JP2016204100A - Image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation apparatus capable of accurately detecting a position of an end in a width direction of a recording medium.SOLUTION: An image formation apparatus comprises: a first belt conveyor part 5 which conveys sheets; a recording part which discharges ink to the sheets conveyed by the first belt conveyor part 5; an end position detection sensor 60 which is arranged on the upstream side in the sheet conveyance direction with respect to the first belt conveyor part 5 for detecting the position of the end in the sheet width direction; and a facing light source 70 which is arranged so as to face the end position detection sensor 60 via a sheet conveyance path 50 to emit light toward the end position detection sensor 60. The end position detection sensor 60 comprises: a first light emission part 60a which emits light; and a light reception part 60b which receives light emitted from the first light emission part 60a and reflected on a sheet P and light emitted from the facing light source 70.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image forming apparatus provided with an end position detection sensor for detecting the position of an end in the width direction of a recording medium in a recording apparatus such as a facsimile, a copying machine, and a printer.

  As a recording apparatus such as a facsimile, a copying machine, and a printer, an ink jet recording apparatus (image forming apparatus) that forms an image by ejecting ink is widely used because it can form a high-definition image.

  When printing on a recording medium using a recording apparatus, if the recording medium is displaced in a direction orthogonal to the transport direction (recording medium width direction), the printing position is shifted for each recording medium. Therefore, when bookbinding is performed after printing, high accuracy is required for the printing position accuracy for each page. In particular, when an ink jet recording apparatus is used, the ink soaks into the recording medium and tends to show through, and therefore higher accuracy (for example, less than or equal to several millimeters) is required for the printing position accuracy during duplex printing.

  Therefore, conventionally, an image forming apparatus provided with an edge position detection sensor that detects the position of the edge in the width direction of the sheet on the conveyance belt that conveys the sheet (recording medium) by using reflected light is used. . In this image forming apparatus, the position of the edge in the width direction of the paper is detected based on the difference in intensity between the reflected light from the conveyor belt and the reflected light from the paper.

  An image forming apparatus in which an end position detection sensor that detects the position of the end in the width direction of a sheet is provided on a conveyance belt that conveys the sheet is disclosed in, for example, Japanese Patent Application Laid-Open No. H10-228707.

JP 2012-86921 A

  However, in the conventional image forming apparatus, the position of the end in the width direction of the paper can be detected for the paper of the conforming specification, but the position of the end in the width direction may not be detected depending on the color of the paper. There was a point. Specifically, when the paper is white and the conveyor belt is black, the difference in intensity between the reflected light from the paper and the reflected light from the conveyor belt is large. The position is detected. On the other hand, if the paper is black or dark gray and the transport belt is also black, the difference in intensity between the reflected light from the paper and the reflected light from the transport belt is small, and the edge position detection sensor detects the end of the paper in the width direction. The position of could not be detected.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an image forming apparatus capable of accurately detecting the position of the end of the recording medium in the width direction. It is to be.

  In order to achieve the above object, an image forming apparatus having a first configuration according to the present invention includes a belt conveyance unit having a conveyance belt that conveys a recording medium, and is opposed to the belt conveyance unit and conveyed by the belt conveyance unit. A recording unit that ejects ink to the recording medium, and a position that is disposed upstream of the belt conveyance unit in the recording medium conveyance direction and detects the position of the recording medium width direction end that intersects the recording medium conveyance direction. And an opposing light source that is disposed to face the end position detection sensor across the recording medium conveyance path and emits light toward the end position detection sensor. The end position detection sensor includes a first light emitting unit that emits light, and a light receiving unit that receives light emitted from the first light emitting unit and reflected by the recording medium, and light emitted from the counter light source.

  According to the first configuration of the present invention, the position of the end in the width direction of the recording medium can be detected with high accuracy.

