JP2020102810A - Image reading device and image reading method - Google Patents

Abstract

To prevent a reduction in reading speed and reduce consumption of memory resources when correcting the influence of external light.SOLUTION: An image reading device comprises: a light source that repeatedly turns on and off; a reading unit that outputs line data that is a reading result according to a light reception amount per reading cycle including a lighting period from the turn-on to the turn-off of the light source; and a control unit that controls the light source and the reading unit. The control unit acquires the plurality of pieces of line data output from the reading unit corresponding to the plurality of times of reading cycles having different lengths, and corrects the acquired pieces of line data based on the difference between the acquired pieces of line data.SELECTED DRAWING: Figure 4

Description

The present invention relates to an image reading device and an image reading method.

It is known that when a scanner reads a document by receiving reflected light from the document and transmitted light from the document, the reading result is affected by external light.

Further, when reading image data in which the number of lines in the sub-scanning direction is twice the number of lines in the sub-scanning direction, which corresponds to the output resolution, when reading image data of odd lines in the sub-scanning direction and when reading image data of even lines. A configuration is known in which the light amount of a light source is different when reading image data and the document area in the image data is determined according to the comparison result of the image data of the odd line and the image data of the even line (Patent Document 1). reference).
Further, an image in which a plurality of line data read respectively when the illumination means is turned on and off is stored, and the stored line data when turned on and off is calculated to reduce the influence of external light on the read image. An input device is known (see Patent Document 2).

JP, 2013-115499, A JP-A-8-248529

In Document 1, since it is necessary to read and store the image data having the number of lines twice the number of lines in the sub-scanning direction corresponding to the output resolution, the reading speed of the document is reduced and the image data is also reduced. A large amount of memory is required to store the.
Further, in Document 2, since it is necessary to read and save the line data when the illumination is on and the line data when the illumination is off, the reading speed of the document is reduced and the line data is often saved. Memory capacity is required.
Therefore, when correcting the influence of external light on the reading result, it is required to prevent the reading speed from decreasing and to suppress the consumption of memory resources.

The image reading device includes a light source that repeats lighting and extinguishing, and a reading unit that outputs line data that is a reading result according to the amount of light received in each reading cycle including a lighting period from turning on the light source to turning off the light source. A control unit for controlling the light source and the reading unit, wherein the control unit obtains the plurality of line data output by the reading unit corresponding to the plurality of reading cycles having different lengths. Then, the acquired line data is corrected based on the difference between the acquired line data.

FIG. 3 is a block diagram simply showing the configuration of the image reading apparatus. FIG. 3 is a diagram simply showing a mechanical structure of the image reading apparatus including a conveyance path. The figure for demonstrating the example of a reading cycle. The flowchart which shows the correction process of line data. FIG. 4 is a diagram showing an example of line data for a plurality of lines output from a reading unit.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Each drawing is merely an example for explaining the present embodiment. Since each drawing is an example, it may be inconsistent with each other or may be partially omitted.

1. Schematic configuration of the image reading device:
FIG. 1 simply shows the configuration of an image reading apparatus 100 according to this embodiment.
FIG. 2 simply shows the mechanical structure of the image reading apparatus 100 including the conveyance path 48.
The image reading apparatus 100 is a scanner that can read a document. The image reading apparatus 100 includes a conveyance unit 30 that conveys a document, a reading unit 31 that performs reading, a light source 32 that irradiates a reading target such as a document, an operation panel 33, the conveyance unit 30, and the reading unit 31. The control unit 10 that controls the light source 32 and the operation panel 33 is provided. The operation panel 33 includes a display unit for displaying visual information, an operation receiving unit for receiving an operation from a user, and the like. The operation receiving unit is a touch panel realized on the display unit, a physical button, or the like. The image reading apparatus 100 may be a multifunction machine having a plurality of functions such as a printer in addition to the function as a scanner.

The transport unit 30 is a mechanism for transporting a document from upstream to downstream of the transport, and includes, for example, a roller for transporting the document, a motor for rotating the roller, and the like. The document transported by the transport unit 30 is read by the reading unit 31. Therefore, the image reading apparatus 100 corresponds to a sheet feed scanner. The transport unit 30 may be called an ADF (Auto Document Feeder).

