JPH04331563A - Image reader - Google Patents

Abstract

PURPOSE:To automatically detect an original area regardless of the density of an original to be read. CONSTITUTION:This image reader has an original detection plate 22 to cover the entire surface of a read area to be placed on the original. The original detection plate 22 is read together with the original and the original area is detected 20. The reader is provided with an original detection plate 20 having the pattern accompanying the change of density, a reference pattern storing means 23 to store corresponding data when only the original detection plate is read, a comparing means 17 to compare the read data with obtained from the reference pattern storing means 23, a counting means 19 to count the number of dots and the number of lines from a reference position, the original area detecting means 20 to detect the original area based on the compared result of the comparing means and a count value counted by the counting means, and a storage means 21 to store the original area detected by the original area detecting means 20. According to the compared result and the counted result, the original area is detected. Thus, the area of the original can be correctly detected even for the original having a white ground, high density of surrounding or entire part or intermediate density of surrounding or entire part.

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, and more particularly to an image reading apparatus having a function of automatically detecting an area of a document to be read.

0002

2. Description of the Related Art Conventionally, among image reading devices that read original documents such as photographs and characters to generate digital pixel data, image reading devices that can set a reading area are known. FIG. 2 is a block diagram illustrating an example of the configuration of a conventional image reading device in which a reading area can be set. 1 is an image reading means, 2 is a digital processing means, 3 is an image display means, 4 is a control means, 5 is a dot number counting means, 6 is a line number counting means, 7 is a dot number comparing means, 8 is a line number comparing means , 9 is a reading area setting means, and 10 is a document.

FIG. 3 is a side view showing an example of the configuration of the image reading means 1. As shown in FIG. Original table 11 made of glass etc.
The upper document 10 is illuminated by an illumination light source 12 , and the reflected light passes through a lens 13 and forms an image on an image sensor 14 . The image on the image sensor 14 is input to each reading pixel, and a signal corresponding to the intensity of light is output as pixel data. The image sensor is provided so as to have a reading width for the document, and the control means 4 in FIG.
Under this control, the document is scanned in the direction of arrow A by a scanning mechanism (not shown) in FIG. 3, and the entire document or a portion of the document is read.

In FIG. 2, the image signal generated by reading an original 10 by the original reading means 1 is processed by digital processing means comprising an A/D converter, shading correction means, etc. under the control of the control means 4 shown in FIG. 2 is converted into digital pixel data and displayed on the image display means 3. FIG. 4 is a plan view showing the readable area on the document table including the document area. 15 is a readable area, and 16 is a document area. Counting the number of dots or lines from the reference point O at the upper left of the diagram of the readable area 15, in the main scanning direction, the reading start position of the document is the X1-th dot, and the reading end position is the X2-th dot. Furthermore, in the sub-scanning direction, the reading start position is the y1-th line, and the reading end position is the y2-th line.

As described above, setting the reading area comes down to setting four values of document area parameters X1, X2, y1, and y2. These values are set in the reading area setting means 9 shown in FIG. The dot number counting means 5 counts dot signals corresponding to reading of each dot in the main scanning direction. Specifically, for example, clock signals corresponding to dot reading are counted. The line number counting means 8 counts line signals corresponding to reading of each line in the sub-scanning direction. Specifically, for example, line signals corresponding to line reading are counted.

The dot number comparing means 7 compares the counted value of the dot number counting means 5 and the setting value for the number of dots of the reading area setting means 9, and sets the reading signal to a valid state or a disabled state according to the comparison result. state. The line number comparing means 8 compares the counted value of the line number counting means 6 and the setting value for the number of lines of the reading area setting means 9, and sets the reading signal to a valid state or a invalid state depending on the comparison result. . The read signals output from the dot number comparison means 7 and the line number comparison means 8 are ANDed,
The signal is input to the digital processing circuit 2. Digital processing means 2
Then, image data is enabled or disabled depending on the enabled state or disabled state of the read signal.

First, reading control in the main scanning direction will be explained. First, at the start of reading each line, the dot number counting means 5 is reset by the control means 4, the dot number setting value X1 is set in the dot number comparing means 7, and the reading signal is set to an invalid state. The dot number counting means 5 counts the number of dots in response to reading, and the dot number comparing means 7 makes the read signal valid when the count value of the dot number counting means 5 becomes equal to X1. Changes in the state of the read signal are fed back to the control means 4, and the dot number comparison means 7 is set to a dot number setting value X2. The dot number comparison means 7 invalidates the read signal when the count value of the dot number counting means 5 becomes equal to X2. Thereafter, this is repeated every time each line is read.

