JP5230382B2 - Image reading apparatus and document size detection method thereof - Google Patents

Description

  The present invention relates to an image reading apparatus that irradiates a document with light using a light source and reads the image from reflected light of the document, and a method for detecting the document size.

  Conventionally, when performing main scanning size detection of an original in an image reading apparatus, there is a method of providing a dedicated main scanning size detection sensor. In this method, an original placed on the platen glass is irradiated with infrared rays from an LED light source from below the platen glass, and the reflected light is read to determine whether the main scanning size of the original is a large size or a small size. Is detected.

  FIG. 15 is a cross-sectional view showing a configuration of a conventional image reading apparatus. The image reading apparatus 500 includes an image reading unit 510 and a pressure plate 508. The image reading unit 510 includes an optical unit frame (not shown) and a frame 515 that supports an original table glass 522 on which an original is mounted. The frame 515 is housed in a photoelectric conversion element 521 made of CCD or CMOS, a lens 520 for condensing light from the document table onto the photoelectric conversion element 521, and an optical unit frame (not shown). An LED light source 516 that illuminates the original on the table is provided. Further, inside the frame body 515, folding mirrors 517, 518, and 519 are provided which are housed in an optical unit frame body (not shown) and guide reflected light from the original to the photoelectric conversion element. A main scanning size detection sensor 501 is provided at the bottom of the frame 515.

  On the other hand, the pressure plate 508 has a surface of a white member for pressing the document so that the document 530 does not float and for creating a background of a portion without the document. The image reading unit 510 reads an image of an original by moving an optical unit frame that supports the LED light source 516 and the folding mirrors 517, 518, and 519 along the original 530 mounted on the original platen glass 522.

  In addition, a technique using a photoelectric conversion element (CCD sensor or CMOS sensor) provided for image reading instead of a dedicated sensor for detecting the main scanning size of the document such as the main scanning size detection sensor 501 is also known. (See Patent Document 1). In this case, the main scanning size of the document is detected by emitting light from a light source provided for irradiating the document and reading the reflected light from the document.

  The timing for reading the main scanning size of the document is the photoelectric conversion element (CCD sensor or CMOS sensor) provided for image reading described below even when the above-described dedicated sensor for detecting the main scanning size of the document is used. The same is true for any use of. That is, this timing is when the user pushes up the pressure plate for pressing the document placed on the image reading apparatus and sets the document on the platen glass.

  As a detection method for setting a document on the platen glass, when the pressure plate is pushed up to some extent, the sensor detects the opening, and the image reading apparatus determines that the user is setting the document. Next, when the user tries to push down the pressure plate, the sensor detects this, and at this time, the image reading apparatus performs an operation of detecting the main scanning size of the document.

The reason for performing the detection operation at such a timing is that the pressure plate for pressing the document is made of a white member so that the non-document portion is not colored. This is because it becomes difficult to distinguish borders. In other words, during the closing of the platen, the main scanning size of the document is reduced by creating a situation where reflected light that is reflected by the document returns and a portion that does not return reflected light when there is no document. It can be read.
JP 2001-346209 A

  However, the conventional image reading apparatus has the following problems. First, when a dedicated sensor is used for detecting the main scanning size of the document, the cost is naturally increased. Further, by providing a dedicated sensor, it is necessary to secure a space for mounting the sensor, and the size of the image reading apparatus cannot be reduced. In FIG. 15, the main scanning size detection sensor 501 described above is provided at the bottom of the frame 515 of the image reading apparatus 500.

  Further, when a photoelectric conversion element (CCD sensor or CMOS sensor) provided for image reading is used, a dedicated sensor for detecting the main scanning size of the document is not used, which is advantageous in terms of cost and space. However, since the main scanning size of the document is detected in a state where the pressure plate is open, a new problem arises that light from the light source is dazzling for the user.

  In a conventional image reading apparatus, a light source such as a halogen tube, a xenon tube, or a fluorescent lamp has been used as a light source with little variation in light quantity in the main scanning direction. However, as a feature of these light sources, the responsiveness when changing the light amount is not good, and conventionally, it has been impossible to perform control for detecting the main scanning size of the document by changing the light amount of the light source. Even if the amount of light can be reduced and the original size can be read, there are cases where the original size cannot be read well due to the influence of the original color, reflectance, and external light.

