JP2008278276A - Image reading device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading device updating correction data in appropriate timing. <P>SOLUTION: Through standby processing, a read of reflected light from a reference position 21b is suspended until it is determined that it becomes ready to read a document. Namely, after the it becomes ready to read the document, the reflected light is read and gain adjustment and shading correction data are determined. After the gain adjustment and shading correction data are determined, therefore, a next document is read without any delay, so even if the quantity of light changes after gain adjustment and shading correction, influences thereof is suppressed, and suitable corrections are made using the determined shading correction data, and a gain value. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image reading apparatus, and more particularly to an image reading apparatus that can determine correction data at an appropriate timing.

  2. Description of the Related Art Conventionally, an image reading apparatus that reads an image such as a graphic drawn on a document is known. In such an image reading apparatus, a document to be read is irradiated with light from a light source, and reflected light reflected by the document is converted into a plurality of charge coupled devices (hereinafter referred to as “CCD”) arranged in a line in the main scanning direction. The image of the original is read by converting the voltage value into the digital data according to the intensity of the reflected light.

At this time, in order to correct unevenness appearing in the main scanning direction due to a difference in the light amount between the central portion and the end portion of the light source in the main scanning direction, a temporal light amount fluctuation of the light source, and a variation in CCD characteristics, Each time the reading unit is read, the reading unit is returned to the home position, the white reference plate is read by the CCD, light quantity distribution data in the main scanning direction is acquired, and based on the light quantity distribution data, main data of the image data when the original is read is read. Shading correction for correcting unevenness in the scanning direction is performed (see, for example, Patent Document 1). The light amount of the light source varies with time, and the light amount distribution data also varies accordingly. Therefore, in order to perform appropriate shading correction, it is desirable to update the shading correction data as appropriate. For example, when reading a large number of pages one page at a time using an automatic document feeder, the amount of light varies greatly between the time when the first page is read and the time when the last page is read. The correction data may be updated.
JP 2002-330269 A

  However, when reading a multi-page document, the start of reading the next page may be put on standby due to the data processing read in advance. For example, when the data read on the previous page is being transferred to an external device and the data transfer has been completed and the next page starts to be read, or the data read on the previous page When it is configured to start reading the next page after image processing such as encoding and color conversion is completed, it is actually between the end of reading the previous page and the start of reading the next page. It will be kept waiting for a long time. In such a case, if the shading correction data is generated immediately after the reading of one page of the document and the generated shading correction data is used for the correction of the next page, the waiting time until the next page is read. When the amount of light varies greatly, there is a problem that the shading correction data created previously may become inappropriate for the correction of the next page.

  The same problem may occur when the memory for storing the read data is insufficient and the start of reading the next page is put on standby until the memory is secured.

  SUMMARY An advantage of some aspects of the invention is that it provides an image reading apparatus capable of determining correction data at an appropriate timing.

  In order to achieve this object, an image reading apparatus according to claim 1 includes a reading unit that reads reflected light emitted from a light source and reflected by the irradiation target, converts the light into image data, and outputs the image data. The reflected light is obtained by reading the reflected light and using the correction data determining means for determining the correction data based on the acquired image data and the correction data determined by the correction data determining means. A correction means for correcting the image data obtained by reading the image, a state determination means for determining whether or not the original can be read, and the state determination means determine that the original can be read. And a waiting means for waiting for the reflected data to be read by the correction data determining means.

  According to a second aspect of the present invention, there is provided the image reading apparatus according to the first aspect, further comprising a transfer unit that transfers the image data corrected by the correction unit to an external device, and the state determination unit is based on the transfer unit. It is determined that the document can be read on the condition that the amount of untransferred image data is equal to or less than the first threshold value.

  According to a third aspect of the present invention, there is provided the image reading apparatus according to the first aspect, further comprising storage means for storing the image data corrected by the correction means, wherein the state determination means has a free space in the storage means. It is determined that the document can be read on condition that the second threshold value is reached.

  According to a fourth aspect of the present invention, there is provided the image reading apparatus according to the first aspect, further comprising an image processing unit that performs predetermined processing on the image data corrected by the correction unit and outputs the processed image data. The image processing means determines that the document can be read on condition that the processing of the image data of the document read in advance has been completed.

  According to a fifth aspect of the present invention, in the image reading apparatus according to the fourth aspect, the image processing means encodes the image data corrected by the correcting means.

  The image reading apparatus according to claim 6, further comprising a printing unit that prints out the image data corrected by the correction unit in the image reading apparatus according to claim 1, wherein the state determination unit outputs the print output by the printing unit. It is determined that the document can be read on condition that the waiting image data is equal to or less than a predetermined amount.

  The image reading apparatus according to claim 7, further comprising a conveying unit that conveys the document one page at a time to the reading position irradiated with light from the light source. The correction data determining unit is configured such that the trailing end of the one-page document that has been read is conveyed by the conveying unit and passes the reading position, and the leading end of the next page of the document is conveyed by the conveying unit. The reflected light is read in order to determine the correction data before it reaches the reading position after being conveyed.

  An image reading apparatus according to an eighth aspect of the present invention is the image reading apparatus according to the seventh aspect, wherein irradiation target switching means for switching the irradiation target of the light source between the reading position and a reference position at a position different from the reading position. The correction data determining means includes a rear end in the conveyance direction of one page of the document that has been read is conveyed by the conveyance means and passes the reading position, and a leading edge of the next page in the conveyance direction is the conveyance. The irradiation target switching unit switches the irradiation target of the light source to the reference position, and the reflection is reflected by the reading unit in a state where the reference position is set as the irradiation target of the light source. Image data is acquired by reading light, and correction data is determined based on the acquired image data.

  The image reading apparatus according to claim 9 is the image reading apparatus according to claim 8, wherein the correction data is determined by the correction data determining means, and the correction data is determined by the correction data determining means. Correction data updating means for updating the correction data storage means with the determined correction data each time, and the trailing end in the conveyance direction of one page of the document that has been read is conveyed by the conveyance means to the reading position. And the inter-page reading unit that reads reflected light by the reading unit and obtains image data in a state where the reading position is set as an irradiation target of the light source, and the correction data determining unit includes the inter-page reading unit. When the image data acquired by the reading unit satisfies a predetermined condition, the reference light is reflected by the irradiation target switching unit as the irradiation target. The image data is acquired by reading, and the correction data is determined based on the acquired image data. The correction unit reads the image data using the correction data stored in the correction data storage unit. It is characterized by correcting the obtained image data.

  The image reading device according to claim 10 is the image reading device according to claim 9, wherein the correction data determining unit acquires image data with the reference position as a light source irradiation target, and then the irradiation target switching unit performs the reading. A correction data acquisition unit that reads reflected light with a position as a light source irradiation target to acquire image data, and the inter-page reading unit for the image data acquired at the time of the previous correction data determination by the correction data acquisition unit Change determination value determining means for determining a change determination value indicating a change amount of the image data acquired by the step, and change determination means for determining whether the change determination value determined by the change determination value determination means is outside the third range; The correction data determining means includes the correction data determining means when the change determining means determines that the change determination value is outside the third range. Acquires image data by reading reflected light the reference position as an irradiation target by the target switching means, characterized in that to determine the correction data based on the obtained image data.

  An image reading apparatus according to an eleventh aspect is the image reading apparatus according to the tenth aspect, wherein the correction-time data acquisition unit is configured to detect a predetermined range at the reading position every time correction data is determined by the correction data determination unit. The image data is acquired, and every time the image data is acquired for the predetermined range by the correction data acquisition means, a value corresponding to the maximum luminance is stored among the acquired image data. The luminance storage unit and the inter-page reading unit acquire image data for the predetermined range each time the trailing end in the conveyance direction of one page of the document that has been read is conveyed by the conveyance unit and passes the reading position. Each time image data is acquired for the predetermined range by the inter-page reading unit, the acquired image data An inter-page maximum luminance storage unit for storing a value corresponding to the maximum luminance, and the change determination value determining unit is configured to determine the inter-page relative to the value corresponding to the maximum luminance stored in the correction maximum luminance storage unit. A value indicating a change amount of a value corresponding to the maximum luminance stored in the maximum luminance storage means is determined as the change determination value.

  An image reading apparatus according to a twelfth aspect of the invention is the image reading apparatus according to the tenth or eleventh aspect, wherein the reading means reads the reflected light, photoelectrically converts it to output an image signal, and the imaging means. An image signal correction unit that corrects an output image signal using an image signal correction value, and a conversion unit that A / D converts the image signal corrected by the image signal correction unit into digital data. The image signal correction value storage means for storing the image signal correction value, and the image signal correction value stored in the image signal correction value storage means at the time of reading the image of the document by the reading means, When the change determination value is within the third range and out of the fourth range by the correction value setting unit set as an image signal correction value used by the correction unit and the change determination unit. A temporary correction value determining means for determining a temporary image signal correction value on the basis of the change judgment value and the image signal correction value stored in the image signal correction value storage means, The value setting means uses the provisional image signal correction value as the image signal when reading a document of a predetermined number of pages to be read after the provisional image signal correction value is determined by the provisional correction value determination means. It is set as an image signal correction value used by the correction means.

