JP4127148B2 - Image reading device - Google Patents

Description

  The present invention relates to an image reading apparatus provided in a copying machine, a scanner, a facsimile, or the like, and more particularly to monitoring the brightness of a light source that illuminates an image on a recording medium.

  Copiers, scanners, facsimiles, and the like are provided with an image reading device that reads an image on a recording medium. This image reading apparatus has a light source that illuminates a part of an image on a recording medium and a sensor that detects reflected light from the illuminated area. The brightness of the light source changes due to deterioration over time, and the read image may not appropriately reflect the image on the recording medium.

  Therefore, a reference sheet such as white is arranged in the illumination area of the light source, and a change in illuminance in the illumination area is read based on reflected light from the reference sheet. Since the change in illuminance is related to the brightness of the light source, the brightness of the light source can be monitored by monitoring the illuminance. In the case of an apparatus in which a recording medium is conveyed and an optical system for reading an image is fixed, the above-described reference sheet is arranged on the opposite side of the light source with respect to the recording medium. If there is something with high brightness such as white at this position, so-called show-through occurs in which the image on the back side of the recording medium is seen through.

  In Patent Document 1 below, when reading images on a recording medium having images formed on both front and back surfaces, a low-lightness sheet (with low lightness that can prevent back-through by retracting a high-lightness reference sheet for illuminance measurement) For example, a device for arranging a black sheet) in an illumination area is described.

JP 2000-59569 A

  The apparatus described in the above publication corresponds to the case where the illuminance is monitored and the case where the show-through is prevented by replacing sheets with different brightness, and a mechanism for replacing the sheets is required. Also, when using a low-lightness sheet for preventing show-through, illuminance cannot be monitored.

  An object of the present invention is to monitor illuminance while preventing show-through.

  An image reading apparatus according to the present invention is an illumination area of a light source that illuminates an image on a recording medium to be conveyed, and the light source side disposed in an area opposite to the light source with respect to the recording medium in the illumination area The surface has a blue backing member. A detection unit that has sensitivity to the blue color of the backing member and that reads reflected light from the backing member is disposed, and an illuminance monitoring unit that monitors the illuminance change in the illumination area of the light source based on the output of the detection unit is provided.

  Blue is lighter than other colors, ie, red and green, and has less reflection, so that show-through is prevented or reduced. In addition, since blue light is reflected, it is possible to detect this, and illuminance can be monitored. In this way, by using the blue backing member, it is possible to simultaneously monitor illuminance and prevent show-through. In addition, since most of the white light sources are darkened from the blue region, the deterioration of the light sources can be detected early and accurately by monitoring the illuminance in blue.

  Further, the backing member can be provided so as to protrude to at least one of the left and right sides of the region through which the recording medium passes. If the illuminance monitoring is performed by the protruding portion, the illuminance monitoring can be continued even when the recording medium passes through the illumination area.

  If it is determined that the illuminance has changed, this can be notified, the image reading apparatus can be stopped, or the operation of another apparatus related to the apparatus can be requested to stop.

  Furthermore, an edge detection unit that detects that the edge of the recording medium has passed over the backing member can be provided. As a result, the position, orientation, and size of the recording medium can be known.

Another image forming apparatus is in the form of the present invention, an image reading unit that reads an image forming unit for forming an image based on the reference and name Ru image information on a recording medium, an image formed on the recording medium conveyed If, by matching the image information serving as the reference and the read image, the difference therebetween has an image inspection unit for inspecting whether or within a predetermined range, the. Then, the image reading unit includes a light source for illuminating the image on the recording medium, of the light source, reads the reflected light from the recording medium, the red, green, their respective pairs every three colors of blue a line sensor that response, is arranged in the reading range of the line sensor, the recording medium passing through the read range, and blue backing member on the opposite side from the line sensor, the blue of the line sensor by the corresponding line sensors, and before detecting the reflected light from Kiura contact member, and the illuminance monitor section for monitoring a change in the illuminance of the illumination region of the light source based on the reflected light, it includes.

  Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an image forming apparatus 10 of the present embodiment. The image forming apparatus 10 forms an image on the sheet paper 16 in the image forming unit 14 based on the reference image information 12. Further, in this apparatus 10, the image formed on the sheet paper 16 is read by the image reading unit 18, the read image (read image information) 20 and the reference image information 12 are compared by the comparison unit 22, and the reference It is determined whether image formation has been performed according to the image.

  In the image forming unit 14, first, based on the reference image information 12, the toner is transferred onto the sheet paper 16 conveyed from the tray 26 by the printing / transfer unit 24. The sheet paper 16 is conveyed to the fixing unit 28 with the toner transferred, and the toner is fixed on the sheet paper 16 by being heated here. The sheet paper 16 on which the image is formed is conveyed to the image reading unit 18.

