JP2944341B2 - Document detection device and image reading device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an original detecting apparatus and an image reading apparatus, and more particularly, to an original detecting apparatus provided with a sensor for detecting the presence or absence of reflection of light applied to an original surface and used in a facsimile apparatus or a copying machine. The present invention relates to a document detection device and an image reading device for detecting the presence / absence, front and rear ends and width.

[0002]

2. Description of the Related Art In an image reading apparatus used in a facsimile machine, a copying machine, etc., it is important to reliably detect the presence / absence of a document, the leading edge, the trailing edge, and the width. Technology is being developed. Japanese Patent Application Laid-Open No.
There is a technique disclosed in Japanese Unexamined Patent Application Publication No. 2-296662 (hereinafter, referred to as a first publication). FIG. 15A shows a configuration of the image reading apparatus described in the first publication, and FIG.
(B) shows an example of a specific pattern used in the image reading device.

In FIG. 15A, reference numeral 4 denotes a document, reference numeral 21 denotes a document table, reference numeral 71 denotes a specific pattern, reference numeral 63 denotes a light source for illuminating the document 4, reference numeral 72 denotes a lens section for condensing light reflected from the document 4, and reference numeral 7 denotes a lens.
Reference numeral 3 denotes an image sensor unit that photoelectrically converts the collected light and reads image information. Reference numeral 5 denotes a transport roller for transporting the document 4, and reference numeral 74 denotes a drive motor unit for driving the transport roller 5. A discharge tray 75 receives a discharged document. 7
Reference numeral 6 denotes a control circuit for controlling the image sensor 73 and the drive motor 74.

[0004] The operation of the image reading apparatus configured as described above will be described. The manuscript 4 is placed on the manuscript table 21, and the drive circuit 74 is driven by the control circuit 76 while confirming the presence or absence of the manuscript 4 by reading the specific pattern 71 by the image sensor 73, and the manuscript runs through the transport roller 5. Let it. At this time, since the original 4 passes through the image sensor unit 73 side of the specific pattern 71,
The specific pattern 71 is concealed by the document 4 with respect to the image sensor unit 73. The document 4 is continuously run until the image sensor unit 73 reads a pattern different from the specific pattern 71. Thereafter, the image sensor unit 73 runs the document 4 stepwise while reading image information for each predetermined scanning line. When the specific pattern is read again as image information by the image sensor unit 73, the end of the document 4 is detected and the reading operation is terminated, and the document 4 is continuously moved again by the transport rollers 5 and discharged to the discharge tray 75. .

As another example of the conventional document detection technique, there is a technique disclosed in Japanese Utility Model Laid-Open Publication No. 63-3660 (hereinafter referred to as a second publication). FIG. 16A is a perspective view of a contact type line sensor with a transmission original document detection function described in the above publication, and FIG. 16B is a diagram of an image data reading unit using the line sensor of FIG. It is sectional drawing. FIG.
8A and 8B, reference numeral 80 denotes a contact type line sensor module, reference numeral 4 denotes a document, reference numeral 5 denotes a transport roller, reference numeral 84 denotes a document insertion opening, reference numeral 81 denotes a sensor for detecting a leading edge of a document, and reference numeral 82a denotes a sensor for detecting a document width. Reference numeral 82b denotes a document width detecting sensor (B), and reference numeral 83 denotes an image data reading line sensor.

The operation of the line sensor configured as described above will be described. When the document 4 is inserted from the document insertion slot 84, the leading edge of the document 4 is detected by the document leading edge detection sensor 81, and the transport roller 5 for transporting the document 4 starts rotating. The detection sensors (A) 82a and (B) 82b detect the document width.
At this time, it is predetermined that the document width is the A4 size when only the document width detection sensor (A) 82a operates, and the B4 size when the document width detection sensor (B) 82b also operates simultaneously. The information from the document width detecting sensor is given to the image data reading line sensor 83 to set the reading scanning width of the image data reading line sensor 83, and the information is also sent to the receiving side to set the receiving scanning width. The document 4 is further fed by the transport roller 5,
The image information is read by the image data reading line sensor 83.

[0007] Also, Japanese Patent Laid-Open Publication No. Hei 3-25456 (hereinafter referred to as
The third publication discloses a technique for preventing an erroneous determination due to a change in a detection value when a document is present in an automatic document feeder including a document detection sensor including a light emitting unit and a light receiving unit. FIG. 17A is a block diagram of the automatic document feeder described in the third publication.
FIG. 3B is a block diagram illustrating a motor control unit, a document detection unit, and the like. In FIG. 17A, reference numeral 90 denotes an automatic document feeder for conveying the document 4, reference numeral 91 denotes a main body of the copying machine, reference numeral 21 denotes a document table, reference numeral 92 denotes a loading roller for calling a document placed on the document table 21, and reference numeral 23 denotes a document 4. A paper feed roller for feeding the automatic document feeder, 93a is a document detection sensor (A), 93b is a document detection sensor (B), 93c is a document detection sensor (C),
Reference numeral 94 denotes a conveyance belt, and reference numeral 5 denotes a case where the conveyance belt 94
And 95, a paper discharge roller.

In FIG. 17B, 96a, 96b, 9
6c is an original detection sensor, an amplifier for amplifying and inputting the output of 93a, 93b, 93c to the microcomputer 98, 97 is a motor drive circuit for controlling motor drive, 97a is a paper feed motor for driving the paper feed roller 23, 9
7b is a transport motor for driving the transport roller 5, 97c and 97d are slit disks fixed so as to rotate together with the feed motor 97a and the transport motor 97b, and 97e and 97f are pulses of rotation of the slit disks 97c and 97d. The rotation sensors 97g and 97h for measurement are comparators for inputting the measurement information of the rotation sensors 97e and 97f to the microcomputer 98, and 99 is a display for operating the microcomputer 98.

Each of the above document detection sensors (A) 93a,
(B) 93b and (C) 93c each include a light emitting unit and a light receiving unit (not shown). The light emitting unit irradiates light to the back surface of the original 4 and the light receiving unit emits light on the back surface of the original 4 The reflected light is received.
Then, each original detection sensor (A) 93a, (B) 93b
And the output from (C) 93c are amplifiers 96a, 96
b and 96c, the analog data is taken into the analog port of the microcomputer 98 as it is. The microcomputer 98 includes the above-described original detection sensors (A) 93a, (B) 93b and (C) 93c.
Is compared with a predetermined determination level to detect the presence or absence of a document. The microcomputer 98 and the above-described original detection sensors (A) 93a and (B) 9
Each document detecting means is constituted by 3b and (C) 93c.

A method for determining the presence or absence of a document in the automatic document feeder configured as described above will be described with reference to FIG. First, it is determined whether or not a document is set after the power is turned on (S60). If a document is set, it is determined whether or not the determination level automatic setting mode is set. (S61). If the determination level automatic setting mode is set, the original is guided to the paper feed roller 23 by the rotation of the take-in roller 92, and the paper feed operation is started.
In this paper feeding operation, the paper feeding motor 97a is driven, and the rotation pulse of the slit disk 97c fixed to the motor 97a is measured by the rotation sensor 97e (S62), and the number of pulses is reduced to a predetermined number a. It is determined whether or not it has reached (S63).

In a normal automatic document feeder, the position of a document is detected by document detection sensors (A) 93a, (B) 93b and (C) 93c. The original detection sensors (A) 93a, (B) 93b and (C) 93c are set based on the detection value at the time of (1) and the detection value at the time of no document. The predetermined number a and the predetermined numbers b, c and d to be described later are determined in advance by the positional relationship between the document detection sensors (A) 93a, (B) 93b and (C) 93c. Has a specified value. The predetermined numbers a, b, c, and d are used so that a detection value based on the light reflected at the edge of the document is used for calculating the determination level.
Is stipulated.

