JP2012249241A - Image reading apparatus - Google Patents

Abstract

In an image reading apparatus capable of reading both sides of an original, an amount of light applied to the original is adjusted.
In an image reading apparatus 1, a CIS 30 and a CIS 40 arranged with a conveyance path 22 interposed therebetween are arranged at positions that are affected by light emitted from a light source of a CIS on the opposite side. In the first state Z1 in which at least one of the leading edge and the trailing edge of the document G in the transport direction indicated by the arrow 37 exists between the position P2 and the position P3, the leading edge of the document G is positioned downstream of the position P3. Then, control is performed so as to reduce the amount of light emitted from the light sources 31 and 41 rather than in the second state Z2 where the trailing edge of the document G is located upstream of P2.
[Selection] Figure 9

Description

  The present invention relates to a technique for adjusting the amount of light applied to a document in an image reading apparatus.

  2. Description of the Related Art Conventionally, an image reading apparatus that reads both sides of a document conveyed along a conveyance path is known. For example, a reading unit that is placed on the upstream side of the conveyance path and reads one side of the document, and a reading unit that is placed on the downstream side of the conveyance path and reads the other side of the document are placed on the opposite side via the conveyance path. It may be arranged (for example, patent document 1). In this apparatus, light emitted from the light source of one reading unit may be received by the light receiving element of the other reading unit. For this reason, when reading both sides of the document, the light emitted from the light source of one reading unit may affect the reading result of the other reading unit, and the reading result may be uneven.

  In the conventional technology, when both sides of a document are read, irradiation of light from the light sources of both reading units is maintained until reading of both reading units is completed. As a result, when reading of the reading unit on the upstream side of the transport path is finished, irradiation of light from the light source of the upstream side reading unit is stopped even though reading of the reading unit on the downstream side of the transport path is being performed. Unlike the case, the amount of light emitted from both light sources could be kept constant over the period during which the reading unit reads the document.

JP 2004-254340 A

  However, when reading of the reading unit on the downstream side of the conveyance path is executed after the reading of the reading unit on the upstream side of the conveyance path is finished, the document covers the reading unit on the downstream side of the conveyance path, while on the upstream side of the conveyance path Since the side reading unit is not covered, the light emitted from the light source of the reading unit on the upstream side of the transport path is received by the light receiving element of the reading unit on the downstream side of the transport path. As a result, the amount of light received by the light receiving element of the reading unit on the downstream side of the conveyance path is increased as compared with the case where both reading units perform reading and the document covers both reading units, and the reading result It is impossible to prevent unevenness from occurring. A similar problem occurs in the light receiving element of the reading unit on the upstream side of the conveyance path when reading of the reading unit on the upstream side of the conveyance path is being performed and reading of the reading unit on the downstream side of the conveyance path is not started. .

  The present specification discloses a technique for adjusting the amount of light applied to an original in an image reading apparatus capable of reading both sides of the original.

  An image reading device disclosed in this specification is provided on one side along a conveyance path that conveys a document along a conveyance path, and irradiates light on one surface of the document. A first light source, a first light receiving element that receives light reflected by one surface of the document and outputs a read image signal, and the transport path from the first reading unit. A second light source located on the other downstream side along the transport path and irradiating light on the other surface of the document; and light reflected by the other surface of the document And a second light receiving element that outputs a read image signal, and at least one of the first light receiving element and the second light receiving element emits light emitted from another light source. Is placed at a position that is affected by, and when reading both sides of the document, A first state in which both the first light source and the second light source are turned on, and at least one of the leading edge and the trailing edge of the document in the direction along the conveyance path exists between the first reading unit and the second reading unit. In the second state, the leading edge of the document is positioned downstream of the second reading unit, and the trailing edge of the document is positioned upstream of the first reading unit. A light source controller that controls the first light source and the second light source so as to reduce the amount of light emitted from the two light sources.

  In the image reading apparatus, the amount of light emitted from the first light source and the second light source in the first state is higher than that of the white member disposed at a position facing each light receiving element. The amount of light adjusted by turning on the light source and the second light source at the same time, and the amount of light emitted from the first light source and the second light source in the second state is white light disposed at a position facing each light receiving element. It is good also as a structure which is the light quantity adjusted by lighting the said 1st light source and the 2nd light source separately with respect to a member.

  In the image reading apparatus, each of the first light receiving element and the second light receiving element has a maximum amount of received light, and each has a plurality of reading elements. The light reflected by the member is received, and in each state, the amount of light emitted from the first light source and the second light source is such that the maximum value of the light receiving amount of the reading element in each light receiving element is equal to the maximum light receiving amount. A configuration may be adopted in which the light amount is adjusted to be the largest within a range that does not exceed.

