JP3343788B2 - Method and apparatus for scanning and decoding bar code symbols - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The invention of this application relates to a bar code reader, especially a scanner and a decoder. Conventional scanning / decoding methods employ a so-called fixed decoding time. In the invention of this application, data is invalid (invalid
As soon as d) is determined, adaptive logic is used, which immediately terminates the decoding process and starts the scanning process.

[0002]

BACKGROUND OF THE INVENTION There are several types of bar code readers, including those that scan a bar code using a laser beam and receive the reflected light to determine the reading of the bar code. I have. There are also several types of CCD units that capture a barcode image via a lens system. Bar code scanners that use laser beams require the vibration or rotation of a motor to drive a prism or laser beam in a scanning mode.
Moreover, the bar code is unreadable when exposed to sunlight, as it is affected by bright ambient light, and sometimes directly by the light source.

[0003] CCD barcode scanners, on the other hand, rely on enhanced ambient light for reading and provide a mechanical mechanism for scanning the beam.
and no need for laser light to read barcodes. The CCD scanner simply processes the barcode on a light-sensitive strip and the data is processed electronically.

In a conventional bar code league, one fixed portion during each scanning period is used for collecting bar code data, and another fixed portion during each scanning time is used for decoding the collected data. . However, in the invention of this application, the decoding / collecting scanning speed is increased, and the response of the barcode reader is greatly increased.

In a conventional CCD reader, an SOS
A signal called "start of scan" is used to distinguish data acquisition from data decoding. At one logic level of the SOS signal, data collection occurs during one fixed period. During this fixed period, data is shifted out of the CCD sensor in series. In addition, the microcontroller records the duration between when the barcode data changes from black to white and vice versa.

At other SOS signal levels, a fixed time period during the scan time is devoted to the microcontroller for decoding (analysis) of the recorded data. With the conventional method of fixing the duration of the SOS signal, the microcontroller must wait for the next level change of the SOS signal, no matter how soon it decides to validate or invalidate the data. On the contrary, the invention of this application
The signal allows its level (change point) to change under the control of the microcontroller. This means
This saves time that would be wasted waiting for SOS signal changes. Further, the ability to restart the SOS signal additionally allows time savings.

[0007] A fixed type (versio) according to the prior art
n), in the worst case, must wait for one full period of the SOS signal before starting data collection. However, the type according to the invention can simply restart the SOS signal and start collecting data.

[0008]

OBJECTS OF THE INVENTION It is therefore a first object of the present invention to improve the throughput of a CCD barcode scanner / decoder. It is a second object of the present invention to provide a CCD barcode scanner and decoder which increases the scanning speed for decoding and collecting barcode data in order to greatly speed up barcode reading. . A third object of the invention of the present application is to provide a bar code reader which has a simple design, is easy to manufacture, and has a reliable operation. Other objects and aspects of the invention of this application will become apparent from the following detailed description taken in conjunction with the accompanying drawings, which disclose embodiments of the invention of this application.

[0009]

To achieve the above object, a method and apparatus for scanning and decoding bar code symbols according to the invention of the present application generates an SOS (scan start) first level signal and an SOS second level signal. A microcontroller having a timing circuit for performing the scanning and a first level SO coupled to the microcontroller for viewing the barcode.
An image sensor for scanning a bar code in response to the S signal to generate a digital data signal representative of the bar code; and a digital device coupled to the image sensor and representing the bar code read by the image sensor. A memory device for storing a data signal therein, wherein the microcontroller identifies and decodes the stored data signal in the memory device when the SOS signal is at a second level to represent the bar code . Means for determining whether the digital data signal is valid or invalid and for restarting the SOS first level signal whenever the invalid bar code data signal is decoded.

