JP5676188B2 - Document size detection apparatus, document reading apparatus, and image forming apparatus - Google Patents

Description

  The present invention relates to a document size detection device, a document reading device, and an image forming apparatus, and more specifically, a document size detection device that detects a document size with a reflective optical sensor, a document reading device including the device, and The present invention relates to an image forming apparatus including the document reading device.

  2. Description of the Related Art Conventionally, a document reading device (scanner device) that optically reads a document and uses it as image data is mounted and distributed as an independent device or in an image forming apparatus such as a copying machine. This image data is subjected to processing such as printing and file storage.

  In such a document reading apparatus, there are many scenes in which it is necessary to determine the size of a document manually placed on a document table or a document sent and placed by an ADF (automatic document feeder). is there. Therefore, a document size detection device is mounted on the document reading device.

  In this document size detection device, a plurality of reflection type optical sensors are disposed below the document table glass in a predetermined positional relationship, and detect the presence or absence of the document on the document table glass at each position. The predetermined positional relationship refers to a relationship in which it is possible to determine the presence / absence of a predetermined size such as A4, B4, A5, and B5 that are generally present as the document size, and the document size is determined by a combination of output results of each reflection type photosensor. Can be determined.

  A reflection type optical sensor is composed of a light emitting element and a light receiving element (light receiving sensor) as a light source. The reflected light from the light source is received by the light receiving sensor, and the detected light quantity exceeds a threshold (or a threshold). If the value exceeds the threshold value, it is detected that there is a document, and if it is less than the threshold value (or less than the threshold value), it is detected that there is no document. The threshold value used here is fixed after adjustment at the time of manufacturing the apparatus.

  On the other hand, Patent Document 1 discloses a document size detection apparatus that employs a method of automatically reducing a threshold value with aging. FIG. 8 is a diagram for explaining document presence / absence detection processing by each reflection type optical sensor included in document size detection processing executed by the document size detection apparatus.

  First, at the time of initial setting of the document size detection apparatus (usually, at the time of shipment or installation), as illustrated as an initial output relationship on the left side of FIG. It is assumed that (III) is set. Here, (I) the output voltage when there is a black document is 1.3 V, (II) the output voltage when there is no document is 0 V, and (III) between I and II above, the threshold for detecting the presence of a document The value (threshold level) voltage is 0.8V. The output voltage when there is a white document is higher than 1.3V. If the threshold is not adjusted, the light intensity of the light emitting element of the reflective photosensor will decrease with age (with individual differences) after several years. For example, only 0.7V can be detected. At this time, since the threshold value is 0.8 V without adjustment, any document placed is erroneously detected as “no document”.

  In order to prevent such erroneous detection, automatic threshold adjustment is executed. This automatic threshold adjustment is performed with respect to some or all of a plurality of threshold values using an OC mat when the angle between the original pressing white plate (illustrated by the OC mat) and the original table glass is a predetermined angle. Executed. In the example of FIG. 8, when the reflection value from the OC mat (the light reception level by the reflected light) is output at a voltage of 0.35 V (−30% of 0.5 V at the initial setting) during adjustment, 0. Adjustment is made so that 8V × 70% = 0.56V is set as the threshold voltage level.

  Patent Document 2 discloses correcting the light amount of the light emitting side element in the reflective photosensor according to the angle of the OC mat.

JP 2008-107610 A JP 2010-130631 A

  However, in the document size detection apparatus described in Patent Document 1, the following erroneous detection can occur. First, when a black document having a high optical density (OD) value is placed, correction is performed to lower the threshold value. As a result, the OC mat is placed on the document glass. There is a possibility that the OC mat is erroneously detected as a document when the angle for determining the size (the angle for detecting the document size) is reached.

  Secondly, in a specification in which a plurality of document sizes such as AB and Inch systems must be identified by a limited number of optical sensors, a document edge having a size that should not be detected is detected, and a threshold value is detected. Will be corrected. As a result, when the OC mat is at an angle for determining the document size, the OC mat may be erroneously detected as a document.

  Third, since the threshold value is lowered with the aging of the optical sensor including the light emitting element, the adjusted threshold value may have a value with no margin for disturbance light.

  Patent Document 2 discloses correcting the light amount of the light emitting element in accordance with the angle of the OC mat, but does not disclose light amount correction due to deterioration of the light emitting element.

  The present invention has been made in view of the above-described actual situation, and the purpose of the present invention is a malfunction that may occur due to aging of the reflective optical sensor, such as a malfunction that cannot be detected by the reflective optical sensor even if there is a document. A document size detecting device capable of preventing malfunction such as disturbance light or a document holding white plate being erroneously detected as a document, a document reading device including the device, and an image forming device including the document reading device It is to provide.

In order to solve the above-mentioned problems, a first technical means of the present invention is a document size detecting device for detecting the size of a document placed on the document table glass, and is provided below the document table glass. A light emitting element and a light receiving element that are light sources arranged in a positional relationship are received, and the light reflected from the light source is received by the light receiving element, and a document at a corresponding position on the platen glass is received . presence of the plurality of reflective optical sensor that detects based on a comparison between the received light level with a predetermined threshold value of the reflected light, an adjustment unit that adjusts the emission level of each of the reflection type optical sensor of the plurality of, with respect to the angle of the document pressing whiteboard and the platen glass for pressing the original document over the platen glass, the initial value of the light receiving level of the reflected light in the state without the document, the reflective light on a plurality of angles For each sensor The adjustment unit is detected by the reflective optical sensor for each angle between the original pressing white plate and the original platen glass during the opening and / or closing operation of the original pressing white plate. said function indicated by the received level of the reflected light, only when the condition is met in the stored angle pairs function linearly related to the initial value shown in the initial value storage unit, the light emission level of the reflection type optical sensor Adjustment is executed, and if the condition is not satisfied, the light emission level of the reflective photosensor is not adjusted .

According to a second technical means, in the first technical means, the adjusting unit is a reflection type light that satisfies the above condition among the plurality of reflection type photosensors during the opening operation and / or the closing operation of the original pressing white plate. The light emission level is adjusted only for the sensor, and the light emission level is not adjusted for the reflective optical sensor that does not satisfy the above condition.
A third technical means is the first or the second technical means, wherein the adjustment unit, the angle between the document pressing whiteboard and the platen glass is sensed light receiving level of the reflected light when a predetermined angle The light emission level of the reflective photosensor is adjusted so as to coincide with the initial value for the predetermined angle.