In step 63, the pulse number is a predetermined number a
If it is determined that the time has been reached, the document detection sensors (A) 93a and (B) 93b are activated (S64). At this time, the sensors (A) 93a and (B) 93b obtain a detection value when there is a document based on the light reflected at the end of the document. When this detection value is obtained, the transport motor 97b is driven, and the slit disk 9 fixed to the motor 97b is driven.
After measuring the rotation pulse of 7d by the rotation sensor 97f (S65), it is determined whether or not the number of pulses has reached a predetermined number b (S66). When the number of pulses reaches the predetermined number b,
The driving of the sheet feeding motor 97a and the conveying motor 97b is stopped and the timer is started (S67), and it is determined whether or not the timer has reached the timer end (S67).
68).

If the timer end has been reached, the driving of the transport motor 97b is started and the measurement of the number of pulses of the rotation is started (S69), and it is determined whether or not the number of pulses has reached a predetermined number c (S70). ). When the number of pulses reaches the predetermined number c, the document detection sensor (C) 93c is activated (S7).
1) At this time, a sensor (C) 93c obtains a detection value when there is a document based on the light reflected at the end of the document. Then, it is determined whether or not the number of pulses has reached the predetermined number d (S72). When the number of pulses has reached, the drive of the conveyance motor 97b is stopped (S73), and the document detection sensors (A) 93a and (B).
93b and (C) 93c are operated (S74). At this time, a detection value when there is no document is obtained by the document detection sensors (A) 93a, (B) 93b and (C) 93c.
The determination level Z is calculated based on the detected value when there is no original and the above-described detected value when there is an original (S75).

Next, a method of automatically updating the determination level based on the accumulated number of document conveyances will be described with reference to FIG. The cumulative number of documents conveyed by the automatic document feeder 90 is calculated (S76), and when the cumulative number exceeds a predetermined number (S77), the processes of steps 60 to 74 described above are executed. In steps S64 and S71, it is detected whether or not the detection is performed by each document detection sensor (S78). If the detection value starts to change, a timer is started to obtain a fixed time for stabilizing the detection value (S79). ), After a lapse of a predetermined time (S8
0) The detection value of the document detection sensor is read (S81), and the determination is performed based on the determination level as in the processing of step 74 described above. Then, the count of the accumulated number is cleared (S83), and the process returns to step S76. In this way, each time the cumulative number reaches the predetermined number, the determination level is updated.

[0015]

However, document detection according to the prior art as described above has several disadvantages as follows. First, in the image reading apparatus described in the first publication, a specific pattern on the back surface of thin paper (12.2 kg paper) is affected. For example, in a specific pattern as shown in FIG.
Although the output as shown in (a) should be given, the black portion of the specific pattern is detected as the original is black by reflecting the black portion of the specific pattern because of the thin paper. The output is lower than the output.
An output as shown in (b) is obtained. In the case of thin paper as in this example, an original document output cannot be obtained.

Next, in the line sensor described in the second publication, the sensor for detecting the leading edge of the original and the sensor for detecting the original width of the black original detect the original by reflected light.
It is impossible to detect a black original that does not reflect light. For example, in the case of a document as shown in FIG.
In a document as shown in FIG. 21B, the trailing edge cannot be detected. In a B4 document as shown in FIG. 21C, detection as a B4 size cannot be performed.

Further, in the automatic document feeder described in the third publication, the specific level for judging the presence or absence of an original is determined by the output value of the original detection sensor when there is no original and the output value of the original detection sensor when there is an original. The output value when a document is present differs depending on the paper quality (thickness) of the document and when the document floats from the document detection sensor. If they are different at the time of actual document detection, an erroneous determination is likely to occur. For example,
If the higher output now has a black level and an output lower than the determination level is obtained, it is determined that "document is present", and the determination level initially calculated is the standard paper (45k).
g) and the next original is thin paper. In this case, the output value of the thin paper is higher than the output value of the standard paper (the output value is close to the black output value because the reflection of the thin paper is weaker than that of the standard paper). It is higher than the set determination level, and it is determined that there is no original, but there is no original. Also, for example, the output value is higher when the document floats from the document detection sensor than when the determination level is calculated first. Such an output value is higher than the previously determined determination level depending on the determination level, and it is determined that "there is no original". As in this example, the document detection method described in the third publication tends to cause erroneous determination of the presence or absence of a document with respect to various output values of the document detection sensor.

Therefore, the present invention can be incorporated in a reading module for reading image information, and the detection of the leading edge and the trailing edge of an original and the width of the original can be performed by detecting the paper quality (thickness) and density (monochrome) of the original, and an original detection sensor. An object of the present invention is to provide a document detection device and an image reading device using the document detection device, which are surely performed without depending on a change in a detection level due to a variation in electrical characteristics of a document or a change in a correlation between a document and a position of a detection sensor. I do.

[0019]

According to the present invention, a reading method is provided.
Transport sensor that transports the document to the scanning sensor
And a photo reflector.
The transport roller is white,
When there is no original between the scanner and the reading sensor,
Is detected, and a black area is
If there is a document with a part, it is determined that there is
The reflector is separated from the transport roller,
If there is no original between the photo reflector and
Is judged to have come out, and white paper appears between the transport roller and the photo reflector.
If there is a document with a part, it is determined that "document is present"
A document detection device for detecting a document edge by detecting
An image reading device is obtained .

[0020]

[0021]

[0022]

According to the structure of the present invention, the original reading position is a constant density pattern. Normally, the constant density pattern uses white or light gray. Therefore, even when the original is thin paper, the influence of the pattern on the back surface is raised. Therefore, the original read output of the original is not lost. Also read sensor
Since the detection is performed by both the photoreflector and the photoreflector, the original can be detected regardless of whether the original is white or black. If only the detection value based on light reception in the absence of a document is used as a reference, the level of the document presence / absence judgment changes due to the paper quality (thickness) of the document and the document floating from the document detection sensor, causing a malfunction in document detection. Will not be.
Moreover, even if the characteristics vary from one detection sensor to another, a certain margin with respect to the determination level can be obtained by adjusting the output within a certain range, so that erroneous determinations due to differences in the detection sensors hardly occur.

[0023]

[0024]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a perspective view of a first embodiment of the present invention, and FIG. 1B is a cross-sectional view of an image reading apparatus using the first embodiment of the present invention. 1A and 1B, reference numeral 2a denotes a photo reflector (A1), 2b denotes a photo reflector (A2), 3a denotes a contact type image sensor for reading (hereinafter, referred to as a reading sensor) (B1),
3b is a reading sensor (B2), 4 is a document, 5 is a document 4
These rollers are compactly integrated as a contact image sensor module 1.

The operation of the image reading apparatus configured as described above will be described. When the document 4 is set, the transport roller 5 starts rotating, and while the document 4 is being sent in the direction A, the leading end of the document 4 is detected by the photo reflector (A1) 2a and the reading sensor (B1) 3a, and When the width of the document 4 is detected by the reflector (A2) 2b and the reading sensor (B2) 3b, reading of the image information is sequentially started for each line by the reading sensor (B1) 3a. When the rear end of the document 4 is detected by the photoreflector (A1) 2a and the reading sensor (B1) 3a, the reading is terminated and the document 4 is discharged to the outside of the image reading device.

