JP2012075006A - Document reader, document reading method, and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique which shortens a reading time while restraining inappropriate reading resolution of a document.SOLUTION: A document reader comprises: a document feeding part for feeding a document; reading parts 21 and 22 capable of reading the first surface and the second surface of the document fed by the document feeding part; a determination part 41 which determines whether reading of the second surface of the document by second resolution is proper or not, the second resolution being lower than first resolution at the time of starting reading of the first surface of the document; and a switch part 42 which switches the resolution at the time of reading the second surface to the second resolution when it is judged that the reading of the second surface by the second resolution is proper.

Description

  The present invention relates to an original reading apparatus, and more particularly to a technique for changing a reading resolution when an original is read by the original reading apparatus.

  Conventionally, as a technique for changing the reading resolution when reading an original in an original reading apparatus, for example, in Patent Document 1, the reading resolution is changed from the middle of reading by a user operating an operation unit during double-side reading of an original. Techniques to do this are disclosed.

JP 2001-160877 A

  According to the above-described prior art document, for example, when the user starts reading at the first resolution but feels that the first resolution is high and the reading process is slow, the user operates the operation unit to operate the first resolution. By changing to the second resolution, which is a lower resolution than that, the reading speed can be increased.

  However, if the user changes the reading resolution to the second resolution at will, the reading speed can be increased, but there is a possibility that a document to be read at a high resolution such as a photograph may be read at an inappropriate second resolution.

  Further, if the user confirms the image of the document and then changes the reading resolution to the second resolution, the possibility of reading the document to be read at the high resolution at the second resolution can be reduced. The operation takes time, and it is difficult to shorten the reading time from the start of reading to the end of reading.

  The present invention provides a technique for shortening a reading time while suppressing an inappropriate reading resolution of a document.

According to a first aspect of the present invention, there is provided a document reading device that transports a document, a reading unit capable of reading the first and second surfaces of the document transported by the document transport unit, and the document. A determination unit that determines whether the reading process of the second side of the document at a second resolution lower than the first resolution at the time of starting the reading process of the first side is appropriate; A switching unit that switches the resolution at the time of reading the second surface to the second resolution when it is determined that the reading processing of the second surface at the resolution is appropriate.
According to this configuration, even when reading of the first surface is started at the first resolution, it is determined that the reading processing of the second surface at the second resolution that is lower than the first resolution is appropriate. In this case, the resolution at the time of reading the second surface is switched to the second resolution. Therefore, the reading time can be shortened while suppressing the reading resolution of the original from becoming inappropriate.

According to a second aspect of the present invention, in the original reading apparatus according to the first aspect of the present invention, the first reading unit further includes a first analyzing unit that analyzes the read image of the first surface, When it is analyzed that the read image is a text image, it is determined that the reading process of the second surface at the second resolution is appropriate.
According to this configuration, if the first surface of the document read by the document transport unit in a series of reading processes is a text image, the second surface is also likely to be a text image, and the first surface is a text image. By determining that the reading process of the second surface at the second resolution is appropriate, the reading time can be shortened while suppressing the reading resolution of the document from becoming inappropriate.

According to a third aspect of the present invention, in the document reading device according to the first or second aspect, the reading unit reads the first surface of the conveyed document at a first reading position; A second reading position is provided on the downstream side in the document conveying direction of one reading unit, and reads the second surface, which is the opposite surface of the original document having the first surface conveyed from the first reading unit, at a second reading position. A reading unit.
According to this configuration, in a configuration of a double reading unit, for example, a double CIS (contact image sensor), it is possible to reduce the reading time while suppressing an inappropriate reading resolution of the document.

According to a fourth aspect of the present invention, in the original reading device of the third aspect, a selection unit for a user to select a reading process for reading an original having a surface to be read at the first resolution and a surface to be read at the second resolution. And a notifying unit for notifying that the surface to be read at the first resolution is set as the first surface on the document conveying unit when the reading process is selected, and the determination unit includes When the reading process is selected, it is determined that the reading process of the second surface at the second resolution is appropriate.
According to this configuration, when performing a reading process for reading a document having a surface to be read at the first resolution and a surface to be read at the second resolution, it is possible to more reliably suppress the reading resolution of the document from becoming inappropriate. .

