It becomes.
Then, the process proceeds to Step 26.

In step 26, the CPU 10 determines the surface reading resolution (corresponding to the reading resolution of the surface of the original document, the first resolution) according to the scaling factor input from the operation display unit 8 and received via the CPU 20: 600 × magnification scaling factor dpi. Set.
That is, the CPU 10 sets the surface reading resolution: 600 × the scaling factor dpi by a resolution obtained by multiplying the surface reading resolution of 600 dpi, which is the same magnification reading, by the scaling factor.
For example, when the scaling factor is 1/2 (50%), the CPU 10 sets the surface reading resolution to 300 (= 600 × (1/2)) dpi.
Here, in this processing example, since the variable magnification range is 50 to 100%, the surface reading resolution is set in the range of 300 to 600 dpi.
The back side scanning resolution (corresponding to the second resolution) is fixed at 600 dpi.
Then, the process proceeds to step 27.

On the other hand, if it is determined in step 23 that no zooming input is made from the operation display unit 7 before the reading start input (in the case of N), in step 31, the CPU 10 reads the linear drawing speed when performing the normal magnification reading. Is set to 300 mm / sec as the reading linear velocity, and the process proceeds to Step 32.
In step 32, the CPU 10 sets 141 μsec, which is the back surface reading line cycle when performing the same magnification reading, to the back surface reading line cycle, and proceeds to step 33.
In step 33, the CPU 10 sets the surface reading resolution of 600 dpi, which is the surface reading resolution when performing the normal magnification reading, to the surface reading resolution.
The back side scanning resolution is fixed at 600 dpi.
Then, the process proceeds to step 27.
When the setting of various parameters is completed in each process described above and the CPU 10 starts controlling the drive motor, in step 27, the document transport mechanism 43 starts transporting the document at the reading linear speed set by the CPU 10, and step Proceed to 28.

  In step 28, the CPU 10 starts reading the document, and is conveyed by the document conveying mechanism 43 by the CCD image sensor 2 of the image reading apparatus 102 according to various parameters including the surface reading line period and the surface reading resolution set by the CPU 10. Read the image data on the front side of the original document, and read the image data on the back side of the original document conveyed by the original document conveyance mechanism 43 according to various parameters including the LED lighting duty set by the CPU 10 and the back surface reading line cycle. Proceed to step 29.

FIG. 5 is a timing chart showing an example of signals exchanged between the CIS 3 and the input image processing unit 16 in the case of performing the same magnification reading in the processing shown in FIG.
In the example shown in FIG. 5, the CIS 3 is based on the pixel clock signal VCLK shown in FIG. 5A, and as shown in FIG. In the figure, an arrow A in the figure of the line synchronization signal XLSYNC is generated and output to the input image processing unit 16.
Further, as shown in FIG. 5C, the CIS 3 starts generating the lamp lighting signal LED_ON indicating the lighting of the LED as the light source 44 in synchronization with the line synchronization signal XLSYN, and is set by the LED lighting duty. During Tadi (μsec), the data is output to the input image processing unit 16.

Further, as shown in FIG. 5D, the CIS 3 outputs the image signal ViDEO_DATA to the input image processing unit 16 within the back surface scanning line cycle.
That is, in the example shown in FIG. 5, the CIS 3 starts reading image data for one line on the back side of the document every 141 μsec, and lights the LED of the light source 44 for a period of LED lighting Duty: Tadi (μsec). .
The CIS 3 reads the image data for one line on the back side of the document within the period of 141 μsec (effective image data in the figure) and outputs it to the input image processing unit 16.

FIG. 6 is a timing chart illustrating an example of signals exchanged between the CIS 3 and the input image processing unit 16 when performing variable magnification reading at a variable magnification of 1/2.
In the example shown in FIG. 6, the CIS 3 is based on the pixel clock signal VCLK shown in FIG. 6A, and as shown in FIG. An arrow B in the figure of the line synchronization signal XLSYNC is generated every 5 μsec and output to the input image processing unit 16.
Further, as shown in FIG. 6C, the CIS 3 starts generating the lamp lighting signal LED_ON indicating the lighting of the LED as the light source 44 in synchronization with the line synchronization signal XLSYN, and is set by the LED lighting duty. During Tadi (μsec), the data is output to the input image processing unit 16.

Further, as shown in FIG. 6D, the CIS 3 outputs the image signal ViDEO_DATA to the input image processing unit 16 within the back surface scanning line cycle.
The pixel clock frequency is a frequency at which effective image data can be transferred even when the back side scanning line cycle is changed according to the scaling factor, and the back side scanning line cycle is changed according to the scaling factor. It is possible.
That is, in the example shown in FIG. 6, the CIS 3 starts reading image data for one line on the back side of the document every 70.5 μsec, and turns on the LED of the light source 44 for a period of LED lighting Duty: Tadj (μsec). Light up.

Then, the CIS 3 reads the image data for one line on the back side of the document (effective image data in the drawing) and outputs it to the input image processing unit 16 within a period of 70.5 μsec.
In the case of the example shown in FIG. 7, the image data for one line on the surface of the document read by the image reading device 102 is mechanically scaled to 50% (resolution: 300 dpi) in the sub-scanning direction. Although being performed, the image data for one line on the back side of the document read by the CIS 3 is not scaled.
Therefore, the input image processing unit 16 is electrically scaled to 50% (resolution: 300 dpi) in the sub-scanning direction.