1 is a diagram illustrating a structure of a printer according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a structure around a first belt conveyance unit, a recording unit, and a second belt conveyance unit of the printer of FIG. 1. FIG. 2 is a diagram illustrating a structure around an end position detection sensor and a counter light source of the printer of FIG. 1. FIG. 2 is a diagram illustrating a structure around an end position detection sensor and a first belt conveyance unit of the printer of FIG. 1. It is the figure which showed the measurement result of the light intensity detected using a 1st light emission part and a light-receiving part when white paper is passed. It is the figure which showed the measurement result of the light intensity detected using a 1st light emission part and a light-receiving part when black paper is passed. It is the figure which showed the measurement result of the light intensity detected using a 2nd light emission part and a light-receiving part when black paper is passed. It is the figure which showed the measurement result of the light intensity detected using a 2nd light emission part and a light-receiving part when white paper is passed. FIG. 2 is a diagram illustrating a structure around an end position detection sensor and a counter light source of the printer of FIG. 1. FIG. 2 is a diagram illustrating a paper edge position detection control flow in the printer of FIG. 1.

  Embodiments of the present invention will be described below with reference to the drawings.

  An ink jet printer 100 (image forming apparatus) according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the printer 100 has a paper feed cassette 2 a disposed below the inside of the printer body 1. A sheet P, which is an example of a recording medium, is accommodated in the sheet feed cassette 2a. A paper feeding device 3a is disposed on the downstream side of the paper feeding cassette 2a in the paper conveyance direction, that is, above the right side of the paper feeding cassette 2a in FIG. By this sheet feeding device 3a, the sheets P are separated and sent one by one toward the upper right of the sheet feeding cassette 2a in FIG.

  A manual paper feed tray (recording medium stacking unit) 2 b is provided outside the right side surface of the printer main body 1. On the manual paper feed tray 2b, paper of a size different from that of the paper P in the paper feed cassette 2a, a recording medium that is difficult to pass through the bent conveyance path, and a recording medium that is desired to be manually fed one by one are placed. Is done. A sheet feeding device 3b is disposed on the downstream side of the manual sheet feeding tray 2b in the sheet conveyance direction, that is, on the left side of the manual sheet feeding tray 2b in FIG. By this sheet feeding device 3b, the sheets on the manual sheet feeding tray 2b are separated and sent one by one toward the left in FIG.

  Further, the printer 100 includes a first paper transport path 4a therein. The first paper transport path 4a is located at the upper right in the paper feeding direction in the case of the paper feed cassette 2a, and is located in the left side of the manual paper feed tray 2b. The paper P delivered from the paper feed cassette 2a is conveyed vertically upward along the side surface of the printer body 1 by the first paper conveyance path 4a, and the paper delivered from the manual paper feed tray 2b is conveyed substantially horizontally to the left. The

  A registration roller pair 13 is provided at the downstream end of the first paper transport path 4a with respect to the paper transport direction. Further, a first belt conveyance unit 5 and a recording unit 9 are disposed downstream of the registration roller pair 13 in the sheet conveyance direction. The paper P sent out from the paper feed cassette 2a (or the manual paper feed tray 2b) reaches the registration roller pair 13 through the first paper transport path 4a. The registration roller pair 13 feeds the paper P toward the first belt conveyance unit 5 while correcting the oblique feeding of the paper P and timings the ink ejection operation performed by the recording unit 9.

  Further, an end position detection sensor 60 for detecting the position of the end of the paper P in the width direction (perpendicular to the paper transport direction) between the registration roller pair 13 and the first belt transport unit 5. And the counter light source 70 is arrange | positioned. The detailed structure around the edge position detection sensor 60 and the counter light source 70 will be described later.

  As shown in FIG. 2, the first belt conveyance unit 5 includes an endless first conveyance belt 8 wound around a first drive roller 6 and a first driven roller 7. The first conveying belt 8 is rotated counterclockwise in FIG. 2 by the first driving roller 6. The paper P sent out by the registration roller pair 13 is held on the transport surface 8a (upper surface in FIG. 2) of the first transport belt 8, and is transported in the direction of arrow X (from right to left) in FIG.

  A first paper suction unit 30 is provided at a location inside the first transport belt 8 and facing the back side of the transport surface 8 a of the first transport belt 8. The first sheet suction unit 30 is provided with a large number of air suction holes 30a on the upper surface, and is provided with a fan 30b inside, so that air can be sucked downward from the upper surface. The first conveying belt 8 is also provided with a large number of air suction holes 8b (see FIG. 4). With the above configuration, the first belt conveyance unit 5 conveys the paper P while adsorbing and holding the paper P on the conveyance surface 8 a of the first conveyance belt 8.

