JP5773928B2 - Image reading apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an image reading apparatus and an image forming apparatus that read an image of a document placed on a document table by moving a carriage.

  2. Description of the Related Art Conventionally, a configuration in which a movable carriage is provided below a document table is known as an image reading apparatus such as a copying machine, a facsimile machine, a scanner, or a multifunction machine. A light source for reading a document for illuminating the document is mounted on the carriage. In an image reading apparatus that employs a contact optical system, an image sensor for reading a document image is mounted on the carriage. In an image reading apparatus that employs a reduction optical system, a mirror for guiding the light reflected from the document to an image sensor disposed outside the carriage is mounted on the carriage.

  The carriage is provided so as to be able to reciprocate along a guide installed in parallel with the moving direction (so-called sub-scanning direction), and the document placed on the document table is moved in one direction along the guide. It is read by moving to. Further, the documents conveyed one by one from the document tray by the document conveying device are read in a state where the carriage is temporarily fixed at a specific image reading position on the guide. When the document is not read, the carriage stands by at a predetermined position on the guide (so-called home position), and the home position is used as a reference position to move in the sub-scanning direction or to the image reading position. Movement is realized.

  For the movement of the carriage, open loop control by a stepping motor is widely used. Therefore, an image reading apparatus that employs the control method needs to perform an initialization operation (origin recognition) for accurately placing the carriage at the home position at least when the power is turned on. In addition, there is an apparatus that performs an initialization operation every time a document reading is completed in order to realize a more accurate carriage movement.

  For example, in Patent Document 1, the above-described initialization operation is realized using an optical sensor. That is, a configuration is adopted in which the photo interrupter is fixed to the carriage and the light shielding plate is disposed at a position corresponding to the home position. In this configuration, by moving the carriage, it is possible to detect a specific position (movement origin) where the photo interrupter is shielded by the light shielding plate. Based on the specific position, the carriage can be arranged at the home position.

  Further, in Patent Document 2, the above-described initialization operation is realized by using an image sensor used for image reading. That is, a configuration is adopted in which a specific pattern that can be read by the image sensor is arranged at a specific position on the document table. In this configuration, the image sensor can detect the specific pattern by moving the carriage. Based on the specific position, the carriage can be arranged at the home position.

JP-A-8-149299 JP 2001-5119 A

  In the technique disclosed in Patent Document 2 described above, it is not necessary to provide an optical sensor such as a photo interrupter, so that the cost of the image reading apparatus can be reduced. However, since this technique is configured to detect a specific pattern by an image sensor, a light source for reading a document has to be turned on during an initialization operation, which has a demerit that power consumption increases. Further, if the technology is applied to an image reading apparatus that performs an initialization operation each time reading of a document is completed, it is assumed that a document exists on the document table and a portion that matches the specific pattern exists on the document. The home position may be detected incorrectly. Further, in this configuration, since the light source for reading the document is turned on when moving to the home position after reading the document, the light of the light source enters the eyes of the user who is trying to replace or take out the document. Probability is high. Since the brightness of the light source for reading a document is high and the visually recognized user feels very dazzling, there is a possibility that the user may feel uncomfortable.

  The present invention has been made in view of the above-described problems of the prior art, and can perform image reading in which a carriage can be appropriately arranged at a home position using an image sensor without turning on a light source for reading a document. An object is to provide an apparatus and an image forming apparatus.

  In order to achieve the above object, an image reading apparatus according to the present invention includes a carriage, an image sensor, a light emitting unit, and a reference position setting unit. The carriage is provided so as to be movable with respect to the document table. The image sensor reads an image of the document placed on the document table with the movement of the carriage. The light emitting unit emits light over a specific width in the carriage movement direction at a specific position within the movable range of the carriage. The reference position setting unit sets the reference position of the carriage based on the position of the carriage when the image sensor detects the light from the light emitting unit. The image sensor may be mounted on the carriage or may be fixed outside the carriage.

  In this configuration, when the moving carriage reaches an area irradiated with light having a specific width, the light enters the image sensor. Therefore, by detecting the incidence of light by the image sensor, it can be specified that the carriage exists in the light irradiation region of the light emitting unit. As a result, the reference position setting unit can set the carriage reference position (home position) based on the carriage position when light is detected by the image sensor. The reference position may be the position of the carriage itself when light is detected by the image sensor, or may be another position determined with the position as a reference (origin).

  In this configuration, since an optical sensor such as a photo interrupter used only for detecting the position of the carriage is not used, the cost is low. Further, it is not necessary to turn on the light source for reading the original when moving the carriage for the initialization operation. In addition, since the light emitting unit can be configured by, for example, one LED (Light Emitting Diode) and a slit having an opening having a predetermined width, the above-described conventional configuration in which an initialization operation is performed using an image sensor. As compared with the above, power consumption during the initialization operation can be significantly reduced.