Next, returning to FIG. 4, in step 29, the CPU 10 of the image reading apparatus 102 finishes reading the image data for all the lines on the front side of the document and reading the image data for all the lines on the back side of the document. The reading of the original is finished, and the process proceeds to Step 30.
In step 30, the CPU 10 ends the control of the drive motor, ends the document transport by the document transport mechanism 43, and ends the double-sided reading process.
As described above, in the image forming apparatus according to the first embodiment, even when the resolution is fixed, the reading line speed is increased according to the reduction rate and the reading line cycle is shortened according to the reduction rate. Since the magnification is electrically changed, it is possible to prevent the reading speed of the document from being lowered and the productivity from being lowered, and to maintain the same productivity as the case of performing the mechanical magnification.

Further, since the LED lighting duty of the LED of the light source 44 is controlled to be equal to or lower than the lower limit value of the reading line cycle, the light accumulation time can be kept constant even if the reading line cycle is changed according to the variable magnification. It is possible to prevent a change in characteristics and a deterioration in image quality.
Furthermore, since the S / N characteristics of the front and back surfaces are adjusted equally, the image quality can be stabilized.
It should be noted that the variable range of the LED lighting duty of the LED of the light source 44 is designed such that an illumination system having an illuminance necessary to satisfy the S / N characteristic that is the reading performance of the image reading apparatus 102 is designed. .

[Example 2]
Next, the image forming apparatus 100 according to the second embodiment will be described.
In the image forming apparatus 100 of the first embodiment, the example in which the reading of the front side of the document is mechanically scaled and the reading of the back side of the document is electrically scaled has been described.
In the image forming apparatus 100 according to the second exemplary embodiment, the scaling process according to the above-described mode and the both sides of the document are electrically scaled according to whether the productivity of image data is prioritized or the reusability is prioritized. One of the processes to be performed can be selected.
In the following description, the description of parts common to the first embodiment will be omitted, and only differences from the first embodiment will be described in detail.

FIG. 7 is a flowchart illustrating a double-sided document reading process in the image forming apparatus according to the second embodiment.
First, steps (indicated by “S” in the figure) 41 and 42 are the same as the processes in steps 21 and 22 in FIG.
In step 43, the CPU 10 determines whether or not a zooming input for inputting a zooming ratio is performed from the operation display unit 7 before inputting reading of a document, and if a zooming input is performed (Y Step) Proceed to Step 44, and if zooming input is not performed (in the case of N), proceed to Step 52.
In step 44, it is determined whether or not an input of the productivity mode (first mode) giving priority to the productivity of the image data is performed from the operation display unit 7 before inputting the reading start of the document. If YES is selected (in the case of Y), the process proceeds to step 45, and if the productivity mode is not input (the reusability mode (second mode) giving priority to the reusability of the image data is input). If yes (N), go to step 52.

Hereinafter, the processing in steps 45 to 51 when the productivity mode is input is the same as the processing in steps 24 to 30 in FIG. 4, and the reusability mode is input. The processing of steps 52 to 54 and steps 48 to 51 is the same as steps 31 to 33 and steps 27 to 30 of FIG.
When the reusability mode is input to the image data read by the above processing, the input image processing unit 16 reads the image data of the surface of the original read by the CCD image sensor 2 and the CIS 3. The image data on the back side of the original is transferred to the image controller 21 and stored in a storage device such as an HDD.

The input image processing unit 16 receives the transfer of the front and back image data stored in the storage device from the image controller 21 and performs electrical scaling.
That is, in the reusability mode, even when scaling is performed, both the front and back sides of the document are scanned at the same magnification, and after the image data read at the same magnification is stored, the input image processing unit 16 Electrical scaling to the scaling factor specified by is performed.
As described above, in the image forming apparatus 100 according to the second embodiment, in the reusability mode, even when scaling is performed, the image data read at the same magnification is stored. Can be scaled at a scaling factor different from that specified at the time of reading, and can be output as a copy image or transmitted by FAX, thereby enhancing the reusability of image data.

Example 3
Next, the image forming apparatus 100 of Example 3 will be described.
In the image forming apparatus 100 according to the first and second embodiments, the example in which the front surface of the document is mechanically scaled and the back surface of the document is electrically scaled has been described.
In the image forming apparatus 100 according to the third exemplary embodiment, a scanner application mode (first mode and first application mode) for reading with a scanner application, or a copy application mode (second mode and second application mode) for reading with a copy application. In accordance with this, it is possible to select either the process of performing scaling in the above-described manner or the process of electrically scaling both sides of the document.
In the following description, the description of parts common to the first and second embodiments will be omitted, and only the differences from the first and second embodiments will be described in detail.

FIG. 8 is a flowchart illustrating a double-sided document reading process in the image forming apparatus according to the third embodiment.
First, steps (indicated by “S” in the figure) 61 and 62 are the same as the processes in steps 21 and 22 (steps 41 and 42 in FIG. 7) in FIG.
In step 63, the CPU 10 determines whether or not a zooming input for inputting a zooming ratio is performed from the operation display unit 7 before inputting reading of the original, and if the zooming input is performed (Y Step) Proceed to Step 64, and if zooming input is not performed (in the case of N), proceed to Step 72.
In step 64, it is determined whether or not the scanner application mode has been input from the operation display unit 7 before the reading start input of the document. If the scanner application mode has been input (in the case of Y), step 64 is performed. If the scanner application mode has not been entered (if the copy application mode has been entered, N), the process proceeds to step 72.

