JP4911186B2 - Image reading device - Google Patents

Description

  The present invention relates to an image reading apparatus that reads an image on a document.

  2. Description of the Related Art Image reading apparatuses that read an image on a document (for example, a scanner device and a copy device) include a device that automatically reads both sides of the document (automatic duplex reading device).

  As such an automatic double-sided reading apparatus, an apparatus that reads both sides of a document without inverting the document in one pass operation of the document has been proposed.

  For example, Patent Document 1 describes an automatic duplex reading apparatus in which a front side reading unit is provided on one side of a conveyance path through which a document is conveyed and a back side reading unit is provided on the other side of the conveyance path.

  Specifically, each reading unit includes a light source and a light receiving element that receives reflected light from the light source. As the light receiving element, for example, a sensor (CCD sensor or CIS sensor or the like) in which a plurality of light receiving elements are arranged in a row is used. Then, when the original passes through the conveyance path, the front side image is read by the front side reading unit, and the back side image is read by the back side reading unit.

JP 2005-110174 A

  Incidentally, in the image reading apparatus, a so-called shading correction operation is performed. The shading correction operation is a correction operation for eliminating unevenness in luminance caused by a difference in light receiving sensitivity of a plurality of light receiving elements that receive reflected light from the document surface. This shading correction operation is executed, for example, every predetermined number of sheets or at predetermined time intervals in order to optimize the reading operation.

  In the automatic duplex reading apparatus as described above, it is preferable that such a shading correction operation is performed for both the front surface reading unit and the back surface reading unit in order to optimize the reading operation.

  However, for example, when the front surface reading unit is present in the vicinity of the back surface reading unit, such as a normal reading position, when the shading correction operation of the back surface reading unit is performed, the light from the light source of the front surface reading unit is received by the back surface reading unit. Incident on the element. In short, the light from the light source of the front surface reading unit goes around to the back surface reading unit.

  At this time, since the light from the light source of the front surface reading unit adversely affects the back surface shading correction, it is difficult to accurately execute the shading correction of the back surface reading unit.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to reduce the influence of light wraparound and more accurately execute shading correction processing in an image reading apparatus having two reading means for reading images on both sides of a document. To provide technology.

In order to solve the above-mentioned problems, the invention of claim 1 is an image reading apparatus, wherein a first light source for irradiating a first surface of a document and a first light receiving means for receiving reflected light from the first surface. First reading means for reading an image on the first surface, a second light source for irradiating the second surface of the document, and a second light receiving means for receiving reflected light from the second surface. A second reading unit that reads the image on the second surface, a first shading correction member that reflects light from the first light source, and a shading correction relating to the first light receiving unit. A first shading correction processing means; a second shading correction member that reflects light from the second light source; and a plurality of pixels arranged in the main scanning direction in the second light receiving means. Receives reflected light from the shading correction member And a second shading correction processing means for performing a shading correction for said second light receiving means based on each pixel value of the plurality of pixels, the first shading correction processing means, the first light receiving The first light receiving means based on the pixel values of the plurality of pixels obtained by receiving reflected light from the first shading correction member with a plurality of pixels arranged in the main scanning direction in the means Data generating means for generating shading correction data for correcting luminance unevenness relating to the plurality of light sources obtained by receiving reflected light from the first surface during reading of the image of the first surface of the document; the pixel value of the pixel has a correction means for correcting, based on the shading correction data, the first reading means is fixed at a predetermined position, the A second reading unit between a first position when reading the image of the second surface and a second position when receiving reflected light from the second shading correction member in the sub-scanning direction; The data generating means estimates the amount of light reaching the first light receiving means from the second light source based on the position of the second reading means in the sub-scanning direction. The shading correction data is created, and the first shading correction processing means executes the shading correction based on the shading correction data .

  According to a second aspect of the present invention, in the image reading apparatus according to the first aspect of the present invention, light from the first light source does not reach the first light receiving means, and light from the second light source is the first light source. A storage unit that stores data relating to the amount of light received by the first light receiving unit in a state of reaching the one light receiving unit, and the first shading correction processing unit is stored in the storage unit. The shading correction is performed based on data.

  According to a third aspect of the present invention, in the image reading apparatus according to the second aspect of the invention, the data creating means creates the shading correction data based on data stored in the storage unit.

According to a fourth aspect of the present invention, in the image reading apparatus according to any one of the first to third aspects of the present invention, the data creating unit is configured to change the second light source based on a temporal change curve of the light amount of the second light source. The amount of light reaching the first light receiving means from the light source is estimated, and the shading correction data is created.

According to a fifth aspect of the present invention, in the image reading apparatus according to the first aspect of the invention, the data creating unit outputs reflected light from the first shading correction member at the plurality of pixels in the first light receiving unit. Receives light and creates first data relating to shading correction of the first light receiving means based on the pixel values of the plurality of pixels, and also relates to the first data for each pixel of the first light receiving means. Second data relating to a ratio between the first pixel value and the second pixel value acquired at two time points different from the generation time point is generated, and the first pixel value is determined based on the second light source. The light from the first light receiving means does not reach the first light receiving means, and the light from the first light source is reflected by the first shading correction member and reaches the first light receiving means. Light receiving by The second pixel value is both the light from the second light source and the light emitted from the first light source and reflected by the first shading correction member. Is a value corresponding to the amount of light received by the first light receiving means in a state of reaching the first light receiving means, and the first shading correction processing means is the first reading means by the first reading means. When reading a surface image, based on the first data and the second data, the pixel values of the plurality of pixels in the first light receiving unit are corrected, and the shading correction is performed. It is characterized by doing.