  The recording unit 9 includes line heads 11C, 11M, 11Y, and 11K that record images on the paper P that is attracted and held on the transport surface 8a and transported. Corresponding to the image data information received from an external computer or the like, each line head 11C to 11K sequentially ejects the respective inks toward the paper P attracted to the first transport belt 8, thereby causing the paper P to A full-color image in which four colors of yellow, magenta, cyan, and black are superimposed is recorded.

  A second belt conveyance unit 12 is disposed on the downstream side (left side in FIG. 1) of the first belt conveyance unit 5 with respect to the sheet conveyance direction. The paper P on which the ink image is recorded by the recording unit 9 is sent to the second belt conveyance unit 12, and the ink ejected on the surface of the paper P is dried while passing through the second belt conveyance unit 12.

  The second belt conveyance unit 12 includes an endless second conveyance belt 40 that is wound around a second drive roller 41 and a second driven roller 42. The second transport belt 40 is rotated counterclockwise in FIG. 2 by the second drive roller 41. The sheet P on which an image is recorded by the recording unit 9 and conveyed in the direction of arrow X by the first belt conveyance unit 5 is transferred to the second conveyance belt 40 and conveyed in the direction of arrow Z in FIG.

  A second paper suction portion 43 is provided at a location inside the second transport belt 40 and facing the back side of the transport surface 40 a of the second transport belt 40. The second sheet suction unit 43 is provided with a number of air suction holes 43a on the upper surface and is provided with a fan 43b inside so that air can be sucked downward from the upper surface. The second conveyor belt 40 is also provided with a large number of air suction vents (not shown). With the above configuration, the second belt conveyance unit 12 conveys the paper P while adsorbing and holding the paper P on the conveyance surface 40 a of the second conveyance belt 40.

  As shown in FIG. 1, a decurler unit 14 is provided on the downstream side of the second belt conveyance unit 12 in the sheet conveyance direction and in the vicinity of the left side surface of the printer main body 1. The paper P from which the ink has been dried by the second belt conveyance unit 12 is sent to the decurler unit 14, and the curl generated on the paper P is corrected using a plurality of rollers arranged in the paper width direction.

  A second paper transport path 4b is provided on the downstream side (upper side in FIG. 1) of the decurler unit 14 with respect to the paper transport direction. The paper is discharged from the second paper transport path 4b to a paper discharge tray 15 provided outside the left side surface of the printer 100 through a pair of discharge rollers.

  Next, a detailed structure around the end position detection sensor 60 and the counter light source 70 will be described.

  As shown in FIGS. 1 and 3, the end position detection sensor 60 is disposed on the upstream side in the paper conveyance direction with respect to the first belt conveyance unit 5, and the counter light source 70 is connected to the paper conveyance path 50 (recording medium conveyance). The end position detection sensor 60 is disposed opposite the road).

  Further, a contact glass 61 is disposed immediately below the end position detection sensor 60, and a plurality of transport guide members 65a, 65b, 65c, 65d are provided around the end position detection sensor 60 and the counter light source 70. , 65e are provided. The contact glass 61 and the lower surfaces of the conveyance guide members 65a, 65b, and 65c and the upper surfaces of the conveyance guide members 65d and 65e constitute a part of the sheet conveyance path 50.

  A paper sensor 62 that detects the presence or absence of the paper P is disposed between the end position detection sensor 60 and the registration roller pair 13. The paper sensor 62 is a sensor using, for example, infrared light, and does not have a function of detecting the position of the edge of the paper P like the edge position detection sensor 60, but the paper sensor 62 does not depend on the color of the paper P. The presence or absence of P can be detected. The paper sensor 62 is configured to transmit a detection signal corresponding to the detection result to the control unit 64 described later. Note that, unlike the edge position detection sensor 60, the paper sensor 62 only needs to be able to detect only one point (or one region) of the paper P, for example.

  As shown in FIG. 4, one edge position detection sensor 60 is arranged on each side of the sheet width direction (left and right direction in FIG. 4), and each edge position detection sensor 60 is located more than the sheet passage area. It is formed short in the paper width direction. The edge position detection sensor 60 includes a large number of first light emitting units 60a that emit light and light receiving units 60b that receive the light emitted from the first light emitting units 60a and reflected by the paper P in the paper width direction. It consists of a single contact image sensor. As shown in FIG. 3, the end position detection sensor 60 is electrically connected to a control unit 64 that controls the operation of the entire printer 100.