  The light emitting unit can be configured to be turned on or off in synchronization with the reading cycle of the image sensor. For example, in a configuration in which the light emitting unit is switched on and off at every reading cycle of the image sensor, when the image sensor receives light from the light emitting unit in a specific reading cycle, the image sensor is removed from the light emitting unit in the next reading cycle. Does not receive the light. Then, in the next reading cycle, the image sensor receives light from the light emitting unit. That is, in this configuration, the light receiving state of the image sensor changes every time the carriage moves one step in the sub-scanning direction. Therefore, the position where the mismatch between the light reception state change pattern of the image sensor and the light emission pattern of the light emitting unit can be detected as the edge of the light emitted by the light emitting unit. With this configuration, the position of the carriage can be reliably specified by one reading cycle of the image sensor, that is, the minimum movement unit in the sub-scanning direction of the carriage. As a result, the carriage can be disposed at the home position with high accuracy and reliability.

  Further, the light source of the light emitting unit can be arranged in a region outside the document mounting region on the document table in a state facing the carriage that has reached the specific position. In this configuration, since the light source of the light emitting unit and the carriage that has reached the specific position can be arranged close to each other, the light emitted from the light emitting unit can reach the image sensor without being attenuated. Therefore, the light emission intensity of the light emitting unit can be set smaller. This configuration is particularly effective for an image reading apparatus that employs a contact optical system that can set the distance between the light source and the image sensor to be extremely short.

  On the other hand, in another aspect, the present invention can also provide an image forming apparatus including the above-described image reading apparatus and an image forming unit that prints a document image read by the image reading apparatus on a sheet.

  According to the present invention, the carriage can be appropriately arranged at the home position using the image sensor without turning on the light source for reading the document.

1 is a schematic configuration diagram showing an overall configuration of a scanner device according to an embodiment of the present invention. The figure which shows the hardware constitutions of the scanner apparatus in one Embodiment of this invention. 1 is a functional block diagram illustrating a scanner device according to an embodiment of the invention. The flowchart which shows an example of the reference position setting procedure which the scanner apparatus in one Embodiment of this invention implements The conceptual diagram which shows the method of detecting the light of the light emission part in one Embodiment of this invention. 1 is a schematic configuration diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. The functional block diagram which shows the other scanner apparatus in one Embodiment of this invention The flowchart which shows an example of the reference position setting procedure which the other scanner apparatus in one Embodiment of this invention implements The conceptual diagram which shows the method of detecting the light of the light emission part in one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings. In the following, the present invention is embodied as a scanner device that reads an image of a document placed on a document table with the movement of a carriage.

  FIG. 1 is a schematic configuration diagram illustrating an example of the overall configuration of the scanner device according to the present embodiment. 1A and 1B are views seen from a direction perpendicular to the moving direction of the carriage, and FIG. 1A is a schematic configuration view seen from a direction parallel to the document table (side view). FIG. 1 and FIG. 1B are schematic configuration diagrams (plan views) viewed from a direction perpendicular to the document table.

  As shown in FIGS. 1A and 1B, the scanner device 100 includes a main body 101 and a platen cover 102 attached above the main body 101. A document table 103 on which a document D 1 to be read is placed is provided on the upper surface of the main body 101, and the document table 103 is opened and closed by a platen cover 102. In FIG. 1B, the platen cover 102 is not shown, and the document table 103 and the document D1 are indicated by dotted lines.

  A scanning optical system 104 is provided inside the main body 101 below the document table 103. Although not particularly limited, here, the scanning optical system 104 is configured as a contact optical system (a so-called CIS (Contact Image Sensor) system). The scanning optical system 104 reads an image of the document D1 and generates digital data (image data) of the image.

  The scanning optical system 104 includes a carriage 110 and a guide 120. The carriage 110 includes a linear light source 111, an image sensor 112, and a 1 × optical system lens 113. Here, an LED array, a CMOS (Complementary Metal Oxide Semiconductor) line image sensor, and a gradient index lens are used as the light source 111, the image sensor 112, and the equal-magnification optical system lens 113, respectively. For example, the light source 111 illuminates the document D1 with each color of R (red), G (green), and B (blue). The equal-magnification optical system lens 113 forms an image of the reflected light (light image) from the document D1 on the light receiving surface of the image sensor 112. The image sensor 112 generates image data of the document D1 corresponding to each color of R (red), G (green), and B (blue) from the light image incident on the light receiving surface.

  The guide 120 is arranged on the side surfaces of the main body 101 facing each other in parallel with the document table 103. The carriage 110 is provided so as to reciprocate along the guide 120. The movement of the carriage 110 is realized by driving by a driving unit (not shown). In the present embodiment, a stepping motor that is a driving unit drives the carriage 110.

  The guide 120 is provided so that the image sensor 112 mounted on the carriage 110 can be moved from one end to the other end of at least the document placement area (document readable area) of the document table 103. In the present embodiment, the size of the document table 103 and the document placement possible area coincide with each other, and one end 103s (hereinafter referred to as a start end 103s) of the document table 103 orthogonal to the side surface of the main body 101 on which the guide 120 is provided. ) To the other end 103e (hereinafter referred to as end end 103e), the image sensor 112 is movable.