According to a sixth aspect of the present invention, there is provided an image reading apparatus, comprising: a first light source that irradiates a first surface of a document; and a first light receiving unit that receives reflected light from the first surface. A first reading means for reading an image on the surface; a second light source for irradiating the second surface of the document; and a second light receiving means for receiving reflected light from the second surface. A second reading means for reading the image of the image, a first shading correction member for reflecting light from the first light source, and a plurality of pixels arranged in the main scanning direction in the first light receiving means. based on each pixel value of the plurality of pixels obtained by receiving the reflected light from the first shading correction member, a first shading correction for correcting the luminance unevenness related to the first light receiving means a first data generating means for generating data, or the second light source Obtained by receiving reflected light from the second shading correction member with a second shading correction member that reflects the light of the second and a plurality of pixels arranged in the main scanning direction in the second light receiving means. And second data creating means for generating second shading correction data for correcting luminance unevenness related to the second light receiving means based on the pixel values of the plurality of pixels . The first reading means is fixed at a predetermined position, and the second reading means has a first position for reading the image on the second surface and the second shading correction member in the sub-scanning direction. is capable least move between a second position at the time of receiving reflected light from said first data generating means, based also on the position in the sub-scanning direction of the second reading means, wherein First It estimated from the amount of source light that reaches to the first light receiving means, characterized by creating a data the shading correction based also on the amount of light.

According to the first to fifth aspects of the present invention, in an image reading apparatus having two reading units that respectively read images on both sides of a document, the influence of light wraparound is reduced and shading correction processing is performed more accurately. Can be performed. In addition, the shading correction data can be generated more accurately in consideration of the position of the second reading unit in the sub-scanning direction.

In particular, according to the fourth aspect of the present invention, it is possible to more accurately create shading correction data in consideration of a temporal change in the light amount of the second light source.

According to the sixth aspect of the present invention, in the image reading apparatus having two reading units that respectively read the images on both sides of the document, the influence of light wraparound is reduced, and shading correction data is more accurately obtained. Can be created.

1 is a diagram illustrating a schematic configuration of a copying apparatus. It is a figure which shows the structure of a back surface reading unit. It is a figure which shows the functional block of a controller. It is a figure which shows the control block regarding shading correction. It is a figure which shows the state in which a surface reading unit exists in a reading position. It is a figure which shows a mode that a surface reading unit moves from a reading position to a shading correction position. It is a figure which shows the state in which a surface reading unit exists in a shading correction position. It is a conceptual diagram which shows the pixel value L (x) of each pixel of the image sensor for back surfaces. It is a figure which shows the relationship between pixel value L (x), value R (x), and value G. It is a figure which shows an example of the function G (y). 5 is a flowchart illustrating an operation example in the copy apparatus. It is a flowchart which shows a part of back surface shading correction | amendment operation | movement. It is a flowchart which shows a part of back surface shading correction | amendment operation | movement which concerns on 2nd Embodiment. It is a figure which shows the attenuation curve of the light quantity of a light source. It is a figure which shows the functional block of the controller which concerns on 3rd Embodiment. It is a figure which shows ratio data.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<1. First Embodiment>
<1-1. Outline of configuration>
FIG. 1 is a diagram showing a schematic configuration of the copy apparatus 1. The copying apparatus 1 includes a scanner unit 3 and a print output unit 5. The copying apparatus 1 is also referred to as an image reading apparatus because it has a function of reading an image of a document. In each figure, directions and the like are shown using an XYZ orthogonal coordinate system.

  The scanner unit 3 is a processing unit that optically reads a document placed at a predetermined position of the copying apparatus 1 and generates image data (also referred to as a document image) of the document.

  The print output unit 5 is an output unit that prints out an image on various media such as paper based on data related to a print target. As the print output unit 5, various types such as an electrophotographic system or an inkjet system can be adopted.

  The copy apparatus 1 obtains an image relating to a document by the scanner unit 3 and prints out the image by the print output unit 5, thereby realizing a copy (copy) function of the document.

  The scanner unit 3 includes a front surface reading unit 10, a back surface reading unit 20, and a document conveying unit 30, and can automatically read images on both sides of the document. That is, the scanner unit 3 is configured as an automatic double-sided reading device.

  The document conveyance unit 30 includes a plurality of conveyance rollers (specifically, a plurality of roller pairs) including a paper feed roller 31, a separation roller 32, a pre-reading roller 34, and a post-reading roller 35. The document placed on the document placement tray 41 is sent to the separation roller 32 side by the paper feed roller 31 and then sequentially advances to the downstream side in the transport direction by the rollers 32, 33, 34, and 35. The document advances toward the discharge tray 48 along the conveyance path CP formed by the rollers 32, 33, 34, 35, the guide member 37, and the like.

  Here, the front surface reading unit 10 is configured as a reduction optical system type reading unit. The surface reading unit 10 includes a light source 11, a reflector 11 r, mirrors 12 (12 a, 12 b, 12 c), a lens (imaging optical system) 14, and an image sensor (imaging device) 15. As the image sensor 15, a linear image sensor (here, a CCD line sensor or the like) in which a plurality of light receiving elements (pixels) are arranged one-dimensionally (in a straight line) in the main scanning direction (X direction) is used. Each element of the surface reading unit 10 is provided below the document transport path CP.

  The front surface reading unit 10 is configured as a movable unit that can move in the sub-scanning direction (Y direction). As the front surface reading unit 10 moves in the Y direction, various components fixed to the front surface reading unit 10, that is, the light source 11, the reflector 11r, the mirrors 12 (12a, 12b, 12c), the lens 14, the image sensor 15, and the like. Moves in the Y direction. The surface reading unit 10 can move at least between the position P1 in FIG. 1 (and FIG. 5) and the position P2 in FIG. Since the position P1 is a position when the front surface reading unit 10 reads an image of a document, it is also referred to as a reading position. Further, the position P2 is a position when the surface reading unit 10 receives the reflected light from the surface shading correction plate 51, that is, a position when performing a shading correction operation in short, and is also referred to as a shading correction position. Is done.