  In particular, when an LED is used as a light source of an original reading apparatus, a point light source such as an LED is not a light source that shines uniformly in the main scanning direction as in the conventional case, but the individual light emitting points of the LED shine very brightly. Cause unpleasantness.

SUMMARY An advantage of some aspects of the invention is that it provides an image reading apparatus and a method for detecting the size of a document that can suppress glare of a user while suppressing a decrease in accuracy of document size detection.

To achieve the above object, an image reading apparatus of the present invention is an image reading apparatus for reading an image of a document, and the pressure plate for pressing a document table the document is placed, a document placed on the document table A light source for irradiating the original with light, a reading means for generating image data according to the incident light, an open / close detecting means for detecting the degree of opening / closing of the pressure plate, and opening / closing of the pressure plate detected by the open / close detection means An adjustment unit that adjusts an initial value of the amount of light emitted by the light source according to the degree, and an image that is generated by the reading unit when the light source is irradiating a document according to the amount of light adjusted by the adjustment unit. based on the data, and a size detecting means for detecting the size of the document placed on the document table, Do not detect the size of a document placed on the platen by said size detecting means In this case, the adjusting unit increases the adjusted light amount, and the size detecting unit is based on the image data generated by the reading unit in the light irradiation from the light source according to the light amount increased by the adjusting unit. The size of the document placed on the document table is detected, and the increase in the amount of light by the adjustment unit and the size until the increase in the amount of light by the adjustment unit reaches a predetermined value or until the size of the document can be detected. It is characterized by repeating the detection of the detection means .

The document size detection method of the present invention includes a document table on which a document is placed, a pressure plate that holds the document placed on the document table, a light source that irradiates light on the document, and an image corresponding to incident light. and a reading means for generating data, in the document size detection method for an image reading apparatus for reading an image of the document, and the opening and closing detecting step of detecting the opening and closing degree of the pressure plate, the opening and closing of the pressure plate that is detected by the opening detection step An adjustment step for adjusting an initial value of the amount of light emitted by the light source according to the degree, and an image generated by the reading unit when the light source is irradiating a document according to the amount of light adjusted in the adjustment step based on the data, and a size detecting step for detecting the size of the document placed on the document table, the size of the document the placed on the platen in size detection step If not detected, the adjusted light amount is increased in the adjusting step, and the size detecting step is image data generated by the reading unit in the light irradiation from the light source according to the light amount increased in the adjusting step. Based on the increase in the amount of light by the adjustment step until the size of the document placed on the document table is detected and the increase in the amount of light by the adjustment step reaches a predetermined value or until the size of the document can be detected. The detection by the size detection step is repeated .

According to the present invention, the amount of light is changed according to the degree of opening and closing of the pressure plate, and the amount of light is increased until the amount of light reaches a predetermined value or the size of the document can be detected. On the other hand, it is possible to suppress the glare of the user when detecting the document size .

  Embodiments of an image reading apparatus and a document size detection method according to the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a cross-sectional view illustrating the configuration of the image reading apparatus according to the first embodiment. The image reading apparatus 10 includes an image reading unit 110 and a pressure plate 108. The image reading unit 110 includes an optical unit frame (not shown) and a frame 115 that supports an original table glass 122 on which an original is mounted.

  Inside the frame 115 is housed in a photoelectric conversion element 121 made of CCD or CMOS, a lens 120 for condensing light from the document table onto the photoelectric conversion element 121, and an optical unit frame (not shown), and a document An LED light source 116 for illuminating the original on the table is provided. Further, inside the frame body 115, folding mirrors 117, 118, and 119 are provided which are housed in an optical unit frame body (not shown) and guide reflected light from the original to the photoelectric conversion element.

  Further, the pressure plate 108 has a white member surface for holding the original so that the original 100 does not float and for creating a background of a portion where there is no original. As will be described later, a pressure plate opening / closing lever 130 (see FIG. 4) that supports the rotation is attached to the pressure plate 108, and fins 131 (see FIG. 4) are attached to the end portions thereof. .