Here, the principle of detecting the front and rear ends of a document will be described. The front and rear edges of the original are photoreflectors (A
1) Detection is performed by 2a and the reading sensor (B1) 3a.
The photoreflector is a sensor 81 for detecting the leading edge of a document and a sensor for detecting a document width (A) 82a, (B) in the conventional image reading apparatus shown in FIGS. 16 (a) and 16 (b).
82b, and FIG. 17 (a),
This corresponds to the document detection sensors (A) 93a, (B) 93b and (C) 93c in the automatic document feeder according to the prior art shown in FIG.

[0027] As the photo reflector described above is Ri Contact includes a light emitting means (not shown) and light receiving means receives the light reflected by the surface of the original 4 and irradiates a light onto the surface of the original 4 at the light emitting means, At this time, the presence of the document 4 is detected by detecting the photocurrent flowing through the photo reflector.

On the other hand, when there is no original 4, the light from the light emitting means is reflected by the transport roller 5 and enters the photoreflector. However, since the distance between the transport roller 5 and the photoreflector is long, the photocurrent almost flows. Absent. The photo reflector detects that the document 4 is not present due to no photocurrent flowing. However, in the case of the present embodiment, if the portion corresponding to the position of the photoreflector of the original 4 is white, light is reflected on the surface of the original 4 and a photocurrent flows through the photoreflector. Manuscript 4 if the part is black
The photoreflector does not reflect the photocurrent and does not flow through the photoreflector, so that the photoreflector can detect a white document corresponding to the position of the photoreflector of the document.

On the other hand, the reading sensor (B1) 3a reads the surface of the transport roller 5 when there is no original 4. The surface of the transport roller 5 is white, and the reading sensor (B1) 3a reads all white when there is no original 4. When the document 4 having a black portion reaches the reading sensor (B1) 3a, the reading sensor (B1) 3a detects the black portion of the document 4 and detects "document present". Therefore, the leading end of the document 4 sequentially passes from the photoreflector (A1) 2a to the reading sensor (B1) 3a, so that the photoreflector (A1) 2a can be read by either the reading sensor (B1) 3a regardless of whether the document is black or white. The leading edge of the document 4 is always detected.

Here, in the case of this embodiment, the photoreflector (A1) 2a and the reading sensor (B1) 3a
When the original 4 is not present, the surface of the white transport roller 5 is read. However, as shown in FIG. 1B, the reading sensor (B1) 3a and the transport roller 5 are in close contact with each other. Since the photo-reflector (A1) 2a and the transport roller 5 are sufficiently separated from each other, even if the white surface of the transport roller 5 is read, the reading sensor (B1) 3a sets this to "white".
On the other hand, the photoreflector (A1) 2a judges this as "black" detection. Photo reflector (A1) 2
a, the diameter of the conveying roller 5 is reduced so that the original 4
When there is no light, the light from the light emitting means of the photo reflector (A1) 2a may not be reflected from anywhere.

The trailing edge of the original 4 can be detected in the same manner. When the rear end of the document 4 has passed the photoreflector (A1) 2a, the photoreflector (A1) 2a detects black because there is no document at the position of the photoreflector (A1) 2a. That is, "no original" or "black part of original" is detected. The transport roller 5 transports the document 4 to the position of the reading sensor (B1) 3a, and the reading sensor (B1).
1) If 3a is read in all white, the trailing end of the document 4 is detected. At this time, if the reading sensor (B1) 3a detects a black portion, it can be understood that it is not the rear end of the document 4.

Next, the principle of document width detection will be described. Here, it is assumed that the reading sensor (B1) 3a can read up to the document width of B4, and the document width detection is to detect whether the width is A4 or B4. The running of the manuscript is centered,
The document of A4 width passes through the central portion of the reading sensor (B1) 3a. Reading sensor (B2) 3b
Is a part on one side of the reading sensor (B1) 3a (outer part of the passing range of a document of A4 width).

The photoreflector (A2) 2b is also located on the same side of the reading sensor (B1) 3a and outside the pass range of the A4 width document. Since the document of A4 width does not pass through the photo reflector (A2) 2b and the reading sensor (B2) 3b, the photo reflector (A2) 2b and the reading sensor (B2) 3b do not detect the document. In this case, the document is determined to be an A4 width document. On the other hand, the original of B4 width has a photo-reflector (A2) 2b and a reading sensor (B2) 3b.
And the photoreflector (A2) 2b or the reading sensor (B2) 3b detects the leading edge of the document and determines that the document is a B4 document.

Next, the operation of this embodiment will be described with reference to the flowcharts shown in FIGS. In order to detect the leading edge and the trailing edge of the original in the image reading apparatus having the above configuration, first, in FIG. 2, the off-levels of the photoreflectors (A1) 2a and (A2) 2b when there is no original are monitored (S1). , Binarization threshold A1T for photoreflector (A1), binarization threshold A2T for photoreflector (A2), binarization threshold BTH for reading sensor (B1) / (B2), and continuous black pixels, which are original detection parameters Number BBP, line number threshold AX for photoreflector (A1) / (A2), line number threshold BX for reading sensor (B1) / (B2), photoreflector (A1) / (A
2) The line number threshold MX for position correction and the line number threshold NX for skew correction are set (S2).

Here, the binary signal of each sensor is
In the photoreflector (A1) 2a, the binarization threshold A
When there is a level of 1T or less, the photoreflector (A
1) The binarized signal A1 of 2a is set to A1 = 1 (that is, "white" is detected in this photoreflector), and if the photoreflector (A2) 2b has a level equal to or lower than the binarized threshold value A2T, Reflector (A2) 2b
Is set to A2 = 1 (that is, the photoreflector detects “white”), and the reading sensors (B1) 3a and (B2) 3b output the binarization threshold B
The pixel at the level of TH or less, that is, the black pixel is the continuous pixel number BBP.
When the reading sensor (B1) 3a
(B2) The binary signals B1 and B2 of 3b are respectively expressed by B1 =
1, B2 = 1 (that is, "black exists" in these sensors)
Detection).

In step 3, it is determined whether or not there is a document (S3).
The ED is turned on (S4) (S4), and the pre-processing command is executed (S5). In this preprocessing, a white reference (white transport roller 5 in the present embodiment) is read in advance by the reading sensors (B1) 3a, (B) in order to correct variations in illuminance on the document surface and variations in sensitivity of the reading sensor due to distortion of the optical system. B
2) Reading is performed by 3b, and the bit output is corrected based on this value. Thereafter, the output signals from these reading sensors become signals in which the bit output is corrected. If it is determined that such preprocessing has been completed (S6),
After the pre-processing is completed (S7), the process proceeds to the processing in FIG.

In FIG. 3, first, the detection of the leading edge of the document is started in step 8 (S8), and when the feeding of the document 4 is started by the transport roller 5 (S9), the photo reflector (A1) is started.
/ (A2) Position correction line counter MC and skew correction line counter NC, photoreflector (A1) line counter (white detection line counter) A1C, and reading sensor (B1) line counter (black line counter) B1C Clear (MC = NC = A1C = B1
C = 0) (S10), and waits for the head of the line. If it is determined that the line has reached the head (ST = 1) (S1
1), the process proceeds to step 12 and the photoreflector (A1)
The outputs of the reading sensor 2a and the reading sensor (B1) 3a are monitored (S12), and it is determined whether or not the reading sensor (B1) 3a detects black (S13). Hereinafter, the description will be made by dividing the original into a white original and a black original.

In the case of a white original document, the reading sensor (B1) 3a still reads the white color of the roller, so that B1 ≠
1 (all white detected), the process proceeds to step 14, and
1C is set to 0 (S14), and the line counter A1C for the photoreflector (A1) is set to the photoreflector (A1) /
(A2) It is determined whether or not the number is equal to the line number threshold value AX (S17). Since the first line is A1C = 0, A1
When C ≠ AX, the process proceeds to step 18, where it is determined whether the binary signal A1 of the photoreflector (A1) 2a is A1 = 1 (white detection) (S18). At this time, if the leading edge of the document has not yet reached the photoreflector (A1) 2a, A1 ≠ 1 (black detection) and step 21
Then, A1C = 0 is set (S21), and the process returns to step 11.

