JPH0927909A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set automatically the read range in a background tracing mode. SOLUTION: A CCD 16 whose elements are juxtaposed one dimensionally reads image information of an original D, an image processing section 27 processes read image data and detects a size of the original. Then a CPU 20 allows the image processing section 27 to set a range in which a peak level of an original background is detected, based on the sensing information of the original size, in the case of selection of the background tracing read mode where data are read depending on the density of the original background.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document reading apparatus applied to a facsimile machine, a copying machine, a scanner for scanning a document, and the like.

[0002]

2. Description of the Related Art In a conventional document reading device, Japanese Patent Laid-Open No.
As described in Japanese Patent Laid-Open No. 256865 and Japanese Patent Laid-Open No. 3-268566, in order to obtain more proper image data of an original, absolute white reference reading is performed using an absolute white reference that does not depend on the background density of the original. There is a mode in which a mode and a background tracking reading mode in which scanning is performed according to the density of the background of the document (relative white reference) can be appropriately selected.

In the background tracking reading mode, it is necessary to set the reading / detection range in order to read the original and detect the peak level of the background of the original that defines the relative white reference.
The setting is performed by inputting document information such as the document size from the host computer side to which the document reading device is connected.

[0004]

In the above-mentioned conventional apparatus,
It was necessary to set the detection range from the host computer side in order to detect the background of the document, but there was a demand for a configuration in which the detection range was set automatically without the need.

It is an object of the present invention to provide an image reading apparatus in which the reading range in the background tracking mode is automatically set.

[0006]

In order to achieve the above object, according to the present invention, it is possible to detect image size of an original while reading image information of the original by photoelectric conversion elements arranged one-dimensionally. In addition, in an image reading apparatus capable of setting an absolute white reference reading mode for reading using an absolute white reference that does not depend on the original background density and a background following reading mode for reading according to the original background density When the mode is set, a means for setting a range for detecting the peak level of the background of the document based on the detection information of the document size is provided.

In the image reading apparatus, a prescan for detecting the original size is performed, and when the background following reading mode is set, a range for detecting the peak level of the original background is set based on the original size detection information. It is characterized in that a means for scanning for reading image information of a document is provided.

In the image reading apparatus, when the image information of the original is read, the leading edge of the original is read in the absolute white reference reading mode, the size of the original is detected at the same time, and the peak of the background of the original is detected based on the detection information of the original size. It is characterized in that a means for setting the range for detecting the level and then setting the background tracking reading mode to read the image information of the original is provided.

Further, according to the present invention, it is possible to read the image information of the original document by the photoelectric conversion elements arranged one-dimensionally and detect the state of the original document skew, and the absolute white reference which does not depend on the background density of the original document. In an image reading apparatus capable of setting an absolute white reference scanning mode in which scanning is performed by using a background tracking scanning mode in which scanning is performed according to the density of the document background, detection information of the document skew state is set when the background tracking scanning mode is set. And a means for setting a range for detecting the peak level of the background of the document.

Further, the image reading apparatus further comprises means for setting a range for detecting the peak level of the background of the document based on the detection information of the document skew state inside the document existing range when the background tracking reading mode is set. And

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a scanner apparatus according to a first embodiment of the present invention, in which 1 is a known automatic document feeder (ADF) provided on the upper right side of the apparatus main body 2 and 3 is an ADF.
1. A stepping motor for feeding originals provided inside 1.
Reference numeral 4 is a document setting table, 5 is a contact glass serving as a document reading table provided on the upper surface of the apparatus main body 2, 6 is a document pressing plate which is formed integrally with the ADF 1 and can open and close the surface of the contact glass 5. , 7 are publicly known white reference plates which are provided at the right end of the contact glass 5 below the ADF 1 and are read during shading correction.

A light source (for example, a fluorescent lamp) is provided inside the apparatus main body 1.
A first traveling body 12 provided with a mirror 10 and a mirror 11, a second traveling body 15 provided with a pair of mirrors 13 and 14, and photoelectric conversions arranged one-dimensionally in the main scanning direction of document reading. An element (for example, CCD) 16, a lens 17 for forming an original image from the second traveling body 15 on the photoelectric conversion element 16, and both the traveling bodies.
A stepping motor 18 and the like for driving 12, 15 are provided.