  On the other hand, the back surface reading unit 20 is configured as a close contact type reading unit here. The back surface reading unit 20 is configured as a so-called CIS (Contact Image Sensor).

  Specifically, the back surface reading unit 20 includes a light source 21 and an image sensor (imaging device) 25 as shown in FIG. As the image sensor 25, a linear image sensor in which a plurality of light receiving elements (pixels) are arranged in a one-dimensional shape (linear shape) in the main scanning direction (X direction) is used. Each element of the back side scanning unit 20 is provided above the document transport path CP. Further, the back side reading unit 20 is fixed at a predetermined position in the copying apparatus 1 as shown in FIG.

  As described above, the front side reading unit 10 is provided on one side (lower side) of the conveyance path CP through which the document is conveyed, and the back side reading unit 20 is provided on the other side (upper side) of the conveyance path CP. ing.

  By performing the reading operation by the front side reading unit 10 and the back side reading unit 20 in accordance with the timing when the original is conveyed downstream by the original conveying unit 30, images on both sides of the original are acquired in parallel. When the original passes through the vicinity of the platen glass 43 in a state where the movable surface reading unit 10 exists at the reading position P1, the surface reading unit 10 performs a reading operation on the surface.

  In this copying apparatus 1, as the original placed on the original placement tray 41 advances downstream in the conveyance path CP, the advance angle of the original is gradually changed, and the original passes near the platen glass 43. When you do, the top and bottom of the surface are reversed. That is, when the document is placed on the document placement tray 41, the surface of the document is the upper surface, whereas when the document passes near the platen glass 43, the surface of the document is the lower surface. .

  The light source 11 of the surface reading unit 10 irradiates the front (front) surface (lower surface) of the document passing through the conveyance path CP from below. The light from the light source 11 passes through the platen glass 43 disposed between the lower surface side members 45 and 46 of the document conveying unit 30 and is reflected by the surface of the document. The reflected light is received by the image sensor 15. The image sensor 15 acquires line images in the paper width direction (main scanning direction) at a time. Then, when the sheet gradually moves in the conveyance direction (sub-scanning direction), a similar line image acquisition operation is repeated, whereby a two-dimensional image relating to the surface of the document is acquired.

  In parallel with the reading operation by the front surface reading unit 10, the back surface reading operation by the back surface reading unit 20 is executed.

  The light source 21 of the back surface reading unit 20 irradiates the back surface (upper surface) of the document passing through the conveyance path CP from above. The light reflected from the back side of the document is received by the image sensor 25. The image sensor 25 acquires line images in the paper width direction (main scanning direction) at a time. A similar line image acquisition operation is repeated when the sheet gradually moves in the transport direction (sub-scanning direction), whereby a two-dimensional image relating to the back side of the document is acquired.

  As described above, the scanner unit 3 uses the front surface reading unit 10 and the back surface reading unit 20 to read images on both sides of the document without inverting the document in one pass operation of the document. It is possible to generate image data for each surface.

  The copying apparatus 1 can also perform single-sided copying in a state where an original is placed on the platen glass 44. In this case, the operator once places the document on the platen glass 44 in a state where the document transport unit 30 is retracted upward from the platen glass 44 of the main body of the copying apparatus 1. Then, when the operator returns the document conveying unit 30 to the original position again, the document is sandwiched between the platen glass 44 and the lower surface side member 46 of the document conveying unit 30. Thereafter, the front surface reading unit 10 passes from the position P1 to the position P2 and further advances (scans) near the lower portion of the platen glass 44 to the right side in FIG. A two-dimensional image of the original can be read.

  Further, the copying apparatus 1 includes a front surface shading correction plate 51 and a back surface shading correction plate 52. Both correction plates 51 and 52 are sheet-like members having a uniform white color. The back surface shading correction plate 52 is disposed opposite to the back surface reading unit 20 in the vicinity of the back surface reading unit 20. On the other hand, the surface shading correction plate 51 is disposed in the vicinity of the position P2. Specifically, the surface shading correction plate 51 is disposed at a position facing the light source 11 of the surface reading unit 10 that has moved to the position P2.

  The front shading correction plate 51 is used for shading correction processing of the front surface reading unit 10, and the back surface shading correction plate 52 is used for shading correction processing of the back surface reading unit 20.

  Further, as shown in FIG. 3, the controller 9 includes a front surface shading correction unit 91 and a back surface shading correction unit 96. FIG. 3 is a block diagram showing a functional configuration of the controller 9.

  The surface shading correction unit 91 includes a data generation unit 92 that generates data for surface shading correction, and a pixel value correction unit that corrects the pixel value of the read image (scanned image) based on the data (surface shading correction data). 93. The surface shading correction data is data for correcting luminance unevenness related to the pixel rows of the image sensor 15.

  Similarly, the back side shading correction unit 96 creates a data creation unit 97 that creates data for back side shading correction, and a pixel value correction unit 98 that modifies the pixel value of the read image based on the data (back side shading correction data). (See also FIG. 4). The back surface shading correction data is data for correcting luminance unevenness related to the pixel rows of the image sensor 25.

  Here, in both the front surface reading unit 10 and the back surface reading unit 20, it is assumed that there is almost no luminance unevenness of the optical system, and the luminance unevenness of the imaging system mainly exists, and the luminance unevenness of the imaging system is corrected for shading. It shall be corrected by

  Next, each shading correction process will be described in detail.

<1-2. Shading correction processing>
First, the shading correction process by the surface reading unit 10 will be described. The shading correction process by the surface reading unit 10 is executed as follows. 5 is a diagram illustrating a state in which the front surface reading unit 10 is present at the reading position P1, and FIG. 7 is a diagram illustrating a state in which the front surface reading unit 10 is present at the shading correction position P2. FIG. 6 is a diagram illustrating a state where the front surface reading unit is moving from the reading position P1 to the shading correction position P2.

