Image reading device and image forming apparatus including the same

Abstract

To provide an image reading device that can execute light source lighting control of front face and rear face reading modules at a timing when the modules are not affected by disturbance light, and an image forming apparatus including the same.SOLUTION: An image reading device 6 comprises a contact glass 25, a document conveying device 27, a first reading module 50, a second reading module 51, a first white reference member 55, a second white reference member 57, and a control unit. The first reading module 50 reads an image of a stationary document placed on the contact glass 25 and an image of a front face of a conveyance document that is conveyed by the document conveying device to an automatic reading position. The second reading module 51 is arranged inside the document conveying device, and reads an image of a rear face of the conveyance document. When executing double-sided reading processing on the conveyance document, the control unit executes, after the double-sided reading processing is requested, offset adjustment and gain adjustment of the second reading module 51 and acquisition of rear face black reference data and front face white reference data.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an image reading device that scans and reads a document, which is used in a digital copying machine, an image scanner, etc., and an image forming apparatus including the same.

Background Art

[0002] Conventionally, among image reading devices mounted on multi-functional devices using an electrophotographic process, there are those equipped with a document conveyance device (Automatic Document Feeder) that sequentially feeds a sheet-like document onto a document placement table (contact glass) to read it, and discharges it from the document placement table after reading. In such an image reading device, there are two types of reading methods: a sheet-through method in which the document is automatically conveyed and read by the document conveyance device with the reading module fixed at the image reading position, and a document fixing method in which the document presser is opened and closed each time a document is read, and the reading module is scanned and moved to read the document placed on the document placement table one by one.

[0003] In recent years, in the above sheet-through method, a double-sided simultaneous reading method in which the front and back surfaces of a double-sided document are simultaneously read using different reading modules in one document conveyance operation by the document conveyance device has become mainstream. The reading module for reading the back surface of the double-sided document is arranged on the document conveyance device side. Also, in the image reading device, there are various processes necessary for initial setting and adjustment of the reading module, etc. One of these processes is a white reference data acquisition process and a black reference data acquisition process for acquiring the light amount data of the reflected light from the white reference plate arranged opposite to the reading module as white reference data and black reference data when the light source mounted on the reading module is turned on and off.

[0004] Patent Document 1 discloses an image reading apparatus including a first reading unit for surface reading and a second reading unit for back surface reading, which are arranged to face each other via a document conveyance path, and a first white reference member and a second white reference member arranged to face each reading unit. In the image reading apparatus of Patent Document 1, the downstream end of the first white reference member is adjusted to be upstream of the second irradiation range irradiated with the reflected light emitted from the second light source of the second reading unit and regularly reflected by the second white reference member. Further, the upstream end of the second white reference member is adjusted to be equal to the downstream end of the first irradiation range irradiated with the reflected light emitted from the first light source of the first reading unit and regularly reflected by the first white reference member.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the configuration of Patent Document 1, the first white reference member and the second white reference member are arranged at positions where the irradiation light from one reading module does not become stray light of the other reading module. However, if the document conveyance device is in an open state separated from the document placement table, there is a possibility that stray light may enter the reading module. Further, it is necessary to consider the possibility that the white reference member of the reading module is not arranged at the reading position facing the reading module.

[0007] Particularly, when the document conveyance device is not provided with an open / close detection function for cost reduction, there is a possibility that offset adjustment, gain adjustment, acquisition of black-and-white reference data, etc. may be executed in a state where stray light enters the reading module or in a state where the white reference member, which is the object to be read, is not arranged at the reading position. As a result, there are problems such that the document conveyance device stops in an abnormal detection state or a normal image reading operation cannot be performed.

[0008] In view of the above problems, an object of the present invention is to provide an image reading apparatus capable of acquiring appropriate double-sided reading images by performing light source lighting control of the front surface reading module and the back surface reading module at a timing not affected by external light, and an image forming apparatus including the same.