FIG. 2 is a block diagram showing a control circuit in this scanner apparatus. A CPU (central processing unit) 20 has a motor driver 21 for a stepping motor 3 for feeding a document and a stepping device for driving a traveling body. A motor driver 22 for the motor 18, a driver 23 for the fluorescent lamp 10, a driver 24 for the CCD 16, ROM 25 and RAM 26 which are memory elements,
An image processing unit 27, which will be described in detail later, a scan buffer 28,
A buffer controller 29 that manages input / output of data to / from the scan buffer 28, a line buffer 30 corresponding to a scan line, and an interface (I / F) controller 31 that controls an interface with an external device such as a host computer are connected. And exchanges control signals and the like.

FIG. 3 is a block diagram showing the arrangement of the image processing section. The image processing section 27 includes an analog video processing section 35 for processing an analog video signal, a shading correction processing section 36, and an image data processing section 37. And binarization processing unit 38
And a timing generator 39 for generating a timing signal.

In the scanner device, as the original reading mode, as shown in FIG. 4, the original D is placed on the contact glass 5 and the first traveling body 12 is moved to read the image information of the original. In the fixed original reading mode and as shown in FIG. 5, the ADF 1 is used to sequentially feed the originals D stacked on the original setting table 4, and the first fixed state is set at the reading position of the white reference plate 7 portion. There is an ADF type reading mode in which image information of a document is read by the traveling body 12.

Next, the basic operation of the scanner device will be described.

In the fixed original reading mode, the original D is set on the surface of the contact glass 5 under the original pressing plate 6,
When the start key is turned on, the CPU 20 operates the fluorescent lamp driver 23 to turn on the fluorescent lamp 10, and the CCD driver
The white reference plate 7 is read by the CCD 16 driven by 24, reference data for shading correction of the image data is obtained by the image processing unit 27, and the reference data is recorded in a memory (not shown) in the image processing unit 27. deep.

Further, the CPU 20 drives the stepping motor 18 for driving the traveling body via the motor driver 22 to move the first traveling body 12 in the sub-scanning direction of the document D. The image information of the document D is read by the CCD 16 when the first traveling body 12 moves. Then, as shown in FIG. 3, the analog video signal a photoelectrically converted by the CCD 16 is digitally converted by the analog video processing unit 35 of the image processing unit 27, and then the shading correction processing unit 36 and the image data processing are performed. Shading correction and various types of image data processing are performed by the unit 37, and binarization processing is performed by the binarization processing unit 38, and the binarized data b is output. Thereafter, the binarized data b is converted into the binary data shown in FIG.
Are sequentially recorded in the scan buffer 28. The data in the scan buffer 28 is output to an external host computer or the like under the control of the I / F controller 31.

In the ADF type reading mode, after the white reference plate 7 is read, the CPU 20 drives the stepping motor 3 for feeding the original document via the motor driver 21, and the original document placed on the original document setting table 4 is driven. Are conveyed one by one toward the document reading position on the contact glass 5.
At this time, the document is conveyed at a constant speed, and the first traveling member
The image information of the document D is read by the CCD 16 with 12 stopped. The analog video signal photoelectrically converted by the CCD 16 is processed in the same manner as in the fixed original reading mode,
The data is sequentially recorded in the scan buffer 28. The data in the scan buffer 28 is output to an external host computer or the like under the control of the I / F controller 31.

In the present scanner device, a pixel counter and a line counter are provided in the main scanning direction and the sub-scanning direction of document reading, respectively, and the reading point can be indicated by these counter values. As the pixel counter and the line counter, for example, the CPU 20 may be provided with a function corresponding to each counter.

Next, the detection of the position and width of the original will be described.

In order to detect the position and width of the document, it is necessary to detect the edge of the document. For example, a uniform density member 40 having a uniform density as shown in FIG. Is provided, the document size detection position X is set on the uniform density member 40, and the density difference from the document D is detected. Since the uniform density in this case is intended to be separated from the background density of the original to be read, the uniform density is set to a density that can be reliably separated from the background density of the original. Since the standard white document has a density level of OD (optical density) of about 0.1,
It suffices to have a density that can be separated from this density.

