Image reading device, and image forming apparatus

Abstract

To provide an image reading device that appropriately controls lighting of light sources and prevents temperature rise during reading processing for various kinds of adjustment.SOLUTION: An image reading device 10 comprises: a reading unit (101) that has light sources 102a, 102b for irradiating a sheet to be conveyed with light, and a light receiving part 105 receiving light emitted from the light sources 102a, 102b and reflected by the sheet, and that reads the sheet on the basis of the reflected light received by the light receiving part 105; and a control unit 20 that turns on the light sources 102, 102b only when the reading unit reads a leading and a rear end of the sheet and a background part around the ends with respect to a conveyance direction of the sheet.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an image reading device that is provided in an image forming apparatus and reads an image printed on a sheet of paper. [Background technology]

[0002] The printing machine market is expanding in the commercial and industrial printing fields. Printing methods used by such machines include electrophotography, which is also expanding into the offset printing market, and inkjet, which has succeeded in cultivating a wide range of markets with its large format, low initial cost, and ultra-high speed.

[0003] Inkjet printers include, for example, line head type recording devices in which a recording head fixed to the main body ejects droplets in conjunction with the transported paper to print an image on the paper. When a line head type recording device is used in commercial printing or industrial printing fields that require high image quality, an image reading device is provided downstream of the recording head in the paper transport direction. The image reading device reads the image printed on the paper. The results of reading by the image reading device are used to detect ink ejection defects by the recording head, and to adjust color misregistration, uneven image density, and geometric characteristics of the image to be printed. Here, the geometric characteristics of the image include the shape of the image, the printing position, etc.

[0004] Printing machines in the commercial and industrial printing fields are required to have a long product life and high operating rate, so the image reading device spends a long time reading images to make various adjustments. In particular, when adjusting the geometric characteristics of an image printed on paper, the image reading device needs to read all of the paper in order to make the geometric characteristics of the image follow the deformation of the paper in real time.

[0005] The light source of an image reading device changes over time when it is turned on for a long time, and is the part with the shortest lifespan of all the parts in the image reading device. Furthermore, turning on the light source for a long time continuously causes the image reading device to heat up, which affects the image reading characteristics. For this reason, the light source of the image reading device is required to have a long lifespan and to suppress the temperature rise. Patent Document 1 discloses a technology that aims to extend the lifespan of the light source by turning on the light source only when reading an area including an image printed on paper. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-111900 Summary of the Invention [Problem to be solved by the invention]

[0007] The image reading device reads the shape of the paper so that the geometric characteristics of the image can follow the deformation of the paper in real time. In this case, it is sufficient for the image reading device to read the paper so that the length of the paper and the coordinates of the vertices of the four corners can be known. However, in Patent Document 1, the control of the light source lighting depends on the image printed on the paper. In other words, the light source is turned on only while the image printed on the paper passes the reading position. Also, in Patent Document 1, when reading the shape of the paper, the light source is always turned on so as to read the entire paper, regardless of the image. Therefore, the light source is not appropriately controlled to light up when reading the shape of the paper, which leads to a shortened life of the light source.

[0008] SUMMARY OF THE PRESENT DISCLOSURE In view of the above problems, a primary object of the present invention is to provide an image reading device that appropriately controls the lighting of a light source and suppresses temperature rise during reading processing for various adjustments. [Means for solving the problem]

[0009] The image reading device of the present invention is characterized in that it has an light-emitting means for irradiating light onto paper being transported, and a light-receiving means for receiving light reflected by the paper from the light-emitting means, and is equipped with a reading means for reading the paper based on the reflected light received by the light-receiving means, and a control means for turning on the light-emitting means only when reading the leading and trailing ends of the paper and the background areas surrounding them in the transport direction of the paper. Effect of the Invention