  The image reading device according to claim 13 is the image reading device according to claim 12, wherein the correction value setting means reads the image data when the image data is read by the inter-page reading means and the correction time data acquisition means. At this time, a predetermined correction value for determination is set as an image signal correction value used by the image signal correction means.

  According to the image reading apparatus of the first aspect, since the reflected data is read by the correction data determining means until it is determined that the original can be read, the correction data is determined at an appropriate timing. There is an effect that can be done. That is, since the original is quickly read after the correction data is determined, appropriate correction can be performed using the determined correction data.

  According to the image reading apparatus of the second aspect, in addition to the effect achieved by the image reading apparatus of the first aspect, even if the reading of the document is not started immediately due to accumulation of untransferred image data, There is an effect that the correction data can be determined at a proper timing.

  According to the image reading apparatus of the third aspect, in addition to the effect produced by the image reading apparatus of the first aspect, even if the free space of the storage means is not sufficient and the reading of the document is not started immediately, There is an effect that the correction data can be determined at a proper timing.

  According to the image reading apparatus of the fourth aspect, in addition to the effect of the image reading apparatus of the first aspect, it takes time to process the image data of the previously read document, and the next document can be read immediately. Even if it is not started, there is an effect that correction data can be determined at an appropriate timing.

  According to the image reading apparatus of the fifth aspect, in addition to the effect of the image reading apparatus of the fourth aspect, it takes time to encode the image data of the previously read document, and the next document can be read. Even if it is not started immediately, the correction data can be determined at an appropriate timing.

  According to the image reading apparatus of the sixth aspect, in addition to the effect of the image reading apparatus of the first aspect, it takes time to print out the image data read in advance, and the next original is immediately read. Even if it is not started, there is an effect that correction data can be determined at an appropriate timing.

  According to the image reading device of the seventh aspect, in addition to the effect produced by the image reading device according to any one of the first to sixth aspects, after passing the reading position of the previous page, the time until the next page reaches the reading position. Time is effectively used, and the time required for the reading process can be suppressed.

  According to the image reading apparatus of the eighth aspect, in addition to the effect produced by the image reading apparatus of the seventh aspect, it is possible to determine appropriate correction data based on the reflected light from the reference position that is not easily soiled by the document. There is an effect that can be done. In this case, the irradiation target of the light source is switched to determine correction data. This switching is performed using the time until the next page reaches the reading position after passing the reading position of the previous page. Therefore, there is an effect that the time required for the reading process can be suppressed.

  Preferably, the irradiation target switching means moves the light source to a position where the reading position is irradiated or a position where the reference position is irradiated. Therefore, by updating the correction data at an appropriate timing, the number of times the light source reciprocates between the reading position and the reference position can be reduced, and the time required for the reading process can be suppressed.

  Further preferably, the image reading apparatus includes a light transmitting means for placing a document to be read and transmitting light emitted from a light source, and light irradiated to a reading position from the reading means via the light transmitting means. Reflecting means for reflecting the light to the reading means. In this way, the correction is performed when the image data obtained by irradiating the reflecting means with the irradiating light through the light transmitting means on which the document is placed and reading the reflected light from the reflecting means satisfies a predetermined condition. Since the data is determined and the correction data storage means is updated, the correction data can be determined at a more appropriate timing according to the image data obtained from the actual reading area.

  Further, the reflecting means may be one that presses the document to be read toward the light transmitting means at the reading position. In this way, the reflecting means can also be used as a document presser, and the number of parts can be reduced.

  According to the image reading apparatus of the ninth aspect, in addition to the effect achieved by the image reading apparatus of the eighth aspect, there is an effect that the correction data can be updated at a more appropriate timing. Preferably, the inter-page reading unit reads the reflected light from the reflection unit by the reading unit in a state where the reading position is the light source irradiation target, and acquires image data.

  According to the image reading device of the tenth aspect, in addition to the effect achieved by the image reading device according to the ninth aspect, the correction data is read at an appropriate timing when it is determined that the amount of change in light amount from the previous correction data determination is large. There is an effect that the update can be performed. Preferably, the correction data acquisition unit acquires image data by reading the reflected light from the reflection unit by the reading unit in a state where the reading position is the light source irradiation target.

  According to the image reading device of the eleventh aspect, in addition to the effect produced by the image reading device of the tenth aspect, there is an effect that the change judgment value can be determined by an appropriate and easy process. In other words, the maximum luminance of the light amount is likely to fluctuate due to the influence of the change in the light source over time, so by using the value corresponding to the maximum luminance in the acquired image data for the determination of the light amount change amount, It is possible to easily determine a change judgment value that appropriately reflects the degree of fluctuation.

  According to the image reading device of claim 12, in addition to the effect achieved by the image reading device of claim 10 or 11, even when there is a light amount fluctuation of the light source, without switching the irradiation target of the light source, There is an effect that it is possible to determine an appropriate temporary image signal correction value, correct the image signal using the appropriate image signal correction value, and suppress the influence of the light amount fluctuation of the light source.

  According to the image reading apparatus of the thirteenth aspect, in addition to the effect achieved by the image reading apparatus of the twelfth aspect, even if the light amount largely fluctuates after the previous determination of the image signal correction value, regardless of the fluctuation. There is an effect that image data for determining an appropriate change judgment value can be acquired.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows an external configuration of an image reading apparatus 1 according to an embodiment of the present invention, and FIG. 2 shows a main internal configuration of the image reading apparatus 1. The image reading device 1 is a device that functions as a scanner device that transfers read data to an external device and a copy device that prints out the read data.

  As shown in FIGS. 1 and 2, the image reading apparatus 1 has an auto document feeder (ADF) that is an automatic document feeder mechanism with respect to a document table 2 that functions as an FBS (Flatbed Scanner). A document cover 4 having 3 is attached so as to be openable and closable via a hinge on the back side (back of the paper surface).

  An operation panel 5 is provided on the front side of the document table 2. The operation panel 5 includes various operation keys 11 and a liquid crystal display unit 12. The image reading apparatus 1 receives a predetermined input from these operation panels 5 and performs a predetermined operation. The image reading apparatus 1 is operated not only by a command input to the operation panel 5 but also by a command connected to the computer and transmitted from the computer via a printer driver, a scanner driver, or the like.

  As shown in FIG. 2, a platen glass 21 is disposed on the top surface of the document table 2 that faces the document cover 4. An image reading unit 22 is built in the document table 2 so as to face the platen glass 21.

  The platen glass 21 is made of, for example, a transparent glass plate, and when the ADF 3 of the image reading apparatus 1 is used, a reading position 21a where a document is placed, and a reference position where the document is not located at a position different from the reading position 21a. 21b. This platen glass 21 corresponds to an example of the light transmitting means of the present invention. An opening for exposing the platen glass 21 is formed at the reading position 21 a of the document table 2. The platen glass 21 exposed from the opening is extended in the depth direction of the image reading apparatus 1 corresponding to the length of the image reading unit 22 in the main scanning direction.

  Above the reading position 21 a of the platen glass 21, a document presser 19, which is an example of a reflection unit, is disposed to face the platen glass 21. The document retainer 19 always moves downward in FIG. 2 due to its own weight or under the urging force of an elastic member such as a spring. Further, the document holder 19 extends in the depth direction of the image reading apparatus 1 corresponding to the length of the image reading unit 22 in the main scanning direction. Therefore, the document conveyed to the reading position 21a via the document conveyance path 32 described later is pressed to the platen glass 21 side by the document pressing unit 19 to improve the adhesion between the platen glass 21 and the document.

  On the other hand, a white tape 21 c is attached to the upper surface of the reference position 21 b of the platen glass 21. As a result, the white tape 21c and the reference position 21b of the platen glass 21 can function as a white reference plate for gain adjustment and shading correction data creation. The white tape 21c is an example of a density reference plate. The gain adjustment and shading correction will be described later.

  The image reading unit 22 irradiates light upward from the light source through the platen glass 21, collects reflected light from the irradiation target on the light receiving element by the lens, and outputs it as an image signal. The image reading unit 22 is provided so as to be able to reciprocate below the platen glass 21 by a belt driving mechanism that is a scanning mechanism, and reciprocates in parallel with the platen glass 21 under the driving force of the carriage motor.