  The front surface reading unit 10 (specifically, the light source 11 and the like) moves in the + Y direction from the position P1 in FIG. 5 to the position P2 in FIG. 7 and stops. Here, it is assumed that the light source 11 is always lit when the power of the copying apparatus 1 is turned on in order to stabilize the amount of light. Therefore, the light source 11 (for example, white fluorescent tube) is lit from the time immediately before the start of movement to the time immediately after the start of movement.

  Then, the shading correction process is executed with the front surface reading unit 10 stopped at the position P2 in FIG. Specifically, the light emitted from the light source 11 is reflected by the surface shading correction plate 51 and received by the image sensor 15 via the mirror 12. Then, correction data is generated so that each output pixel value of the plurality of light receiving elements in the image sensor 15 is adjusted to a predetermined white value (for example, the maximum gradation value “255” of an 8-bit value). . The correction data is generated by the surface shading correction unit 91 (specifically, the data creation unit 92) and stored in the shading correction table TB1.

  Thereafter, at the time of reading the front image, each pixel value acquired by the image sensor 15 is corrected based on the correction data stored in the shading correction table TB1. In this way, the surface shading correction process is executed.

  Next, shading correction processing by the back surface reading unit 20 will be described.

  Since the back side reading unit 20 is fixed, it does not move. The back surface shading correction processing is executed by using the back surface shading correction plate 52 disposed to face the back surface shading correction plate 52.

  Specifically, the light emitted from the light source 21 (for example, white LED) is reflected by the back surface shading correction plate 52 (FIG. 1), and the reflected light from the back surface shading correction plate 52 is received by the image sensor 25. . Each of the plurality of pixels of the image sensor 25 obtains a pixel value based on the amount of received light. Then, based on the pixel value, all the output pixel values of the plurality of light receiving elements in the image sensor 25 are adjusted to a predetermined white value (for example, the maximum gradation value “255” of an 8-bit value). Correction data K (x) is generated. The correction data K (x) is obtained by the back surface shading correction unit 96 (specifically, the data creation unit 97), and a shading correction table TB2 (see FIG. 4) based on the correction data K (x) is created. . The shading correction table TB2 is stored in a memory (storage unit) in the controller 9.

  Here, the correction data K (x) represents shading correction data for each pixel arranged in the main scanning direction (X direction), and more specifically, the shading correction data for the pixel at position x in the image sensor 25. To express. The correction data K (x) can be calculated by the following equation (1), for example. The value L (x) represents the output pixel value of the pixel at the position x. The value b is, for example, the maximum gradation value “255” of the pixel value (8-bit value).

  When uniform white light is received in the X direction, each pixel value L (x) theoretically becomes the same value. Actually, however, the pixel values L (x) are different from each other as shown in FIG. 8 due to differences in sensitivity characteristics of the light receiving elements in the image sensor 25. FIG. 8 is a conceptual diagram showing output pixel values of the respective light receiving elements when the reflected light or the like from the back surface shading correction plate 52 is received.

  On the other hand, as shown in FIG. 4, by using the correction data K (x) calculated as described above, the pixel output value at the time of actual image reading is corrected. Variations between pixels can be suppressed or eliminated.

  More specifically, the pixel output value M (x) at the time of image reading may be multiplied by the correction data K (x). Here, as shown in Expression (1), the correction data K (x) is a value corresponding to the reciprocal of the value L (x).

  For example, as shown in FIG. 8, when the pixel value M (x) of the pixel at the position x1 can be obtained only as 3/4 of the original value, the pixel value of the pixel is expressed by the equation (1). M (x) is increased to the inverse of 3/4, that is, 4/3 times. Thereby, the pixel value M (x) is corrected to an appropriate value. The same applies to the pixels at other positions x. In this way, the shading correction process is executed. In addition, although the back surface shading correction process is described here, the same applies to the front surface shading correction process. The surface shading correction process is executed based on the above equation (1).

  By the way, in this embodiment, the surface shading correction data is created based on the pixel value L (x) received in a state where the surface reading unit 10 has moved to the position P2 (see FIG. 7). When the front shading correction operation is executed in this way (FIG. 7), the front shading correction plate 51, the rear shading correction plate 52, and the like exist between the light source 21 and the mirror 12a. Therefore, the light from the light source 21 hardly reaches the image sensor 15 of the surface reading unit 10. That is, there is almost no influence of the light from the light source 21 of the back surface reading unit 20 when creating the front shading correction data.

  On the other hand, when the back side shading correction data is created, the influence of the light from the light source 11 of the front side reading unit 10 is relatively large.

  Specifically, as shown in FIG. 5 and the like, the back surface reading unit 20 is disposed in the vicinity of the platen glass 43. Further, the back surface shading correction plate 52 may be disposed opposite to the back surface reading unit 20 with the conveyance path CP of the document PA interposed therebetween. Normally, during the operation of creating the back surface shading correction data as described above, PA does not exist in the conveyance path CP (in particular, a position between the roller 34 and the roller 35, that is, a position near the platen glass 43). For this reason, the light (part of the light) from the light source 11 of the front surface reading unit 10 passes through the platen glass 43, travels beyond the conveyance path CP of the document PA, and enters the image sensor 25 of the back surface reading unit 20. To do. In short, the light from the light source 11 goes around to the position of the image sensor 25. As a result, the output value of the image sensor 25 is not an original value reflecting only the reflected light from the back surface shading correction plate 52, but also a value affected by the light from the light source 11. Therefore, if the output value of the image sensor 25 is used as it is, the shading correction of the back surface reading unit is not accurately executed.

  Therefore, in this embodiment, the correction data K (x) related to the backside shading correction process is calculated using the following equation (2) instead of the above equation (1).