A fourth technical means is the first or the second technical means, wherein the adjusting unit includes a light receiving of the reflected light is detected at a predetermined angle angle of the plurality of said original pressing whiteboard and the platen glass The light emission level of the reflective photosensor is adjusted so that the sum of squares of the difference between the level and the initial value for each of the plurality of predetermined angles is minimized.

According to a fifth technical means, in any one of the first to fourth technical means, the adjustment unit only determines a detection result when an angle between the original pressing white plate and the original table glass is 45 degrees or less. Based on this, the light emission level of the reflective photosensor is adjusted.

A sixth technical means is the technical means according to any one of the first to fifth technical means, wherein the adjusting unit only determines a detection result when an angle between the original pressing white plate and the original table glass is 45 degrees or less. On the basis of this, it is determined whether or not the linear relationship exists.

A seventh technical means is the technical means according to any one of the first to sixth technical means, wherein the adjustment unit powers on the document size detection apparatus when the initial value is stored or after the initial value is stored. It is characterized in that it is determined whether or not the linear relationship is satisfied after a predetermined period has elapsed.

According to an eighth technical means, in any one of the first to sixth technical means, the adjustment unit determines whether or not the linear relationship is satisfied when a predetermined user operation is received. It is a feature.

A ninth technical means is an original reading apparatus provided with the original size detecting device in any one of the first to eighth technical means.
A tenth technical means is an image forming apparatus provided with the document reading device in the ninth technical means.

  According to the present invention, in the document size detection device, malfunctions such as the reflection type optical sensor that cannot be detected by the reflection type optical sensor even if there is a document, disturbance light, and the document holding white plate are mistaken for the document. It is possible to prevent malfunctions such as detection.

FIG. 3 is a diagram for explaining a configuration example of a document reading device including a document size detection device according to an embodiment of the present invention. It is a figure for demonstrating the other structural example of the angle detection means applied to the original document size detection apparatus of this invention. FIG. 3 is a block diagram illustrating a circuit configuration example of a main part of the document size detection apparatus according to the present invention. It is a flowchart for demonstrating an example of the light emission level adjustment process in the original document size detection apparatus which concerns on this invention. 6 is a diagram illustrating an example of an output of an optical sensor with respect to an angle of a document cover in the document size detection apparatus according to the present invention. FIG. It is a top view which shows the other example of arrangement | positioning of the optical sensor in the original document reading apparatus of this invention. 1 is a cross-sectional view illustrating a configuration example of an image forming apparatus incorporating a document reading apparatus according to the present invention. It is a figure for demonstrating the document presence detection process in each optical sensor included in the document size detection process performed with the document size detection apparatus as described in a prior art.

  A document size detection device according to the present invention is a device that detects the size of a document placed on a platen glass by being transported manually or by an automatic document transport device, and includes a plurality of reflective optical sensors ( Hereinafter, it is simply referred to as an optical sensor. This document size detection device is generally provided in a document reading device (scanner device) that optically reads a document and outputs image data. Then, in the original reading apparatus, the original size is determined based on the combination of the output results of the respective optical sensors in order to limit the reading range of the original or to use for processing such as scaling after reading the original. As described above, the present invention can also take the form of a document reading device equipped with a document size detection device, and can also take the form of an image forming device such as a multifunction machine equipped with a document reading device, a simple copying machine, or a facsimile machine. It can be taken.

FIG. 1 is a diagram for explaining a configuration example of an original reading apparatus including an original size detecting apparatus according to an embodiment of the present invention.
A document reading apparatus 1 illustrated in FIG. 1 includes a document table glass 11 on the top surface of a housing 10, and a scanner unit (not shown) provided therein, and a document P placed on the document table glass 11. It is possible to read the image.

  The casing 10 is provided with a document cover 13 to which a document pressing white plate (hereinafter, exemplified by the OC mat 14) is attached on the document table glass 11 side so as to be opened and closed. The document cover 13 has a lid shape that opens and closes up and down with the rear side as a fulcrum when placing a document. The original pressing white plate may be a white plate such as a white sheet for covering the original platen glass 11 and pressing the original P, and is not limited to the OC mat 14. The original P is not limited to a thin sheet, and may be a thick read medium such as a book. The OC mat 14 serves to protect the original P when the original P is pressed.

  In the document reading apparatus 1, the document P is placed on the document table glass 11 and the image reading process is generally performed with the document cover 13 closed, but the document cover 13 remains open. Image reading processing in the state shown in FIG. 1 is also possible.

  A switch 15 for detecting a document cover closed state is provided inside the housing 10 so that the closed state or the open state of the document cover 13 can be detected. By detecting that the switch 15 has returned from the closed state to the closed state with the switch 15, it is possible to perform control such that the document size detecting device is operated. The switch 15 is not limited to the arrangement shown in FIG. 1, and may be provided at a position where it is turned on by the document cover 13 in the closed state or the open state, and turned off in the open state or the closed state. May be.

  The document reading device 1 according to the present invention is provided with a document size detection device inside the housing 10 or the like. In this document size detection apparatus, a plurality of optical sensors (illustrated by three optical sensors 12a to 12c in this case) are arranged below the document table glass 11 in a predetermined positional relationship, and have a size determination unit 17a. A control unit 17 is provided.

The control unit 17 corresponds to a main control unit of the document size detection apparatus, that is, a main control unit or a sub control unit of the document reading apparatus, and can be configured by, for example, a microcomputer. More specifically, the control unit 17 stores, for example, a control program for controlling the entire document size detection device or the entire document reading device 1, ROM or EEPROM (registered trademark) storing various data, and the control program. It can be configured by a CPU for execution and a RAM as an execution area thereof. The various data include parameters for determining a linear relationship and parameters for adjustment, which will be described later, in addition to parameters including a predetermined threshold, which will be described later, used for document size determination.

  Each of the optical sensors 12a to 12c is an optical sensor for detecting presence / absence of a document, which includes a light emitting element such as an LED and a light receiving element such as a phototransistor. Each of the optical sensors 12a to 12c detects the presence / absence of a document at a corresponding position on the document table glass 11 based on a comparison between a light reception level of reflected light and a predetermined threshold value. Here, the plurality of predetermined threshold values (a total of three threshold values in this example) are fixed values.

  The size determination unit 17a detects a document based on a combination of output results of the optical sensors 12a to 12c, and determines the size of the document. Therefore, the size determination unit 17a can be said to be a document size detection unit. This determination condition depends on the predetermined positional relationship described above. In addition, each optical sensor 12a-12c may be arrange | positioned so that a movement is possible, and should just become the predetermined positional relationship mentioned above at the time of size detection.