[0010]

The SOS signal from the microcontroller is first set to the first signal level, and while the SOS signal is at the first signal level, a digital data signal representing a bar code is read from the CCD sensor and read from the CCD sensor. Storing the representative data signal in a memory, and determining and decoding the stored representative data signal while the SOS signal is at a second signal level to determine whether the representative data signal is valid or invalid. Whenever the invalid bar code data signal is decoded, restart the SOS first level signal immediately. As a result, the bar code data signal can be re-read without any waiting time.

[0011]

FIG. 2 shows the signal differences between the fixed and adaptive methods in relation to the scan start (SOS) signal. Figure
In 2A, the conventional CCD system is a fixed SOS
Signal, the CCD data is first collected during approximately the first half of the scan period, until the next collection signal is triggered.
Decoded during the second half of the scanning period. In the invention of this application, as shown in FIG. 2 B, the scanning start (SOS) signal,
Adapting to individual barcodes that are actually sensed, the data decryption following data collection is processed quickly, and the collection cycle is restarted more quickly as soon as the barcode is validated. Can be done.

[0012] Thus, the effective or as soon as the collection cycle invalid is validation of the bar code starts quickly, as shown in FIG. 2 A
It is not necessary to wait for a fixed amount of time to elapse as in the conventional system. The logic or signal level for data collection and decoding may be reversed. Then, when SOS is at logic "low", data collection occurs, and S
Decryption of data occurs when the OS is logic "high".

FIG. 1 shows an electrical block diagram of a CCD hand-held scanner / decoder 38 according to the invention of this application. The scanner is pointed at the barcode 30 to be read. These barcodes are a series of high and low reflectivity print bars. The former are known as spaces and the latter as bars. The images of these bars and spaces are projected onto the CCD / IC 32 by the optical unit 31. The optical unit 31 may be, for example, a combination of a lens and a mirror. In a preferred embodiment, the optical unit 31
Is a bar code 30, preferably 2 inches to 6 inches depending on the light sensitive area of the CCD · IC 32, is chosen so to obtain readings.

Depending on the optical system, the hand-held unit 38 can be moved closer to or farther away from the bar code 30 so that the bar code matches the focal position. At the focal position, the usable image is a CCD photosensitive pixel group (pixel).
s) clearly tied above 40 (see FIG. 5). CC
The D-IC 32 is preferably about 50.8 m above one line segment.
It has 2048 photosensitive pixel groups 40 arranged over m (2 inches). The width of each pixel is about 25.4 microns (1 mil). This means that for the narrowest bar of interest, 101.6 microns (4 mils) wide, 4 pixels will receive light information from that bar.

The light projected onto the CCD 32 is integrated over time. As a result, the brighter the projection target, the faster the signal will appear. That is, the charge and voltage of the sensor increase rapidly. After a fixed integration period, the signal on each pixel 40 is transferred to the analog shift register 41. To complete this process, the timing circuit 34 (FIG. 1)
At the rising edge of the SOS signal, the transfer pulse [T
P] signal. Next, the shift signals 1 and 2 shift each signal generated in each pixel toward the output terminal of the CCD 32.

The output (OS) of the CCD 32 is applied to a circuit 33 comprising an amplifier, a filter and a digitizer. Filters are used to remove unwanted components from the CCD output. The digitizer 33 is used to convert a signal into a digital signal. There, a logic high represents a bar and a logic low represents a space. The width of each digital pulse is proportional to the width of the printed bar or space. The digitized signal is applied to the microcontroller 35 as shown in FIG. Microcontroller 35 records the time at which any transition occurs for this signal, and stores that value in memory 51. In this way, a series of relative width values associated with all bars and spaces is generated. The microcontroller is
These values will be recorded until the SOS signal goes to a logic low, ie, the second signal level.

Once at the second signal level, the data is analyzed for validity. The validity of the data is determined based on whether or not the standards defined in a symbol specification, for example, "ANSI (American National Standards Institute) Standard" are satisfied. If the data represents a valid barcode, the data is converted by the microcontroller 35 to ASCII symbol (American standard code for information exchange) characters and sent out of the interface circuit 36. After the failure of the data transmission or the validity test, the microcontroller 35 restarts the timing circuit (SOS timer) 34. Then, the next data collection starts.