  Specifically, the correction data K (x) is calculated based on the value R (x). Here, the value R (x) is obtained from the light source 11 to the image sensor from each pixel value L (x) of the image sensor 25 at the time of shading correction processing (more specifically, when receiving reflected light from the back surface shading correction plate 52). This is a value obtained by subtracting the value F (x) corresponding to the sneak light amount to 25. That is, this value R (x) is a value reflecting only the reflected light from the back surface shading correction plate 52, and corresponds to a value excluding the influence of the amount of sneak light (originally speaking).

  Specifically, data F (x) relating to the amount of light received by the image sensor 25 in a state in which the light from the light source 21 does not reach the image sensor 25 and the light from the light source 11 reaches the image sensor 25 is stored in advance. It is measured and stored in the memory in the controller 9. The value F (x) corresponding to the sneak light amount is, for example, the value of the pixel at each position x of the image sensor 25 in the state where the surface reading unit 10 exists at the position P1, the light source 11 is turned on, and the light source 21 is turned off. What is necessary is just to be acquired as an output value. Further, the value F (x) does not need to be acquired for each shading correction process, and may be acquired at a certain maintenance point, for example.

  Here, as described above, it is assumed that there is almost no luminance unevenness of the optical system, and light of substantially the same brightness has arrived from the light source 11 to each light receiving element. That is, the light source 11 emits uniform light in the X direction. The value F (x) corresponding to the amount of light emitted from the light source 11 and received by the image sensor 25 is approximated as being a constant value G in the X direction.

  By using such corrected correction data K (x), as shown in FIG. 9, by subtracting the value F (x) from each pixel value L (x) of the image sensor 25, the original correction data K (x) is used. A value R (x) is calculated, and shading correction processing is executed based on the value R (x). Therefore, it is possible to execute more accurate shading correction processing while suppressing the influence of the amount of sneak light.

  In particular, in this embodiment, the light source 11 is always lit when the power is on. Therefore, when the front surface reading unit 10 exists at the position P1 and the document does not exist in the conveyance path CP (FIG. 5), the light from the light source 21 passes through the document conveyance path CP and reaches the image sensor 15. . In such a situation, by creating the shading correction table TB1 based on the above equation (2), it is possible to execute more accurate shading correction processing while suppressing the influence of the amount of sneak light. Is possible.

  Further, in this embodiment, the surface reading unit 10 is movable, and the position of the light source 11 of the surface reading unit 10 varies. In particular, in this embodiment, the front surface reading unit 10 is moved independently of the shading correction operation related to the back surface reading unit 20, and the execution timing of each shading correction operation is determined independently of each other. Therefore, the position of the front surface reading unit 10 at the time of executing the shading correction operation by the back surface reading unit 20 is not fixed to one position. For example, when the back surface shading correction operation is performed, the front surface reading unit 10 may exist at the position P1 or may exist at the position P2. Therefore, the value G corresponding to the amount of incident light from the light source 11 of the front surface reading unit 10 to the image sensor 25 in the back surface shading correction operation varies depending on the position of the light source 11.

  Therefore, in this embodiment, the following equation (3) is used. That is, the value G in Equation (2) is obtained as a function of the position y in the Y direction of the surface reading unit 10. This value y is a value at the time of back surface shading correction operation (specifically, the time of receiving reflected light from the back surface shading correction plate 52). Then, it is assumed that shading correction processing is performed using the correction data K (x) reflecting the value G.

  FIG. 10 is a diagram illustrating an example of the function G (y). FIG. 10 shows a case where the wraparound light amount monotonously decreases from the position P1 to the position P3. More specifically, an example of monotonic decrease expressed by a linear expression is shown. The position P3 is a predetermined position between the position P1 and the position P2. In FIG. 10, it is assumed that the amount of sneak light is zero on the right side of the position P3. That is, in the expression (3), the value of the function G (y) is zero in the range of y> y3. The values y1 and y3 are the coordinate values (Y coordinate values) of the Y-direction positions corresponding to the positions P1 and P3, respectively.

  Further, the value C in Expression (3) is the pixel value of each pixel of the image sensor 25 in a state where the surface reading unit 10 exists at the position P1 (y = y1) and the light source 11 is turned on and the light source 21 is turned off. It is assumed that it is acquired as the average value of. The value C is acquired at a certain maintenance time (for example, initial adjustment time T0 in the factory).

  In this embodiment, the correction data K (x) according to the equations (2) and (3) is generated by the backside shading correction unit 96 (specifically, the data creation unit 97) and stored in the shading correction table TB2. The Thereby, the correction data K (x) becomes a value reflecting the amount of sneak light estimated based on the position y of the surface reading unit 10.

  Thereafter, at the time of reading the back image, each pixel value M (x) relating to the back image acquired by the image sensor 25 is corrected based on the correction data stored in the shading correction table TB2. Thereby, the back surface shading correction data is reflected on the pixel value N (x) after correcting the pixel value M (x), and the back surface shading correction processing is completed.

  Here, creating the shading correction table TB2 based on the values F (x) to C estimates the amount of light reaching the image sensor 25 from the light source 11 and backside shading correction data based on the amount of light. Is equivalent to creating Similarly, executing the shading correction based on the value F (x) to the value C is estimating the amount of light reaching the image sensor 25 from the light source 11 and executing the back surface shading correction based on the amount of light. Equivalent to. In this way, the back surface shading correction unit 96 estimates the amount of light reaching the image sensor 25 from the light source 11 and performs back surface shading correction based on the amount of light.

  In addition, although the case where the function G (y) is approximated by a linear expression is illustrated here, it is not limited to this. For example, it may be approximated by a higher order expression or the like. Alternatively, the values G (y) at a plurality of positions y may be measured and stored as a data table.

<1-3. Detailed operation>
Next, with reference to FIG. 11, an example of operation in the copy apparatus 1 and, in detail, an example of operation at the time of receiving a copy start instruction will be described.

  In this embodiment, as described above, the execution timing of the shading correction operation (specifically, the correction data table creation operation using the reflected light from the shading correction plates 51 and 52) is the front reading unit and the back reading unit. And are determined according to their own standards.