[0010] According to the present invention, it is possible to appropriately control the lighting of the light source during the reading process for various adjustments, and to suppress the rise in temperature due to the light emission of the light source. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram illustrating the configuration of an image reading device. [Diagram 2] FIG. [Diagram 3] FIG. 4 is an explanatory diagram of a first lighting control mode. [Figure 4] FIG. 4 is an explanatory diagram of a second lighting control mode. [Diagram 5] 4 is a flowchart showing an image reading process. [Figure 6] FIG. 11 is an explanatory diagram of a modified example of the first lighting control mode. [Figure 7] 4 is a flowchart showing an image reading process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[0013] FIG. 1 is a diagram showing the configuration of an image reading device. This image reading device 10 is provided inside an image forming device (not shown). The image reading device 10 reads paper S that is transported by a print belt 111 after an image is printed by the image forming device. The results of reading by the image reading device 10 are fed back to the image forming device and are used to adjust color shifts, uneven image density, and geometric characteristics of the image produced by the image forming device. For example, an electrophotographic method or an inkjet method is used as a printing method for the image forming device. Note that when the image forming device is an inkjet type, the results of reading by the image reading device 10 are also used to detect defective ink ejection by the recording head.

[0014] The image reading device 10 includes a box-shaped housing 100. The housing 100 incorporates a reading unit 101 that reads paper S, a reading glass 107, a shading reference plate 108, a motor 109, a photosensor 110, and a control unit 20. The reading unit 101 includes light sources 102a and 102b, reflecting mirrors 103a, 103b, 103c, 103d, and 103e, an imaging lens 104, a light receiving unit 105, and a sensor board 106.

[0015] The light sources 102a and 102b are light-emitting units that irradiate light onto the paper S. The light sources 102a and 102b each include a light-emitting element row configured by arranging a plurality of light-emitting elements, such as LEDs (Light Emitting Diodes), in a line. The light-receiving unit 105 receives the light irradiated from the light sources 102a and 102b and reflected by the paper S. The reflecting mirrors 103a to 103e are an optical system that guides the light reflected by the paper S to the imaging lens 104. The imaging lens 104 forms an image of the reflected light guided by the reflecting mirrors 103a to 103e on the light-receiving surface of the light-receiving unit 105.

[0016] The light receiving unit 105 outputs an analog electrical signal (hereinafter simply referred to as "analog signal") corresponding to the reflected light received on the light receiving surface. The analog signal represents the result of reading the paper S. The light receiving unit 105 includes a light receiving element row in which a plurality of photoelectric conversion elements, such as CCD (Charge Coupled Device) sensors, are arranged in the same direction as the light emitting element row. The light receiving unit 105 is mounted on a sensor board 106. The sensor board 106 is connected to the control unit 20, and transmits the analog signal output from the light receiving unit 105 to the control unit 20. The configuration of the control unit 20 will be described later.

[0017] The reading unit 101 reads an image in the main scanning direction, which is the direction in which the rows of light emitting elements of the light sources 102a and 102b and the row of light receiving elements of the light receiving unit 105 are aligned. The print belt 111 transports the paper S in a direction (transport direction SS) that intersects (here, perpendicular to) the main scanning direction. The transport direction SS is the sub-scanning direction. The reading unit 101 reads the image on the paper S transported in the transport direction SS, line by line, in the main scanning direction.

[0018] The reading glass 107 is a transparent member provided between the reading unit 101 and the print belt 111. The reading glass 107 prevents, for example, paper dust generated from the transported paper S from entering the inside of the reading unit 101 and affecting the reading result. Light output from the light sources 102a and 102b passes through the reading glass 107 and irradiates the paper S. Light reflected by the paper S passes through the reading glass 107 and is received by the light receiving unit 105. A shading reference plate 108 is provided on the reading glass 107 on the print belt 111 side. The shading reference plate 108 is, for example, a member whose side facing the reading unit 101 is white.

[0019] The shading reference plate 108 is read by the reading unit 101 during shading correction. The light receiving unit 105 has manufacturing variations for each photoelectric conversion element (each pixel). In addition, it is not easy to uniformize the light emitted from the light sources 102a and 102b in the main scanning direction. For this reason, even if an image is read from a paper S on which an image of uniform image density is printed, the digital values ​​of the image data, which are the reading results, will vary for each position in the main scanning direction. In order to suppress such variations, shading correction is performed.