According to a fifth aspect, in the document reading apparatus according to the fourth aspect, the switching unit switches the resolution at the time of reading the second surface to the second resolution when the reading processing of the first surface is completed.
According to this configuration, since the entire first surface can be read at the first resolution, the read image quality of the first surface is good. This is effective when the first surface is an image to be read at high resolution.

According to a sixth invention, in the document reading apparatus according to the third invention, a first analysis unit that analyzes the read image on the first surface, a second analysis unit that analyzes the read image on the second surface, An estimation unit that estimates whether or not the image of the first surface and the image of the second surface are the same image from the analysis result by the first analysis unit and the analysis result by the second analysis unit; The determination unit determines that the reading process of the first surface of the document at the second resolution is appropriate from the analysis result of the first analysis unit, and the image of each surface is estimated from the estimation of the estimation unit. When it is estimated that the images are the same, it is determined that the reading process of the second surface at the second resolution is appropriate.
According to this configuration, it is possible to suppress reading at different reading resolutions even though the first surface and the second surface are the same image.

According to a seventh aspect, in the document reading device according to the sixth aspect, the first analysis unit extracts a color used on the first surface, and the second analysis unit is used on the second surface. And the estimation unit determines whether the image of the first surface and the image of the second surface are the same image, and whether the colors of the extracted surfaces are the same. Estimate by comparison.
According to this configuration, it is preferable to compare whether the image on the first side and the image on the second side are the same image regardless of whether the document has a long side or a short side. it can.

According to an eighth aspect of the present invention, in the document reading apparatus according to the sixth aspect, the first analysis unit extracts at least one line data of the rear end position of the resolution estimation section of the first surface, and the second analysis unit includes the first analysis unit. Extracting at least one line data of the rear end position of the resolution estimation section of two surfaces, the estimation unit has extracted whether the image of the first surface and the image of the second surface are the same image It is estimated by comparing whether or not the extracted line data of each surface is the same.
According to this configuration, it is possible to suitably compare whether or not the image on the first side and the image on the second side are the same image when the document has a short side.

According to a ninth aspect of the present invention, in the document reading apparatus according to the sixth aspect, the first analysis unit extracts several line data of the leading position of the resolution estimation section of the first surface, and the second analysis unit includes the second surface. The number of line data of the position of the resolution estimation section is extracted, and the estimation unit extracts whether each of the extracted surfaces is the same as the image of the first surface and the image of the second surface. It is estimated by comparing whether or not the line data is the same.
According to this configuration, it is possible to suitably compare whether the image on the first side and the image on the second side are the same image when the document has a long side.

According to a tenth aspect of the invention, in the document reading device according to any one of the sixth to ninth aspects, the switching unit determines that the reading process of the second surface at the second resolution is appropriate. The resolution at the time of reading the first surface is also switched to the second resolution.
According to this configuration, the reading time can be further shortened. Although the resolution is switched during reading, since both sides need to be read with low resolution, even if the reading image quality is uneven, it is acceptable.

An eleventh aspect of the invention is the document reading apparatus according to the tenth aspect of the invention, further comprising a conversion unit that converts the image read at the first resolution into the second resolution.
According to this configuration, it is possible to suppress unevenness in the read image quality.

An image forming apparatus according to a twelfth aspect includes the document reading apparatus according to any one of the first to eleventh aspects, and an image forming unit that forms an image based on the document read by the document reading apparatus.
According to this configuration, in the image forming apparatus having the document reading function, it is possible to reduce the reading time while suppressing the reading resolution of the document from becoming inappropriate.

A document reading method according to a thirteenth aspect of the present invention is a document reading method in a document reading apparatus having a reading unit capable of reading the first and second surfaces of a document, wherein the first surface of the document is read. Determining whether or not the reading process of the second side of the document at the second resolution lower than the first resolution when the reading unit starts is appropriate, and the determination step determines the first A switching step of switching the resolution at the time of reading the second surface to the second resolution when it is determined that the reading processing of the second surface at two resolutions is appropriate.
According to this configuration, it is possible to shorten the reading time while suppressing an inappropriate reading resolution of the document.