  In the image reading apparatus, the first light receiving element and the second light receiving element have a maximum amount of received light, and each has a plurality of reading elements. The reflected light is received, and the amount of light emitted from the first light source and the second light source in the first state is an average of the amount of light received by the reading element in the first light receiving element and the second light receiving element. A configuration may be adopted in which the light amount is adjusted to be the largest within a range where the value does not exceed the maximum light reception amount.

  In the image reading apparatus disclosed in the present specification, at least one of the leading edge and the trailing edge of the document exists between the first reading section and the second reading section, and at least one of the first reading section and the second reading section. The amount of light of the first light source and the second light source in the first state where the light emitted from the light source is not covered with the original is determined by the first reading unit and the second reading unit at both the leading and trailing ends of the original. Control is performed so that the light emitted from any light source of the first reading unit and the second reading unit is less than the light amounts of the first light source and the second light source in the second state where the original is covered. To do. According to this image reading apparatus, the first reading unit and the second reading unit are arranged on the opposite side along the conveyance path, and the light emitted from the light source of the reading unit not covered with the document is arranged on the opposite side. Even when the light is received by the light receiving element of the reading unit, it is possible to suppress a difference in the amount of light received by the light receiving element in the first state and the second state, and unevenness occurs in the read image signal. Is suppressed.

Perspective view of the image reading apparatus 1 Schematic sectional view of the image reading apparatus 1 The figure for demonstrating the structure of the reading part 24 Block diagram schematically showing the electrical configuration of the image reading apparatus 1 Flow chart showing the reading process Flow chart showing light amount adjustment processing The flowchart which shows the light quantity adjustment process in the 2nd state Z2. The flowchart which shows the light quantity adjustment process in the 1st state Z1 of Embodiment 1. FIG. The figure which shows the 1st state Z1 The figure which shows 2nd state Z2 The figure which shows the lighting time T of the light sources 31 and 41 in the 1st state Z1 and the 2nd state Z2. The flowchart which shows the light quantity adjustment process in the 1st state Z1 of Embodiment 2. FIG.

<Embodiment 1>
Embodiment 1 will be described with reference to FIGS. 1 to 11.

1. FIG. 1 is a perspective view showing an appearance of an image reading apparatus 1 according to the present embodiment, and FIG. 2 is a schematic internal configuration diagram of the image reading apparatus 1. In the following description, the left side of the paper is the front side of the apparatus, and the right side of the paper is the rear side of the apparatus. The image reading apparatus 1 includes a paper feed tray 2, a main body unit 3, and a paper discharge tray 4. The image reading apparatus 1 according to the present embodiment conveys a plurality of originals G placed on the paper feed tray 2 by a user to the paper discharge tray 4 and the reading unit 24 included in the main body unit 3. This is a sheet feed scanner that reads using (see FIG. 2). The document G is an example of a sheet, and may be paper or an OHP sheet.

  The paper feed tray 2 is provided on the rear side of the main body 3 with the front side inclined downward. Guides 7A and 7B are provided at both left and right ends of the sheet feeding tray 2 so as to be movable in the left-right direction. In the image reading apparatus 1, the distance between the guides 7 </ b> A and 7 </ b> B is adjusted to be equal to the width of the original G by pushing or narrowing the guides 7 </ b> A and 7 </ b> B by the user. The document G is placed between 7B.

  As shown in FIG. 2, a conveyance path 22 extending from the front end of the paper feed tray 2 to the rear end of the paper discharge tray 4 is provided in the main body 3, and a pickup roller is provided around the conveyance path 22. 20, a separation pad 21, a feed roller 23, a reading unit 24, a discharge roller 25, a front sensor 26, and a rear sensor 27 are provided.

  The pickup roller 20 is disposed on the front side of the paper feed tray 2, and draws one or a plurality of documents G placed on the paper feed tray 2 into the main body 3 by a frictional force. The separation pad 21 is disposed so as to face the pickup roller 20 and separates a plurality of documents G one by one by frictional force. As a result, the originals G are conveyed one by one into the main body 3.

  The feed roller 23 is provided on the downstream side of the conveyance path 22 relative to the pickup roller 20 and the like, is driven by a motor (not shown), and conveys the document G drawn into the main body 3 along the conveyance path 22. To do. The reading unit 24 is provided on the downstream side of the conveyance path 22 with respect to the feed roller 23, and reads the document G conveyed along the conveyance path 22 by the feed roller 23.