[0020] Specifically, the reading glass 107 moves, and the shading reference plate 108 moves to a reading position (a position irradiated by the light sources 102a and 102b) by the reading unit 101. The reading unit 101 reads the shading reference plate 108 that has moved to the reading position. From the reading result of the shading reference plate 108, a correction value is calculated so that the reading result in the main scanning direction (e.g., luminance value) becomes uniform within a predetermined range. This correction value corrects the amount of irradiation by the light sources 102a and 102b, the sensitivity variation of the photoelectric conversion element of the light receiving unit 105, or the reading result of the image of the paper S, thereby correcting the manufacturing variation and the variation in the amount of light. The shading correction is performed in this manner. When the shading correction is completed, the reading glass 107 returns to the position shown in FIG. 1, and the shading reference plate 108 retreats from the reading position of the reading unit 101.

[0021] The movement of the reading glass 107 during shading correction is performed by a driving force output from the motor 109. In other words, the motor 109 serves as a driving source for moving the reading glass 107. The photosensor 110 detects whether the shading reference plate 108 is located at the reading position of the reading unit 101. For example, the photosensor 110 is turned on when the shading reference plate 108 is located at the reading position of the reading unit 101, and is turned off when the shading reference plate 108 is retracted from the reading position of the reading unit 101 to read the paper S.

[0022] A paper detection sensor 112 for detecting paper S transported from the image forming apparatus is provided upstream of the image reading device 10 in the transport direction SS. The paper detection sensor 112 is used to determine the presence or absence of paper S transported by the print belt 111. When the paper detection sensor 112 detects the paper S, the control unit 20 starts reading the paper S with the reading unit 101 and turns on the light sources 102a and 102b.

[0023] Fig. 2 is a configuration diagram of the control unit 20. The control unit 20 is electrically connected to the light sources 102a and 102b and the light receiving unit 105 of the reading unit 101. The control unit 20 is further electrically connected to a motor 109, a photosensor 110, and a paper detection sensor 112. In Fig. 2, the image reading device 10 is connected to an image forming device 30 such as a printer.

[0024] The control unit 20 is a computer system including a central processing unit (CPU) 201, a read only memory (ROM) 202, and a random access memory (RAM) 203. The CPU 201 uses the RAM 203 as a working area to execute a computer program stored in the ROM 202, thereby controlling the operation of the image reading device 10. In addition, the control unit 20 includes a lighting control unit 204 for controlling the operation of the light sources 102a and 102b, and a drive control unit 205 for controlling the operation of the motor 109. The control unit 20 includes an A / D conversion unit 206 and an image processing unit 207 for performing predetermined image processing on the reading result obtained from the light receiving unit 105. Such a control unit 20 may be realized by a discrete product or a one-chip semiconductor product. The one-chip semiconductor product is, for example, a micro-processing unit (MPU), an application specific integrated circuit (ASIC), a system-on-a-chip (SOC), or the like.

[0025] The lighting control unit 204 controls the turning on and off of the light sources 102a and 102b under the control of the CPU 201. When the paper S is detected as a result of the detection by the paper detection sensor 112, the CPU 201 causes the lighting control unit 204 to turn on the light sources 102a and 102b. When the paper S is no longer detected as a result of the detection by the paper detection sensor 112, the CPU 201 causes the lighting control unit 204 to turn off the light sources 102a and 102b.

[0026] In this embodiment, the lighting control unit 204 controls the light sources 102a and 102b in two lighting control modes, a first lighting control mode and a second lighting control mode. In the first lighting control mode, the lighting control unit 204 turns on the light sources 102a and 102b only when the leading edge and trailing edge of the paper S and the background around them are read in the transport direction SS. In the second lighting control mode, the lighting control unit 204 always turns on the light sources 102a and 102b while reading the entire surface of the paper S. Detailed operations of the first lighting control mode and the second lighting control mode will be described later.

[0027] The drive control unit 205, under the control of the CPU 201, transmits a drive signal to the motor 109 to move the reading glass 107 on which the shading reference plate 108 is provided. The CPU 201 transmits a control signal to the drive control unit 205 so that the shading reference plate 108 moves to the reading position of the reading unit 101 when the shading correction starts. The drive control unit 205 transmits a drive signal to the motor 109 based on this control signal to move the reading glass 107 from the position shown in FIG. 1. The CPU 201 transmits a control signal to the drive control unit 205 so that the shading reference plate 108 moves away from the reading position of the reading unit 101 when the shading correction ends. The drive control unit 205 transmits a drive signal to the motor 109 based on this control signal to return the reading glass 107 to the position shown in FIG. 1.

