JPH11125872A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately execute the detection of a document edge so as to discriminate a document size in the case of detecting the document edge in a state where an original cover is closed so as to discriminate the document size. SOLUTION: The detected signal of an original cover sensor 15 to detect the fully closed state of the opening and closing of the original cover attached so that it can be opened and closed to an original platen is monitored, and when the detected signal to mean the fully closed state of the original cover is outputted by the original cover sensor 15, the detected signal of the original cover sensor 15 is checked after a specified time from the point of time again, and when the detected signal means the fully closed state, a CPU 16 instructs to start the detection of an edge at a fully closed time, and an edge detecting means 17 detects the document edge at the fully closed time from the image information of a document. The detected result of the original cover sensor 15 is checked after the specified time again without immediately executing the detection of the edge when the detected signal of the original cover sensor 15 is changed to that meaning the fully closed state, so that the detection of the edge is executed after confirming that the original cover is completely closed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus such as a digital copying machine and, more particularly, to detection of a document edge for determining a document size in the image reading apparatus.

[0002]

2. Description of the Related Art Conventionally, in document size detection in a copying machine or the like, as described in, for example, Japanese Patent Application Laid-Open No. 8-204912, document edge detection is performed when the document presser is close and fully closed, that is, when the background color is black and white. Document size detection. In the above method, an angle sensor for detecting that the document press has reached a predetermined angle with respect to the document table and a document press sensor for detecting that the document press has been closed are prepared. However, even if the document presser slightly floats so that the output of the sensor does not change, the output of the document presser sensor determines that the document presser is closed.

[0003]

In such a prior art, when detecting an edge of a document in a state where the document presser is closed, when the edge detection is performed at the same time when the document press sensor changes, the original document is detected. The background is gray instead of white because the presser foot is slightly floating and not completely closed. Therefore, there is a problem that the edge of the gray document cannot be detected because the density difference from the background is not present, and the size of the document cannot be determined.

An object of the present invention is to make it possible to correctly detect an edge of an original for judging the size of the original when detecting the edge of the original in a state in which the original presser is closed to judge the original size. That is the task.

[0005]

Means for Solving the Problems The present invention (claim 1) provides:
A document table (21) on which a document is set, a document holder (22) attached to the document table so as to be openable and closable, open / close detection means (15) for detecting the open / closed state of the document holder, and a document table set on the document table A reading unit (11) having image information detecting means (23-28) for scanning the scanned original to detect image information of the original, and monitoring a detection signal of the opening / closing detecting means; When a detection signal indicating the fully closed state is output, the detection signal of the detecting means is checked again after a predetermined time from the time, and when the detected signal indicates the fully closed state, the edge detection at the time of the fully closed state is performed. Control means (16) for instructing start, and edge detecting means (17) for detecting a document edge when fully closed from image information of a document read by the reading means in accordance with the command of the control means. An image reading apparatus. Further, according to the present invention (claim 2), in the above invention, the predetermined time is:
It is characterized in that it is changed in accordance with the type of document holding, for example, whether or not the document holding has an automatic document feeder.

According to a third aspect of the present invention, there is provided a document table on which a document is set, a document holder mounted on the document table so as to be openable and closable, and an open / close detecting means for detecting the open / close state of the document holder. A reading unit having a light source (23) for irradiating a document set on a platen, and image information detecting means (24 to 28) for detecting image information by reflected light from the document irradiated by the light source; A light amount increasing unit (61) for supplementing the light amount of the light source with respect to the vicinity of the position of the original document edge to be monitored; and a detection signal of the open / close detection unit is monitored. Control means for instructing the start of edge detection, and edge detecting means for detecting a document edge when fully closed from image information of the document read by the reading means in accordance with the command from the control means. Example was an image reading apparatus.

According to a fourth aspect of the present invention, there is provided a document table on which a document is set, a light source for irradiating the document set on the document table, and image information reflected by the document illuminated by the light source. A reading unit having an image information detecting unit to detect, and an irradiation amount of light from the light source to a document portion near a positioning reference end of the platen and an irradiation light amount from the light source to a document edge near an opposite side of the document portion. This is an image reading apparatus provided with light amount increasing means (61, 91).

[0008]

According to the prior art in which the detection of the document edge is started at the same time as the detection signal of the opening / closing detection means (document press sensor) changes, the document presser floats as shown in FIG. The background will be gray instead of completely white. For this reason, when the density of the document is gray, there is no difference in density from the background, so that edge detection cannot be performed, and the size of the document is uncertain. On the other hand, according to the present invention (claims 1 and 2), the edge detection is not performed immediately when the detection signal of the opening / closing detection means changes to a signal indicating full closure, but the opening / closing is performed again after a predetermined time. Since the detection result of the detection means is checked, the edge detection can be performed after confirming that the document presser is completely closed. For this reason, the background becomes white, and even if the original has a gray density, a density difference from the background occurs, so that the edge can be detected correctly, and the size of the original can be correctly determined based on the edge.