  In this scanning optical system 104, the carriage 110 is moved in one direction along the guide 120 (here, a direction from the start end 103 s to the end end 103 e: hereinafter referred to as a document reading direction). The image of the placed document D1 can be read by the image sensor 112.

  As shown in FIGS. 1A and 1B, in the scanner apparatus 100, the document table 103 is arranged offset with respect to the main body 101, and the start end 103s of the document table 103 and the start thereof are arranged. A space 105 is provided in the main body 101 between the end 103s and the side surface of the main body 101 facing the end 103s. Although not particularly limited, in this embodiment, the reference position (home position) of the carriage 110 is set to a position where the carriage 110 is disposed in the space 105.

  Further, the scanner device 100 includes a light emitting unit 130. The light emitting unit 130 emits light over a specific width in the moving direction of the carriage 110 at a specific position within the movable range of the carriage 110. Although not particularly limited, in this example, the light emitting unit 130 includes an LED 131 and a slit 132 that limits an irradiation range of light emitted from the LED 131. The slit 132 has an opening 133 that extends over a specific width d1 in the moving direction of the carriage 110. In this example, the light emitting unit 130 is fixed to the upper surface of the main body 101 adjacent to the document table 103 in the moving direction of the carriage 110 (that is, the upper surface of the main body 101 in the space 105) with the opening 133 facing downward. . Although not particularly limited, in the present embodiment, as shown in FIG. 1B, the light emitting unit 130 is not the entire width direction of the carriage 110 (direction perpendicular to the moving direction: so-called main scanning direction), but the central portion. Only provided.

  FIG. 2 is a hardware configuration diagram of a control system in the scanner device. The scanner device 100 according to the present embodiment drives a CPU (Central Processing Unit) 201, a RAM (Random Access Memory) 202, a ROM (Read Only Memory) 203, a driving unit that drives the carriage 110, and a document conveying device (not shown). A driver 204 corresponding to each drive unit such as a drive unit is connected via an internal bus 205. The ROM 203 stores a program, and the CPU 201 controls the scanner device 100 in accordance with an instruction of the control program. For example, the CPU 201 uses the RAM 202 as a work area, and controls the operation of each drive unit by exchanging data and commands with the driver 204.

  An operation panel 206, various sensors 207, and an external interface 208 are also connected to the internal bus 205. The operation panel 206 receives a user operation and supplies a signal based on the operation to the CPU 201. The sensor 207 includes various sensors such as an open / close detection sensor of the platen cover 102 and a document detection sensor on the document table 103. The external interface 208 includes various communication interfaces such as a USB interface and a network interface for transmitting image data generated by the scanner apparatus 100 to other devices. The CPU 201 executes, for example, a program stored in the ROM 203, thereby realizing the following means (functional blocks) and controlling the operation of each means in accordance with signals from each sensor.

  FIG. 3 is a functional block diagram of the scanner device of this embodiment. As shown in FIG. 3, the scanner device 100 of this embodiment includes a reference position setting unit 301, a light emission control unit 302, and a drive control unit 303.

  The reference position setting unit 301 sets the reference position of the carriage 110, that is, the home position, based on the position of the carriage 110 when the image sensor 112 detects the light emitted from the light emitting unit 130. The light emission control unit 302 controls turning on and off of the light emitting unit 130. The drive control unit 303 controls drive means (here, the above-described stepping motor) that drives the carriage 110.

  FIG. 4 is a flowchart illustrating an example of a reference position setting procedure performed by the scanner device 100. For example, the procedure includes predetermined conditions (conditions for starting the initialization operation of the carriage 110) such as the power supply to the scanner device 100 being completed and the reading of the document placed on the document table 103 being completed. The process proceeds with the satisfaction of the condition (step S401). The completion of reading of the document placed on the document table 103 is detected, for example, based on the size of the document D1 and the driving amount of the stepping motor, based on the movement of the carriage 100 from one end of the document D1 to the other end. Can be recognized.

  When the initialization operation start condition of the carriage 110 is satisfied in the scanner device 100, the drive control unit 303 starts the initialization operation of the carriage 110 (step S401 Yes). At this time, the drive control unit 303 instructs the light emission control unit 302 to turn on the light emitting unit 130. Receiving the instruction, the light emission control unit 302 turns on the LED 131 of the light emitting unit 130 (step S402).

  Next, the drive control unit 303 starts driving the carriage 110 (step S403). At this time, the drive control unit 303 drives the carriage 110 in a direction opposite to the image reading direction (that is, a direction from the end end 103e to the start end 103s: hereinafter referred to as an origin return direction). When the carriage 110 is located at the end of the guide 120 on the space 105 side when the power is turned on, the carriage 110 cannot be driven in the origin return direction. Therefore, when the power is turned on, it is possible to employ a configuration in which the carriage 110 is once driven in the image reading direction by a predetermined distance and then driven in the origin return direction.