[0028] During shading correction, the CPU 201 controls the output of the drive control unit 205 based on the detection result of the photosensor 110. When starting shading correction, the CPU 201 stops the motor 109 through the drive control unit 205 when the photosensor 110 detects that the shading reference plate 108 has reached the reading position. When ending shading correction, the CPU 201 stops the motor 109 through the drive control unit 205 when the photosensor 110 detects that the shading reference plate 108 has retreated from the reading position.

[0029] Under the control of the CPU 201, the A / D conversion unit 206 receives an analog signal representing the result of reading the paper S from the light receiving unit 105, and converts the analog signal into a digital signal. The A / D conversion unit 206 transmits this digital signal to an image processing unit 207. Under the control of the CPU 201, the image processing unit 207 performs various types of image processing on the digital signal obtained from the A / D conversion unit 206, and generates image data representing the image read from the paper S. The image data is transmitted from the control unit 20 to the image forming apparatus 30, a personal computer, or the like.

[0030] The image forming device 30 includes an image analysis unit 301, a paper conveying unit 302, and an image forming unit 303. The image analysis unit 301 analyzes image data acquired from the control unit 20 of the image reading device 10, and calculates various correction values. The correction values ​​calculated by the image analysis unit 301 are fed back to the paper conveying unit 302 and the image forming unit 303, and are used to adjust color shift, uneven image density, geometric characteristics of the image, and the like. The paper conveying unit 302 conveys the paper on which the image is printed. The image forming unit 303 prints an image according to a print job on the paper. When printing the image, the image forming unit 303 adjusts color shift, uneven image density, geometric characteristics of the image, and the like based on the correction values. The paper on which the image is printed by the image forming device 30 is conveyed to the image reading device 10, and is read by the reading unit 101.

[0031] (Lighting control mode) 3 is an explanatory diagram of the first lighting control mode. In the printing presses in the commercial printing field and the industrial printing field, among various adjustments performed using the image reading device 10, there is a type of adjustment that does not require reading the entire paper S. For example, in the geometric adjustment that adjusts the geometric characteristics of the image printed by the image forming device 30, the skew of the image, the deviation of the image in the conveying direction SS, the deviation of the image in the direction perpendicular to the conveying direction SS, the main scanning magnification, the sub-scanning magnification, etc. are adjusted in real time during printing. Such geometric adjustment is possible if the length of the paper S and the coordinates of the four corners can be detected. In other words, it is not necessary to turn on the light sources 102a and 102b in the middle of the paper S except for the leading and trailing ends in the conveying direction SS.

[0032] The first lighting control mode is a lighting control mode that is set when it is not necessary to read the entire sheet S with the light sources 102a and 102b turned on. In the first lighting control mode, the light sources 102a and 102b are turned on only when reading the leading edge portion of the sheet S in the transport direction SS and its background portion, and the trailing edge portion of the sheet S in the transport direction SS and its background portion. The light sources 102a and 102b are turned off in the middle portion of the sheet S and in the middle portion between sheets S. This reduces the lighting time of the light sources 102a and 102b, and suppresses the rise in temperature of the image reading device 10 caused by the light sources 102a and 102b. This makes it possible to extend the life of the light sources 102a and 102b.