  For example, when white paper P is passed, the intensity of light received by the light receiving unit 60b is as shown in FIG. That is, when the paper P is white, the intensity of the reflected light that is emitted from the first light emitting unit 60a and reflected by the paper P is relatively high. Therefore, the measurement is performed by the light receiving unit 60b located at a position corresponding to the inside of the paper P. The emitted light intensity is relatively high (higher than the threshold value α). Further, since the light emitted from the first light emitting unit 60a is not reflected by the paper P outside the paper P, the light intensity measured by the light receiving unit 60b located at a position corresponding to the outside of the paper P is relatively low. (It becomes lower than the threshold value α). Therefore, it is possible to detect the position of the end portion in the width direction of the paper P based on the light intensity change point (position where the light intensity crosses the threshold value α) measured by the light receiving unit 60b.

  On the other hand, for example, when passing black or dark gray paper P, the intensity of light received by the light receiving unit 60b is as shown in FIG. That is, when the paper P is black or dark gray, the intensity of the reflected light emitted from the first light emitting unit 60a and reflected by the paper P is relatively low, so that the light receiving unit located at a position corresponding to the inside of the paper P The light intensity measured at 60b is relatively low (below the threshold value α). Further, outside the paper P, as in the case where the paper P is white, the light intensity measured by the light receiving unit 60b located at a position corresponding to the outside of the paper P is relatively low (below the threshold value α). . For this reason, it is difficult to detect the position of the end in the width direction of the paper P.

  Note that the detection of the edge in the width direction of the sheet P by the first light emitting unit 60a and the light receiving unit 60b is performed only once for one sheet.

  As shown in FIG. 3, the counter light source 70 is arranged along the paper width direction (left-right direction in FIG. 4) and includes a plurality of second light emitting portions 71 made up of light emitting elements such as LEDs, and extends in the paper width direction and second. A mounting substrate 72 on which the light emitting unit 71 is mounted, and a diffusion plate 73 that extends in the paper width direction and is disposed in the light emitting direction of the second light emitting unit 71 are included. The second light emitting unit 71 is electrically connected to the control unit 64 via the mounting substrate 72. The second light emitting unit 71 and the diffusing plate 73 are disposed at a position farther from the paper conveyance path 50 than the first light emitting unit 60 a of the end position detection sensor 60. Thereby, since the light emitted from the second light emitting unit 71 is made uniform, the number of the second light emitting units 71 can be made smaller than the number of the first light emitting units 60 a of the end position detection sensor 60.

  Further, the second light emitting unit 71 is disposed so as to emit light toward the light receiving unit 60 b of the end position detection sensor 60. Therefore, for example, when passing black or dark gray paper P, the intensity of light received by the light receiving unit 60b is as shown in FIG. That is, outside the sheet P, the intensity of light emitted from the second light emitting unit 71 and passing through the outside of the sheet P and measured by the light receiving unit 60b located at a position corresponding to the outside of the sheet P becomes relatively high. (It becomes higher than the threshold value α). In addition, since most of the light emitted from the second light emitting unit 71 and applied to the paper P is absorbed by the paper P inside the paper P, the light receiving unit 60b located at a position corresponding to the inside of the paper P. The light intensity measured at is relatively low (below the threshold value α). Therefore, it is possible to detect the position of the end portion in the width direction of the paper P based on the light intensity change point (position where the light intensity crosses the threshold value α) measured by the light receiving unit 60b.

  On the other hand, for example, when white paper P is passed, the intensity of light received by the light receiving unit 60b is as shown in FIG. That is, outside the paper P, as in the case where the paper P is black or dark gray, the light intensity measured by the light receiving unit 60b located at a position corresponding to the outside of the paper P is relatively high (beyond the threshold value α). Higher). Further, inside the paper P, most of the light emitted from the second light emitting unit 71 and applied to the paper P passes through the paper P and reaches the light receiving unit 60b, so that the light reaches the position corresponding to the inside of the paper P. The light intensity measured by the light receiving unit 60b located is relatively high (higher than the threshold value α). For this reason, it is difficult to detect the position of the end in the width direction of the paper P.