Schematic diagram showing the electrical configuration of the MFP according to the embodiment Schematic diagram showing a simplified configuration of the reading unit Block diagram showing electrical configuration of ASIC Illustration of resolution estimation level Flow chart showing the flow of reading processing Flowchart showing selection of same-side original document estimation processing Flowchart showing the flow of the same document estimation process on the back and front of A The flowchart which shows the flow of the same original estimation process of the back and front of B The flowchart which shows the flow of the same original estimation process of the back and front of C The flowchart which shows the flow of the same original estimation process of back and front of D

<Embodiment>
An embodiment of the present invention will be described with reference to FIGS.
1. Configuration of Image Reading Apparatus FIG. 1 is a schematic diagram showing an electrical configuration of a so-called multifunction machine (an example of an image forming apparatus and an image reading apparatus) 1 having a print function, a scan function, and a copy function. Note that the image forming apparatus is not limited to a multifunction peripheral, and may be simply a copier, for example. Further, the image reading apparatus is not limited to the multi-function peripheral, and may be simply an image scanner, for example.

  The multifunction device 1 includes a control unit 10, an operation unit 12, a reading unit 13, an ASIC 14, and a printing unit (an example of an image forming unit) 15.

  The control unit 10 includes a CPU 11, a ROM 11a, and a RAM 11b. The CPU 11 controls each unit of the multifunction machine 1 by executing various programs stored in the ROM 11a. The ROM 11a stores various programs executed by the CPU 11. The RAM 11b is used as a main storage device for the CPU 11 to execute various processes.

  The operation unit 12 (an example of a selection unit and a notification unit) includes a display device (an example of a notification unit) such as an LCD (Liquid Crystal Display), various buttons (an example of a selection unit), and the like. The user can perform various operations such as function selection and reading condition setting by operating the operation unit 12.

  The reading unit 13 includes an ADF (Auto Document Feeder: an example of a document conveying unit, see FIG. 2) 27 that conveys the document 5, an image sensor, and the like, reads the document 5, and outputs image data to the ASIC 40. The reading unit 13 includes a first CIS (Contact Image Sensor: an example of a first reading unit, see FIG. 2) 21 that reads a back side (corresponding to “first side of a document”) 5b and a front side (“ A second CIS 22 (an example of a second reading unit, see FIG. 2). By these CIS 21 and 22, both surfaces 5a and 5b of the document 5 are read.

  That is, the first CIS 21 reads the back side (hereinafter referred to as “original side back”) 5b of the conveyed document at the first reading position P1. On the other hand, the second CIS 22 is provided downstream of the first CIS 21 in the document conveyance direction, and the surface 5 (hereinafter referred to as “document surface”) a of the document conveyed from the first CIS 21 is a second reading position. Read at P2.

  An ASIC 40 (Application Specific Integrated Circuit) performs various processes on image data output from the reading unit 13 or image data transmitted from an external computer (not shown) connected to the multifunction device 1 so as to be communicable. Circuit. The configuration of the ASIC 14 will be described later.

  The printing unit 15 forms an image by a CMYK four color material (toner, ink, etc.) on a recording medium such as paper based on the image data output from the ASIC 40 by an electrophotographic method, an inkjet method, or the like ( Printing).

2. Configuration of Reading Unit FIG. 2 is a schematic diagram showing a simplified configuration of the reading unit 13.

  A housing 23 (only a part of which is shown in FIG. 2) is formed in a box shape, and a first platen glass 24 and a second platen glass 25 are juxtaposed on the top.

  The document cover 26 is coupled to the housing 23 so as to be rotatable between a closed posture that covers the upper surface of the housing 23 and an open posture that opens the upper surface of the housing 23. The document cover 26 is provided with an ADF 27, a document tray 28 on which documents 5 such as paper are stacked, a paper discharge tray 29, and the like.

  Inside the ADF 27, there are a separation roller 30, a suction roller 32 that is rotatably provided at a distal end portion of an arm 31 that is pivotally supported by a shaft that supports the separation roller 30, a plurality of conveyance rollers 33, 34, a paper discharge roller 35, and a plurality of driven rollers 36 in pressure contact therewith. The document 5 is conveyed by these rollers and is conveyed on the conveyance path 37, and is discharged onto the discharge tray 29 through the reading position P <b> 1 by the first CIS 21 and the reading position P <b> 2 by the second CIS 22. .