FIG. 3 shows a software flow diagram for a conventional fixed scanning / decoding technique. Start (en
ter) Block 11 is achieved by the operator pressing a start trigger on the CCD unit. The microcontroller then continues to sample the SOS signal until it detects a positive rising edge (blocks 12 and 13). Since the SOS signal is asynchronous to the microcontroller, it may use up one cycle time of the SOS signal to complete the sampling process. This time cycle is representative of the latency period, which is eliminated with the adaptive technique of the present invention. Subsequently, in the next three blocks 14, 15, and 16, the data of the CCD signal is converted into a number proportional to the pulse width and stored in the memory 51 of the microcontroller until the SOS signal reaches the second signal level. You.

Next, an attempt is made in the data decryption block 17 to convert these numbers into a series of ASCII characters. If the data cannot be converted, the flow (f
low) causes block 12 to go backwards. Because the time required for data removal varies widely, the SOS signal is in a random phase when block 12 is started. Thus, the system must wait or waste one full period of the SOS signal. If block 17
When the data has been successfully (effectively) converted, the data is transmitted at block 19 to other device components, such as a cash register or a computer. At this point, block 12 is started.
Since block 12 starts with a random phase, a time penalty is inevitable.

FIG. 4 shows a software flow diagram for an adaptive scanning / decoding technique according to the present invention. As described above, the start block 20 is achieved in response to the operator pressing the start switch. Microcontroller 3
5 restarts the SOS signal at block 21 and forces it to the first signal level. For this reason, FIG.
There is no waiting time as in the conventional method. Next, SOS
While the signal is at the first signal level, blocks 22, 2
At 3 and 24, the data is converted to a number and stored in memory 51.
(RAM).

In block 25, the validity is checked all at once. If the data is invalid, block 21 is restarted. Otherwise, at block 26 a more rigorous (precise) validation and decryption is performed. If then, block 27
In, if it is confirmed that the data is invalid, the block 21 is restarted. If the data was successfully decrypted, the data is sent to an external device at block 28. As a result, block 21 is restarted and the process is repeated.

It is important to note that there is no need for the microcontroller 35 to wait for the SOS signal to reach the first signal level. Microcontroller 35
Restarts the SOS signal immediately after the data is confirmed invalid in block 25 or 27, or after the data is confirmed valid in block 28. Once a valid ASCII character chain has been generated, the chain is applied from an output terminal of the microcontroller 35 to an interface 36 connected to its readout terminal (not shown). By shortening the data processing cycle, the system according to the invention of this application allows for faster reading and validating existing barcodes.

In the hand-held scanner according to the present invention,
The CCD unit will have the ability to scan barcodes under most ambient light conditions. Moreover, according to the invention of this application, a small LED 50 can be attached to a handheld scanner as an illumination light source, and can be directed to a barcode. Barcodes can be read without ambient light, and can be read under extremely high brightness conditions as well. Because no laser beam or mechanical scanning device is required, this hand-held unit can be manufactured at a lower cost than many current laser scanning devices.

The hand-held scanner according to the invention of the present application is also more reliable due to the absence of a scanning device and a laser light source, and does not cause the problem of breakage in the event of a fall. Moreover,
Since no scanning laser beam is used, there is no health hazard to the eyes of the user or the person standing by the scanner.

FIG. 7 is an electrical block diagram similar to FIG. 1, with an LED driver 49 added. LE
The D driver 49 is coupled to the microcontroller 35 and the plurality of LEDs 150. The microcontroller 35 causes a plurality of LED diodes 150 directed to illuminate the barcode 30 to flash. LE
When D150 is pulsed at a high current, the bar code 30
It is known that the LED 150 flashes with greater illuminance above, actually reducing the shutter speed and thus increasing the sensitivity of the bar code reader.