  The drive control unit 303 that has started driving the carriage 110 in the home position return direction notifies the reference position setting unit 301 to that effect. Upon receiving the notification, the reference position setting unit 301 monitors the output signal of the image sensor 112 and tries to detect the output signal corresponding to the light emitted from the light emitting unit 130 (No in step S404).

  FIG. 5 is a conceptual diagram illustrating a method in which the reference position setting unit 301 detects light from the light emitting unit 130. FIG. 5A schematically shows a state in which the carriage 110 (image sensor 112) does not reach the light irradiation region S where the light of the specific width d1 is irradiated by the light emitting unit 130. FIG. FIG. 5B schematically shows a state in which the image sensor 112 reaches one end of the light irradiation region S and light including the one end is incident on the image sensor 112. FIG. 5C schematically shows a state in which the image sensor 112 reaches the other end of the light irradiation region S and light including the other end is incident on the image sensor 112. FIG. 5D schematically shows a state after the image sensor 112 passes through the light irradiation region S. FIG. 5E schematically shows an output signal (output voltage) of the image sensor 112 when the carriage 110 moves in one direction from the state shown in FIG. 5A to the state shown in FIG. 5D. FIG. In FIG. 5E, the horizontal axis corresponds to the carriage position, and the vertical axis represents an image sensor that passes through the light irradiation region S as the carriage 110 moves among all the image sensors that constitute the image sensor 112. Corresponds to the output voltage.

  The image sensor 112 generates a signal charge corresponding to the amount of incident light in a light receiving region of each image sensor that constitutes the image sensor 112, and extracts the signal charge as an output signal (voltage value). A signal is output through a signal output step. Since the two steps are performed in parallel, in the scanner device 100, the output signal corresponding to the light input to the image sensor 112 when the carriage 110 is at a specific position is the image after the carriage 110 moves one step. Output from the sensor 112. Therefore, strictly speaking, the output signal of the image sensor 112 does not correspond to the amount of light incident on the image sensor 112 at the position of the carriage 110 at the time when the output signal is acquired, but at the position of the carriage 110 before one movement step. Corresponds to the amount of incident light. However, in FIG. 5E, in a state in which such a deviation between the output signal and the carriage position is eliminated, that is, when the carriage 110 is at a certain position, the output signal corresponding to the amount of light incident at the position. Is illustrated.

  As shown in FIG. 5E, when the carriage 110 moves in one direction from the state shown in FIG. 5A to the state shown in FIG. 5D, the output voltage is the low potential region A, the low potential region. Transition region B from high potential region to high potential region, high potential region C, transition region D from high potential region to low potential region, and low potential region E change in this order. Note that the step-like change in the output voltage in the region B and the region D results from the carriage 110 being driven by the stepping motor as described above.

  Region A corresponds to a state in which the image sensor 112 has not reached the light irradiation region S (FIG. 5A). Similarly, the region E corresponds to the state after the image sensor 112 passes through the light irradiation region S (FIG. 5D). The region B corresponds to a state from when the image sensor 112 reaches one end of the light irradiation region S to when the light incident on the image sensor 112 becomes a constant light amount as the carriage 110 moves (FIG. 5 (b)). Similarly, the region D corresponds to a state from when the image sensor 112 reaches the other end of the irradiation region S to when no light enters the image sensor 112 as the carriage 110 moves (FIG. 5C). ). The region C has a constant amount of light incident on the image sensor 112 between the state shown in FIG. 5B and the state shown in FIG. This corresponds to a region where the amount of light incident on the image sensor 112 does not change.

  As can be understood from FIG. 5E, the carriage corresponding to the end of the light irradiation region S (the position corresponding to the end of the opening 133 in the carriage movement direction) based on the change in the output voltage of the image sensor 112. The position of the carriage 110 corresponding to the position 110 and the center of the light irradiation region S (the position corresponding to the center of the opening 133 in the carriage movement direction) can be detected (Yes in step S404). For example, the reference position setting unit 301 detects the position P where light is first detected in the region B and the position Q immediately before no light is detected for the first time in the region D as the ends of the light irradiation region S, An intermediate position M between the position P and the position Q can be specified as the movement origin of the carriage 110 (step S405). Although not particularly limited, here, the reference position setting unit 301 determines that light is detected when the output voltage of the image sensor 112 exceeds a predetermined threshold voltage Vt, and the output voltage of the image sensor 112 is determined. Is less than the threshold voltage Vt, it is determined that no light is detected. Further, the intermediate position M can be specified as a position advanced from the position P by a predetermined movement step, or a position retracted from the position Q by a predetermined movement step. In this case, the number of movement steps from the position P or the position Q is the width of the light irradiation region S in the carriage movement direction (that is, the positional relationship between the opening width d1 of the opening 133, the LED 131, the slit 132, and the equal-magnification optical system lens 113). ) Can be determined in advance.