The leading edge of the document is a photo reflector (A1) 2
a, the leading edge of the document is now white, so A
1 = 1 (white detection), the process proceeds to step 19, and A1
C = A1C + 1 is set (S19), and it is determined again whether A1C = AX (S20). If A1C ≠ AX, the process returns to step 11 to repeat the above processing. Then, if A1C = AX in step 20, the process proceeds to step 22. Here, the line number threshold value AX for the photoreflector (A1) / (A2) is set to A1 = 1 (white detection) or A1 = 0 as a countermeasure against malfunction such as chattering of the photoreflectors (A1) 2a and (A2) 2b.
This is for counting the number of continuous lines of (black detection). Number of lines for reading sensor (B1) / (B2)
Similarly, the threshold value BX is set as B1 as a measure against malfunction such as chattering of the reading sensors (B1) 3a and (B2) 3b.
= 1 (black detection) or B1 = 0 (all white detection) for counting the continuous line number threshold value.

In step 22, MC = MC + 1 is set to correct the position of the photoreflector (S22).
It is determined whether or not the photoreflector (A1) / (A2) position correction line counter MC is equal to the photoreflector (A1) / (A2) position correction line number threshold MX (S).
23). Until the position is corrected, since MC ≠ MX, the process returns to step 11 and proceeds to step 17 via steps 11, 12, 13, and 14, but immediately proceeds to step 2 since A1C = AX.
Move to 2. When this process is repeated and MC = MX, that is, when the position correction is completed, NC = NC + 1 is set in step 24 to perform skew correction (S24), and the skew correction line counter NC sets the skew correction line number threshold NX.
Is determined (S25). Since NC ≠ NX until the skew is corrected, the process proceeds to step 26 and waits for the head of the line (S26), and returns to step 24. When this processing is repeated and NC = NX, that is, when the skew correction is completed, the process proceeds to step 27, and the detection of the leading edge of the document is completed.

Here, the photoreflector (A1) / (A
2) The position correction line number threshold MX and the skew correction line number threshold NX will be described. FIG. 6 shows a photo reflector (A1) 2a of the B4 contact type image sensor module 1,
(A2) 2b, reading sensor (B1) 3a, (B2)
3 shows the positional relationship between the original 4 having a width of 3b and an A4 width. Photoreflector (A1) in the original traveling direction
2a, (A2) 2b are reading sensors (B1) 3a,
(B2) 5.5 mm before 3b. Therefore, when the leading end of a white original is detected at the position of the photoreflector (A1) 2a, the leading end of the original reaches the line of the reading sensor (B1) 3a by further moving the original 4 by 5.5 mm. The number of lines for correcting the position of the photoreflector (A1) / (A2) corresponds to 5.5 mm. When the sub-scanning density is 7.7 lines / mm, 5.5.
5 mm corresponds to 42 lines (7.7 × 5.5).

A document traveling system such as a G3 facsimile is usually designed so that the skew is within 3% of the main scanning length in the sub scanning direction. The detection of the leading edge of the document is terminated when the leading edge of the document is in the main scanning direction and the photo reflector (A
1) When the document reaches the line of the reading sensor (B1) 3a at the position 2a, the document width detection can be ended while the leading edge of the document is in the main scanning direction with the photo reflector (A).
2) it is the time when it reaches the on line reading sensor (B2) 3b position 2 b. Photo reflector (A1) 2
a and the photoreflector (A2) 2b are 73 mm, so that the timing at which the detection of the document width can be completed is 2.2 mm (73 mm × 0. 03) There will be a considerable delay. Thus, the original tip main scanning direction in the Photo Li <br/> Furekuta (A1) reading sensor position 2a (B1)
After reaching the line 3a, a further 2.2 mm original 4
Makes it possible to detect the original width. The number of lines for skew correction is equivalent to 2.2 mm.

If the original is a black original, step 13
The leading edge of the original is still a reading sensor (B1) 3a
If it has not reached B1, it becomes B1 ≠ 1 (all white detection), and the process proceeds to step 17, but since A1C = 0 now, the process directly proceeds to step 18. Further, in step 21, A1C = 0 is set and the process returns to step 11.

The leading edge of the document has already been read by the sensor (B1)
3a, B1 = 1 in step 13
(Detection of presence of black), the process proceeds to step 15, and B
1C = B1C + 1 is set (S15). Then, it is determined whether or not the line counter B1C for the reading sensor (B1) 3a is equal to the line number threshold value BX for the reading sensor (B1) 3a (S16). Step 1 if BIC ≠ BX
7, the process returns to the step 11 through the steps 18 and 21. When BIC = BX by repeating this process, the process proceeds to step S24, and skew correction is performed in the same manner as in the case of the above-described original having a white front end (S24, S25, S24).
26) The detection of the leading edge of the document is completed.

Then, the processing shifts to the processing shown in FIG. 4 and shifts to the detection of the trailing edge of the original. In FIG. 4, the detection of the trailing edge of the original is started in step 28 (S28), and the photoreflector (A1) / (A2) is started. ) The position correction line counter MC, the photoreflector (A1) line counter A1C, and the reading sensor (B1) line counter B1C are cleared (MC = A1C = BIC = 0) (S29), and step 30 is performed. At the beginning of the line. If it is determined that the line has reached the head (ST = 1) (S30), the process proceeds to step 31, and it is determined whether or not the photoreflector (A1) 2a has not detected white (A1 = 0) (S31).
If A1 ≠ 0 (white detection), the process returns to step 29.
If 1 = 0 (black detection), the process shifts to step 32 to determine whether or not the photoreflector (A1) line counter A1C is equal to the photoreflector (A1) / (A2) line number threshold AX (S32). ). If A1C = AX, the process shifts to step 35, but the first line is A1C ≠
Since it is AX, the process goes to step 33 and A1C = A1C
+1 is set (S33), and it is determined again whether A1C = AX (S34).

If A1C ≠ AX, the flow returns to step 30 to repeat the above processing until A1C = AX. A
When 1C = AX, the process proceeds to step 35 to set MC = MC + 1 in order to correct the position of the photoreflector (S35), and it is determined in step 36 whether or not MC ≧ MX (S36). Until MC ≧ MX,
Returning to step 30, the processing of steps 31, 32 and 35 is repeated. If MC ≧ MX by repeating this process, the process proceeds to step 37, and it is determined whether or not the reading sensor (B1) 3a detects all white (B1 = 0) (S37). B1C if B1 = 0
= 0 (S38) and returns to step 30, but B1 = 0
If so, the process proceeds to step 39 to set B1C = B1C + 1 (S39). In step 40, the line counter B1C for the reading sensor (B1) reads the reading sensor (B
It is determined whether it is equal to 1) / (B2) line number threshold value BX (S40). If B1C ≠ BX, the process returns to step 30 and the above processing is repeated.

When B1C = BX by repeating this process, the flow shifts to step 41 to complete the detection of the trailing edge of the original (S41). Then, the feed is stopped (S42), and it is determined whether or not there is a next page (S43). If there is a next page, the process returns to step 8 in FIG. 3 to start detecting the leading edge of the document again. If there is no next page, go to step 44,
The LED is turned off (OFF) (S44), and the detection of the leading edge and the trailing edge of the document ends.