FIG. 8 is a software flow diagram for the program in microcontroller 35 used to flash LED 150, and FIG.
FIG. 4 is a diagram illustrating an increase in light emission duration related to an S signal.
FIG. 8 is a software flowchart for the shutter speed optimization system. In the figure, "flash emission time" is a variable and is used for setting the flash duration. Start block A is achieved as a result of the operator pressing a start trigger on the CCD unit.

In block B, the variable "flash emission time" is initialized to a minimum value. Next, in block C, the SOS is restarted. Immediately after that, block D
, The strobe light is flashed for a period determined by the current value of the variable 'flash emission time'. Next, in block E, the microcontroller 35 reads the data from the CCD and stores it in a memory buffer. In block F, the program waits until the SOS signal goes to a logic low. Next, in block G, to determine if the valid barcode is legible,
The buffer data is analyzed.

At block H, a conditional branch is executed. If there is a valid barcode, at block K, the data is transmitted through interface hardware to a component of the external device, such as a cash register or computer. If the test result in block H fails (absence of valid barcode), then in block I the data is examined and the data indicates that the barcode is present but is not validated because the exposure is too low. Check whether you are doing. The criterion for passing this test is that the buffer contains a certain minimum number of bar-to-space transitions. The number of transitions when the scanner scans an empty space is less than when it approaches a barcode.

In block I, if this test passes (is the bar code present?), Block J
Is tested to see if the 'flash duration' (variable) is at a maximum. If the 'flash duration' (variable) has not reached the maximum value, in block L the 'flash duration' (variable) is increased by one. If the 'flash duration' (variable) has reached the maximum value, the 'flash duration' (variable) remains unchanged. The above cycle
Thereafter, the process is repeated by restarting the block C. Thus,
When the scanner is close to the barcode, the 'flash emission time' (variable) of the LED will change until the valid reading is obtained.
As shown in FIG.

In a practical embodiment, the sensor 32 is
Toshiba TCD131D, CC with 2048 pixels
The D-line image sensor has been selected. As the microcontroller 35, Hitachi 6301Y is selected.
Interface 36 is a MAXIM MA
X232 has been selected.

The "39 barcode" was introduced in 1974 in a full alphanumeric format for data entry systems.
eric) developed as a barcode. This barcode is particularly effective for applications that use alphanumeric data for item recognition. The "39 barcode " structure allows printing with a wide variety of technologies including offset printing, letterpress, fully formed impact printers, dot matrix printers, and non-impact printing devices.

Current applications include inventory control, work in process manufacturing, trucking, wholesale distribution, hospital, government and retail point of sale management. "39 Barco
" D " is the most widely used alphanumeric bar code. It is accepted by many companies and industries as a standard code. "Standards for barcode symbols on transport packages and unit loads" (Specific
ation for Bar Code Symbol
s on Transport Packages &
Unit Loads) ANSI draft MH10. X-1981 describes three different bar code symbologies. "39 barcode "
Is called "3 of 9" (3of9) in the ANSI standard. Furthermore, the Ministry of Defense MIL-STD-1189 (19
(January 4, 1982) is a standard symbol for marking "39 barcode " (called "3 of 9 code") on unit packs (large packages), outer containers, and selected documents. Defined as notation.

In the above, only some embodiments according to the invention of the present application have been shown and described in detail. However, these drawings are made for the purpose of explanation only, It does not define the limitations of the invention of this application. In addition, many changes and modifications can be made to the above-described embodiment of the present invention without departing from the spirit and scope of the present invention.

[0034]

The invention of this application is configured as described above, so that the following first to third effects can be obtained. The invention of this application can, firstly, improve the throughput of CCD barcode scanners and decoders. Second, the scanning speed for decoding and collecting barcode data can be increased, and barcode reading can be significantly speeded up. Third, the design of the barcode reader can be simplified, manufacturing can be facilitated, and operation reliability can be improved.

[Brief description of the drawings]

FIG. 1 is an electrical block diagram of a barcode scanner according to the present invention.