Further, according to the present invention (claim 3), even if the document presser is floating at the moment when the document presser is determined to be closed as shown in FIG. By compensating for the light blocked by the document, the background becomes bright (white) as shown in FIG. Therefore, a density difference between the gray original and the original is obtained, so that the original edge is correctly detected.

Conventionally, as shown in FIG. 10, since the light amount at the edge of the original is small, the edge of the original can use a sufficient bit width when exchanging reflectance data with digital data compared with the center of the original. However, according to the present invention (claim 4), by providing the light amount increasing means at both ends of the document, it is possible to suppress a decrease in the light amount at both ends of the document as shown in FIG. Can effectively use the bit width.

[0011]

(Embodiment 1) FIG. 1 is a block diagram showing a configuration of an embodiment of a document size detecting apparatus according to the present invention, and FIG. 2 is a diagram schematically showing a configuration of an image reading section. As shown in FIG. 1, a document size detecting apparatus according to the present embodiment includes an image reading unit 11 for reading an image of a document, and an AD conversion unit for converting analog image information output from the image reading unit 11 into digital image information. 1
2, a shading correction unit 13 for performing shading correction on the converted digital image information, and a document holding unit 22.
An angle sensor 14 that outputs an ON signal when the opening angle of FIG. 2 is within a predetermined angle, and a document holder 22
Document holding sensor 1 that outputs an ON signal when the document is closed
5, a CPU 16 having a function of monitoring the outputs of these sensors, controlling the operation of the document edge detecting unit 17 and determining the document size based on the edge position detected by the document detecting unit 17, and the control of the CPU 16 The document edge detecting unit 17 detects the presence or absence of a document placed on the document table 21 based on the image information from the image reading unit 11 and the position of the document edge.

As shown in FIG. 2, the image reading section 11 includes a document table 21 on which a document 29 is placed, and a white document cover surface 2.
A document holder 22 having a light source 23 for emitting light to the image surface of the document 29 while moving in the sub-scanning direction indicated by an arrow-
Mirrors 24, 25, and 2
6 and a CCD image sensor 28 that receives light via the lens 27 and converts it into an electric signal. further,
The image reading unit 11 includes an angle sensor 14 that outputs an on / off signal at a predetermined angle in a closed state by opening and closing the document press 22, and a document press sensor 15 that is turned on when the document press 22 is closed. Is attached.

The document edge detector 17 detects the document edges in two states, that is, when the document presser 22 is closed to a predetermined angle and the angle sensor 14 is turned on and when the document presser sensor 15 is turned on. Of the detection results in these two states, the edge position detected (largely) outside the main scanning direction is determined as the edge position of the document.

The document edge detecting section 17 extracts two pixels at a predetermined pixel interval from an input image signal, calculates a difference between the two densities, and calculates a difference obtained as a result of the calculation. A register or the like is provided that holds a value of a counter that indicates a position of a pixel on the scanning line when the density difference is equal to or larger than the threshold value. Lines 191 to 195 connecting the CPU 16 and the document edge detecting unit 17 are
, A control line for giving an edge detection instruction to the document edge detection unit 17, requesting data of a detection result, a signal line of data to be exchanged, and the like. For example, a data bus 191 for transmitting and receiving threshold data used for the operation, data of the operation result, and the like; an address bus 192 for specifying various registers in the document edge detecting unit 17; a write line 193 for instructing writing to the registers; And a chip select line 195 for selecting the document edge detector 17.

When the original presser 22 is in a state of being almost closed and the angle sensor 14 is outputting an ON signal, the background is black. Therefore, one line of image data to be scanned is extracted at a predetermined interval, and its density is extracted. If the difference is a density change from white to black and the amount of change is equal to or greater than a predetermined threshold, the position is set as the document edge and the document edge position is updated. With the above-described edge detection method, the position of the density difference equal to or larger than the threshold is held from the inside to the outside of the original, that is, in the main scanning direction, and the finally remaining position is set as the original edge when the original is pressed and closed.
The original presser 22 is in the closed state, and the original press sensor 1
When 5 is on, the background is white due to the white cushion on the back side of the original press. Therefore, when the image data changes from black to white, original edge detection is performed in the same manner as the above method.
Note that a method of detecting the document edge based on the density difference is known (for example, see Japanese Patent Application Laid-Open No. 8-204912), and such a known method may be employed for detecting the edge itself in the present embodiment.