  In particular, the image reading unit 22 moves below the reading position 21 a when reading a document fed by the ADF 3 below the platen glass 21. As shown in FIG. 2, when the image reading unit 22 is arranged below the reading position 21a, the light emitted from the image reading unit 22 passes through the platen glass 21 and is arranged at the reading position 21a. The original is irradiated.

  The surface of the document retainer 19 that faces the platen glass 21 is white. When the document is not at the reading position 21 a, the document holder 19 reflects the irradiation light from the image reading unit 22 below the platen glass 21 to the image reading unit 22. According to the image reading apparatus 1 of the present embodiment, the reflected light from the document holder 19 is read by the image reading unit 22 and the amount of light quantity change is evaluated based on the digital data obtained as a result. That is, the number of parts is reduced by causing the document retainer 19 to function as a document retainer and also as a reflecting means.

  FIG. 3 is a diagram illustrating a state in which the image reading unit 22 has moved below the reference position 21b. As shown in FIG. 3, the image reading unit 22 that has moved downward below the reference position 21b irradiates the reference position 221b with light and reads the reflected light from the reference position 21b. The white tape 21c attached to the reference position 21b functions as a white reference plate. Therefore, when determining shading correction data to be described later, a digital obtained by reading reflected light from the white tape 21c is used. Shading correction data is determined using the data. Here, since the white tape 21c is arranged at a position separated from the reading position 21a, it is possible to suppress contamination from a document or the like, and appropriate shading correction data is determined.

  Returning to FIG. 1 and FIG. The document cover 4 includes an ADF 3 that continuously conveys documents from the paper feed tray 30 to the paper discharge tray 31 through the document conveyance path 32. In the conveyance process by the ADF 3, the document passes through the reading position 21 a on the platen glass 21, and the image reading unit 22 waiting under the platen glass 21 reads the image of the document.

  As shown in FIG. 2, in the ADF 3, a paper feed tray 30 and a paper discharge tray 31 are connected to each other via a reading position 21 a on the platen glass 21, and are substantially U-shaped in the horizontal direction in a vertical sectional view. A document conveyance path 32 is formed. The document transport path 32 is continuously formed as a passage having a predetermined width through which a document can pass by members, guide plates, guide ribs, and the like constituting the ADF main body.

  In the document conveyance path 32, a suction roller 33 and a separation roller 34 for feeding documents from the paper feed tray 30 to the document conveyance path 32, and a document fed to the document conveyance path 32 are conveyed to the sheet discharge tray 31. And conveying means for carrying out the operation. Specifically, as shown in the drawing, the conveyance rollers 35A, 35B, 35C, and 35D provided in the document conveyance path 32 and the pinch roller 37 that press-contacts them correspond to an example of the conveyance unit.

  As shown in FIG. 2, the document transport path 32 is provided with a plurality of sensors for detecting document transport. Specifically, a first front sensor 52 and a second front sensor 53 are disposed on the upstream side and the downstream side of the separation roller 34 in the document transport path 32, respectively, and also immediately upstream of the reading position 21a. A rear sensor 54 is disposed on the rear side. Each of these sensors is a so-called optical sensor that detects the rotation of the detector that appears and disappears in the document conveyance path 32 as on / off of the photo interrupter.

  When a document is placed on the paper feed tray 30, the first front sensor 52 is turned on. Whether the document is placed on the paper feed tray 30 is detected by turning on / off the first front sensor 52. The second front sensor 53 disposed immediately downstream of the separation roller 34 is for detecting the leading edge or trailing edge of the document fed to the document conveying path 32 by turning on / off thereof. For example, the number of rotations of the conveying rollers 35A, 35B, 35C, and 35D after the second front sensor 53 detects the trailing edge of the document is monitored by the number of steps of the encoder or motor, and the like. The position of the front end or the rear end is determined.

The rear sensor 54 disposed immediately upstream of the reading position 21a is for detecting the leading edge and the trailing edge of the document conveyed on the document conveyance path 32 by turning on / off thereof. The transport rollers 35A, 35B, 35C, and 35D after the rear sensor 54 detects the leading edge or trailing edge of the document.
The number of rotations is monitored by the number of steps of the encoder or motor, and it is determined whether or not the leading edge or trailing edge of the document has reached the reading position 21a. Image reading of the image reading unit 22 is controlled based on a signal from the rear sensor 54. Image reading is started when the leading edge of the document reaches the reading position 21a, and image reading is performed when the trailing edge of the document reaches the reading position 21a. Reading is terminated.

  With reference to FIG. 4, the configuration of the image reading unit 22 and the outline of the flow of signals output from the image reading unit 22 will be described. FIG. 4A is a diagram illustrating a schematic configuration of an ASIC 66 that is an example of an image reading unit 22 and a correction unit that processes data output from the image reading unit 22.

  As shown in FIG. 4, the image reading unit 22, which is an example of a reading unit, includes, for example, a light source 22 a configured by a cold cathode tube and a CCD (Charge) that covers a main scanning range that is at least the long side of the platen glass 21. The image sensor 22b which is an example of the imaging means comprised with the coupled device) image sensor, and AFE (analog front end IC) 22c are provided. According to the image reading unit 22, the reflected light obtained by reflecting the irradiation light from the light source 22a by the irradiation target is read by the image sensor 22b. The image sensor 22b photoelectrically converts the reflected light and outputs an image signal to the AFE 22c. In the AFE 22 c, the image signal is A / D converted into digital data and output to the ASIC 66. Digital data output to the ASIC 66 corresponds to an example of image data. Note that the image sensor 22b may be formed of other types of image sensors such as a contact type CIS (Contact Image Sensor) image sensor. Further, an A / D converter or the like may be used instead of AEF.

  The digital data output from the image reading unit 22 to the ASIC 66 is first black-corrected by the black correction unit 66a of the ASIC 66. The digital data black-corrected by the black correction unit 66 a is then subjected to shading correction by the shading correction unit 66 b of the ASIC 66. Here, the shading correction means that the shading correction data set for each pixel in the main scanning direction is converted into the digital data for each pixel in order to correct the dispersion of the digital data for each pixel in the main scanning direction during white reading. It is a process to multiply.

  FIG. 5 is a graph showing the relationship between the image signal output from the image sensor 22 during white reading and the position in the main scanning direction at the reading position 21a. According to this graph, it can be seen that a high value is obtained at the central portion in the main scanning direction, while a relatively low value is obtained at both ends in the main scanning direction. Furthermore, in addition to variations in the amount of light from the light source 22a, there is also non-uniformity in the sensitivity of the image sensor 22b in the main scanning direction, so that the image signal of each pixel is non-uniform even during white reading. As a result, in the case of no shading correction, even when reading white, if the image signal output from the image reading unit 22 corresponding to each pixel is digitized without correction, the digital data corresponding to each pixel Is not a predetermined maximum reference value (for example, 255). Therefore, the variation in the main scanning direction is made uniform by shading correction.

  Returning to FIG. The data subjected to the shading correction by the shading correction unit 66b is further output to the image processing unit 66c of the ASIC. The digital data is stored in the image memory 63k of the RAM 63 after being subjected to various processes such as a color conversion process from RGB to YCbCr and an encoding process for encoding and compressing with JPEG in the image processing unit 66c.

  FIG. 4B is a diagram illustrating a schematic configuration of the AFE 22c. As shown in FIG. 4B, the AFE 22c includes a gain correction unit 22c1 that is an example of an image signal correction unit, and an A / D conversion unit 22c2 that is an example of a conversion unit. The gain correction unit 22c1 amplifies the image signal output from the image sensor 22b according to the gain value, and outputs the amplified signal to the A / D conversion unit 22c. In the gain correction unit 22c, the image sensor 22b is adjusted according to the gain value adjusted so that the value obtained by amplifying the image signal obtained at the time of reading white matches the maximum reference value of the A / D conversion unit 22c2. The image signal output from is amplified and output. The gain value that determines the amplification factor of the image signal in the gain correction unit 22c1 corresponds to an example of the image signal correction value of the present invention.

  The A / D conversion unit 22c2 compares the analog image signal whose gain has been corrected by the gain correction unit 22c with a predetermined reference value, and performs A / D conversion to, for example, digital data of 00h to FFh (hexadecimal number) and outputs it. To do.

  According to the image reading apparatus 1 of the present embodiment, first, the image reading unit 22 is moved below the reference position 21b (see FIG. 3), reads the white tape 21c, and as a result, an image output from the image sensor 22b. The gain is adjusted based on the signal to determine the gain value. When the gain value is determined, the gain value is set in the gain correction unit 66a, and the image signal from the image sensor 22b is gain-corrected by the gain correction unit 66a and input to the A / D conversion unit 22c2. Converted to digital data.

