JPH0981674A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit influence on an image recognition processing or the like even when the dispersion of the time taken until a medium reaches a read part is present by returning to the leading address of an image memory and executing the write of the image data when the read of the medium is not ended. SOLUTION: A medium edge detection part 20 for performing detection by comparing the total sum of the image data for one line with a prescribed threshold value and the image memory 6 capable of storing at least the image data of the entire medium 1 are provided, the write is executed to the image memory 6 including the image data of a background part 5 from the read start time of a read part 10 and the write start address of medium images detected by the medium edge part 20 is stored. Then, when the read of the medium 1 is not ended even though the image data are written to the final address of the image memory 6, a write control part 30 returns to the leading address of the image memory 6 and executes the write of the image data. Thus, more than required hardwares are not prepared.

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 used for reading an image on a medium as image data and recognizing and processing the image described therein.

[0002]

2. Description of the Related Art An apparatus for reading characters written on a medium as image data and recognizing the image data includes a conveyance path for inhaling and conveying the medium and an image sensor for reading the image of the medium on the conveyance path. And so on. When the medium is loaded into the apparatus, the medium is conveyed on the conveying path at a constant speed, and the image of the medium is scanned and read by the image sensor line by line to obtain image data for image recognition processing.

This medium is not always carried on the carrying path at a predetermined timing. For example, if the medium is pressed at the entrance when the medium is loaded and the start is delayed,
The timing when the medium reaches directly below the image sensor is delayed. When the image sensor detects that the medium is loaded, it immediately starts reading the image data. Therefore, the image data of the background portion is first written in the image memory for storing the image data of the medium, and subsequently, the image data of the medium is written. If it takes a long time to reach the image sensor of the medium, a relatively large amount of image data of the background portion is written in the image memory. Therefore, the image memory requires a certain amount of storage capacity in order to completely store the image data of the medium.

[0004]

The conventional image reading apparatus as described above has the following problems to be solved. As described above, an unspecified amount of background image data is stored in the beginning of the image memory, and the medium image data is subsequently stored. Therefore, there is a problem that not only hardware cost is required, but also the cut-out processing time for cutting out a character image from image data of a medium is different every time. The variation in the timing of such processing affects various data processing thereafter.

[0005]

The present invention adopts the following constitution in order to solve the above points. <Structure> Scanning and reading the image of the medium line by line,
A reading unit for obtaining image data for image recognition processing,
A medium edge detection unit that detects the boundary between the image data of the background portion read before the image reading of the medium body and the image data of the medium body by comparing the sum of the image data for one line with a predetermined threshold value, At least the image memory that can store the image data of the entire medium and the writing start address of the medium image detected by the medium edge detection unit while writing the image memory including the image data of the background portion from the start of reading by the reading unit And the image data is written up to the final address of the image memory, and when the reading of the medium is not completed, the writing control unit returns to the head address of the image memory and executes the writing of the image data.

<Explanation> Scanning the medium line by line is scanning in the main scanning direction, and the direction perpendicular to this line is the sub scanning direction. The image of the medium is image data such as characters written on the surface of the medium. Characters and the like are cut out from this image data and subjected to recognition processing. The surface of the table or the conveyor belt that supports the medium serves as the background portion, which is present in front of the reading start side edge of the medium, and at the beginning of reading, a portion of the background portion is always read as image data. If the background portion is black and the medium is white, the total sum of the image data for one line changes abruptly at the edge portion of the medium. The threshold is set to a value that captures such changes.

In the image memory, writing is started from the head address, writing is performed up to the last address, and then the data is written again by returning to the head address. There is no problem even if the image data of the latter half of the medium read thereafter is overwritten in the portion from the start address to the writing start address of the medium image. Moreover, in this way, even if the medium slips during transportation and the image data of the background portion increases, the image memory is not wastefully used. In the image recognition processing of the medium, characters are cut out based on the write start address of the medium image detected by the medium edge detection unit, so that the processing time of the image recognition processing and the like becomes almost constant.

<Structure> A reading unit that scans and reads an image of a medium line by line to obtain image data for image recognition processing, image data of a background unit read before image reading of the medium body, and medium body Medium edge detection unit that detects the boundary with the image data of 1 by comparing the total of the image data for one line with a predetermined threshold value, an image memory that stores at least the image data of the medium, and a reading unit Wait until the medium edge detection unit detects the boundary between the image data of the background portion and the image data of the medium body, and after writing a certain amount of the image data of the background portion from the image memory start address, the image data of the medium is written. And a write control unit for executing the writing of.