  The image reading unit 18 includes a light source 30 that illuminates the image on the conveyed sheet paper 16 and a line sensor 32 that receives reflected light from the illuminated image. The line sensor 32 is a line of three colors of red, blue, and green having at least a dimension capable of reading an image of the maximum size of sheet paper (dimension in the direction orthogonal to the conveyance direction) handled by the image forming apparatus 10 at a time. It consists of sensors 32R, 32B, and 32G. Further, a backing member 36 is disposed in a region that is illuminated by the light source and in which image information is detected by the line sensor 32 and that is opposite to the light source 30 with respect to the conveyance path 34 on which the sheet paper 16 is conveyed. Has been. The surface of the backing member 36 facing the light source, that is, the surface on the side of the conveyance path 34 is blue, and the blue surface is disposed so as to be substantially in contact with the back surface of the sheet paper 16 that has been sent. The

  The sheet paper 16 that has passed through the image reading unit 18 is sent to the double-sided tray 37 when image formation on the first side of double-sided printing is completed, and is sent again to the image forming unit 14 from here to the image on the second side. Formation is made.

  FIG. 2 is a view of the image reading unit 18 as viewed from above in FIG. The sheet paper 16 is conveyed in the direction of the arrow in the figure, with the surface on which the image is formed in the image forming unit being the front side in the figure. The backing member 36 is disposed on the lower side of the sheet paper 16, and both ends of the backing member 36 are protruded from the end of the sheet paper 16. In order to make the backing member 36 protrude from the end of the sheet paper 16 with respect to all the dimensions of the sheet paper 16 to be sent, it is longer than the sheet paper having the maximum width handled by the image forming apparatus 10. Have dimensions. Of the above-described line sensors 32, at least the blue line sensor 32B has a dimension capable of reading a portion of the backing member 36 protruding from the sheet paper 16. The image information of the protruding portion of the backing member 36 is sent to the monitoring unit 38 (see FIG. 1). The blue color of the backing member 36 is constant. If there is a change in the output of this portion, it is estimated that the illuminance on the surface of the sheet paper 16 in addition to the backing member 36 has changed. As a cause of the change in illuminance, a change in brightness of the light source 30 is a promising candidate. Whether the brightness of the light source 30 is changed by monitoring the output of the blue line sensor 32 by the monitoring unit 38. Can be monitored. If there is a change in the illuminance on the surface of the backing member 36B substantially, that is, exceeding a predetermined range of allowable value, the notification unit 40 notifies the operator of the image forming apparatus 10 and the person in charge of maintenance and management. . If the change in illuminance can be corrected by image processing, the correction unit 42 performs so-called shading correction. The relationship between shading correction and illuminance change notification is, for example, performing shading correction before reaching a predetermined allowable value, and performing notification regarding illuminance change while performing shading correction after reaching the allowable value. can do.

  Further, the edge detection unit 44 detects the leading edge or the trailing edge of the sheet paper 16 by using a part of the output of the blue line sensor 32B. The reference position of the read image information 20 can be specified using the detected edge. Further, if this edge detection is performed at at least two places of the line sensor 32B, it can be detected that the sheet paper 16 is being fed obliquely, that is, so-called skewed.

  The reason why the front surface of the backing member 36 is blue will be described below. As described above, the backing member 36 serves as a reference for monitoring illuminance, and a certain brightness is required for this purpose. On the other hand, since it is in contact with the back side of the passing sheet paper 16, if the backing member has a high brightness, if the image is formed on the back side of the sheet paper 16, the image is seen through the front side. End up. If the backing member is blue, the illuminance can be monitored, and the brightness is lower than that of red or green, so that the show-through hardly occurs. This is one of the reasons why the color of the backing member 36 is blue. Furthermore, since the light source that is currently used generally deteriorates blue more quickly than other colors, the temporal change of the light source can be accurately determined by monitoring the blue color. This is the second reason for adopting blue. As described above, when the blue color deterioration occurs early, other red and green colors are not corrected uniformly in the same manner as the blue output when performing the above-described shading correction. It is preferable to estimate and correct the amount of color change. For this purpose, the temporal change characteristics of the light source used are stored in advance for each color, and the amount of change in other colors is estimated from the amount of change in blue.

  Ordinarily, the amount of light can be monitored in blue, and shading correction can be performed by setting the illuminated portion to be white at a predetermined time. The timing of correction may be when the amount of light monitored in blue drops below a predetermined value, when the cumulative operating time of the apparatus reaches a predetermined time, or during periodic inspections. In order to make the illuminated part white when correcting shading, for example, a white area is provided in a part of the backing member that is not normally illuminated, and the white area is arranged in the illuminated part by moving the backing member. To be. Alternatively, it is also conceivable to perform shading correction while stopping or passing a white medium (sheet paper or the like) through the illuminated part, and then removing the white medium.