The light source 32 is, for example, an LED (Light Emitting Diode). The reading unit 31 has an image sensor. The image sensor receives the reflected light from the original of the light emitted from the light source 32, accumulates electric charge according to the amount of received light, and sends it to the control unit 10 as image data. The image sensor includes a plurality of sensor chips arranged in the main scanning direction. The main scanning direction is a direction that intersects the document transport direction of the transport unit 30. The term “crossing” as used herein means orthogonality, but it may not only be strict orthogonality but also include an error that may occur due to actual component mounting accuracy or the like. That is, the reading unit 31 is a line image sensor having a length capable of covering the width of the document in the main scanning direction. The main scanning direction is also called the longitudinal direction of the image sensor. The transport direction is also called the sub-scanning direction. In FIG. 2, the main scanning direction is a direction perpendicular to the paper surface of FIG.

Each sensor chip constituting the reading unit 31 has the same configuration as a CIS (Contact Image Sensor) or CCD (Charge Coupled Device) image sensor. That is, each sensor chip includes a photoelectric conversion element, a shift gate, and a shift register. Then, the charge accumulated in the photoelectric conversion element is transferred to the shift register by opening the shift gate, and the charge is output while the charge is sequentially moved by the shift register. The charge of each photoelectric conversion element corresponds to the value of each pixel forming the image data read by the reading operation of the reading unit 31. The image data read by the reading operation of the reading unit 31 is called “line data”.

The opening of the shift gate (transfer of charges) is performed in response to a control signal from the control unit 10. This control signal is called a "shift signal". The charges transferred to the shift register are converted into analog data from the output section at the end of the shift register and output to the AFE (Analog Front End) 20 of the control section 10.

The photoelectric conversion element always accumulates electric charge according to the amount of received light. Therefore, the timing at which the charge of the photoelectric conversion element is transferred in response to the shift signal is the timing at which the photoelectric conversion element starts to accumulate the charge corresponding to the next line data. Therefore, the period from when the control unit 10 outputs the shift signal to the reading unit 31 to when the next shift signal is output is the "reading cycle" of the line data for one line. It can be said that the shift signal is a signal for instructing the reading unit 31 about the timing of the end of one reading cycle and the start of the next reading cycle. That is, the read cycle is switched by the shift signal.

The control unit 10 includes, for example, a CPU that performs main control, a ROM that stores programs and the like, a RAM that temporarily stores data and the like as a main memory, and an ASIC (designed to perform various processes exclusively). Application Specific Integrated Circuit) and other electronic circuit components. The controller 10 may be a SoC (System on a Chip) controller. The control unit 10 has, for example, an AFE 20, an image processing unit 21, a storage unit 22, and an output unit 23. The control unit 10 also includes a motor control unit 11, a reading control unit 12, and a light source drive unit 13.

The motor control unit 11 controls the motor (not shown) included in the conveyance unit 30 by PID control to cause the conveyance unit 30 to convey the document. The reading control unit 12 controls reading by the reading unit 31. That is, the reading control unit 12 outputs a shift signal to the reading unit 31 and controls the transfer of the charges accumulated in the photoelectric conversion element. The light source drive unit 13 controls the turning on and off of the light source 32 by controlling the power supply to the light source 32.

The AFE 20 converts the analog data output from the reading unit 31 into digital data. The image processing unit 21 corrects and outputs the digital data output from the AFE 20. However, the division of roles between the AFE 20 and the image processing unit 21 need not be limitedly understood as described above. The AFE 20 and the image processing unit 21 may be collectively referred to as an AFE, or conversely, the AFE 20 and the image processing unit 21 may be collectively referred to as an image processing unit. The storage unit 22 functions as a buffer that temporarily stores digital data before and after processing by the image processing unit 21. The storage unit 22 sends the digital data processed by the image processing unit 21 to the output unit 23.

The output unit 23 transmits the digital data input from the storage unit 22 to an external information processing device, for example, a host such as a personal computer (not shown). The output unit 23 is realized by, for example, an interface for making a network connection or a USB (Universal Serial Bus) connection. If the image reading apparatus 100 is the above-described multifunction machine, the output unit 23 may output the data to the printer unit that is included in the image reading apparatus 100 and that can execute the printing based on the image data. ..