  The image reading unit 110 reads an image of a document by moving an optical unit frame that houses the LED light source 116 and the folding mirrors 117, 118, and 119 along the document 100 mounted on the document table glass 122.

  FIG. 2 is a diagram showing a layout of LED chips in the LED light source 116. The LED light source 116 includes two LED arrays 116A and 116B. In each of the LED arrays 116A and 116B, a plurality of LED chips 116c and 116d are arranged in an array. The plurality of LED chips 116c and 116d are roughly mounted at the center of each LED array 116A and 116B and densely mounted at the ends thereof. This is because the amount of light at the end of the LED array is reduced by the lens 120 when it reaches the photoelectric conversion element 121, so that the LED chips are densely mounted at the end of the LED array as shown in FIG. This is because the amount of light on the photoelectric conversion element 121 becomes uniform.

  FIG. 3 is a diagram showing the position of the original when the original 100 is placed on the original table glass 122. A main scanning direction size guide plate 133 and a sub-scanning direction size guide plate 132 are provided on the left side and the upper side of the document table glass 122 in the drawing, respectively. The user places the document 100 on the platen glass 122 with the main scanning direction size guide plate 133 and the sub-scanning direction size guide plate 132 as marks. In FIG. 3, a B5 size document is arranged.

  FIG. 4 is a diagram illustrating a state in which the LED light source 116 emits light when the pressure plate 108 is opened, the light is reflected by the original 100, and the light from the LED light source 116 passes through a portion where the original 100 does not exist. is there. The light reflected by the document 100 is detected by the photoelectric conversion element 121. On the other hand, assuming that the area where the light does not reflect on the photoelectric conversion element 121 is an area where there is no document, the main scanning size of the document is detected by reading the boundary.

  When the user opens the pressure plate 108 to place the original 100 on the platen glass 122, the pressure plate opening / closing lever 130 attached to the pressure plate 108 and the fins 131 attached thereto are interlocked with the opening / closing of the pressure plate 108. At this time, the pressure plate opening / closing angle and its opening / closing angle are detected by the four pressure plate opening / closing angle detection sensors 200a, 200b, 200c, 200d (open / close detection means).

  FIG. 5 is a perspective view showing an appearance of a photo interrupter used as four pressure plate opening / closing angle detection sensors 200a, 200b, 200c, and 200d. The four pressure plate opening / closing angle detection sensors 200a, 200b, 200c, and 200d have the same structure, and are referred to as a pressure plate opening / closing angle detection sensor 200 when it is not particularly necessary to distinguish them. The photo interrupter constituting the pressure plate opening / closing angle detection sensor 200 is well known, and outputs a different signal depending on whether or not the fin 131 is positioned in the gap.

  When the pressure plate 108 is completely closed, the pressure plate opening / closing angle detection sensor 200a detects that the light of the photo interrupter is blocked by the fins 131. When the user tries to push up the pressure plate 108 from this state, the fin 131 located on the pressure plate opening / closing angle detection sensor 200a is removed, and the pressure plate opening / closing angle detection sensor 200a detects this. Thereby, it is detected that the pressure plate is opened.

  When the image reading apparatus 10 detects that the pressure plate 108 is opened, it waits until it detects that the pressure plate 108 is next closed. In FIG. 4, the pressure plate opening / closing angle detection sensor 200b is arranged so as to detect that the pressure plate 108 is opened 30 °. Further, the pressure plate opening / closing angle detection sensor 200c is arranged so as to detect that the pressure plate 108 is opened by 45 °, and the pressure plate opening / closing angle detection sensor 200d is arranged so as to detect that the pressure plate 108 is opened by 70 °. Yes.

  As shown in FIG. 4, when the fin 131 is stopped at the pressure plate opening / closing angle detection sensor 200c, it is detected that the pressure plate is opened by 45 °. If the pressure plate 108 is to be closed from this position, the pressure plate opening / closing angle detection sensor 200c shifts to a state where the fin 131 is not detected. By detecting this state, it is detected that the pressure plate 108 is about to be closed from the 45 ° open state.