FIG. 2 shows the scanning speed according to the prior art and the scanning speed according to the invention of the present application.

FIG. 3 is a software flow diagram of a non-adaptive prior art system.

FIG. 4 is a software flow diagram of the adaptive system according to the invention of this application.

FIG. 5 is an electrical diagram showing a configuration of a CCD linear image sensor having a plurality of pixels for sensing a barcode image.

FIG. 6 is a digitized signal generated by a bar code reader according to the invention of this application.

FIG. 7 is an electrical block diagram of a second embodiment of the barcode scanner according to the present invention.

FIG. 8 is a software flow chart of the second embodiment shown in the block diagram of FIG. 7;

FIG. 9 is a comparison diagram between the scan speed according to the invention of the present application for data collection and decoding and the flash emission time of the LED of the circuit according to the invention of the present application.

[Explanation of symbols]

Reference Signs List 30 barcode 31 optical system 32 integrated circuit CCD 33 composite circuit including amplifier, filter and digitizer 34 timing circuit 35 microcontroller 36 interface 38 handheld scanner / decoder 40 pixel 41 analog shift register 49 LED driver 50 LED 51 random access memory ( RAM) 150 LEDs

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Wen Yu Han United States of America New Jersey 07627, Demarest, 2 Hardenberg Avenue 134 (72) Inventor Gerrard Jay Knight United States of America 11767, New York, Nesconsett, Shady Praise 7 (72) ) Inventor Jackson Lamb United States 11576 New York, Balstor Cycle, Rosslyn 339

Claims (17)