As shown in FIG. 2, the image reading apparatus 100 includes a main body 40 and a lid 41 that covers a predetermined surface of the main body 40. The lid 41 can be opened and closed with respect to the main body portion 40. A document transport path 48 is secured between the main body 40 and the lid 41. That is, the conveyance unit 30 takes in the original document into the housing of the image reading apparatus 100 from the supply port 42 upstream of the conveyance path 48. Then, the conveyance unit 30 conveys the original taken in from the supply port 42 inside the conveyance path 48 by rotating the rollers 44a, 44b, 45a, 45b and the like, and from the discharge port 43 downstream of the conveyance path 48 to the outside. To discharge. Although not shown, a tray for placing documents before reading is arranged near the supply port 42, and a tray for accumulating documents after reading is provided near the discharge port 43. May be installed.

A predetermined surface of the main body portion 40, that is, a part of the surface facing the lid 41 is composed of a transparent member 46. The transparent member 46 is glass in most cases, but it is a transparent material other than glass. May be. Inside the main body 40, as shown in FIG. 2, a light source 32 and a reading unit 31 are housed. Although omitted in FIG. 2, the control unit 10 is also housed in the main body unit 40. A background plate 47 is disposed on the lid 41 at a position facing the transparent member 46. The background plate 47 is, for example, a white plate member.

The document conveyed on the conveyance path 48 is irradiated by the light source 32 when passing through the position corresponding to the transparent member 46, and the reflected light from the document is incident on the reading unit 31 via the transparent member 46. As is known, the reading unit 31 appropriately has an optical system such as a lens and a mirror in addition to the image sensor, and the light incident on the reading unit 31 via the transparent member 46 is generated by these optical systems. The light is received by the image sensor via.

In FIG. 2, a pair of rollers 44a and 44b that face each other with the transport path 48 interposed therebetween and a pair of rollers 45a and 45b that face each other with the transport path 48 sandwiched are illustrated as some of the rollers that configure the transport unit 30. ing. The roller 44a is arranged on the lid 41, and the roller 44b is arranged on the main body 40. Further, the roller 45 a is arranged on the lid 41, and the roller 45 b is arranged on the main body 40. The rollers 44a and 44b are located upstream of the background plate 47. The rollers 44a and 44b may be called paper feed rollers and the like. The rollers 45a and 45b are located downstream of the background plate 47. The rollers 45a and 45b may be called discharge rollers and the like. Due to the structure of the image reading apparatus 100, external light enters the conveyance path 48 from the supply port 42 and the discharge port 43. Therefore, the reading unit 31 receives not only the light emitted by the light source 32 but also a part of the external light.

The image reading apparatus 100 is not limited to a sheet feed scanner that conveys a document, and may be a flat bed scanner. That is, the image reading apparatus 100 includes the light source 32 and the reading unit 31, or the light source 32 and the optical system which is a part of the reading unit 31, in parallel with the document table such as glass on which the document is placed. The document may be read by moving the document in the scanning direction. The transport unit 30 is not necessary in the configuration of the flatbed scanner. The image reading apparatus 100 may be a product that can read a document in any of a sheet feed scanner and a flatbed scanner.

2. Image reading process:
The control unit 10 causes the motor control unit 11 to start drive control of the transport unit 30 when a scan start instruction is received via the operation panel 33. As a result, the conveyance of the document by the conveyance unit 30 is started. Further, the control unit 10 causes the light source driving unit 13 to start controlling the light source 32, and causes the reading control unit 12 to start controlling the reading unit 31.

FIG. 3 is a diagram for explaining an example of the reading cycle of the reading unit 31. In FIG. 3, the timing at which the reading control unit 12 outputs the shift signal SS to the reading unit 31 is shown along the time axis. The period sandwiched between the shift signal SS and the next shift signal SS is one reading cycle. As can be seen from FIG. 3, the intervals at which the shift signal SS is output are not constant. That is, the reading control unit 12 changes the length of each reading cycle by changing the timing of outputting the shift signal SS to the reading unit 31.

FIG. 3 exemplifies three types of lengths of time T, time T+Δt, and time T−Δt as different lengths of the reading cycle. The following method can be considered as a method of changing the length of the reading cycle.

