JP2008263292A - Image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reader for detecting a document size normally without considering time to stabilize light of a lamp after turned on, and also preventing the eyes of a user from being irradiated with light from the lamp. <P>SOLUTION: The image reader comprises a document lighting lamp 110 which irradiates a document, an original table 117 where the document is mounted, and a CCD 116 which reads reflection of the light radiated from the document lighting lamp 110. Further, the image reader has a size detecting means of detecting the size of the document placed on the original table 117 using data read by the CCD 116, and a light quantity detecting means of detecting the quantity of light of the document lighting lamp 110. The size detecting means determines a threshold for determining a document from variation in quantity of light detected by the light quantity detecting means, and detects a range exceeding the threshold in a main scanning direction of the document as a document area range. A CPU 201 has functions as the size detecting means and light quantity detecting means. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image reading apparatus.

  2. Description of the Related Art Conventionally, image reading apparatuses such as copying machines, facsimile machines, and scanners have automatically detected the paper size (original size) of an original placed on an original table. There are the following methods for automatically detecting the paper size.

  That is, in the process of closing the document pressing member, the reading light source (xenon lamp, etc.) is turned on to irradiate the document surface, and the change in the reflected light is read by the reading element (CCD, etc.). Detect the size of. At this time, in the sub-scanning direction, the document size is determined by detecting the size of the document with a plurality of photosensors (Patent Document 1).

  In such a document size detection method, when detecting the size in the main scanning direction, the reading light source is turned on at the beginning of closing the document pressing member, and after waiting for a certain period of time so that the light amount of the reading light source is stabilized, the state is changed by the reading element. Is supposed to be sampled.

  Hereinafter, the paper size detection method will be described in detail with reference to the drawings.

  FIG. 12 is a diagram for explaining an outline when document size detection is performed in an image reading apparatus according to a conventional example. FIG. 13 is a diagram illustrating the opening / closing operation of the pressure plate when the document size is detected in the image reading apparatus according to the conventional example.

  FIG. 12 is a top view of the image reading apparatus. When the document pressing member (pressure plate) is opened to place the document 1203 on the document table 1201, the reading light source (lamp) 1202 is as shown in FIG. The document is moved to a position to detect the end of the document in the main scanning direction.

  Then, as shown in FIG. 13, a sensor 1302 that detects opening and closing of the pressure plate 1301 detects the position at which the pressure plate 1301 starts to close (the pressure plate 1301 is in the state (a)) at the timing when the sensor 1302 changes from on to off. .

  At this timing, the lamp 1202 is turned on, and after waiting for a predetermined time until the light quantity is stabilized, reading is performed by a reading element (CCD) (not shown). Then, the CCD reading value at the detection point shown in FIG. 14 is sampled at predetermined time intervals (for example, every 100 milliseconds) in the process of closing the pressure plate 1301, and the change in the reading state is examined.

  When the pressure plate 1301 is completely closed (the pressure plate 1301 is in the state shown in FIG. 13B), the change in the reading value at each detection point is examined, and as shown in FIG. 15, there is no change in the reading value. The detection point is detected as the document main scanning size (width).

Further, the size (length) in the sub-scanning direction is determined by the photo sensor 1204 arranged as shown in FIG. Finally, the paper size is determined by the width and length according to the table of FIG.
JP 2004-77991 A

  However, in the above-described conventional image reading apparatus, when the angle at which the pressure plate starts to be closed is high in order to wait until the lamp reaches a constant light amount after detecting that the pressure plate has started to be closed, irradiation from the lamp is performed. There was a problem that the user felt dazzling.

  On the other hand, when the angle at which the closing can be started is lowered, the pressure plate becomes less than the detectable angle before the lamp light quantity is stabilized (the pressure plate is closed), and there is a problem that the document size cannot be detected. .

  In addition, when the user quickly opens and closes the pressure plate, the pressure plate falls below the detectable angle before the lamp light quantity is stabilized, and the document size may not be detected normally.

  An object of the present invention is to provide an image reading apparatus that can detect the size of a document without considering the time from when the lamp rises until it stabilizes, and can prevent the light from the lamp from being irradiated to the user's eyes. It is to provide.