  Further, for example, a document sensor 38 is provided between the separation roller 30 and the conveyance roller 33. For example, the document sensor 38 detects the leading edge of the document 5 conveyed from the separation roller 30 to generate a document detection signal, and turns off the document detection signal as the document 5 passes through the trailing edge. The document detection signal is supplied to the ASIC 40. The ASIC 40 performs various types of control related to reading based on the detection timing of the document detection signal. For example, the ASIC 40 estimates the position of the document 5 based on the document detection signal. The position of the document 5 is estimated using the conveyance speed (known) of the document 5, the detection timing of the document detection signal, and the elapsed time from the detection timing. The elapsed time from the detection timing is measured by a timer (not shown).

  The second CIS 22 is accommodated in the housing 23 and reads the document surface (second surface) 5a. Here, the document surface 5 a is a surface facing up in the document 5 placed on the document tray 28 or a surface facing down in the document 5 placed on the first platen glass 24. is there. The second CIS 22 reads the original document 5 using an equal-magnification optical system, and includes a CMOS image sensor having a plurality of light receiving elements arranged linearly in the main scanning direction perpendicular to the paper surface, and RGB three-color light emitting diodes. A light source having a light source, a rod lens array that forms an image of reflected light reflected by the document 5 on each light receiving element of the CMOS image sensor, a carriage on which these are mounted, and a carriage in the sub-scanning direction (a direction perpendicular to the main scanning direction). In addition, a transport mechanism (not shown) that reciprocates in the direction parallel to the surface of the first platen glass 24 is provided.

  When reading the document 5 conveyed by the ADF 27, the second CIS 22 stops under the second platen glass 25 and reads the document 5 while sequentially switching the color of the light source. On the other hand, when reading the document 5 placed on the first platen glass 24, the second CIS 22 moves at a constant speed in the sub-scanning direction and reads the document 5 while sequentially switching the color of the light source. For example, the second CIS 22 can read at a resolution of 100 dpi, 200 dpi, 300 dpi, and 600 dpi.

  The first CIS 21 is fixed inside the ADF 27, and reads the back side of the document (first surface of the document) 5b conveyed by the ADF 27. Here, the document back surface 5 b is a surface facing downward in the document 5 placed on the document tray 28. The configuration of the first CIS 21 is substantially the same as the configuration of the second CIS 22 except that it is not configured to be movable.

3. Configuration of ASIC FIG. 3 is a block diagram mainly showing an electrical configuration of the ASIC 40.

The ASIC 40 includes a determination unit 41, a switching unit 42, a first analysis unit 43, a second analysis unit 44, an estimation unit 45, and a conversion unit 46.
The determination unit 41 determines whether or not the reading process of the document surface 5a at the second resolution that is lower than the first resolution at the time of starting the reading process of the document back surface 5b is appropriate. For example, here, the first resolution is 600 dpi and the second resolution is 300 dpi.

When the determination unit 41 determines that the reading process of the document surface 5a at the second resolution (300 dpi) is appropriate, the switching unit 42 switches the resolution at the time of reading the document surface 5a to the second resolution (300 dpi).
Note that the switching unit 42 may switch the resolution at the time of reading the document back surface 5b to the second resolution (300 dpi) when it is determined that the reading process of the document front surface 5a at the second resolution is appropriate.

  The first analysis unit 43 is connected to the first CIS 21 and analyzes the read image on the document back surface 5b. On the other hand, the second analysis unit 44 is connected to the second CIS 22 and analyzes the read image on the surface 5b of the document.

  When the first analysis unit 43 analyzes that the read image on the document back surface 5b is a text image, the determination unit 41 determines that the document surface 5a reading process at the second resolution (300 dpi) is appropriate.

  Note that when the first resolution is a predetermined resolution, for example, 100 dpi, the determination unit 41 may determine that the reading process of the document surface 5a at the second resolution is not appropriate. This is because the second resolution cannot be set when the first resolution is set to the lowest resolution.