  The reference position setting unit 301 that has specified the movement origin as described above sets the reference position (home position) of the carriage 110 based on the movement origin (step S406). The reference position may be the same as the above-described movement origin, or may be a position moved from the movement origin by a predetermined step in a designated direction.

  The reference position setting unit 301 that has set the reference position notifies the drive control unit 303 of the reference position. Upon receiving the notification, the drive control unit 303 moves the carriage 110 to the notified reference position. At this time, the drive control unit 303 instructs the light emission control unit 302 to turn off the light emitting unit 130. Receiving the instruction, the light emission control unit 302 turns off the LED 131 of the light emitting unit 130 (step S407).

  As described above, in this scanner device 100, the movement origin of the carriage 110 is specified based on whether or not the light emitted from the light emitting unit 130 enters the image sensor 112. In this configuration, since an optical sensor such as a photo interrupter used only for detecting the position of the carriage 110 is not used, the cost is low. Further, since it is not necessary to turn on the light source for reading the original when moving the carriage 110 for the initialization operation, the light does not enter the user's eyes and uncomfortable. In addition, since the light emitting unit 130 includes the LED 131 and the slit 132 having the opening 133 having a predetermined width d1, the power consumption is higher than that of the above-described conventional configuration in which the initialization operation is performed using the image sensor 112. Can be significantly reduced. In addition, since the width in the carriage movement direction of the light irradiation region S by the light emitting unit 130 is specified structurally, for example, a change in the output signal exceeding the width or narrower than the width is caused by the light of the light emitting unit 130. It can also be determined that the output signal is not changed. Therefore, by performing the determination, for example, it is possible to reduce erroneous detection that may occur when the user opens and closes the platen cover 102 while the carriage 110 is moving directly below the document table 103.

  In the scanner device 100, the LED 131 of the light emitting unit 130 is arranged on the upper surface of the space 105 provided in the main body 101 adjacent to the document table 103 along the moving direction of the carriage 110 so as to face the carriage 110. Yes. In this configuration, the LED 131 and the carriage 110 that has reached a position facing the LED 131 can be disposed close to each other. Therefore, the light emitted from the light emitting unit 130 can reach the image sensor 112 without being attenuated. As a result, the light emission intensity of the light emitting unit 130 can be set smaller, and the power consumption can be further reduced.

  In the above description, from the viewpoint of further reducing power consumption, the light emitting unit 130 is lit only during the initialization operation. However, the light emitting unit 130 may be lit constantly. In this case, the above-described light emission control unit 302 is not necessary.

  The above-described scanner device 100 can also be incorporated in a digital multi-function peripheral. FIG. 6 is a schematic configuration diagram illustrating an example of the overall configuration of the digital multifunction peripheral according to the present embodiment. In FIG. 6, the same reference numerals are given to components having the same operational effects as the components of the scanner device 100, and the detailed description below is omitted.

  As illustrated in FIG. 6, the multi-function device 600 includes a main body 601 including an image reading unit 620 (image reading device) and an image forming unit 640 having the same configuration as the scanner device 100 described above. The above document table 103 is provided on the upper surface of the main body 601, and the document table 103 is opened and closed by a platen cover 602. In the image forming apparatus 600, unlike the above-described scanner apparatus 100, the platen cover 602 includes a document conveying device 610, a document tray 611, and a paper discharge tray 612. An operation panel (not shown) is provided on the front surface of the multi-function device 100 so that the user can give a copy start or other instruction to the multi-function device 600, and can check the status and settings of the multi-function device 600. It has been.

  The image reading unit 620 provided below the document table 103 reads the image of the document by the scanning optical system 104 and generates image data as described above. Similar to the scanner device described above, the document can be placed on the document table 103. As described above, the image reading unit 620 generates the image data of the document placed on the document table 103 by moving the carriage 110 along the guide 120 in the document reading direction.

  In addition, the document can be placed on the document tray 611. The document conveying device 610 sends out the document set on the document tray 611 by the pickup roller 613 one by one to the conveying path 616. There is an image reading position P on the conveyance path 616. The conveyance roller 614 conveys the document to the image reading position P. When reading an image of a document set on the document tray 611, the image reading unit 620 temporarily fixes the carriage 110 according to the image reading position P. In the image forming apparatus 600, a document reading window 618 extending in the main scanning direction is provided below the image reading position P, and the carriage 110 is temporarily fixed directly below the document reading window 618. In this example, the document reading window 618 is provided between the light emitting unit 130 and the document table 103 in FIG. When the document passes through the image reading position P, the light source 111 illuminates the document. The light from the light source 111 is reflected by the original passing through the original reading window 618 and passing the original reading position P, and is introduced into the image sensor 112. The document that has passed the image reading position P is discharged to a discharge tray 612 by a discharge roller 615.

