JP6017365B2 - Image reader - Google Patents

Description

  The present invention provides an image reading apparatus that corrects a decrease in brightness that appears at both ends of a read image using a light guide for illumination.

  Conventionally, when a customer goes to a financial institution to make a transfer, etc., it is done by themselves using an ATM (Automatic Teller Machine), or it is requested to go to a window with a pre-filled transfer request form and a passbook or cash Divided into two ways.

  In general, an image reading device is always provided next to a contact person at a financial institution or the like, and the contact person uses an image reading device to make a copy of the copy, and a transfer request form. And the reading side of the passbook is read.

In such an image reading apparatus, the image output sometimes fluctuates, and a partial brightness difference may appear in an image obtained by reading. On the other hand, for example, there has been proposed an image reading apparatus capable of realizing appropriate linearity correction and preventing image quality deterioration even when the image output fluctuates due to a change in the light amount of the light source. (For example, refer to Patent Document 1.)
For example, when the paragraph [0033] or the like is seen in the technique of Patent Document 1, as a correction table having a correction amount corresponding to each pixel, a general processing pixel defined at a fixed pixel interval from the top pixel position of the sensor chip. A correction table for chip edge processing and a correction table for chip edge processing that defines pixels around the chip edge in pixel units.

  Further, when the paragraph [0035] of Patent Document 1 is viewed, the description that “the lighting time of the light source 11 turns on a plurality of pulse-controlled light sources corresponding to one cycle of the reading line” is seen, It can be read that light from a plurality of light sources arranged in the main scanning direction is irradiated on the document from the front end of the light guide.

JP 2008-252217 A

  By the way, in the illumination light for illuminating the document of the image reading apparatus, a plurality of illumination lights from a line light source composed of an LED array arranged along the main scanning direction of the document, as in Patent Document 1, are arranged in the main scanning direction. Illumination light that emits light from the light source from the front end of the light guide, illumination light that diffuses and irradiates light from the light sources at both ends of the light guide arranged linearly in the main scanning direction, etc. is there.

  In general, in an image reading apparatus that reads an irregularly-shaped original document that is always in the vicinity of a person in charge at a bank or other counter, dirt such as dust enters the background of the read image to confirm the reading width of a white-type original document. In order to prevent this, the member of the document conveyance path facing the reading sensor is often configured in black.

  Further, when a light guide is used for illumination for reading an image with such an image reading apparatus, a phenomenon occurs in which the brightness of both sides of the read image is lower than that of the central portion. As described above, if there is a low-lightness part at both ends of the read image, the shape of characters and numbers printed on the part becomes unclear, resulting in a problem that erroneous recognition occurs in the image recognition process following the read process. .

  However, although Patent Document 1 describes correction of pixel brightness to cope with changes in the light amount of the light source and the like, there is no change in the light amount of the light source when a light guide is used for illumination. Nothing is taken up about the difference in brightness between the central part and both end parts of the read image that occurs.

  The present invention solves the above-described conventional problems, and even if a light guide is used for illumination of an image reading apparatus that is always provided at a bank or other financial institution, it appears at both ends of the read image. An object of the present invention is to provide an image reading apparatus capable of easily correcting a decrease in brightness.

  In order to solve the above problems, an image reading apparatus of the present invention is an image reading apparatus that sequentially reads a data image of a data medium in the main scanning direction in the sub-scanning direction while guiding light from the light source. A light guide that diffuses and illuminates the data image of the data medium; and a data medium transport system that is disposed opposite the light guide to transport the data medium and forms a black background for the data medium. An optical sensor for reading the data image illuminated by the light guide of the data medium conveyed in the sub-scanning direction by the data medium conveying system in the main scanning direction, and forming an image on the optical sensor; And correction means for correcting the brightness of pixels in a predetermined range at both ends in the main scanning direction of the data image based on a black background pixel number correspondence table.

  In this image reading apparatus, the data medium is, for example, a slip or a passbook, and the light guide is made of, for example, a rod-shaped light diffusing member arranged along the main scanning direction of the data medium. For example, the light source is disposed at both ends of the light guide, and the black background pixel number correspondence table corresponds to, for example, the number of pixels in the predetermined range and the number of pixels of the black background following the number of pixels. The brightness increase degree set for each pixel of the number of pixels in the predetermined range is described in the matrix frame, and the correction unit, for example, for each pixel of the number of pixels in the predetermined range of the black background pixel number correspondence table The brightness of the pixel is corrected based on the set brightness increase.