  In the example of FIG. 1, the document P placed on the document table glass 11 reflects the light from the light emitting elements of the optical sensors 12a and 12b, and the reflected light is received by the respective light receiving elements, and the size determination unit. In 17a, it is detected that the received light level is equal to or higher than the threshold value, and a detection result that there is a document is output. On the other hand, even if light from the light emitting element of the optical sensor 12c passes through the platen glass 11 and is reflected by any one of the metaphors (including other external light), the light amount detected by the light receiving element is small. The detection result indicating that there is no original is output.

  Based on these detection results, it can be determined that the document P has a size having a distance between the distance from the end of the document table glass 11 to the optical sensor 12b and the distance from the same end to the optical sensor 12c. In FIG. 1, the original can be detected when the optical sensor 12a is horizontally placed B5 (that is, B5R) or more, the original sensor can be detected when the optical sensor 12b is horizontally A4 (that is, A4R) or more, and the original can be detected when the optical sensor 12c is horizontally placed B4 or more. In this way, it is assumed that each is arranged. In this case, in the above example, it can be determined that the document P is A4 size.

  The document size detection apparatus according to the present invention includes an angle detection unit because it is necessary to measure the angle between the OC mat 14 and the document table glass 11 as will be described later. The angle detection unit includes a document cover closed state detection switch 15 and an angle detection sensor 16. While the closed state is detected by the switch 15, the angle detection sensor 16 is not operated, and the angle detection sensor 16 is operated only when it is not detected, that is, when it is in the open state. Such control may be performed by the control unit 17.

  The angle detection sensor 16 can be composed of, for example, a plurality of light receiving elements installed at specific angle intervals on the side end of the support shaft of the document cover 13. Thus, the angle can be detected from the position of the light receiving element shielded by the document cover 13. For detecting the angle of the document cover, a gyro sensor or the like attached to the document cover 13 side can also be used.

  A configuration example of an angle detection sensor that can be provided instead of the angle detection sensor 16 in the document reading apparatus 1 of FIG. 1 will be described with reference to FIG. As illustrated in FIG. 2, a variable resistor whose resistance value changes according to the rotation angle of the document cover 13 is used as an angle detection sensor that detects the angle of the OC mat 14. The angle detection sensor of this example is provided at the side end of the support shaft 19 of the document cover 13. Here, the resistor 16 a connected to the DC power supply 16 b is arranged so as to go around the support shaft 19. Further, the movable piece 16c that comes into contact with the resistor 16a rotates integrally with the document cover 13 to constitute the variable resistor.

  The resistor 16 a and the movable piece 16 c are connected to the control unit 17. Here, the position of the movable piece 16c may be fixed, and the resistor 16a may rotate integrally with the document cover 13. When the document cover 13 is opened and closed, the position of the movable piece 16c that contacts the resistor 16a slides to change the resistance value, and the voltage value at this time is detected by the control unit 17. In the control unit 17, the relationship between the voltage value and the angle is stored in advance in a storage device so that the angle of the OC mat 14 can be calculated according to the voltage value. This storage device may be a storage device used as an initial value storage unit 18 described later.

  The document size detection apparatus according to the present invention includes an adjustment unit 17b and an initial value storage unit 18 as main features.

  The adjusting unit 17b adjusts the light emission level of each of the plurality of optical sensors 12a to 12c, that is, the light emission level of each light emitting element. The optical sensors 12a to 12c receive reflected light with a light receiving element with respect to light emitted from the light emitting element at a predetermined light emission level (light emission luminance level), but the predetermined light emission level actually changes over time. Even if an attempt is made to emit light at a predetermined light emission level, light can be emitted only at a light emission level less than that, and the light reception level is lowered even under the same conditions. The adjustment unit 17b performs the adjustment. The adjustment unit 17b can be provided in the control unit 17 as illustrated in FIG. 1, that is, can be incorporated as an adjustment program.

  The initial value storage unit 18 sets the initial value of the light reception level of the reflected light in the absence of the document with respect to the angle between the OC mat 14 and the document table glass 11 for each of the optical sensors 12a to 12c for a plurality of angles (opening / closing angles). The storage device stored in Here, the initial value may be a value measured without a document, or may be a specified value of the same model. Note that the initial value basically varies depending on the position of the photosensor, and therefore differs depending on the photosensor. In addition, since the initial values of the optical sensors 12a to 12c vary depending on the installation location of the document reading apparatus 1, they may be measured and updated each time the installation location is changed.

  The adjusting unit 17b according to the present invention adjusts the light emission level as described above. However, the adjusting unit 17b does not execute the condition unconditionally, and each light is determined based on the output values of the plurality of optical sensors 12a to 12c and the detection angles of the angle detecting units. The sensors 12a to 12c determine the state of no document, and at least perform the adjustment in a state where it is determined that there is no document. Then, the adjustment unit 17b determines whether or not there is no document by comparing the initial value with the initial value.

  More specifically, the adjustment unit 17b causes the light sensor 12a to detect the light reception level of the reflected light at each angle when the OC mat 14 is opened or closed, and indicates the light reception level of the reflected light for each detected angle. Only when the function is linearly related to the function indicated by the initial value for each angle stored in the initial value storage unit 18 (the function indicated by the angle vs. initial value), the light emission level of the optical sensor 12a is adjusted. . In other words, the adjustment unit 17b determines whether or not the mapping from the “initial value stored in the initial value storage unit 18” to “the received light level of the detected reflected light” at each angle is a linear map. Only when it can be said that it is in the linear mapping (considering errors), the light emission level of the optical sensor 12a is adjusted.

  The adjustment of the light emission level will be briefly described. The adjustment is performed using the OC mat 14, that is, using the reflected light in the opening / closing operation of the document cover 13. Further, the adjustment of the light emission level is executed based on the initial value and the received light level of the reflected light determined to satisfy the linear relationship in order to maintain the linear relationship (at a stage where there is no document). To do. As described above, the adjustment is executed based on the light reception level at an angle at which the reflected light can be obtained using the OC mat 14 among the light reception levels detected to satisfy the linear relationship. With regard to how to adjust, if the light emission level is adjusted so that the light reception level under the same conditions is maintained regardless of aging (maintained before and after aging), the predetermined threshold value is changed. The same document size determination can be made at least.

