JPH0120795B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a character reading device. In recent years, in the retail industry such as department stores and supermarkets, improvements have been made to improve customer service by shortening checkout time at checkout counters, to prevent input errors caused by incorrect key-ins, and to improve accounting management, inventory management, and replenishment operations using computers. In order to achieve automation, a device has been developed and put into practical use that manually scans the characters printed on product price tags, optically reads them, and automatically inputs them into POS devices.

Since such a character reading device scans characters on a form by manual scanning, the scanning speed varies. In order to deal with this variation, the character pattern observed by the scanner is output without distortion, and to simplify the subsequent recognition logic, a surface scanner with a two-dimensional array of photoelectric conversion element devices is used as a manual scanning character reading device. It is commonly used in

On the other hand, in conventional devices using such surface scanners, there is a method of reading the data using a similarity method as an identification processing method, but this method allows the design of comparison patterns to be automated and Although high identification performance can be obtained, the processing time increases as the number of character types to be read increases.
In order to cover the shortcomings of such identification processing methods,
The following measures are required to detect character patterns observed by a surface scanner.

In other words, the character pattern observed by the surface scanner is approximately in the center of the scanner's observation area, which is the condition that no part of the character pattern is missing and that there is no intrusion of adjacent characters in the character width direction. , and the projection in the character height direction.The character pattern detected in this way is identified and judged, and at the same time, the character pattern margin on the medium is determined by projecting the observation area in the character width direction. is detected, and it is determined that the observations are of the same character until the space between characters is detected.

However, if the scanner is moved diagonally with respect to the character string as shown in Figure 1a, then Figure 1b
If large characters are printed in part of the character string as shown in Figure 1c, if noise etc. appears in the margins between characters as shown in Figure 1c, or if the print density is too low as shown in Figure 1d. If the thin quantization pattern becomes discontinuous, the space between characters cannot be detected accurately. For this reason, the ability to skip letters,
Alternatively, the same character may be read and output multiple times. Furthermore, if the space between characters is not detected even after a certain period of time has elapsed after a character is detected, it is determined that the character line is at the end. Due to these factors, the allowable range of movement speed of the scanner has become narrow, and improvements have been desired.

SUMMARY OF THE INVENTION An object of the present invention is to provide a character reading device which eliminates the above-mentioned drawbacks and improves the flexibility of printing conditions and scanner movement speed.

According to the present invention, a scanner having a photoelectric conversion device consisting of two-dimensionally arranged photoelectric conversion elements is used as the scanner. Each photoelectric conversion element of the photoelectric conversion device is scanned in response to a clock pulse output from a scanning control section, and outputs an electrical signal corresponding to a character image projected onto the photoelectric conversion device. The photoelectric conversion device repeatedly outputs character images at a sufficiently fast cycle compared to the moving speed of the scanner itself. Hereinafter, this will be referred to as frame scanning. In a given frame, parts of each of two characters lined up on the medium will be observed simultaneously.

Therefore, it is determined whether the obtained observed pattern satisfies the detection conditions. Here, the detection condition indicates whether or not an observation pattern sufficient for character identification is obtained, and detects whether a part of a character is missing or whether a character exists. Character patterns are cut out from the observed patterns that satisfy this detection condition and sent to the identification section, where identification processing is started. On the other hand, the photoelectric conversion device similarly outputs an observation pattern in the next frame. It is quite possible that this observation pattern also satisfies the detection conditions. If the observation pattern detection condition is satisfied in consecutive frames, it is easily understood that the same character is actually observed in the consecutive frames. It is also understood that there must be some frames in which the detection condition is not satisfied before the next scanned adjacent character on the medium reaches a frame in which the detection condition is satisfied.

Therefore, in the present invention, means is provided for counting the number of frames of an observation pattern that satisfies the detection condition, and by counting and monitoring the number of frames of the observation pattern that does not satisfy the detection condition, it is possible to detect the same number of frames on the medium. It is configured to distinguish between characters and adjacent characters.