FIG. 7A shows an example of density level distribution of the uniform density member. Note that black is described as a high level and white as a low level. Further, for the sake of simplification of description, it is shown that the uniform density member 40 is read by the first running body 12 and the CCD 16 to output a uniform density level, but in reality, there are many density fluctuations. The illustrated position A is the reading start position in the main scanning direction. The position B indicates the main scanning read end position. Further, although the end portion of the uniform density member 40 in the main scanning direction is also illustrated as the position A and the position B, it is not particularly limited.

At the position A, the first pixel of the pixel counter in the main scanning direction is set, and the count is sequentially incremented. FIG. 7B is an explanatory diagram showing a distribution example of density levels when a document is detected. As can be seen from the figure, the C position indicates the start of the document density distribution in the main scanning direction, and the C position to the D position indicate the document width. The pixel position in the main scanning direction at the C position and the D position digitizes the point position, and the point indicated by this address thereafter indicates the position and width of the document.

The document size detection operation will be described more specifically.

In the ADF type reading mode, as shown in FIG. 6, the document D is conveyed until the document D surely appears at the document size detection position X on the uniform density member 40, and the document width at that time is set to the above-mentioned value. To detect. When this detection is performed, an interrupt is issued to the CPU 20 at that time. When the CPU 20 receives the interrupt signal, it can obtain the document position and its width information by reading the address values of the C position and D position obtained by the document size detection. When the detection process ends, the CPU 20
Moves the first traveling body 12 to the document reading position and also conveys the document D to the document reading position.

The CPU 20 outputs the document size data to the host computer before reading the document data according to the designation of the mode of the document size detection processing, and the host computer specifies the reading area to the scanner device by the document size data. Alternatively, the original is directly read according to the original size data. Then, after sending the read data (image data) to the host computer, the size of the document in the main scanning direction and the sub-scanning direction is sent to the host computer, so that main scanning synchronization can be obtained with the image data sent to the host computer. The image can be reproduced as a clear image.

Note that the original size detection for reading an original while it is being conveyed cannot detect the trailing edge of the original from the read data. Therefore, a detecting means (not shown) for detecting the presence or absence of the original when the original is conveyed. This is performed by detecting the trailing edge of the document based on the detection result of (1).

In the fixed original reading mode, the original D
Is set on the surface of the contact glass 5 with its side portion in contact with a predetermined size defining portion (abutting with origin), and is pressed against the surface of the contact glass 5 by the document holding plate 6. As described above, the document size needs to be separated from the document as described above. Therefore, the document pressing surface of the document pressing plate 6 has a uniform density that can be reliably separated from the background density of the document. Further, the document size is detected at a position where the leading edge of the document can be reliably determined, and the document width and position for reading the document are set based on the detected data.

That is, since the document D is set in contact with the size defining portion, the first traveling body 12 and CC
The reading with D16 is performed from the origin line of the size regulation section. At that time, since the trailing edge position of the document is detected, it can be determined that the document within the document range is surely present, and the original size of the document is not obstructed by the density of the image data within the document range. The image data on the inside is scanned from the side surface.

Then, while the original is read in the sub-scanning direction at the same reading position, the presence or absence of the original is detected by the density of the original. When the reading of the original document in the sub-scanning direction is completed, the original document density does not exist and the original document holding plate 6 has the same density.
When the change from the original density to the original pressing plate density is detected, an interrupt signal is generated to the CPU 20. C
Upon receiving the interrupt signal, the PU 20 interrupts the document reading process and stops the movement of the first traveling body 12. When the interrupt occurs, the CPU 20 detects the count value of the sub-scanning line counter and obtains the number of lines of the read image data from this count value.

In the present scanner device, there are an absolute white reference reading mode in which reading is performed using an absolute white reference that does not depend on the original background density, and a background following reading mode in which reading is performed according to the original background density (relative white reference). Either mode can be selected and used. The reading operation in both of these modes will be described below.