For example, a plurality of different lengths of the reading cycle are stored in advance in a predetermined memory in the control unit 10. The reading control unit 12 repeatedly generates such previously stored reading cycles of different lengths in the same order. Referring to the example of FIG. 3, the read control unit 12 outputs the shift signal SS so that read cycles of three different lengths of time T, time T+Δt, and time T−Δt are repeatedly generated in this order. Is adjusted and the shift signal SS is output to the reading unit 31.

Alternatively, the reading control unit 12 may repeat the generation of the reading cycle having a length randomly selected from the different lengths stored in advance as described above. That is, the reading control unit 12 generates reading cycles of three different lengths of time T, time T+Δt, and time T−Δt in a random order. In this case, the reading control unit 12 outputs the shift signal SS to the reading unit 31 and then outputs the timing at which the time T−Δt has elapsed, the time T has elapsed, or the time T+Δt has elapsed. The shift signal SS of is output to the reading unit 31.

Needless to say, the length of the reading cycle does not have to be limited to three types as shown in FIG. 3, and may be four or more types or two types.

Alternatively, the reading control unit 12 may repeat generating a reading cycle having a length randomly determined by, for example, generating a random number. In this case, the reading control unit 12 outputs the shift signal SS to the reading unit 31 and then randomly determines the length of time by generating a random number, and at the timing when the determined time elapses, The shift signal SS is output to the reading unit 31.

In FIG. 3, symbol L indicates a lighting period from when the light source 32 is turned on to when the light source 32 is turned off. The length of the lighting period L is constant. Further, the cycle of the lighting period L, that is, the time from the start of the lighting period L to the start of the next lighting period L is constant. In this way, the light source drive unit 13 causes the light source 32 to generate the lighting period L having a constant length at a constant cycle.

Note that the control unit 10 causes the reading period of the reading unit 31 and the lighting period of the light source 32 to be generated, respectively, under the constraint that one lighting period is included in one reading period. Therefore, even when the length of the reading cycle is changed by any of the methods described above, the reading control unit 12 sets the reading cycle of each time to be at least the lighting period L or more. The reading control unit 12 outputs the shift signal SS within the period from the end of the lighting period L to the start of the next lighting period L.

The reading unit 31 outputs line data to the control unit 10 as a reading result corresponding to one reading cycle. That is, the reading unit 31 realizes a reading process of outputting line data which is a reading result according to the amount of received light in each reading cycle including the lighting period. In the reading process, a plurality of line data are output corresponding to a plurality of reading cycles having different lengths. In the control unit 10, the image processing unit 21 acquires the line data sequentially output from the reading unit 31 via the AFE 20, and sequentially stores the acquired line data in the storage unit 22.

FIG. 4 is a flowchart showing the correction processing of line data. This flowchart corresponds to a correction process for correcting line data. That is, the present embodiment discloses an image reading method including a reading process and a correction process. The correction of the line data in the present embodiment is a correction for removing the influence of external light included in the line data.

In step S200, the image processing unit 21 calculates the difference between the line data having different read cycle lengths based on the line data stored in the storage unit 22. The control unit 10 naturally understands the length of each reading cycle based on each timing of the shift signal SS output to the reading unit 31. Therefore, the image processing unit 21 may store the line data output from the reading unit 31 in the storage unit 22 in association with the length of the reading cycle corresponding to the line data.

FIG. 5 shows line data for a plurality of lines output from the reading unit 31. In FIG. 5, the horizontal axis represents the pixel position X, and the vertical axis represents the value (read value Y) for each pixel forming the line data. The read value Y is a value indicating brightness according to the amount of light accumulated in the photoelectric conversion element of the image sensor included in the reading unit 31, and is, for example, brightness. The read value Y is represented by a gradation value in a 256 gradation range of 0 to 255, for example. The pixel position X is a position of a pixel forming line data, and corresponds to a position of the photoelectric conversion element in the main scanning direction of the image sensor.

5, the solid line in the graph shows the line data LD_ _T as reading result corresponding to the single read cycle length is the time T. Further, the one-dot chain line graph of FIG. 5 shows the line data LD_T _+Δt as the reading result corresponding to one read cycle whose length is the time T+Δt, and the two-dot chain line graph has the length _T−Δt . The line data LD_T _-Δt as a reading result corresponding to one reading cycle of _Δt is shown.