  Here, the opening operation and the closing operation may be determined based on the detection result of the closing operation of the switch 15. Further, the above determination may be performed based on the detection results during both operations when the opening operation and the closing operation are performed as a series of operations. The angle to be detected may be determined in advance, or may be detected at a plurality of predetermined angles without being limited to the same pitch. The angle at which the light reception level is detected at the time of determination may be the same as the angle at which the initial value is stored in the initial value storage unit 18 or may be different, as long as at least the presence or absence of a linear relationship can be determined as a function.

  In the case of a linear relationship, if Xθ is an OC mat reflection initial value with respect to the angle θ of the document cover, and f (Xθ) is a light reception level detected after a secular change with respect to the angle θ, f (Xθ) = α · Xθ (Where α is a real number), that is, the mapping f (Xθ) is linear. Conversely, it may be understood that Xθ indicates the received light level detected after aging with respect to the angle θ, and f (Xθ) indicates the OC mat initial value with respect to the angle θ. More generally, the case of a linear relationship indicates that the function of the initial value for θ and the function after aging have the same change tendency. In other words, in the present invention, if both functions have the same change tendency, adjustment may be performed (permitted) by normal operation. Of course, it is preferable to allow a certain amount of error in determining whether or not the relationship is linear, and it is also possible to determine whether or not the relationship is linear by simply comparing the two values.

  Similarly, the light emission level of the optical sensor 12b is adjusted only when the detection result at each angle for the optical sensor 12b is in a linear relationship with the function indicated by the angle versus initial value. The same applies to the optical sensor 12c. The determination as to whether or not the linear relationship is satisfied may be performed at the time of one opening operation or closing operation for all of the optical sensors 12a to 12c.

  Basically, even when all the optical sensors 12a to 12c are determined at the same time, the determination result may be different for each optical sensor. When making adjustments to the optical sensor, the same adjustment may be executed uniquely for other optical sensors (even if there is not much difference).

  Further, as described above, the determination is made for each of the optical sensors 12a to 12c, and the adjustment is performed for the optical sensor only when there is a linear relationship. This is because the linear relationship indicates that at least the optical sensor is in a state where adjustment may be performed (a state suitable for light amount correction). However, in the present invention, the adjustment may be executed only when all the optical sensors have a linear relationship.

  As described above, according to the present invention, light from the light emitting element is emitted from the OC mat of the document cover 13 in the process of operating the document cover (the opening / closing angle changes from 0 degrees to 90 degrees, for example). Return light reflected at 14 is detected, and the optical sensor output detected in the process is compared with the initial value recorded in the absence of the document. According to this comparison, the present invention detects whether or not a disturbance light or an original is accidentally placed depending on whether or not the two are in a linear relationship, that is, whether or not the linear relationship is satisfied. In the present invention, if there is no original or the like and there is no disturbance light, the light emission level of the optical sensor is adjusted (resulting in adjustment of the output light amount). Then, adjustment is performed based on the light reception level at an angle at which the reflected light can be obtained using the OC mat 14 among the light reception levels detected to satisfy the linear relationship.

  Since the original size detection apparatus of the present invention performs adjustment in a normal operating state, it can prevent malfunctions such as ambient light and the OC mat 14 being erroneously detected as an original due to aging degradation of the optical sensor. Since adjustment is performed using the OC mat 14 (for example, adjustment is performed so that the light reception level under the same conditions is maintained regardless of aging deterioration), even if there is a document due to aging deterioration of the optical sensor, the optical sensor detects it. It is possible to prevent malfunctions that cannot be made.

  In addition, the adjustment unit 17b determines whether or not the linear relationship is satisfied after a predetermined period from the time when the initial value is stored or when the power of the document size detection apparatus is turned on after the initial value is stored. Is preferred. As a result, the above determination can be automatically executed, and adjustment can be automatically executed as necessary based on the determination. Therefore, light amount calibration by a user operation is unnecessary, and malfunction due to aging degradation of the optical sensor. Can be prevented in advance. The predetermined period may be determined in view of the performance of the light emitting element, and the predetermined period may be substituted by calculating the operating time instead of the actual elapsed time of the year.

  Alternatively, the adjustment unit 17b may determine whether or not the linear relationship is satisfied when a predetermined user operation is received. Thereby, a user or a maintenance contractor can appropriately perform the determination, and automatically adjust as necessary based on the determination, thereby preventing malfunction due to aging degradation of the optical sensor.

  As described above, in the document reading apparatus 1, regardless of whether the predetermined period has elapsed or the user operation is a trigger, if the result of the determination is that there is a linear relationship, the light emission level is basically adjusted. However, even if it is a linear relationship, if there is not much difference and the approximation is not necessary, it is not necessary to adjust, so that the adjustment need not be executed. In this way, the adjustment itself can also be executed by determining a threshold value for the difference in function and performing threshold processing. In this way, at least the adjustment of the light emission level of the optical sensor may be performed only when there is a linear relationship.

<Circuit Configuration Example of Document Size Detection Device and Specific Example of Light Level Adjustment>
FIG. 3 is a block diagram showing a circuit configuration example of a main part of the document size detecting apparatus according to the present invention. The main part 20 illustrated in FIG. 3 is incorporated in the document reading apparatus 1 illustrated in FIG.

  The main part 20 includes a first sensor block a (22a), a second sensor block b (22b), a third sensor block c (22c), an A / D converter 24, a switch 25, and a D / A converter. 26, a switch 27, a switch 15 and an angle detection unit comprising an angle detection sensor 16, an initial value storage unit 18, and a control unit 17 for controlling them. As described above, the control unit 17 includes the size determination unit 17a and the adjustment unit 17b.

In the ROM or EEPROM (registered trademark) of the control unit 17, as a parameter used for document size determination, a reference value (light reception level) of a light sensor output value (light reception level) with respect to an angle between the document cover 13 and the document table glass 11 for each size ( The predetermined threshold value) data and the OC mat reflection light value data are recorded and held as necessary. In particular, at least the angle determined to perform document size detection is retained. In addition, the ROM and EEPROM (registered trademark) of the control unit 17 hold parameters for determining a linear relationship, parameters for adjustment, and the like. The initial value storage unit 18 holds the angle versus initial value, but may be configured to be included in the ROM or EEPROM (registered trademark) .

  The sensor block 22a includes an optical sensor (original size sensor a) 12a for detecting an original size, and the optical sensor 12a includes a light emitting unit using an LED and a light receiving unit using a phototransistor. Light emission in the light emitting unit is controlled by a light emission pulse signal output from the control unit 17 (light emission output a in the case of the optical sensor 12a). The sensor block 22a further includes a voltage converter 28a that can adjust the reference voltage in order to adjust the voltage applied to the LED. The light receiving unit converts the current flowing by the received light into a voltage value, and outputs it to the switch 25 as a sensor output value (sensor output a = Ri in the case of the optical sensor 12a).