In order to detect the width of the original in the image reading apparatus according to the present embodiment, as shown in FIG. 5, the detection of the original width is started at the same time as the detection of the leading end of the original is started (S8). First, at step 45, the line counter A2C for the photoreflector (A2) and the line counter B2C for the reading sensor (B2) are cleared (A2C = B2C = 0) (S45), and the head of the line is waited. If it is determined that the line has reached the head (ST = 1), the process proceeds to step 47, where the photoreflector (A
2) The outputs of 2b and the reading sensor (B2) 3b are monitored (S47), and it is determined whether or not the photoreflector (A2) 2b detects white (A2 = 1) (S4).
8). Hereinafter, the case where the document width is A4 width and B4 width will be described separately.

When the document width is A4 width, the photoreflector (A2) 2b and the reading sensor (B2) 3b do not detect the document (that is, both the white document and the black document have A2 width).
= 0, B2 = 0), it is determined in step 48 that A2 ≠ 1, and the flow shifts to step 49 to set A2C = 0 (S4
9) In step 52, the reading sensor (B2) 3
It is determined whether or not b detects black (S52). However, as described above, if the width is A4 width, B2 = 0, so that B2 ≠ 1 is determined.
It is set to 0 (S55). Then, in step 56, it is determined whether or not the detection of the leading edge of the document has been completed (S56). If the detection has not been completed, the flow returns to step 46 to repeat the above processing. If the detection of the leading edge of the document has been completed, step 5
Then, the document width is detected as A4 width (S57), and the document width detection ends.

If the original width is B4 width and the original is a white original (or if the original is a white original), it is determined in step 48 that A2 = 1, and the process proceeds to step 50 to proceed to A2C.
= A2C + 1 (S50), and in step 51, the line counter A2C for the photoreflector (A2) sets the line number threshold AX for the photoreflector (A2) / (A2).
Is determined (S51). A2C at the beginning
Since it is AX, the process proceeds to step 52, where it is determined whether or not the reading sensor (B2) 3b detects black (B2 = 1) (S52). Since B2Ｂ1 now, B2C = It is set to 0 (S55), and it is determined whether or not the detection of the leading edge of the document is completed (S56). At this time, since the detection of the leading edge of the document is not completed, the process returns to step 46 and the above processing is repeated.
C = AX, so the process proceeds to step 58, where the document width is detected as B4 width (S58), and the document width detection ends.

If the width of the original is B4 and the original is black (or the original is black), it is determined in step 48 that A2、1.
2C = 0 (S49), and it is determined in step 52 whether or not the reading sensor (B2) 3b detects black (B2 = 1) (S52). Now, since the original is black, it is determined that B2 = 1 and the process proceeds to step 53, where B2C =
As B2C + 1 (S53), in step 54, it is determined whether or not the reading sensor (B2) line counter B2C is equal to the reading sensor (B2) / (B2) line number threshold value BX (S54). Since B2C ≠ BX at the beginning, the process shifts to step 56 to determine whether or not the detection of the leading edge of the document is completed (S56). At this time, since the detection of the leading edge of the document has not yet been completed, the process returns to step 46 to repeat the above processing. However, before detecting that the detection of the leading edge of the document has been completed in step 56, B2C = BX
Then, the process proceeds to step 58, where the document width is detected as the B4 width (S58), and the document width detection ends.

In order to monitor the output of the photo reflector in the above-described series of operations, for example, a detection circuit as shown in FIG. 7 is used. In FIG. 7, 11 is a higher power supply line (5.0 V), 12 is an output terminal, and 13 is a photoreflector (that is, the photoreflector (A1) 2a, (A
2) 2b) and 14 are lower power lines. Photo reflector 13 is provided with a light emitting means (LED) 13a and a light receiving unit (phototransistor) 13b, as shown in FIG., The resistor R ₁ and the photocurrent for adjusting the optical current I _C of the phototransistor 13b I and the resistance R ₂ for converting the _C output voltage V _OUT is provided. When there is a white original on the photo reflector 13, the light emitting means (LED) 13
The photocurrent I _C receives light reflected by the white document by the light receiving means (phototransistor) 13b and irradiates a light to a white document flows at a. Accordingly, a voltage drop of I _C × R ₂ is caused by the resistor R ₂ , and the output V _{OUT of the} photoreflector 13 is output to the output terminal 12 = (5.0−I _C ×
R ₂ ) V is obtained.

The analog output V _OUT from the photo reflector obtained as described above is converted into a digital signal by the signal processing circuit shown in FIG. FIG.
The processing circuit shown in (a) also serves as a circuit for correcting variations in illuminance on the document surface and variations in sensitivity of the reading sensor due to distortion of the optical system, and the output of the reading sensor shown in FIGS. 1 (a) and 1 (b). And a photo reflector (A1) 2a,
(A2) Output SNS1 and SNS2 of 2b (FIG. 7
(Corresponding to the middle output V _OUT ) with the analog switches 32a, 32
Switching is performed between 2b and 32c, and AD conversion is performed by the AD conversion unit 33. Each of the analog switches is closed when the timing signals A, B, and C of the digital processing unit 31 in FIG. 8A are H (high) and is opened when the timing signals are L (low).

The output of the reading sensor, the output SNS1 of the photoreflector (A1) and the output of the photoreflector (A1)
The output SNS2 of 2) is sequentially read out by the timing signals A, B and C at the timing shown in FIG. 8B during one line, and is AD-converted by the AD converter 33 into a 6-bit digital output 34. You.

The read sensor output (digital output 34), which has been AD-converted into 6 bits, is subjected to correction of the illuminance variation of the document surface and the sensitivity variation of the read sensor by the digital processing unit 31, and then performs "all white detection" of one line. Or "black detection" information. 6-bit digital output 3
4, the A / D converted photoreflector (A1) 2a,
(A2) Outputs SNS1 and SNS2 of 2b are digitalized by a digital processing unit 31 based on a previously stored digital output when there is no original, based on a determination level obtained by a method described below, and information on the presence or absence of a white original. give.

FIG. 9A shows an example in which the output value V _OUT of the photoreflector 13 is determined in the detection circuit shown in FIG.
(B). Fig. 9 (a) is 45kg high quality paper (standard paper)
9B is an output value for the original, and FIG.
g For high-quality paper (thin paper) originals. In the figure, a photoreflector of I _C = 1.17 mA is shown, and I _C =
4.80mA photoreflectors, the I _C = 5.38
The photoreflector of mA was used. When the output value of the photoreflector 13 when there is no original and the output value when there is an original (here, 45 kg high-quality paper and 12.2 kg high-quality paper) are measured, the output value is obtained for each photoreflector and each paper quality (thickness). There is a difference, and there is a difference between the output value when there is no original and the output value when there is an original. Utilizing the difference between the output values, it is determined whether or not the original is on the photo reflector 13.

First, the output value of the photoreflector 13 when there is no original is stored, and then, when the level is lowered by a certain level (0.5 V in this example) from the level when there is no original, "no original" and "original" Yes ”boundary (slice level)
When an output value smaller than the slice level is obtained, it is determined that a document exists on the photoreflector 13.

In this embodiment, since the output value when there is a document is not used based on only the output value when there is no document when determining the slice level, the automatic document feeder described in the third publication described above is used. Unlike this, the slice level does not depend on the paper quality (thickness) of the document.
Therefore, even when a document having a thickness different from that at the time of determining the slice level is sent during actual document detection, erroneous determination does not occur, and this can be reliably detected.

According to the method of determining the slice level in this embodiment, the slice level does not depend on the distance between the document and the photoreflector (floating of the document). Therefore, even if the output of the photoreflector fluctuates due to the difference in how the document floats during actual document detection, the presence / absence determination of the document is hardly affected by the change, and erroneous determination is less likely to occur than in the conventional document detection. . An example is described below.