<Explanation> A certain amount of image data of the background portion is written in the head portion of the image memory so that the image can be accurately cut out from the image data of the medium. Therefore, even if you start reading,
The image data is not written from the leading portion of the image memory until the boundary between the background image and the medium body image is detected. The image data read by the reading unit before and after the boundary detection may be buffered in a non-obstructive area of the image memory and transferred after the boundary detection. The write start address of the image data of the medium is set to an appropriate value so that the image can be cut out with high accuracy.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to specific examples. <Embodiment 1> FIG. 1 is a schematic explanatory view of an image reading apparatus according to Embodiment 1 of the present invention. This apparatus is configured to scan an image of the medium 1 line by line by a reading unit 10 and read the image, and store image data for image recognition processing in an image memory 6. The medium 1 is read line by line along the main scanning direction 3. Further, the medium 1 is sent in the direction of the reading unit 10 on the transport path, so that the reading is advanced in the sub-scanning direction 4. The medium 1 is made of, for example, white paper, the conveying path is made of a black belt, and the image of this conveying path is called the image of the background portion 5. In the state as shown in the figure, the medium 1 is conveyed toward the reading unit 10, and the reading unit 1
When 0 starts reading an image, the image data of the background portion 5 is initially read. Therefore, as shown on the left side of the drawing, the image data of the background portion 5 is written from the head address A1 of the image memory 6 for a while.

After that, the writing of the image data of the medium is started from the address A2 shown in the figure. In the present invention, the address A2 at this boundary portion is used as the medium edge detection unit 2
0 is detected. If the medium 1 takes a relatively long time to reach the reading unit 10, as shown in the figure, a large amount of image data in the background unit 5 is stored in the image memory 6.
Is written to. Therefore, before writing the entire image data of the medium 1, the final address A3 of the image memory 6 is reached. At this time, in the device of the present invention, the write control unit 30
Controls the writing of the image data of the latter half of the medium 1 to be continuously executed from the head address A1 of the image memory 6.

That is, the first half of the image data of the medium 1 is written from the boundary address A2 to the final address A3, and the second half of the image data after that is written from the first address A1 to the image memory 6 as shown on the right side of the drawing. Address A4
Written up. The storage capacity of the image memory 6 is
It is set in advance to a size slightly larger than the capacity for storing the entire image data of the medium 1. Therefore, the image data of the background portion 5 slightly remains between the boundary address A2 and the address A4 of the portion where the writing of the image data of the medium is completed. In order to carry out the present invention as described above, the device of the present invention has the following hardware configuration, for example.

FIG. 2 is a hardware block diagram of the image reading apparatus. This apparatus is configured to suck the medium 1 in the direction of arrow 12 through the gate 9, convey the medium 1 on the conveying path 14, and read the image data by the image sensor 13. The medium 1 is at the gate 9
A medium sensor 11 for detecting the insertion of the medium is provided. In order to read the image, the device includes an insertion detection circuit 21, a clock pulse generator 22, an image sensor drive circuit 23, an A / D converter 25, a central processing unit (CPU) 24, an image memory 26, a ROM ( Reed
Only memory) 27 is provided.

The image data read by the image sensor 13 is converted into a digital signal from an analog signal by an A / D converter 25 via an amplifier 15 and sent to the apparatus. The CPU 24 is composed of a processor for controlling the entire apparatus, and controls the writing of the image data received from the A / D converter 25 through the data bus 28 into the image memory 26. The write address is supplied through the address bus 29. The image data writing control program is stored in the ROM 27. The reading unit 10 shown in FIG. 1 includes an image sensor 13 and a mechanism around the image sensor 13. The medium edge detection unit 20 shown in FIG. 1 is composed of a CPU 24 and a program for performing arithmetic processing of image data. Also, FIG.
The writing control unit 30 shown in FIG. 2 is configured by a control program for writing image data to the CPU 24 and the image memory 26.

The insertion detection circuit 21 is composed of a circuit for optically detecting the insertion of the medium 1 and sending an interrupt signal to the CPU 24. Clock pulse generator 22
Is a circuit for generating a clock signal for controlling image data reading of the medium 1 by the image sensor 13 and operation timing of the entire apparatus. Further, the image sensor drive circuit 23 outputs a read control signal to the image sensor 13 and at the same time outputs the timing signal to A
It is a circuit that supplies the / D converter 25 and the CPU 24.

<Operation> The above device operates as follows. First, when the medium 1 is inserted from the gate 9 in the direction of the arrow 12, the medium sensor 11 detects the front end of the medium 1 and notifies the CPU 24 through the insertion detection circuit 21. CPU 24
When the medium insertion is detected, the drive circuit (not shown) is driven to drive the transport path 14 to start transporting the medium 1. The medium 1 is conveyed in the direction of the arrow 12 and passes under the image sensor 13. The image sensor 13 starts reading image data at the same time when the conveyance of the medium is started. The image data is amplified by the amplifier 15, converted into digital data by the A / D converter 25, and stored in the image memory 26 line by line.