  The sensor blocks 22b and 22c have the optical sensors 12b and 12c of FIG. 1, respectively, have the same configuration as the sensor block 22a, and output the respective sensor output values to the switch 25.

  The switch 25 is provided to select the light reception output to be used from the sensor blocks 22a to 22c based on the input light reception output switching signal. The controller 17 sequentially switches the sensor outputs output from the optical sensors 12 a to 12 c by outputting a light reception output switching signal to the switch 25, and inputs the sensor output to the A / D converter 24.

  The A / D converter 24 converts the light reception output selected by the switch 25 (the output of the phototransistor of the photosensor in the selected sensor block) into a digital signal and outputs it to the control unit 17. The A / D converter 24 is commonly used to convert the output values of the plurality of optical sensors 12a to 12c into digital values. The control unit 17 uses the sensor output value input from the A / D converter 24 to execute document size detection processing and sensor output detection processing for determining whether the linear relationship is present.

  The D / A converter 26 is used for correcting the light emission level of the light emitting unit, that is, correcting the light amount. More specifically, the adjustment unit 17b compares the function indicated by the initial value (angle vs. initial value) in the initial value storage unit 18 with the function indicated by the current angle vs. received light level value and determines whether or not the relationship is linear. Determine whether. Only when the relationship is linear, the adjustment unit 17b outputs a digital light amount correction signal to the D / A converter 26. As an example, the light amount correction signal may be determined according to the difference between the two, and more specifically according to the coefficient α described above.

  The D / A converter 26 receives the digital light amount correction signal output from the adjustment unit 17b, converts it into an analog signal, and outputs it to the voltage converter 28a. The voltage converter 28a corrects the reference voltage applied to the LED based on the signal. The D / A converter 26 is commonly used to convert light amount correction signals to the plurality of sensor blocks 22a to 22c into analog signals. The switch 27 selects a sensor block including an LED to be adjusted from the sensor blocks 22a to 22c based on a correction (adjustment) target switching signal from the adjustment unit 17b of the control unit 17.

  Here, basically, the light emission levels of the optical sensors 12a to 12c are not set to the maximum values at the time of shipment (at the stage of storing the initial values), but can be adjusted to the increase direction of the light emission levels due to secular change. Decide with a margin. The light emission level can be changed by changing the current flowing through the LED by correcting the reference voltage as described above. However, the ON duty of the light emission pulse signal can be changed by PWM dimming by changing the circuit configuration. It is also possible to change the average light emission level by changing. In any change, the light amount is basically adjusted in the direction of increasing with respect to secular change.

An example of the light emission level adjustment process in the document size detection apparatus according to the present invention will be described with reference to the flowchart shown in FIG.
As described above, when the switch 15 detects that the document cover 13 has changed from the closed state to the open state for the first time when the passage of a predetermined period or reception of a predetermined user operation is a trigger and the trigger is valid, The adjustment unit 17b of the control unit 17 mainly performs the following processing.

  First, n is set to 1 (step S1), and light is received by the nth photosensor (step S2). In step S2, light is received at a predetermined pitch from 0 ° to X °. Here, X may be determined in advance between 0 ° and 90 °.

  Next, the received value is compared with the initial value stored in the initial value storage unit 18 in the absence of the document (that is, with the reflected light from the OC mat 14) (step S3). In this example, it is assumed that the initial values to be compared are also held at the same predetermined pitch in the same range. In step S3, it is only necessary to compare whether or not the two functions are in a linear relationship as a result.

  When one is in a linear relationship with the other (in the case of YES in step S4), using the angle detection result using the OC mat 14, the correction of the light amount, that is, the light emission level of the nth photosensor is performed. Adjustment is performed (step S5). After the process of step S5, n is incremented for the process for the next optical sensor (step S6). On the other hand, if NO in step S4, that is, if the above linear relationship is not satisfied, the process proceeds to step S6 without performing the process of step S5, that is, without performing light amount correction on the nth photosensor. .

  After step S6, it is determined whether n is greater than 4, that is, whether the process has been completed up to the third photosensor (step S7). If NO, the process returns to step S2, and YES. If the process ends, the process ends.

  A specific example of such processing will be described with reference to FIG. FIG. 5 is a diagram showing an example of the output of the optical sensor with respect to the angle of the document cover in the document size detection apparatus according to the present invention. In FIG. 5, the degree of opening of the angle between the document cover 13 and the document table glass 11 is schematically shown on the upper side of the graph.

  As the initial value, for example, if data corresponding to the function indicated by the solid line in FIG. 5 (however, there is no disturbance light) is stored in the initial value storage unit 18, the data is linear as shown by the function indicated by the alternate long and short dash line. If there is a relationship, the light amount correction is executed. This utilizes the fact that the reflection value (initial value) of the OC mat 14 with respect to the angle of the OC mat 14 in the absence of ambient light has a linear relationship with the reflection value when the light emitting portion deteriorates over time. In this case, if the light amount correction is not performed, the predetermined threshold value is less likely to be exceeded. In the example of FIG. 5, even when a white document is placed, the threshold value is almost equal to the threshold value, and the document cannot be detected.

  For comparison, FIG. 5 also shows a function of an initial value in the case where ambient light is present. When this function is larger than the angle of the document cover 13 (OC mat 14) suitable for actually executing the document size determination of 5 ° to 45 °, the function is different from the case of no disturbance light. That is, in the presence of disturbance light, the sensor value when the document cover 13 is opened is large, and when the document cover 13 is close to the closed state, the sensor value suddenly decreases, and the disturbance is not reduced until the angle is smaller than the above suitable angle. It almost coincides with the case without light.

  Note that when the document cover 13 is closed or opened, the document size is detected between 5 ° and 45 °. The reason is that if the document cover 13 is 45 ° or more, it is easily affected by ambient light, and if it is less than 5 °, it is easily affected by reflection from the OC mat 14. Basically, it is sufficient to detect the document at one point between such angles.

  If the above linear relationship is not satisfied, it is a case where “determination that the document is not placed on the platen glass 11” cannot be performed, and thus the light amount correction is not performed. For example, (1) when there is disturbance light and the angle (opening angle) of the document cover 13 is large, the detection result has the form shown in FIG. 5 with respect to the initial value with disturbance light and is stored. This indicates a function having a change that does not satisfy the linear relationship with the initial value without disturbance light.