The photoelectric conversion element of the reading section 31 basically always receives outside light during the reading cycle. That is, the amount of external light received by the photoelectric conversion element increases within the reading cycle depending on the length of the reading cycle. Further, the photoelectric conversion element also receives the reflected light from the document during the lighting period within the reading cycle. As described in the example of FIG. 3, the length of the lighting period L is constant. Therefore, it can be said that the difference between the line data having different read cycle lengths corresponds to the amount of outside light depending on the difference between the read cycles of the two compared line data.

In step S200, the image processing unit 21 extracts and extracts a combination of two line data having different read cycle lengths from the plurality of line data corresponding to one document stored in the storage unit 22. The difference between the two line data relating to the combination is calculated. Although there is no particular limitation on how many sets of two line data are extracted from the plurality of line data corresponding to one document, it is preferable to extract a plurality of sets.

Using the example of FIG. 5, in step S200, the image processing unit 21 calculates the difference between the line data LD_ _T and line data LD_ _{T +} Δt. The difference between the line data is the difference in the read value Y for each pixel position X when the two line data are compared for each pixel position X.
Similarly, the image processing unit 21 can calculate the difference between the line data LD_T _+Δt and the line data LD_T _−Δt .
Similarly, the image processing unit 21 is capable of calculating the difference between the line data LD_ _T and line data LD_ _T-Δt.

For convenience of explanation, the difference between line data LD_ _T and line data LD_ _{T + Delta] t,} is expressed as the difference _{(LD_ T + Δt -LD_ T)} .
The difference between the line data LD_T _+Δt and the line data LD_T _−Δt is expressed as the difference (LD_T _+Δt− LD_T _−Δt ).
The difference between the line data LD_ _T and line data LD_ _T-Δt, referred to as the difference _{(LD_ T -LD_ T-Δt)} .

In step S210, the image processing unit 21 calculates a data correction amount per unit time from the difference calculated in step S200. The unit time is, for example, seconds.
For example, the difference (LD_ _{T + Δt} -LD_ _T) corresponds to the amount of external light photoelectric conversion element is received during the time Delta] t. Therefore, the image processing unit 21, a difference _{(LD_ T + Δt -LD_ T)} , a value obtained by dividing by Delta] t, the data correction amount α1 per unit time.
Similarly, the difference (LD_T _+Δt− LD_T _−Δt ) corresponds to the amount of outside light received by the photoelectric conversion element during the time 2×Δt. Therefore, the image processing unit 21 sets the value obtained by dividing the difference (LD_T _+Δt− LD_T _−Δt ) by 2×Δt as the data correction amount α2 per unit time.
Similarly, the difference (LD_ _T -LD_ _T-Δt) is equivalent to the amount of external light photoelectric conversion element is received during the time Delta] t. Therefore, the image processing unit 21, a difference _{(LD_ T -LD_ T-Δt)} , a value obtained by dividing by Delta] t, the data correction amount α3 per unit time.

As described above, the difference between the line data is the difference in the read value Y for each pixel position X. Therefore, the image processing unit 21 also calculates the data correction amount per unit time for each pixel position X. Further, the data correction amount per unit time calculated from the difference between the two line data varies depending on the combination of the two line data. Therefore, the image processing unit 21 calculates the average value of the data correction amount per unit time obtained for each difference between the two line data as described above. Then, this average value is set as the data correction amount α per unit time.

For example, the image processing unit 21 sets the average value of the data correction amounts α1, α2, and α3 per unit time as the data correction amount α per unit time. The data correction amount α per unit time is also referred to as an outside light influence value α. Of course, the data correction amounts α1, α2, α3... Per unit time, which are the basis for obtaining the outside light influence value α as such an average value, of the two line data extracted for calculating the difference in step S200. It exists according to the number of groups. The image processing unit 21 also calculates the outside light influence value α for each pixel position X.