FIG. 8 is a circuit diagram showing in detail the configuration of the analog video processing unit 35 of FIG. 3, in which 50 and 51 are amplifiers and 52 and 53.
Is an analog switch, 54 is a capacitor, 55 is a resistor, 56 is a Zener diode, and 57 is an A / D converter.

In FIG. 8, the analog video signal a of the document information obtained by the photoelectric conversion of the CCD 16 is an amplifier.
Amplified by 50, input to the A / D converter 57 and converted into a digital signal. Here, in the absolute white reference reading mode, the voltage V _A generated by the Zener diode 56 as the reference voltage of the A / D converter 57 is the analog switch 5
Selected by 3. A signal (WHGT) which will be described later and is generated by the image data processing unit 37 is supplied to the condenser 54.
Then, the analog switch 52 holds the peak value of the white signal obtained by reading the white reference plate 7.

When the background tracking reading mode is selected, the voltage V _B held by the capacitor 54 is
It is applied as a reference voltage of the A / D converter 57 by the analog switch 53 via the amplifier 51. Image data processing unit 37
Then, based on the size information in the main scanning direction of the document obtained by the above-described document size detection, the range for performing the document background peak level detection is determined and the WHGT signal of FIG. 7B is generated. In the example of FIG. 7 (b), the range in which the document background peak level detection is performed is inside the document size (range of C to D).
(WHGT signal) is set. The holding voltage of the capacitor 54 is updated every main scanning, and the image data corresponding to the density of the background of the original is read.

By doing so, the range for performing the background tracking reading of the original can be automatically set by using the original size detection function of the scanner device without receiving an external input from the host computer. The original can be read according to the background density.

In the reading operation in both modes, the analog switch 53 is selected so that the reference voltage of the A / D converter 57 becomes V _A, and the document size is detected in the absolute white reference reading mode. After the prescan operation is performed and the size of the document in the main scanning direction is detected at the leading edge of the document, the image data processing unit 37 determines the range in which the peak level of the document background is detected, and WH is used during the second main scan.
It is also conceivable to generate a GT signal and read a document in the background tracking reading mode.

As described above, in the fixed original reading mode, the size of the original is detected by the pre-scanning of the leading edge of the original, whereby the range for performing the background tracking reading can be automatically set.

Further, as another example of the reading operation in both modes, when the reading operation is started, the analog switch 53 is selected so that the reference voltage of the A / D converter 57 becomes V _A , and the absolute white reference reading mode is selected. Is set, and when the leading edge of the document is read, the document size is detected at the same time as the reading operation, and the image data processing unit 37 detects the document size in the main scanning direction and then the background peak level of the document. It is also conceivable to determine the detection range, generate the WHGT signal, and then select the analog switch 53 so that the reference voltage of the A / D converter 57 becomes V _B.

By doing so, it is possible to automatically set the range in which the background is followed by one reading operation.

By the way, at the time of normal document conveyance in FIG. 6, the document D was conveyed until the document size detection position X appeared reliably, but when the document is skewed as shown in FIG. In order to detect the skew, the detection process is started before the document D reaches the document size detection position X.

In the detection processing, an interrupt is generated to the CPU 20 by detecting the original at the original size detection position X, and the original position information and the original width information are provided to the CPU 20 each time this occurs. Write to register. While performing this writing process, the document position information and the document width information at the time of the previous interrupt are taken out from the register, and are compared with the document position information and the document width information at the time of the current interrupt. A more specific description will be given with reference to FIGS.

FIGS. 10 (a) to 10 (e) show changes in the density level detected at the document size detection position X when a skew occurs. In FIG. 10 (a), the document is still at the document size detection position X. Has not reached. FIG. 10B shows a detection state at the time when the leading end of the document D reaches the document size detection position X, and an interrupt is issued to the CPU 20 from this time,
At the same time, the document position information and document width information at this time are written in the register. Next, due to the occurrence of the interrupt in FIG. 10 (c),
The document position information and the document width information at this time are written in the register, and the document position information and the document width information in FIG. As a result of comparison, the document width in the case of FIG.
Determines that the document D is skewed, has not reached the maximum width yet, and is in the process of expanding in width.