  Further, (2) when a white document or a black document is placed during the opening operation or the closing operation, a function that does not satisfy the linear relationship after the angle at which the white document or the black document is placed is shown. . (3) If an edge of a document of a size that should not be detected (such as a size that should be detected by the adjacent optical sensor) is detected during the opening or closing operation, the angle after the detected angle of the document is detected. Is a function that does not satisfy the linear relationship. Regarding the above (2) and (3), the one-dot chain line in FIG. 5 changes so that an inflection point different from the straight line in FIG. 5 exists at the stage where the document is placed.

  Next, a specific example will be given regarding the adjustment of the light emission level. As described above, among the light receiving levels detected to satisfy the above linear relationship, the same light receiving level based on the angle at which the reflected light can be obtained using the OC mat 14 in the opening / closing operation of the document cover 13 is the same. If the light emission level is adjusted so that the light reception level under the conditions is maintained regardless of deterioration over time, the same document size determination can be made without changing the predetermined threshold value.

  On the other hand, in the technique described in Patent Document 1, the light receiving level value at one point (a point where the document cover is open / closed) is checked against deterioration of the light emitting element, and correction is performed based on the result. The predetermined threshold value is automatically lowered along with aging. In the present invention, as compared with the method described in Patent Document 1 in which the threshold value is automatically lowered with aging, even if a black document with a high OD value is placed, it is not erroneously corrected and detected. Even if an edge of a document having a size that is not to be detected is detected, correction is not erroneously performed, and a margin for disturbance light can be maintained.

An example of adjustment that keeps the light reception level under the same conditions regardless of deterioration over time will be given.
As a result of adjustment, the adjustment unit 17b adjusts the received light level of the reflected light detected when the angle between the OC mat 14 and the document table glass 11 is a predetermined angle so that it matches the initial value with respect to the predetermined angle. What is necessary is just to adjust the light emission level of an optical sensor. This adjustment may be performed while feeding back the light reception level, or a predicted value that is stored in advance based on the difference of the comparison target may be used.

  Here, as the predetermined angle, it is preferable to employ an angle for performing document size detection as exemplified in any of 5 ° to 45 °. That is, the predetermined angle is an angle at which external light such as a fluorescent lamp enters from the gap between the OC mat 14 and the platen glass 11 to some extent and the influence of external light on the light receiving element of the optical sensor is small. What is necessary is just to set suitably 10 degrees, 20 degrees, 30 degrees, 45 degrees. This makes it possible to adjust the light emission level when determining the actual document size, so that the amount of light can be adjusted with a simple correction that increases the amount of light so that the two values match, and enables accurate document size determination. become.

  The predetermined threshold value is determined by the light reception level (sensor output value A) detected as reflected light from the black original placed on the black original and the OC mat 14 when the OC mat 14 is at a predetermined angle. In particular, it is preferably set to an intermediate value (median value) between the received light level (sensor output value B) detected as reflected light. For example, as illustrated as the initial output relationship in FIG. 8, the output voltage value when there is a black original is 1.3V, and the output voltage value due to the initial reflected light from the OC mat 14 having a predetermined angle is 0.5V. Then, the optimum initial value (median value) of the threshold value is 0.9V. Further, the predetermined angle may be set to an angle included in a movable angle range that is difficult to move when compared with other movable angle regions when the OC mat 14 moves in the circumferential direction.

  As an alternative, an adjustment may be made so that it is closest to the original relationship when viewed globally. Therefore, for example, it is assumed that there are a plurality of the predetermined angles, and the adjustment unit 17b determines that the sum of squares of the difference between the light reception levels and the initial values for the plurality of predetermined angles is minimized as a result of the adjustment. What is necessary is just to adjust the light emission level of an optical sensor. That is, the sum of squares of the difference between the light reception level of the reflected light detected when the angle between the OC mat 14 and the document glass 11 is a plurality of predetermined angles and the initial value for each of the plurality of predetermined angles is minimized. For example, the light emission level of the optical sensor may be adjusted. This adjustment may also be performed while feeding back the light reception level, or a predicted value stored in advance for the coefficient α may be used.

  To give a simpler example, the square of the difference between the received light level for 20 ° and its initial value, the square of the difference between the received light level for 30 ° and its initial value, and the received light level for 45 ° The light emission level may be selected such that the sum of the difference and the square of the initial value is minimized. Such an adjustment is also an adjustment that maintains the light reception level under the same conditions regardless of the deterioration over time.

  Next, a preferred example of the angle range defined by X in steps S2 and S3 will be described.

  As illustrated in FIG. 5 described above, if the function of the initial value in the presence of disturbance light is larger than the open angle (5 ° to 45 °) suitable for actually executing the document size determination, there is no disturbance light. It becomes a function different from the case of. Therefore, it is preferable that the adjusting unit 17b adjusts the light emission level of the optical sensor based only on the detection result when the angle between the OC mat 14 and the document table glass 11 is 45 ° or less. The adjustment based only on the detection result of 45 ° or less corresponds to the adjustment using the OC mat 14. As a result, the light is not affected by the disturbance light, and even if the document reading apparatus is placed directly under the fluorescent lamp, the light amount can be corrected and the adjustment without the influence of the disturbance light can be performed. .

  Further, the adjustment unit 17b may determine whether or not the linear relationship is established based only on the detection result when the angle between the OC mat 14 and the platen glass 11 is 45 ° or less. . In this case, since the adjustment is performed when the linear relationship is satisfied, any of the following processes can be applied. In the first process, only whether or not the above linear relationship is determined is executed only for the detection result in the case of 45 ° or less, and the actual adjustment is executed with reference to the other detection results. Or you may employ | adopt the 2nd process of performing both the process of determination and adjustment based only on the detection result of 45 degrees or less.

<Threshold setting example 1>
In the above description, it is assumed that the light emission level is adjusted so as to maintain the light reception level under the same conditions. Further, the document size detection apparatus according to the present invention has been described on the assumption that a plurality of threshold values (in this example, a total of three threshold values) corresponding to each of the plurality of optical sensors 12a to 12c are fixed values. . However, it is possible to prevent malfunction due to aging deterioration of the optical sensor by simultaneously changing the predetermined threshold value without performing such adjustment. The threshold value is adjusted by using the OC mat 14 when the angle between the OC mat 14 and the document table glass 11 is the predetermined angle.