The operation of the document size detecting device of the image reading apparatus according to the present embodiment configured as described above will be described with reference to the operation flow of FIG. When a document 29 is placed with one document edge aligned with the document placement reference end on the document table 1 and the document press 22 is to be closed, the document press 22
At a predetermined angle with respect to the first document placing surface, the actuator of the angle sensor 14 attached to the attachment portion of the document holder 22 is pressed, and an ON output is generated at the angle sensor 14.
When the sensor 14 is turned on, the CPU 16 instructs the document edge detection unit 17 to start the document edge detection in the closed state of the document presser 22, and the document edge detection unit 17 performs edge detection (steps S31 to S31).
32). To perform this edge detection, the image reading unit 11
Scans the original one line, and the output image data is A
The signal is supplied to the document edge detection unit 17 through the processing of the D conversion unit 12 and the shading correction unit 13. The document edge detecting unit 17 checks the instantaneous density change of the input one-line image data, and satisfies the condition that the density change is from white to black and the density change is equal to or more than a predetermined threshold. At that time, the position is held as a document edge candidate, and the document edge candidate is updated each time the condition is satisfied. The candidate document edge position remaining when the scanning is completed is set as the document edge when the document press is closed.

Next, when the document presser 22 is closed, the output of the document press sensor 15 is turned on (step S33). FIG.
In the state (1), since the document press is not completely closed on the document table 21 yet, the shaded portion in the dotted line in FIG. 4 is shaded, and a density difference between the document and the outside of the document hardly occurs as shown in FIG.
After the document pressing sensor 15 is turned on, the CPU 16 checks the output of the document pressing sensor 15 again after an appropriate delay time 150 ms in order to wait for the document pressing 22 to be completely closed as shown in FIG. S34-S
35). If the document pressing sensor 15 is turned on as a result of the confirmation, the CPU 16 instructs the document edge detecting unit 17 to detect a document edge when the document pressing unit 22 is fully closed, and the document edge detecting unit 17 responds to the instruction. Edge detection is performed (step S38). If the document pressing sensor 15 is off as a result of the confirmation, the CPU 16 determines that the original pressing sensor 15 has been turned on for 250 ms from the first on.
It is checked whether the time has elapsed (step S36). If 250 ms has not elapsed, it is checked whether or not the angle sensor 14 is off (step S37). If not, the process returns to step S35 to continue document detection. The repetition processing of steps S35 to S37 is performed at intervals of 10 ms.
Perform 0 times. If the result of the determination in step S35 is YES, a document edge is detected (step S38). 2
When 50 ms has elapsed and when the angle sensor 14 is turned off, it is considered that the document presser was opened for some reason in the middle, and the document edge detection when the document is fully closed is not performed (step S39). Then, the CPU 16 requests the document edge detection unit 17 to obtain a document edge detection result in the state where the document press is almost closed in step S32 and a document edge detection result in a state where the document press is fully closed in step S38. The document size is determined on the basis of (Step S40).

The above-mentioned delay time 150 ms is set in accordance with the vibration time and the drop time by changing the original presser 22 between the normal case and the automatic original feeder so that the original presser 22 is completely closed regardless of the type of the original presser. To detect the document edge when the document presser is fully closed.

(Embodiment 2) This embodiment has a configuration in which a light amount increasing device is added to the end of the document table in Embodiment 1. In FIG. 6, a document table 21 and a document holder 22 are provided.
The configuration including the angle sensor 14 and the document pressing sensor 15 is the same as that of the first embodiment. The difference from the first embodiment is that a reflection plate 61 is attached to the left end of the original table in the figure as a light amount increasing device at the end of the original table. The light amount increasing device may be an auxiliary lamp or the like.

In the above configuration, when the document holder 22 is closed and the document pressing sensor 15 is turned on, if the light amount increasing device 61 is not provided at the end of the document table, the document will block light. Shadows are formed in the dotted circles in the vicinity, and the reflected light from the white cover of the document holder is reduced and becomes dark as shown in FIG. On the other hand, when the light amount increasing device 61 is attached to the end of the platen, the auxiliary light from the left side of the platen increases the reflected light of the white cover of the document holder, and as shown in FIG. The difference in density becomes clear. As described above, when the light amount increasing device 61 is attached to the end of the document table, it is possible to correctly detect the document edge when the document press is fully closed at the moment when the document press 22 is closed and the document press sensor 15 is turned on. it can.