Means for Solving the Problems

[0009] A first configuration of the present invention for achieving the above object is an image reading apparatus including a contact glass, a document conveying device, a first reading module, a second reading module, a first white reference member, a second white reference member, and a control unit. The contact glass has a document placed thereon. The document conveying device is provided on the upper surface of the contact glass so as to be openable and closable, and conveys the document to the automatic reading position of the contact glass. The first reading module is disposed below the contact glass so as to be reciprocally movable in the sub-scanning direction, and is capable of reading an image on the surface side of a fixed document placed on the contact glass and a conveyed document conveyed to the automatic reading position by the document conveying device. The second reading module is disposed in the document conveying device and is capable of reading an image on the back side of the conveyed document. The first white reference member is disposed opposite to the first reading module at a position different from the automatic reading position. The second white reference member is disposed opposite to the second reading module. The control unit controls the first reading module and the second reading module. The first reading module includes a first light source and a first sensor that reads the reflected light of the light irradiated from the first light source to the conveyed document as image light. The second reading module includes a second light source and a second sensor that reads the reflected light of the light irradiated from the second light source to the conveyed document as image light. When the control unit executes a double-sided reading process of reading images on the front surface side and the back surface side of the conveyed document at once as a conveyance reading process for reading an image of the conveyed document, after the double-sided reading process is requested, the control unit executes offset adjustment, gain adjustment, acquisition of black reference data for the back surface, and acquisition of white reference data for the back surface of the second reading module.

Effects of the Invention

[0010] According to the first configuration of the present invention, when performing double-sided reading processing, before turning on the light source of the first reading module to obtain surface white reference data, offset adjustment, gain adjustment of the second reading module, and acquisition of black reference data for the back side and white reference data for the back side are executed. If it is immediately after double-sided reading processing is requested, the document conveyance device is in a closed state, and the second reading module can appropriately read the second white reference member without being affected by external light. Therefore, it is not necessary to provide an open / close detection function for the document conveyance device, and the number of parts of the document conveyance device can be reduced and the cost can be lowered.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an image forming apparatus 100 including an image reading unit 6 of the present invention. In FIG. 1, in the image forming apparatus 100 (here, a digital multi-functional peripheral is shown as an example), when performing a copying operation, the image reading unit 6 described later reads the image data of the document and converts it into an image signal. On the other hand, in the image forming unit 3 within the multi-functional peripheral main body 2, the photosensitive drum 5 that rotates in the clockwise direction in FIG. 1 is uniformly charged by the charging unit 4. Then, an electrostatic latent image based on the document image data read by the image reading unit 6 is formed on the photosensitive drum 5 by a laser beam from an exposure unit (such as a laser scanning unit) 7. The developer (hereinafter referred to as toner) is attached to the formed electrostatic latent image by the developing unit 8 to form a toner image. The supply of toner to the developing unit 8 is performed from the toner container 9.

[0013] Toward the photosensitive drum 5 on which the toner image is formed as described above, the paper is conveyed from the paper feeding mechanism 10 to the image forming unit 3 via the paper conveyance path 11 and the registration roller pair 12. The conveyed paper passes through the nip portion of the photosensitive drum 5 and the transfer roller 13 (image transfer portion), and the toner image on the surface of the photosensitive drum 5 is transferred. Then, the paper on which the toner image is transferred is separated from the photosensitive drum 5 and conveyed to the fixing unit 14 having the fixing roller pair 14a, and the toner image is fixed. The paper that has passed through the fixing unit 14 is conveyed to the paper conveyance path 15 that branches in a plurality of directions. The conveyance direction of the paper is sorted by the path switching mechanisms 21 and 22 having a plurality of path switching guides provided at the branch point of the paper conveyance path 15, and then (either as it is or after being sent to the reverse conveyance path 16 and double-sided copied), it is discharged to the paper discharge portion composed of the first discharge tray 17a and the second discharge tray 17b.

[0014] Also, although not shown, a charge removing device for removing residual charge on the surface of the photoreceptor drum 5 is provided on the downstream side of the cleaning device 18 with respect to the rotation direction of the photoreceptor drum 5. Further, the paper feeding mechanism 10 is detachably attached to the multifunction machine main body 2 and includes a plurality of paper feeding cassettes 10a and 10b for storing paper and a stack bypass (manual feed tray) 10c provided above them, and these are connected to the image forming unit 3 including the photoreceptor drum 5 and the developing unit 8 etc. by a paper conveyance path 11.

[0015] An image reading unit 6 is arranged at the upper part of the multifunction machine main body 2, and a document conveyance device 27 is attached to the upper surface of the multifunction machine main body 2. The lower surface of the document conveyance device 27 also serves as a platen (document presser) that presses and holds the document placed on the contact glass 25 (see FIG. 2) of the image reading unit 6 when the document conveyance device 27 is in a closed state.

[0016] An operation unit 80 is provided on the front surface of the image reading unit 6. The operation unit 80 is provided with a liquid crystal display unit and LEDs, and is configured to indicate the state of the image forming apparatus 100, display the image forming status and the number of printed copies. In addition, the operation unit 80 is provided with a start button for the user to instruct to start image formation, a stop / clear button used when aborting image formation, a reset button used when setting various settings of the image forming apparatus 100 to the default state, etc.