  In the image forming apparatus 600, the image data generated by the image reading unit 620 can be printed on a sheet by the image forming unit 640. Further, it can be transmitted to other devices (not shown) through the network 662 by the network interface 661.

  The image forming unit 640 prints image data generated by the image reading unit 620 or image data received from another device connected to the network 662 on a sheet. The image forming unit 640 includes a photosensitive drum 641. The photosensitive drum 641 rotates in one direction at a constant speed. Around the photosensitive drum 641, a charger 642, an exposure device 643, a developing device 644, and an intermediate transfer belt 645 are arranged in this order from the upstream side in the rotation direction. The charger 642 uniformly charges the surface of the photosensitive drum 641. The exposure device 643 irradiates the uniformly charged surface of the photosensitive drum 641 with light according to the image data to form an electrostatic latent image on the photosensitive drum 641. The developing device 644 attaches toner to the electrostatic latent image and forms a toner image on the photosensitive drum 641. The intermediate transfer belt 645 transfers the toner image on the photosensitive drum 641 to a sheet. When the image data is a color image, the intermediate transfer belt 645 transfers each color toner image onto the same sheet. The RGB color image is converted into C (cyan), M (magenta), Y (yellow), and K (black) format image data, and the image data of each color is input to the exposure unit 643.

  The image forming unit 640 feeds paper from the manual feed tray 651, the paper feed cassettes 652, 653, 654, and the like to the transfer unit between the intermediate transfer belt 645 and the transfer roller 646. Various sizes of paper can be placed or stored in the manual feed tray 651 and the paper feed cassettes 652, 653, and 654. The image forming unit 640 selects a sheet specified by the user or a sheet corresponding to the automatically detected document size, and feeds the selected sheet from the manual feed tray 651 or the cassettes 652, 653, 654 by the feeding roller 655. . The fed paper is transported to the transfer section by transport rollers 656 and registration rollers 657. The sheet on which the toner image is transferred is conveyed to the fixing device 648 by the conveyance belt 647. The fixing device 648 includes a fixing roller 658 with a built-in heater and a pressure roller 659, and fixes the toner image on the sheet by heat and pressing force. The image forming unit 640 discharges the sheet that has passed through the fixing unit 648 to the discharge tray 649.

  The image reading unit 620 of the image forming apparatus 600 can also specify the movement origin of the carriage 110 based on whether or not the light emitted from the light emitting unit 130 is incident on the image sensor 112. Therefore, it is possible to realize a configuration in which the carriage 110 can be appropriately arranged at the home position that is a reference position for movement of the carriage 110 in the document reading direction and movement to the image reading position P when reading the document.

  In the above description, the configuration in which the light emitting unit 130 is turned on during the initialization operation has been described. However, the light emitting unit 130 may blink during the initialization operation.

  FIG. 7 is a functional block diagram of another scanner device according to this embodiment. As shown in FIG. 7, the scanner device 700 includes a reference position setting unit 301, a light emission control unit 302, and a drive control unit 303, similar to the scanner device 100 described above. The overall configuration of the scanner device 700 is the same as the overall configuration of the scanner device 100 shown in FIG.

  On the other hand, the scanner device 700 is different from the scanner device 100 in that an image reading cycle signal is input to the light emission control unit 302 from a reading cycle signal generation unit 701 that generates an image reading cycle signal. The image reading cycle signal is a signal that defines an image reading cycle (that is, an output signal output cycle) in the image sensor 112 that is a line image sensor, and the image sensor 112 is configured according to the cycle defined by the image reading cycle signal. An output signal is sequentially output from each imaging device. Therefore, image data for one line in a direction orthogonal to the movement direction of the carriage 110 (so-called main scanning direction) is acquired in synchronization with the image reading cycle signal. Note that, as described above, in the image sensor 112, the charge generation step and the signal output step are performed in parallel, so that each image sensor responds to incident light in synchronization with the period in which the output signal is output. A signal charge is generated. The image reading cycle signal is realized by, for example, a pulse signal repeatedly generated at a constant cycle.

  FIG. 8 is a flowchart illustrating an example of a reference position setting procedure performed by the scanner device 700. Similar to the scanner apparatus 100, the procedure proceeds with a trigger when the initialization operation start condition of the carriage 110 is satisfied (step S801).

  When the initialization operation start condition of the carriage 110 is satisfied in the scanner device 700, the drive control unit 303 starts the initialization operation of the carriage 110 (Yes in step S801). At this time, the drive control unit 303 instructs the light emission control unit 302 to start blinking of the light emitting unit 130. Receiving the instruction, the light emission control unit 302 starts blinking the LED 131 of the light emitting unit 130 in synchronization with the image reading cycle signal input from the reading cycle signal generation unit 701 (step S802). Here, the light emission control unit 302 switches between turning on and off the LED 131 for each period defined by the image reading period signal (that is, for each reading period of the image sensor 112).