  Then, based on the digital data output from the image reading unit 22, black correction data and shading correction data are determined and set in the black correction unit 66a and the shading correction unit 66b, respectively. After these settings are made, the image reading unit 22 is moved below the reading position 21a (see FIG. 2) to read the original, and the image signal obtained by reading the original is subjected to gain correction, A / D conversion, black correction, shading correction, and other various image processing are performed and stored in the image memory 63k.

  FIG. 6 shows a configuration of the control unit 60 of the image reading apparatus 1. The control unit 60 controls not only the ADF 3 but also the entire operation of the image reading apparatus 1. As shown in the figure, the control unit 60 is configured as a microcomputer including a CPU 61, a ROM 62, a RAM 63, and an EEPROM (Electrically Erasable and Programmable ROM) 64, and an ASIC (Application Specific Integrated Circuit) via a bus 65. 66.

  The ROM 62 stores a program for controlling various operations of the image reading apparatus 1 and the ADF 3. The ROM 62 includes an untransferred data amount threshold value 62a that is an example of a first threshold value, a free space threshold value 62b that is an example of a second threshold value, a light amount change determination gain value 62c that is an example of a determination correction value, and a third range. 62d and the fourth range 62e are stored. These values will be described later with reference to FIG.

  The RAM 63 is used as a storage area or a work area for temporarily storing various data used when the CPU 61 executes the program. The RAM 63 includes a correction gain value storage area 63a, a white level data storage area 63b, a shading correction data storage area 63c, a black level data storage area 63d, a black correction data storage area 63e, and a correction A / D data maximum luminance storage area. 63f, an inter-page A / D data maximum luminance storage area 63g, an A / D data maximum luminance change rate storage area 63h, a temporary gain value storage area 63i, a scan page number counter 63j, and an image memory 63k are provided.

  The correction gain value storage area 63a is an example of an image signal correction value storage means. When determining shading correction data, the gain value determined by the gain adjustment immediately before the determination is stored as a correction gain value. It is an area to do. The correction gain value stored in the correction gain value storage area 63a is set in the gain correction unit 22c1 (see FIG. 4B). Therefore, the image signal output from the image sensor 22b is gain-corrected using the correction gain value.

  The white level data storage area 63b is digital data obtained by the image reading unit 22 that has been moved below the reference position 21b and obtained from the light source with respect to the full width in the main scanning direction as reflected light applied to the white tape 21c as a white reference plate. This area is stored as white level data. As described above, the reference position 21b of the platen glass 21 functions as a white reference plate. Therefore, the shading correction to be multiplied by the digital data for each pixel so that the white level data stored in the white level data storage area 63b can be equalized to the maximum reference value (for example, 255) at the time of white reading. Data is determined for each pixel.

  The shading correction data storage area 63c is an example of correction data storage means, and is an area in which shading correction data determined based on the white level data is stored. The shading correction data stored in the shading correction data storage area 63c is set in the shading correction unit 66b (see FIG. 4A). Therefore, shading correction is performed using this shading correction data.

  The black level data storage area 63d uses, as black level data, digital data acquired using the image sensor 22b provided in the light-shielding area where the reflected light does not enter, among the image reading unit 22 moved below the reference position 21b. This is the memory area. Based on the black level data, black correction data to be subtracted from the digital data output from the image reading unit 22 is determined.

  The black correction data storage area 63e is an area for storing black correction data determined based on black level data. The black correction unit 66a (see FIG. 4A) of the ASIC 66 performs black correction on the digital data output from the image reading unit 22 based on the black correction data stored in the black correction data storage area 63e. As a characteristic of the image sensor 22b, there is an output of a dark output level even when there is no light input. Therefore, black correction data is subtracted from the output of the image reading unit 22 by black correction. The black correction data is newly determined at the same timing as the determination of the shading correction data described above, and the value is updated.

  The corrected A / D data maximum luminance storage area 63f is an example of a corrected maximum luminance storage means, and is an area for storing the corrected A / D data maximum luminance. The A / D data maximum luminance at the time of correction is a value corresponding to the maximum luminance among the digital data for one line acquired after the shading correction data is determined.

  The inter-page A / D data maximum luminance storage area 63g is an example of the inter-page maximum luminance storage means, and the rear end of the one-page original in the conveyance direction passes through the reading position 21a and the next page is read. The document presser 19 is moved by the image reading unit 22 below the reading position 21a until the leading end of the original in the conveying direction is conveyed and reaches the reading position 21a, that is, between pages where no original is placed at the reading position 21a. This is an area for storing a value corresponding to the maximum luminance among the digital data acquired by reading the reflected light from the A / D data maximum luminance between pages.

The A / D data maximum luminance change rate storage area 63h is an area for storing the A / D data maximum luminance change rate indicating the amount of change in inter-page A / D data maximum luminance with respect to the corrected A / D data maximum luminance. is there. Specifically, for example, a value calculated by the following formula (1) is calculated as the A / D data maximum luminance change rate and stored in the A / D data maximum luminance change rate storage area 63h.
A / D data maximum luminance change rate = {(A / D data maximum luminance between pages ÷ A / D data maximum luminance during correction) −1} × 100 (1)

  With reference to FIG. 7, the change in the amount of light over time of the light source 22a will be described in more detail. FIG. 7 is a graph showing the relationship between the image signal output from the image sensor 22b and the position in the main scanning direction at the reading position 21a. The image signal read at the previous determination of shading correction data is indicated as G1. An image signal read after a predetermined time has elapsed since the previous shading correction is a graph indicated as G2. As shown in FIG. 7, the image signal (G2) read after a lapse of a predetermined time generally has a higher output from the image sensor 22b than the image signal (G1) read during the previous shading correction. I understand that This is due to the increase in the amount of light from the light source 22a over time.

  Further, according to the graph shown in FIG. 7, the value fluctuates more greatly in the center in the main scanning direction where the image signal shows a higher value than in the main scanning direction both ends where the image signal shows a lower value. I understand. In other words, when the maximum luminance read at the present time greatly fluctuates with respect to the maximum luminance read at the time of determining the previous shading correction data, it is determined that the amount of light from the light source 22a also largely fluctuates as a whole. can do. On the other hand, when the change amount of the maximum luminance is small, it can be determined that the amount of light from the light source 22a does not vary greatly as a whole.

  Therefore, according to the image reading apparatus 1 of the present embodiment, the change amount of the inter-page A / D data maximum luminance acquired at the current time with respect to the correction-time A / D data maximum luminance acquired when the previous shading correction data was determined. On the basis of the maximum luminance change rate of A / D data indicating the amount of change in light quantity from the time when the previous shading correction data is determined until the present time is evaluated.

  Specifically, the calculated maximum A / D data luminance change rate is compared with the third range 62d (see FIG. 6), and if the A / D data maximum luminance change rate is outside the third range 62d, It is determined that the amount of change in the amount of light since the determination of the shading correction data is large, the image reading unit 22 is moved below the reference position 21b, the reflected light from the white tape 21c is read, and the shading correction data is newly determined and updated. . The third range 62d is set to, for example, −5% or more and + 5% or less.

  On the other hand, when the A / D data maximum luminance change rate is within the third range 62d, according to the image reading apparatus 1 of the present embodiment, the image reading unit 22 is kept waiting at the reading position 21a. That is, the image reading unit 22 is not returned to the lower side of the reference position 21b, and gain adjustment and shading correction data are not updated. Therefore, when the light amount change amount is small, it is not necessary for the image reading unit 22 to reciprocate between the reading position 21a and the reference position 21b, so that the time required for the reading process can be shortened.

  However, even when the A / D data maximum luminance change rate is determined to be within the third range 62d, if it is determined to be outside the fourth range 62e (see FIG. 6), It can be determined that a certain amount of light intensity fluctuation has occurred since the time of shading correction data determination. Therefore, according to the image reading apparatus 1 of the present embodiment, it is an example of a temporary image signal correction value from the correction gain value and the A / D data maximum luminance change rate stored in the correction gain value storage area 63a. Calculate the temporary gain value. The fourth range 62e is a range narrower than the third range 62d, and is set to, for example, -2% or more and + 2% or less.

  Returning to FIG. The temporary gain value storage area 63i is an area for storing a temporary gain value calculated from the correction gain value and the A / D data maximum luminance change rate. As described above, the gain correction unit 22c1 is set with the gain value stored in the correction gain value storage area 63a. The document for five pages after the temporary gain value is determined (claims) For example, the temporary gain value is set in the gain correction unit 22c1 (see FIG. 4B), and an image is obtained using the temporary gain value. The gain of the image signal output from the sensor 22b is corrected.