[0017] Specifically, the paper conveyance path 15 first branches into two branches on the downstream side of the fixing roller pair 14a. One path (the path that branches to the right direction in FIG. 1) is configured to communicate with the first discharge tray 17a. Then, the other path (the path that branches to the left direction in FIG. 1) branches into two branches via the conveyance roller pair 19. One path (the path that branches to the left direction in FIG. 1) is configured to communicate with the second discharge tray 17b. On the contrary, the other path (the path that branches downward in FIG. 1) is configured to communicate with the reverse conveyance path 16.

[0018] Furthermore, inside the multi-function device main body 2, a control unit (CPU) 90 that controls operations of an image forming unit 3, an image reading unit 6, a document conveying device 27, etc. is arranged.

[0019] FIG. 2 is a side cross-sectional view showing the internal structure of the image reading unit 6 according to an embodiment of the present invention provided with the document conveying device 27. On the upper surface of the image reading unit 6, a contact glass 25 composed of an automatic reading glass 25a and a hand-placed document glass 25b is arranged.

[0020] Inside the image reading unit 6, a surface reading module 50 is arranged. The surface reading module 50 reads a document image placed on the hand-placed document glass 25b while moving in the sub-scanning direction (the left-right direction in FIG. 2). Further, the surface reading module 50 reads an image on the front surface side (lower surface side) of a document conveyed by the document conveying device 27 while stopped directly below the automatic reading glass 25a.

[0021] Between the automatic reading glass 25a and the hand-placed document glass 25b, a conveying guide 54 that scoops up the leading edge of a document conveyed by the document conveying device 27 is arranged. Below the conveying guide 54, a surface white reference plate 55 for shading correction of the surface reading module 50 is arranged.

[0022] The cover member 31 of the document conveying device 27 is supported so as to be openable and closable with the device side surface side (the left side in FIG. 2) as a fulcrum with respect to a frame (not shown) of the document conveying device 27. Inside the cover member 31, a document conveying path d from a document feeding tray 29 to a document discharging tray 32 is formed. Along the document conveying path d, document conveying members including a pickup roller 33, a paper feeding belt 34, a separating roller 35, a registration roller pair 36, a conveying roller pair 37, a discharging roller pair 43, etc., and a back surface reading module 51 that reads an image on the back surface side of a document are provided.

[0023] The original document conveyance path d is curved so as to reverse between the resist roller pair 36 and the automatic reading glass 25a. Also, a plurality of paper detection sensors (not shown), including a paper feed sensor and a discharge sensor for detecting the presence or passage of the original document, are provided at appropriate positions in the original document conveyance path d. Further, a backside white reference plate 57 for shading correction of the backside reading module 51 is disposed at a position facing the backside reading module 51 across the original document conveyance path d.

[0024] The paper feed belt 34 is wound around a driving roller 44a and a driven roller 44b, and a separation roller 35 contacts from below with a predetermined pressure. A torque limiter is built in the separation roller 35, and it is configured to rotate drivenly with the paper feed belt 34 only when the rotational load exceeds a predetermined torque.

[0025] An open / close detection sensor 58 for detecting the opening and closing of the cover member 31 is disposed inside the cover member 31. The open / close detection sensor 58 is a PI (photointerrupter) sensor including a detection unit having a light emitting unit and a light receiving unit. As shown in FIG. 2, when the cover member 31 is in the closed position, the open / close detection sensor 60 is shielded from light by a light shielding plate (not shown) provided on the cover member 31 side, and the light receiving signal level of the detection unit is in the LOW state. When the cover member 31 rotates in the opening direction (upward) from the state of FIG. 2, the light shielding plate retracts upward from the detection unit of the open / close detection sensor 58, and the light receiving signal level of the detection unit becomes the HIGH state. The opening and closing of the cover member 31 are detected by transmitting the light receiving signal of the open / close detection sensor 60 to a control unit 90 (see FIG. 6).

[0026] Next, the sheet-through type document reading operation using the document feeder 27 will be described. In the sheet-through type, with the document feeder 27 in a closed state in contact with the contact glass 25, a plurality of documents are set on the document feed tray 29 with the image side facing up. Then, when the copy start button on the operation unit 80 (see FIG. 1) of the image forming apparatus 100 is turned on, a lift plate (not shown) raised by a lifting mechanism (not shown) pushes up the pickup roller 33 through the document. As a result, the weight of the frame (not shown) including the pickup roller 33 is applied to the lift plate, and the upper surface of the document is pressed against the pickup roller 33 with a predetermined pressure (paper feed pressure).