  In order to achieve the above object, an image reading apparatus according to claim 1 is a document table on which a document is placed, a light source that irradiates a document placed on the document table, and a reflection of light emitted by the light source. A reading element that reads light; a size detection unit that detects a size of a document placed on the document table using data read by the reading element; and a light amount detection unit that detects a light amount of the light source, The size detection unit determines a threshold value for determining the presence or absence of a document according to a change in the light amount detected by the light amount detection unit, and detects a document region range in the main scanning direction of the document based on the threshold value. It is characterized by that.

  According to the image reading apparatus of the present invention, it is possible to detect the document size without considering the time from the rise of the lamp to the stabilization, and to prevent the user's eyes from being irradiated with light from the lamp. .

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a configuration diagram of an image reading apparatus according to an embodiment of the present invention.

  In FIG. 1, an image reading apparatus 100 includes an optical system including an original illumination lamp (light source) 110 and mirrors 111 to 113, a motor 114 for driving the optical system, a lens 115, a CCD (reading element) 116, an original table 117, an original. A pressure plate 118 as a pressing member is provided. A reference white plate 119 having a white lower surface is disposed at the end of the document table 117.

  The pressure plate 118 holds a document placed on the document table 117. When reading one document placed on the document table 117, the optical system including the document illumination lamp 110 and the mirrors 111 to 113 is driven by the motor 114 in the direction indicated by the arrow 120. Then, the image of the document placed on the document table 117 is scanned, imaged on the CCD 116 via the lens 115, and read.

  FIG. 2 is a control block diagram of the image reading apparatus according to the embodiment of the present invention.

  The image reading apparatus 100 includes a CPU 201, an image processing unit 202 connected to the CPU 201, a motor driver unit 203, and a sensor signal input unit 204. The CPU 201 is connected to the CCD 116, and an image memory 205 is connected to the image processing unit 202.

  The CPU 201 includes a program storage ROM (not shown), a work RAM, and the like. The motor driver unit 203 is a driver circuit for driving the motor 114. The sensor signal input unit 204 captures signals from various sensors into the CPU 201.

  The CPU 201 performs document reading control using the motor driver unit 203 and the sensor signal input unit 204. An image signal imaged on the CCD 116 by the lens 115 is converted into digital image data, subjected to various kinds of image processing by the image processing unit 202, and written (stored) in the image memory 205.

  The CPU 201 of the present embodiment functions as a size detection unit that detects the size of the document placed on the document table 117 using the data read by the CCD 116 and a light amount detection unit that detects the light amount of the document illumination lamp 110. . The light quantity detection means has a function of detecting the quantity of light that changes over time.

  Then, the size detection unit determines a threshold value for determining the presence or absence of the document according to the change in the light amount detected by the light amount detection unit, and detects a range exceeding the threshold in the main scanning direction of the document as a document region range. .

  FIG. 3 is a block diagram of the image processing unit in FIG.

  In FIG. 3, the image processing unit 202 includes an amplifier circuit 301, an A / D converter 302, and a shading correction circuit 303.

  In the process of scanning a document image, an analog image signal is output from the CCD 116 for each line of reading. After being amplified by an amplifier circuit 301, the signal is converted into an 8-bit digital signal by an A / D converter 302. Converted.

  The shading correction circuit 303 performs black level correction and white level correction (shading correction) on the image signal. Thereafter, the corrected image data is written into the image memory 205. The above processing is performed for the document image area to form a scanned image of the document.

  FIG. 4 is a diagram for explaining the arrangement of reference white plates when performing document size detection in the image reading apparatus of FIG.

  In FIG. 4, the reference white plate 119 is arranged outside the document area 401 in the main scanning direction (vertical direction in FIG. 4) as shown in FIG. 4 at the position where the document size is detected (size detection position in FIG. 4). ing. The photo sensor 402 is also arranged in the same manner as the conventional example.

  The CCD 116 reads the main scanning area including the reference white plate 119, and reads the white level by the reference white plate 119 and the original in the original area. Then, document size detection control is performed based on the opening / closing information of the pressure plate 118, the white level by the reference white plate 119, and document reading information.