  In this way, even if there is a light amount variation of the light source 22a, an appropriate temporary gain value corresponding to the light amount variation is determined without moving the image reading unit 22 below the reference position 21a. The image signal can be gain corrected using an appropriate temporary gain value.

  The scan page number counter 63j is a counter that counts the number of pages that have been read.

  The image memory 63k is a memory in which digital data subjected to black correction, shading correction, and other image processing in the ASIC 66 is stored. The digital data stored in the image memory 63k is transferred to an external device set in advance according to an instruction from the user.

  The EEPROM 64 is a storage area for storing various settings, flags, and the like that should be stored even after the power is turned off. In addition to the above-described black correction and shading correction, the ASIC 66 further follows the suction roller 33, the separation roller 34, the transport rollers 35A, 35B, 35C, and 35D, the paper discharge roller 36, and the switchback roller (SB) according to a command from the CPU 61. A motor (not shown) for applying a driving force to the roller 43 is controlled.

  Connected to the ASIC 66 is an image reading unit 22 for reading an image of a document conveyed to the reading position 21a by the ADF 3. Based on the control program stored in the ROM 62, the image reading unit 22 reads an image of the document. Although not shown in the drawing, a drive mechanism for reciprocating the image reading unit 22 is also operated in response to an output signal from the ASIC 66.

  A network I / F 55 (I / F 55) is connected to the ASIC 66. The I / F 55 connects the image reading apparatus 1 to a network and controls data input / output with an external apparatus via the network. In a read data transfer process (see FIG. 8), which will be described later, through this I / F 55, the digital data acquired by the image reading unit 22 and stored in the image memory 63k is transferred to an external device such as a personal computer. .

  The image forming unit 56 includes a so-called ink jet printer that includes a transport mechanism for transporting recording paper and an ink jet head that includes a plurality of nozzles and actuators. When the user designates the copy function from the operation panel 5 and reads the document, the digital data acquired by the image reading unit 22 and accumulated in the image memory 63k is transferred to the image forming unit 56. . The image forming unit 56 prints out the received digital data on a recording sheet.

  Next, the read data transfer process executed in the image reading apparatus 1 configured as described above will be described with reference to the flowcharts of FIGS.

  FIG. 8 is a flowchart of read data transfer processing executed by the image reading apparatus 1. This read data transfer process is started when a document is placed on the paper feed tray 30 of the ADF 3, the transfer destination of the read digital data is set by the user, and “Start” is input using the operation keys 11. First, the image reading unit 22 is moved below the reference position 21b (S2). Next, it waits until the light source 22a of the image reading unit 22 is stabilized (S4). Specifically, it is determined that the light source 22a is stable on the condition that the amount of fluctuation per unit time of the amount of light emitted from the light source 22a is equal to or less than a predetermined value. If a sufficient time has elapsed after the power is turned on, it may be determined that the light source 22a is stable, and the process of S4 may be skipped.

  Next, the value of the scan page number counter 63j is set to “0” (S5), and the supply of the document placed on the paper feed tray 30 of the ADF 3 is started (S6). Then, a correction data full determination process (S10) is executed. This correction data full determination process (S10) is a process of performing gain adjustment, black correction data determination, and shading correction data determination in the gain correction unit 22c1, and details will be described later with reference to FIG.

  Next, it is determined whether the leading end of the supplied document in the transport direction has reached the reading position 21a (S12). While the leading end of the document in the conveyance direction does not reach the reading position 21a (S12: No), the process is on standby. When the leading end of the document in the transport direction reaches the reading position 21a (S12: Yes), next, standby processing is executed (S13).

  This standby process (S13) is a process for determining whether or not the original can be read and waiting for the transition to the next process until the original can be read. This will be described later with reference to FIG. When it is determined in the standby process (S13) that the original can be read, the next fed original is scanned (read) while being conveyed (S14). By providing the standby process (S13), for example, when the original cannot be read due to the memory full, the previous page being processed, etc., the start of reading of the original is waited. The

  When the reading of one page of the document is completed in this way, the digital data obtained by the reading is subjected to correction processing, encoding processing, and the like in the ASIC 66 (see FIG. 4A), and then the image memory 63k. Accumulated in. Then, transfer of the digital data stored in the image memory 63k is started (S15). Here, digital data is transferred to an external device preset by the user via the I / F 55 (see FIG. 6).

  Next, “1” is added to the value of the scan page number counter 63j (S16), and it is determined whether the value of the scan page number counter 63j is “5” or more (S18). Initially, since the value of the scan page number counter 63j is less than “5” (S18: No), the process proceeds to S26, and it is determined whether or not the leading end of the next document in the conveyance direction has reached the reading position 21a. (S26). If it is determined that the leading edge of the document of the next page in the conveyance direction does not reach the reading position 21a (S26: No), it is then determined whether the document has been conveyed by a predetermined distance or more (S38). If this determination is negative (S38: No), the process returns to S26.

  If it is determined that the leading edge of the document in the next page has reached the reading position 21a while the processing is repeated in this way (S26: Yes), the processing returns to S13 and the processing of the next page is started. To do.

  When the document for five pages is read while the processing is repeated, the value of the scan page number counter 63j is determined to be “5” or more (S18: Yes). Next, the A / D data maximum luminance change rate is determined. Calculation processing (S20) is executed. In this A / D data maximum luminance change rate calculation process, the trailing end of the one-page original in the conveyance direction passes through the reading position 21a, and the leading end of the next page in the conveyance direction reaches the reading position 21a. In this process, the A / D data maximum luminance change rate indicating the amount of light quantity change of the light source 22a from the time when the previous shading correction data is determined to the present time is calculated. For details, refer to FIG. It will be described later.

  Next, it is determined whether the calculated A / D data maximum luminance change rate is outside the fourth range 62e (S22). For example, when the calculated A / D data maximum brightness change rate is less than −2% or greater than + 2%, the A / D data maximum brightness change rate is determined to be outside the fourth range 62e (S22: Yes), Next, it is determined whether the A / D data maximum luminance change rate is outside the third range 62d (S28).

  Here, for example, when the A / D data maximum luminance change rate is less than −5% or greater than + 5%, it is determined that the A / D data maximum luminance change rate is outside the third range 62d (S28). : Yes), it can be determined that the light amount change amount of the light source 22a from the time when the previous shading correction data is determined until the present time is large. Accordingly, in order to determine and update the shading correction data again, the image reading unit 22 is moved below the reference position 21b (S32).

  Next, a correction data full determination process (S36) is executed. In this correction data full determination process (S36), the gain correction value, the black correction data, and the shading correction data are determined as in the above-described correction data full determination process (S10), and the determined value or correction data is determined. In this process, the correction gain value storage area 63a, the shading correction data 63c, and the black correction data storage area 63e are updated. Details will be described later with reference to FIG. Next, the value of the scan page number counter is set to “0” (S25), and reading of the next page is started.

  Returning to S22, description will be made. The calculated A / D data maximum luminance change rate is determined to be outside the fourth range 62e (S22: Yes), and the A / D data maximum luminance change rate is determined to be within the third range 62d. In this case (S28: No), the light quantity variation is observed, but it can be determined that the shading correction data is not updated enough. Therefore, the temporary gain value is determined, and the determined temporary gain value is used as the gain correction unit 22c1. A simple correction data determination process (S30) to be set is executed. When the temporary gain value is determined by this correction data simple determination process (S30), the value of the scan page counter 63j is then set to "0" (S25), and reading of the next page document is started.

  In this way, after the temporary gain value is determined, the image signal from the image sensor 22b is gain-corrected using the temporary gain value when reading the original for five pages. Therefore, even if there is a change in the amount of light from the time of execution of the previous correction data full determination process (S10, S36) to the present time, appropriate gain correction can be performed using the temporary gain value corresponding to the change in the amount of light. .

  Returning to S22, description will be given. When it is determined that the calculated maximum A / D data luminance change rate is within the fourth range 62e (S22: No), the correction gain value stored in the correction gain value storage area 63a is used as the gain correction unit 22c1. (S24), the value of the scan page number counter 63j is set to "0" (S25), and the document of the next page is read. That is, when it is determined that the light amount fluctuation from the execution time of the previous correction data full determination process (S10, S36) to the current time is small, the previous correction data full is read when reading 5 pages of originals to be read thereafter. The gain value, black correction data, and shading correction data determined in the determination process (S10, S36) are used.

  If it is determined that the leading edge of the next original does not reach the reading position 21a (S26: No) and the conveyance of a predetermined distance or more has been performed while the processing is repeated in this manner (S38: Yes), since it can be determined that there is no document of the next page, the conveyance by the conveyance rollers 35A, 35B, 35C, and 35D is stopped (S40), and the image reading unit 22 is moved below the reference position 21b to perform reading. End the data transfer process.