[0027] Here, the pickup roller 33, the driving roller 44a, the driven roller 44b, and the paper feed belt 34 are arranged on a frame (not shown). The pickup roller 33 is connected to the driving roller 44a by a gear (not shown). When the driving roller 44a rotates by a roller driving motor (not shown), the paper feed belt 34 stretched between the driving roller 44a and the driven roller 44b is rotationally driven, and the pickup roller 33 is also rotationally driven.

[0028] The documents set on the document feed tray 29 are sent by the pickup roller 33 to the nip portion between the paper feed belt 34 and the separation roller 35, usually multiple sheets from the upper layer. Then, only the topmost one of the multiple documents is separated by the separation roller 35 and conveyed toward the registration roller pair 36. At this time, after the leading edge of the document is detected by the paper feed sensor and the document is conveyed by a predetermined distance, the rotational driving of the pickup roller 33 and the paper feed belt 34 is stopped by stopping the operation of the roller driving motor, and the primary paper feed is completed. The document fed in the primary paper feed stops at the nip portion of the registration roller pair 36 with a bend formed at its leading edge.

[0029] After a predetermined time has elapsed since the first paper feed ends, the second paper feed is started. That is, the registration roller pair 36 is rotationally driven by the operation of a second paper feed drive motor (not shown). The document is conveyed toward the document reading glass 25a by the registration roller pair 36 and the conveyance roller pair 37. The document conveyed to the document reading glass 25a is pressed against the document reading glass 25a from above by coming into contact with a document pressing member (not shown) disposed opposite to the document reading glass 25a. Then, the image on the front side (the document reading glass 25a side) of the document is read by the front surface reading module 50 through the document reading glass 25a.

[0030] Thereafter, the document that has passed through the document reading glass 25a is conveyed through the conveyance guide 54 toward the conveyance roller pair 37 and the discharge roller pair 43, and finally is discharged onto the document discharge tray 32 by the discharge roller pair 43. At that time, when the passage of the rear end of the document is detected by the discharge sensor, the completion of the image reading of one document is detected. Here, the discharge sensor has a counting function for counting the number of documents every time the conveyance of a document is completed. If the paper feed sensor detects a subsequent document, the conveyance of the second and subsequent documents continues in the same manner as described above.

[0031] Also, when reading a double-sided document, after reading the image on the back surface of the document with the back surface reading module 51 provided on the upstream side of the document reading glass 25a, the image on the front surface of the document is read with the front surface reading module 50.

[0032] FIG. 3 and FIG. 4 are enlarged views around the front surface reading module 50 and the front surface white reference plate 55 in FIG. 2, showing the states where the front surface reading module 50 is in the reference position (home position) and the automatic reading position, respectively. The front surface reading module 50 is a reading module of the CIS sensor (Contact Image Sensor) method.

[0033] As shown in FIG. 3, inside the surface reading module 50, there are a light source 70a, a condenser lens 71a composed of a plurality of lenses, and a CMOS (Complementary MOS) sensor 73a as a reading means. The CMOS sensor 73a is supported by a substrate 75a. After the light irradiated from the light source 70a is reflected by a document (not shown), it is condensed by the condenser lens 71 and guided to the CMOS sensor 73a. The surface reading module 50 is in contact with the back surface of the contact glass 25 via a slider 60.

[0034] Here, as a reading method of the surface reading module 50, an equal magnification optical system using a CMOS sensor 73 as an imaging device without using a mirror is exemplified. However, it is also possible to use a reduction optical system that uses a plurality of mirrors and optical lenses, uses a charge coupled device called a CCD (Charge Coupled Devices) as an imaging device, and forms a reduced image by an optical lens to read an image.

[0035] In the above configuration, when reading a document image in a document fixing method, first, the document conveying device 27 is opened, and a document (not shown) is placed face down on the document glass 25b for hand placement. Then, the document conveying device 27 is closed, and while irradiating the image surface of the document with the light from the light source 70a, the surface reading module 50 is moved at a predetermined speed from the scanner home side (the left side in FIG. 2) to the scanner return side (the right side in FIG. 2). As a result, the light reflected from the image surface becomes image light and is formed on the CMOS sensor 73a. The formed image light is pixelated by the CMOS sensor 73a and converted into an electrical signal corresponding to the density of each pixel, and the image is read.