  Here, as apparent from FIG. 4, the area where there is no document and the light passes is the closest part to the user, so the user feels very dazzling. In particular, the LED light source 116 is a light source in which LED chips, which are point light sources, are arranged in an array, and as shown in FIG. 2, the LED chips 116c and 116d are densely arranged in an area without a document. The user will feel increasingly dazzling.

  FIG. 6 is a block diagram showing the configuration of the control unit of the image reading apparatus 10. The control unit controls the light amount of the LED according to the control unit (CPU) 600, the pressure plate opening / closing angle detection sensor 200, the photoelectric conversion element 121 that receives reflected light from the document, the memory 602, the LED light source 116, and the light amount setting value. LED dimming circuit 700. The memory 602 stores a light amount setting value of the LED light source 116 according to the opening / closing angle of the pressure plate opening / closing angle detection sensor 200 when the document size is detected.

  The control unit (CPU) 600 detects the opening / closing state of the pressure plate and the opening / closing angle of the pressure plate from the pressure plate opening / closing angle detection sensor 200. In addition, the CPU 600 reads the light amount setting value of the LED light source according to the opening / closing angle of the pressure plate from the memory 602. The CPU 600 drives the LED dimming circuit 700 using the light amount setting value, and turns on the LED light source 116. When the photoelectric conversion element 121 reads (detects) the reflected light from the original on the original platen glass irradiated by turning on the LED light source 116, the CPU 600 detects the main scanning size of the original.

  FIG. 7 is a diagram showing a circuit configuration of the LED light source 116 and the LED dimming circuit 700. FIG. 7 also shows the CPU 600, the memory 602, and the pressure plate opening / closing angle detection sensor 200. The LED dimming circuit 700 mainly includes a D / A converter 601, an operational amplifier OP1, a transistor Tr1, and a resistor R1.

  As described above, the control unit (CPU) 600 detects the pressure plate opening / closing state and the pressure plate opening / closing angle from the pressure plate opening / closing angle detection sensor 200. The CPU 600 reads the light amount setting value of the LED light source according to the opening / closing angle of the pressure plate from the memory 602. The CPU 600 sets the LED light amount setting value in the D / A converter 601 of the LED dimming circuit 700 using the light amount setting value. The D / A converter 601 converts the set digital value into an analog output. Then, the current of the transistor Tr1 is controlled via the operational amplifier OP1. At this time, the analog signal converted by the D / A converter 601 is used as the reference voltage of the operational amplifier OP1. The operational amplifier OP1 drives the transistor Tr1 so that a desired current flows through the resistor R1 while detecting the current flowing through the resistor R1, and the current flowing through the LED chips 116c and 116d (LED1 to LEDn), that is, the light amount of the LED light source 116. To control.

  FIG. 8 is a graph showing the light amount setting value of the LED light source 116 according to the opening / closing angle of the pressure plate when the document size is detected. As described above, the light amount setting value of the LED light source 116 corresponding to the opening / closing angle of the pressure plate is stored in the memory 602.

  In this graph, when the pressure plate is closed or when the LED light amount when reading the image data of the document is set to 100%, the larger the pressure plate opening / closing angle, the lower the LED light amount and the main scanning size of the document is detected. Is done. That is, when the pressure plate opening / closing angles are 0 °, 30 °, 45 °, and 70 °, the LED light amounts are set to 100%, 80%, 70%, and 60%, respectively. As described above, when the opening / closing angle of the pressure plate increases, the influence of the LED light source entering the user's eyes also increases. Therefore, the control is performed so that the LED light quantity decreases as the opening / closing angle increases.

  FIG. 9 is a flowchart showing the main scanning size detection processing procedure of the document. This processing program is stored in the memory 602 and executed by the CPU 600. First, the CPU 600 detects that the pressure plate 108 has been opened by the pressure plate opening / closing angle detection sensor 200 (step S1). Further, the CPU 600 detects the angle at which the pressure plate 108 is opened (step S2).