FIG. 2 is a diagram showing a scanner used in the present invention. Characters printed on medium 1 are illuminated by lamp 2. This reflected light is projected onto the photoelectric conversion device 4 through the lens 3 with an appropriate reduction ratio. The photoelectric conversion device 4 is, for example, m×n 2
It is composed of photoelectric conversion elements arranged in a dimensional array, and the output of each photoelectric conversion element is taken out in a scanning manner in response to a clock pulse output from a scan control section, which will be described later.
A group of electrical signals obtained by one scan (one frame scan) are analog signals each corresponding to the amount of projected light. This analog signal is taken out to the outside via the driver circuit 5.

FIG. 3 is a block diagram showing the overall configuration of an embodiment of the present invention. The analog signal taken out from the scanner 7 is converted into a 1/0 quantized signal by a quantization circuit 8. Hereinafter, this will be referred to as an observation pattern. An observed pattern in a certain frame consists of m×n quantized signals. The observed pattern is sent to the character detection and cutting section 9, and it is determined whether or not it satisfies the detection conditions. Character patterns (consisting of m'×n' quantized signals) are extracted from the observed patterns that satisfy the detection conditions and sent to the identification section 10. Identification unit 10
identifies character patterns using a similarity method, for example, and outputs the answer. The scan control unit 11 periodically scans the photoelectric conversion device 4 in the scanner 7 and generates a scan synchronization signal at the end of one frame.
Output EOF.

In general, when a manual scanner is used, the identification unit 10 outputs the reading results for one line at once when the reading for one line on the medium is completed.

FIG. 4 shows an example of the structure of the character detection and cutting section 9.
The quantization signal obtained from the quantization circuit 8 is supplied to a character width detection circuit 13, a character height detection circuit 14, and a detection cutting circuit 15, which are controlled by a control section 16. The character width detection circuit 13 has a character width direction projection register 17, and obtains the projection of the observed pattern in the character width direction. Character height detection circuit 1
Reference numeral 4 has a character height direction projection register 18 and a height counter 19, and calculates the projection of the observed pattern in the height direction and its height. Since these specific circuit configurations are well known, detailed explanation thereof will be omitted.

The control unit 16 is composed of, for example, a microcomputer, and controls each of the above-mentioned units, and uses data obtained by the character width detection circuit 13 and character height detection circuit 14 to ensure that the input observation pattern satisfies the detection conditions. Determine whether or not it is.

The character detection condition is checked to see if the character height is within a predetermined range. The character height detection circuit 14 uses an observation pattern 30 shown in FIG.
Row scanning 31 is performed sequentially in the column direction. Every time one line is scanned, it is determined whether or not there is black (character part 32) in that line, and at the time of EOC33 when two white lines are detected at the bottom of the character, for example, after a black line,
The length of the pattern projection 34 in the projection register 18 is determined by a height counter 19, and the determined height H is sent to the control section 16. The control unit 16 checks whether this value H is within a predetermined character height range, and if it is outside the range, it scans the next line and performs a new pattern detection operation. On the other hand, if the detected value H is within the specified character height range, the control unit 16 drives the character width detection circuit 13 to obtain pattern projection in the character width direction, and determines whether the detection conditions are satisfied. Check. The detection condition in the character width direction is satisfied if the pattern projection 35, assuming that the number of bits in the character width direction of the observed pattern is 12, matches any of the detection conditions (1) to (5) shown in FIG. shall be taken as a thing. In Figure 6, the hatched bits are always black (character parts), the blank bits are always white (background), and the bits marked with an x can be either white or black. .