  The detection of the edge in the width direction of the paper P by the counter light source 70 and the light receiving unit 60b is performed only once for one paper.

  Further, as shown in FIG. 9, at least the second light emitting unit 71 of the counter light source 70 is not disposed on the optical axis L1 of the first light emitting unit 60a. As a result, regardless of the presence or absence of the transport guide member 65d and whether or not the transport guide member 65d has translucency, the light emitted from the first light emitting unit 60a is reflected by the surface of the second light emitting unit 71 and received. It is possible to suppress the light received by the part 60b. Note that since the diffusion plate 73 transmits 99% or more of light, it may be arranged on the optical axis L1 (see FIG. 9) of the first light emitting unit 60a, but on the optical axis L1 of the first light emitting unit 60a. It is preferable that they are not arranged.

  Further, the transport guide member 65d is disposed on a line L2 connecting the first light emitting unit 60a and the second light emitting unit 71 (see FIG. 9). Thereby, it is possible to further suppress the light emitted from the first light emitting unit 60a from being reflected by the surface of the second light emitting unit 71 and being received by the light receiving unit 60b. The conveyance guide member 65d is formed of a member that does not have translucency, or a member (low reflectivity member) made of black or the like that hardly reflects the light emitted from the first light emitting unit 60a.

  Next, paper edge position detection control in the printer 100 of the present invention will be described. The paper edge position detection control procedure will be described along the steps of FIG. 10 with reference to FIG. Note that the sheet edge position detection control described below is executed by controlling the operations of the sheet sensor 62, the edge position detection sensor 60, the counter light source 70, and the like based on a control signal from the control unit 64.

  First, when the user presses the start switch on the operation panel (operation unit) of the printer 100 or receives a print start signal from an external computer or the like, the control unit 64 causes the paper sensor 62 to receive the paper P in step S1. The presence or absence of is detected. When the paper sensor 62 does not detect the paper P in step S1, a paper no signal is transmitted from the paper sensor 62 to the control unit 64, and the paper detection operation in step S1 is repeated. When the paper sensor 62 detects the paper P in step S1, a paper presence signal is transmitted from the paper sensor 62 to the control unit 64, and the process proceeds to step S2.

  In step S2, the control unit 64 emits light from the first light emitting unit 60a. In step S <b> 3, a signal based on the intensity of light received by each light receiving unit 60 b is transmitted from the end position detection sensor 60 to the control unit 64. At this time, as described above, for example, when the white paper P is passed, the position of the end portion in the width direction of the paper P can be detected by the control unit 64. On the other hand, for example, when black or dark gray paper P is passed, it is difficult for the control unit 64 to detect the position of the end in the width direction of the paper P.

  It should be noted that the time from when the paper presence signal is transmitted to the control unit 64 in step 1 until light is emitted from the first light emitting unit 60 a in step 2 is between the paper sensor 62 and the edge position detection sensor 60. It is set as appropriate based on the distance, the paper conveyance speed, and the like.

  Next, in step S <b> 4, the control unit 64 emits light from the second light emitting unit 71 of the counter light source 70. In step S <b> 5, a signal based on the intensity of light received by each light receiving unit 60 b is transmitted from the end position detection sensor 60 to the control unit 64. At this time, as described above, for example, when black or dark gray paper P is passed, the position of the end portion in the width direction of the paper P can be detected by the control unit 64. On the other hand, for example, when a white paper P is passed, it is difficult for the control unit 64 to detect the position of the end in the width direction of the paper P.

  As described above, the edge position of the paper P is detected, and the paper edge position detection control ends. Thereafter, the control unit 64 ejects ink from the ejection nozzle 18 corresponding to the print area of the paper P based on the detection result.

  In the present embodiment, as described above, the end position detection sensor 60 including the first light emitting unit 60a and the light receiving unit 60b, and the counter light source 70 disposed to face the end position detection sensor 60 with the paper conveyance path 50 interposed therebetween. And comprising. Thereby, when the paper P is white, for example, the position of the edge part of the width direction of the paper P can be detected using the 1st light emission part 60a and the light-receiving part 60b, and the paper P is black or dark, for example In the case of gray, the position of the end of the paper P in the width direction can be detected using the counter light source 70 and the light receiving unit 60b. As a result, regardless of the color of the paper P, the position of the edge in the width direction of the paper P can be detected with high accuracy.