Hereinafter, the processes in steps 65 to 71 when the scanner application mode is input are the same as the processes in steps 24 to 30 in FIG. 4 (steps 45 to 51 in FIG. 7). The processes in steps 72 to 74 and steps 68 to 71 when input is performed are the same as steps 31 to 33 and steps 27 to 30 in FIG. 4 (steps 52 to 54 and steps 48 to 51 in FIG. 7), respectively. Therefore, the description thereof is omitted.
When the copy application mode input is performed on the image data read by the above processing, the input image processing unit 16 reads the image data of the surface of the document read by the CCD image sensor 2 and the CIS 3. The image data on the back side of the original is transferred to the image controller 21 and stored in a storage device such as an HDD.
Then, the input image processing unit 16 receives the transfer of the front and back image data stored in the storage device from the image controller 21, performs electrical scaling, and outputs it to the output image processing unit 5 to copy the image. As output.

That is, in the copy application mode, even when scaling is performed, both the front and back sides of the document are scanned at the same magnification, and after the image data read at the same magnification is stored, the input image processing unit 16 Electrical scaling to the designated scaling ratio is performed and a copy image is output.
As described above, in the image forming apparatus 100 according to the third embodiment, the productivity of image data can be prioritized in the scanner application mode, and the reusability of image data can be prioritized in the copy application mode.
In the above-described processing, an example in which image data productivity is given priority in the scanner application mode and image data reusability is given priority in the copy application mode has been described. The relationship between each application mode and what has priority Is not limited to this.
For example, priority may be given to image data reusability in the scanner application mode, and image data productivity may be given priority in the copy application mode. You may make it input from the operation display part 7 whether to do.

Example 4
Next, the image forming apparatus 100 according to the fourth embodiment will be described.
In the image forming apparatus 100 according to the first to third embodiments, the example in which the front surface of the document is mechanically scaled and the back surface of the document is electrically scaled has been described.
In the image forming apparatus 100 according to the fourth embodiment, in the case of single-sided scanning, the surface of the document is mechanically scaled, and in the case of double-sided scanning, the process of electrically scaling both sides of the document, Any one of the processing of mechanically and electrically scaling the front surface and electrically scaling the back surface of the document can be selected.
In the following description, the description of parts common to the first to third embodiments will be omitted, and only differences from the first to third embodiments will be described in detail.
FIG. 9 is a flowchart illustrating document reading processing in the image forming apparatus according to the fourth embodiment.

The document reading process is started by inputting a document reading start after a document is placed on the document tray 140 of the ADF 101 and a variable magnification is input from the operation display unit 7.
The range of mechanical scaling is resolution: 400 to 600 dpi, and scaling of the surface of the original to resolution: 300 to 400 dpi is performed by using both mechanical scaling and electrical scaling. And
First, when the CPU 10 receives a reading start input of the document from the operation display unit 7 via the CPU 20, in step 81 (indicated by “S” in the figure) 81, the LED lighting duty: Tadi (μsec) (stored in the memory). Set the LED lighting duty of the light source (in this case, the LED) of the CIS 3 to a value equal to or lower than the lower limit value of the back side scanning line cycle.
For example, when the lower limit of the back side scanning line cycle (scanning line cycle of the back side of the document) is 94 (= 141 × (2/3)) μsec, the CPU 10 sets the LED lighting duty of the LED, which is the light source 44 of CIS3, to 93 μsec. Set to Tadi adjusted below.

In step 82, the CPU 10 sets the surface reading line period (the reading line period on the surface of the document, corresponding to the “first reading period”) to 141 μsec, and proceeds to step 83.
In step 83, the CPU 10 determines whether or not the double-sided reading mode is input from the operation display unit 7 before inputting the reading start of the original. If the double-sided reading mode is not input (single-sided reading mode). Is input (in the case of N), the process proceeds to step 92. If the input of the double-sided reading mode is input (in the case of Y), the process proceeds to step 84.
In step 92, the CPU 10 accepts the variable magnification input from the operation display unit 7 via the CPU 20, and sets the reading linear speed: 300 / variable magnification mm / sec according to the variable magnification.
In other words, the CPU 10 sets a reading linear speed: 300 / magnification / magnification mm / sec, which is a speed obtained by dividing 300 mm / sec, which is a reading linear speed when carrying out equal magnification reading, by a magnification.
Then, the process proceeds to Step 93.

In step 93, the CPU 10 receives the magnification ratio input from the operation display unit 7 via the CPU 20, and sets the surface reading resolution: 600 × magnification ratio dpi according to the magnification ratio.
That is, the CPU 10 sets surface reading resolution: 600 × magnification magnification dpi, which is a resolution obtained by multiplying 600 dpi, which is the surface reading resolution in the case of performing the same magnification reading, by the magnification.
Then, the process proceeds to Step 88.
On the other hand, in step 84, the CPU 10 determines whether or not the zooming range indicated by the received zooming factor is within the range of resolution: 300 to 400 dpi. If the resolution is within the range of 300 to 400 dpi (Y ), The process proceeds to step 85, and if the resolution is not within the range of 300 to 400 dpi (in the case of N), the process proceeds to step 94.
In step 85, the CPU 10 sets the reading linear velocity to 450 (= 300 / (2/3)) mm / sec, and proceeds to step 86.

In step 86, the CPU 10 sets the back side scanning line cycle to 94 (= 141 × (2/3)) μsec.
In this processing example, since the range of mechanical magnification is resolution: 400 to 600 dpi, the back side scanning line cycle is in the range of 94 to 141 μsec, and the lower limit value of the back side scanning line cycle is 94 μsec.
Then, the process proceeds to step 87.
In step 87, the CPU 10 sets the surface reading resolution to 400 (= 600 × (2/3)) dpi.
Also, the back side scanning resolution is fixed at 600 dpi.
Then, the process proceeds to Step 88.