  Next, in order to solve the above-described problem, an image reading method of the present invention includes a light source, a light guide for diffusing light from the light source to illuminate a data image on a data medium, and a light guide on the light guide. A data medium transport system arranged opposite to transport the data medium to form a black background for the data medium, and the light guide of the data medium transported in the sub-scanning direction by the data medium transport system A light sensor that sequentially reads the data image to be illuminated in the main scanning direction in the sub-scanning direction, and a decrease in brightness that appears at both side edges of the read image of the data image read by the light sensor. In the matrix frame in which the number of pixels in the main scanning direction existing in the lightness reduction portion and the number of pixels of the black background following the end of the number of pixels correspond to each other. Lightness reduction part A table generation step for generating a brightness correction table describing the brightness increase degree set for each pixel of the number of pixels in the main scanning direction, and the brightness set for each pixel of the brightness correction table And a correction step of correcting the brightness of the pixel in the main scanning direction existing in the brightness reduction portion based on the increase degree.

  The light guide is composed of, for example, a rod-shaped light diffusing member disposed along the main scanning direction of the data medium, and the light sources are disposed at both ends of the light guide, for example. Composed.

  Since the present invention can easily correct a decrease in lightness appearing at both ends of a read image even if a light guide is used for illumination of an image reading apparatus that is always provided at a counter of a financial institution such as a bank, It is possible to prevent a problem that erroneous recognition occurs in the subsequent image recognition process.

  Further, since a method of uniformly illuminating the data medium by diffusing light with an inexpensive light guide made of resin can be used, an inexpensive image reading apparatus can be provided.

1 is an external perspective view of an image reading apparatus according to Embodiment 1 of the present invention. FIG. 3 is a cross-sectional view schematically illustrating an internal configuration of the image reading apparatus according to Embodiment 1 with a casing and a lid member removed. FIG. 5 is a diagram illustrating a light source, a light guide, and an operation of an illumination unit arranged in the vicinity of the reflected light incident port of the image scanner of the image reading apparatus according to the first embodiment. FIG. 3 is a diagram illustrating a condensing lens and a CCD, together with a light guide and a data medium, that constitute a reading unit disposed inside and above the reflected light incident port of the image scanner according to the first embodiment. FIG. 3 is a diagram illustrating an image of a data medium formed on a CCD together with a black background around the image scanner according to the first embodiment. FIG. 6 is a diagram for explaining that the cause of a decrease in brightness at both ends of an image of a data medium in the image scanner according to the first embodiment is a surrounding black background. (a) and (b) show how the lightness-decreasing portions at both edges of the paper surface are different for data media with different recording surface widths in order to numerically confirm the phenomenon that the lightness at both edges of the image on the data medium decreases. It is a figure which shows the aspect of the experiment investigated whether it changed. FIG. 8 is a chart (brightness correction table) showing the relationship between the width of the lightness reduction portion at the side end portion of the data medium corresponding to the width of the black background portion based on the experiment shown in FIG. 7. (a) is a circuit block diagram for performing image reading processing of the image reading apparatus according to the first embodiment, and (b) is a flowchart of processing performed by the CCD waveform processing circuit. It is a figure which shows the digital image data of the data medium expand | deployed to the image memory by the image digitizing part of the circuit block shown to Fig.9 (a). It is a figure which shows the example in case a black solid image exists in the center part of a data medium.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[Example 1]
FIG. 1 is an external perspective view of the image reading apparatus according to the first embodiment. As shown in FIG. 1, the image reading apparatus 1 has an internal device covered by a casing 2 formed continuously at the bottom and the rear and a lid member 3 formed continuously at the top and the front. Yes.

  The front portion of the lid member 3 forms an inclined surface 4, and the central portion of the inclined surface 4 is largely cut away. An operation panel unit 5 is disposed on the inclined surface 4 on the right side of the notch, and the notch has a slip port 6 and a passbook port 7 for loading and unloading slips and passbooks as data media inside the apparatus. Is arranged.

  FIG. 2 is a cross-sectional view schematically showing an internal configuration of the image reading apparatus 1 with the casing 2 and the lid member 3 removed. In the figure, the same components as in FIG. 1 are given the same reference numerals as in FIG. A general conveyance path 9 is formed on the upper surface of the lower frame 8 shown in FIG.

  Two slip transport roller pairs 12 are arranged on the slip transport path 11 following the slip port 6 with the slip transport path 11 interposed therebetween. Further, two pairs of passbook transport rollers 14 are arranged on the passbook transport path 13 following the passbook port 7 with the passbook transport path 13 in between.