  Next, the drive control unit 303 starts driving the carriage 110 (step S803). At this time, like the scanner device 100, the drive control unit 303 drives the carriage 110 in the origin return direction. As described above, the image reading cycle signal defines the acquisition cycle of image data for one line by the image sensor 112. Therefore, image data cannot be acquired properly unless the carriage 110 is moved in synchronization with the period. That is, the drive control unit 303 moves the carriage 110 by one step in synchronization with the cycle of the image reading cycle signal.

  The drive control unit 303 that has started driving the carriage 110 in the home position return direction notifies the reference position setting unit 301 to that effect. Upon receiving the notification, the reference position setting unit 301 monitors the output signal of the image sensor 112 corresponding to the light emitted from the light emitting unit 130, and tries to detect the output signal corresponding to the light emitted from the light emitting unit 130 (No in step S804). .

  FIG. 9 is a conceptual diagram illustrating a method in which the reference position setting unit 301 detects light from the light emitting unit 130. FIG. 9 schematically shows an output signal (output voltage) of the image sensor 112 when the carriage 110 moves in one direction from the state shown in FIG. 5A to the state shown in FIG. 5D. Yes. In FIG. 9, the horizontal axis corresponds to the carriage position, and the vertical axis corresponds to the output voltage of the image sensor that passes through the light irradiation region S as the carriage 110 moves among all the image sensors that constitute the image sensor 112. . Carriage positions a to m in FIG. 9 correspond to positions where the carriage 110 stops when the carriage 110 moves one step. In FIG. 9, the output signal is illustrated in a state in which the deviation between the output signal and the carriage position is eliminated, as in FIG. In this example, when the light emitting unit 130 is lit, the light of the light emitting unit 130 enters the image sensor 112 when the carriage 110 is positioned between the position d and the position j. In FIG. 9, the region is shown as a light irradiation region S.

  Further, the upper part of FIG. 9 shows the state of the light emitting unit 130 when the carriage 110 is in each position. “Dot” indicates that the LED 131 is turned on, and “Off” indicates that the LED 131 is turned off. In this example, as described above, the light emission control unit 302 switches on / off the LED 131 for each reading cycle of the image sensor 112, and the drive control unit 303 moves the carriage 110 for each reading cycle of the image sensor 112. Move one step. Therefore, each time the carriage 110 moves by one step, the LED 131 is turned on and off. Specifically, FIG. 9 shows that the LED 131 is off when the carriage 110 is at position a, position c, position e, position g, position i, position k, and position m, and that the carriage 110 is at position b, It indicates that the LED 131 is lit when it is at position d, position f, position h, position j, position l.

  As described above, in this example, when the carriage 110 moves in one direction during the initialization operation and is between the position d and the position j, light enters the image sensor 112 if the LED 131 is lit. . However, as shown in FIG. 9, the LED 131 is lit when the carriage 110 is at position d, position f, position h, and position j, but when the carriage 110 is at position e, position g, and position i, the LED 131 is Off. Therefore, as shown in FIG. 9, at position d, position f, position h, and position j, an output voltage corresponding to the state where light is incident on the image sensor 112 is output, and at position e, position g, and position i, the image sensor. An output voltage (low potential) corresponding to a state in which no light is incident on 112 is output. In FIG. 9, for reference, the output voltage when the LED 131 is lit at the position e, the position g, and the position i is indicated by a dotted line.

  As can be understood from the above, in the scanner device 700, when the carriage 110 moves in the light irradiation region S of the light emitting unit 130, the low potential that matches the blinking pattern of the LED 131 in the output signal of the image sensor 112. Output appears. That is, by detecting the position where the pattern where the low potential of the output voltage appears does not match the pattern of turning off the LED 131, the end of the light irradiation region S (the position corresponding to the end of the opening 133 in the carriage movement direction). ) Can be detected.

  Here, as described above, the reference position setting unit 301 determines that light is detected when the output voltage of the image sensor 112 exceeds a predetermined threshold voltage Vt, and the output voltage of the image sensor 112 is the threshold value. When the voltage is equal to or lower than Vt, it is determined that no light is detected. In this case, in the example of FIG. 9, the reference position setting unit 301 switches between “light detection state” and “light non-detection state” for each movement step, starting from the position f where light is first detected. Detect patterns. That is, the reference position setting unit 301 sequentially detects a light detection state (position f), a light non-detection state (position g), a light detection state (position h), and a light non-detection state (position i). When the carriage 110 moves to the position j, the reference position setting unit 301 detects a light non-detection state. Thus, when the light non-detection state (low potential) continues, the reference position setting unit 301 detects the position (in this case, the position j) as the end of the light irradiation region S (Yes in step S804). Then, the reference position setting unit 301 identifies the position j or a position that has been retracted from the position j by a movement step specified in advance as the movement origin of the carriage 110 (step S805). Note that the reference position setting unit 301 detects the position d where light should be detected within the light irradiation region S based on the position f where light is first detected and the position h where light is detected next. Can also be detected as the end of the light irradiation region S.