[0036] On the one hand, when reading a document image in a sheet-through manner, the document conveyance device 27 is closed, and as shown in FIG. 4, the front surface reading module 50 is moved to the automatic reading position (directly below the automatic reading glass 25a). Then, the document is sequentially conveyed toward the automatic reading glass 25a by the document conveyance device 27, the front surface of the document passing through the automatic reading glass 25a is irradiated with light from the light source 70a, and the image light reflected from the image surface is imaged on the CMOS sensor 73a to read the image. In any reading method, the image signal read by the front surface reading module 50 is converted into a digital signal and then sent to the temporary storage unit 94 (see FIG. 6).

[0037] FIG. 5 is an enlarged view around the back surface reading module 51 in FIG. 2. The back surface reading module 51 is a reading module of the same CIS sensor (Contact Image Sensor) method as the front surface reading module 50. As shown in FIG. 5, inside the back surface reading module 51, a light source 70b, a condenser lens 71b composed of a plurality of lenses, and a CMOS (Complementary MOS) sensor 73b as a reading means are provided. The CMOS sensor 73b is supported by a substrate 75b.

[0038] The back surface of the document passing through the back surface reading module 51 is irradiated with light from the light source 70b, the reflected light (image light) reflected from the image surface is condensed again by the condenser lens 71b, and is imaged on the CMOS sensor 73b. The imaged image light is pixel-decomposed by the CMOS sensor 73b and converted into an electrical signal corresponding to the density of each pixel to read the image.

[0039] FIG. 6 is a block diagram showing an example of a control path used in the image forming apparatus 100 of the present embodiment. Since various controls of each part of the image forming apparatus 100 are performed when using the image forming apparatus 100, the control path of the entire image forming apparatus 100 becomes complicated. Therefore, here, the part necessary for the implementation of the present invention in the control path will be mainly described.

[0040] The operation unit 80 is provided with a liquid crystal display unit 81 and LEDs 82 indicating various states, which are configured to indicate the state of the image forming apparatus 100, display the image forming status and the number of printed sheets. Various settings of the image forming apparatus 100 are made from the printer driver of the personal computer.

[0041] In addition, the operation unit 80 is provided with a start button for the user to instruct to start image formation, a stop / clear button used when aborting image formation, a reset button used when setting various settings of the image forming apparatus 100 to the default state, and the like.

[0042] The module drive motor 83 reciprocates the surface reading module 50 in the sub-scanning direction (the left-right direction in FIG. 2) when reading the original image in the original fixing method. Further, the module drive motor 83 moves the surface reading module 50 to the automatic reading position when reading the original image in the sheet-through method. The module drive motor 83 is a stepping motor, and the control unit 90 can detect the position of the surface reading module 50 based on the number of drive pulses of the module drive motor 83.

[0043] The control unit 90 includes at least a CPU (Central Processing Unit) 91 as a central arithmetic processing unit, a ROM (Read Only Memory) 92 which is a read-only storage unit, a RAM (Random Access Memory) 93 which is a rewritable storage unit, a temporary storage unit 94 for temporarily storing image data and the like, a plurality (here, two) of I / Fs (interfaces) 96 for transmitting control signals to each device in the image forming apparatus 100 and receiving input signals from the operation unit 80, and a reading processing unit 97. Further, the control unit 90 can be arranged at an arbitrary location within the image forming apparatus 100.

[0044] In addition, the control unit 90 transmits control signals to each part and device in the image forming apparatus 100 from the CPU 91 through the I / F 96. Further, signals indicating the states thereof and input signals from each part and device are transmitted to the CPU 91 through the I / F 96. Examples of the parts and devices controlled by the control unit 90 include the image forming unit 3, the image reading unit 6, the document conveying device 27, the operation unit 80, and the like.

[0045] The ROM 92 stores control programs for the image forming apparatus 100, data such as numerical values necessary for control, and data that should not be changed during the use of the image forming apparatus 100. The RAM 93 stores necessary data generated during the control of the image forming apparatus 100 and data temporarily required for the control of the image forming apparatus 100. The temporary storage unit 94 receives an image signal input from an image input unit (not shown) that receives image data transmitted from the image reading unit 6 and is converted into a digital signal, and temporarily stores the image signal.