  The terminal ends of the slip conveyance path 11 and the passbook conveyance path 13 join the general conveyance path 9 respectively. A separator 15 that rotates up and down is arranged at the junction. A print head 16, an image scanner 17, and a page turning unit 18 are located above the general conveying path 9 following the back of the apparatus (right side of the figure) from the arrangement portion of the separator 15 from the front of the apparatus (left side of the figure) to the back. Is arranged.

  In the arrangement portion of the image scanner 17 and the page turning unit 18, two pairs of conveyance rollers 19 and 21 are arranged on both sides of the general conveyance path 9. Between the conveyance roller pair 19 and 19, a reflected light incident port 22 that is a reading unit of the image scanner 17 protrudes into the general conveyance path 9 from above.

  A black roller 23 is disposed on the lower surface (the upper surface of the lower frame 8) of the general conveyance path 9 facing the reflected light incident port 22. The image scanner 17 includes a light source, a light guide, a condensing lens, a CCD (Charge Coupled Device), and the like, which will be described in detail later.

  In this image reading apparatus 1, when a data medium is inserted from the slip port 6 or the passbook port 7, the image recording unit 17 reads the data recording surface of the data medium and performs printing by the print head 16 as necessary.

  Then, when the processing inside them is completed, the pair of conveying rollers in each part is rotated in reverse, the data medium is discharged to the outside via the slip port 6 or the passbook port 7 and returned to the customer. Said separator 15 is a mechanism part which selects the discharge direction at the time of returning a data medium.

  FIG. 3 is a diagram showing a light source and a light guide that constitute an illumination unit arranged in the vicinity of the reflected light incident port 22 of the image scanner 17, and an operation thereof. The light guide 24 shown in FIG. 3 is composed of a rod-shaped light diffusing member arranged along the main scanning direction (the depth direction in FIG. 2) of the data medium (slip or passbook).

  Light sources 25 are disposed at both ends of the light guide 24. Each of the light sources 25 includes two high-intensity LEDs (light emitting diodes) 26 and a substrate 27 on which these high-intensity LEDs 26 are mounted.

  The light guide 24 guides the light from the light source 25 along the axis of the light guide 24 as indicated by the broken line a, and diffuses the light to the outside as indicated by the broken line b, so that the data recording surface of the data medium Illuminate the data image. The illumination light 28 diffused from the light guide 24 and irradiated to the outside is optically designed so that the light intensity is almost uniform over the entire surface of the light guide 24.

  FIG. 4 is a view showing a condensing lens and a CCD constituting a reading unit disposed inside and above the reflected light entrance 22 of the image scanner 17 together with a light guide 24 and a data medium. 4, illustration of the light sources 25 at both ends of the light guide 24 shown in FIG. 3 is omitted.

  As shown in FIG. 4, the data recording medium d (slip or passbook) is illuminated on the data recording surface d in the main scanning direction indicated by the alternate long and short dash line c by the illumination light 28 diffused and radiated from the light guide 24. The reflected light 30 reflected by the data recording surface d is converged by the condenser lens 31 and forms an image on the light receiving surface of the CCD 32.

  In addition to the data recording surface d of the data medium 29, the image data that forms an image on the light receiving surface of the CCD 32 also forms image data of the background data e1 and e2 outside the data recording surface d as reflected light 30 '. .

  As described above, the image data read from the data medium 29 such as a slip or a passbook to the CCD 32 of the image scanner 17 is later inclined by the inclination of the outline of the white background of the data medium 29 by OCR (Optical Character Recognition / Reader) processing. Image correction such as line correction is performed.

  In this OCR process, the opposite surface facing the reading unit (reflected light incident port 22) of the image scanner 17 has a black roller surface like the black roller 23 so that the white edge portion of the data medium 29 becomes clear. The lower surface of the general conveyance path 9 in the vicinity thereof (the upper surface of the lower frame 8) is also a black conveyance surface.

  When the data medium is read by the image scanner 17, the black roller 23 operates so as to press the data medium against the reading unit (reflected light incident port 22) with a constant pressure, so that the read data is wrinkled on the paper on the reading surface. It is made difficult to be affected by.

  As a result, the periphery of the image of the data medium 29 read by the image scanner 17, that is, the CCD 32 (the portions of the background data e1 and e2) has a black background. By the way, as described above, low-lightness portions appear at both end portions of a read image read by such an image reading apparatus 1.