  In the case where the medium is a sheet paper, in this embodiment, since the double-sided tray 37 is provided, this paper can be used again for printing.

  Since the backing member 36 is blue with relatively low brightness, it is possible to prevent characters on the back side of the sheet paper 16 from being seen through, but the sheet paper 16 is thin and easy to see through. In some cases, the blue color itself may be transparent. In this case, the read image can be corrected by subtracting a predetermined amount of blue output from the read image information 20. A constant value can be set for the subtraction amount. Also, a table in which the sheet paper type is associated with the subtraction value is stored, and when the sheet paper is set on the tray 26, the sheet paper type is input, and the amount is subtracted based on the correspondence table. Can be done. In addition, the operator can manually input the subtraction amount.

  As described above, the backing member 36 is disposed so as to protrude from the end of the largest sheet paper 16 to be handled. Thus, even when the sheet paper 16 passes over the backing member 36, the illuminance is monitored. Can continue. In particular, when using continuous paper called a continuous book instead of sheet paper, monitoring can be performed even when the paper is passing. Even when a continuous book is used, continuous illumination monitoring can be performed as long as the backing member 36 protrudes from at least one of the left and right sides.

  On the contrary, when the sheet paper is handled and it is sufficient to monitor the illuminance between the fed sheet papers, that is, it is sufficient to perform intermittent monitoring, the backing member 36 is a sheet of the maximum size. There is no need to protrude from the width of the paper.

In the above embodiment, the blue line sensor which is one of the three color line sensors of the color image reading apparatus is used. However, a separate line sensor may be used for illuminance monitoring . Also of al, the image forming apparatus of the embodiment, but is intended to perform electrophotographic image formation or xerographic, the other method can be applied for example also to an inkjet.

  Blue in this embodiment preferably has a wavelength in the wavelength range of 350 nm to 500 nm. Furthermore, it is preferable that the sensor whose wavelength is green is included in a wavelength band of 350 nm to 450 nm where the sensitivity is not present. Furthermore, it is preferably included in a wavelength band of 400 nm to 450 nm where the optical design is good.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. It is a figure which shows the outline when an image reading part is seen from the information of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Image forming apparatus, 14 Image forming part, 16 Sheet paper, 18 Image reading part, 30 Light source, 32 Line sensor, 32B Blue line sensor, 36 Backing member, 38 Monitoring part, 40 Notification part, 42 Correction part, 44 Edge detector.

Claims (6)

The image on the recording medium conveyed illuminated by the light source, the light reflected from the image an image reading apparatus for reading by the line sensor,
An illumination area of the light source, with respect to the recording medium in the illumination region, is located on the opposite side of the region of the light source, a surface of the light source side and the blue backing member,
A detector that has sensitivity in the blue wavelength region of the backing member and reads reflected light from the backing member;
An illuminance monitoring unit that monitors an illuminance change in an illumination area of the light source based on the output of the detection unit;
An image reading apparatus. The image reading apparatus according to claim 1,
The backing member has a portion that protrudes to at least one of the left and right in the conveyance direction of the recording medium in the region through which the recording medium passes,
The detection unit is a line sensor having a dimension that allows the reflected light from the entire width of the backing member to be read .
Image reading device. 3. The image reading apparatus according to claim 1, wherein the line sensor that reads reflected light from the image includes a line sensor corresponding to each of three colors of red, green, and blue, and the detection is performed. The image reading apparatus is a line sensor corresponding to blue among the line sensors corresponding to each color . The image reading apparatus according to claim 3, further comprising an edge detection unit that detects an edge of the conveyed recording medium based on an output of the detection unit. The image reading apparatus according to claim 3, wherein the image information read by the line sensor corresponding to each of the three colors is corrected so that information relating to blue is reduced by a predetermined amount. Reader. An image forming unit that forms an image based on the reference and name Ru image information on a recording medium,
An image reading unit for reading an image formed on the recording medium to be conveyed;
By matching the image information serving as the reference and the read image, and an image inspection unit the difference between the two is to check whether within a predetermined range,
In an image forming apparatus having
The image reading unit
A light source for illuminating an image on the recording medium;
Of the light source, reads the reflected light from the recording medium, the red, green, a line sensor in which it respectively to correspond to each three colors of blue,
Disposed in the reading range of the line sensor, the recording medium passing through the read range, and blue backing member on the opposite side from the line sensor,
The line sensors corresponding to the blue of the line sensor, before detecting the reflected light from Kiura contact member, the illuminance monitor unit for monitoring a change in the illuminance of the illumination region of the light source based on the reflected light,
An image forming apparatus.

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