  For this reason, during the copying operation, only the shading correction operation of the front side reading unit may be executed, and the shading correction operation of the back side reading unit may not be executed. Conversely, only the shading correction operation of the back surface reading unit is performed, and the shading correction operation of the front surface reading unit may not be performed. Further, the shading correction operation of the front surface reading unit and the shading correction operation of the back surface reading unit may be executed at the same time in parallel. Further, when the shading correction operations on both sides are executed in parallel, not only when the shading correction operations on both sides are executed at exactly the same timing, but also the shading correction operations on both sides are started at different timings. It also exists when

  In any situation, the back surface shading correction operation is executed using the relationship as shown in the above formulas (2) and (3), thereby reducing the influence of the light sneaking from the light source 11. Is possible. In particular, by acquiring the amount of sneak light from the light source 11 to the image sensor 25 as a value corresponding to the position y, it is possible to execute the shading correction process with very high accuracy.

  First, when the main switch is turned on (step S1) and the initialization process (step S2) is completed, it is determined whether or not the document is placed at a predetermined position and the start key is pressed (step S3). S4). The standby state is continued until the original is placed on the original placement tray 41 and the start key is pressed. When the document is placed on the document placement tray 41 and the start key is pressed, the process proceeds to step S11.

  In step S11, it is determined whether or not it is the execution timing of the shading correction operation.

  If it is not the execution timing of the shading correction operation, the process proceeds to step S12. In step S12, the image reading process relating to both sides of the document as described above is executed. In this image reading process, the pixel value of each pixel in the read image is corrected based on the shading correction data generated in steps S14 and S16 described later. This completes the shading correction process for the actual read image.

  On the other hand, when it is the execution timing of at least one of the front shading correction operation and the back surface shading correction operation, the process proceeds to step S13. In other words, if it is the generation timing of the front shading correction data or the generation timing of the back surface shading correction data, the process proceeds to step S13.

  In step S13, it is determined whether it is the execution timing of the back surface shading correction operation. Then, when it is determined that it is not the execution timing of the back surface shading correction operation, the back surface shading correction operation is not executed and the process proceeds to step S15. On the other hand, when it is determined that it is the execution timing of the back surface shading correction operation, the process proceeds to step S14, and the execution of the back surface shading correction operation (specifically, the data creation operation of the correction table TB2 etc.) is started or continued. Thereafter, the process proceeds to step S15.

  FIG. 12 is a diagram illustrating the operation executed in step S14 in the back surface shading correction processing. As shown in FIG. 12, first, in step S21, the light emitted from the light source 21 and reflected by the back shading correction plate 52 is received by the image sensor 25, and the pixel value L (x) of each pixel of the image sensor 25 is obtained. Obtained (step S21). Next, the data creation unit 97 acquires the position information (position y) of the light source (lamp) 11 at the time of acquisition in step S21 (step S22) and sets adjustment parameters (such as value C) related to the backside shading correction processing. Obtain (step S24). Then, the data creation unit 97 generates correction data related to the backside shading correction process based on the information (position information and adjustment parameters) acquired in steps S22 and S24 (step S25). Specifically, the correction data K (x) is calculated based on the equations (2) and (3), and the correction data K (x) is stored in the data table TB2.

  In the next step S15, it is determined whether or not it is the execution timing of the surface shading correction operation. When it is determined that it is not the timing for executing the surface shading correction operation, the surface shading correction operation is not executed and the process proceeds to step S17. On the other hand, when it is determined that it is the execution timing of the surface shading correction operation, the process proceeds to step S16, and the execution of the surface shading correction operation is started or continued. Thereafter, the process proceeds to step S17.

  Note that when it is the execution timing of both the front and back shading correction operations, the back surface shading correction operation in step S14 and the front surface shading correction operation in step S16 are executed in parallel. Further, as described above, in each shading correction operation (steps S14 and S16), an operation for acquiring a shading correction image and an operation for generating shading correction data are performed.

In step S17, it is confirmed whether or not all scanning operations for a plurality of documents have been completed. If the scan operation is not yet completed, the process returns to step S11 again and the same operation as described above is repeated. On the other hand, if it is determined that all scanning operations for a plurality of documents have been completed, a print output operation is executed (step S18). Specifically, double-sided scanned images relating to a plurality of originals acquired in step S12 are output on printing paper. In this way, a copy operation relating to a plurality of documents is executed. As described above, the correction processing based on the shading correction data generated in steps S14 and S16 is performed in step S12 on the pixel value of each pixel of the double-sided scanned image used for the print output operation. Is done.

  As described above, the shading correction process and the copy operation for the two reading units 10 and 20 are executed.

  According to such an operation, the influence of light from the light source 11 can be reduced in the back surface shading correction operation. Therefore, it is possible to execute an accurate back surface shading correction operation.

  In addition, the copying apparatus 1 acquires the position y of the light source 11 at the time of back surface shading correction operation (specifically, when the reflected light is received from the back surface shading correction plate 52), and the amount of sneak light from the light source 11 based on the position y. Adjust the size of. Therefore, it is possible to perform a more accurate backside shading correction operation.

  In addition, although the case where the back surface shading correction operation is executed in accordance with the copy start instruction (exemplarily executed in parallel with the front surface shading correction operation) is illustrated here, the present invention is not limited to this. For example, each shading correction operation may be executed on its own standard in a standby state for a copy start instruction. Then, when the back surface shading correction operation is executed, the above idea may be applied.

<2. Second Embodiment>
The second embodiment is a modification of the first embodiment. Below, it demonstrates centering around difference with 1st Embodiment, referring FIG.13, FIG14 etc. FIG.

  In the first embodiment, the change with time of the light amount of the light source 11 is not taken into consideration, but with the second embodiment, the change with time of the light amount of the light source 11 is also taken into consideration. Specifically, the value G of equation (2) is calculated as shown in the following equation (4).