Further, when the document D is conveyed, it is shown in FIG.
As shown in FIG. 10 (e), the CPU 20 is shown in FIG. 10 (d) and FIG. 10 (e).
It is determined that they are the same when comparing the document width information based on the detection result. That is, the document D is conveyed to the maximum width. The maximum width is due to the document conveyance up to Figure 10 (d), and the information in Figure 10 (e) is
It is used as information for determining whether or not the width data of the document D in 10 (d) is the maximum data. In this way, the data related to the document width is updated while performing the interrupt process of the document detection process, and the maximum data of the document width is found. In this example, the document conveyance distance in FIGS. 10B to 10D is the amount of deviation due to skew.

To actually express the skew amount, the original D
Position information ((X in Figure 9
1 and Y2)) and the position information ((X2, Y3), (X3, Y3) in FIG. 9) in FIG.

CPU 20 when it is determined that the maximum data
The above-mentioned data is collectively processed according to an instruction from the host computer to send the skew data, the document position data, and the document width data to the host computer before or after reading the image data. In any case, after the detection is completed, the first traveling body 12 is moved to the document reading position, and the document is also conveyed to the document reading position to read the image of the document.

In the fixed original reading mode, in order to detect the skew of the original, the prescan is performed before the image reading of the original, and the skew amount is detected in the same manner as described above.

Next, the detection of the skew amount in the background tracking reading mode will be described with reference to the explanatory view of FIG.

That is, at the start of reading, reading is performed in the absolute white reference reading mode. If there is no skew, the reading range is set to the background tracking reading range (WHGT) according to the document size, and reading is performed. When the skew occurs, the skew amount is detected as described above, the reading is performed in the absolute white reference reading mode from the A line to the B line that does not reach the maximum width of the document, and the background tracking reading is performed after the B line. Set the range and switch to background tracking scanning mode. After that, the range of the background tracking reading is shifted according to the skew amount of the document (according to the inclination of the document) to perform the reading. The background tracking reading range is set for each main scan or every several lines. Then, after reading again from the maximum width of the document to the C line, which starts to become smaller, the absolute white reference mode is switched again to the D line.

By doing so, even if the document skew occurs, the range for performing the background tracking reading can be automatically set according to the skew amount of the document, so that the reading according to the background density of the document becomes possible. .

Further, after the prescan is performed to detect the skew of the document, A, B, and B shown in the explanatory view of FIG.
A rectangular area (hatched portion) inside the document D in each of the C and D lines is set as a range for detecting the peak level of the background of the document, and WHG is set in the rectangular area during the reading operation.
It is conceivable that the T signal is generated to perform the reading in the background tracking reading mode, and the reading in the absolute white reference reading mode is performed in the other areas.

By doing so, even if the document skew occurs, the range for performing the background tracking reading can be automatically set so as to always be inside the document according to the skew amount of the document. Optimal reading according to the density becomes possible.

[0054]

As described above, according to the image reading apparatus of the present invention, the range for performing background tracking reading is automatically set by using the document size detecting function. This makes it possible to read according to the background density of the original.

According to the second aspect of the present invention, the range for performing the background tracking reading can be automatically set by performing the prescan for detecting the original size in the fixed original reading mode.

According to the third aspect of the invention, the range in which the background tracking reading is performed can be automatically set by one reading operation.

According to the structure of claim 4, even if the document skew occurs, the range for performing background tracking reading can be automatically set according to the skew amount, and the reading according to the background density of the document can be performed. It will be possible.

According to the fifth aspect of the present invention, even if the document skew occurs, the background tracking reading range can be automatically set so as to always be inside the document according to the skew amount. , It becomes possible to read according to the optimal background density of the original.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a scanner device that is an embodiment of an image reading device of the present invention.

FIG. 2 is a block diagram showing a control circuit in an embodiment of the image reading apparatus of the present invention.

FIG. 3 is a block diagram showing a configuration of an image processing unit in an embodiment of the image reading apparatus of the present invention.