(Embodiment 3) FIG. 9 schematically shows the structure of an image reading section in a third embodiment 2. In the second embodiment, the light amount increasing device 9 is provided on the opposite side of the light amount increasing device 61.
1 is provided. FIGS. 10 and 11 show white data when the light amount increasing device is not attached to the end of the document table and when the light amount increasing device is attached. In FIG. Comparing the white data at the center of the platen, the reflectivity drops considerably. When this reflectance data is converted into 8-bit digital data by the AD converter 12, white-black at the center of the document table is assigned to 8 bits, so that the bit width of the data at the end of the document table cannot be used effectively. In FIG. 11, since the light amount increasing devices 61 and 91 are attached, the reflectance of the white data at the end of the original table is large, and the bit width of the data at the end of the original table is also effective when white to black at the center of the original table is assigned to 8 bits. Can be used for

[0022]

According to the present invention (claims 1 and 2), the edge detection is not performed immediately when the detection signal of the open / close detection means changes to a signal indicating full closure, but is detected again after a predetermined time. Since the detection result of the open / close detection means was checked,
Edge detection can be performed after confirming that the document presser is completely closed. For this reason, the background becomes white, and even if the original has a gray density, a density difference from the background occurs, so that the edge can be detected correctly, and the size of the original can be correctly determined based on the edge.

Further, according to the present invention (claim 3), even if the document presser is floating at the moment when it is determined that the document presser is closed as shown in FIG. By compensating for the light blocked by the document, the background becomes bright (white) as shown in FIG. Therefore, a density difference between the gray original and the original is obtained, so that the original edge is correctly detected.

Further, according to the present invention (claim 4), by providing the light quantity increasing means at both ends of the document, it is possible to suppress a decrease in light quantity at both ends of the document as shown in FIG. Bit width can be used effectively for data.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of Embodiments 1 to 3 of the present invention;

FIG. 2 is a diagram schematically illustrating a configuration of a document reading unit according to the first exemplary embodiment.

FIG. 3 is a diagram showing a document size detection flow according to the first embodiment;

FIG. 4 is a diagram showing a state in which the document holder 22 is closed but not completely;

FIG. 5 is a diagram showing a state in which the document holder 22 is completely closed;

FIG. 6 is a diagram illustrating a configuration to which a light amount increasing device according to a second embodiment is added.

FIG. 7 is a diagram showing reflection when the document pressing is on when no light amount increasing device is added;

FIG. 8 is a diagram showing reflection when the document pressing is turned on in a second embodiment to which a light amount increasing device is added;

FIG. 9 is a diagram illustrating a configuration to which a light amount increasing device according to a third embodiment is added.

FIG. 10 is a diagram showing a bit width that can be assigned to a reflectance when a light amount increasing device is not added;

FIG. 11 is a diagram showing a bit width that can be assigned to a reflectance when a light amount increasing device is added;

[Explanation of symbols]

11: Image reading unit, 12: AD conversion unit, 13: Shading correction unit, 14: Angle sensor, 15: Document holding sensor, 16: CPU, 17: Document edge detection unit

Claims (4)

[Claims] 1. A document table on which a document is set, a document holder attached to the document table so as to be openable and closable, open / close detection means for detecting an open / close state of the document holder, and a document set on the document table. Reading means having image information detecting means for scanning to detect image information of the document, and monitoring the detection signal of the open / close detection means, when the open / close detection means outputs a detection signal indicating the full closing of the document press,
After a predetermined time from that point, the detection signal of the opening / closing detection means is checked again, and when the detection signal indicates full closure, a control means for instructing start of edge detection at full closure, the control means And an edge detecting unit for detecting a document edge from image information of the document read by the reading unit in response to the instruction. 2. The image reading apparatus according to claim 1, wherein the predetermined time is changed according to a type of document pressing. 3. A document table on which a document is set, a document presser attached to the document table so as to be openable and closable, open / close detection means for detecting the open / close state of the document presser, and irradiating the document set on the document table. Reading means having image information detecting means for detecting image information by reflected light from a document illuminated by the light source, and a light amount for supplementing an irradiation light amount from the light source to a position near a document edge to be detected Increasing means, monitoring the detection signal of the open / close detection means, and when the detection signal indicates fully closed, control means for instructing the start of edge detection when fully closed, and in response to the instruction of the control means And an edge detecting means for detecting a document edge from image information of the document read by the reading means. 4. A reading device comprising: a document table on which a document is set; a light source for irradiating the document set on the document table; and image information detecting means for detecting image information by reflected light from the document irradiated by the light source. And light amount increasing means for supplementing the irradiation light amount from the light source to the document portion near the positioning reference end of the document table and the irradiation light amount from the light source to the vicinity of the document edge on the opposite side of the document portion. An image reading apparatus characterized by the above-mentioned.