Each line data is the result of the reading unit 31 reading a line at a different position in the sub-scanning direction of the document, and the read value Y of each line data is a value that reflects the density of the content (image, character, etc.) of the document. Has become. Therefore, the difference between the line data with different lengths of the reading cycle includes not only the amount of external light depending on the difference of the reading cycle but also the difference according to the difference in the contents due to the position in the document. However, when calculating the difference between the line data having different lengths of the reading cycle, the image processing unit 21 compares the two line data having the positional relationship adjacent to each other in the sub-scanning direction, and thereby, It is possible to suppress as much as possible the difference according to the difference in contents due to the position in the document. This is because there is a high possibility that two line data having a positional relationship that are adjacent to each other in the sub-scanning direction are the result of scanning contents with little difference. Further, as described above, the image processing unit 21 sets the average value of the data correction amounts α1, α2, α3,... As the external light influence value α. This also makes it possible to obtain the outside light influence value α that highly accurately represents the amount of outside light received by the photoelectric conversion element per unit time while suppressing the influence of the content of the original as much as possible.

In step S220, the image processing unit 21 sets each line data stored in the storage unit 22 as a correction target and corrects each line data. In this case, the image processing unit 21 subtracts the product of the outside light influence value α calculated in step S210 and the length of the reading cycle of the line data to be corrected from the line data to be corrected, and thereby the line to be corrected. Correct the data.

As an example, a case of correcting the line data LD_T _+Δt indicated by the alternate long and short dash line in FIG. 5 will be described. The reading cycle of the line data LD_T _+Δt is time T+Δt. Therefore, the image processing unit 21 subtracts the outside light influence value α×time T+Δt from the line data LD_T _+Δt . More specifically, since the outside light influence value α is a value obtained for each pixel position X, the process of subtracting the outside light influence value α×time T+Δt from the read value Y of the line data LD_T _+Δt is performed for the pixel position. Execute every X. As a result, the read value Y of each pixel forming the line data LD_T _+Δt is corrected. It can be said that the corrected line data LD_T _+Δt is line data in which the influence of external light is removed and the density of the document is almost faithfully expressed. The image processing unit 21 similarly performs such correction on each line data corresponding to one document stored in the storage unit 22. With the above, the flowchart of FIG. 4 ends.

The image processing unit 21 stores the corrected line data in step S220 in the storage unit 22. The output unit 23 can output the corrected line data stored in the storage unit 22 to a predetermined output destination. Of course, the image processing unit 21 can repeatedly execute the processing of FIG. 4 for each reading result of a plurality of originals using a plurality of line data corresponding to one original as a unit of the processing of FIG. ..

3. Summary:
As described above, according to the present embodiment, the image reading apparatus 100 responds to the light source 32 that repeats turning on and off and the amount of light received for each reading cycle that includes the lighting period from when the light source 32 is turned on until it is turned off. A reading unit 31 that outputs line data that is a reading result, and a control unit 10 that controls the light source 32 and the reading unit 31 are provided. Then, the control unit 10 acquires a plurality of the line data output by the reading unit 31 corresponding to the plurality of reading cycles having different lengths, and acquires the line data based on the difference between the acquired line data. The line data is corrected.

That is, since the difference between the line data having different lengths of the reading cycle expresses the influence of the external light, the control unit 10 performs correction based on the difference to eliminate the influence of the external light. Can be obtained. Further, according to the above configuration, since the number of lines read by the reading unit 31 is not increased as in the documents 1 and 2, the reading speed of the document does not decrease and the line data of the read number of lines is stored. The memory capacity required for this is smaller than that of the above-mentioned documents 1 and 2.

Further, according to the present embodiment, the control unit 10 causes the light source 32 to generate a lighting period having a constant length at a constant cycle.
According to the above configuration, the length of the lighting period is constant within each reading cycle regardless of the length of the reading cycle. Therefore, the control unit 10 can accurately grasp the influence of the external light received by the reading unit 31 based on the difference between the line data having different reading cycle lengths. Further, according to the above configuration, since the cycle of the lighting period is constant, the reading unit 31 can read the document at regular intervals, although the reading cycle is not constant.

However, the present embodiment may include a mode in which the length of the lighting period included in each reading cycle is not constant. Further, the present embodiment may include a mode in which the cycle of the lighting period is not constant.

Further, according to the present embodiment, the control unit 10 changes the length of the reading cycle by changing the timing of outputting the shift signal for switching the reading cycle to the reading unit 31.
According to the above configuration, the control unit 10 can easily vary the length of the reading cycle by not setting the intervals at which the shift signal is output to the reading unit 31 to be constant.