  The discharge roller 25 is provided on the downstream side of the conveyance path 22 with respect to the reading unit 24, and sends the document G that has been subjected to image reading processing by the reading unit 24 to the discharge tray 4. The discharge tray 24 is provided on the front side of the main body 3 with the front side inclined downward, and the documents G sent out by the discharge roller 25 are stacked. That is, the pickup roller 20, the feed roller 23, and the discharge roller 25 form a conveyance unit 28 that conveys the document G placed on the paper feed tray 2 along the conveyance path 22. In the conveyance unit 28, the pickup roller 20, the feed roller 23, and the discharge roller 25 rotate in conjunction with a common motor (not shown) to convey the original G.

  The front sensor 26 is provided on the front end side of the paper feed tray 2, detects the presence or absence of the document G arranged on the paper feed tray 2, and outputs a detection signal SG 1 corresponding to the detection result. The rear sensor 27 is provided on the downstream side of the transport path 22 relative to the feed roller 23, detects the presence or absence of the document G at the position P1 (see FIG. 3) of the transport path 22, and outputs a detection signal SG2 corresponding to the detection result. To do. The front sensor 26 and the rear sensor 27 may be, for example, a contact sensor such as a pressure sensor or a non-contact sensor such as an optical sensor or a magnetic sensor.

  FIG. 3 is a schematic configuration diagram of the reading unit 24. The reading unit 24 includes a pair of CISs 30 and 40 that are provided on the downstream side of the conveyance path 22 with respect to the rear sensor 27 and are arranged to face each other with the conveyance path 22 interposed therebetween. The pair of CISs 30 and 40 are disposed with the conveyance path 22 interposed therebetween and are provided so as not to move relative to each other. As shown in FIG. 3, the CIS (an example of the first reading unit) 30 is disposed on the lower side (an example of one side) along the conveyance path 22 and passes through the surface 34 </ b> A side of the platen glass 34. An image on the front surface (an example of one surface) of the original G is read. The CIS (an example of the second reading unit) 40 is located on the downstream side of the conveyance path 22 from the CIS 30 in the conveyance direction indicated by the arrow 37 in FIG. The CIS 40 is arranged on the upper side (an example of the other side) along the conveyance path 22 and reads an image on the back surface (an example of the other surface) of the document G passing through the front surface 44A side of the platen glass 44.

  The CIS 30 includes a light source (an example of a first light source) 31, a light receiving unit (an example of a first light receiving element) 32, and a rod lens array 36 in addition to the platen glass 34. The light source 31 includes a light emitting diode, and the light receiving unit 32 includes a plurality of light receiving elements (not shown) arranged linearly in a direction perpendicular to the paper surface of FIG. Note that the structure of the CIS 40 is basically the same as the structure of the CIS 30, and redundant description is omitted. A white reference plate 33 is disposed on the back surface 34B of the platen glass 34 at a position facing a light receiving portion (an example of a second light receiving element) 42 of the CIS 40. A light receiving portion of the CIS 30 is disposed on the back surface 44B of the platen glass 44. A white reference plate 33 is disposed at a position opposite to 32.

  The light source 31 irradiates the original G conveyed on the conveyance path 22 via the platen glass 34 or the white reference plate 43 of the CIS 40 with the light L1. The light receiving unit 32 is disposed on the downstream side of the light source 31 in the carriage 35, and is reflected from the original G or the white reference plate 43 of the CIS 40 at the position P <b> 2 provided on the downstream side of the position P <b> 1 in the transport path 22. The reflected light L2 (reflected light from the original G in FIG. 3) is received.

  Further, the light source 41 (an example of a second light source) irradiates the light L <b> 3 to the original G transported through the transport path 22 through the platen glass 44 or the white reference plate 33 of the CIS 30. The light receiving unit 42 is disposed on the downstream side of the light source 41 in the carriage 45, and is reflected from the original G or the white reference plate 43 of the CIS 40 at the position P 3 provided on the downstream side of the position P 2 in the transport path 22. The reflected light L4 (reflected light from the original G in FIG. 3) is received.