In Figure 6, numbering from 1 to 12 from the left.
The example below shows an example consisting of 12-bit registers. For example, in the example of condition (1), bits 4 to 9
A necessary condition is that there is a projection of a character pattern on the first 6 bits, and that there is no projection of a character pattern on bits 1 and 12. In other words, in an example where an input character pattern is detected approximately at the center of a two-dimensional array of photoelectric conversion devices, characters with a character width of 1.2 mm (0.2 x 6 with a resolution of 0.2 mm) to 2.0 mm (0.2 x 10) are detected. Indicates a place where

The degree of freedom in condition (1) (that is, the number of bits marked with an x) is 4 bits, and there are 16 combinations of them.Similarly, condition (2) has 16 types, conditions (3) and (4) have 2 types each, and conditions There are four types of (5), and only 40 out of 4096 types, which are 12 bits in total, satisfy the detection conditions.

The conditions shown in Figure 6 are that the scanning time for one frame is 0.5.
msec, the resolution per photoelectric conversion element is set to 0.2 mm, and when the scanner scans a character with a character width of 8 bits at a moving speed of 0.2 mm/0.5 msec = 400 mm/sec, the detection conditions shown in Figure 6 are satisfied. (1), and the detection condition is such that detection is performed at each time of the n-th frame 41, the (n+1)-th frame 42, and the (n+2)-th frame 43 in FIG. 7 in the scanning movement direction. It is something that

In this way, for a character pattern with a character width of 1 to 12 bits observed at a moving speed of 400 mm/sec, by combining each detection condition shown in Figure 6, the detection condition can be satisfied at least three times. are given the opportunity to This shows that even when the moving speed of the scanner is tripled to 1200 mm/sec, characters can be detected without skipping characters.

On the other hand, under such detection conditions, if the movement of the scanner becomes significantly slow, the same character on the medium will be detected many times. For example, in the above example, if the moving speed of the scanner becomes 200 mm/sec, the detection condition will be satisfied 6 times, and if it becomes 40 msec, the detection condition will be satisfied 30 times. Therefore, if the identification process for one character in the identification unit 10 is completed in one frame, multiple identification results will be output for one character on the medium unless it is known that the same character is being detected. . Therefore, as will be described later, it is necessary to determine whether the same character or the next character is being detected.

Referring again to FIG. 4, when the control unit 16 determines that the observed pattern satisfies the detection conditions, it drives the detection cutout circuit 15. Since the configuration of the detection cutout circuit 15 is also well known, a detailed explanation will be omitted.
The character pattern portion is converted from the observed pattern into a predetermined size (m'×n'), and the identification unit 10
Transfer to the internal pattern memory. At this time, the control section 16 determines the center of the character pattern from the detected character width and character height data, and controls the detection cutting circuit so that the center of the character pattern coincides with the center of the pattern memory. When the transfer of this character pattern is completed, the control section 16 outputs an identification start signal to the identification section 10, and entrusts the following identification processing to a control section (not shown) in the identification section 10. Then, the control unit 16 similarly checks whether the observation patterns supplied in the following frames satisfy the detection conditions. If the observed pattern does not satisfy the detection conditions, the control section 16 does not drive the detection cutout circuit 15.

By the way, as mentioned above, when there is a character pattern that satisfies the detection condition in the i-th frame, the character patterns that satisfy the detection condition in subsequent frames are almost always the same as the character pattern in the i-th frame. It is. For this reason, the character detection and cutting section 9 is provided with a circuit to prevent the same character from being reread.

In Figure 4, flip-flop (PASS) 2
0 is set when a character pattern that satisfies the detection condition is detected, and is reset when a character pattern that satisfies the detection condition is no longer detected. A counter (SCTR) 21 counts the number of frames having a character pattern that satisfies the detection conditions. A counter (NSCTR) 22 counts the number of frames starting from frames that no longer satisfy the detection conditions. A selector (SEL) 23 selectively outputs a double value or a quadruple value of the count value of the SCTR 21. The comparator 24 compares the output of the SEL 23 and the output of the NSCTR 22, and outputs an identification permission signal if they match. Flip-flop (ABFF) 25 is set when projection register 17 is all black, and its output specifies a value four times SEL 23.