  The A / D data maximum luminance change rate calculation process (S20) will be described with reference to FIG. FIG. 9 is a flowchart of the A / D data maximum luminance change rate calculation process (S20). This A / D data maximum luminance change rate calculation process (S20) determines the inter-page A / D data maximum brightness, the inter-page A / D data maximum brightness, and the previous correction data full determination process (S10, S36). ), The A / D data maximum luminance change rate is determined from the corrected A / D data maximum luminance determined at the time of execution.

  Prior to the description of the flowchart, in this A / D data maximum luminance change rate calculation process (S20), a light amount change determination gain value 62c used for determining the inter-page A / D data maximum luminance (see FIG. 6). ).

  As described above, in order to determine the maximum luminance of inter-page A / D data, the document holding unit 19 is read by one line in the image reading unit 22, and the read image signal is amplified by gain correction and amplified. The A / D converter 22c2 performs A / D conversion on the obtained image signal, thereby obtaining digital data. A range corresponding to one line irradiated with light from the light source corresponds to an example of the predetermined range of the present invention.

  Here, when the image signal is amplified using the gain value determined in the previous correction data full determination process (S10, S36) and input to the A / D converter 22c2, the previous correction data full determination process ( S10, S36) If the amount of light suddenly increases from the time of execution to the present time, the image signal after gain correction is the maximum that can be converted by the A / D converter 22c2 (see FIG. 4B). The brightness is saturated and a significant value cannot be obtained for evaluating the amount of change in light quantity.

  Therefore, according to the image reading apparatus 1 of the present embodiment, in order to suppress the saturation of the image signal obtained by reading the document pressing unit 19 to the maximum luminance that can be converted by the A / D conversion unit 22c2, the document pressing unit. At the time of reading 19, the predetermined light amount determination gain value 62c is set in the gain correction unit 22c1, and the document presser 19 is read.

  The light amount change determination gain value 62c is set sufficiently smaller than the gain value determined by the correction data full determination process (S10, S36) or the temporary gain value determined by the correction data simple determination process (S30). For example, a value corresponding to an amplification factor of 1 is used. At the time of determining the inter-page A / D data maximum brightness, gain correction is performed using the light amount change determination gain value 62c set to be sufficiently small as described above, so that the value of the image signal after gain correction is A / D. Saturation to the maximum luminance that can be converted by the conversion unit 22c2 is suppressed. As a result, even if the amount of light suddenly increases from the previous correction data full determination process (S10, S36) to the present time, a significant maximum inter-page A / D data maximum luminance is determined in order to evaluate the amount of change in the amount of light. It can be done.

  Further details will be described with reference to the flowchart shown in FIG. In the A / D data maximum luminance change rate calculation process (S20), first, the light amount change determination gain value 62c (see FIG. 6) is set in the gain correction unit 22c1 (S202). Then, the reflected light from the document holder 19 is read for one line (S204). The read image signal for one line is gain-corrected using the light amount change determination gain value 62c set in the process of S202.

  Next, the digital signal for 16 pixels is extracted from the digital data for one line obtained by gain correction of the image signal for one line in the AEF 22c and A / D conversion. (S205). The digital data extracted here is data that has not undergone black correction and shading correction. Then, the average value of the extracted digital data for 16 pixels is calculated as the inter-page A / D data maximum luminance and stored in the inter-page A / D data maximum luminance storage area 63g (S206).

  Next, based on the corrected A / D data maximum luminance stored in the corrected A / D data maximum luminance storage area 63f and the inter-page A / D data maximum luminance, the A / D data maximum luminance change rate is calculated. Calculate (S208).

  Using the A / D data maximum luminance change rate calculated in this way, the light amount change amount from the previous correction data full determination process (S10, S36) is determined.

  According to the A / D data maximum luminance change rate calculation process (S20), the A / D data maximum luminance change rate for determining the amount of change in the light amount can be obtained without moving the image reading unit 22 below the reference position 21b. That is, the calculation can be performed while the image reading unit 22 is kept waiting below the reading position 21a. Therefore, the image reading unit 22 does not need to reciprocate between the reference position 21b and the reading position 21a after reading the previous page and before reading the next page, and can quickly start reading the next page of the document. it can. Further, since the reflected light from the document holder 19 is read by the image sensor 22b and the A / D data between pages is determined based on the acquired digital data, the light amount is determined according to the output from the image sensor 22b responsible for actual document reading. The amount of change can be suitably determined.

  The A / D data maximum luminance change rate calculation process (S20) is executed after the previous page has passed through the reading position until the next page passes through the reading position, so that the time until the next page is reached is effective. The time required for the reading process can be suppressed.

  The correction data full determination process (S10, S36) will be described with reference to FIG. FIG. 10 is a flowchart showing the correction data full determination process (S10, S36). At the start of this correction data full determination process (S10, S36), the image reading unit 22 is moved below the reference position 21b.

  First, in the standby process (S101), it is determined whether or not a document can be read and waits for a transition to the next process until the document can be read. Since this standby process (S101) is the same process as the standby process (S13) described above, the details will be described later with reference to FIG.

  When it is determined by the standby process (S101) that the document can be read, the image reading unit 22 emits light and reading of the reflected light from the white tape 21c is started. (S102).

  Then, the white tape 21c is read by the image sensor 22b, and gain adjustment for determining a gain value is performed so that the maximum luminance of the image signal matches a predetermined reference value input to the A / D converter 22c2. The determined gain value is stored in the correction gain value storage area 63a as a correction gain value (S103).

  Next, the determined gain value at the time of correction is set in the gain correction unit (S104), and the area for 16 lines is read while moving the image reading unit 22 by 16 lines below the reference position 21b, and the digital data is read. Obtain (S106). The digital data acquired here is read by the white level data read by the image sensor 22b provided at the position where the reflected light from the white tape 21c enters and the image sensor 22b provided in the light shielding area. Black level data. The acquired white level data is stored in the white level data storage area 63b, and the black level data is stored in the black level data storage area 63d (S108).

  Next, black correction data is determined based on the acquired black level data, stored in the black correction data storage area 63e (see FIG. 6), and stored in the black correction unit 66a of the ASIC 66 (see FIG. 4A). Set (S110).

  Next, shading correction data is determined based on the acquired white level data, stored in the shading correction data storage area 63c (see FIG. 6), and stored in the shading correction unit 66b (see FIG. 4A) of the ASIC 66. Set (S112).

  Then, the image reading unit 22 is moved from below the reference position 21b to below the reading position 21a (S114). Thereby, the irradiation object of the light source 22a, that is, the reading object by the image reading unit 22 is switched from the reference position 21b to the reading position 21a.

  Next, the light amount change determination gain value 62c is set in the gain correction unit 22c1 (S116). This is for calculating the maximum brightness of the corrected A / D data in the subsequent steps. That is, as described above, the A / D data maximum luminance change rate indicating the light amount change amount is calculated from the corrected A / D data maximum luminance and the inter-page A / D data maximum luminance. The maximum A / D data at the time of correction is obtained by using the light intensity change determination gain value 62c, which is the same value as the gain value used for calculating the maximum luminance of the inter-page A / D data so that it can be accurately determined. The brightness is determined.

  Next, the document holding unit 19 is read for one line by the image reading unit 22 moved below the reading position 21a, and digital data for one line is acquired (S118). The read image signal for one line is gain-corrected using the light amount change determination gain value 62c set in the processing of S116.

  Next, the digital signal for 16 pixels is extracted from the digital data for one line obtained by gain correction of the image signal for one line in the AEF 22c and A / D conversion. (S119). Then, the average value of the extracted digital data for 16 pixels is calculated as the corrected A / D data maximum luminance and stored in the corrected A / D data maximum luminance storage area 63f (S120).

  Then, the correction gain value is set in the gain correction unit 22c1 (S122), and the correction data full determination process (S10, S36) is terminated. According to the correction data full determination process, the gain value and the shading correction data are determined according to the light amount from the light source 22a at the present time. Then, when reading five pages of documents from the next page, the newly determined gain value and shading correction data are used to perform various corrections. Therefore, it is possible to perform appropriate correction according to the amount of light from.

  The correction data simple determination process (S30) will be described with reference to FIG. FIG. 11 is a flowchart showing the correction data simple determination process (S30).

In the correction data simple determination process (S30), first, a temporary gain value is determined based on the A / D data maximum luminance change rate and the correction gain value, and stored in the temporary gain value storage area 63i (see FIG. 6). (S302). The temporary gain value is determined by, for example, calculation shown in the following formula (2).
Temporary gain value = Gain value during correction × 100 / (100 + A / D data maximum luminance change rate) (2)
That is, instead of adjusting and determining the gain value based on the reflected light from the white tape 21c, the correction gain value determined in the previous correction data full determination process (S10, S36) is changed to the current value. By reflecting the A / D data maximum luminance change rate indicating the light amount change amount, an appropriate gain value corresponding to the light amount variation is determined.