  This control will be described below with reference to FIGS.

  FIG. 5 is a flowchart showing a procedure of document size detection processing executed by the image reading apparatus of FIG. FIG. 6 is a diagram for explaining the opening / closing operation of the pressure plate when the document size is detected in the image reading apparatus of FIG. FIG. 7 is an enlarged view of the open / close sensor and the close sensor in FIG. 6. FIG. 8 is a diagram showing the relationship between the amount of light (white level) of the reference white plate in FIG. 1 and time. FIG. 9 is a diagram showing a threshold level (threshold) for determining the presence or absence of a document determined from the white level in FIG.

  The document size detection process in FIG. 5 is executed by the CPU 201 in FIG.

  In FIG. 5, first, it waits for the pressure plate 118 to be lifted in a standby state (step S101). When the pressure plate 118 is lifted to the position shown in FIG. 6A, the document illumination lamp 110 is moved to the document size detection position as shown in FIG. 4 (step S102). This state is a state in which the pressure plate 118 is “open”.

  In the process of closing the pressure plate 118, when the pressure plate 118 is in the position of FIG. 6B, the open / close sensor (open / close detection means) 601 is turned on to detect the start of closing of the pressure plate 118 (step S103). (FIG. 7A).

  At the same time, the document illumination lamp 110 is turned on (step S104), and document size detection processing is performed until the pressure plate 118 is in the “closed” state (step S105). In the document size detection, the reference white plate 119 and the document 602 are sampled at regular intervals (in this embodiment, every 10 milliseconds).

  Then, as the document illumination lamp 110 rises, the read value of the reference white plate 119 becomes a graph as shown in FIG. 8, so that when the white level is sampled at regular intervals, it becomes like the block of FIG.

  Based on this, a threshold level for determining the presence or absence of a document is determined (step S106). The width of the original 602 is detected by setting the threshold level to 70% of the white level. When the pressure plate 118 reaches the position shown in FIG. 6C, the closed sensor 603 detects that the pressure plate 118 is closed (FIG. 7B). At the same time, the document illumination lamp 110 is turned off.

  The document width is detected by referring to the detection points in FIG. 14 in the main scanning direction. P0 in FIG. 14 is a photosensor that determines the sub-scanning size. The detection point has a certain area, and the reading levels in the area are added and averaged to obtain the reading value of the detection point (step S107).

  If the determination of the entire detection point is not completed (NO in step S108), the process waits for 10 milliseconds (step S109). If the determination of the entire detection point has been completed (YES in step S108), the process proceeds to step S110.

  First, at each sampling interval, when the reading value at each detection point exceeds the threshold level calculated from the white level of the reference white plate 119 (NO in step S110), it is determined that there is a document (step S111), and Save the result. Further, when it is below, it is determined that there is no document (step S112), and the result is stored.

  When the pressure plate 118 is in the “closed” state (YES in step S105), the document illumination lamp 110 is turned off (step S114), the document size is determined (step S115), and this process is terminated.

  To determine the document size, first, the document presence / absence determination history of each detection point is searched, and it is determined that there is no document at the detection point that has changed from “no document” to “present”. Then, the document size is determined using the maximum width of the detection point where the document is finally present.

  For example, as shown in FIG. 10, sampling is performed from time T <b> 1 to T <b> 10 when T <b> 1 detects the start of closing with the opening / closing sensor 601 and T <b> 10 detects the “closed” state with the closing sensor 603. Then, it is determined that there is no original at detection points P4 and P5 where the presence or absence of the original has changed. Next, the document size is determined using the position P3 of the maximum width where the document is present.

  The final document size is determined as shown in FIG. In the case of the example of FIG. 10, when the photo sensor P0 detects the presence of a document, it is determined as “B5R” size, and when P0 detects that there is no document, it is determined as “B6” size.

  If the closed sensor 603 cannot detect that the pressure plate 118 is closed even if the number of sampling times exceeds 500 (5 seconds) (YES in step S113), the document illumination lamp 110 is turned off at that time (step S116). ). Then, the document size is set to “unknown” (step S117), and this process ends.