If the double-sided reading mode is input before the reading start input and the magnification range indicated by the magnification ratio is outside the range of resolution: 300 to 400 dpi, in step 94, the CPU 10 performs the case where the same magnification reading is performed. The reading linear velocity of 300 mm / sec is set as the reading linear velocity, and the process proceeds to step 95.
In step 95, the CPU 10 sets 141 μsec, which is the back surface reading line cycle when performing the same magnification reading, to the back surface reading line cycle, and proceeds to step 96.
In step 96, the CPU 10 sets the surface reading resolution of 600 dpi, which is the surface reading resolution when performing the normal magnification reading, to the surface reading resolution.
Also, the back side scanning resolution is fixed at 600 dpi.
Then, the process proceeds to Step 88.

When the setting of various parameters is completed in each of the above processes and the CPU 10 starts controlling the drive motor, in step 88, the document transport mechanism 43 starts transporting the document at the reading linear speed set by the CPU 10, and step Proceed to 89.
In step 89, the CPU 10 starts reading the document and, when the single-sided reading mode is input, the surface reading line period and the surface reading resolution set by the CPU 10 by the CCD image sensor 2 of the image reading apparatus 102. The image data on the surface of the document conveyed by the document conveying mechanism 43 is read according to various parameters including
In this case, the image data on the surface of the document read by the CCD image sensor 2 is mechanically scaled to a magnification specified in the sub-scanning direction.

When the double-sided reading mode is input and the zooming range is within a range of resolution: 300 to 400 dpi, the CCD image sensor 2 causes various parameters including the surface reading line period and the surface reading resolution set by the CPU 10. Accordingly, the image data on the surface of the document conveyed by the document conveying mechanism 43 is read.
The CIS 3 reads the image data on the back side of the document conveyed by the document conveyance mechanism 43 in accordance with various parameters including the LED lighting duty and the back surface reading line period set by the CPU 10.
In this case, the image data on the front side of the document read by the CCD image sensor 2 is mechanically scaled to a resolution of 400 dpi in the sub-scanning direction, and the image data on the back side of the document read by the CIS 3 is No scaling has been done.

For this reason, the input image processing unit 16 is further electrically connected in the sub-scanning direction so that the specified magnification is obtained when the image data scaled to resolution: 400 dpi is transferred from the CCD image sensor 2. Performs variable magnification.
Similarly, when the image data on the back side of the document is transferred from the CIS 3, the input image processing unit 16 performs electrical scaling to a magnification specified in the sub-scanning direction.
When the double-sided reading mode is input and the zooming range is outside the range of resolution: 300 to 400 dpi, the CCD image sensor 2 reads the document according to the surface reading line period and the surface reading resolution set by the CPU 10. The image data on the surface of the document conveyed by the conveyance mechanism 43 is read.
The CIS 3 reads the image data on the back side of the document conveyed by the document conveyance mechanism 43 in accordance with various parameters including the LED lighting duty and the back surface reading line period set by the CPU 10.

In this case, the image data on the front surface of the document read by the CCD image sensor 2 and the image data on the back surface of the document read by the CIS 3 are not scaled.
For this reason, when the image data on the surface of the document is transferred from the CCD image sensor 2, the input image processing unit 16 performs electrical scaling to the magnification specified in the sub-scanning direction, and similarly, the input image When the image data on the back side of the document is transferred from the CIS 3, the processing unit 16 performs electrical scaling to a magnification specified in the sub-scanning direction.
Then, the process proceeds to Step 90.
In step 90, when the CPU 10 of the image reading apparatus 102 finishes reading the image data for all the lines on the front side of the document or reading the image data for all the lines on the back side of the document, the CPU 10 ends the reading of the document. Proceed to 91.

In step 91, the CPU 10 ends the control of the drive motor, ends the document transport by the document transport mechanism 43, and ends the reading process.
As described above, in the image forming apparatus 100 according to the fourth embodiment, only mechanical scaling is performed in the single-sided reading mode, so that productivity can be maximized.
In the double-sided reading mode, when the reduction ratio is large (in the case of resolution: 300 to 400 dpi), the magnification is changed by combining mechanical scaling and electrical scaling.
For example, when scaling to resolution: 350 dpi, the image data on the surface of the document is first mechanically scaled from resolution: 600 dpi to resolution: 400 dpi, and then electrically scaled to resolution: 350 dpi.

Image data on the back side of the document is electrically scaled from resolution: 600 dpi to resolution: 350 dpi.
Therefore, the lower limit value of the back surface scanning line cycle can be increased and the LED lighting duty of the light source 44 can be increased as compared with the case where the scaling of the image data on the front side of the document is handled only by mechanical scaling. it can.
As a result, the illuminance of the LED that is the light source 44 can also be reduced, and the occurrence of side effects such as an increase in cost and an increase in heat generation can be suppressed.
In other words, by using mechanical zooming and electrical zooming together, it is possible to suppress the occurrence of side effects as described above while maintaining productivity.

Example 5
Next, the image forming apparatus 100 according to the fifth embodiment will be described.
In the image forming apparatus 100 according to the fifth embodiment, the functions of the image forming apparatuses 100 according to the first to fourth embodiments described above are appropriately combined.
For example, when the functions of the image forming apparatus 100 according to the first and third embodiments are combined, it is possible to select whether to give priority to productivity or reusability when performing single-sided reading or double-sided reading. .

Example 6
Next, the image forming apparatus 100 of Example 6 will be described.
In the image forming apparatus 100 of the first to fifth embodiments, the light source 44 of the CIS 3 is an LED, and the example in which the light accumulation time is controlled by controlling the lighting of the LED has been described. In the apparatus 100, an example in which the light accumulation time is controlled using the electronic shutter function of the CIS 3 will be described.
In the following description, the description of parts common to the first to fifth embodiments will be omitted, and only differences from the first to fifth embodiments will be described in detail.
The configuration of the image forming apparatus 100 according to the sixth embodiment is different from the image forming apparatus 100 according to the first to fifth embodiments in that a xenon lamp is provided as the light source 44, and the other parts are the same as those described above. A name and a code | symbol are attached | subjected and the description is abbreviate | omitted.