  In addition, as described above, the counter light source 70 includes the second light emitting unit 71 that emits light and the diffusion plate 73 that diffuses the light emitted from the second light emitting unit 71. Thereby, the light radiate | emitted from the 2nd light emission part 71 can reach the light-receiving part 60b in a more uniform state.

  Further, as described above, the second light emitting unit 71 is not disposed on the optical axis L1 of the first light emitting unit 60a. Thereby, since it can suppress that the light radiate | emitted from the 1st light emission part 60a reflects in the 2nd light emission part 71, and injects into the light-receiving part 60b, the misdetection by the light-receiving part 60b can be suppressed.

  In addition, as described above, the conveyance guide member 65d is disposed on the line L2 connecting the first light emitting unit 60a and the second light emitting unit 71. Thereby, since it can suppress more that the light radiate | emitted from the 1st light emission part 60a reflected in the 2nd light emission part 71, and injects into the light-receiving part 60b, it can suppress the misdetection by the light-receiving part 60b more. it can.

  Further, as described above, when the manual paper feed tray 2b on which a plurality of sizes of paper P can be placed is used, various sizes of paper are supplied. It is particularly effective to detect the position with high accuracy.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

  For example, in the above embodiment, an example in which a contact image sensor is used as the edge position detection sensor 60 that detects the position of the edge of the paper P has been described. However, a sensor other than the contact image sensor such as a CCD may be used. Good.

  Further, in the above-described embodiment, it has been described that the present invention is effective when the color of the paper P is black or dark gray. However, the present invention is also effective when a border paper is used as the paper P.

  In the above-described embodiment, the example in which the edge position detection sensors 60 are provided on both sides in the sheet width direction has been described. However, in the case of a printer (image forming apparatus) that uses only standard sheets, the edge position detection sensor 60 is provided. May be provided only on one side in the paper width direction. If configured in this manner, the cost can be reduced.

  Moreover, although the example which does not arrange | position contact glass above the counter light source 70 demonstrated in the said embodiment, you may arrange | position contact glass above the counter light source 70. FIG. If comprised in this way, it can suppress that a dust etc. accumulate on the opposing light source 70. FIG.

  In the above-described embodiment, the ink jet printer 100 has been described as an example. However, the present invention is not limited to the ink jet type, and may be applied to an image forming apparatus such as an electrophotographic copying machine, a printer, a multifunction peripheral, and a facsimile. Is equally applicable.

2b Manual feed tray (recording medium stacking unit)
5 First belt conveyor (belt conveyor)
8 First conveyor belt (conveyor belt)
9 Recording unit 50 Paper transport path (recording medium transport path)
60 end position detection sensor 60a first light emitting unit 60b light receiving unit 65d transport guide member 70 counter light source 71 second light emitting unit 73 diffuser plate 100 printer (image forming apparatus)
L1 Optical axis L2 Line connecting the first light emitting part and the second light emitting part P Paper (recording medium)

Claims (5)

An end position detection sensor that is disposed facing the recording medium conveyance path and detects the position of the end of the recording medium in the width direction of the recording medium that intersects the recording medium conveyance direction;
A counter light source disposed opposite to the end position detection sensor across the recording medium conveyance path and emitting light toward the end position detection sensor;
With
The end position detection sensor includes: a first light emitting unit that emits light; a light receiving unit that receives light emitted from the first light emitting unit and reflected by the recording medium; and light emitted from the counter light source; An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the counter light source includes a second light emitting unit that emits light and a diffusion plate that diffuses the light emitted from the second light emitting unit.   The image forming apparatus according to claim 2, wherein the second light emitting unit is not disposed on an optical axis of the first light emitting unit. A conveyance guide member for configuring the recording medium conveyance path and guiding the recording medium;
The image forming apparatus according to claim 2, wherein the conveyance guide member is disposed on a line connecting the first light emitting unit and the second light emitting unit.   The image forming apparatus according to claim 1, further comprising a recording medium stacking unit on which the recording media having a plurality of sizes can be placed.

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