These operations will be explained with reference to FIG. This figure schematically shows the relative relationship between character strings on the medium and the projection register 7. 50 ₁ , 50 ₂
represents consecutive characters on the medium, and 51 to 58 represent character width direction projections obtained by the projection register 17 in a particular frame.

PASS20, SCTR21, and NSCTR22 are cleared before the first character ₅₀₁ of the character line is detected. 1st frame to (n-1)th frame
Since the projections 51 and 52 in the frame do not satisfy the detection condition, there is no change in the SCTR 21 and NSCTR 22. Since the projection 53 of the n-th frame satisfies the detection condition, the control unit 16 drives the detection cut-out circuit 15 and outputs an identification start signal (accordingly, the detection cut-out circuit 15 extracts the character pattern from the n-th frame). cut out and send to the identification section 10). Moreover, the control section 16
Set PASS20 and make SCTR21 countable. (After setting PASS20, control unit 16
does not drive the detection cutout circuit 15 until it receives an identification permission signal, which will be described later. ) SCTR21 is PASS2
Since it is connected to the Q terminal of 0, the scan control unit 1
It is incremented by 1 in synchronization with the frame synchronization signal EOF sent from 1. Since NSCTR22 is connected to the terminal of PASS20, it cannot be counted.

The projection 54 of the next (n+1)th frame also satisfies the detection conditions, but since the identification permission signal 27 has not been obtained, the control unit 16 does not drive the detection cutout circuit 15 and does not output the identification start signal (follows Tetsute (n+
1) The character pattern of the frame is not sent to the identification unit 10). However, SCTR21 is incremented by 1 in synchronization with EOF. SCTR21 is similarly incremented by 1 in the (n+2)th frame.

In the (n+3)th frame, the projection 56 does not satisfy the detection condition, so the control unit 16 clears PASS20. For this reason, SCTR21 was prohibited from counting.
The count value is held (here, 3). Instead, the NSCTR 22 starts counting in synchronization with EOF. Thereafter, frames that do not satisfy the detection conditions continue until the mth frame, so the number of frames is NSCTR
It is counted by 22. On the other hand, SEL23 recently
Based on the output of ABFF25, the double value of SCTR21 (6 in this case) is selected and supplied to COMP24. For this reason, the COMP 24 outputs the identification permission signal 27 when the count value of the NSCTR 22 reaches 6. When the control unit 16 receives this signal, it will have a new frame that satisfies the detection conditions.

If a character pattern that satisfies the detection conditions is obtained in the (m+1)th frame, the identification permission signal 27 has already been output, so the control unit 16 determines that the character pattern is new and drives the detection cutout circuit 15 to identify the character pattern. A start signal is output to the identification section 10 (therefore, the character pattern of the (m+1)th frame is sent to the identification section 10). In this way, it is possible to prevent the same character from being identified multiple times by considering the character pitch even though the detection condition is satisfied continuously. (Here, the (m+
1) It may happen that a character pattern that satisfies the detection condition is obtained in a frame, but the (m+1)th frame is a character pattern that does not satisfy the detection condition, and the subsequent frame is a character pattern that satisfies the detection condition. . In short, after the identification permission signal is given, the first frame that satisfies the detection conditions is subjected to identification processing. ) Figure 9 shows SCTR21 (solid line) and NSCTR22.
It is a graph showing the correlation between the count value change (broken line) and the state of PASS20 (Q) on the vertical axis and time on the horizontal axis. Here, a is the number of frames (according to SCTR 21) during the detection condition satisfaction period from time ta to tb, and the NSCTR 22 counts the number of frames during the subsequent detection condition unsatisfaction period from tb to td. The count value of the NSCTR 22 is compared with the double value 2a (dotted chain line) of the count value a of the SCTR 21, and when they match (te), the next character pattern identification process is allowed.

Furthermore, when ABFF25 is set, that is, when the slope of the character pattern is large or a large character pattern is observed as shown in Fig. 10a and b, SEL23 determines the number of subsequent frames in which identification is not permitted. 2 compared to the normal character width.
It is set to double.