[0033] The leading and trailing edges of the paper S can be detected if a predetermined range is read so that the coordinates of the four corners of the paper S can be calculated by image processing. To calculate the coordinates of the four corners of the paper S, the edges of the paper S must be detected, and therefore the background areas around each of the leading and trailing edges of the paper S must also be read. The range that needs to be read at the leading and trailing edges of the paper S is constant regardless of the paper size. For example, the period during which the light sources 102a and 102b are turned off can be expressed by the following formula. (Light off section) = (paper length) - (leading edge reading range) - (rear edge reading range)

[0034] The paper length is the size from the leading edge to the trailing edge of the paper S. The leading edge reading range and the trailing edge reading range are the ranges that need to be read at the leading edge and trailing edge of the paper S. The ranges that need to be read at the leading edge and trailing edge of the paper S are, for example, about 10 mm inward from each of the leading edge and trailing edge of the paper S, taking into account transport variations of the paper S. The off intervals of the light sources 102a and 102b when the paper sizes are A3 and A5 are expressed by the following formula. For A3 size Light-off section = 420 [mm] - 10 [mm] - 10 [mm] =400[mm](95% of paper length) For A5 size Light-off section = 210 [mm] - 10 [mm] - 10 [mm] =190[mm](90% of paper length)

[0035] Thus, the larger the paper size, the longer the time that the light sources 102a and 102b are off, and the greater the effect of suppressing temperature rise and extending the life span. Also, real-time geometric adjustment during printing needs to be performed by reading all of the paper S in order to follow differences in paper cutting errors and shrinkage amounts. In other words, image reading for real-time geometric adjustment during printing accounts for a very high proportion of the total reading time of the image reading device 10. Therefore, by controlling image reading for real-time geometric adjustment during printing using the first lighting control mode, the effect of suppressing temperature rise and extending the life span of the light sources 102a and 102b is greater.

[0036] The timing at which light sources 102a and 102b turn on and off when reading paper S is constant regardless of the lighting control mode. The timing at which the light sources turn on when reading paper S is before (for example, about 10 mm before) the leading edge of paper S passes the reading position. The timing at which the light sources turn off is after (for example, about 10 mm after) the trailing edge of paper S passes the reading position. The image read before the leading edge of paper S passes the reading position is an image of the background part around the leading edge. The image read after the trailing edge of paper S passes the reading position is an image of the background part around the trailing edge.

[0037] 4 is an explanatory diagram of the second lighting control mode. In printing machines in the commercial printing field and the industrial printing field, among various adjustments performed using the image reading device 10, there is a type of adjustment that requires reading the entire paper S. For example, in image density unevenness adjustment that adjusts the image density unevenness of an image printed by the image forming device 30, an adjustment image is printed on the entire paper S, so it is necessary to read the entire paper S.

[0038] In the second lighting control mode, it is necessary to read the entire sheet S. For this reason, the light sources 102a and 102b are always on while the sheet S passes the reading position. This allows the entire adjustment image for adjusting image density unevenness to be read, making it possible to appropriately adjust image density unevenness. The timing of turning on and off the light sources 102a and 102b when reading the sheet S is the same as in the first lighting control mode.

[0039] The frequency of reading the adjustment image for adjusting image density unevenness is low. While real-time geometric adjustment during printing requires reading all of the paper S, the adjustment image for image density unevenness only needs to be read once every several hundred sheets. Therefore, in the case of adjusting image density unevenness, even if the entire paper S is read with the light sources 102a and 102b turned on, the impact on the temperature rise and shortening of the lifespan of the light sources 102a and 102b is small.

[0040] 5 is a flowchart showing an image reading process including a lighting control process for the light sources 102a and 102b. This process is started after the image forming apparatus 30 starts printing an image on the paper S.

[0041] The control unit 20 waits until an instruction to start image reading is given (S501: N). The instruction to start image reading is given, for example, by a command signal sent by the main control unit of the image forming apparatus 30. When an instruction to start image reading is given (S501: Y), the control unit 20 judges whether the lighting control mode is the first lighting control mode or not (S502). The lighting control mode is judged, for example, according to the type of adjustment performed using the image reading apparatus 10. For example, the control unit 20 judges that the lighting control mode is the first lighting control mode if the image reading is for geometric adjustment, and judges that the lighting control mode is the second lighting control mode if the image reading is for image density unevenness adjustment.

[0042] If the first lighting control mode is selected (S502: Y), the control unit 20 waits until the leading edge of the conveyed paper S approaches the image reading position (S503: N). The control unit 20 uses the paper detection sensor 112 to detect the leading edge of the paper S approaching the image reading position.