  The reference position setting unit 301 specifying the movement origin as described above sets the reference position (home position) of the carriage 110 based on the movement origin (step S806). The reference position may be the same as the above-described movement origin, or may be a position moved from the movement origin by a predetermined step in a designated direction.

  The reference position setting unit 301 that has set the reference position notifies the drive control unit 303 of the reference position. Upon receiving the notification, the drive control unit 303 moves the carriage 110 to the notified reference position. At this time, the drive control unit 303 instructs the light emission control unit 302 to turn off the light emitting unit 130. Receiving the instruction, the light emission control unit 302 turns off the LED 131 of the light emitting unit 130 (step S807).

  As described above, in the scanner device 700, the moving origin of the carriage 110 is specified based on the blinking light emitted from the light emitting unit 130 to the image sensor 112. In particular, in a configuration in which the LED 131 is turned on and off for each movement step of the carriage 110, the position of the carriage is reliably specified by one reading cycle of the image sensor 112, that is, the minimum movement unit in the sub-scanning direction of the carriage. Can do. As a result, the carriage can be arranged at the home position with extremely high accuracy.

  In addition, in the light irradiation region S of the light emitting unit 130, erroneous detection is prevented if the image sensor 112 is configured to detect light at least twice (that is, a configuration in which light detection, light non-detection, and light detection change occur). Thus, the carriage 110 can be set to the reference position more reliably than the scanner device 100 described above. Specifically, in the above-described scanner device 100, when the platen cover 102 is opened and closed at a specific timing during the initial operation of the carriage 100, the moving origin may be erroneously detected. Erroneous detection can be prevented.

  In the above description, the LED 131 is turned on and off for each moving step of the carriage 110. However, the LED 131 can be blinked in an arbitrary pattern. For example, the lighting and extinguishing of the LED 131 may be switched for each of a plurality of movement steps of the carriage 110, or the pattern of “lit”, “lit”, and “dark” may be repeated. In the above, in order to further reduce the power consumption, the light emitting unit 103 is blinked when the initialization operation is started. However, the light emission control unit 302 may be configured to blink the light emitting unit 130 at all times. .

  As described above, according to the present invention, the carriage can be appropriately arranged at the home position using the image sensor without turning on the light source for reading the document.

  The above-described embodiments do not limit the technical scope of the present invention, and various modifications and applications other than those already described are possible within the scope of the present invention. For example, in the above-described embodiment, a CIS scanner device including one carriage on which an image sensor is mounted is illustrated as an example of a configuration in which cost reduction is particularly desired. However, the present invention uses a first carriage having a light source and a mirror and a second carriage having two mirrors, and the image sensor fixed outside the carriage by the movement of the first and second carriages. The present invention is also applicable to a scanner apparatus including a reduction optical system (so-called CCD system) that forms an image of a document placed on a document table.

  In the above-described embodiment, the light emitting unit is arranged at the center in the main scanning direction. However, if the light can be emitted over a specific width in the movement direction of the carriage, the installation position is arbitrary. In the above-described embodiment, the light source of the light emitting unit is arranged to face the carriage and directly uses light. However, as long as light over a specific width in the carriage movement direction can be irradiated, other positions are used. The light source may be installed to use reflected light. In addition, in the above-described embodiment, the light emitting unit is configured by the slit having the opening having the predetermined width and the light source. However, as long as light over a specific width in the movement direction of the carriage can be irradiated, the structure is also arbitrary. .

  Furthermore, in the above-described embodiments, the present invention is embodied as a scanner device and a digital multifunction peripheral. The present invention can also be applied to any image reading apparatus or image forming apparatus that reads an image of a document placed on the document.

  According to the present invention, the carriage can be appropriately arranged at the home position by using the image sensor without turning on the light source for reading the document, which is useful as an image reading apparatus and an image forming apparatus.

100, 700 Scanner device (image reading device)
DESCRIPTION OF SYMBOLS 103 Document stand 110 Carriage 112 Image sensor 130 Light emission part 301 Reference position setting part 302 Light emission control part 600 Image forming apparatus 620 Image reading part (image reading apparatus)
640 Image forming unit 701 Reading cycle signal generating unit

Claims (3)

A carriage that is movable relative to the document table;
An image sensor that reads an image of a document placed on the document table with the movement of the carriage;
A light emitting unit that emits light over a specific width in the movement direction of the carriage at a specific position within a movable range of the carriage;
A reference position setting unit that sets a reference position of the carriage based on the position of the carriage when the image sensor detects light from the light emitting unit;
Equipped with a,
The light source of the light emitting unit is disposed in a region outside the document mounting area on the document table in a state facing the carriage that has reached the specific position.
Image reading device.   The image reading apparatus according to claim 1, wherein the light emitting unit is turned on or off in synchronization with a reading cycle of the image sensor. The image reading apparatus according to claim 1 or 2 ,
An image forming unit that prints a document image read by the image reading device on paper;
An image forming apparatus comprising:

Images