The functional configurations of the image processing unit 1 and the controller 4 of the image forming apparatus 100 according to the sixth embodiment are the same. However, the first to fifth embodiments control the electronic shutter of the CIS 3 at the time of image reading. The point is different.
The CIS 3 includes a xenon lamp as the light source 44.
It is difficult to control lighting and extinction of this xenon lamp in one line cycle from the viewpoint of responsiveness.
Therefore, in the CIS 3 of the image forming apparatus 100 according to the sixth embodiment, the light accumulation time is set to be equal to or lower than the lower limit value of the reading line cycle by using the electronic shutter function of the CIS 3 instead of controlling the lighting of the xenon lamp of the light source 44. Control.
Note that the processing for controlling the light accumulation time of the light source 44 to be equal to or lower than the lower limit value of the reading line cycle using the electronic shutter function of the CIS 3 described below can be similarly performed even when the light source 44 is an LED. This can be performed instead of the LED lighting control in the image forming apparatus 100 of the first to fifth embodiments.

FIG. 10 is a flowchart illustrating electronic shutter adjustment processing in the image forming apparatus 100 according to the sixth embodiment.
The process shown in FIG. 10 is for the case where the light source 44 is a xenon lamp, the reference document for adjustment is placed on the document tray 40 of the ADF 101, and input image processing is performed based on the operation information input from the operation display unit 7. This is executed when an adjustment start is input from the operation display unit 7 while the electronic shutter duty adjustment mode is set in the CPU 10 by the unit 16.

Further, as an operation specification, when the range of mechanical scaling is 50 to 100% (resolution: equivalent to 300 to 600 dpi) and the image reading apparatus 102 performs the same magnification reading, the reading linear velocity is 300 mm / sec, An example in which the front side scanning line period is 141 μsec, the front side scanning resolution is 600 dpi, the back side scanning line period is 141 μsec, and the back side scanning resolution is 600 dpi is described, but the present invention is not limited to this example.
Further, the back side reading CIS3 is a 1 × magnification sensor, and has a higher S / N characteristic than the reduction optical system on the front surface, and can obtain an S / N characteristic equivalent to that on the front surface when the light accumulation time on the back surface is less than the lower limit setting. It shall be possible.
When the CPU 10 receives an adjustment start instruction input from the operation display unit 7 via the CPU 20 in step (indicated by “S” in the figure) 101, the CPU 10 displays the electronic shutter duty (back surface sensor electronic shutter basic duty) of the CIS 3. Lower limit value (adjustment reference value) of the back side scanning line cycle (scanning line cycle on the back side of the document): 70 μsec, and the process proceeds to step 102.

In step 102, the reading linear velocity of the front and back surfaces is set to 300 mm / sec, and the process proceeds to step 103.
In step 103, the reading line period on the front surface and the back surface is set to 141 μsec, and the process proceeds to step 104. In step 104, the shading correction is set to OFF, and the process proceeds to step 105.
In step 105, the lamp 33 and the light source 44 are turned on, and the process proceeds to step 106.
In step 106, the reference document set on the document tray 40 of the ADF 101 is conveyed, and reading of the images on the front and back surfaces of the reference document is started, and the image data on the front surface and the image data on the back surface are acquired. move on.
In step 107, the S / N detector 17 detects S / N characteristics (ratio of signal level and noise component (standard deviation, peak / bottom)) from the image data of the front surface and the image data of the back surface, respectively. Proceed to step 108.

It is assumed that the density of the reference document is set to the upper limit of the density range that can be read by the document reading apparatus 102.
In step 108, reading of the images on the front and back sides of the reference document is terminated, and the process proceeds to step 109.
In step 109, the lamp 33 and the light source 44 are turned off, and the process proceeds to step 110.
In step 110, an electronic shutter Duty: Tadj is calculated so that the S / N characteristic detected for the image on the front side of the reference original and the S / N characteristic detected for the image on the back side of the reference original are equal to each other. move on.
For the processing of step 110, simply, the electronic shutter duty of CIS3 is calculated so that the output level of the sensor becomes a constant value (the sensor output target value on the back surface converted from the sensor output level on the front surface). The calculated value may be stored in the memory.

In this case, when the electronic shutter duty is 70 μsec and the sensor output level is Vini, if the target output level is Vtgt, the electronic shutter duty is calculated as 70 × Vtgt / Viniμsec.
In step 111, the electronic shutter Duty: Tadj in which the S / N characteristics of the front and back images are equal is stored in the memory, and the process proceeds to step 112.
In step 112, the shading correction is set to ON and the adjustment process is terminated.
In the above-described adjustment process, the reference document is read. However, if a reference white plate for shading correction is used instead of the reference document, it is necessary to prepare a reference document for adjustment. In addition, even in the user's usage environment, adjustments can be made during the initialization operation when the power is turned on.

Next, processing for reading both sides of a normally used document in the image forming apparatus 100 according to the sixth embodiment will be described.
FIG. 11 is a flowchart illustrating document double-sided reading processing in the image forming apparatus 100 according to the sixth embodiment.
In the double-sided reading process of the original, the operation display unit is set in a state where the original is placed on the original tray 140 of the ADF 101 and the double-sided reading mode is set by the input image processing unit 16 based on an input from the operation display unit 7. 7 starts when a document reading start is input.
Further, when the range of the magnification ratio for mechanical scaling is 50 to 100% (resolution: equivalent to 300 to 600 dpi) and the image reading apparatus 102 performs the same magnification reading, the scanning linear velocity of the original is 300 mm / sec. An example in which the reading line cycle on the front side of the document is 141 μsec, the reading resolution on the front side of the document is 600 dpi, the reading line cycle on the back side of the document is 141 μsec, and the reading resolution on the back side of the document is 600 dpi will be described. It is not limited to.