Subsequently, the CPU 24 executes the operation corresponding to the medium edge detecting section 20 shown in FIG. That is, the signals forming the image data read by the image sensor 13 are added pixel by pixel for each line and compared with a preset threshold value. For example, if the black dots are "1" and the white dots are "0" and the number of black dots in the image data for one line is counted, the total sum of the image data for one line can be obtained. Since the background portion 5 is black, the number of black dots is almost 1
It is equal to the number of lines. On the other hand, since the medium 1 is white, the number of black dots sharply decreases at the timing of reading the leading end of the medium 1. Therefore, if the intermediate value of the number of black dots is set as a threshold value, the CP value is set at the timing when the image sensor 13 reads the leading end portion of the medium 1.
U24 can detect. The specific determination operation will be described in detail later. Image memory 2 at this time
The image data write address of No. 6 is the boundary address A2 shown in FIG.

The address A2 is for identifying from which line of the image memory 6 the image data of the medium is written. For example, the image sensor drive circuit 23 shown in FIG. 2 drives the image sensor 13. To this end, the number of sample hold pulses output may be counted and the value may be held as the boundary address A2. The sample hold pulse is a pulse signal generated so that the line intervals when the medium 1 is read in the sub-scanning direction are equal. In this way, after detecting the address of the boundary, the image data of the medium is written in the image memory 6,
After that, when the final address of the image memory is reached, the image data of the remaining medium is written from the head address of the image memory 6. Subsequent processing is as described in FIG.

FIG. 3 is a signal explanatory diagram of each part of the apparatus when reading image data for one line. (A) shows the reference clock pulse output from the clock pulse generator 22. Further, (b) is an image sensor drive circuit 2
Reference numeral 3 indicates a sampling pulse generated by using the reference clock pulse. Further, (c) shows a sample hold pulse similarly output from the image sensor drive circuit 23. One sampling pulse is output at the timing of reading one pixel of the image signal. Also, the sample hold pulse is set to 1 at the start of reading one line.
It is output twice. (D) is image data, and in the case of the figure, the black dots are read not in binary but in multivalue.
(E) is the number of lines, which represents the output of the counter indicating which line is read this time. Here, reading the image data of the m-th line is given as an example. (F) is a memory address for each pixel, and the address signal for one line is output from A0 + X to An + X to the address bus 29 shown in FIG. (G) is the timing at which image data is supplied to the image memory 26 through the data bus 28 when this address signal is output.

Next, the process of generating and transferring each signal will be described.
A sampling pulse is generated by dividing the reference clock pulse of (a), and a sample hold pulse is generated by counting a fixed number of this sampling pulse. The image data shown in (d) is synchronized with the falling edge of the sampling pulse shown in (c).
Output from Further, at the rising edge of the sampling pulse, this image data is converted into digital data in the A / D converter 25 and output to the data bus 28 at the timing shown in (g). The CPU 24
The memory address shown in (f) is set by counting the falling edges of the sampling pulse shown in (b). The output start time of the image data shown in (d) is (c)
It is a fixed time after the timing when the sample hold pulse shown in (1) is output. Therefore, the CPU 24 outputs the memory address shown in (f) to the address bus 29 at that timing. The CPU 24 counts and stores the sample hold pulse shown in (c) of this figure from the start of writing the image data. Then, when the boundary described above is detected, the value is held and used as the setting reference of the data read start position when the character is cut off from the image data of the medium later.

Boundary detection is performed as follows. If the image data is a multi-valued digital signal as shown in (d) of FIG.
It is represented by 256 gradations of FFH. In order to detect the boundary portion, the total sum of the image data for one line is obtained. This value is Σd. By doing so, the image data of the background portion having no medium has a value of Σdi close to 00H because the reflected light is small. Further, when the reading of the front end of the medium is started, the reflected light rapidly increases, and the value of Σd becomes extremely large. Therefore, a predetermined threshold value R is set, and when Σd is larger than this threshold value R, it is determined that the leading edge of the medium has been detected. The boundary can be detected in this manner regardless of whether the image data is multivalued or binary.

<Effect of Concrete Example 1> By performing the above-described processing, the storage capacity of the image memory 6 shown in FIG. 1 need only be slightly larger than the entire image data of the medium 1 and is required. There is no need to prepare the above hardware. Therefore, the memory cost can be set sufficiently low. If the boundary address A2 is stored, when the character is cut out from the image data of the medium next time, the reference address of the cutout is always at a fixed position with respect to the medium, and the character is cut out. A series of processing such as extraction and recognition processing can be performed at a fixed timing. That is,
Even if the time until the medium reaches the reading unit 10 varies, there is an effect that it does not affect the image recognition processing and the like.