Further, according to the present embodiment, the control unit 10 calculates a data correction amount per unit time from the difference, and reads the calculated data correction amount per unit time and the line data to be corrected. The line data to be corrected is corrected by the product of the length of the cycle.
According to the above configuration, the control unit 10 can correct the line data with the optimum correction amount for removing the influence of external light according to the length of the reading cycle.

Further, in the present embodiment, a reading step of outputting line data which is a reading result corresponding to the amount of received light in each reading cycle including a lighting period from turning on the light source to turning off the light source, and the output line data And a correcting step of correcting, wherein the reading step outputs a plurality of the line data corresponding to a plurality of reading cycles having different lengths, and the correcting step outputs the line data between the output line data. An image reading method for correcting the line data based on the difference is disclosed.

Further, in the present embodiment, the control unit 10 varies the length of the reading cycle such that the average of the reading cycles of a plurality of times becomes the reading cycle per line corresponding to the set reading speed. , May be used.
The reading cycle per line corresponding to the set reading speed is specifically derived from the carrying speed of the carrying unit 30 and the reading resolution of the reading unit 31 which are preset for the image reading apparatus 100. It is the read cycle per line. The reading resolution of the reading unit 31 is the number of reading lines per inch in the sub-scanning direction. In the example of FIG. 3, it is assumed that the time T is the reading cycle per line corresponding to the set reading speed. In this case, the reading control unit 12 of the control unit 10 changes the reading cycle of each time with, for example, the reading cycle of time T, the reading cycle of time T+Δt, and the reading cycle of time T−Δt at substantially the same frequency. generate. As a result, the length of the reading cycle is on average equal to the time T. As a result, even though the reading cycle is not constant, the speed required for reading the original document is maintained as a result, and the convenience of the user is not impaired.

According to this embodiment, the following actions and effects are also exhibited.
The control unit 10 can obtain the outside light influence value α by applying the present embodiment as one of the initial processes before reading the document. Then, the control unit 10 corrects the shading data used for so-called shading correction for correcting the variation of the output range (black level to white level) for each photoelectric conversion element by using the external light influence value α, and It is possible to perform shading correction on the read value without the influence of external light.
Further, according to the present embodiment, the reading value generated by reading the background outside the document in the line data output from the reading unit 31 is corrected as described above to remove the influence of outside light. Read value. As a result, the accuracy of determination between the original area and the area outside the original can be improved, which is superior to Document 1 described above.

10... Control part, 11... Motor control part, 12... Reading control part, 13... Light source drive part, 20... AFE, 21... Image processing part, 22... Storage part, 23... Output part, 30... Conveying part, 31... Reading unit, 32... Light source, 33... Operation panel, 48... Conveyance path, 100... Image reading device

Claims (6)

A light source that repeatedly turns on and off,
A reading unit that outputs line data that is a reading result according to the amount of received light in each reading cycle including a lighting period from turning on the light source to turning off the light source,
A control unit for controlling the light source and the reading unit,
The control unit acquires a plurality of the line data output by the reading unit corresponding to a plurality of reading cycles having different lengths, and based on a difference between the acquired line data, the acquired An image reading apparatus, which corrects line data. The image reading apparatus according to claim 1, wherein the control unit causes the light source to generate the lighting period having a constant length at a constant cycle. The control unit changes the length of the read cycle by changing the timing of outputting a shift signal for switching the read cycle to the read unit. Image reading device. The control unit calculates a data correction amount per unit time from the difference, and by the product of the calculated data correction amount per unit time and the length of the reading cycle of the line data to be corrected, The image reading apparatus according to claim 1, wherein the line data to be corrected is corrected. The control unit changes the length of the reading cycle such that an average of the reading cycles of a plurality of times is a reading cycle per line corresponding to a set reading speed. The image reading device according to any one of claims 1 to 4. A reading step of outputting line data which is a reading result according to the amount of received light in each reading cycle including a lighting period from turning on the light source to turning off the light source;
A correction step of correcting the output line data,
In the reading step, a plurality of the line data are output corresponding to the plurality of reading cycles having different lengths,
The image reading method, wherein in the correction step, the line data is corrected based on a difference between the output line data.

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