Next, reading control in the sub-scanning direction will be explained. First, at the start of reading a document, the line number counting means 6 is reset by the control means 4, the line setting value y1 is set in the line number comparing means 8, and the reading signal is set to an invalid state. The line number comparing means 8 makes the read signal valid when the count value of the line number counting means 6 becomes equal to y1. Changes in the state of the read signal are fed back to the control means 4, and the line number comparison means 8 is set to a line setting value y2. The line number comparison means 8 indicates that the count value of the line number counting means 6 is y.
When equal to 2, the read signal is disabled.

Dot number comparison means 7 and line number comparison means 8
The read signals from the pixel are logically ANDed, and the digital processing means 2 outputs a pixel signal corresponding to a valid read signal. As a result, image data for the document area 16 as shown in FIG. 4 is obtained. Regarding the setting of the reading range for the reading area setting means 9 as described above, the original is pre-scanned before reading the original, the original area is automatically detected based on the reading signal at that time, and the original area is automatically detected based on the detected original area. A known method is to set a reading range and perform reading. FIG. 5 is a block diagram of a conventional document area detection means. 18 is a constant reference value storage means for storing a constant reference value; 17 is a comparison means for comparing pixel data with the constant reference value stored in the constant reference value storage means 18; and 19 is a standard. Counting means 20 counts the number of dots and lines from a position, and document area detection means 20 detects the document area based on the comparison result of the comparison means 17 and the counting result of the counting means 19.

[0010] Many ordinary originals have a white background, and a black original detection plate is often used to detect this. In the case of the optical system shown in Figure 3, the reflectance is high;
Even metal plates with little scattering can be read as black, so
The original detection plate itself does not have to be black. The document detection plate as described above is placed on the document 10 on the document table 11 so as to completely cover the readable area 15 in FIG. Also,
The reference constant value storage means 18 stores constant value data corresponding to the case where the document detection plate is read. Then, the entire readable area 15 is read by the image reading means 1. Detection of the document area 16 is performed based on a comparison result between each read pixel data and a constant value of reference data corresponding to the reading of the document detection plate, and a result of counting the number of dots and lines from a reference point.

First, detection of the document area 16 in the main scanning direction will be explained. Read the dots while counting the number of dots D. First, if there is data in the line that does not correspond to the reading of the original detection plate, it will be detected in the original area 16.
It is determined that it is the left end of , and x01=D. Furthermore, the same line is read while counting the number of dots D, and if there is data in the line that does not correspond to the reading of the original detection plate, x02=D is set. In the original area, x0
2 will be updated one after another. When the document area in one line ends, x02 is not updated, so x02 corresponds to the right end of the document area 16 in that line. The above detection is repeated for each line, but x01
The minimum value of x02 is set as x1, and the maximum value of x02 is set as x2, which is constantly updated. Then, x1 and x2 become the left end and right end of the final document area 16, respectively.

Next, detection of the document area 16 in the sub-scanning direction will be explained. Read the lines while counting the number of lines L. If there is data in the line that does not correspond to the reading of the original detection plate, it is determined that this is the upper end of the original area 16, and y1 =L. Furthermore, read the following lines while counting the number of lines, and if there is data in the line that does not correspond to the reading of the original detection plate,
Let y2=L. During the document area, y2 is updated one after another. When the original area 16 ends, y2 is not updated, so y2 corresponds to the final lower end of the original area 16.

As described above, the document area detection means 20 detects the document area parameters x1, x2, y1, y2.
Calculate. The calculated document area parameters are stored in the document area storage means 21. When reading a document to obtain image data, the document area parameters x1, x2, y1, y2 stored in the document area storage means 21 are used.
As explained in FIG. 2, only the document area is read using the scanner to obtain image data.

[0014] In the prescan for detecting the document area as described above, it is sufficient to know the area of the document and there is no need to read the contents of the document in detail, so it is sufficient to read the document at high speed by lowering the reading density or the like. As described above, conventionally, a document detection plate with a uniform density that can be read as black is used to automatically detect the document area, and the document is read based on the detected document area.

[0015]

[Problems to be Solved by the Invention] However, with the conventional document area detection method as described above, for example, in the case of a document with a high overall density or surrounding area, it is not possible to distinguish between the document and the document detection plate when detecting the document area. , the document area could not be detected correctly. Therefore, when reading is performed based on the result of document area detection, there is a problem that depending on the type of document, the required area may not be read correctly. In addition, in order to enable area detection not only for originals with a white background but also for originals with a high overall density or surrounding area, it is necessary to use an original detection plate with a uniform density between white and black, such as intermediate gray. Although this is possible, there is a problem that area detection becomes impossible for originals having backgrounds of similar density.