  Then, the determined temporary gain value is set in the gain correction unit 22c1 (S304), and the correction data simple determination process (S30) is terminated. According to this correction data simple determination process (S30), the gain value (temporary gain value) corresponding to the light amount change amount can be determined without returning the image reading unit 22 to the reference position 21b. Then, when reading five pages of the original after the temporary gain value is determined, the temporary gain value is used to appropriately correct the gain of the image signal.

  Further, according to this simple correction data determination process (S30), it is not necessary to return the image reading unit 22 to the reference position 21b for the calculation of the temporary gain value, so that the reading of the next page can be started quickly. it can.

  The standby processing (S13, S101) will be described with reference to FIG. FIG. 12 is a flowchart showing the standby process (S13, S101).

  First, of the digital data acquired by reading the original up to the previous page, the digital data that has not been transferred by the I / F 55, that is, the digital data that has been read during the previous reading process and that has not been transferred or acquired by reading the previous page, has not been transferred. It is determined whether the amount of digital data is equal to or less than the untransferred data amount threshold 62a (see FIG. 6) (S132). When the amount of untransferred digital data is larger than the untransferred data amount threshold 62d (S132: No), that is, the I / F 55 is transferring digital data of a document read in advance, and If the transfer waiting data amount is larger than the untransferred data amount threshold value 62d, it is determined that reading of the next page cannot be started, and the process waits.

  If it is determined that the amount of untransferred digital data has become equal to or less than the untransferred data amount threshold 62d while waiting for processing (S132: Yes), then the free capacity of the image memory 63k is checked. It is determined whether the free space of the image memory 63k is equal to or larger than the free space threshold 62e (S134). That is, even when reading of the next page is started when the free space of the image memory 63k is small, the digital data acquired by the reading cannot be accumulated. Therefore, when the free capacity of the image memory 63k is smaller than the free capacity threshold 62e (S134: No), the processing is waited.

  Then, if it is determined that the free space of the image memory 63k is equal to or larger than the free space threshold 62e (S134: Yes), then the image processing unit 66c (see FIG. 4A) performs the preceding operation. It is determined whether the image processing of the digital data of the read original has been completed (S136). Specifically, it is determined whether the digital data encoding process in the image processing unit 66c is completed. That is, if the image processing in the image processing unit 66c has not ended, the digital data obtained by the reading cannot be processed even if the reading of the next page is started. Therefore, while the image processing in the image processing unit 66c does not end (S136: No), the process waits.

  When it is determined that the image processing in the image processing unit 66c has been completed while waiting for the processing in this way (S136: Yes), the standby processing (S13, S101) is ended. Upon completion of the standby process, reading of the next page of the document is started, or reading of reflected light for gain adjustment and shading correction data determination in the correction data full determination process (S10, S36) is started.

  According to the image reading apparatus 1, when the digital data obtained by reading the reflected light from the document holder 19 satisfies a predetermined condition, the correction data full determination process (S36) is executed. When the amount of change in light quantity from the previous execution of the correction data full determination process (S10, S36) is not so large, the correction data full determination process (S36) is not executed, so the image reading unit 22 has the reference position 21b. There is no need to move down. Therefore, reading of the next page can be started quickly, and the time required for the reading process can be shortened. On the other hand, since the correction data full determination process (S36) is executed when the light amount change amount from the previous correction data full determination process (S10, S36) is large, the correction data is updated at an appropriate timing. Thus, gain correction and shading correction can be suitably executed.

  Further, according to the correction data full determination process (S10, S36), the reflected light from the white tape 21c is made to wait until it is determined by the standby process (S101) that the document can be read. It is done. That is, after the document can be read, the reflected light is read, gain adjustment, and determination of shading correction data are performed. In other words, after the gain adjustment and shading correction data are determined, the next document is read without delay, so even if a change in the amount of light occurs after gain adjustment and shading correction, the influence can be suppressed and determined. Appropriate correction can be performed with the shading correction data and the gain value.

  Next, a read data printing process for outputting data acquired by reading an original with the image reading unit 22 to the image forming unit 56 (see FIG. 6) will be described with reference to FIG. This read data printing process transfers the digital data acquired by the image reading unit 22 to an external device set by the user in the process of S15 of the read data transfer process (see FIG. 8) described with reference to FIG. Instead, the image data is transferred to the image forming unit 56, and the standby process (S130) is executed instead of the standby process (S13, S101) described with reference to FIGS. Since others are common, illustration and description are omitted.

  With reference to FIG. 13, the standby process (S130) executed as a subroutine of the read data printing process will be described. FIG. 13 is a flowchart showing the standby process (S130) executed in the read data printing process. In the standby process (S130) shown in FIG. 13, the same steps as those in the standby process (S13, S101) described with reference to FIG.

  In the standby process (S130), first, it is determined whether the image forming unit 56 waits for print output, that is, whether the number of pages of unprinted digital data is equal to or less than a predetermined number (predetermined amount in claims) (S1320). For example, when high-definition printing is performed or when the amount of images to be printed is large, the time required for printing one page is longer than the time required for reading one page. Therefore, when the number of unprinted pages is larger than a predetermined number (for example, 3 pages) (S1320: No), it is determined that reading of the next page cannot be started, and the process is waited for.

  If it is determined that the number of unprinted pages has become equal to or less than the predetermined number while waiting for processing (S1320: Yes), then the free space of the image memory 63k is checked, and the free space of the image memory 63k is determined. It is determined whether or not the free space threshold 62e has been reached (S134), and whether or not the image processing of the digital data of the document read in advance performed in the image processing unit 66c (see FIG. 4A) has been completed. Judgment is made (S136). Note that the standby processing (S13, S101) described with reference to FIG. 12 is described here as determining whether or not the digital data encoding processing in the image processing unit 66c has been completed. On the other hand, since the standby process (S130) shown in FIG. 13 is executed in the read data printing process for printing out digital data, the image process other than the encoding process (for example, the binarization process) is completed. It may be configured to perform the determination of S136 based on whether or not it has been performed.

  According to the standby process (S130) shown in FIG. 13, the same effect as the standby process (S13, 101) shown in FIG. 12 can be obtained, and the number of unprinted pages can be equal to or less than a predetermined number, so that the original can be read. Reading of the reflected light from the white tape 21c is put on standby until it is determined that the state has been reached. Therefore, even if printing takes a long time and there is a long waiting time until the start of reading the next page of the document, the gain adjustment and shading correction data can be determined immediately before the start of reading the next page. Thus, appropriate correction can be performed with the shading correction data and the gain value.

  Although the present invention has been described based on the embodiments, the present invention is not limited to the above-described embodiments, and various improvements and modifications can be easily made without departing from the spirit of the present invention. Can be inferred.

  For example, according to the image reading apparatus 1 of the embodiment, the correction A / D data maximum brightness and the inter-page A / D data maximum brightness are determined by reading the document retainer 19 for one line. These maximum luminances may be determined by reading a plurality of lines. Further, it may be configured such that the correction-time A / D data maximum brightness and inter-page A / D data maximum brightness are determined using only the center portion in the main scanning direction in one line.

  Further, in the image reading apparatus 1, the surface corresponding to the platen glass 21 of the document holder 19 has been described as being configured in white. However, if there is no problem in detecting the amount of light change, other than white, for example, gray It may be constituted by.

  Further, according to the image reading apparatus 1, every time a five-page document is read, the light amount change amount from the time of determining the previous shading correction data is determined, but at the time of previous correction for each page and each page. You may compare with.

  Further, the read data transfer process (FIG. 8) described above is a process of reading only one side of a document placed on the ADF, but the present invention can also be applied to double-sided reading. That is, each time one side of the document is read, the maximum luminance change rate of A / D data may be calculated, and the light quantity change amount may be determined based on the calculated A / D data maximum luminance change rate.

  In the standby process (S13, S101) and the standby process (S130) of the above-described embodiment, the standby process is terminated when all three conditions are satisfied. The standby process may be terminated when the two conditions are satisfied. Further, another condition may be added in order to determine whether or not the document can be read. For example, the image reading apparatus 1 includes a storage medium mounting unit for mounting a storage medium such as a memory card, and is configured to store digital data read by the image reading unit 22 and stored in the image memory 63k in the storage medium. In such a case, the standby by the standby process may be continued until the storage of the digital data in the storage medium proceeds by a predetermined amount. In addition, the order in which the determination steps shown in the standby processes (S13, S101, S130) are executed can be changed as appropriate.