  When the document G transported through the transport path 22 does not exist at the position P2 of the transport path 22, the light L1 irradiated from the light source 31 is irradiated onto the white reference plate 43, and a part of the light passes through the platen glass 44. The light is received by the light receiving unit 42. Further, when the document G transported through the transport path 22 does not exist at the position P3 of the transport path 22, the light L3 irradiated from the light source 41 is irradiated onto the white reference plate 33, and a part thereof is platen glass. Light is received by the light receiving unit 32 via 34. That is, in the reading unit 24, the light receiving unit 42 is disposed at a position affected by the light L1 emitted from the light source 31, and the light receiving unit 32 is affected by the light L3 emitted from the light source 41. It can be said that it is arranged at a position.

  The white reference plate 33 and the white reference plate 43 are not limited to the white reference plate, and may be a gray reference plate. In addition to the configuration arranged on the back surfaces 34B and 44B of the platen glasses 34 and 44 as shown in FIG. For example, it is good also as a structure embed | buried under the platen glass 34,44. As shown in FIG. 3, the CIS 30 acquires white reference data necessary for shading correction and the like using the white reference plate 43 included in the CIS 40, and the CIS 40 performs shading correction and the like using the white reference plate 33 included in the CIS 30. Acquire necessary white reference data.

  As shown in FIG. 1, the main body unit 3 includes a power switch and various setting buttons, an operation unit 5 that receives an operation command from the user, a light emitting diode, and the like. 1 includes a display unit 6 for displaying the status of 1.

2. FIG. 4 is a block diagram schematically showing the electrical configuration of the image reading apparatus 1. As shown in FIG. 4, the image reading apparatus 1 includes an ASIC (application specific integrated circuit) 10 that controls each unit of the image reading apparatus 1. The ASIC 10 includes a central processing unit (hereinafter referred to as CPU) 11, ROM 12, and RAM 13, and a device control unit 15, an analog front end (hereinafter referred to as AFE) 16, a drive circuit 17, CISs 30 and 40, and the like via a bus 14. The unit 28, the operation unit 5, the display unit 6, the front sensor 26, the rear sensor 27, and the like are connected.

  Various programs for controlling the operation of the image reading apparatus 1 are stored in the ROM 12, and the CPU 11 functions as the light source control unit 50 and the like according to the program read from the ROM 12 and controls each unit. The drive circuit 17 drives a motor (not shown) and drives various rollers included in the transport unit 28.

  The device control unit 15 is connected to each of the CISs 30 and 40, and transmits to the CISs 30 and 40 a signal for controlling the lighting / extinguishing of the light sources 31 and 41 and the lighting time T based on a command from the CPU 11. When receiving signals from the device control unit 15, the CISs 30 and 40 turn on the light sources 31 and 41 and cause the light sources 31 and 41 to emit light over the lighting time T. At that time, the CISs 30 and 40 receive the reflected light reflected from the original G or the white reference plates 33 and 43 conveyed along the conveyance path 22 by the light receiving units 32 and 42 based on a command from the CPU 11. The read light (an example of the read image signal) that is an analog signal corresponding to the amount of light received by the light receiving units 32 and 42 is output to the AFE 16. The CISs 30 and 40 receive the reflected light using the light receiving elements of the light receiving units 32 and 42 and sequentially output read voltages corresponding to the amount of light received by the light receiving elements to the AFE 16.

  The AFE 16 is connected to each of the CISs 30 and 40, and converts the read voltage output from the CISs 30 and 40 into a gradation value that is a digital signal (another example of the read image signal) based on a command from the CPU 11. A / D conversion circuit is included. The AFE 16 has a predetermined input range and resolution (for example, gradation of 0 to 255 if it is 8 bits). The AFE 16 performs A / D conversion on the read voltage output from the CISs 30 and 40 to a gradation value of 8 bits (0 to 255). The gradation values A / D converted by the AFE 16 are stored in the RAM 13 via the bus 14. As a result, the gradation value, which is read data read using the light receiving elements of the CISs 30 and 40, is stored in the RAM 13.

3. Reading Processing Next, processing in the CPU 11 when reading the document G using the reading unit 24 will be described with reference to FIGS. 5 to 11.

  FIG. 5 shows a flowchart of the first embodiment executed by the CPU 11 according to a predetermined program. When it is confirmed by the front sensor 26 that the document G is placed on the paper feed tray 2 of the image reading device 1 and a reading instruction for reading both sides of the document G is input via the operation unit 5, the CPU 11 performs processing. To start. When starting the process, the CPU 11 first executes a light amount adjustment process for the light sources 31 and 41 (S2).