  The CPU 600 reads the light amount setting value of the LED light source according to the opening / closing angle of the pressure plate when the document size is detected from the memory 602 (step S3). The process of step S3 is an example of a setting value acquisition unit that acquires a light amount setting value. CPU 600 detects the movement of pressure plate 108 being closed (step S4).

  The CPU 600 turns on the LED light source with the light amount setting value read from the memory 602 in step S3 (step S5). The process in step S5 is an example of a light amount adjusting unit. The CPU 600 detects the light reflected from the document and detects the main scanning size of the document (step S6). Then, the CPU 600 turns off the LED light source 116 when it detects the main scanning size of the document (step S7). Thereafter, the CPU 600 ends this process.

  The image reading apparatus according to the first embodiment reads the main scanning size of the document while irradiating the document with light with a light amount corresponding to the opening / closing angle of the pressure plate stored in advance in the memory. Therefore, when an LED is used as a light source, main scanning size detection can be performed with a light amount that is not dazzling when the platen is opened and closed. Further, by using an LED as the light source of the document, it is possible to improve the responsiveness to the light amount change. In this way, it is possible to reduce glare by using the LED as a light source, and to detect the main scanning size with a light amount that is not dazzling. Further, by storing the light amount setting value in the memory, the light amount can be easily and quickly adjusted.

[Second Embodiment]
FIG. 10 is a block diagram illustrating a configuration of a control unit of the image reading apparatus according to the second embodiment. Unlike the first embodiment, the image reading apparatus according to the second embodiment includes two storage areas including a first memory 602a (first storage unit) and a second memory 602b (second storage unit). Have In addition, the same code | symbol is used about the component same as the said 1st Embodiment.

  The control unit controls the light amount of the LED according to the control unit (CPU) 600, the pressure plate opening / closing angle detection sensor 200, the photoelectric conversion element 121, the first memory 602a, the second memory 602b, the LED light source 116, and the light amount setting value. An LED dimming circuit 700 is included. The photoelectric conversion element 121 receives reflected light from the document.

  The first memory 602a stores an initial light amount setting value of the LED light source 116 corresponding to the flat plate opening angle detected by the pressure plate opening / closing angle detection sensor 200 when the document size is detected. Further, the second memory 602b stores a light amount step-up amount indicating how many steps the light amount is increased from the initial light amount stored in the first memory 602a.

  The LED dimming circuit 700 turns on the LED light source 116 according to the initial light amount setting value stored in the first memory 602a, and when the main scanning size of the document cannot be detected after a predetermined time has elapsed, the second memory 602b. The light quantity is controlled to increase by the light quantity step-up stored in.

  The control unit (CPU) 600 detects the opening / closing state of the pressure plate and the opening / closing angle of the pressure plate from the pressure plate opening / closing angle detection sensor 200. Further, the CPU 600 reads the initial light amount setting value of the LED light source according to the opening / closing angle of the pressure plate from the first memory 602a. The CPU 600 drives the LED dimming circuit 700 using the light amount setting value, and turns on the LED light source 116. When the photoelectric conversion element 121 reads (detects) the reflected light of the document on the platen glass irradiated by turning on the LED light source 116, the CPU 600 detects the main scanning size of the document.

  As described above, the main scanning size of the document is detected, but when the photoelectric conversion element 121 reads the reflected light of the document, the amount of light is low depending on the color and reflectance of the document, and thus the CPU 600 cannot detect the document well. There is.

  If the main scanning size of the document cannot be detected, the CPU 600 increases the light amount with respect to the initial light amount setting value of the first memory 602a by the light amount step-up stored next in the second memory 602b, and the LED dimming circuit. 700 is driven, and the LED light source 116 is turned on. The CPU 600 repeats this light quantity increase up to a predetermined maximum light quantity (MAX) value over time, and detects the main scanning size of the document.

  FIG. 11 is a flowchart showing the main scanning size detection processing procedure of the document. This processing program is stored in the first memory 602 a and executed by the CPU 600. About the same step process as the said 1st Embodiment, the description is abbreviate | omitted by attaching | subjecting the same step number.