  If the document back surface 5b read by the ADF 27 in a series of reading processes is a text image, the front surface 5a is likely to be a text image. Therefore, when the back surface 5b is a text image, it is determined that the reading process of the front surface 5a with the second resolution (300 dpi) is appropriate, thereby suppressing the reading resolution of the document 5 from being inappropriate and reducing the reading time. It can be shortened.

  The estimation unit 45 estimates whether or not the image on the document back surface 5b and the image on the document surface 5a are the same image from the analysis result by the first analysis unit 43 and the analysis result by the second analysis unit 44. At this time, the determination unit 41 determines from the analysis result by the first analysis unit 43 that the reading process of the document back surface 5 at the second resolution (300 dpi) is appropriate, and from the estimation of the estimation unit 45, each surface 5a, When it is estimated that the image 5b is the same image, the determination unit 41 determines that the reading process of the document surface 5a at the second resolution (300 dpi) is appropriate.

  The conversion unit 46 converts the image read at the first resolution by the first CIS 21 or the second CIS 22 into an image at the second resolution. In particular, when the switching unit 42 determines that the reading process of the document front surface 5a at the second resolution is appropriate, the conversion unit 46 also switches the resolution when reading the document back surface 5b to the second resolution (300 dpi). The image read at the first resolution (600 dpi) may be converted to the second resolution (300 dpi).

4). Reading Process Next, a reading process of the document 5 in the present embodiment will be described with reference to FIGS. FIG. 5 is a flowchart showing the flow of the reading process. This process is started when the user places the document 5 on the document tray 28 and presses the document reading start key.

4-1. Resolution Estimation Section Prior to the description of “reading process”, the “resolution estimation section” will be described.
The “resolution estimation section” is determined by, for example, the scale position Xm to which the resolution estimation level is input by the user. The setting scale 12A for the resolution estimation level is shown in FIG. 4, for example. The scale is, for example, “1” from the “high speed / simple” side to “15” from “low speed / detail”, and FIG. 4 shows the case where the scale “7” is selected. The resolution estimation level setting scale 12 </ b> A is displayed on, for example, the display device of the operation unit 12.

  When the resolution estimation level is set to “high speed / simple”, the resolution estimation section becomes narrow. On the other hand, when “low speed / detail” is set, the resolution estimation section becomes wide.

The “resolution estimation section” is calculated based on the scale position Xm as follows, for example. Dividing the distance L1 from the back CIS position (P1) to the front CIS position (P2) + the document length L2 by the scale “15”, the divided section Y is calculated. If the “resolution estimation section” is Z,
Z = Xm * Y (Formula 1)
Calculate as

  The reason why the “resolution estimation section” is calculated in this way is that the appropriate resolution estimation section depends on the print pattern of the document, and thus needs to be selected by the user. Here, the value of the distance L1 from the back surface CIS position to the front surface CIS position + the document length L2 is the moving distance of the sheet from the start of reading the front end of the back document to the end of reading the rear end of the front document. Depending on user settings, the maximum reading range can be set as the resolution estimation section at the maximum.

4-2. Each Process Related to Reading Now, when the document 5 is conveyed to the first CIS 21 by the conveying roller 33 or the like (step S110), the first CIS 21 starts reading the document back surface 5b (step S115). Next, the ASIC 40 determines whether the rear end position of the resolution estimation section Z is equal to the back surface reading distance based on the document detection signal from the document sensor 38 (step S120). Here, the rear end position of the resolution estimation section Z is determined from the above (Equation 1), and the back surface reading distance (original position) is calculated based on the original detection signal and the like as described above.

If it is determined that the rear end position of the resolution estimation section Z is not equal to the back surface reading distance (step S120: NO determination), the document 5 is further conveyed.
If it is determined that they are equal (step S120: YES determination), the conveyance of the document 5 is stopped (step S125), and the back surface optimum resolution is estimated (step S130).