[0046] The reading processing unit 97 executes a reading process of the document fixing method (fixed reading process) for reading image data from a document placed on the platen glass 25b for hand-placed documents using the surface reading module 50. Further, the reading processing unit 97 executes a reading process of the sheet-through method (conveying reading process) for reading image data on the front and back sides of a document automatically conveyed by the document conveying device 27 using the surface reading module 50 and the back surface reading module 51.

[0047] By the way, at various timings such as when the power of the image forming apparatus 100 is turned on, when it resumes from the power saving state (sleep mode), when there is a predetermined temperature and humidity change, or when the image reading process is started, processes necessary for the initial setting and adjustment of the back surface reading module 51 and the surface reading module 50 are performed. The processes include black reference data acquisition process, white reference data acquisition process, offset adjustment, and gain adjustment.

[0048] The black reference data acquisition process acquires the output voltages (output levels) of the CMOS sensors 73a and 73b as light quantity data (black reference data) with the light sources 70a of the front surface reading module 50 or 70b of the back surface reading module 51 turned off.

[0049] The white reference data acquisition process turns on the light source 70a of the front surface reading module 50 or 70b of the back surface reading module 51, so that the light irradiated from the light source 70a or 70b is reflected by the front surface white reference plate 55 or the back surface white reference plate 57, condensed by the condenser lenses 71a or 71b, and guided to the CMOS sensors 73a or 73b. The output voltages (output levels) of the CMOS sensors 73a and 73b at this time are acquired as light quantity data (white reference data).

[0050] Offset adjustment adjusts the output voltages (output levels) of the CMOS sensors 73a and 73b to a constant voltage with the light sources 70a of the front surface reading module 50 or 70b of the back surface reading module 51 turned off. Gain adjustment adjusts the output voltages (output levels) of the CMOS sensors 73a and 73b to a constant voltage with the light sources 70a of the front surface reading module 50 or 70b of the back surface reading module 51 turned on.

[0051] In the image reading unit 6 of the present embodiment, the back surface reading module 51 is installed at a position facing the front surface reading module 50 in order to reduce the height of the image reading unit 6 (reduce the dimension in the height direction). Then, at the time of reading a document in the sheet-through method, the irradiation light from the light source 70a (or the light source 70b of the back surface reading module 51) of the front surface reading module 50 is arranged in a positional relationship so as not to become external disturbance light for the CMOS sensor 73b of the back surface side reading module 51 (or the CMOS sensor 73b of the back surface reading module 51).

[0052] However, when reading a document in the sheet-through method, the front reading module 50 moves from below the white reference plate 55 for the front surface to the automatic reading position with the light source 70a turned on. Therefore, there is a possibility that the irradiation light from the light source 70a may become stray light with respect to the CMOS sensor 73b of the back reading module 51.

[0053] Also, when the document conveyance device 27 does not have an open / closed detection function for detecting whether it is in a closed state in contact with the contact glass 25 or an open state separated from the contact glass 25, if the black reference data acquisition process is performed with the document conveyance device 27 in the open position, the CMOS sensor 73a or 73b may receive stray light and accurate black reference data may not be obtained.

[0054] Therefore, in the present embodiment, when double-sided reading is required in the sheet-through method document reading operation, before executing the white reference data acquisition process of the front reading module 50, offset adjustment, gain adjustment, and black and white reference data acquisition processes of the back reading module 51 are executed. Then, after the offset adjustment, gain adjustment, and acquisition of black and white reference data of the back reading module 51 are completed, the white reference data of the front reading module 50 is acquired.

[0055] FIG. 7 is a flowchart showing an example of document reading control in the sheet-through method in the image reading unit 6 of the present embodiment. With reference to FIGS. 1 to 6 as necessary, the lighting control of the light source 70a of the back reading module 51 and the light source 70b of the back reading module 51 in the sheet-through method will be described according to the steps in FIG. 7. It is assumed that in the initial state, the front reading module 50 is arranged at the reference position (home position) shown in FIG. 3. Also, it is assumed that the front reading module 50 has been subjected to offset adjustment and gain adjustment when the image forming apparatus 100 is powered on.

[0056] When sheet-through original reading is requested, the control unit 90 acquires surface black reference data (step S1). Specifically, the output level of the CMOS sensor 73a with the light source 70a of the surface reading module 50 turned off is acquired as the surface black reference data.

[0057] Next, the control unit 90 determines whether the requested original reading process is a duplex reading process (step S2). If it is a duplex reading process (Yes in step S2), the control unit 90 performs offset adjustment of the backside reading module 51 with the light source 70b of the backside reading module 51 turned off (step S3). Next, the control unit 90 turns on the light source 70b of the backside reading module 51. Then, gain adjustment of the backside reading module 51 is performed (step S4).