Here, in the normal case, 2 of the count value of SCTR21
The reason for multiplying it was determined from the fact that the distance that satisfies the character detection conditions relative to the printed character pitch on the form is as small as approximately 3/12 (printing pitch 10 characters/inch), and the magnification was calculated using SEL23. The first thing that changed was
As shown in Figures a and b, when the detection condition is satisfied only on one side due to a large inclination or a large character being observed, the number of subsequent frames for which identification is not permitted is set to the normal number. This is because it is set twice as wide as the character width. The value of the magnification is just an example, and the value may be set based on the same idea based on the count value of the SCTR 21.

As described above, according to this embodiment, the number of frames that satisfy the detection conditions is counted, and in the frames determined according to the counted value, even if a character pattern that satisfies the detection conditions is detected, identification is not performed. do not have. In other words, since identification is not permitted after the first frame in which the detection condition is satisfied until the end of the frame period determined according to the count value, multiple identifications of the same character can be prevented by taking into account the character pitch. Therefore, the permissible range of the moving speed of the scanner can be greatly expanded compared to the conventional scanner.

With this invention, it is possible to scan in cases where the character width is large, when the inclination of the characters on the scanner and the medium is large, or when the printing contrast is low and the quantization pattern is output in pieces, and also under these conditions. To provide a character reading device with a high degree of freedom not found in conventional character reading devices, in which characters can be reliably detected regardless of whether the moving speed of the device is slow or fast, and multiple readings do not occur.

Furthermore, in the past, it has been thought that providing separate detection/judgment logic and identification processing circuits would not be compatible with the demands for lower cost and miniaturization, but detection/judgment logic is mainly based on sequential control; It is always easier to separate similarity calculation in processing and data processing for maximum similarity detection from the program control configuration, and it is smaller and cheaper than conventional methods. price has been achieved.

In this invention, the operation of determining the same character was explained using counters, flip-flops, etc., but these can be simplified by sharing them with other registers etc. using current program control technology. It is easy to imagine that this could happen.

Although this invention has been explained limited to characters, symbols,
It can also be applied to general pattern input such as symbols.

[Brief explanation of drawings]

Figures 1 a to d are diagrams showing an example of observing an input pattern in an observation area, Figure 2 is a diagram illustrating an overview of the medium and scanner, and Figure 3 is an overall block diagram of an embodiment of the present invention. , FIG. 4 is a block diagram of a part of an embodiment of the present invention, FIG. 5 is a diagram explaining the observation area, input character pattern, and its projection, and FIG. 6 shows the state in which the character width direction detection condition is satisfied. Figure 7 is a diagram illustrating the state of change in characters on the medium and the character width direction projection of the scanner, and Figure 8 is a diagram showing the period in which the detection is satisfied in the scanning state where space between characters is normally detected. 9 is a diagram explaining the operation of the counters SCTR and NSCTR, and the relationship with the output of the flip-flop PASS indicating the status of the same character period.
Figures a and b show a state in which the detection condition can only be satisfied on one side due to excessive inclination and excessive character width. 7...Scanner, 8...Quantization circuit, 9...Character detection cutting section, 10...Identification section, 11...Scanning control section, 13...Character width detection circuit, 14...Character height detection Circuit, 15...Detection cutting circuit, 16...Control unit.

Claims (1)

[Claims] 1 Two-dimensionally arranged photoelectric conversion devices,
means for periodically obtaining observation patterns by frame-scanning the photoelectric conversion device; means for determining whether or not the observation patterns satisfy predetermined detection conditions; and means for determining whether or not the observation patterns satisfy predetermined detection conditions; an identification unit that performs identification processing; a counting unit that counts the number of consecutive frames of observation patterns that satisfy a detection condition; a unit that supplies only the first observation pattern of the continuous frames to the identification unit; means for setting a frame period determined according to the counted value subsequent to the continuous frame targeted by the counted value, and prohibiting the identification unit from performing new identification processing during this period. A character reading device characterized by: