JPH10257255A - Original size detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a detector to detect the size of an original even when the original whose size is hardly discriminated is placed on an original platen. SOLUTION: Image data of one line read in the step S4 are sequentially checked from image data corresponding to upperstream pixels in the main scanning direction for each pixel and discriminated as to whether or not parts of the image data whose reference density is P or below and that are consecutive by a reference data number Q or over are in existence in the image data (step S5). In the case that parts of the image data where white level data are consecutive for the reference data number Q or over are detected (YES in the step S5), it is discriminated that the part detected at first is an end ridge of the original set to the original platen this side in the main scanning direction, and the size of the original is detected in the step S6. In the case that the discrimination in the step S5 is negated, the reference density P is increased by a value α in the step S8. Then the processing returns to the step S5 and whether or not parts of the image data whose reference density is a newly set criterion P or below and that are consecutive by a reference data number Q or over are in existence in the image data is discriminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document size detecting device which is applied to a document reading device capable of reading a document and detects the size of a document set on a document table.

[0002]

2. Description of the Related Art Conventionally, copiers and facsimile apparatuses capable of reading an image of a document set on a transparent document table having a function of detecting the size of a document set on the document table have been widely known. Have been. Various techniques are employed for detecting the size of a document.For example, in the case of a digital image reading device, when a document is set on a platen and a document cover for covering the document is closed, An original size is detected by reading an image of one line along the main scanning direction and detecting an edge of the original in the main scanning direction based on the read image data.

[0003] The detection of the document size in the digital image reading apparatus will be described in more detail. A light source for illuminating and scanning a document set on the document table is provided below the document table, and this light source is waiting at a predetermined home position. When the document is set on the document table and it is detected that the document cover is closed, the light source emits light and the document and the document table are irradiated with light.
More specifically, the light source emits light after the user starts closing the document cover and before the document cover contacts the document. Therefore, light applied to the document is reflected by the document, but light applied to portions other than the document is radiated to the outside.

The light reflected by the original is incident on a CCD sensor and converted into analog image data corresponding to the density of the original image. Analog image data from the CCD sensor is converted into digital image data representing the pixel density in, for example, 256 gradations of 0 to 255 (FFh).
In addition, since the reflected light is not incident on the portion other than the original, it is represented by a value close to 255 (FFh) or 255 (FFh).

Next, the digital image data of one line obtained as described above is examined sequentially along the main scanning direction, and first, a predetermined reference density value (for example, "1") is determined.
00 ") is equal to or smaller than the reference length K (for example, 3 m).
A portion that is continuous over the number of data corresponding to m) is detected. Generally, an image is often not formed near the edge of a document, so that the detected portion can be regarded as the edge of the document in the main scanning direction.

Referring to FIG. 5, since the width of the original in the main scanning direction differs depending on the size of the original, the edge of the original platen on one line (indicated by a two-dot chain line) read as described above. La and L from the document to the edge of the document in the main scanning direction
b and Lc differ depending on the document size. Specifically, in the case of an A4 (Japanese Industrial Standard A row 4) size document, the length of the portion other than the document is La,
In the case of the size 4 (Japanese Industrial Standard B column No. 4), the length Lb of the portion other than the original is shorter than the length La. Also,
In the case of the A3 (Japanese Industrial Standards A row 3) size, the length Lc of the portion other than the original is shorter than the length Lb.

Therefore, the document size can be determined by counting the number of data from the first image data in the main scanning direction to the image data corresponding to the pixel at the edge of the document in the image data of one line.

[0008]

However, among the originals set on the original platen, one line of image data obtained as described above has a high density of the background of the paper, such as a newspaper original. There is a possibility that image data having a density equal to or lower than the reference density value is not included. In this case, since the edge of the document cannot be detected, the size of the document cannot be detected.

In the case where an image is recorded up to the vicinity of the edge of the original in one read line, as in the case of an A4 original shown in FIG. There is no continuous part more than the number of data corresponding to. Therefore, also in this case, the document size cannot be detected. Therefore, an object of the present invention is to
An object of the present invention is to provide a document size detecting device capable of detecting a document size even if the document has a high background density or a document on which an image is recorded up to the vicinity of an edge.

[0010]

According to a first aspect of the present invention, there is provided a document size detecting apparatus for detecting a size of a document set on a document table. A light source for illuminating and scanning the document set in the document, data generating means for generating image data corresponding to the document density based on light generated from the light source and reflected by the document, and data generated by the data generating means. Detecting means for detecting a portion corresponding to a predetermined condition from the image data, a condition changing means for changing the predetermined condition to be relaxed when a detection signal is not output from the detecting means, and And a size determination unit for determining the size of the document based on the output of the document.

In the invention according to the second aspect, the portion corresponding to the predetermined condition is such that when image data generated by the data generating means is examined in a predetermined order, an image having a density equal to or less than a reference density value is first determined. If the data is a portion that is equal to or greater than the reference data number, and the detection means does not output a detection signal, the condition changing means increases the reference density value by a predetermined value or sets the reference data number to a predetermined value. 2. The document size detecting device according to claim 1, wherein at least one of the data number changing processes for reducing the number of data is performed.

According to the first aspect of the present invention, a portion corresponding to a predetermined condition is detected from the image data generated by the data generating means, and a document size is determined based on the detected portion. You. The portion corresponding to the predetermined condition is, as described in claim 2,
First, a portion where image data below the reference density value is continuous over the number of reference data, and this portion corresponds to the document edge.
Since the position of the document edge on the document table varies depending on the document size, when the document edge is detected, the document size can be determined based on the position of the document edge.

When the portion corresponding to the predetermined condition is not detected by the detecting means, the predetermined condition is relaxed by the condition changing means. Specifically, when the detection signal is not output from the detection means as in the configuration of the second aspect, the reference density value is increased by a predetermined value. As a result, the original set on the platen
For example, even for a halftone original such as a newspaper, the edge of the original can be detected, so that the size of the original can be detected.

When the detection signal is not output from the detection means, the reference data number is reduced by a predetermined number by the condition changing means, so that even if the document has an image recorded near the edge of the paper, The edge of the original can be detected. According to a third aspect of the present invention, the light source is provided so as to be movable in a predetermined direction below the document table, and displaces the light source by a predetermined distance when a detection signal is not output from the detection means. 3. The method according to claim 1, further comprising means.
The document size detection device according to the item (1).

According to the third aspect of the invention, when the detecting means does not detect a portion corresponding to the predetermined condition, the position of the light source is shifted and the reading line of the original image is changed. Then, the document size detection is performed based on the image data of the new reading line. This allows
Since the line on which the image is recorded up to the edge of the document is accidentally read, the risk that the edge of the document is not detected and the size of the document is not detected can be eliminated.

[0016]

An embodiment of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view illustrating an internal configuration of an image forming apparatus to which a document size detecting device according to an embodiment of the present invention is applied. FIG. 2 is a partial perspective view of the image forming apparatus shown in FIG.

This image forming apparatus is a so-called multifunction machine having a copying function, a facsimile function and a printer function, and includes an apparatus main body 1 and a scanner section 2 provided above the apparatus main body 1 for reading a document image. , An automatic document feeder (hereinafter, referred to as “AD
F ". ) 3 and a recording paper discharge unit 4 for receiving a recorded paper on which an image is recorded and discharged in the apparatus main body 1. Also, on the near side of the upper surface of the scanner unit 2,
As shown in FIG. 2, an operation unit 5 having various operation keys such as a display unit 51, a numeric keypad 52, and a start key 53 is arranged.

The ADF 3 is provided above the scanner unit 2 and is for automatically supplying a document to a transparent document table 21 disposed on the upper surface of the scanner unit 2. A
The DF 3 also serves as a cover for the document table 21, and the front side is opened upward, centering on the rear side, so that the document can be manually placed on the document table 21 (see FIG. 2). Also, as shown in FIG.
3 is provided with an open / close detection switch 80 for detecting the open / close state of the switch 3. The open / close detection switch 80 is turned off when the angle of the ADF 3 with respect to the upper surface of the scanner unit 2 exceeds a predetermined angle when the ADF 3 is opened and closed, and is turned on when the angle is smaller than the predetermined angle. .

An original setting surface 31 on which an original to be read by the scanner unit 2 is set is provided on the upper surface of the ADF 3.
Are formed. In FIG. 1, a document inlet 32 is formed on the left side of the document setting surface 31, and a document outlet 33 is formed on the right side of the document setting surface 31. Further, the ADF 3 is provided with a transport belt 34 for arranging a document at a predetermined position on the document table 21. The transport belt 34 is provided so as to face the document table 21 when the ADF 3 is closed.
The surface opposite to is white.

When a document is set on the document table 21 using the ADF 3, the document is set on the document setting surface 31 with the ADF 3 closed, and a start key 53 provided on the operation unit 5 is pressed. Press. Then, the documents set on the document setting surface 31 are taken in one by one from the document inlet 32, and are arranged on the document table 21 by the transport belt 34. After the document image is read by the scanner unit 2, the document table 21 is conveyed by the transport belt 34.
And is discharged from the document discharge port 33. At this time, the size of the document is detected based on, for example, the outputs of a plurality of reflective sensors arranged on the document setting surface 31 of the ADF 3.

On the other hand, when the original is set on the original table 21 manually, the front side of the ADF 3 is
Expose 1 Then, the document is transferred to, for example,
After the document is set in accordance with the left rear corner of the ADF 3, the front side of the ADF 3 is pulled down and the document table 21 is covered with the ADF 3. Thereafter, when the start key 53 is pressed, the document image is read by the scanner unit 2. At this time, the size of the document set on the document table 21 is detected by executing a document size detection process described later.

The scanner section 2 is provided with a light source 22 for illuminating a document on a document table 21. Light source 22
Is constituted by, for example, a fluorescent tube elongated in the main scanning direction (the front-back direction in FIG. 1), and is configured to be reciprocally displaceable below the document table 21 in the sub-scanning direction (left-right direction in FIG. 1). . The light generated from the light source 22 is
Is reflected by The reflected light is reflected by a first reflecting mirror 23 that moves together with the light source 22, and its optical path is turned back by a second reflecting mirror 25 and a third reflecting mirror 26 fixed to a moving frame 24 before being incident on a CCD sensor 27. Is done.
The CCD sensor 27 generates analog image data based on the incident light.

The apparatus main body 1 is provided with a printing unit 10 for outputting an image on a predetermined sheet. Printing unit 10
1 includes a cylindrical photoreceptor 11 that is rotated at a constant speed clockwise in FIG. 1 at the time of image output, a main charger 12, a developing device 13, and a transfer roller 14 that are sequentially arranged along the rotation direction of the photoreceptor 11. And the main charger 1
A laser scanning unit 15 that exposes the surface of the photoconductor 11 with laser light is provided between the developing unit 2 and the developing device 13.

The photoreceptor 11 is rotated and driven, and the surface of the photoreceptor 11 uniformly charged by the main charger 12 is exposed by a laser beam from the laser scanning unit 15. The laser scanning unit 15 corresponds to image data created by the scanner unit 2 as described above, image data input via a communication line, and image data input from an external device such as a personal computer (not shown). The surface of the photoreceptor 11 is exposed by the modulated laser light. As a result, an electrostatic latent image corresponding to the image to be output is formed on the surface of the photoconductor 11. The photoreceptor 11 on which the electrostatic latent image is formed next faces the developing device 13, and the electrostatic latent image is developed into a toner image. As the photoconductor 11 further rotates, the toner image formed on the surface of the photoconductor 11 faces the transfer roller 14.

On the other hand, the apparatus main body 1 is provided with paper feed cassettes 61 and 62 each capable of storing a plurality of sheets. In synchronization with the above-described toner image forming operation in the printing unit 10, a sheet according to the document size and the copy magnification is fed out onto the transport path 63 from one of the sheet feeding cassettes 61 and 62. The sheet fed out onto the conveyance path 63 is temporarily stopped by the registration roller 64, and then fed toward the photoconductor 11 at a timing when the toner image on the surface of the photoconductor 11 is aligned with the transfer roller 14. Then, by the operation of the transfer roller 14, the photosensitive member 1
The toner image on one surface is transferred to the fed sheet.

The sheet on which the toner image has been transferred is heated roller 1
6 and a fixing device 18 including a pressure roller 17.
The toner on the sheet is fixed on the sheet by heating by the heat roller 16 and pressing by the pressure roller 17. The sheet after the fixing process is discharged by a discharge roller 19 to a recording sheet discharge section 4 formed on the upper surface of the apparatus main body 1. FIG.
FIG. 2 is a block diagram showing an electrical configuration of the apparatus main body 1.

The apparatus main body 1 has a CPU 70 that controls the respective parts of the apparatus main body 1, the scanner section 2 and the operation section 5 in a comprehensive manner.
Is provided. A memory such as a ROM 71 and a RAM 72 is connected to the CPU 70.
Executes a document size detection process described later according to a program stored in the ROM 71. At this time, RAM
Reference numeral 72 functions as a work area for temporarily holding various data.

The scanner unit 2 is connected to the CPU 70 via the image processing unit 73. The image processing unit 73 converts the analog image data input from the scanner unit 2 (CCD sensor 27) into, for example, 256 to 0 to 255 (FFh).
The image data is converted into digital image data representing the density of each pixel by gradation. After performing various processes on the digital image data, the image processing unit 73 converts the processed image data into a CP.
Input to U70.

The CPU 70 is also connected to an open / close detection switch 80 for detecting the open / close of the ADF 3 (see FIG. 1). The CPU 70 starts the document size detection processing based on the open / close detection signal (ON / OFF signal) from the open / close detection switch 80, and sends the document to the document table 21 (see FIG. 1) based on the image data from the image processing unit 73. The size of the set document is detected.

The CPU 70 is further connected to a facsimile function unit 74. The facsimile function unit 74 includes a modem 75 for demodulating received image data and modulating image data to be transmitted, and an external communication line 77.
(Network Cont) for connecting the modem and the modem 75
(rol unit) 76 is included. The image data received via the external communication line 76 is transmitted to the modem 75 and the NCU 7
6 to the CPU 70. The device body 1
External equipment such as a personal computer (not shown)
Is connected, the image data created by the personal computer or the like is input to the CPU 70.

The CPU 70 has a facsimile function unit 74,
The image data input from the scanner unit 2 and an external device such as a personal computer is supplied to the printing unit 10 to output an image based on the input image data on a predetermined sheet. FIG. 4 is a flowchart showing the flow of the document size detection process. This document size detection process is a process for automatically detecting the size of a document placed on the document table 21. The user opens the ADF 3 and manually sets the document on the document table 21. Will be executed when

When a document is manually set on the document table 21, if the size of the set document is not determined even though the document always exists on the document table 21,
It is necessary to specify the document size, which is troublesome for the user. Therefore, in the document size detection process described below, if a document whose document size is difficult to determine is set, the size of the document is determined as much as possible, even if it takes a long time to detect the document size. ing. This reduces the frequency with which the user must specify the document size.

It is to be noted that the original is placed on the platen 21 using the ADF 3.
When the document is automatically set, the document size is detected based on, for example, the output of a reflection sensor (not shown) arranged on the document setting surface of the ADF 3. Referring to FIG. 4 while referring to FIG. 3, when the ADF 3 is opened and the open / close detection switch 80 is turned off, the CPU 70 determines that the original is manually set on the original platen 21, and outputs a flag described later. F is reset (step S1), and initial values of a reference density value P and a reference data number Q, which are determination references in the determination in step S4 described later, are set (step S2). In the initial value setting in step S2, the reference density value P is set to, for example, “100”. The reference data number Q is set to a data number corresponding to, for example, a reference length of 3 (mm).

When the initial values of the reference density value P and the reference data number Q are set, it is next determined whether or not the open / close detection switch 80 has been turned on (step S3). When the user who has finished setting the original closes the ADF 3, the ADF
When the angle formed by 3 with the upper surface of the scanner unit 2 becomes a predetermined angle, the open / close detection switch 80 is turned on. When the open / close detection switch 80 is turned on, the determination in step S3 is affirmed, and the scanner unit 2 reads one line of the document along the main scanning direction (step S3).
4). More specifically, the light source 22 provided in the scanner unit 2 is located at a predetermined home position (the position shown in FIG. 2) in advance, and emits light when the open / close detection switch 80 is turned on. That is, before the lower surface of the ADF 3 (the transport belt 34) contacts the original, the light source 22
(See FIG. 1) is emitted. Therefore, light applied to the document is reflected by the document, and light applied to portions other than the document is radiated to the outside.

As a result, with respect to the original portion, 256 pixels of 0 to 255 (FFh) are provided for each pixel based on the reflected light.
The image data of each pixel is represented by “255 (FFh)” because the light from the light source 22 is not reflected in a portion other than the document. One line of image data generated in this manner is stored in, for example, a RAM.
72.

Next, the image data of one line stored in the RAM 72 is stored on the upstream side in the main scanning direction for each pixel (FIG. 1).
Are read out in order from the image data corresponding to the pixel on the near side (in FIG. 2). Then, the reference density value P (= “100”)
It is determined whether or not a portion where the following image data continues for the reference data number Q (= the number of data corresponding to 3 mm) or more exists in one line of image data (step S5).

The reference density value P is, for example, 8 bits (25 bits).
This is a threshold value at which image data represented by (6 gradations) is divided into two data of high-level data (black data) and low-level data (white data). That is, when the image data is equal to or less than the reference density value P, the image data is regarded as white data, and when the image data is larger than the reference density value P, the image data is regarded as black data. Therefore, in step S5, after the 8-bit image data stored in the RAM 72 is binarized, it is determined whether or not there is a portion where the white data continues for the reference data number Q or more.

When a portion where the white data continues for the reference data number Q or more is detected in the image data included in one line (YES in step S5), the CPU 70 sets the first detected portion on the document table 21. The document size is determined to be the front edge in the main scanning direction of the document, and the document size is detected in step S6, and the document size detection process ends. In step S6, the document size is specifically detected as follows. As described with reference to FIG. 5 in the related art section, the lengths La, Lb, and Lc of portions other than the original on one line (indicated by a two-dot chain line in FIG. 5) differ depending on the original size. Therefore, the ROM 71 stores the length La,
The numbers of image data respectively corresponding to Lb and Lc are stored in advance in association with the document sizes A4, B4 and A3, respectively.

When the edge of the document is detected in step S5,
The number of data from the image data corresponding to the pixel at the most upstream side in the main scanning direction to the image data corresponding to the pixel at the edge of the document is counted by, for example, a counter provided in the RAM 72. Then, the number of image data counted by this counter is compared with the number of image data stored in the ROM 71 to determine the document size. For example, if the number of image data counted by the counter is substantially equal to the number of data corresponding to the length La, it is determined that the document set on the document table 21 is A4.

On the other hand, an original (halftone original) having a relatively high density of the background of the paper, such as a newspaper, is
Is set, there is a possibility that the read image data of one line does not include any image data having the reference density value P or less. If there is no image data of the reference density value P or less in the image data of one line, the determination in step S5 is negative.

If the determination in step S5 is negative, it is next determined whether or not the reference density value P is equal to or greater than a predetermined upper limit value _Pmax (for example, "150") (step S5).
7). At this time, the reference density value P is the initial set value “10”.
Since it is "0", the determination in step S7 is denied, and the routine goes to step S8. In step S8, the reference density value P is increased by a value α (for example, “20”). Step S
In step S8, when the reference density value P is increased by the value α,
5 to return to the newly set reference density value P (= “12
0 ") is determined as to whether or not a portion where the image data below the reference data number Q is continuous exists in the image data of one line.

As described above, the processing of steps S5, S7 and S8 is repeated, and the value of the reference density value P serving as the determination reference in step S5 is gradually increased. Thus, even if the set document is a halftone document, the background of the document is determined to be white in step S5, and the edge of the document can be detected. Therefore, the document size can be detected in step S6.

However, like the A4 original shown in FIG.
In one line read by the scanner unit 2 (for example, a line indicated by a two-dot chain line in FIG. 5), when an image is recorded up to the vicinity of the edge of the original, a portion where the white data is continuous for the reference data number Q or more. Does not exist. At this time,
Even if the processing of steps S5, S7 and S8 is repeated and the reference density value P is gradually increased,
The determination in step S5 is not affirmative, and the document size cannot be detected.

If the reference density value P is equal to or greater than the predetermined upper limit _Pmax without affirming the determination in step S5, the determination in step S7 is affirmed and the process proceeds to step S9. Then, in step S9, it is determined whether or not the reference data number Q is equal to or less than a predetermined lower limit Q _min (for example, the number of data corresponding to 1 mm).
At this time, since the reference data number Q is initially set to the data number corresponding to 3 mm, the determination in step S9 is denied, and the process proceeds to step S10.

In step S10, the reference data number Q is reduced by the data number β (for example, the number of data corresponding to 1 mm). When the reference data number Q is reduced by the data number β in step S10, the process returns to step S5, and the image data having the reference density value P or less is newly set as the reference data number Q (= the number of data corresponding to 2 mm). It is determined whether or not the continuous portion exists in the pixels of one line. Then, the reference data number Q is set to a predetermined lower limit value Q.
Steps S5, S9 and S10 are repeated until the value becomes _min or less.

As described above, when the reference density value P is equal to the upper limit value P _max
If the determination in step S5 is not affirmative even if the reference data number Q is increased to the predetermined lower limit Q
reduced to _min . Thus, even if the document has an image recorded near the edge of the sheet, the edge of the document can be detected, and the size of the document can be detected.

Further, as described above, the reference density value P is raised to the upper limit value _Pmax , and the reference data number Q is reduced to the lower limit value Qmax.
_If the determination in step S5 is not affirmed even if the value is reduced to _min , the determination in step S9 is denied, and the process proceeds to step S11. Then, in step S11, 1
The state of the flag F indicating that the second image reading has been executed is checked.

At this time, since the flag F is set to 0, the determination in step S11 is denied, and the flag F is set to 1
Then, the light source 22 provided in the scanner unit 2 is moved from the home position shown in FIG. 2 by a predetermined distance, for example, in the sub-scanning direction (step S13). The display unit 5 arranged on the operation unit 5
For example, a message such as "Please open the ADF 3" is displayed on the screen 1 (step S14). The user of the image forming apparatus views the display and opens the ADF 3.

When the ADF 3 is opened by the user and the open / close detection switch 80 is turned off, the process returns to step S2, and the initial values are set again for the reference density value P and the reference data number Q. Then, the processing after step S3 is executed. When it is detected in step S3 that the open / close detection switch 80 has been turned on, the original is read in step S4. At this time, the above-described step S1
Since the position of the light source 22 has been changed in Step 3, an original image on a line different from the first reading line (for example, a line indicated by a two-dot chain line in FIG. 5) is read. Then, based on the image data obtained by the second reading,
Step S5 and steps S7 to S10
Is repeated. If a document edge is detected during this process, the determination in step S5 is affirmed, and the document size is determined based on the detected position of the document edge (step S6).

On the other hand, the processing of steps S5 and S7 to step S10 are repeated, when the reference number of data Q is also lowered to the lower limit value Q _min, which can not detect the document edge is the determination of step S9 Affirmed,
In step S11, the state of the flag F is checked. At this time, since the flag F is set to 1, the determination in step S11 is affirmed, and the process ends without detecting the document size.

As described above, first, the light source 22 reads one line of the original image at the home position, and the image data of the initial reference density value P or less is included in the read one line image data. It is checked whether or not there is a continuous portion equal to or more than the reference data number Q. When image data corresponding to pixels on the upstream side (front side in FIG. 1) in the main scanning direction is examined in order, the first detected portion is regarded as the document edge, and the document size is detected. .

On the other hand, when there is no portion where the image data having the initial reference density value P or less is continuous beyond the initial reference data number Q, the reference density value P and the reference data number Q are changed, and the edge of the document is detected. Critical criteria are relaxed. For example, by raising the reference density value P, even if the document set on the document table 21 is a document such as a newspaper having a relatively high density of the background of the paper, the edge of the document can be detected. Further, since the reference data number Q is reduced, the edge of the document can be detected even if the document has an image recorded near the edge of the sheet. Therefore, the possibility that the document size cannot be detected due to the inability to detect the edge of the document is reduced.

The reference density value P is equal to the upper limit value P._maxUp to
And the reference data number Q is lower limit value Q _minLowered to
If the document edge is not detected, the position of the light source 22 is
Is changed, and the reading line of the document image is changed. So
Then, based on the image data of the new reading line,
Size detection is performed. As a result, the edge of the document
Because the line on which the image was recorded was read in
It is possible to eliminate the possibility that the edge of the original cannot be detected.
it can.

In the configuration described above, for example, the case where an A4 size original is set with its longitudinal direction along the main scanning direction (so-called A4 vertical setting) and the case where an A3 size original is set are described. The position of the edge on the near side of the original in the main scanning direction becomes the same, and whether the original is an A4 original or A3
I can't tell if it's a manuscript. The same applies to a case where a vertically set B5 (Japanese Industrial Standard B column No. 5) size document is set vertically and a case where a B4 size document is set.

Therefore, below the platen 21, for example,
The positions where the reflection sensors are not turned on when the A4 is set vertically and turned on when the A3 is set vertically are not turned on when the B5 is set vertically,
It is preferable that it is arranged at a position where it is turned on when it is set. Although the description of one embodiment of the present invention is as described above, the present invention is not limited to the above-described embodiment. For example, in the above-described embodiment, the processing in the case where the position of the light source (read line) is changed only once has been described. However, the change of the light source position is not limited to one time, and may be changed two or more times.

In the above embodiment, the reference density value,
Although the processing in the case where all of the reference data number and the light source position are changed has been described, only one of these conditions may be changed, or the two conditions may be arbitrarily combined. It may be configured to be changed. Further, in the above-described embodiment, the configuration is such that the number of reference data is changed after the reference density value is changed to the upper limit value, but the reference density value is changed after the reference data number is changed to the lower limit value first. May be changed.

In the above-described embodiment, the case where the document size detecting apparatus according to the present invention is applied to a multifunction machine having a copying function, a facsimile function and a printer function has been described as an example. The present invention can be applied to any apparatus having image reading means, such as a copier, a facsimile machine, and the like. In addition, various changes can be made within the scope described in the claims.

[0058]

According to the first and second aspects of the present invention, the original set on the original platen is, for example, a halftone original such as a newspaper or an original on which an image is recorded up to near the edge of the paper. However, since the edge of the document can be detected, the size of the document can be detected.

According to the third aspect of the present invention, if the portion corresponding to the predetermined condition is not detected by the detecting means, the position of the light source is shifted and the reading line of the original image is changed. Since the line on which the image is recorded up to the document edge is read, the document edge can not be detected and the document size cannot be detected.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating an internal configuration of an image forming apparatus to which a document size detecting device according to an embodiment of the present invention is applied.

FIG. 2 is a partial perspective view of the image forming apparatus shown in FIG.

FIG. 3 is a block diagram showing an electrical configuration of the apparatus main body.

FIG. 4 is a flowchart illustrating a flow of a document size detection process.

FIG. 5 is a diagram for explaining the principle of document size detection.

[Explanation of symbols]

 Reference Signs List 1 apparatus main body 2 scanner section 3 automatic document feeder (ADF) 5 operation section 70 CPU 71 ROM 72 RAM 73 image processing section

Claims (3)

[Claims] A document size detecting device for detecting the size of a document set on a document table, comprising: a light source for illuminating and scanning the document set on the document table; and a light source generated from the light source and reflected by the document. Data generating means for generating image data corresponding to the document density based on the
Detecting means for detecting a portion corresponding to a predetermined condition; condition changing means for changing the above-mentioned predetermined condition to be relaxed when a detection signal is not output from the detecting means; and a document based on an output from the detecting means. And a size determining means for determining the size of the document. 2. The part corresponding to the predetermined condition is:
When examining the image data generated by the data generating means in a predetermined order, the image data having a density equal to or less than the reference density value is a portion where the number of pieces of reference data is equal to or greater than the number of the reference data. When no is output, at least one of a density value change process for increasing the reference density value by a predetermined value and a data number change process for decreasing the reference data number by a predetermined number is performed. 2. The document size detecting device according to claim 1, wherein: And a light source displacing means for displacing the light source by a predetermined distance when a detection signal is not output from the detecting means. 3. The document size detecting device according to claim 1, wherein the document size detecting device includes a document size detecting device.