  In the image reading apparatus 1 of the present embodiment, as shown in FIG. 9 or FIG. 10, when reading the document G, the document G transported along the transport path 22 is one of the positions P2 and P3 of the transport path 22. A first state (see FIG. 9) Z1 in which at least one of the leading end and the trailing end in the transport direction of the document G indicated by the arrow 37 exists between the positions P2 and P3, and the transport path 22 A state where both the positions P2 and P3 exist, that is, the leading edge in the conveyance direction of the document G is located downstream from the position P3, and the trailing edge in the conveyance direction of the document G is located upstream from the position P2. Switching between two states (see FIG. 10) Z2. Therefore, in this embodiment, the light quantity of the light sources 31 and 41 is adjusted in each state of the 1st state Z1 and the 2nd state Z2.

  As shown in FIG. 6, in the light amount adjustment process, the CPU 11 first adjusts the light amount of the light source 31 when only the light source 31 is turned on (S32). This adjustment is performed with the light source 41 turned off and the light source 31 turned on, and the lighting time T1 of the light source 31 when only the light source 31 is turned on is determined.

  As shown in FIG. 7, in the light amount adjustment process of the light source 31, the CPU 11 first sets the lighting time T of the light source 31 that can be shortened / extended in units of the reference time KT to the maximum time Tmax (S42). The CPU 11 turns on the light source 31 for the set lighting time T, reads one line of the white reference plate 43 using each light receiving element of the light receiving unit 32, and acquires white reference data for each light receiving element (S44). The CPU 11 converts the acquired white reference data into a gradation value by the AFE 15, and among the gradation values of each light receiving element, the maximum gradation value WKmax at which the gradation value is the largest is determined as the maximum gradation value ( An example of the maximum light receiving amount, in the case of 8 bits, 255) It is compared with Kmax (S46).

  When the maximum gradation value WKmax of the white reference gradation data is equal to or greater than the maximum gradation value Kmax of the AFE 16 (YES in S46), the CPU 11 shortens the lighting time T by the reference time KT (S48), and the processing from S44 repeat. On the other hand, when the maximum gradation value WKmax of the white reference gradation data is smaller than the maximum gradation value Kmax of the AFE 16 (NO in S46), the CPU 11 sets the lighting time T to the lighting time of the light source 31 when only the light source 31 is turned on. T1 is stored in the RAM 13 (S50), and the process is terminated.

  Next, the CPU 11 adjusts the light amount of the light source 41 when only the light source 41 is turned on (S34). This adjustment is performed with the light source 31 turned off and the light source 41 turned on. Note that the light amount adjustment process of the light source 41 when only the light source 41 is turned on is basically the same process as the light amount adjustment process of the light source 31 when only the light source 31 is turned on, and redundant description is omitted. With this adjustment, the lighting time T2 of the light source 41 when only the light source 41 is turned on is stored in the RAM 13.

  Next, CPU11 adjusts the light quantity of the light source 31 in the simultaneous lighting of the light source 31 and the light source 41 (S32). This adjustment is performed in a state where the light source 31 and the light source 41 are turned on at the same time, that is, in a state where the light source 31 and the light source 41 are turned on for the same lighting time T. A lighting time T3 is determined.

  As shown in FIG. 8, in the light amount adjustment process, the CPU 11 first sets the lighting time T of the light sources 31, 41 to the maximum time Tmax (S52). The CPU 11 turns on the light source 31 and the light source 41 for the set lighting time T, reads one line of the white reference plate 43 using each light receiving element of the light receiving unit 32, and acquires white reference data for each light receiving element (S54). ). The CPU 11 converts the acquired white reference data into a gradation value by the AFE 16, and compares the maximum gradation value WKmax with the maximum gradation value Kmax (S56).

  When the maximum gradation value WKmax of the white reference gradation data is equal to or greater than the maximum gradation value Kmax of the AFE 16 (YES in S56), the CPU 11 shortens the lighting time T by the reference time KT (S58), and the processing from S54 repeat. On the other hand, when the maximum gradation value WKmax of the white reference gradation data is smaller than the maximum gradation value Kmax of the AFE 16 (NO in S56), the CPU 11 sets the lighting time T to the light source 31 in simultaneous lighting of the light source 31 and the light source 41. Is stored in the RAM 13 as the lighting time T3 (S60), and the process ends.