  FIG. 5 is a diagram showing an image of the data medium 29 formed on the CCD 32 together with the surrounding black background. As shown in FIG. 5, an image of the data medium 29 is formed in the black background data e1 and e2. The brightness of the side edges 29a and 29b of the image of the data medium 29 is lowered. The brightness reduction rate was about 10% when measured.

  However, the reason why the brightness of the side edges 29a and 29b of the image of the data medium 29 is lowered in this way was tried by changing various illumination methods, but the cause was completely unknown. However, as a result of various discussions here, it was concluded that the surrounding black background was the cause.

  FIG. 6 is a diagram for explaining that the cause of the decrease in the brightness of the both side edges 29a and 29b of the image of the data medium 29 is the surrounding black background. In the illumination light 28 using the light guide 24 shown in FIG. 6, the light once irradiated on the paper surface of the data medium 29 is scattered to the reflected light entrance 22 of the image scanner 17 and to the four sides thereof. At the same time, the light is scattered also on the optical surface of the light guide 24. This scattered light irradiates the paper surface again as reflected light.

  As a result, the central portion of the white paper surface portion becomes brighter, and both side edge portions 29a and 29b adjacent to the black background portions e1 and e2 without the data medium 29 have no scattered light from the black background portions e1 and e2. There has been considered a phenomenon in which there is no reflected light that irradiates the paper surface from the light guide 24 again, and the lightness decreases accordingly.

  FIGS. 7 (a) and 7 (b) are experiments of examining how the lightness-decreasing portions at both ends of the paper surface change in a data medium having a different recording surface width in order to confirm the above phenomenon numerically. It is a figure which shows an aspect. The data medium 29-1 in FIG. 9A has a relatively wide recording surface width 33a, and the data medium 29-2 in FIG. 11B has a recording surface width 33b relatively narrow.

  As shown in FIGS. 7 (a) and 7 (b), the data media 29-1 and 29-2 have the left end portions of the insertion ports (the slip port 6 and the passbook port 7), in particular, end positioning members (not shown). The sheet is conveyed while its position is regulated so as to be separated from the left wall surface of the insertion port by a certain distance.

  Therefore, the width of the black background portion e1 adjacent to the left end portions of the data media 29-1 and 29-2 is constant. For this reason, the widths of the lightness reduction portions 29-1a and 29-2a appearing at the left end portions of the data media 29-1 and 29-2 are the same. That is, it was considered that if the width of the black background portion e1 is determined, the widths of the lightness reduction portions 29-1a and 29-2a are also determined.

  However, when attention is paid to the right end portions of the data media 29-1 and 29-2, the widths of the lightness reduction portions 29-1b and 29-2b appearing at the right end portions are changed. Therefore, in FIG. 7A, the black background portion e1 in the forward scanning line f in the main scanning direction, the range on the scanning line of the lightness reduction portion 29-1a, and the black background portion e2 in the backward scanning line g, the lightness reduction portion. The range on the scanning line of 29-1b was examined by the number of pixels.

  7 (a) and 7 (b), the forward scanning line f and the backward scanning line g are shown in two separated states for convenience of illustration and explanation. Indicates the same main scanning line.

  Similarly in FIG. 7B, the black background portion e1 in the forward scanning line f in the main scanning direction, the range on the scanning line of the lightness reduction portion 29-2a, and the black background portion e2 in the scanning line g in the backward pass. The range on the scanning line of the lightness reduction portion 29-2b was examined by the number of pixels.

  As a result, the widths of the lightness decreasing portions 29-1a, 29-1b, 29-2a, 29-2b at both ends of the data medium 29 (29-1, 29-2) (length on the scanning line, the same applies hereinafter). Is proportional to the width of the black background portions e1 and e2 up to a certain range width of the adjacent black background portions e1 and e2, and it has been found that the influence of the decrease in brightness becomes constant beyond the certain range.

  FIG. 8 is a chart showing the relationship with the width of the lightness reduction portion at the side end portion of the data medium corresponding to the width of the black background portion, created based on the above-described experiment. FIG. 8 shows the number of dots of black pixels corresponding to the width of the black background portions e1 and e2 in the vertical h direction, and the side of the data medium 29 that is affected by the decrease in brightness due to the number of black pixel dots in the horizontal i direction. The order of dots in a pixel row (referred to as white pixels) at the end portions 29a and 29b is shown.