[0043] When the leading edge of the paper S approaches the reading position (S503: Y), the control unit 20 turns on the light sources 102a and 102b (S504). The control unit 20 causes the reading unit 101 to read an image of the leading edge of the paper S and its background (S505). When reading of the leading edge and its background is completed, the control unit 20 turns off the light sources 102a and 102b (S506). Thereafter, the control unit 20 causes the reading unit 101 to read an image of the middle portion of the paper S (S507). Note that in order to detect the paper length, it is necessary to read an image of the middle portion of the paper S (excluding the leading edge and trailing edge) even when the light sources 102a and 102b are turned off.

[0044] The control unit 20 waits until the rear end of the conveyed paper S approaches the image reading position (S508: N). The approach of the rear end of the paper S to the reading position is determined based on, for example, the elapsed time since the front end of the paper S was detected, the conveying speed of the paper S, and the paper size set in advance. The approach of the rear end of the paper S to the reading position can also be determined by the change in the detection result of the paper detection sensor 112 from a state in which the paper S is detected to a state in which the paper S is no longer detected. When the rear end of the paper S approaches the reading position (S508: Y), the control unit 20 turns on the light sources 102a and 102b (S509). The control unit 20 causes the reading unit 101 to read the image of the rear end of the paper S and its background part (S510). When a predetermined time has passed since the reading of the image of the rear end and its background part is completed, the control unit 20 turns off the light sources 102a and 102b (S511).

[0045] The control unit 20 determines whether or not there is a subsequent sheet (S512). If there is a subsequent sheet (S512: Y), the control unit 20 returns to the process of S503 and reads the subsequent sheet S. If there is no subsequent sheet (S512: N), the control unit 20 ends the image reading process.

[0046] When the lighting control mode is the second lighting control mode (S502: N), similarly to the process of S503, the control unit 20 waits until the leading edge of the conveyed paper S approaches the image reading position (S513: N). When the leading edge of the paper S approaches the reading position (S513: Y), the control unit 20 turns on the light sources 102a and 102b (S514). The control unit 20 causes the reading unit 101 to read the entire image of the paper S (S515). When the reading is completed, the control unit 20 turns off the light sources 102a and 102b (S516). The control unit 20 determines whether or not there is a subsequent paper (S517). When there is a subsequent paper (S517: Y), the control unit 20 returns to the process of S513 and reads the subsequent paper S. When there is no subsequent paper (S517: N), the control unit 20 ends the image reading process.

[0047] By the above-mentioned process, the light sources 102a and 102b are appropriately controlled to be turned on during image reading for various adjustments. This makes it possible to suppress the temperature rise of the light sources 102a and 102b of the image reading device 10 and to extend the life of the light sources 102a and 102b.

[0048] Fig. 6 is an explanatory diagram of a modified example of the lighting control of the light sources 102a and 102b in the first lighting control mode. This differs from the lighting control of the light sources 102a and 102b in the first lighting control mode shown in Fig. 3 in that the light sources 102a and 102b are not turned off but continue to be lit even between multiple sheets of paper S that are transported continuously.

[0049] Printing machines in the commercial printing and industrial printing fields have high printing speeds and the spacing between multiple sheets of paper S that are transported in succession is narrow. For this reason, when turning on and off the light sources 102a and 102b between sheets of paper as described in FIG. 3, there is a possibility that the processing will not be completed in time due to the narrow spacing between sheets. In such a case, it is appropriate to control the lighting of the light sources 102a and 102b as shown in FIG. 6. In FIG. 6, the light sources 102a and 102b are not turned off between sheets of paper but remain on.

[0050] 7 is a flowchart showing an image reading process including a lighting control process of a modified example of the light sources 102a and 102b. This process is started after the image forming apparatus 30 starts printing an image on the paper S.

[0051] The processing of S701 to S710 is the same as the processing of S501 to S510 in Fig. 5, and therefore the description will be omitted. After the processing of S710, the control unit 20 determines whether or not there is a succeeding sheet of paper (S711) without turning off the light sources 102a and 102b. If there is a succeeding sheet of paper (S711: Y), the control unit 20 returns to the processing of S705 and reads the succeeding sheet of paper S. If there is no succeeding sheet of paper (S711: N), the control unit 20 turns off the light sources 102a and 102b (S716) and ends the image reading processing.