  Next, CPU11 adjusts the light quantity of the light source 41 in the simultaneous lighting of the light source 31 and the light source 41 (S38). This adjustment is performed in a state where the light source 31 and the light source 41 are turned on simultaneously, that is, in a state where the light source 31 and the light source 41 are turned on with the same lighting time T. Note that the light amount adjustment process of the light source 41 when the light source 31 and the light source 41 are turned on simultaneously is basically the same process as the light amount adjustment process of the light source 31 when the light source 31 and the light source 41 are turned on simultaneously, and redundant description is omitted. With this adjustment, the lighting time T4 of the light source 41 when the light source 31 and the light source 41 are turned on simultaneously is stored in the RAM 13. In addition, the adjustment at the time of simultaneous lighting of the light source is adjusted to the light amount at the time of actual reading by performing readjustment after each T3 and T4 is determined.

  When the light amount adjustment processing of the light sources 31 and 41 is completed, the CPU 11 drives the transport unit 28 using the drive circuit 17 and starts transporting the document G placed on the paper feed tray 2 (S4). After starting the conveyance of the document G, the CPU 11 confirms the position of the document G conveyed on the conveyance path 22 using the rear sensor 27, and waits for the leading end in the conveyance direction of the document G to reach the position P1 (in S6). NO).

  As shown in FIG. 3, the CPU 11 turns on the light sources 31 and 41 when the leading end of the document G in the conveyance direction reaches the position P1 (YES in S6). As shown in FIG. 11, when turning on the light sources 31 and 41, the CPU 11 repeatedly turns on and off in one line cycle TS. When the leading end of the document G in the conveyance direction reaches the position P1, the CPU 11 causes the light source 31 and the light source 41 to emit light over the lighting time T3 in one line cycle TS.

  As shown in FIG. 9, the CPU 11 starts reading the document G by the CIS 30 when the leading end of the document G in the transport direction reaches the position P2 and the document G transported through the transport path 22 is in the first state Z1. . Whether or not the leading end of the document G in the transport direction has reached the position P2 depends on the transport speed of the document G transported on the transport path 22 after the leading end of the transport direction of the document G has reached the position P1, and the transport. This is determined by whether or not the conveyance time determined by the distance between the position P1 and the position P2 in the path 22 has elapsed. The same applies when the leading edge of the document G in the conveyance direction reaches the position P3, and the same applies when the trailing edge of the document G in the conveyance direction reaches the position P1 and then reaches the positions P2 and P3.

  Further, the CPU 11 waits for the leading end of the document G in the conveyance direction to reach the position P3 (NO in S10). As shown in FIG. 10, the CPU 11 reaches the position P3 in the transport direction of the document G (YES in S10), and the document G transported along the transport path 22 is cut from the first state Z1 to the second state Z2. In other words, the lighting time T of the light sources 31 and 41 is changed. In the second state Z2, the CPU 11 causes the light source 31 to emit light over the lighting time T1, and causes the light source 41 to emit light over the lighting time T2 (S12). Further, the CPU 11 starts reading the document G by the CIS 40.

  The CPU 11 reads both sides of the document G using the CISs 30 and 40 in the second state Z2. Further, the CPU 11 waits for the trailing end of the document G in the conveyance direction to reach the position P2 (NO in S14). When the rear end of the document G in the transport direction reaches the position P2 (YES in S14) and the document G transported on the transport path 22 is switched from the second state Z2 to the first state Z1 again, the light source 31 , 41 is changed. In the first state Z1, the CPU 11 causes the light source 31 and the light source 41 to emit light over the lighting time T4 (S16). Further, the CPU 11 ends the reading of the original G by the CIS 30.

  Next, the CPU 11 waits for the trailing end of the document G in the conveyance direction to reach the position P3 (NO in S18). When the trailing end of the document G in the conveyance direction reaches the position P3 (YES in S18), the CPU 11 turns off the light sources 31 and 41 (S20). Further, the CPU 11 ends the reading of the original G by the CIS 40 and ends the reading of the original G by the reading unit 24. After discharging the original G to the paper discharge tray 4, the CPU 11 stops the conveyance unit 28 using the drive circuit 17 (S22) and ends the reading process.

4). Advantages of the present embodiment (1) In the image reading apparatus 1 of the present embodiment, the CIS 30 and the CIS 40 are provided at positions shifted from each other across the conveyance path 22, and the position P 2 where the CIS 30 reads a document and the CIS 40 are The document reading position P3 is set at a different position on the conveyance path 22. Therefore, when the CIS 30 reads the original G at the position P2, that is, when the original G exists at the position P2, the first state Z1 where the original G does not exist at the position P3 and the second state where the original G exists at the position P3. Two states of Z2 can occur.