FIG. 10A is a sectional view of a document traveling system of an image reading apparatus to which the present embodiment is applied. In FIG. 1, when a document 4 is set on a document table 21, a document detection sensor 22 is physically pressed by the document 4 and mechanically detects the document 4. Then, the paper feed roller 23 and the transport roller 5 rotate, and the document 4 is sent to the close contact type image sensor module 1. Numeral 24 denotes an automatic paper feed rubber plate for transporting the documents one by one when a plurality of documents are set on the document table 21.

Photoreflectors (A1) 2a, (A2)
As shown in FIG. 10A, the sensor surface 2b is located at a distance of 0.5 from the original travel surface 25 of the contact type image sensor module 1.
mm apart. This is a photo reflector (A1) 2
a, (A2) 2b irradiates the surface of the original 4 with the light emitting means and receives the light reflected by the original 4, but the photocurrent becomes maximum when the distance from the original 4 is about 0.5 mm. It is. When the document 4 is conveyed in parallel with the document running surface 25 of the contact type image sensor module 1 and at the same height, the document of the contact type image sensor module 1 is positioned at the photoreflectors (A1) 2a and (A2) 2b. Running surface 2
Although the lifting of the document 4 from the document 5 becomes small, when the document 4 is conveyed at an angle with respect to the document running surface 25 as shown in FIG. 10A, the document 4 is moved at the positions of the photoreflectors (A1) 2a and (A2) 2b. It becomes easy to float from the original running surface 25 of the contact type image sensor module 1. As a result, the photocurrent of the photoreflectors (A1) 2a and (A2) 2b is reduced.

Regarding the detection in such a case, the relationship between the floating of white 12.2 kg paper from the sensor surface of the photoreflector and the output V _OUT of the output terminal 12 in FIG. 7 is shown in FIG.
(B). This result is for a photoreflector with I _C = 5.38 mA. Output V _OUT when there is no original
Is 3.3 V, if the threshold value (slice level) for detecting a white document is 2.8 V with a margin of 0.5 V, even if the white 12.2 kg paper is lifted from the sensor surface by 2.
Up to 5 mm can be detected.

As described above, according to this embodiment, irrespective of whether the document is a black document or a white document, there is a variation in the paper quality (thickness) of the document and the variation in the floating from the photo reflector. even if, it can be reliably detect the leading end after end and width.

Next, in addition to the above-described difference in the paper quality of the original and the difference in the manner in which the original is floated, variations in the output value due to variations in the characteristics of each photoreflector may cause an erroneous determination when the original is detected. However, as in the second embodiment of the present invention described below, original detection can be made more reliable by changing the photoreflector output detection circuit. FIG. 11A is a circuit diagram of a detection circuit according to a second embodiment of the present invention in which the photoreflector output detection circuit is modified. In the figure, the output terminal 11 is high-potential power supply line (5.0V), 12, 13 are photorealistic full <br/> reflectors, 14 low-potential power supply line, the analog switch 41 (a), 42 is an analog Switch (b). This circuit comprises analog switches (a) 41, (b) 4
The two resistors R ₃ , R ₄ connected in parallel to the resistor R ₂ or made detachable therefrom by turning on and off the two.
Is different from the detection circuit shown in FIG. In FIG. 11A, the photo reflector 13
When there is a white original on the light irradiated to the white document by the light emitting means (LED) 13a is received by the light receiving means (phototransistor), it flows optical current I _C is. The output voltage V _OUT is obtained at the output terminal 12 by the voltage drop at that time.

FIG. 11B shows the output value V of the photo reflector 13 obtained when both the analog switch (a) 41 and the analog switch (b) 42 are turned on.
An example of _OUT measurement is shown. 11 In (b) I
_C = _1.17mA photoreflectors, the I _C = 4.
80 mA photoreflector, I _C = 5.38 mA
Using the photoreflector of the present invention. The output value of the photo-reflector when there is no document, a is 4.7V,
3.6V, and it is 3.3V in.

The output of each photoreflector increases as the document floats as shown in the figure, and approaches the output value when there is no document. By the way, the boundary (slice level) between "no document" and "document present" is determined to be where a document is present by dropping a certain voltage from the output value when there is no document as shown in the first embodiment. . In this example, the point at which the voltage drops by 0.5 V is set as the slice level. Then, the slice levels of the photo reflectors become 4.2 V, 3.1 V, and 2.8 V, respectively. In this case, if the document floats by 2.5 mm, the document cannot be detected. Therefore, the analog switches (a) 41 and (b) 42 are operated so that the original can be detected regardless of the photo reflector even when the original floats by 2.5 mm.

In FIG. 11A, the current I _C when there is no original is I _C0 , the current I _C when there is an original is I _C1 ,
Assuming that the resistance value when the three resistors R ₂ , R ₃ and R ₄ are connected in parallel is Z ₂₃₄ , the difference ΔV ₂₃₄ between the output voltage when there is no original and when there is an original is ΔV ₂₃₄ = _{(5.0-I C0 · Z 234} ) - (5.0-I C1 · Z 234) = contrast _{(I C1 -I C0) · Z} 234, analog switches (a) 41, operating the (b) 42 Thus, for example, if the resistors R ₃ and R ₄ are separated from the resistor R ₂ , the difference ΔV ₂ between the output voltage when there is no original and when there is an original is given by Z ₂ when the value of the resistor R ₂ is Z _2. Similarly, ΔV ₂ = (I _C1 −I _C0 ) · Z ₂ .

Here, ΔV ₂₃₄ and ΔV ₂₃₄
Comparing V _2, because it is Z _2> Z _234, ΔV ₂
> It is a ΔV _234. That is, by operating the analog switches (a) 41 and (b) 42 in the detection circuit of FIG. 11A to adjust the combined resistance of the resistors R ₂ , R ₃ and R ₄ ,
It can be seen that the margin for determining the presence or absence of a document can be increased using the difference between the output when there is no document and the output when there is a document.

For example, in the case of (1), the analog switches (a) 41 and (b) 42 are turned off to increase the resistance value so that the output value when there is no original is as follows. Then, the output value when there is a document greatly decreases, and the difference from the output value when there is no document becomes large, so that the document can be detected even when it floats 2.5 mm.

Also in the case of (1), only the analog switch (b) 42 is turned off to increase the resistance value so that the output value when there is no original is as follows. Then, the output value when the document is present decreases and the difference from the output value when the document is absent increases, so that it is possible to detect even when the document floats by 2.5 mm. If the detection circuit shown in FIG. 11A is used by such an operation, the original can always be detected even if the original floats by 2.5 mm regardless of the variation of the photo reflector. Note that the resistors R ₂ , R ₃ , R in FIG.
₄ may be composed of a single variable resistor so that it can be adjusted externally. Alternatively, taps can be switched by an analog switch using a resistor with a tap.

In the first and second embodiments described above, an example has been described in which an original is detected by a combination of a photoreflector and a contact type image sensor. However, original detection is limited to the above combination. is not. As in the third and fourth embodiments described below, a document can be similarly detected by a combination of a photo reflector and a photo reflector or a combination of a contact type sensor and a contact type sensor.

FIG. 12 is a sectional view of a document traveling system of an image reading apparatus according to one embodiment of the present invention. Referring to FIG. 12, in the present embodiment, in addition to a reading sensor 55 dedicated to reading image information, photoreflectors (C1) 51a and (D1) 52a for detecting a leading edge of a document, and a photoreflector (C2) for detecting a document width. ) 51b and (D2) 5
2b.