[0052] When the lighting control mode is the second lighting control mode (S702: N), the control unit 20 waits until the leading edge of the conveyed paper S approaches the image reading position (S712: N). When the leading edge of the paper S approaches the reading position (S712: Y), the control unit 20 turns on the light sources 102a and 102b (S713). The control unit 20 causes the reading unit 101 to read the entire image of the paper S (S714). When the reading is completed, the control unit 20 determines whether or not there is a subsequent paper without turning off the light sources 102a and 102b (S715). When there is a subsequent paper (S715: Y), the control unit 20 returns to the process of S712 and reads the subsequent paper S. If there is no subsequent paper (S714: N), the control unit 20 turns off the light sources 102a and 102b (S716) and ends the image reading process.

[0053] By the above-mentioned process, even if the distance between the sheets is so narrow that the light sources 102a and 102b cannot be controlled in time, the light sources 102a and 102b are appropriately controlled to light during image reading for various adjustments. This makes it possible to suppress the temperature rise of the light sources 102a and 102b of the image reading device 10 and to extend the life of the light sources 102a and 102b.

Claims

1. a light emitting means for irradiating light onto the paper being conveyed, and a light receiving means for receiving light reflected by the paper from the light emitting means, and a reading means for reading the paper based on the reflected light received by the light receiving means; a control means for setting an area corresponding to the leading edge of the paper in the paper transport direction as a first area, an area corresponding to the trailing edge of the paper as a second area, and an area between the first area and the second area as a third area, and for turning on the light emitting means in the first area to cause the reading means to read the first area, for providing a period in which the light emitting means is turned off in the third area, and for turning on the light emitting means in the second area to cause the reading means to read the second area, Image reading device.

2. The first area includes the leading edge of the paper and a background area around it, The second area includes the rear end of the paper and a background area therearound.

2. The image reading device according to claim 1.

3. the control means controls the reading means in a first mode in which the light emitting means is turned on when reading the first area and the second area and is turned off when reading the third area, and in a second mode in which the light emitting means is turned on while reading the first area, the second area, and the third area.

2. The image reading device according to claim 1.

4. The control means, in the first mode, causes the reading means to read the paper even in the third area where the light emitting means is not lit.

4. The image reading device according to claim 3.

5. The control unit determines whether the mode is the first mode or the second mode depending on the type of adjustment performed using the reading unit.

4. The image reading device according to claim 3.

6. a detection unit that detects the paper on the upstream side of the reading unit in the transport direction; The control means turns on the light emitting means when the detection means detects the paper, regardless of the mode.

4. The image reading device according to claim 3.

7. the control means turns off the light emitting means when reading of the second area is completed in the first mode.

4. The image reading device according to claim 3.

8. the control means does not turn off the light emitting means even when reading of the second area is completed when a plurality of sheets of paper are continuously conveyed in the first mode.

4. The image reading device according to claim 3.

9. an image forming means for printing an image on a sheet; an image reading means for reading the paper; The image reading means a light emitting means for irradiating light onto the paper being conveyed, and a light receiving means for receiving light reflected by the paper from the light emitting means, and a reading means for reading the paper based on the reflected light received by the light receiving means; and a control means for controlling the reading means in a first mode in which the light emitting means is turned on when reading a first region corresponding to the leading edge of the paper in the paper transport direction and a second region corresponding to the trailing edge of the paper, and a second mode in which the light emitting means is turned on while reading the entire surface of the paper. Image forming device.

10. further comprising an image analysis unit that analyzes the results of reading by the image reading unit and calculates a correction value for adjusting the image printed by the image forming unit; The control unit determines whether to control the reading unit in the first mode or the second mode depending on the type of adjustment.

10. The image forming apparatus according to claim 9.

11. the control means controls the lighting of the light emitting means in the first mode when adjusting the geometric characteristics of the image printed on the paper by the image forming means.

10. The image forming apparatus according to claim 9.

12. the control means controls the lighting of the light emitting means in the second mode when adjusting unevenness in image density of the image printed on the paper by the image forming means.

10. The image forming apparatus according to claim 9.

Images