  In addition, the standby processing (S13, S101) and the standby processing (S130) described above are executed regardless of whether the reading is for the first page or the second and subsequent pages. However, in reading the first page, the standby process may be skipped.

  Further, the image reading apparatus 1 described above has been described as functioning as a scanner apparatus and a copying apparatus. However, a multifunction apparatus (MFD) that integrally includes a facsimile apparatus, a scanner apparatus, a copy function, a facsimile mechanism, a scanner function, and the like. : Multi Function Device) or the like, the present invention can also be applied to an image reading unit for reading an image of a document.

1 is a perspective view showing an external configuration of an image reading apparatus according to an embodiment of the present invention. It is sectional drawing which shows the internal structure of an image reading apparatus. It is a figure which shows the state which the image reading unit moved below the reference position. (A) is a figure which shows schematic structure of ASIC which processes the data output from an image reading unit and an image reading unit, (b) is a figure which shows schematic structure of AFE. It is a graph which shows the relationship between the image signal read with an image sensor at the time of white reading, and the main scanning direction position in a reading position. It is a block diagram which shows the structure of a control part. It is a graph which shows the relationship between the image signal output from an image sensor, and the main scanning direction position in a reading position. 6 is a flowchart of read data transfer processing executed by the image reading apparatus. It is a flowchart of A / D data maximum luminance change rate calculation processing. It is a flowchart which shows a correction data full determination process. It is a flowchart which shows a correction data simple determination process. It is a flowchart which shows a standby process. It is a flowchart which shows the standby process performed by read data printing process.

Explanation of symbols

1 Image Reading Device 21a Reading Position 21b Reference Position 21c White Tape (Density Reference Plate)
22 Image reading unit (reading means)
22a Light source 22b Image sensor (imaging means)
22c1 gain correction unit (image signal correction means)
22c2 A / D converter (conversion means)
35A Conveying roller (part of conveying means)
35B Conveying roller (part of conveying means)
35C Conveying roller (part of conveying means)
35D transport roller (part of transport means)
37 Pinch roller (part of transport means)
56 Image forming unit (printing means)
63f A / D data maximum brightness storage area during correction (maximum brightness storage means during correction)
63g A / D data maximum brightness storage area between pages (maximum brightness storage means between pages)
66 ASIC (correction means)
66c Image processing unit (image processing means)
S2, S32, S114 Irradiation target switching means S13, S101, S130 Standby means S15 Transfer means S106 to S112 Correction data determination means S36 Correction data update means S20, S22, S28, Change determination means S24, S122, S304 Correction value setting means S114 , S118 Correction data acquisition means S132, S134, S136 State determination means S1320 State determination means S204 Inter-page reading means S208, S2014 Change determination value determination means S302 Temporary correction value determination means

Claims (13)

Reading means that reads reflected light that is irradiated from a light source and reflected by the irradiation target, converts the light into image data, and outputs the image data;
Correction data determining means for reading reflected light from the density reference plate by the reading means to acquire image data, and determining correction data based on the acquired image data;
Using the correction data determined by the correction data determination means, the correction means for correcting the image data obtained by reading the reflected light by the reading means,
State determination means for determining whether or not a document can be read;
An image reading apparatus comprising: a waiting unit that waits for the reading of reflected light by the correction data determining unit until the state determining unit determines that the original can be read. Transfer means for transferring the image data corrected by the correction means to an external device;
The state determination unit determines that the document can be read on condition that the amount of image data not transferred by the transfer unit is equal to or less than a first threshold value. The image reading apparatus according to claim 1. Storing means for storing image data corrected by the correcting means;
2. The state determination unit according to claim 1, wherein the state determination unit determines that a document can be read on condition that the free space of the storage unit is equal to or greater than a second threshold value. Image reading device. Image processing means for performing predetermined processing on the image data corrected by the correction means and outputting the image data;
The state determination unit determines that the document is ready to be read on condition that the image processing unit has finished processing the image data of the document read in advance. The image reading apparatus according to claim 1.   5. The image reading apparatus according to claim 4, wherein the image processing unit encodes the image data corrected by the correction unit. Printing means for printing out the image data corrected by the correction means;
The state determination unit is configured to determine that a document can be read on the condition that image data waiting for print output by the printing unit has reached a predetermined amount or less. The image reading apparatus according to 1. A transport unit that transports the document one page at a time to a reading position irradiated with light from the light source;
The correction data determining unit is configured such that the trailing end of the one-page document that has been read is conveyed by the conveying unit and passes the reading position, and the leading end of the next page of the document is conveyed by the conveying unit. The image reading apparatus according to claim 1, wherein the reflected light is read for determining the correction data before being conveyed and reaching the reading position. An irradiation target switching means for switching an irradiation target of a light source between the reading position and a reference position at a position different from the reading position;
The correction data determining unit is configured such that the trailing end of the one-page document that has been read is conveyed by the conveying unit and passes the reading position, and the leading end of the next page of the document is conveyed by the conveying unit. Before being conveyed and reaching the reading position, the irradiation target switching unit switches the irradiation target of the light source to the reference position, and the reflected light is reflected by the reading unit in a state where the reference position is set as the irradiation target of the light source. 8. The image reading apparatus according to claim 7, wherein the image reading apparatus acquires image data by reading, and determines correction data based on the acquired image data. Correction data storage means for storing correction data determined by the correction data determination means;
Each time correction data is determined by the correction data determination means, correction data update means for updating the correction data storage means with the determined correction data;
After the rear end of the one-page original in the conveyance direction is conveyed by the conveyance unit and passes through the reading position, the reflected light is read by the reading unit in a state where the reading position is a light source irradiation target. And inter-page reading means for acquiring image data,
When the image data acquired by the inter-page reading unit satisfies a predetermined condition, the correction data determining unit reads the reflected light with the reference position as an irradiation target by the irradiation target switching unit, and acquires image data. The correction data is determined based on the acquired image data,
9. The image reading apparatus according to claim 8, wherein the correction unit corrects image data read by the reading unit using correction data stored in the correction data storage unit. After obtaining image data with the reference position as an irradiation target of the light source by the correction data determining means, and reading the reflected light with the reading position as the irradiation target of the light source by the irradiation target switching means to obtain image data Acquisition means;
A change determination value determining means for determining a change determination value indicating a change amount of the image data acquired by the inter-page reading means with respect to the image data acquired by the correction data acquisition means at the time of the previous correction data determination;
Change determination means for determining whether the change determination value determined by the change determination value determination means is outside the third range;
The correction data determining means reads the reflected light with the reference position as the irradiation object by the irradiation object switching means when the change determination means determines that the change determination value is out of the third range. The image reading apparatus according to claim 9, wherein data is acquired, and correction data is determined based on the acquired image data. The correction data acquisition means acquires image data for a predetermined range at the reading position every time correction data is determined by the correction data determination means.
Each time the image data is acquired for the predetermined range by the correction data acquisition unit, the correction maximum luminance storage unit that stores a value corresponding to the maximum luminance among the acquired image data;
The inter-page reading unit acquires image data for the predetermined range each time the trailing end in the transport direction of one page of the document that has been read is transported by the transport unit and passes through the reading position.
Inter-page maximum brightness storage means for storing a value corresponding to the maximum brightness among the acquired image data each time image data is acquired for the predetermined range by the inter-page reading means,
The change determination value determining unit is a value indicating a change amount of a value corresponding to the maximum luminance stored in the inter-page maximum luminance storage unit with respect to a value corresponding to the maximum luminance stored in the correction maximum luminance storage unit. The image reading apparatus according to claim 10, wherein the change determination value is determined. The reading means reads reflected light, photoelectrically converts and outputs an image signal; and
Image signal correction means for correcting an image signal output from the imaging means using an image signal correction value;
Conversion means for A / D converting the image signal corrected by the image signal correction means into digital data,
Image signal correction value storage means for storing the image signal correction value;
Correction value setting means for setting an image signal correction value stored in the image signal correction value storage means as an image signal correction value used in the image signal correction means when the image of the original is read by the reading means; ,
When the change determining means determines that the change determination value is within the third range and outside the fourth range, the change determination value and the image signal stored in the image signal correction value storage means Provisional correction value determining means for determining a temporary image signal correction value based on the correction value;
The correction value setting means, when reading a document of a predetermined number of pages to be read after the provisional image signal correction value is determined by the provisional correction value determination means, The image reading apparatus according to claim 10, wherein the image reading apparatus is set as an image signal correction value used by the image signal correction unit.   The correction value setting means uses the predetermined correction value for determination by the image signal correction means when the image data is read by the inter-page reading means and when the image data is read by the correction time data acquisition means. 13. The image reading apparatus according to claim 12, wherein the image reading apparatus is set as a signal correction value.

Images