The photoreflectors (C1) 51a, (C
2) Photoreflector (C1) / (C
2) A white back surface 53 is provided, and a black back surface 54 for the photo reflectors (D1) / (D2) is provided on the back surfaces of the photoreflectors (D1) 52a and (D2) 52b.

In FIG. 12, when the document 4 is set on the document table 21, the document detection sensor 22 is physically pushed by the document 4 and mechanically detects the document 4. Then, the paper feed roller 23 and the transport roller 5 rotate, and the document 4 is sent to the close contact type image sensor module 1. 24 is the platen 2
This is a rubber plate for automatic paper feeding for transporting the originals one by one when a plurality of originals are set in the same. The photoreflectors (C1) 51a and (C2) 51b read the back white when there is no original, and the output changes when a black original comes.
As a result, "document present" is detected. On the other hand, when there is no original, the photoreflectors (D1) 52a and (D2) 52b read the back black, and when a white original comes, the output changes, thereby detecting that "the original is present". The leading edge of the document is detected when the document sequentially passes through the photoreflectors (C1) 51a and (D1) 52a. That is, a black original is detected by the photo reflector (C1) 51a, and a white original is detected by the photo reflector (D1) 52a.

The photoreflectors (C2) 51b, (D
2) 52b is located outside the passing range of the document of A4 width,
If the document is not detected by the photo reflectors (C2) 51b and (D2) 52b, the document width is determined to be A4 width. The B4 width original is a photo reflector (C2) 51b,
(D2) It is detected when the document sequentially passes through 52b. That is, in the case of a black original, the photo reflector (C2)
51b, a photo reflector (D2) 52 for a white original
b.

As described above, by providing a black back surface and a white back surface for the two photoreflectors provided in the document traveling direction, the document can be detected by a combination of the photoreflectors. In this reference example, it is possible to select which of the white original and the black original is to be detected first by exchanging the positions of the black rear surface and the white rear surface, but in any case, regardless of the black / white of the original. This can be detected.

Next, FIG. 13 (a) is a view showing a section of a reading section of an image reading apparatus according to a third embodiment of the present invention, wherein an original is detected by a combination of a contact type sensor and a contact type sensor. This is an example of the operation. FIG. 13 (b)
FIG. 14 is a plan view of the contact image sensor module 1 in FIG.

13 (a) and 13 (b), reference numeral 1 denotes a contact image sensor module, 4 denotes a document, 5 denotes a conveying roller, 61 denotes a contact sensor for detecting the leading edge and trailing edge of the document, 62 denotes a contact sensor for detecting the document width, 63 is a light source, 3a and 3b are reading sensors (B1) and (B2). Contact sensor 61 for detecting the leading and trailing edges of the document, and contact sensor 6 for detecting the document width
2. The reading sensors (B1) 3a and (B2) 3b are all provided in the same glass. The contact sensor 61 for detecting the leading edge and the trailing edge of the document and the contact sensor 62 for detecting the document width are preset so as to detect a white document, and the reading sensors (B1) 3a and (B2) 3b are also used in the first embodiment. As described above, a black original is detected.

The operation of the image reading apparatus configured as described above will be described. When the document 4 is set, the document 4 is fed by the transport roller 5 in the direction A in FIG. In the case where the original 4 is a white original, when the leading end of the white original comes on the original leading and trailing edge detecting contact sensor 61, “document present” is detected by the original leading and trailing edge detecting contact sensor 61, and The document is sent to above the reading sensor 3a, and the detection of the leading edge of the document is completed. When the document is a black document, the document cannot be detected by the contact sensor 61 for detecting the leading and trailing edges of the document, and the document 4 is sent to the reading sensor (B1) 3a. When the original 4 is a white original, when the leading end of the white original comes on the original front-end and rear-end detection contact sensor 61, “document present” is detected by the original front-end and rear end detection adhesion sensor 61, and is read by the transport roller 5. The document is sent to above the sensor 3a, and the detection of the leading edge of the document is completed. When the document is a black document, the document cannot be detected by the contact sensor 61 for detecting the leading and trailing edges of the document, and the document 4 is sent to the reading sensor (B1) 3a. When the document 4 reaches the reading sensor (B1) 3a, the reading sensor (B1) 3a detects that "document is present" and terminates the detection of the leading edge of the document.

In addition to the detection of the leading edge of the original, the detection of the original width is performed by the original width detecting contact sensor 62 and the reading sensor (B).
2) Performed by 3b. Reading sensor (B1) 3
It is assumed that a can be read up to B4 width, and the document width detects A4 width or B4 width. Reading sensor (B
2) 3b is a portion at one end of the reading sensor (B1) 3a and a portion outside the passing range of the A4 width document.

The original width detecting contact sensor 62 is also located outside the passing range of the A4 width original on the same side as the reading sensor (B1) 3a. Since the A4 width document does not pass through the document width detection contact sensor 62 and the reading sensor (B2) 3b, the document width detection contact sensor 62 and the reading sensor (B2) 3b do not detect the document. In this case, the document is determined to be an A4 width document. On the other hand, the B4 width document sequentially passes through the document width detection contact sensor 62 and the reading sensor (B2) 3b, and the document width detection contact sensor 62 and the reading sensor (B2) 3b detect the document. to decide.

When the document width is detected as described above, image information is read by the reading sensor (B1) 3a. Then, after the contact sensor 61 for detecting the leading end and trailing end of the original detects the trailing end of the original in the same manner as the detection of the leading end of the original, the original is discharged out of the image reading apparatus.

In the above-described three embodiments and the reference example , the original is not skewed. However, as described above, some skew occurs in the original traveling system such as the G3 facsimile. It is unavoidable to do that. A document detection device must reliably detect a document even when there is such a skew. When the original is skewed, the detection of the width of the original is particularly problematic. However, as in a fourth embodiment of the present invention described below, by adding a photoreflector to the first embodiment, The width can be reliably detected.

FIG. 14 is a configuration diagram of a contact type image sensor module according to a fourth embodiment of the present invention. In the figure, 1 is a contact type image sensor module, 2a is a photo reflector (A1), 2b is a photo reflector (A2), 2c is a photo reflector (A3), 3a is a reading sensor (B1), 3b and 3c are reading, respectively. The sensors (B2) and (B3) are portions of both ends of the reading sensor (B1). The photo reflector and the reading sensor are separated by 5.5 mm.

The operation of the contact type image sensor module configured as described above will be described. The original is a photoreflector (A1) 2a, (A
2) It enters from the 2b and (A3) 2c sides and travels in the direction of the reading sensors (B1) 3a, (B2) 3b and (B3) 3c. Photoreflectors (A1) 2a, (A2) 2
b, (A3) 2c detect the white original and read sensors (B1) 3a, (B2) 3 as described in the first embodiment.
b, (B3) 3c detects a black original. The photo-reflector (A1) 2a and the reading sensor (B1) 3a detect the leading edge and the trailing edge of the document. The white original arrives on the photo reflector (A1) 2a and the photo reflector (A
1) When 2a detects that a document is present, the document is fed by 5.5 mm, reaches the reading sensor (B1) 3a, and ends the detection of the leading edge of the document. In the case of a black document, the photoreflector (A1) 2a cannot detect "document present" and the document is sent to the reading sensor (B1) 3a. When reaching the reading sensor (B1) 3a, the reading sensor (B1)
3a detects that "document is present" and ends the detection of the leading edge of the document. The detection of the trailing edge of the document can be performed in the same manner.