<Threshold setting example 2>
As another method for adjusting the plurality of threshold values, similarly to Patent Document 1, when the angle between the OC mat 14 and the platen glass 11 is the predetermined angle without being interlocked with the adjustment of the light emission level. The adjustment to some or all of the plurality of threshold values may be executed using the OC mat 14. However, in the document size detection apparatus according to the present invention, the light emission level is adjusted after returning the threshold value to the original value after a certain period of use, in order to cope with aging. do it. Then, the threshold value adjustment by the threshold value adjustment unit is performed until the use period elapses again, and the light emission level may be adjusted similarly when the use period has elapsed.

<Other arrangement examples of optical sensors for detecting presence / absence of document>
FIG. 6 is a top view showing another arrangement example of the optical sensor in the document reading apparatus of the present invention. An arrangement as shown in FIG. 6 can be adopted as an example of the arrangement of the photosensors for detecting the presence or absence of the document. That is, with respect to the alignment origin on the platen glass 11 (here, the upper left in FIG. 6), the sensor a that is blocked by a vertically placed document of A5 size or more and a horizontally placed document of A4R or more, and a portrait document of B5 size or more. A sensor b blocked by a placed document and a horizontally placed document of B4 or larger, and a sensor c blocked by a vertically placed document of A4 size or larger and a horizontally placed document of A3 or larger are arranged as shown in FIG. Further, a sensor d which is blocked by a horizontally placed document of A5R size or larger and a vertically placed document of A4 or larger is arranged as shown in FIG. Further, as a group of sensors for horizontally placing a document larger than the document A4 in portrait orientation, a sensor e that is blocked by a horizontally placed document of B5R size or larger, a sensor f that is blocked by a horizontally placed document of A4R size or larger, B4 size. The sensor g that is blocked by the horizontally placed document and the sensor h that is blocked by a horizontally placed document of A3 size or larger are arranged as shown in FIG.

  By combining the detection results of these sensor groups, for example, when the document P is placed and detected by the sensor a and not detected by the sensor b, it can be determined as the A5 size or the A4R size. At the same time, when the sensor f is detected, it can be determined as A4R size, and when it is not detected, it can be determined as A5 size. Although only an example of dealing with a simple horizontal document as illustrated in FIG. 1 has been described, various arrangement examples of the optical sensor for detecting the presence / absence of a document can be applied.

<Example of document reading device installation>
FIG. 7 shows a cross-sectional view of an example of an image forming apparatus incorporating a document reading device including the document size detection device according to each of the embodiments described above. The image forming apparatus illustrated in FIG. 7 is roughly composed of an image reading unit 100 corresponding to the document reading apparatus according to the present invention, an image forming unit, a paper feeding unit, and a post-processing device.

  As shown in FIG. 7, the image reading unit 100 includes a transparent document placement table (document table glass) 111 and a document image reading unit for scanning and reading an image of a document placed on the document table glass 111. In other words, the scanner unit 110, a document cover 113 with an OC mat 114 added thereto, and a double-sided automatic document feeder (RADF) 120 for automatically supplying a document onto the document table glass 111 are configured. . The RADF 120 is attached to the document cover 113. The OC mat 114 is provided so as to be rotatable in a belt manner for the RADF 120.

  The scanner unit 110 includes a lamp reflector assembly that exposes the surface of a document, and a first reflecting mirror that guides a reflected light image from the document to a photoelectric conversion element (CCD) 124 that converts the reflected light image into an electrical image signal. The scanning unit 121 includes a second scanning unit 122 equipped with second and third reflection mirrors, and an optical lens body 123 for forming a reflected light image on the CCD 124. The first scanning unit 121 is scanned so as to travel from the left to the right along the platen glass 111 at a constant speed V, and the second scanning unit 122 is scanned in the same direction at a speed of V / 2.

  As a result, the image reading unit 100 moves the scanner unit 110 along the lower surface of the platen glass 111 while sequentially placing the document to be read on the platen glass 111 by operations related to the RADF 120 and the scanner unit 110. Thus, the image of the document placed on the document table glass 111 is sequentially formed on the CCD 124 for each line, and the document image is read. The document to be read can be placed on the document table glass 111 with the document cover 113 opened.

  The document size detection apparatus according to the present invention includes optical sensors 112a to 112c corresponding to the optical sensors 12a to 12c, a switch 115 corresponding to the switch 15, an angle detection sensor 116 corresponding to the angle detection sensor 16, and a control for controlling them. The image reading unit 100 is mounted as a control unit (not shown) corresponding to the unit 17. Then, before moving the scanner unit 110 along the lower surface of the document table glass 111, the presence or absence of the document is detected by the optical sensors 112a to 112c, and the document size can be determined. Based on the determined document size, the moving range of the scanner unit 110 is limited, and the read image data is subjected to scaling processing.

  The image data obtained by reading the document image with the scanner unit 110 is subjected to various processes and then temporarily stored in a memory (not shown), and the image data is output from the memory to the image forming unit in response to an output instruction. Then, after being reproduced as a visible image on the photosensitive drum 142, the image is transferred onto a sheet to form a toner image.

  The image forming unit includes a laser writing unit (LSU) 141 and an electrophotographic process unit 140 for forming an image. The LSU 141 includes a semiconductor laser that emits a laser beam in accordance with image data read from a memory or image data transferred from an external device such as a PC, a polygon mirror that deflects the laser beam at an equal angular velocity, and a laser beam that is deflected at an equal angular velocity. Has an f-θ lens that corrects the photosensitive drum 142 of the electrophotographic process unit 140 so as to scan at a constant speed.

  In the electrophotographic process unit 140, a charging device 143, a developing device 144, a transfer device 145, a peeling device 146, a cleaning device 147, and a charge eliminating device are arranged around the photosensitive drum 142 according to a well-known mode. The fixing device 148 is arranged on the downstream side.

  The paper feed unit includes first to third cassettes 131 to 133, a manual feed tray 135, and a large capacity cassette 134. The first cassette 131 is a tandem tray that accommodates the first tray and the second tray, and both trays can be pulled out from the apparatus main body at the same time. The second cassette 132 and the third cassette 133 accommodate a third tray and a fourth tray, respectively. The large capacity cassette 134 is the fifth tray. The sheet feeding / conveying units 136 and 137 include a sheet feeding roller, a conveying roller, and a registration roller for conveying a sheet from the sheet feeding unit to a transfer position between the photosensitive drum 142 and the transfer device 145. In these five trays, sheets are stacked and stored for each size, and when a cassette or tray storing sheets of a size desired by the user is selected, the top of the sheet bundle in the tray is selected. The sheets are fed one by one and sequentially conveyed toward the electrophotographic process unit 140 via the conveyance paths of the sheet feeding conveyance units 136 and 137.

