JPH09243331A - Document size detector - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To accurately detect the size of a document. In an image reading apparatus for reading an original on a contact glass, a reflective original sensor is provided on a lower surface of the contact glass, and a reference threshold value to be compared with an output of the reflective original sensor is set in an original density halftone area. When a document is set, the document is detected by the signal from the document cover opening / closing detecting means, the output result of the first reflection type document sensor is obtained and compared with the reference threshold value, and the signal at the start of copying is set. The second output result of the reflection type original document sensor is obtained and compared with the reference threshold value, and the original size is detected by the change in the comparison result twice.

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 for an image reading device such as a copying machine.

[0002]

2. Description of the Related Art As a prior art related to the present invention, as disclosed in Japanese Patent Application Laid-Open No. 4-261565,
2. Description of the Related Art There is known a document size detection apparatus that has a unit for detecting the opening / closing angle of a document cover, detects the presence or absence of each document at two angles, and determines the document size according to the state of change.

Further, as described in Japanese Patent Application No. 3-8336, the bisector of the interior angle formed by both optical axes of the light emitting portion and the light receiving portion of the reflection type document sensor is connected to the hinge of the document cover. There is known a document detection device which is provided so as to be inclined to the side opposite to the hinge with respect to the normal line of the document table when viewed from the axial direction, thereby improving detection accuracy.

Conventionally, the detection of the size of a document has been performed by combining a scanner with an optical fiber color document cover or the like, but recently, a reflection type document sensor has been widely used to shorten the first copy time. ing.

In order to detect the document size with high accuracy, a method has been proposed in which the threshold value of the document sensor output is set to be high and the presence or absence of the document is detected when the document cover is closed. Furthermore, as a measure to prevent the false detection of the document size by detecting the hand holding the document,
It has been proposed that the sensors be arranged in two rows, and that long sensors and short sensors be installed.

[0006]

In the present invention, a plurality of reflection type document sensors are provided under the contact glass, and the document size is determined by the combination of the outputs of these sensors. In addition, there are some document standards that are the back standard because of the ease of use of the user.In such a case, when the user tries to accurately match a document of a small size to the document standard, the user manually touches the contact glass. If you set it while touching it, since it is a small size original, it is held down to the end by hand, so the current original size detection sensor will also detect your hand, it will be judged as a large size original and a large size copy will appear. There is a problem such as coming. This is because, at present, the threshold value is set to be high so that a color original or a black original can be detected without error. However, there is no effective technique for preventing false detection of the density of the hand holding a small-sized document as a disturbance.

Therefore, in the present invention, the threshold value is set as the halftone density area to prevent erroneous detection of the hand, and further, even when the document density becomes higher than the threshold value, the document size is detected again at the start of copying. However, an object of the present invention is to provide a document size detection device capable of detecting an error-free document size by considering a change from data when the document cover is closed.

[0008]

In order to solve the above-mentioned problems, the invention according to claim 1 is an image reading apparatus for reading an original on a contact glass, which has a reflective original sensor on the lower surface of the contact glass, A reference threshold value to be compared with the output of the document sensor is set in the document density halftone area, and when the document is set, the document is detected by a signal from the document cover opening / closing detection means, and the first reflection type document sensor Output result of, compare with the reference threshold,
The output result of the second reflection type original sensor by the signal at the start of copying is obtained and compared with the reference threshold value.
The feature is that the document size is detected based on a change in the degree comparison result.

According to a second aspect of the present invention, the original halftone area for setting the reference threshold value in the first aspect of the invention is
It is characterized in that the reflection density (OD) is set in a range of 0.3 to 0.6.

The invention according to claim 3 is characterized in that the reference threshold value in the invention according to claim 1 is variable.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the original density of the original placed on the contact glass is read by the reflective original sensor, and the detection result at this time is used as a reference threshold value. It is characterized by

According to a fifth aspect of the present invention, in the first aspect of the invention, the first output result of the reflection type original document sensor is obtained by a signal from the original document cover opening / closing detecting means in the original document size detecting device, and the reference is obtained. Compared with the threshold value, the output result of the second reflection type original document sensor by the signal at the start of copying is obtained and compared with the reference threshold value. The document size is detected by the size of the output result of the detected reflective document sensor.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a document size detecting device according to the present invention will be described below with reference to the drawings.
FIG. 6 shows an example in which the document size detection device is installed in a copying machine.
Shown in The reflective original detection sensor detects one of various sizes, and therefore has one length sensor 7, a width sensor 8,
I am using 3 of 9, 10.

FIG. 7 shows the detection state of the sensor for each document size. As shown in FIG. 7, by the above four sensors,
It is possible to detect seven types of document sizes of A3, B4, A4 portrait, B5 portrait, A4 landscape, B5 landscape, and A5 landscape.

The document size detection timing is two times when a signal is output from the document cover opening / closing detection means by lowering the document cover and when a signal at the start of copying is received.