  As described above, the document level is determined immediately after the pressure plate 118 starts to be closed by changing the threshold level for determining the presence or absence of the document according to the amount of light of the document illumination lamp 110 that samples the reference white plate 119 arranged outside the document area. Size detection can be performed.

  FIG. 11 is a diagram for explaining the arrangement of photosensors when performing document size detection in the image reading apparatus of FIG.

  In the example of FIG. 4, the light quantity measurement is performed using the reference white plate 119 arranged outside the document area. However, as another embodiment of the light quantity measurement, as shown in FIG. The light quantity may be measured using a photosensor 1101 arranged in the section.

  In this case, the current light amount is detected by A / D converting the signal output from the photosensor 1101. Then, by sampling the light amount by the photo sensor 1101 every predetermined time, it is possible to perform the same document size detection control as when the reference white plate 119 is used. There is also a photo sensor 1102 for detecting the size of the document in the sub-scanning direction (length direction).

1 is a configuration diagram of an image reading apparatus according to an embodiment of the present invention. 3 is a control block diagram of the image reading apparatus according to the embodiment of the present invention. FIG. FIG. 3 is a block diagram of an image processing unit in FIG. 2. FIG. 2 is a diagram for explaining the arrangement of reference white plates when performing document size detection in the image reading apparatus of FIG. 1. 3 is a flowchart illustrating a procedure of document size detection processing executed by the image reading apparatus of FIG. 2. FIG. 3 is a diagram for explaining opening and closing operations of a pressure plate when performing document size detection in the image reading apparatus of FIG. 1. FIG. 7 is an enlarged view of the open / close sensor and the close sensor in FIG. 6. It is a figure which shows the relationship between the light quantity (white level) of the reference | standard white board in FIG. 1, and time. FIG. 9 is a diagram illustrating a threshold level for determining the presence or absence of a document determined from the white level in FIG. 8. 10 is a chart showing document presence / absence determination of document size detection points over time. FIG. 2 is a diagram illustrating the arrangement of photosensors when performing document size detection in the image reading apparatus of FIG. 1. FIG. 10 is a diagram illustrating an outline when performing document size detection in an image reading apparatus according to a conventional example. It is a figure explaining the opening / closing operation | movement of a pressure plate at the time of performing document size detection in the image reading apparatus which concerns on a prior art example. FIG. 4 is a diagram illustrating detection points for performing document size detection in the image reading apparatus. FIG. 10 is a diagram for explaining determination of whether or not a document exists when performing document size detection in an image reading apparatus according to a conventional example. 6 is a chart showing a relationship between a document size detection point and a detected document size.

Explanation of symbols

110 Document illumination lamp (light source)
116 CCD (reading element)
117 Document platen 118 Pressure plate (document holding member)
119 Reference white plate 201 CPU (size detection means, light quantity detection means)
601 Open / close sensor (open / close detection means)
603 Close sensor

Claims (5)

An original table on which an original is placed;
A light source for irradiating a document placed on the document table;
A reading element for reading reflected light of the light irradiated by the light source;
Size detection means for detecting the size of the document placed on the document table using data read by the reading element;
A light amount detecting means for detecting the light amount of the light source,
The size detection unit determines a threshold value for determining the presence or absence of a document according to a change in the light amount detected by the light amount detection unit, and detects a document region range in the main scanning direction of the document based on the threshold value. An image reading apparatus.   2. A reference white plate disposed outside an area of a document in a main scanning direction, wherein the light amount detection unit detects a light amount from data obtained by reading the reference white plate with the reading element. The image reading apparatus described.   The image reading apparatus according to claim 1, further comprising: a photosensor that measures a light amount of the light source, wherein the light amount detection unit detects a light amount from an output of the photosensor.   A document pressing member that presses the document placed on the document table; and an opening / closing detection unit that detects opening / closing of the document pressing member. The opening / closing detection unit detects a position at which the document pressing member starts to close. 4. The image reading apparatus according to claim 1, wherein the light amount is detected by the light amount detecting means.   5. The image reading apparatus according to claim 1, wherein the light amount detection unit detects a light amount that changes over time.

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