  When the opening / closing angle of the pressure plate is detected in step S2, the CPU 600 reads an initial light amount setting value corresponding to the opening / closing angle from the first memory 602a (step S3A). The CPU 600 turns on the LED light source 116 with the initial light amount setting value read from the first memory 602a in step S5, and then determines whether or not the main scanning size of the document has been detected (step S6A).

  If the main scanning size of the document can be detected, the CPU 600 turns off the LED light source 116 in step S7. On the other hand, when the main scanning size of the document cannot be detected, the CPU 600 adds the light amount step-up (light amount increase value) stored in the second memory 602b, and the light amount with respect to the initial light amount of the first memory 602a. Increase (step S6B). The process of step S6B is an example of an increase value acquisition unit that acquires the light amount increase value.

  The CPU 600 repeatedly performs this light quantity increase, and determines whether or not the LED light quantity exceeds the maximum light quantity (MAX) value (step S6C). If the maximum light amount (MAX) value has been exceeded, the CPU 600 proceeds to the process of step S7. If not, the process returns to step S6A.

  FIG. 12 is a timing chart showing the change in the set value of the LED light amount according to the pressure plate opening / closing angle when the pressure plate opening / closing angle is 30 °. The initial light intensity setting value of the first memory 602a is 60%. The light amount setting value is a value at which the 5% spectral amount increases stepwise with the passage of the document detection time t (T1 to T5). If the main scanning size of the original is not detected even after irradiation for T1 time with the initial light amount setting value, the CPU 600 next increases the 5% spectral amount that is the light amount step-up set in the second memory 602b to 65%. The amount of light. Then, the CPU 600 again irradiates the document size with this light amount for T2 time, and tries to detect whether or not the main scanning size of the document can be detected.

  When this operation is repeated and the maximum light amount set to the upper limit value of 80% is reached, the CPU 600 determines that the main scanning size of the original cannot be detected even if it is irradiated further, and the main scanning size detection processing of the original is terminated. To do. The upper limit value of 80% is set to the same value as the light amount setting value corresponding to the pressure plate opening / closing angle of 30 ° in the first embodiment as an example only, but the upper limit value can be arbitrarily set. is there.

  FIG. 13 is a timing chart showing the change in the set value of the LED light amount according to the pressure plate opening / closing angle when the pressure plate opening / closing angle is 45 °. In this case, the initial light amount setting value of the first memory 602a is 50%. The light amount setting value is a value at which the 5% spectral amount increases stepwise with the passage of the document detection time t (T1 to T7). If the main scanning size of the original is not detected even after irradiation for T1 time with the initial light amount setting value, the CPU 600 next increases the 5% spectral amount that is the light amount step-up set in the second memory 602b to 55%. The amount of light. Then, the CPU 600 again irradiates the document size with this light amount for T2 time, and tries to detect whether or not the main scanning size of the document can be detected.

  FIG. 14 is a timing chart showing the change in the set value of the LED light amount in accordance with the pressure plate opening / closing angle when the pressure plate opening / closing angle is 70 °. In this case, the initial light amount setting value of the first memory 602a is 40%. The light amount setting value is a value at which the 5% spectral amount increases stepwise as the document detection time t elapses (T1 to T9). If the main scanning size of the original is not detected even after irradiation for T1 time with the initial light amount setting value, the CPU 600 next increases the 5% spectral amount that is the light amount step-up set in the second memory 602b to 45%. The amount of light. Then, the CPU 600 again irradiates the document size with this light amount for T2 time, and tries to detect whether or not the main scanning size of the document can be detected.

  As described above, the image forming apparatus according to the second embodiment controls the light amount of the LED light source according to the opening / closing angle of the pressure plate when the main scanning size of the document is detected. Accordingly, it is possible to detect the main scanning size of the document without giving the user the unpleasant feeling of dazzling. Further, since the original size is read with the pressure plate opened and closed, there are cases where the original size cannot be read due to the influence of the color, reflectance, and external light of the original. Even in such a case, the main scanning size of the document can be detected reliably and without dazzling even if the LED is used as the light source by gradually increasing the light amount of the LED light source according to the opening / closing angle of the pressure plate. It becomes possible to do. In other words, by increasing the light amount of the preset light source over time according to the opening / closing angle of the pressure plate, the light amount can be gradually increased without a sense of incongruity for the user. Can be detected.