The relationship between the document density (OD) and the output of the reflective document sensor is as shown in FIG. 1, and the document density at the output value b of the reflective document sensor is used as a threshold value. There is. This value corresponds to 0.4 in document density (OD), which is almost the density of a human hand. As a result, the human hand judges that there is no manuscript. By the way, conventionally,
Since the presence of a document was detected at point a where the reflective document sensor output was extremely low, the document size was sometimes erroneously detected.

When a document is set on the contact glass and the document cover is to be closed, a signal is generated from the document cover opening / closing detecting means in the middle of the process, and at the time of output of this signal, the first output of the reflection type document sensor. The value is obtained. When the reflection density (OD) obtained from this output value is 0.4 or less and 0.4 or more, it is divided into two as shown in FIGS. 8 and 10. The mark indicates that the sensor has determined that the document exists, and the mark x indicates that the sensor has determined that there is no document.

Next, the output value of the second reflective original sensor is obtained from the signal at the start of copying. When the reflection density (OD) obtained from this output value is 0.4 or less and when it is 0.4 or more, it is divided into two as shown in FIGS. 9 and 11. Similar to FIG. 8 and FIG. 10, a mark indicates that the sensor has determined that there is a document, and a mark x indicates that the sensor has determined that there is no document.

That is, when the reference threshold value is set to 0.4, and the reflection density (OD) of the original is 0.4 or less,
The output values of the first and second reflection type original document sensors are compared, and the original size is determined by the output state of the first reflection type original document sensor. When the original has a reflection density (OD) of 0.4 or more, the output values of the first and second reflection type document sensors are compared, and the document size is determined according to the output state of the second reflection type document sensor. decide.

In this way, the original is detected by the signal from the original cover opening / closing detection means when the original is set and the original cover is closed, and the output result of the first reflection type original sensor is compared with the reference threshold value. Since the original size is judged by grasping the change between the result and the output result of the second reflection type document sensor by the signal at the start of copying and the comparison result of the reference threshold value, the reflection density (OD) of 0. It is also possible to detect the size of four or more normal color originals. Therefore,
As described above, it is possible to prevent erroneous detection of the hand when the size is small.

FIG. 2 shows a block diagram of an embodiment of the document size detecting apparatus of the present invention. When a signal is generated from the document cover angle sensor 14 which constitutes the document cover opening / closing means, the light emitted from the light emitting element 1 is reflected by the document 2, the document cover or the space, and the reflected light enters the light receiving element 3. In the comparison circuit 4, the threshold value generation circuit 12 compares it with a predetermined threshold value b. The output is CPU
5 is input. Similarly, when the copy start key is pressed, the flow of detection similarly flows and the final document size is determined.

FIG. 3 is a flowchart showing the operation of the document size detecting device. The document size detection is roughly divided into two. While the document cover is being closed, a signal is generated by the document cover angle sensor 14, the document size is detected by the reflective document sensor based on this signal, this is compared with a reference threshold value, and the result is stored. Furthermore, when the copy button is turned on, the original size is detected again by the reflective original sensor, and this is compared with the reference threshold,
The result is stored. The document size is determined from the two stored data. This determination is made by observing the on / off state of each sensor, as shown in FIGS. 8 to 11, whereby the size of the color original can be detected without erroneous detection of the hand.

Actually, such a document size detecting sensor is
It is often composed of a light emitting element photodiode and a light receiving element phototransistor. The recommended value is a region where the reflection density (OD) is 0.3 to 0.6 as the threshold value, but the output of the light receiving element phototransistor at that time is often different depending on each element. FIG. 4 shows a schematic diagram of variations in the light receiving element and the light emitting element. In the conventional detection area, when the output of the light receiving element is a, the reflection density (O
D) A variation of 1.2 or more does not cause a problem. However, when the intermediate region is used as the threshold value, the variation width becomes unacceptable. Therefore, it is necessary to make the threshold setting variable, and the CP of the block diagram of FIG.
A threshold can be prepared selectably in U5. For which region to select the threshold value, for example, when it is desired to set the reflection density (OD) to 0.4, the reflection density (OD) is set to 0.4.
A gray chart of a certain degree is prepared, placed on a contact glass, the original density (OD) is read by a reflective original sensor, and the read value is set as a threshold value. Since this is the darkest original that cannot be detected, the area that can be detected can be set.

Further, FIG. 5 is a flow chart showing the procedure of automating the adjustment of the threshold value and omitting the trouble of the adjustment. Reflection density (OD) as reference document on contact glass
In the adjustment mode, a gray chart of 0.4 is set, and in the present example, for example, the threshold value is increased from 0% to 5% step, and the document size is repeatedly detected and the document cannot be detected. Is set as a new reference value and will be used thereafter. Thus, by determining the threshold value centering on the density level of the hand, which is considered as a disturbance, it is possible to detect the document size with few false detections.

When the user uses a book as a manuscript, the first manuscript size detection when the manuscript cover is closed performs the manuscript size detection as shown in FIG. Further, when the start button is pressed, the book is thick and the document cover cannot be brought into close contact with the contact glass, resulting in a gap, so that the document size detection value may not change between the first time and the second time. In this case, there is no problem if the result of FIG. 8 which is the data of the first time, which is detected as having a document, is directly handled as size data. Normally, since the contact cover side of the document cover is white, the document cover is in close contact with the contact glass, and the APS sensor can detect the document size.

[0026]

According to the first aspect of the present invention, a reflective original sensor is provided on the lower surface of the contact glass, and the reference threshold value to be compared with the output of the reflective original sensor is set in the original density halftone area. When the original is set, the original is detected by the original cover open / closed detection means, the output result of the first reflection type original sensor is obtained and compared with the reference threshold value, and the second time is detected by the signal at the start of copying. The output result of the reflection type original document sensor is obtained and compared with the reference threshold value, and the original size is detected by the change of the two comparison results. Therefore, the size detection accuracy can be improved.

According to the second aspect of the invention, the original halftone area for setting the reference threshold value is set to a reflection density (OD) of 0.3 to 0.6 close to the density of the hand. It is possible to prevent the influence of the hand at the time of a small-sized document with large disturbance.

According to the third aspect of the present invention, since the reference threshold value can be made variable by the operation unit or the like, it is possible to absorb the variation of the light emitting diode which is the light emitting element and the variation of the phototransistor which is the light receiving element. The level of reference document detection can be adjusted for each machine, and the document size detection accuracy can be improved.

According to the fourth aspect of the present invention, the document density of the document placed on the contact glass is read by the reflective document sensor, and the detection result at this time is set as the reference threshold value, thereby automatically setting. This makes it possible to prevent setting mistakes and set the reference threshold value in a short time.

According to the invention described in claim 5, the output result of the first reflection type document sensor by the document cover opening / closing detecting means in the document size detecting device is obtained and compared with the reference threshold value, and at the start of copying. The output result of the second reflection type original sensor by the signal of is obtained and compared with the reference threshold,
If the two comparison results do not change, the original size detection data of the first and second times should be used in order to detect the original size based on the size of the output result of the reflective original sensor that detects the presence of the original. Then, when copying books, the first
The original size can be detected even when the detection values of the second and second reflective sensors do not change.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a document reflection density and a reflection type sensor output in a document size detection device according to the present invention.

FIG. 2 is a block diagram showing an example of a signal processing system used in the document size detecting apparatus according to the present invention.

FIG. 3 is a flowchart showing a document size detecting operation in the document size detecting device according to the present invention.

FIG. 4 is a graph showing the relationship between the document density and the output of the light receiving element in the document size detecting device according to the present invention.

FIG. 5 is a flowchart showing an example of automatic adjustment of a threshold value in the document size detecting apparatus according to the present invention.

FIG. 6 is a plan view showing an arrangement example of sensors when a document size detecting device is mounted on a copying machine.

FIG. 7 shows an operating state of a sensor for each original size in the original size detecting device.

FIG. 8 is a diagram showing the relationship between the document size and the operation of each sensor when the reflection density is less than or equal to a reference threshold and the document cover is closed.

FIG. 9 is a diagram showing the relationship between the document size at the start of copying and the operation of each sensor when the reflection density is equal to or lower than the reference threshold value.

FIG. 10 is a diagram showing the relationship between the document size and the operation of each sensor when the reflection density is equal to or higher than a reference threshold and the document cover is closed.

FIG. 11 is a diagram showing the relationship between the document size at the start of copying and the operation of each sensor when the reflection density is equal to or higher than the reference threshold.

[Explanation of symbols]

 7 Reflective Original Detection Sensor (Length Sensor) 8 Reflective Original Detection Sensor (Width Sensor) 9 Reflective Original Detection Sensor (Width Sensor) 10 Reflective Original Detection Sensor (Width Sensor)

Claims (5)

[Claims] 1. An image reading apparatus for reading an original on a contact glass, wherein a reflective original sensor is provided on a lower surface of the contact glass, and a reference threshold value to be compared with an output of the reflective original sensor is set in an original density halftone area. Then, when the document is set, the document is detected by the signal from the document cover opening / closing detecting means, the output result of the first reflection type document sensor is obtained, and compared with the reference threshold value. A document size detection device that obtains a second output result of the reflection type document sensor based on a signal, compares the output result with a reference threshold value, and detects the document size based on a change in the two comparison results. 2. The original size detection according to claim 1, wherein the original halftone area for setting the reference threshold value is set in a range where the reflection density (OD) is 0.3 to 0.6. apparatus. 3. The document size detecting apparatus according to claim 1, wherein the reference threshold value is variable. 4. The document density of a document placed on the contact glass is read by a reflective document sensor, and the detection result at this time is used as a reference threshold value.
The document size detection device described. 5. The invention according to claim 1, wherein the output result of the first reflection type document sensor is obtained by a signal from the document cover opening / closing detecting means in the document size detecting device and is compared with a reference threshold value. . If the output result of the second reflection type original sensor by the signal at the start of copying is obtained and compared with the reference threshold value, and the comparison result of these two times does not change,
A document size detection device that detects the document size based on the size of the output result of the reflective document sensor that detects the presence of a document.