FIG. 4 is an explanatory diagram of a fixed original reading mode.

FIG. 5 is an explanatory diagram of an ADF type reading mode.

FIG. 6 is an explanatory diagram of a uniform density member in one embodiment of the image reading apparatus of the present invention.

FIG. 7 is an explanatory diagram of density level detection by a uniform density member in an embodiment of the image reading apparatus of the present invention.

FIG. 8 is a circuit diagram of an analog video processing unit in an embodiment of the image reading apparatus of the present invention.

FIG. 9 is an explanatory diagram of a uniform density member portion when a skew occurs in the embodiment of the image reading apparatus of the present invention.

FIG. 10 is an explanatory diagram of density level detection by a uniform density member when a skew occurs in an embodiment of the image reading apparatus of the present invention.

FIG. 11 is an explanatory diagram of skew amount detection in an embodiment of the image reading apparatus of the present invention.

FIG. 12 is an explanatory diagram of skew amount detection in an embodiment of the image reading apparatus of the present invention.

[Explanation of Codes] 1 ... ADF (Automatic Document Feeding Device), 6 ... Document Holding Plate,
7 ... White reference plate, 12 ... First running body, 15 ... Second running body, 16 ... Photoelectric conversion element (CCD), 20 ... CPU, 27
Image processing unit, 28 ... Scan buffer, 30 ... Line buffer, 35 ... Analog video processing unit, 36 ... Shading correction processing unit, 37 ... Image data processing unit, 38 ...
Binarization processing unit, 39 ... Timing generating unit, 40 ... Uniform density member, 50, 51 ... Amplifier, 52, 53 ... Analog switch, 57 ... A / D converter.

Claims (5)

[Claims] 1. A photoelectric conversion element arranged in a one-dimensional manner can read image information of an original and detect the original size, and perform reading using an absolute white reference that does not depend on the background density of the original. In an image reading apparatus capable of setting an absolute white reference scanning mode to be performed and a background tracking scanning mode in which scanning is performed according to the density of the document background, in the background tracking scanning mode, the document background is detected based on the detection information of the document size. An image reading apparatus comprising means for setting a range for detecting the peak level of the image. 2. The photoelectric conversion elements arranged in a one-dimensional manner can read the image information of the original, detect the original size, and read using an absolute white reference that does not depend on the background density of the original. In an image reading apparatus capable of setting an absolute white reference reading mode to be performed and a background following reading mode for reading according to the density of the background of the original, a prescan for detecting the original size is performed, and the background following reading mode is performed. At the time of setting, set the range for detecting the peak level of the background of the document based on the detection information of the document size,
An image reading apparatus comprising means for performing scanning for reading image information of a document. 3. A one-dimensionally arranged photoelectric conversion element is used to read image information of an original and also to detect the original size, and to read using an absolute white reference that does not depend on the background density of the original. In an image reading apparatus capable of setting an absolute white reference reading mode to be performed and a background follow-up reading mode to read according to the density of the background of the document, the leading edge of the document is set to the absolute white reference reading mode when reading image information of the document. The original size is detected at the same time, the range for detecting the peak level of the original background is set based on the detected original size information, and then the background tracking reading mode is set to read the image information of the original. An image reading apparatus comprising means for performing the operation. 4. A one-dimensionally arranged photoelectric conversion element is capable of reading image information of a document and detecting a document skew state, and reading using an absolute white reference that does not depend on the background density of the document. In an image reading apparatus capable of setting an absolute white reference reading mode for performing and a background following reading mode for reading according to the density of a document background, in the background following reading mode setting, based on the detection information of the document skew state. An image reading apparatus comprising means for setting a range for detecting a peak level of a background of a document. 5. A photoelectric conversion element arranged in a one-dimensional manner can read image information of an original and detect an original skew state, and read using an absolute white reference that does not depend on the background density of the original. In an image reading apparatus capable of setting an absolute white reference reading mode for performing and a background following reading mode for reading according to the density of a document background, in the background following reading mode setting, based on the detection information of the document skew state. An image reading apparatus comprising means for setting a range for detecting a peak level of a background of a document inside a document existing range.