Here, the estimation of the optimal backside resolution is performed by, for example, a method of binarizing an image and estimating from the size of the continuous area. In this method, the resolution is estimated by determining the size of the “character”.
Specifically, for example, when searching for an image from the upper left to the lower right, continuous regions are detected by labeling. The size of the maximum rectangle surrounding the detected continuous area is calculated, and it is determined whether this rectangle is a character. Then, it is determined whether or not the size of the rectangle determined to be a character is equal to or smaller than a predetermined threshold value. If it is determined to be equal to or smaller than the threshold value, it is estimated as “high resolution”. presume.

  Next, in step S140, a “back and front identical document estimation process” described later is performed. If it is estimated in the “back and front identical document estimation process” (YES in step S145), the ASIC 40 sets the optimum resolution on the back to the reading resolution (step S150).

  On the other hand, when it is estimated in the “back and front same original estimation process” that the front and back originals are not the same (step S145: NO), the ASIC 40 estimates the optimum surface resolution (step S155). The estimation of the optimum surface resolution is the same as the method for estimating the optimum back surface resolution.

  Next, the ASIC 40 compares the optimal resolution of the back surface with the optimal resolution of the front surface, and when the optimal resolution of the back surface is higher than the optimal resolution of the front surface (step S160: YES), the process proceeds to step S150. On the other hand, when the optimal resolution on the back surface is not higher than the optimal resolution on the front surface (step S160: NO), the optimal resolution on the front surface is set as the reading resolution (step S165).

Next, reading and conveyance of the document back surface 5b are resumed (step S170). When reading of the document back surface 5b is completed (step S175: YES), reading and conveyance of the document surface 5a are resumed (step S180).
Then, the ASIC 40 converts the read data of the resolution estimation section Z into data of the optimum resolution (Step S185).

5. Next, the same document estimation process on both sides will be described with reference to the flowcharts of FIGS.

  As shown in FIG. 6, the “front and back same document estimation process” differs depending on whether the print form of the document 5 is “long edge binding” or “short edge binding”. “Long-side binding” is a print mode in which a plurality of read originals 5 are printed and the long side of each original 5 is printed. “Short-side binding” is a plurality of read originals 5. This is a printing form in which the short side of each document 5 is printed.

  The ASIC 40 first determines the print form before performing the “front and back identical document estimation process”. The determination of the print form can be made, for example, by setting the scan original by the user.

  If it is determined that the document 5 is “long edge binding” (step S210: YES), “D process” is performed as “back and front same document estimation process” (step S220). On the other hand, if it is determined that the document 5 is “short edge binding” (step S230: YES), “B process” or “C process” is performed as “back and front same document estimation process” (step S240). Further, when the document 5 is neither “long edge binding” nor “short edge binding” (or when the printing form cannot be limited (determined)), for example, when the reading document 5 is one (step S230: NO), “ Process A "is performed (step S260). In this case, any one of “A process” to “D process” may be performed.

Next, each process will be described.
5-1. "Processing A"
FIG. 7 is a flowchart showing “Process A”.

  The first analysis unit 43 of the ASIC 40 extracts the color used on the document back surface 5b (step S261). The second analysis unit 44 of the ASIC 40 extracts the color used on the document surface 5a (step S262).

The estimation unit 45 of the ASIC 40 estimates whether or not the back side image and the front side image are the same image (the same original) by comparing whether or not the colors of the extracted surfaces are the same. That is, when it is determined that the extracted colors of the respective surfaces are the same (step S263: YES), it is estimated that the document is the same on both sides (step S264). On the other hand, when it is determined that the extracted colors of the respective surfaces are not the same (step S263: NO), it is estimated that the originals are not the same on both sides (step S265).
Here, the color extraction and the color identity determination are performed using, for example, a histogram representing the appearance frequency of each color image. For example, a monochrome original is read in color, and histograms of the back surface and the front surface are created. If the histogram shows a tendency that the appearance frequency of white and black is high on both the back and front surfaces and the appearance frequency of other colors is low, it is estimated that the document is the same on both sides.

5-2. "Processing B"
FIG. 8 is a flowchart showing “Process B”.

  The ASIC 40 determines whether or not the document length is equal to the sum of the back surface reading distance and the front surface reading distance (step S241). If “NO” is determined in step S241, the document 5 is conveyed and reading is resumed (step S242). On the other hand, if “YES” is determined in the step S241, the conveyance and reading of the document 5 are stopped (step S243).