First, when the CPU 10 receives a document reading start input from the operation display unit 7 via the CPU 20, the setting of the electronic shutter function of the CIS 3 is stored in the memory in step (indicated by “S” in the drawing) 121. The electronic shutter Duty is set to Tadj (μsec) (corresponding to a value equal to or lower than the lower limit value of the back surface scanning line cycle), and the process proceeds to Step 122.
For example, when the lower limit value of the back side scanning line cycle (scanning line cycle of the back side of the document) is 70.5 (= 141 × (1/2)) μsec, the CPU 10 sets the electronic shutter function setting of the CIS 3 to 70 μsec or less. Set to adjusted Tadj (μsec).
In step 122, the CPU 10 sets the surface reading line period (the reading line period on the surface of the document, which corresponds to the “first reading period”) to 141 μsec, and proceeds to step 123.

In step 123, the CPU 10 determines whether or not a zooming input for inputting a zooming ratio is performed from the operation display unit 7 before inputting the reading start of the document. If the zooming input is performed (Y Step) Proceed to Step 124, and if zooming input is not performed (in the case of N), proceed to Step 131.
In step 124, the CPU 10 sets a reading linear velocity (corresponding to a conveying speed): 300 / magnification / magnification mm / sec according to the magnification / magnification input from the operation display unit 7 and received via the CPU 20.
In other words, the CPU 10 sets a reading linear speed: 300 / magnification / magnification mm / sec, which is a speed obtained by dividing 300 mm / sec, which is a reading linear speed when carrying out equal magnification reading, by a magnification.

For example, when the variable magnification is 1/2 (50%), the CPU 10 sets the reading linear velocity to 600 (= 300 / (1/2)) mm / sec.
Here, in this processing example, since the variable magnification range is 50 to 100%, the reading linear velocity is set in the range of 300 to 600 mm / sec.
Then, the process proceeds to step 125.
In step 125, the CPU 10 receives the back side scanning line period (corresponding to the scanning line on the back side of the document, the second scanning period) according to the scaling factor input from the operation display unit 7 and received through the CPU 20. Set magnification μsec.
That is, the CPU 10 sets a back side scanning line cycle of 141 × variable magnification μsec, which is obtained by multiplying 141 μsec, which is the back side scanning line cycle in the case of performing equal magnification reading, by a variable magnification.

For example, when the variable magnification is 1/2 (50%), the CPU 10 sets the back surface scanning line cycle to 70.5 (= 141 × (1/2)) μsec.
Here, in this processing example, since the variable magnification range is 50 to 100%, the back side scanning line cycle is set in the range of 70.5 to 141 μsec, and the lower limit value of the back side scanning line cycle is 70.5 μsec. It becomes.
Then, the process proceeds to step 126.
In step 126, the CPU 10 determines the surface reading resolution (corresponding to the reading resolution of the surface of the original document, the first resolution) according to the scaling factor input from the operation display unit 7 and received via the CPU 20: 600 × magnification scaling factor dpi. Set.
That is, the CPU 10 sets the surface reading resolution: 600 × the scaling factor dpi by a resolution obtained by multiplying the surface reading resolution of 600 dpi, which is the same magnification reading, by the scaling factor.

For example, when the scaling factor is 1/2 (50%), the CPU 10 sets the surface reading resolution to 300 (= 600 × (1/2)) dpi.
Here, in this processing example, since the variable magnification range is 50 to 100%, the surface reading resolution is set in the range of 300 to 600 dpi.
The back side scanning resolution (corresponding to the second resolution) is fixed at 600 dpi.
Then, the process proceeds to step 127. On the other hand, if it is determined in step 123 that the scaling display is not input from the operation display unit 7 before the reading start input (in the case of N), in step 131, the CPU 10 performs the normal magnification reading. If the reading linear velocity is 300 mm / sec, the reading linear velocity is set as the reading linear velocity.
In step 132, the CPU 10 sets 141 μsec, which is the back side scanning line cycle when performing 1 × scanning, as the back side scanning line cycle, and proceeds to step 133.

In step 133, the CPU 10 sets the surface reading resolution of 600 dpi, which is the surface reading resolution when performing the normal magnification reading, to the surface reading resolution.
The back side scanning resolution is fixed at 600 dpi.
Then, the process proceeds to Step 127.
When the setting of various parameters is completed in each process described above and the CPU 10 starts controlling the drive motor, in step 127, the document transport mechanism 43 starts transporting the document at the reading linear speed set by the CPU 10, and step Proceed to 128.
In step 128, the CPU 10 starts reading the document, and is conveyed by the document conveying mechanism 43 by the CCD image sensor 2 of the image reading apparatus 102 according to various parameters including the surface reading line period and the surface reading resolution set by the CPU 10. Read the image data on the front side of the original document, and read the image data on the back side of the original document conveyed by the original document conveyance mechanism 43 according to various parameters including the electronic shutter duty and the back surface reading line period set by the CPU 10 by the CIS3. Proceed to step 129.