  A paper discharge path 149 is provided on the downstream side of the fixing device 148 in the paper conveyance direction. The paper discharge path 149 includes a paper discharge conveyance path 151 of the post-processing apparatus and a refeed conveyance section 150 for duplex copying. And branching.

  In the LSU 141 and the electrophotographic processing unit 140, the image data read from the memory is formed as an electrostatic latent image on the surface of the photosensitive drum 142 by scanning the laser beam with the LSU 141, and the toner of the developing device 144 The visualized toner image is electrostatically transferred by the transfer device 145 onto the surface of the paper conveyed from the paper feeding unit, and is fixed by the fixing device 148.

  The sheet on which the image is formed in this manner is sent from the fixing device 148 to the post-processing device, or selectively conveyed to the refeed conveyance unit 150 for duplex copying. The paper sent to the post-processing device is subjected to predetermined processing such as sorting or stapling as necessary, and is stacked on the first discharge tray 153 or the second discharge tray 154. Further, the sheet sent to the re-feed conveyance unit 150 for double-sided copying is reversed here and conveyed again to the electrophotographic process unit 140, where an image is formed on the back side of the sheet, and discharged after fixing.

  The post-processing apparatus is provided with a first discharge basket 153 and a second discharge basket 154. The second discharge tray 154 receives the sheet on which the image is discharged from the image forming unit via a receiving discharge conveyance path 151 provided at the upper side of the post-processing apparatus, and the sheet is discharged as it is. It is a discharge part. The first discharge tray 153 is a discharge unit that discharges a sheet that has been post-processed by post-processing means 152 that is selectively mounted, such as staples and punches. In the post-processing apparatus, the sheet on which the image is formed is configured to be discharged from the first discharge tray 153 or the second discharge tray 154 selected by the user.

  The image forming apparatus illustrated in FIG. 7 is compatible with double-sided printing, and the configuration for that will be described below. The sheet on which the image is recorded is further conveyed upward by the conveying roller 155 through the fixing device 148 and passes through the switching gate 159. When the sheet discharge tray is set to the stacking tray 157 provided in the exterior of the image forming unit, the sheet is discharged to the stacking tray 157 by the reverse roller 156. On the other hand, when double-sided image formation or post-processing is designated, the sheet is discharged toward the stacking tray 157 by the reverse roller 156 once. In this case, the sheet is not completely discharged, and the reversing roller 156 is reversed while the sheet is held. The sheet is reversely conveyed in the reverse direction, that is, in the direction in which the refeed conveyance unit 150 and the post-processing apparatus that are selectively mounted for double-sided image formation and post-processing are mounted.

  At this time, the switching gate 159 is switched from a solid line state (upward) to a broken line state (downward). When performing double-sided image formation, the reversely conveyed sheet is supplied again to the image forming unit through the refeed conveyance unit 150 with another switching gate 158 facing upward (broken line). On the other hand, when post-processing is performed, the re-feeding transport unit 150 is transported to the post-processing apparatus with another switching gate 158 facing downward (solid line), and post-processing is performed. .

DESCRIPTION OF SYMBOLS 1 ... Document reading apparatus, 10 ... Housing, 11 ... Document platen glass, 12a, 12b, 12c ... Optical sensor for detecting presence / absence of document, 13 ... Document cover, 14 ... OC mat, 15 ... Switch, 16 ... Angle detection sensor , 17 ... control unit, 17a ... size determination unit, 17b ... adjustment unit, 18 ... initial value storage unit.

Claims (10)

A document size detection device for detecting the size of a document placed on a platen glass,
A set of a light-emitting element and a light-receiving element serving as a light source disposed in a predetermined positional relationship below the platen glass, and the light reflected from the light source is received by the light-receiving element. of the presence of a document at the corresponding position, a plurality of reflective optical sensor that detects, based on a comparison between the reflected light reception level and a predetermined threshold,
An adjustment unit for adjusting the light emission level for each of the plurality of reflective photosensors;
With respect to the angle of the document pressing whiteboard and the platen glass for pressing the original document over the platen glass, the initial value of the light receiving level of the reflected light in the state without the document, the reflective light on a plurality of angles An initial value storage unit stored for each sensor,
The adjustment unit, at the time of opening operation and / or closing operation of the document pressing whiteboard shows the document holder whiteboard and the light receiving level of the reflected light which the sensed by the reflection type optical sensor for each angle between the platen glass The adjustment of the light emission level of the reflective photosensor is performed only when the function satisfies a condition that is linearly related to the function indicated by the angle versus initial value stored in the initial value storage unit, and the condition is satisfied. If there is no document, the document size detection device does not adjust the light emission level of the reflection type photosensor .   The adjustment unit adjusts the light emission level only for the reflection type photosensors satisfying the condition among the plurality of reflection type photosensors during the opening operation and / or the closing operation of the document pressing white plate, 2. The document size detection apparatus according to claim 1, wherein the light emission level is not adjusted for a reflection type optical sensor that is not satisfied. The adjustment unit, the angle of the document pressing white plate and the platen glass light receiving level of the reflected light is detected at a predetermined angle, so as to coincide with the initial value for the predetermined angle, the reflective document size detection apparatus according to claim 1 or 2, characterized in that to adjust the emission level of the optical sensor. The adjustment unit, the difference between the received light level of the detected the reflected light when the predetermined angle angle of the plurality of said original pressing whiteboard and the platen glass, and the initial value for each of the predetermined angle of the plurality of 3. The document size detection apparatus according to claim 1, wherein the light emission level of the reflection type photosensor is adjusted so that the sum of squares is minimized. The adjustment unit adjusts a light emission level of the reflective photosensor based only on a detection result when an angle between the original pressing white plate and the original table glass is 45 degrees or less. 5. The document size detection apparatus according to any one of 1 to 4 . The adjustment unit determines whether or not the linear relationship is based only on a detection result when an angle between the original pressing white plate and the original table glass is 45 degrees or less. Item 6. The document size detection device according to any one of Items 1 to 5 . The adjustment unit determines whether or not the linear relationship is established after a predetermined period from the time when the initial value is stored or after the document size detection device is turned on after the initial value is stored. document size detection apparatus according to any one of claims 1 to 6, characterized in that. The adjustment unit, upon reception of the predetermined user operation, the document size detection apparatus according to any one of claims 1 to 6, characterized in that a determination of whether or not the linear relationship. Document reading apparatus having a document size detecting device according to any one of claims 1-8. An image forming apparatus comprising the document reading device according to claim 9 .

Images