[0058] Subsequently, the control unit 90 turns off the light source 70b of the backside reading module 51. Then, backside black reference data is acquired (step S5). Specifically, the output level of the CMOS sensor 73b with the light source 70b of the backside reading module 51 turned off is acquired as the backside black reference data.

[0059] Note that if gain adjustment of the backside reading module 51 is performed after the backside black reference data is acquired, the output level of the CMOS sensor 73b with the light source 70b turned off may also change. Therefore, gain adjustment of the backside reading module 51 is performed before the backside black reference data is acquired. As a result, the number of times of turning the light source 70b on and off is increased, but more accurate backside black reference data can be acquired.

[0060] Subsequently, the control unit 90 turns on the light source 70b of the back surface reading module 51. Then, it acquires the back surface white reference data (step S6). Specifically, it acquires the output level of the CMOS sensor 73b with the light source 70b of the back surface reading module 51 turned on as the back surface white reference data. In this embodiment, while either the back surface reading module 51 or the back surface white reference plate 57 is oscillated in a direction orthogonal to the conveyance direction by an oscillation mechanism (not shown), the back surface white reference data is acquired multiple times.

[0061] Next, the control unit 90 determines whether or not the acquisition of the back surface white reference data has been completed (step S7). If the acquisition of the back surface white reference data has been completed (Yes in step S7), the control unit 90 turns on the light source 70a of the front surface reading module 50. Then, it acquires the front surface white reference data (step S8). Specifically, with the front surface reading module 50 arranged at the reference position (directly below the front surface white reference plate 55), the light source 70a is turned on and the output level of the CMOS sensor 73a is acquired as the front surface white reference data.

[0062] On the other hand, if the required original reading is single-sided reading (No in step S2), after acquiring the front surface black reference data (step S1), the control unit 90 turns on the light source 70a of the front surface reading module 50 to acquire the front surface white reference data (steps S8, S9) without performing the offset adjustment of the back surface reading module 51, the acquisition of the back surface black reference data, the gain adjustment, and the acquisition of the back surface white reference data (steps S3 to S7).

[0063] While acquiring the surface white reference data, the control unit 90 turns on the light source 70a of the surface reading module 50 and moves the surface reading module 50 from the reference position directly below the automatic reading glass 25a (automatic reading position) to start the document conveyance (step S9), and reads the document (step S10). Then, it is determined whether the reading of the required predetermined number of sheets has been completed (step S11). If the reading is continuing (No in step S11), the process returns to step S9, and the document conveyance and reading are continued (steps S9, S10). If the reading of the predetermined number of sheets has been completed (Yes in step S11), the process ends.

[0064] According to the control example shown in FIG. 7, when the required document reading process is a double-sided reading process, before turning on the light source 70a of the surface reading module 50 to acquire the surface white reference data, the offset adjustment of the back surface reading module 51, the acquisition of the back surface black reference data, the gain adjustment, and the acquisition of the white reference data are executed in this order.

[0065] Thus, if it is immediately after double-sided reading is requested, the document conveyance device 27 is in a closed state, and the back surface reading module 51 can appropriately read the back surface white reference plate 57 without being affected by external light. Therefore, it is not necessary to provide an opening / closing detection function for the document conveyance device 27, and the number of parts of the document conveyance device 27 can be reduced and the cost can be reduced.

[0066] Also, until the offset adjustment, gain adjustment, and acquisition of black and white reference data of the back surface reading module 51 are completed, the surface reading module 50 stops at a predetermined position with the light source 70a turned off, so that the reading settings of the back surface reading module 51 can be appropriately completed without being affected by the irradiation light from the light source 70a.

[0067] After confirming that the acquisition of the white reference data for the back surface has been completed, the light source 70a of the front surface reading module 50 is turned on to execute the acquisition of the white reference data for the front surface. Since the front surface white reference plate 55 is installed under the transport guide 54, even when the original document transport device 27 is in an open state when acquiring the white reference data of the front surface reading module 50, there is no possibility of ambient light entering the condenser lens 71a of the front surface reading module 50.

[0068] Also, the front surface reading module 50 reads the front surface white reference plate 55 while moving to the automatic reading position to acquire the white reference data for the front surface. Since the irradiation light from the light source 70b of the back surface reading module 51 is in a positional relationship where it does not enter the condenser lens 71a of the front surface reading module 50, there is no possibility that the irradiation light of the back surface reading module 51 will affect as ambient light. Therefore, after acquiring the white reference data for the back surface, the back surface reading module 51 may be in a state where the light source is turned on for image reading.