FIG. 12 is a timing chart showing an example of signals exchanged between the CIS 3 and the input image processing unit 16 in the case of performing the same magnification reading in the processing shown in FIG.
In the example shown in FIG. 12, the CIS 3 is based on the pixel clock signal VCLK shown in FIG. 12A, and as shown in FIG. In the figure, an arrow A in the figure of the line synchronization signal XLSYNC is generated and output to the input image processing unit 16.
As shown in FIG. 12C, the lamp lighting signal LED_ON is output to the input image processing unit 16 during the image reading period.
Further, as shown in FIG. 12D, the CIS 3 generates an electronic shutter control signal SENS_ON indicating release of the electronic shutter in synchronization with the line synchronization signal XLSYN, and Tadj (μsec) set by the electronic shutter Duty. ) To the input image processing unit 16.

Further, as shown in FIG. 12E, the CIS 3 outputs the image signal ViDEO_DATA to the input image processing unit 16 within the back surface scanning line cycle.
That is, in the example shown in FIG. 12, the CIS 3 starts reading image data for one line on the back side of the document every 141 μsec, and releases the electronic shutter for Tadj (μsec) and accumulates light.
The CIS 3 reads the image data for one line on the back side of the document within the period of 141 μsec (effective image data in the figure) and outputs it to the input image processing unit 16. The xenon lamp is lit during the image reading period.

FIG. 13 is a timing chart illustrating an example of signals exchanged between the CIS 3 and the input image processing unit 16 when performing variable magnification reading at a variable magnification of 1/2 in the processing illustrated in FIG.
In the example shown in FIG. 13, the CIS 3 is based on the pixel clock signal VCLK shown in FIG. 13A, and as shown in FIG. An arrow B in the figure of the line synchronization signal XLSYNC is generated every 5 μsec and output to the input image processing unit 16.
Further, as illustrated in FIG. 13C, the lamp lighting signal LED_ON is output to the input image processing unit 16 during the image reading period.

Further, as shown in FIG. 13D, the CIS 3 generates an electronic shutter control signal SENS_ON indicating release of the electronic shutter in synchronization with the line synchronization signal XLSYN, and Tadj (μsec) set by the electronic shutter Duty. ) To the input image processing unit 16.
As shown in FIG. 13E, the CIS 3 outputs the image signal ViDEO_DATA to the input image processing unit 16 within the back surface reading line cycle.
That is, in the example shown in FIG. 13, the CIS 3 starts reading image data for one line on the back side of the document every 70.5 μsec, and releases the electronic shutter for a period of Tadj (μsec) and accumulates light. .

Then, the CIS 3 reads the image data for one line on the back side of the document (effective image data in the drawing) and outputs it to the input image processing unit 16 within a period of 70.5 μsec. The xenon lamp is lit during the image reading period.
In the case of the example shown in FIG. 13, the image data for one line on the surface of the document read by the CCD image sensor 2 is mechanically scaled to 50% (resolution: 300 dpi) in the sub-scanning direction of the document. However, the image data on the back side of the document read by the CIS 3 is not scaled.
Therefore, when the image data on the back side of the document is transferred from the CIS 3, the input image processing unit 16 electrically performs scaling to 50% (resolution: 300 dpi) in the sub-scanning direction.

Next, returning to FIG. 11, in step 129, the CPU 10 of the image reading apparatus 102 finishes reading the image data for all the lines on the front side of the document and reading the image data for all the lines on the back side of the document. The reading of the original is finished, and the process proceeds to step 130.
In step 130, the CPU 10 ends the control of the drive motor, ends the document transport by the document transport mechanism 43, and ends the double-sided reading process.
As described above, even in the image forming apparatus according to the sixth embodiment, even when the resolution is fixed, the reading line speed is increased according to the reduction rate, and the reading line cycle is shortened according to the reduction rate. Since the magnification is electrically changed, it is possible to prevent the reading speed of the document from being lowered and the productivity from being lowered, and to maintain the same productivity as the case of performing the mechanical magnification.

In addition, since the setting of the electronic shutter function of the CIS 3 is controlled to be equal to or lower than the lower limit value of the reading line cycle, the light accumulation time can be kept constant even if the reading line cycle is changed according to the variable magnification. Change and degradation of image quality can be prevented.
Furthermore, since the S / N characteristics of the front and back surfaces are adjusted equally, the image quality can be stabilized.
It is assumed that the xenon lamp of the light source 44 is designed with an illumination system having an illuminance necessary to satisfy the S / N characteristic that is the reading performance of the image reading apparatus 102.

Example 7
Next, the image forming apparatus 100 according to the seventh embodiment will be described.
In the image forming apparatus 100 according to the seventh embodiment, the functions shown in the image forming apparatus 100 according to the first to fourth embodiments are appropriately combined, and the electronic shutter of the CIS 3 described above is controlled instead of the lighting control of the LED. .
For example, if the functions of the image forming apparatus 100 according to the first embodiment, the third embodiment, and the fifth embodiment are combined, whether to give priority to productivity when performing single-sided reading or double-sided reading when controlling the electronic shutter of the CIS3. It is possible to select whether to give priority to reusability.

The effects of Examples 1 to 7 are listed.
(1) In a reading apparatus capable of reading both sides of a document at the same time, the reading cycle can be changed without changing the reading characteristics of the reading means whose reading resolution cannot be changed. It is possible to stabilize the characteristics by detecting the difference between the reading characteristics of the front surface and the back surface and reducing the difference by corresponding to the reading cycle corresponding to the mechanical magnification while maintaining the resolution.
(2) Adjusting the light accumulation time of the sensor within a range below the lower limit value of the reading line cycle variable range of the sensor to reduce the difference in S / N characteristics between the front surface and the back surface, thereby making the reading cycle of the back surface variable. Therefore, it is possible to reduce and stabilize the reading characteristic variation and the difference in reading characteristics between the front surface and the back surface.
(3) By controlling the lighting duty of the light source, the light accumulation time of the sensor is made constant, and it becomes possible to prevent the reading characteristics from being affected by a variable reading cycle or a difference from the surface.