[0016]

[Means for Solving the Problems] In order to solve the above problems, the present invention provides an image reading device that reads a document and generates digital pixel data, and is capable of covering the entire surface of the reading area placed on the document. In an image reading device that has a document detection plate having a function of detecting a document area by reading the document detection plate together with the document, the document detection plate has a pattern with a density change and only the document detection plate has a function of detecting the document area. Reference pattern storage means for storing data corresponding to when read, comparison means for comparing the read data and data obtained from the reference pattern storage means, and a counter for counting the number of dots and lines from a reference position. means, a document area detecting means for detecting a document area based on the comparison result of the comparing means and the count value counted by the counting means, and a storage means for storing the document area detected by the document area detecting means. It was configured from

[0017]

[Operation] In the image reading device configured as described above, when detecting a document area, the reference data for a pattern with density changes on the document detection plate and the document read data are compared, and a reference point is used. The document area is detected based on the results of counting the number of dots and lines from .

[0018]

[Embodiments] Hereinafter, embodiments of the present invention will be explained based on the drawings. FIG. 1 is a block diagram showing the configuration of the present invention. Reference numeral 23 is a reference pattern storage means for storing data corresponding to the reading of the original detection plate. FIG. 6 is a plan view showing an example of a pattern with density changes of the original detection plate 22 used in the present invention. In FIG. 6, hatched areas with narrow intervals indicate areas with high concentration. In this case, the reference pattern storage means 23 stores data corresponding to the case where a pattern with density changes on the original detection plate 22 in FIG. 6 is read. At this time, it is not necessarily necessary to store the read data as it is in the reference pattern storage means 23; for example, if the pattern of the document detection plate has regular repetition, only the basic pattern can be stored and may be referenced repeatedly. Alternatively, the pattern may be replaced with a mathematical formula or the like, and the reference pattern may be generated by calculation. FIG. 7 is a plan view showing another example of a pattern accompanied by a change in density of the original detection plate 22 used in the present invention. In FIG. 7, changes in density indicated by diagonal lines indicate intermediate changes in density. In this case as well, the reference pattern storage means 2 uses data corresponding to the case where the pattern with density changes on the original detection plate in FIG. 7 is read.
Remember it in 3.

When detecting the document area, the document detection plate 22 as described above is placed on the document 10 on the document table 11 so as to completely cover the readable area 15 in FIG. Then, the entire readable area 15 is read by the image reading means 1. As explained in FIG.
This is performed by the document area detecting means 20 based on the results of comparison with the reference data of the pattern corresponding to the reading of No. 2 and the results of counting the number of dots and lines from the reference point. The obtained document area parameters x1, x2, y1, y2 are as follows:
It is stored in the document area storage means 21 and used as described in FIG. 2 when reading a document and obtaining image data.

[0020] In the above explanation, a case has been described in which a document detection plate having a pattern as shown in FIGS. do not have.

[0021]

As described above, the present invention is an image reading device that reads a document and generates digital pixel data, and has a document detection plate that can cover the entire surface of the reading area placed on the document. However, in an image reading device that has a function of detecting a document area by reading the document detection plate together with the document, this corresponds to when only the document detection plate having a pattern with a density change and the document detection plate are read. a reference pattern storage means for storing data; a comparison means for comparing read data with data obtained from the reference pattern storage means; a counting means for counting the number of dots and lines from a reference position; and the comparison means and a storage means for storing the document area detected by the document area detection means. In addition to originals with a white background, the area of the original can be detected correctly even in originals with high density in the entire area or surrounding areas, or in originals with intermediate density in the overall area or surrounding areas.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention.

FIG. 2 is a block diagram showing an example of the configuration of a conventional image reading device that can set a reading area.

FIG. 3 is a side view showing an example of the configuration of the reading means 1. FIG.

FIG. 4 is a plan view showing a readable area on a document table including a document area.

FIG. 5 is a block diagram of a conventional document area detection means.

FIG. 6 is a plan view showing an example of a document detection plate used in the present invention.

FIG. 7 is a plan view showing another example of the document detection plate used in the present invention.

[Explanation of symbols]

1 Image reading means 2 Digital processing means 4 Control means 17 Comparison means 19 Counting means 20 Original area detection means 21 Original area storage means 22 Original detection board 23 Reference pattern storage means

Claims (1)

[Claims] Claim 1: An image reading device that reads a document and generates digital pixel data, comprising a document detection plate that can cover the entire surface of a reading area placed on the document, and the document detection board In an image reading device that has a function of detecting a document area by reading, there is a document detection plate having a pattern with a change in density, and a reference pattern memory that stores data corresponding to when only the document detection plate is read. a comparison means for comparing the read data with the data obtained from the reference pattern storage means; a counting means for counting the number of dots and lines from the reference position; 1. An image reading apparatus comprising: a document area detecting means for detecting a document area based on a counted value of the document area; and a storage means for storing the document area detected by the document area detecting means.