Photoreflector (A2) 2b, (A3)
2c and the reading sensors (B2) 3b and (B3) 3c detect the width of the original. Reading sensor (B1)
It is assumed that 3a can be read up to B4 width, and the document width detects A4 width or B4 width. The original travels at the center and the A4 width original is read by the reading sensor (B
1) Pass through the center of 3a. Reading sensor (B2) 3
b, (B3) 3c are portions on both sides of the reading sensor (B1) 3a and outside the passing range of the A4 width document. Photoreflectors (A2) 2b, (A3)
2c is also located on the same side of the reading sensor (B1) 3a and outside the passing range of the A4 width document. Since the A4 width original does not pass through the photoreflectors (A2) 2b and (A3) 2c and the reading sensors (B2) 3b and (B3) 3c,
The photo reflectors (A2) 2b and (A3) 2c and the reading sensors (B2) 3b and (B3) 3c do not detect the original. In this case, the document is determined to be an A4 width document. On the other hand, B4
Originals of width are photoreflectors (A2) 2b and (A3) 2
c and the reading sensors (B2) 3b and (B3) 3c sequentially, and the photoreflectors (A2) 2b and (A3) 2
c and the reading sensors (B2) 3b and (B3) 3c detect the document and determine that the document has a B4 width. If the document is skewed here, the photo reflector (A2) 2
b, (A3) 2c and reading sensor (B2) 3b,
(B3) 3c is located at both ends of the reading sensor (B1) 3a, so that even if the original is skewed, the photoreflector (A2) 2b and the reading sensor (B2) 3b, and the photoreflector (A3) 2c and Reading sensor (B
3) Either side of 3c detects the original and sets the width of the original to B
4 widths can be determined.

[0087]

As described above, according to the present invention,
At the first document detection position , the background density
A first document detecting means for detecting the document and, a second document detecting means for detecting the document based on the background density of the therein in the second document detection position, the first document detecting means and the second The two original detecting means are arranged in combination so as to detect originals of different black and white from each other, and the originals are sequentially passed from the first original detecting position to the second original detecting position. Even in the case of a white document, the presence / absence, leading and trailing edge, and document width can always be detected by one of the document detecting means. That is, it is possible to reliably detect regardless of the density (black and white) of the original,
It does not mean that only one of black and white documents can be detected. By mounting the first and second document detection means in one module, the apparatus can be reduced in size and cost can be reduced.

Further, according to the present invention, when determining the determination level for determining the presence or absence of a document, only the output value of the document detection means when there is no document is used as a reference and the output value when there is a document is not used. Therefore, even when the output value of the document detecting means fluctuates due to the difference in the paper quality (thickness) of the document or the way the document floats between the determination of the determination level and the actual document detection, the document is reliably detected. be able to. Further, by providing an adjusting means for adjusting the output value of the document detecting means within a predetermined range to widen the judgment margin at the time of detecting the document, the document can be reliably detected even if the characteristics of the document detecting means vary. be able to.

As described above, according to the present invention, the output value fluctuation and the density of the original due to the change of the paper quality of the original, the change of the mutual positional relationship between the original and the original detecting means, the variation of the characteristic of the original detecting means, and the like. A document detection device and an image reading device that can reliably detect a document regardless of (black and white) can be provided at low cost.

[Brief description of the drawings]

FIG. 1 (a) is a perspective view of a contact type image sensor module according to a first embodiment of the present invention. FIG. 2B is a cross-sectional view of the image reading apparatus using the contact image sensor module shown in FIG.

FIG. 2 is a flowchart for explaining the operation of the first embodiment of the present invention.

FIG. 3 is a flowchart for explaining the operation of the first embodiment of the present invention, and is a part after FIG. 2;

FIG. 4 is a flowchart for explaining the operation of the first embodiment of the present invention, and is a part after FIG. 3;

FIG. 5 is a flowchart for explaining the operation of the first embodiment of the present invention.

FIG. 6 is a plan view of the contact type image sensor module according to the first embodiment of the present invention and a diagram showing a document running state.

FIG. 7 is a circuit diagram of an output detection circuit of the photo reflector according to the first embodiment of the present invention.

FIG. 8A is a circuit diagram of a signal processing circuit for a photoreflector output according to the first embodiment of the present invention.
FIG. 7B is a diagram showing the timing of switching the input to the AD converter in the signal processing circuit shown in FIG.

FIG. 9 is a diagram showing an example of measuring a photoreflector output in the circuit shown in FIG. 7;

FIG. 10A is a cross-sectional view of a document traveling system in an image reading apparatus using the first embodiment of the present invention. FIG. 7B is a diagram showing the output of the photoreflector in a state where the document is floating above the sensor surface in the document traveling system shown in FIG.

FIG. 11 (a) is a circuit diagram of an output detection circuit of a photoreflector according to a second embodiment of the present invention. FIG. 7B is a diagram showing an example of measuring the photoreflector output in the output detection circuit shown in FIG.

FIG. 12 is a cross-sectional view of a document traveling system in the image reading device according to a reference example of the present invention.

FIG. 13A is a sectional view of a reading unit in an image reading apparatus according to a third embodiment of the present invention. FIG. 2B is a plan view of the contact type image sensor module in FIG.

FIG. 14 is a plan view of a contact image sensor module according to a fourth embodiment of the present invention.

FIG. 15A is a diagram illustrating a configuration of an example of an image reading apparatus according to a conventional technique. The division diagram (b) is a diagram showing a specific pattern in the division diagram (a).

FIG. 16A is a perspective view of an example of a contact type image sensor module according to a conventional technique. FIG. 2B is a cross-sectional view of a reading unit in the image reading apparatus using the contact type image sensor module shown in FIG.

FIG. 17A is a cross-sectional view of an example of an automatic document feeder according to the related art. FIG. 2B is a block diagram showing the motor control means and the document detection means in FIG.

FIG. 18 is a flowchart illustrating a method of calculating a determination level in a detection unit in the automatic document feeder illustrated in FIG. 17;

19 is a flowchart illustrating a method of updating a determination level by a detection unit in the automatic document feeder illustrated in FIG. 17;

20 is a diagram showing a comparison between an original output and an output when a thin paper document is used in the conventional image reading apparatus shown in FIG.

21 is a diagram illustrating an example of an undetectable document in the contact image sensor module according to the related art illustrated in FIG. 16;

[Explanation of symbols]

1,80 Contact image sensor module 2a, 2b, 51a, 51b, 52a, 52b Photoreflector 3a, 3b, 3c, 55 Reading sensor 4 Document 5 Conveyor roller 11 Higher power supply line 12 Output terminal 13 Photoreflector 14 Lower power supply Line 31 Digital processing section 33 AD conversion section 34 Digital output 71 Specific pattern 76 Control circuit section 83 Line sensor 90 Automatic document feeder 91 Copier body

Continuation of front page (56) References JP-A-62-65560 (JP, A) JP-A-63-280569 (JP, A) JP-A-3-34765 (JP, A) JP-A-3-110541 (JP) , U) Hikaru 3-181271 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04N 1/00 H04N 1/04 G03B 27/62 H01L 31/12

Claims (1)

(57) [Claims] 1. A reading sensor comprising: a reading roller; a conveying roller for conveying a document to the reading sensor; and a photoreflector, wherein the reading sensor is in close contact with the conveying roller, the conveying roller is white, and the conveying roller When there is no document between the scanning sensor and the reading sensor, it is determined that “white” has been detected, and a black portion is detected between the transport roller and the reading sensor.
When there is a document with a minute, it is determined that there is a document, the photo reflector is separated from the transport roller, and when there is no document between the transport roller and the photo reflector, it is determined that `` black '' is detected, The transport roller and the fan
When there is an original with a white part between
Indicates the end of the document by determining that there is a document.
Document detection device and an image reading apparatus and performs.