(4) By synchronizing the light source lighting duty with the reading synchronization signal of the line sensor, it is possible to easily control the light accumulation time and stabilize the reading characteristics.
(5) By directly controlling the light storage time of the sensor, it is possible to stabilize the reading characteristics.
(6) By changing the line cycle on the back surface, it is possible to transport the document at a transport speed corresponding to the variable magnification without changing the resolution, thereby improving productivity.
(7) By further providing a scaling unit that electrically scales, it becomes possible to improve productivity and cope with any scaling.
(8) The conditions for reading image data can be changed according to the purpose of use of the image reading apparatus.

(9) The image reading apparatus or the image forming apparatus can be used with priority on productivity or reusability.
(10) The image reading apparatus or the image forming apparatus can be used with priority on productivity or reusability depending on the application.
(11) The image reading apparatus or the image forming apparatus can be used with priority on productivity or reusability depending on the single-side reading or the double-side reading.
(12) It can be provided in an image forming apparatus such as a digital copying machine, a digital multifunction peripheral, a scanner, or a FAX.
(13) By enabling selection of whether to prioritize productivity or reusability from the operation display unit, it is possible to improve the operability of the user.

  The image reading apparatus and the image forming apparatus according to the present invention can be applied to a scanner, a facsimile machine, a printer, a copying machine, and a multifunction machine.

1: Image processing unit 2: CCD image sensor 3: CIS 4: Controller 5: Output image processing unit 6: LD driver 7: Operation display unit 10, 20: CPU 11: CPU memory 12, 13: Data conversion unit 14: Memory 15: Memory control unit 16: Input image processing unit 17: S / N detection unit 21: Image controller 22: I / O controller 30: Slit glass 31: Contact glass 32: Reference white plate 33: Lamp 34: First mirror 35: First carriage 36: Second mirror 37: Third mirror 38: Second carriage 39: Lens unit 40: Document tray 41: Reference white roller 42: Paper discharge tray 43: Document transport mechanism 44: Light source 100: Image forming apparatus 101 : ADF 1 2: the image reading apparatus 103: main unit 104: an exposure device

JP 2005-217561 A JP 2009-033723 A

Claims (13)

First image reading means for reading first image data that is an image of one side of the document at a first resolution corresponding to a predetermined magnification and a predetermined first reading cycle;
Second image reading means for accumulating light emitted from a light source and reading second image data which is an image on the other side of the document at a second reading period corresponding to a second resolution fixed in advance and the magnification. When,
S / N detection means for detecting an S / N ratio between the first image data read by the first image reading means and the second image data read by the second image reading means;
An image reading apparatus comprising: a control unit configured to vary a light accumulation time during image reading of the second image reading unit based on an S / N ratio detected by the S / N detection unit.   The second image reading means can vary the light accumulation time at the time of reading the second image data within a range equal to or less than the lower limit value of the second reading cycle based on the S / N ratio of the first image data. The image reading apparatus according to claim 1, further comprising a control unit.   The second image reading unit controls lighting of the light source based on an S / N ratio of the first image data, and the light accumulation time is variable within a range equal to or less than a lower limit value of the second reading cycle. The image reading apparatus according to claim 1, further comprising a control unit.   The second image reading unit reads one line of the image on the other side of the document according to the line synchronization signal input every second reading cycle, and input is started in synchronization with the line synchronization signal. 4. The image reading apparatus according to claim 3, further comprising means for turning on the light source in accordance with a lighting signal that ends input below the lower limit value.   The second image reading unit reads one line of the image on the other side of the document according to the line synchronization signal input every second reading cycle, and input is started in synchronization with the line synchronization signal. 3. The image reading apparatus according to claim 2, further comprising means for accumulating light emitted from the light source in accordance with a control signal that is input below the lower limit value.   The image reading apparatus according to claim 1, further comprising a conveyance unit that conveys the document at a conveyance speed corresponding to the variable magnification.   The image reading apparatus according to claim 1, further comprising a scaling unit that electrically scales the second image data at the scaling factor. In the first mode, the first image reading unit reads the first image data from one side of the document with the first resolution and the first reading period corresponding to the magnification, and in the second mode, Means for reading the first image data from one side of the document at the predetermined first resolution and the first reading period;
In the first mode, the second image reading unit reads the second image data from the other surface of the document at the second reading cycle according to the second resolution and the magnification, and the second mode. Then, means for reading the second image data from the other side of the document at the second resolution and the predetermined second reading cycle,
8. The image reading apparatus according to claim 7, wherein the scaling means includes means for electrically scaling the first image data read in the second mode with the scaling ratio.   The image reading apparatus according to claim 8, wherein the first mode is a productivity mode that prioritizes productivity, and the second mode is a reusability mode that prioritizes reusability.   The image reading apparatus according to claim 8, wherein the first mode is a first application mode, and the second mode is a second application mode. In the single-sided reading mode, the first image reading unit reads the first image data from one side of the document at the first resolution and the first reading period corresponding to the magnification, and in the double-sided reading mode, Means for reading the first image data from one side of the document at the predetermined first resolution and the first reading period;
In the double-sided reading mode, the second image reading unit reads the second image data from the other side of the document at the second resolution and a predetermined second reading period.
8. The image reading apparatus according to claim 7, wherein the scaling means includes means for electrically scaling the first image data read in the double-sided reading mode with the scaling ratio.   An image forming apparatus comprising the image reading apparatus according to claim 1.   11. An image forming apparatus comprising: the image reading apparatus according to claim 8; and a mode input unit that selectively inputs a type of the mode.

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