  Further, by storing the initial light amount setting value and the light amount step-up amount in the memory, the light amount can be easily and quickly adjusted.

  The present invention is not limited to the configuration of the above-described embodiment, and any configuration can be used as long as the functions shown in the claims or the functions of the configuration of the present embodiment can be achieved. Is also applicable.

  For example, in the above embodiment, the case where the main scanning size of the document is detected has been described. However, the present invention can be similarly applied to the case where the sub scanning size of the document is detected or both of them are detected. is there. When both are detected, an irregular size can be detected.

  In the above embodiment, the pressure plate opening / closing angle detection sensor accurately obtains the opening / closing angle of the pressure plate, and the light amount setting value corresponding to the angle is set in four stages. The method is not limited. For example, the opening / closing degree of the pressure plate may be roughly determined without strictly obtaining the opening / closing angle, and may be, for example, three angles of large angle, medium angle, and small angle, and three levels of light amount corresponding thereto. A set value may be set. On the contrary, the light amount setting value corresponding to the opening / closing angle of the pressure plate may be set more finely in 5 steps or more.

  In the above embodiment, all of the light amount setting value, the initial light amount setting value, and the light amount step-up according to the opening / closing angle of the pressure plate are stored in advance in the memory and read out each time. Instead of reading from the memory, these values corresponding to the pressure plate opening / closing angle are calculated each time using a function representing the relationship between the pressure plate opening / closing angle calculated in advance and the light amount setting value, the initial light amount setting value, and the light amount step-up amount. You may make it calculate.

  In the above-described embodiment, the light amount is increased step by step by the light amount step-up with the passage of time. However, the light amount may be continuously increased with the passage of time. As a result, the amount of light can be gradually increased without any discomfort for the user.

  As the pressure plate opening / closing detection means, when the fin 131 attached to the pressure plate opening / closing lever 130 is interlocked with the opening / closing of the pressure plate 108, the pressure plate opening / closing angle detection sensors 200a, 200b, 200c, 200d detect the opening / closing angle of the pressure plate. It is not limited to things. That is, various things can be used. For example, a reflecting plate is provided on the pressure plate, and a sensor unit having a light projecting unit and a light receiving unit is provided on the upper surface of the frame of the image reading unit, and light projected from the light projecting unit is reflected by the reflecting plate, and the light receiving unit The degree of opening and closing of the pressure plate can also be detected depending on whether or not the light is received at. Alternatively, the open / close angle of the pressure plate can be detected by using a plurality of light receiving portions and depending on which light receiving portion receives the light.

  The image reading apparatus is applied to a facsimile machine, a scanner device, a multifunction peripheral (MFP) having a print function, a copy function, a scanner function, and the like.

1 is a cross-sectional view illustrating a configuration of an image reading apparatus according to a first embodiment. It is a figure which shows the layout of the LED chip in the LED light source. 6 is a view showing the position of a document when document 100 is placed on document table glass 122. FIG. When the pressure plate 108 is opened, the LED light source 116 emits light, the light is reflected by the original 100, and the light from the LED light source 116 passes through a portion where the original 100 does not exist. It is a perspective view which shows the external appearance of the photo interrupter used as four pressure plate opening / closing angle detection sensors 200a, 200b, 200c, 200d. 2 is a block diagram illustrating a configuration of a control unit of the image reading apparatus 10. FIG. It is a figure which shows the circuit structure of the LED light source 116 and the LED light control circuit 700. FIG. It is a graph which shows the light quantity setting value of the LED light source 116 according to the opening / closing angle of the pressure plate at the time of document size detection. 6 is a flowchart illustrating a procedure for detecting a main scanning size of a document. It is a block diagram which shows the structure of the control unit of the image reading apparatus in 2nd Embodiment. 6 is a flowchart illustrating a procedure for detecting a main scanning size of a document. It is a timing chart which shows the change of the setting value of LED light quantity according to the opening / closing angle of a pressure plate in case a pressure plate opening / closing angle is 30 degrees. It is a timing chart which shows the change of the setting value of LED light quantity according to the opening / closing angle of a pressure plate in case a pressure plate opening / closing angle is 45 degrees. It is a timing chart which shows the change of the setting value of LED light quantity according to the opening / closing angle of a pressure plate in case a pressure plate opening / closing angle is 70 degrees. It is sectional drawing which shows the structure of the conventional image reading apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image reader 100 Original 108 Pressure plate 116 LED light source 121 Photoelectric conversion element 200 Pressure plate opening / closing angle detection sensor 600 Control unit (CPU)
602 memory 700 LED dimming circuit