  In the chart of FIG. 8, “+ x%” shown in the data column in which the number of dots of each black pixel corresponds to the order of the dots of each white pixel column represents the lightness reduction rate “−x%” with an inverted sign. Yes. That is, the chart of FIG. 8 is a correspondence table showing the number of black pixel dots and the brightness reduction rate of the white pixel dot row affected by the brightness reduction, and also shows the correction value for the brightness reduction of the white pixel dot row. It is also a brightness correction table.

  Since it has been found through experiments that the brightness of white pixels does not decrease unless the number of dots of black pixels continues for a certain number (29 dots) or more, in the brightness correction table of FIG. The number of dots of black pixels increasing with each dot is shown up to 100 dots.

  After the number of black pixel dots exceeds 100 dots (about 10 mm long), the range of pixel rows in which the brightness of white pixels decreases is constant, so the maximum number of black pixel dots is 100 dots. Yes. That is, when the number of black pixel dots exceeds 100 dots, the brightness correction of the white dot row may be performed with the same correction value as when the number of black pixel dots is 100 dots.

  Since the number of dots in the white dot row that is affected by the lightness reduction corresponding to the number of black pixels exceeding 100 dots is up to the 400th dot (42.3 mm), in the lightness correction table of FIG. The white dots arranged in the direction of are ranked up to the 400th dot.

  As described above, the maximum area of the white dot row that is affected by the decrease in brightness due to the number of continuous dots of the adjacent black pixels is 400 dots. Therefore, correction values up to 400 dots in the white dot row are stored in the brightness correction table. Is set.

  According to this brightness correction table, for example, when the number of consecutive dots of black pixels is 31 “★”, the correction value that brightens the first dot by + 6% in the white pixel dot row of the data medium adjacent to it. The brightness is corrected in such a manner that the second dot is multiplied by a correction value that brightens + 6%, the third dot is multiplied by a correction value that brightens + 5%, and so on.

  FIG. 9A is a circuit block diagram for performing the image reading process of this example, and FIG. 9B is a flowchart of the process performed by the CCD waveform processing circuit. In FIG. 9A, first, the image of the data medium 29 read by the CCD 32 of the image scanner 17 is sent to the A / D converter 34 as an analog signal line-sequentially in the main scanning direction.

  The A / D converter 34 converts the input analog signal into, for example, a 256-gradation digital signal and sends it to the CCD waveform processing circuit 35. The CCD waveform processing circuit 35 starts the CCD waveform processing shown in FIG. 9B (step S101).

  This CCD waveform processing is generally performed, and first, shading correction is performed on the peripheral portion of the image (step S102). In this processing, correction is performed using a correction value that is uniquely determined by the characteristics of the condenser lens 31.

  Then, the CCD waveform processing is completed (step S104). The digital image data for which the CCD waveform processing has been completed is sent to the digital data conversion unit 36.

  The digital data converting unit 36 includes an image memory (not shown), and develops digital image data for which CCD waveform processing has been completed in this image memory. The image correction circuit 37 performs lightness correction on the digital image data developed in the image memory.

  FIG. 10 is a diagram showing digital image data (29) of the data medium 29 developed in the image memory. The image correction circuit 37 reciprocates and scans the digital image data 29 including the black dots of the background data e1 and e2 in the main scanning direction as indicated by arrows j and k.

  In the forward scan indicated by the arrow j, the number of black dots in the background data e1 is counted, and when the scanning object moves from the black background to the white dot portion 29a of the digital image data 29, the first white dot is changed to the main dot. Lightness correction of white dot rows on scanning is performed. This lightness correction is performed based on the lightness correction table shown in FIG.

  Next, in the backward scan indicated by the arrow k, the number of black dots in the background data e2 is counted, and when the scan object moves from the black background to the white dot portion 29b of the digital image data 29, the first dot white The brightness correction of the white dot row on the main scan from the dot is performed. This lightness correction is also performed based on the lightness correction table shown in FIG.

  Note that the number of black dots in the background data e1 is determined by the type of the image reading apparatus, so that the left end is restricted. For example, the number of black dots is set to 29 dots in advance and the number of forward black dots is set. Counting may be omitted.

  Further, the number of black dots in the return path is counted when it exceeds 100 dots when counted from the right end, and when the scanning target is changed from black dots to white dots, the brightness correction table shown in FIG. Based on the correction value when the number of black dots continues from the first white dot to 100 dots, the brightness correction of the white dot row on the main scan is performed.

  Needless to say, in the above-described embodiments, various modifications can be made without departing from the scope of the embodiment. For example, FIG. 11 shows an example in the case where a black solid image exists in the center portion of the data medium 29.