  In the second state Z2 where the document G exists at the position P3, the light emitted from the light source 41 is blocked by the document G. On the other hand, in the first state Z1 where the document G does not exist at the position P3, the light emitted from the light source 41 is not blocked by the document G, and a part of the light emitted from the light source 41 is received by the light receiving unit 32 of the CIS 30. Is done. Therefore, if the amount of light emitted from the light source 31 is the same in the first state Z1 and the second state Z2, the amount of light received by the light receiving unit 32 in the first state Z1 is received by the light receiving unit 32 in the second state Z2. The amount of light that is read by the CIS 30 varies depending on the switching between the first state Z1 and the second state Z2.

  FIG. 11 shows a comparison of lighting times T of the light sources 31 and 41 in the first state Z1 and the second state Z2 of the image reading apparatus 1. In the present embodiment, the lighting state T3 of the light source 31 when the light source 31 and the light source 41 are simultaneously turned on in the first state Z1 is the lighting state of the light source 31 when the light source 31 is turned on only in the second state Z2. It adjusts so that it may become shorter than time T1. That is, the light amount irradiated from the light source 31 in the first state Z1 is adjusted to be smaller than the light amount irradiated from the light source 31 in the second state Z2. Similarly, the amount of light emitted from the light source 41 in the first state Z1 is adjusted to be smaller than the amount of light emitted from the light source 41 in the second state Z2. Accordingly, it is possible to suppress a difference in the amount of light received by the light receiving units 32 and 42 in the first state and the second state, and it is possible to suppress occurrence of unevenness in the read data.

(2) In the image reading apparatus 1 of the present embodiment, the lighting time T3 of the light source 31 in the first state Z1 is adjusted in a state where the light sources 31 and 41 are simultaneously turned on, and the lighting time of the light source 31 in the second state Z2 is adjusted. T1 is adjusted with the light source 31 turned on and the light source 41 turned off. That is, in the image reading apparatus 1, in the first state Z1, since the light emitted from the light sources 31, 41 is received by the light receiving units 32, 42, the first light source and the second light source are turned on at the same time for adjustment. To do. In the second state Z2, the light emitted from the light source 41 is not received by the light receiving unit 32, and the light emitted from the light source 31 is not received by the light receiving unit 42. Therefore, the first light source and the second light source are separated. Turn on to adjust. Therefore, it is possible to adjust the light amounts of the light sources 31 and 41 in each state in consideration of the light irradiation state according to the state of the document G being transported through the transport path 22.

<Embodiment 2>
A second embodiment will be described with reference to FIG. In the present embodiment, the light amount adjustment processing for the lighting time T of the light sources 31 and 41 in the first state Z1 is different from that in the first embodiment. In the following description, the same description as that of the first embodiment will not be repeated.

1. Light quantity adjustment process As shown in FIG. 12, in the light quantity adjustment process of the light source 31 in the first state Z1, the CPU 11 sets the lighting time T of the light sources 31 and 41 to the maximum time Tmax (S52). White reference data is acquired using each light receiving element (S54). The CPU 11 converts the acquired white reference data into a gradation value by the AFE 15, and compares the average gradation value WKave obtained by averaging the gradation values of the respective light receiving elements with the maximum gradation value Kmax (S62).

  When the average gradation value WKave of the white reference gradation data is equal to or greater than the maximum gradation value Kmax of the AFE 16 (YES in S62), the CPU 11 shortens the lighting time T by the reference time KT (S58), and the processing from S54 repeat. On the other hand, when the average gradation value WKave of the white reference gradation data is smaller than the maximum gradation value Kmax of the AFE 15 (NO in S62), the CPU 11 sets the lighting time T to the lighting time T3 of the light source 31 in the first state Z1. Is stored in the RAM 13 (S60), and the process ends. The adjustment of the lighting time T4 of the light source 41 in the first state Z1 is the same. Further, the average gradation value WKave of the white reference gradation data does not necessarily have to be performed for all data.

2. Effects of the present embodiment In the image reading apparatus 1 of the present embodiment, the amount of light emitted from the light sources 31 and 41 in the first state Z1 is based on the average value of the amount of light received by the light receiving elements of the light receiving units 32 and 42. Adjust. According to this image reading apparatus, the average value of the amount of light received by the light receiving element when the document G is read is taken into consideration while considering the influence of light emitted from the CIS light source disposed on the opposite side of the conveyance path 22. Overflow in each of the light receiving parts 32 and 42 can be suppressed.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and the drawings, and for example, the following various aspects are also included in the technical scope of the present invention.
(1) Although the above embodiment has been described using the image reading apparatus 1, the present invention is not limited to this. It may be a multi-function machine having an image reading function for reading the original G and having at least one function such as a printer function, a scanner function, a copy function, and a facsimile function.