  Here, the value α (t) is a function representing a change with time of the light amount of the light source 11. Specifically, the change with time of the value α (t) is expressed by an attenuation curve (time change curve) as shown in FIG. 14, for example. Note that data regarding the value α (t) is stored in a memory in the controller 9.

  Then, the back surface shading correction process as shown in FIG. 13 may be executed. The operation shown in FIG. 13 is different from the operation of FIG. 12 in that step S23 is added.

  Specifically, first, in step S21, the light emitted from the light source 21 and reflected by the back shading correction plate 52 is received by the image sensor 25, and the pixel value L (x) of each pixel of the image sensor 25 is acquired. (Step S21). Next, the data creation unit 97 acquires position information (position y) of the light source (lamp) 11 at the time of acquisition in step S21 (step S22), and information on deterioration of the light amount of the light source 11 (attenuation rate α). Obtain (step S23). In addition, the data creation unit 97 acquires an adjustment parameter related to the back surface shading correction process (step S24). Then, the data creation unit 97 generates correction data related to the backside shading correction processing based on the information (position information, deterioration information, and adjustment parameters) acquired in steps S22, S23, and S24 (step S25). Specifically, the correction data K (x) is calculated based on the equations (2) and (4), and the correction data K (x) is stored in the data table.

  For example, as shown in FIG. 14, the light source 11 has a light amount of 100% at the initial adjustment time T0 immediately before product shipment, while the light amount of the light source 11 is a predetermined ratio at a time T8 when a predetermined time has passed. For example, the case where it falls to 60%) is assumed. By using Equation (4) in such a case, it is possible to realize more accurate shading correction processing in consideration of a decrease in the amount of sneak light incident on the image sensor 25 from the light source 11 with the passage of time. Is possible. That is, it is possible to more accurately execute the shading correction by reflecting the temporal change in light amount of the light source 11 (specifically, attenuation of the light amount).

<3. Third Embodiment>
The third embodiment is a modification of the first embodiment. Below, it demonstrates centering on difference with 1st Embodiment.

  In the first embodiment, the case where the sneak light amount from the light source 11 is directly estimated by obtaining the value F (x) is exemplified. However, in the third embodiment, the sneak light amount from the light source 11 is calculated. The case where it estimates indirectly is illustrated.

  In the third embodiment, not only a single shading correction table TB2 is created, but two shading correction tables TB2 (TB22) and TB3 are created (see FIG. 15). An example in which a shading correction process for reducing the influence of the sneak light amount from the light source 11 is executed based on the two shading correction tables TB22 and TB3 will be described.

  Specifically, at the data acquisition time T1 for backside shading correction, the correction data K (x) as shown by the equation (1) is obtained, and the shading correction table TB22 is created to store the memory (stored in the controller 9). Part).

  On the other hand, data corresponding to the function B (x) as shown in Expression (5) is stored in the correction table TB3.

  Data regarding this function B (x) is acquired at a time different from the time T1 when the shading correction table TB22 is created.

  Further, the function B (x) represents the original pixel value P (x) that reflects only the amount of light received from the light source 21 without being affected by the light from the light source 11 and the influence of the light from the light source 11. 2 is a function obtained for each position x with respect to the pixel value Q (x) reflecting the amount of light received when the light from the light source 21 is also received. FIG. 16 is a diagram illustrating the relationship between P (x) and Q (x).

  In other words, the function B (x) is a function obtained by determining the ratio between the value P (x) and the value Q (x) for each position x of the image sensor 25. Here, the value P (x) is an image sensor in a state where the light from the light source 11 does not reach the image sensor 25 and the light from the light source 21 is reflected by the back shading correction plate 52 and reaches the image sensor 25. This is a value corresponding to the amount of light received by each of the 25 pixels. On the other hand, the value Q (x) is obtained in each pixel of the image sensor 25 in a state where both the light emitted from the light source 21 and reflected by the back surface shading correction plate 52 and the light from the light source 11 reach the image sensor 25. This value corresponds to the amount of light received.

  For example, the value P (x) is obtained by executing a shading correction operation related to the back surface reading unit 20 at a certain time T3 when there is no influence of light from the light source 11 (specifically, reflection from the back surface shading correction plate 52). By receiving light). Examples of the time T3 include a time point when the front surface reading unit 10 moves and exists at the shading correction position P2. At this time, the value P (x) corresponds to the original value reflecting only the reflected light from the back surface shading correction plate 52. Also, the time T3 may be a time before the time T1, or may be a time after the time T1.

  The value Q (x) is acquired in a state where both the light emitted from the light source 21 and reflected by the back shading correction plate 52 and the light from the light source 11 reach the image sensor 25 at another time T4. Is done. For example, the above-described back surface shading correction operation (the operation of receiving reflected light from the back surface shading correction plate 52) may be performed in a state where the front surface reading unit 10 exists at the position P1. The time T4 may be a time before the time T1 (, T3), or may be a time after the time T1 (, T3).

  Here, as can be seen by comparing FIG. 16 and FIG. 9, the value (ratio) obtained by dividing the value P (x) by the value Q (x) is the original value R (x) included in the value L (x). ) Ratio.

  Therefore, a correction process as shown in the following equation (6) is performed on the value of each pixel value M (x) acquired when the reading operation is performed, and the corrected pixel value N (x) is obtained. calculate. That is, the pixel value M (x) is corrected by using the value K (x) in Expression (1) and the value B (x) in Expression (5).

  As described above, in the back surface shading correction processing related to the back surface reading unit 20, it is also possible to reduce the influence of light from the light source 11 by executing the shading correction operation based on the two shading correction tables TB22 and TB3. is there.

  Note that, in the above formulas (5) and (6), the fluctuation of the amount of sneak light due to the fluctuation of the position y is not taken into consideration. Therefore, the ratio data B (x) corresponding to the equation (5) is created and held (stored) for each of various positions y, and the ratio data B (x, y) for each position y is stored. Based on the above, a shading correction process similar to that of Expression (6) may be executed.