  In the case of FIG. 11, the number of black dots in the background data e1 is counted in the forward main scan indicated by the arrow j, and when the scanning object moves from the black background to the white dot portion 29a, the first white dot From the black dot image 38, the number of black dots in the black solid image 38 is counted, and when the scanning object moves from the black dot to the white dot portion 29b ', the first dot white is corrected. Lightness correction from dot to white dot row is performed.

  In the backward scan indicated by the arrow k, the number of black dots in the background data e2 is counted, and the brightness correction of the white dot row of the white dot portion 29b is performed based on the count and the brightness correction table. The number of black dots of the solid image 38 is counted, and the brightness correction of the white dot row of the white dot portion 29a ′ is performed based on the count and the brightness correction table.

  In this way, a method of uniformly illuminating the data medium by diffusing light with an inexpensive light guide made of resin, the phenomenon that the brightness of both ends that occurs in that case is reduced to one main scanning line Since the brightness correction can be performed only by reciprocating scanning every time, an inexpensive image reading apparatus can be provided.

  The present invention can be used in an image reading device that corrects a decrease in brightness that appears at both ends of a read image of the image reading device.

DESCRIPTION OF SYMBOLS 1 Image reader 2 Housing | casing 3 Cover member 4 Inclined surface 5 Operation panel part 6 Voucher slot 7 Passbook slot 8 Lower frame 9 General conveyance path 11 Voucher conveyance path 12 Voucher conveyance roller pair 13 Passbook conveyance path 14 Passbook conveyance roller pair 15 Separator DESCRIPTION OF SYMBOLS 16 Print head 17 Image scanner 18 Page turning unit 19, 21 Carrying roller pair 22 Reflected light entrance 23 Black roller 24 Light guide 25 Light source 26 High-intensity LED (light emitting diode)
27 Substrate 28 Illumination light 29 (29-1, 29-2) Data medium 29a, 29b, 29-1a, 29-1b, 29-2a, 29-2b End 30 Reflected light 31 Condensing lens 32 CCD (Charge Coupled) Device)
33a, 33b Recording surface width 34 A / D converter 35 CCD waveform processing circuit 36 Digital data conversion unit 37 Image correction circuit 38 Solid black image

Claims (7)

In an image reading apparatus that sequentially reads a data image of a data medium in the main scanning direction in the sub-scanning direction,
A light source;
A light guide that illuminates the data image of the data medium by diffusing light from the light source;
A data medium transport system disposed opposite the light guide to transport the data medium and forming a black background for the data medium;
An optical sensor for reading in the main scanning direction the data image illuminated by the light guide of the data medium conveyed in the sub-scanning direction by the data medium conveying system;
Correction means for correcting the brightness of pixels in a predetermined range at both ends in the main scanning direction of the data image formed on the optical sensor based on a brightness correction table;
I have a,
The brightness correction table is set for each pixel of the pixels in the predetermined range in a matrix frame in which the order of the pixels in the predetermined range and the number of pixels of the black background following the pixel column arranged in the order correspond to each other. The brightness increase is described,
An image reading apparatus.   The image reading apparatus according to claim 1, wherein the data medium is a slip or a passbook.   The image reading apparatus according to claim 1, wherein the light guide body is formed of a rod-shaped light diffusing member disposed along the main scanning direction of the data medium.   The image reading apparatus according to claim 1, wherein the light source is disposed at both ends of the light guide. A light source, a light guide for diffusing the light of the light source to illuminate a data image of the data medium, and a black background for the data medium that is disposed opposite the light guide and conveys the data medium A data medium transport system to be formed and reading in the main scanning direction the data image illuminated by the light guide of the data medium transported in the sub scanning direction by the data medium transport system. A sequential optical sensor;
A correction method for correcting a decrease in brightness appearing at both ends of the read image of the data image read by the optical sensor,
Wherein the ranking of pixels in a predetermined range at both ends of the main scanning direction that is present in the portion of the brightness reduction, the matrix in the frame and the number of pixels the black background following the pixel rows arranged in positions that order correspond, the predetermined range A table generation step for generating a brightness correction table in which the brightness increase degree set for each pixel is described;
A correction step of correcting the brightness of the pixels in the predetermined range based on the brightness increase set for each pixel of the brightness correction table;
An image reading method comprising: The image reading method according to claim 5 , wherein the light guide is formed of a rod-shaped light diffusing member arranged along the main scanning direction of the data medium. The image reading method according to claim 5 , wherein the light source is disposed at both ends of the light guide.