<Specific Example 2> FIG. 4 is a schematic explanatory view of an apparatus of specific example 2. In the specific example 1 described using FIG. 1,
The image data writing of the medium 1 is started from an arbitrary address of the image memory 6. On the other hand, in this embodiment, the medium 1 is always located at a fixed position as seen from the start address of the image memory 6.
Set to the image data writing start address of. For this purpose, for example, the write start address immediately after the start of reading is set to the address A2 which is separated from the start address A1 of the image memory 6. Then, the writing of the image data of the background portion is started from here, and as soon as the boundary A3 with the image data of the medium is detected, a certain amount of the image data of the background portion is written to the head address A1 of the image memory 6, and the subsequent address A4. To write the image data of the medium.

The detection of the start of writing the image data on the medium is performed by the medium edge detecting section 20. The writing control unit 30 controls the writing of image data of the medium to the image memory 6.
Done by Start address A of this image memory 6
The image data of the background portion written from 1 may be several lines. In this way, by storing the image data of the background portion for several lines and then storing the image data of the medium, it is possible to detect the edge of the medium with high accuracy using a well-known feature matrix or the like. . Therefore, when cutting out the position of the character written on the medium with reference to a fixed distance from the front end, that is, the edge portion of the medium, the cutting can be performed with high accuracy.

Moreover, the subsequent image recognition processing or the like may always be started from the top address of the image memory 6, the procedure is constant and the processing time is also constant, and the subsequent processing can be carried out smoothly. In order to detect the image data of the medium at the address A3 and then sequentially write the image data of the background portion and the image data of the medium from the head address A1 of the image memory 6, for example, the CPU performs the reading operation of the medium. The process of transferring the image data written before and after the address A3 to the head address A1 or less of the image memory 6 in the idle time may be performed in parallel with the medium reading operation. That is, for such an operation, the portion before and after the address A3 of the image memory 6 is used as a so-called buffer memory.

<Effect of Concrete Example 2> The capacity of the image memory is
Similar to the specific example 1, the image data of the medium may be fixed at a level slightly larger than the total amount of the image data of the medium that can be stored, and the image data of the medium is surely written at a fixed position counting from the start address of the image memory. It is not necessary to hold the address or control the write operation from the last address of the image memory to the first address, and the load on the CPU is reduced. Therefore, the processing time for storing the image data of the medium can be shortened. Further, since the image data of the medium is stored in a certain place of the image memory, it is possible to perform the cutting process for image recognition with high accuracy,
Further, there is an effect that the processing time becomes constant. In the above example, the edge detection is performed by the intensity difference between the reflected light of the background portion and the medium, but by the determination of the difference between the reflected light and the transmitted light of the medium and its surroundings, any detection method can be used. It is possible.

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram of an apparatus of a specific example 1.

FIG. 2 is a hardware block diagram of the image reading apparatus.

FIG. 3 is a signal explanatory diagram of each part of the apparatus for one line.

FIG. 4 is a schematic explanatory view of a device of specific example 2.

[Explanation of symbols]

 1 Medium 6 Image Memory 10 Reading Unit 20 Medium Edge Detection Unit 30 Writing Control Unit

Claims (2)

[Claims] 1. A reading unit that scans an image on a medium line by line to obtain image data for image recognition processing; image data of a background unit read before image reading of a medium body; A medium edge detection unit that detects the boundary with the image data by comparing the total sum of the image data for one line with a predetermined threshold, an image memory that can store at least the image data of the entire medium, and a reading unit at the start of reading. From the medium to the image memory including the image data of the background portion, stores the write start address of the medium image detected by the medium edge detection unit, and writes the image data up to the final address of the image memory. If the reading of is not completed, the program returns to the start address of the image memory and writes the image data. An image reading apparatus comprising a control unit. 2. A reading unit for scanning an image of a medium line by line to obtain image data for image recognition processing; image data of a background unit read before image reading of the medium body; A medium edge detection unit that detects the boundary with the image data by comparing the total sum of the image data for one line with a predetermined threshold, an image memory that stores at least the image data of the medium, and a reading unit from the start of reading. Waiting until the medium edge detection unit detects the boundary between the image data of the background portion and the image data of the medium body, and after writing a certain amount of the image data of the background portion from the image memory start address, the image data of the medium is written. An image reading apparatus comprising: a writing control unit that performs writing of the image.