<4. Other>
Although the embodiments of the present invention have been described above, the present invention is not limited to the contents described above.

  For example, in the first and second embodiments, the case where the value G fluctuates in accordance with the fluctuation of the position y is illustrated. However, the present invention is not limited to this. If the influence on the backside shading correction is relatively slight, the value G may be determined as a fixed value.

  In each of the above embodiments, the copying apparatus is exemplified as the image reading apparatus. However, the present invention is not limited to this, and other types of apparatuses may be used. For example, the image reading apparatus according to the present invention may be a scanner apparatus having only a scan function, or conversely, a multi-function machine (multi-function machine) having various functions (facsimile communication function, etc.) in addition to the scan function. -It may also be called a function peripheral.

DESCRIPTION OF SYMBOLS 1 Copy apparatus 3 Scanner part 5 Print output part 10 Front surface reading unit 11 Light source 15 Image sensor 20 Back surface reading unit 21 Light source 25 Image sensor 30 Original conveyance part 41 Original document tray 43, 44 Platen glass 45, 46 Lower surface side member 48 Ejection Tray 51 Front shading correction plate 52 Back shading correction plate

Claims (6)

An image reading device,
A first reading unit that has a first light source that irradiates the first surface of the document and a first light receiving unit that receives reflected light from the first surface;
A second reading unit that has a second light source that irradiates the second surface of the document and a second light receiving unit that receives reflected light from the second surface;
A first shading correction member that reflects light from the first light source;
First shading correction processing means for performing shading correction on the first light receiving means;
A second shading correction member that reflects light from the second light source;
Reflected light from the second shading correction member is received by a plurality of pixels arranged in the main scanning direction in the second light receiving means, and the second light receiving is performed based on pixel values of the plurality of pixels. Second shading correction processing means for performing shading correction on the means;
With
The first shading correction processing means includes:
Based on the pixel values of the plurality of pixels obtained by receiving the reflected light from the first shading correction member at the plurality of pixels arranged in the main scanning direction in the first light receiving means, Data creating means for creating shading correction data for correcting luminance unevenness related to the first light receiving means;
Correction means for correcting pixel values of the plurality of pixels obtained by receiving reflected light from the first surface during reading of the image of the first surface of the document based on the shading correction data; ,
Have
The first reading means is fixed at a predetermined position;
The second reading means has a first position when reading the image on the second surface and a second position when receiving reflected light from the second shading correction member in the sub-scanning direction. And at least move between
The data creation means estimates the amount of light reaching the first light receiving means from the second light source based on the position of the second reading means in the sub-scanning direction, and obtains the shading correction data. make,
The image reading apparatus according to claim 1, wherein the first shading correction processing unit performs the shading correction based on the shading correction data . The image reading apparatus according to claim 1,
The light from the first light source is received by the first light receiving means in a state where the light from the second light source does not reach the first light receiving means and the light from the second light source reaches the first light receiving means. A storage unit for storing data relating to the amount of light
Further comprising
The image reading apparatus according to claim 1, wherein the first shading correction processing unit performs the shading correction based on data stored in the storage unit. The image reading apparatus according to claim 2,
The image reading apparatus, wherein the data creating unit creates the shading correction data based on data stored in the storage unit. The image reading apparatus according to any one of claims 1 to 3 ,
The data creation means estimates the amount of light reaching the first light receiving means from the second light source based on a time-dependent change curve of the light quantity of the second light source, and creates the shading correction data. An image reading apparatus. The image reading apparatus according to claim 1,
The data creation means includes
The reflected light from the first shading correction member is received by the plurality of pixels in the first light receiving unit, and the shading correction of the first light receiving unit is performed based on each pixel value of the plurality of pixels. While creating the first data,
For each pixel of the first light receiving means, second data relating to a ratio between the first pixel value and the second pixel value respectively obtained at two time points different from the time point when the first data is created is obtained. make,
The first pixel value is such that the light from the second light source does not reach the first light receiving means and the light from the first light source is reflected by the first shading correction member. A value corresponding to the amount of light received by the first light receiving means in a state of reaching one light receiving means,
The second pixel value is such that both the light from the second light source and the light emitted from the first light source and reflected by the first shading correction member reach the first light receiving means. A value corresponding to the amount of light received by the first light receiving means in the state of
The first shading correction processing unit is configured to detect the first light reception based on the first data and the second data when the first reading unit reads the image on the first surface. An image reading apparatus that corrects each pixel value of the plurality of pixels and executes the shading correction. An image reading device,
A first reading unit that has a first light source that irradiates the first surface of the document and a first light receiving unit that receives reflected light from the first surface;
A second reading unit that has a second light source that irradiates the second surface of the document and a second light receiving unit that receives reflected light from the second surface;
A first shading correction member that reflects light from the first light source;
Based on the pixel values of the plurality of pixels obtained by receiving the reflected light from the first shading correction member at the plurality of pixels arranged in the main scanning direction in the first light receiving means, a first data generating means for generating a first shading correction data for correcting luminance nonuniformity for the first light receiving means,
A second shading correction member that reflects light from the second light source;
Based on the pixel values of the plurality of pixels obtained by receiving the reflected light from the second shading correction member by the plurality of pixels arranged in the main scanning direction in the second light receiving means, Second data creating means for generating second shading correction data for correcting luminance unevenness related to the second light receiving means;
With
The first reading means is fixed at a predetermined position;
The second reading means has a first position when reading the image on the second surface and a second position when receiving reflected light from the second shading correction member in the sub-scanning direction. And at least move between
The first data creating means estimates the amount of light reaching the first light receiving means from the second light source based on the position of the second reading means in the sub-scanning direction , and calculates the amount of light. Generating the shading correction data based on the image reading apparatus.

Images