[0069] Also, the timing of starting the conveyance of the original document is preferably to start the conveyance of the original document after acquiring the white reference data for the front surface of the front surface reading module 50, before or during the front surface reading module 50 starts moving to the automatic reading position, similar to the case of single-sided reading. By starting the conveyance of the original document without waiting for the front surface reading module 50 to complete moving to the automatic reading position in this way, the time from the reading request to the completion of reading can be shortened.

[0070] In addition, the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention. For example, in the above-described embodiment, as the image reading device, an image reading device including an image reading unit 6 and an original document transport device 27, having a back surface reading module 51 disposed in the original document transport device 27 and a front surface reading module 50 disposed in the image reading unit 6 has been described as an example. However, it can be similarly applied to an image scanner used separately from the image forming apparatus 100.

Industrial Applicability

[0071] The present invention can be used in an image reading apparatus capable of reading images on the front and back sides of a document at once using a front surface reading module and a back surface reading module. By using the present invention, it is possible to provide an image reading apparatus capable of obtaining appropriate double-sided reading images by performing light source lighting control of the front surface and back surface reading modules at a timing not affected by external light, and an image forming apparatus including the same.

Explanation of Signs

[0072] 6 Image reading unit (image reading apparatus) 25 Contact glass 27 Document conveying device (image reading apparatus) 31 Cover member 50 Front surface reading module (first reading module) 51 Back surface reading module (second reading module) 55 Front surface white reference plate (first white reference member) 57 Back surface white reference plate (second white reference member) 70a Light source (first light source) 70b Light source (second light source) 71a, 71b Condensing lenses 73a CMOS sensor (first sensor) 73b CMOS sensor (second sensor) 90 Control unit 100 Image forming apparatus

Claims

1. A contact glass on which a document is placed, a document conveying device that is provided on the upper surface of the contact glass so as to be openable and closable and conveys the document to an automatic reading position of the contact glass, a first reading module that is disposed below the contact glass so as to be reciprocally movable in a sub-scanning direction and is capable of reading an image on the front side of a fixed document placed on the contact glass and a conveyed document conveyed to the automatic reading position by the document conveying device, a second reading module that is disposed in the document conveying device and is capable of reading an image on the back side of the conveyed document, a first white reference member that is disposed opposite to the first reading module at a position different from the automatic reading position, a second white reference member that is disposed opposite to the second reading module, a control unit that controls the first reading module and the second reading module, In an image reading apparatus comprising: The first reading module includes a first light source and a first sensor that reads reflected light of light irradiated from the first light source to the conveyed document as image light, The second reading module includes a second light source and a second sensor that reads reflected light of light irradiated from the second light source to the conveyed document as image light, When the control unit executes a double-sided reading process of reading images on the front side and the back side of the conveyed document at once as a conveyance reading process of reading an image of the conveyed document, The image reading apparatus is characterized in that, after the double-sided reading process is requested, offset adjustment, gain adjustment, acquisition of black reference data for the back side, and acquisition of white reference data for the back side of the second reading module are executed.

2. The control unit executes offset adjustment and gain adjustment of the first reading module when the image reading apparatus is powered on, and acquires black reference data for the front side and white reference data for the front side after the conveyance reading process is requested. The image reading apparatus according to claim 1, characterized in that.

3. When the double-sided reading process is requested, the control unit acquires the black reference data for the front side with the first light source of the first reading module turned off before acquiring the offset adjustment, the gain adjustment, the black reference data for the back side, and the white reference data for the back side of the second reading module. After the offset adjustment, the gain adjustment, the acquisition of the black reference data for the back surface, and the acquisition of the white reference data for the back surface of the second reading module are completed, the first light source of the first reading module is turned on to acquire the white reference data for the front surface. The image reading apparatus according to claim 2, characterized in that.

4. When the conveyance reading process is requested, the control unit moves the first reading module to the automatic reading position while acquiring the white reference data for the front surface, and starts the conveyance of the conveyance document before the movement of the first reading module to the automatic reading position is completed. The image reading apparatus according to claim 1, characterized in that.

5. The image reading apparatus according to claim 1, characterized in that it does not have a mechanism for detecting whether the document conveyance device is in a closed state in contact with the contact glass or an open state separated from the contact glass.

6. An image forming apparatus equipped with the image reading apparatus according to any one of claims 1 to 5.

Images