  Next, the first analysis unit 43 of the ASIC 40 extracts one line data of the rear end position of the resolution estimation section Z of the document back surface 5b (step S244). Further, the second analysis unit 44 of the ASIC 40 extracts one line data of the rear end position of the resolution estimation section Z of the document surface 5a (step S245).

  The estimation unit 45 of the ASIC 40 determines whether or not the image on the document back surface 5b and the image on the document surface 5a are the same image (the same document), and whether or not the extracted line data on each surface is the same. Estimate by comparing. In other words, when it is determined that the extracted line data are substantially the same (step S246: YES), it is estimated that the original document is the same on both sides (step S247). On the other hand, if it is determined that the extracted line data do not match (step S246: NO), it is presumed that the originals are not the same on both sides (step S248).

  In step S246, the front line data is collated from the right end to the left end of the document, and the back surface line data is collated from the left end to the right end of the document.

5-3. "C processing"
FIG. 9 is a flowchart showing the “process C”.

  The ASIC 40 determines whether the length obtained by adding the document length + “several lines” is smaller than the sum of the back surface reading distance and the front surface reading distance (step S251). If “NO” is determined in step S251, the document 5 is conveyed and reading is resumed (step S252). On the other hand, if “YES” is determined in the step S251, the conveyance and reading of the document 5 are stopped (step S253).

  Next, the estimation unit 45 of the ASIC 40 determines whether or not the image on the document back surface 5b and the image on the document surface 5a are the same image (the same document) by reading “several lines” on the document back surface 5b and the document surface 5a. Estimate by comparing whether the data are identical. That is, when it is determined that the extracted line data are substantially the same (step S254: YES), it is presumed that the front and back originals are the same (step S255). On the other hand, if it is determined that the extracted line data do not match (step S254: NO), it is estimated that the two originals are not the same on both sides (step S256).

5-4. "Processing D"
FIG. 10 is a flowchart showing the “process D”.

  The first analysis unit 43 of the ASIC 40 extracts several line data of the leading end position of the resolution estimation section Z of the document back surface 5b (step S221). Further, the second analysis unit 44 of the ASIC 40 extracts several line data of the leading end position of the resolution estimation section Z of the document surface 5a (step S222).

  The estimation unit 45 of the ASIC 40 determines whether or not the image on the document back surface 5b and the image on the document surface 5a are the same image (the same document), and whether or not the extracted line data on each surface is the same. Estimate by comparing. That is, when it is determined that the extracted line data are substantially the same (step S223: YES), it is presumed that the original document is the same on both sides (step S224). On the other hand, if it is determined that the extracted line data do not match (step S223: NO), it is presumed that the originals are not the same on both sides (step S225).

6). Effects of the embodiment-
Even when reading of the document back surface 5b is started at the first resolution (600 dpi), the reading process of the document surface 5a at the second resolution (300 dpi), which is lower than the first resolution (600 dpi), is appropriate. If it is determined, the resolution at the time of reading the document surface 5a is switched to the second resolution (300 dpi). Therefore, the reading time can be shortened while suppressing the reading resolution of the document 5 from becoming inappropriate.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.

  (1) The operation unit 12 includes a selection button (an example of a selection unit) for the user to select a reading process for reading a document having a surface to be read at the first resolution and a surface to be read at the second resolution. To do. When this reading process is selected, a display device such as an LCD (an example of a notification unit) may be notified that the surface to be read at the first resolution is set on the ADF 27 as the document back surface 5b. When the reading process is selected, the determination unit 41 determines that the reading process of the document surface 5a at the second resolution is appropriate. In this case, the switching unit 42 sets the first resolution of the document back surface 5b. When the reading process is finished, the resolution at the time of reading the document surface 5a may be switched to the second resolution.