(2) In the above embodiment, the pair of CISs 30 and 40 of the reading unit 24 are provided at positions shifted from each other with the conveyance path 22 interposed therebetween. However, the pair of CISs 30 and 40 may be disposed at positions facing each other in the transport direction of the transport path 22. For example, in the CIS 30, when the light receiving unit 32 is disposed on the upstream side of the light source 31, and in the CIS 40, the pair of CISs 30 and 40 are arranged on the conveyance path 22 when the light receiving unit 42 is disposed on the downstream side of the light source 41. Even if they are arranged at opposite positions in the transport direction, the position P2 where the CIS 30 reads the original and the position P3 where the CIS 40 reads the original can be set at different positions on the transport path 22. By disposing the CISs 30 and 40 in this way, the reading unit 24 can be reduced in size.

(3) In the above-described embodiment, the ASIC 10 includes one CPU 11 and the image reading process is executed by the one CPU 11. However, the image reading process may be executed by a plurality of CPUs 11. For example, the configuration may be such that device control processing, image processing, and driving processing are executed by different CPUs 11.

(4) In the above embodiment, the transmission member placed on the conveyance path 22 side of the CIS 30 or 40 has been described using the platen glass 34 or 44, but the material is not particularly limited, and the transmittance is relatively high. High plastics may be used.

(5) In the above embodiment, the reading unit 24 has been described using an example in which the reading unit 24 includes a pair of CISs 30 and 40. However, the CISs 30 and 40 are examples of reading devices that constitute the reading unit 24. The reading device may include a CCD (Charge Coupled Drive Image Sensor).

1: image reading apparatus, 10: ASIC, 11: CPU, 15: device control unit, 16: AFE, 17: drive circuit, 22: transport path, 24: reading unit, 28: transport unit, 30, 40: CIS, 31, 41: Light source, 32, 42: Light receiving unit, 33, 43: White reference plate, 34, 44: Platen glass, 50: Light source control unit, G: Document, T: Lighting time, Z1: First state, Z2 : Second state

Claims (4)

A transport unit that transports a document along a transport path;
A first light source installed on one side along the conveyance path and irradiating light on one side of the document and light reflected on one side of the document are received and a read image signal is received. A first reading unit having a first light receiving element for outputting;
A second light source that is positioned on the downstream side of the transport path from the first reading unit, is disposed on the other side along the transport path, and irradiates light to the other surface of the document; and the document A second light receiving element that receives the light reflected by the other surface of the first light receiving element and outputs a read image signal;
With
At least one of the first light receiving element and the second light receiving element is disposed at a position that is affected by light emitted from another light source,
Furthermore,
When reading both sides of the document, both the first light source and the second light source are turned on, and at least one of the leading edge and the trailing edge of the document in the direction along the conveyance path is the first reading unit and the second reading unit. In the first state existing between the second reading unit and the second reading unit, the leading end of the document is positioned downstream of the second reading unit, and the trailing end of the document is positioned upstream of the first reading unit. A light source control unit that controls the first light source and the second light source so as to reduce the amount of light emitted from the first light source and the second light source,
An image reading apparatus comprising: The image reading apparatus according to claim 1,
The amount of light emitted from the first light source and the second light source in the first state causes the first light source and the second light source to be turned on simultaneously with respect to the white member disposed at a position facing each light receiving element. The light intensity adjusted
The amount of light emitted from the first light source and the second light source in the second state lights the first light source and the second light source separately with respect to a white member disposed at a position facing each light receiving element. An image reading apparatus having a light amount adjusted in such a manner. The image reading apparatus according to claim 2,
Each of the first light receiving element and the second light receiving element has a maximum light receiving amount and has a plurality of reading elements, and receives the light reflected by the white member using each reading element. And
In each state, the amount of light emitted from the first light source and the second light source is adjusted to the largest amount of light in the range where the maximum value of the light receiving amount of the reading element in each light receiving element does not exceed the maximum light receiving amount. Image reading apparatus. The image reading apparatus according to claim 2,
Each of the first light receiving element and the second light receiving element has a maximum light receiving amount and has a plurality of reading elements, and receives light reflected by the original using each reading element. ,
The amount of light emitted from the first light source and the second light source in the first state is a range in which an average value of the light receiving amount of the reading element in the first light receiving element and the second light receiving element does not exceed the maximum light receiving amount. The image reading apparatus is adjusted to have the largest light quantity.

Images