Claims (8)

In an image reading apparatus that reads an image of a document ,
A document table on which the document is placed;
A pressure plate for holding a document placed on the document table ;
A light source for irradiating the document with light;
Reading means for generating image data in response to incident light;
Open / close detecting means for detecting the open / close degree of the pressure plate;
Adjusting means for adjusting the initial value of the amount of light emitted by the light source according to the degree of opening and closing of the pressure plate detected by the opening / closing detection means;
Size detection for detecting the size of the document placed on the document table based on the image data generated by the reading unit when the light source irradiates the document according to the light amount adjusted by the adjustment unit. Means ,
When the size detection unit cannot detect the size of the document placed on the document table, the adjustment unit increases the adjusted light amount,
The size detection unit detects the size of the document placed on the document table based on the image data generated by the reading unit in the irradiation of light from the light source according to the amount of light increased by the adjustment unit. ,
An image reading apparatus characterized by repeating the increase in the amount of light by the adjustment unit and the detection by the size detection unit until the increase in the amount of light by the adjustment unit reaches a predetermined value or until the size of the document can be detected . The light quantity adjusted at the initial stage of the first opening / closing degree of the pressure plate is higher than the light quantity adjusted at the initial stage of the second opening / closing degree, which is larger than the first opening / closing degree. The image reading apparatus according to claim 1. An increase value acquisition means for acquiring a light intensity increase value ;
A set value acquisition means for acquiring a light amount set value according to the degree of opening and closing of the pressure plate,
The adjustment means repeatedly increases the light amount increase value to the light amount setting value until the light amount increase reaches a predetermined value or until the size of the document can be detected, thereby increasing the light amount of the light source. The image reading apparatus according to claim 1 or 2 . Storage means for storing the light quantity setting value;
The image reading apparatus according to claim 3, wherein the setting value acquisition unit reads the light amount setting value stored in the storage unit. First storage means for storing the light quantity setting value;
Second storage means for storing the light quantity increase value;
The set value acquisition unit reads the light amount setting value stored in the first storage unit, and the increase value acquisition unit reads the light amount increase value stored in the second storage unit. The image reading apparatus according to claim 3. The image reading apparatus according to any one of claims 1 to 5, characterized in that the size of the document is the main scanning size. The image reading apparatus according to claim 1, wherein the light source is an LED light source in which point light sources including a plurality of LED chips are arranged. An original table on which an original is placed, a pressure plate for pressing the original placed on the original table, a light source for irradiating the original with light, and a reading means for generating image data according to the incident light. In the document size detection method of the image reading apparatus that reads the image of the document,
An opening / closing detection step for detecting an opening / closing degree of the pressure plate;
An adjustment step of adjusting an initial value of the amount of light emitted by the light source according to the degree of opening and closing of the pressure plate detected in the opening / closing detection step;
Size detection for detecting the size of the document placed on the document table based on the image data generated by the reading unit when the light source irradiates the document according to the light amount adjusted in the adjustment step. And having steps
If the size of the document placed on the document table cannot be detected in the size detection step, the adjusted light amount is increased in the adjustment step,
In the size detection step, the size of the document placed on the document table is detected based on the image data generated by the reading unit in the light irradiation from the light source corresponding to the light amount increased in the adjustment step. ,
A document size detection method , wherein the increase in the light amount by the adjustment step and the detection by the size detection step are repeated until the increase in the light amount by the adjustment step reaches a predetermined value or until the size of the document can be detected.

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