DESCRIPTION OF SYMBOLS 1 ... Multifunction machine 12 ... Operation part 13 ... Reading part 21 ... 1st CIS
22 ... Second CIS
40 ... ASIC
41 ... Determination unit 42 ... Switching unit 43 ... First analysis unit 44 ... Second analysis unit 45 ... Estimation unit 46 ... Conversion unit

Claims (13)

A document transport section for transporting a document;
A reading unit capable of reading the first surface and the second surface of the document conveyed by the document conveying unit;
A determination unit configured to determine whether reading processing of the second side of the document at a second resolution lower than the first resolution at the time of starting the reading processing of the first side of the document is appropriate;
A switching unit that switches the resolution at the time of reading of the second surface to the second resolution when it is determined that the reading processing of the second surface at the second resolution is appropriate;
A document reading apparatus comprising: The document reading device according to claim 1,
A first analysis unit for analyzing the read image of the first surface;
The determination unit determines that the reading process of the second surface at the second resolution is appropriate when the first analysis unit analyzes that the read image of the first surface is a text image. apparatus. In the document reading device according to claim 1 or 2,
The reading unit is
A first reading unit that reads the first surface of the conveyed document at a first reading position;
A second surface that is provided on the downstream side of the first reading unit in the document conveyance direction and reads the second surface, which is the opposite surface of the document having the first surface conveyed from the first reading unit, at a second reading position. A document reading apparatus including two reading units. The document reading apparatus according to claim 3,
A selection unit for a user to select a reading process for reading a document having a surface to be read at the first resolution and a surface to be read at the second resolution;
An informing unit for informing that the surface to be read at the first resolution is set as the first surface in the document conveying unit when the reading process is selected;
The determination unit determines whether the reading process of the second surface at the second resolution is appropriate when the reading process is selected. The document reading device according to claim 4,
The switching unit switches the resolution at the time of reading the second surface to the second resolution when the reading processing of the first surface is completed. The document reading apparatus according to claim 3,
A first analysis unit for analyzing the read image of the first surface;
A second analysis unit for analyzing the read image of the second surface;
An estimation unit for estimating whether the image of the first surface and the image of the second surface are the same image from the analysis result by the first analysis unit and the analysis result by the second analysis unit; In addition,
The determination unit determines that the reading process of the first surface of the document at the second resolution is appropriate from the analysis result of the first analysis unit, and the image of each surface is estimated from the estimation of the estimation unit. A document reading device that determines that reading processing of the second surface at the second resolution is appropriate when it is estimated that the images are the same. The document reading device according to claim 6,
The first analysis unit extracts a color used in the first surface,
The second analysis unit extracts a color used in the second surface,
The estimation unit estimates whether the image of the first surface and the image of the second surface are the same image by comparing whether the colors of the extracted surfaces are the same, Document reader. The document reading device according to claim 6,
The first analysis unit extracts at least one line data of a rear end position of the resolution estimation section of the first surface,
The second analysis unit extracts at least one line data of a rear end position of the resolution estimation section of the second surface;
The estimation unit estimates whether the image of the first surface and the image of the second surface are the same image by comparing whether the extracted line data of each extracted surface is the same. A document reading device. The document reading device according to claim 6,
The first analysis unit extracts several line data of the tip position of the resolution estimation section of the first surface,
The second analysis unit extracts several line data of the tip position of the resolution estimation section of the second surface,
The estimation unit estimates whether the image of the first surface and the image of the second surface are the same image by comparing whether the extracted line data of each extracted surface is the same. A document reading device. In the document reading device according to any one of claims 6 to 9,
The document reading apparatus, wherein the switching unit switches the resolution at the time of reading the first surface to the second resolution when it is determined that the reading process of the second surface at the second resolution is appropriate. The document reading apparatus according to claim 10,
An original reading apparatus, further comprising: a conversion unit that converts an image read at the first resolution into the second resolution. An original reading apparatus according to any one of claims 1 to 11,
An image forming unit that forms an image based on a document read by the document reading device;
An image forming apparatus comprising: An original reading method in an original reading apparatus provided with a reading section capable of reading the first side and the second side of an original,
Judgment to determine whether or not the reading process of the second side of the document at a second resolution lower than the first resolution when the reading unit starts the reading process of the first side of the document is appropriate Process,
A switching step of switching the resolution at the time of reading the second surface to the second resolution when it is determined that the reading processing of the second surface at the second resolution is appropriate by the determining step;
Document reading method including

Images