(57) [Claims] With 1. A add bar code symbol with a view to use an image sensor coupled to a memory with the signal processing device, a method of scanning and decode the bar code symbol, scanning from the signal processing unit Setting a start signal or SOS signal to a first signal level (a); reading a digital data signal representative of a bar code from a CCD sensor while the SOS signal is at the first signal level (b); representative of the bar code read from the CCD sensor
(C) storing a digital data signal to be stored in a memory when the SOS signal is at a second signal level to determine whether the digital data signal representing the bar code is valid or invalid. (D) verifying and decoding the signal; and whenever the invalid bar code data signal is decoded,
To repeat the steps (a), containing the step (e) immediately restarts the SOS first level signal to re-read the bar code data signals from the CCD sensor has put a bar code on the field, the to, a method of scanning and decode the bar code symbol. 2. A method of scanning and decrypting the bar code symbol according to claim 1, moreover, whenever it is confirmed whether or invalid digital data signal is effectively representative of the bar code, the bar code symbol A method of scanning and decoding bar code symbols that immediately restarts scanning. 3. A method of scanning and decrypting the bar code symbol according to claim 2, moreover, after the step (d), representative of the bar code
When the digital data signal is confirmed to be valid at any time, to repeat the step (a), contains the step immediately restarts the SOS first level signal, thereby, the duration of the SOS second level signal how to minimize, maximize CCD data collection scan speed, scan and decode the bar code symbol. 4. A method of scanning and decrypting the bar code symbol according to claim 3, moreover, the step of reading (b) is representative of the bar code
Digital the barcode <br/> data signals to produce a data signal containing the filtering and de-I digital step of reduction, a method of scanning and decode the bar code symbol to be. 5. A method for scanning and decoding bar code symbols according to claim 3 , further comprising the step of illuminating said bar code symbols using ramp means in response to said SOS signal. a method for scanning and decrypting the bar code symbol. 6. A method of scanning and decrypting the bar code symbol according to claim 3, moreover, the timing circuit to restart the SOS signal in response to an output of the microcontroller additionally used, the timing circuit is coupled to the shift register of the CC D sensor, a method of scanning and decode the bar code symbol. 7. A method of scanning and decrypting the bar code symbol according to claim 6, moreover, the shift bar code data signal is the timing circuitry collected from the shift register of the CC D sensor to the microcontroller to, a method of scanning and decode the bar code symbol. 8. A method of scanning and decoding bar code symbols according to claim 5, further comprising the steps of: determining whether the image sensor is scanning a valid or invalid bar code symbol. Examining the stored data signal of d), "flash duration" as a variable to give to the LED lamp in response to step (e) where the bar and space are scanned
The increases in accordance with the determined order, and additionally containing the step of resetting the minimum value of the above "flash radiation time" in response to step (f) when a data signal has been confirmed as valid, the bar code symbol How to scan and decode. 9. A method for scanning and decoding bar code symbols according to claim 8, further comprising an LED driver coupling said microcontroller to said LED lamp, said microcontroller triggering said SOS signal. sometimes, increasing the "flash radiation time" before symbol LED lamp, a method of scanning and decode the bar code symbol. 10. An apparatus for scanning and decoding bar code symbols, comprising: a microcontroller having a timing circuit for generating an SOS first level signal and an SOS second level signal; and a bar code symbol coupled to the microcontroller. an image sensor for scanning a bar code symbol in response to an SOS first level signal and generating a digital data signal representative of the bar code; and an image sensor coupled to the image sensor. contains a memory device for storing therein the digital data signal representative of the bar code read by said microcontroller, check the stored data signals in the memory device when the SOS signal is at the second level And decode the digital data signal representing the bar code
No. is enabled or disabled or to determine and invalid bar code data signal to scan and decrypt the bar code symbol containing means to restart immediately SOS first level signal whenever the decrypted device. 11. The image sensor according to claim 1, wherein the image sensor is a charge-coupled device (C).
CD) cell is a capacitors, scanning a bar code symbol according to claim 1 0, wherein and decryption devices. 12. invalid bar code as soon as the data signal is decoded SOS first level signal is restarted, wherein the bar code symbol to re-read the bar code data signals from the CCD sensors with a view an apparatus for scanning and decode the bar code symbol of claim 1 1, wherein, whenever a bar code data signal is confirmed as invalid, and said microcontroller is immediately restarted SOS first level signal, the bar code By re-acquiring the data signal , thereby minimizing the duration of the SOS second level signal, and immediately restarting bar code symbol scanning whenever the bar code data signal is verified as valid or invalid. , CCD data collection scanning speed is maximized, scanning and decrypting an apparatus for bar code symbol. 13. A device for scanning and decrypting the bar code symbol according to claim 1 wherein, moreover, the noise and unwanted signals from the data signal is removed and the bars
An apparatus for scanning and decoding bar code symbols , which additionally includes a filter and a digitizer for generating a digital data signal representative of the code . 14. In response to the SOS signal containing lamp device for illuminating the bar code symbol, according to claim 1 2 scan and decode an apparatus for bar code symbol according. 15. A device for scanning and decrypting the bar code symbol according to claim 1 3, wherein, moreover, is coupled to the microcontroller, the LED driver circuit having an output terminal coupled to the prior SL LED lamp, the in response to the SOS signal and the microcontroller, additional and means for increasing pre Symbol a "flash radiation time" before Symbol LED lamps between from time representative data is invalid until the time the data signal is valid scanning and decryption to apparatus comprising, a bar code symbol. 16. A scanning and apparatus for decoding the bar code symbol according to claim 15, moreover, the means for increasing the "flash radiation time", to the LED lamp immediately after reading of the first invalid signal current is increased in the form of plus a first increment variation in the initial value, is increased more effective until the bar code is read the current to the previous SL LED lamp incremental variation of the form, current to且the LED lamp Device for scanning and decoding bar code symbols , including means for resetting the bar code symbol to an initial value . 17. An apparatus for scanning and decoding bar code symbols, comprising: a microcontroller having a timing circuit for generating an SOS first level signal and an SOS second level signal; and a microcontroller coupled to said microcontroller for converting the barcode. Into the field of view, scan the barcode in response to the SOS signal,
It contains an image sensor for generating a digital data signal representative of the bar code, coupled to said image sensor, and a memory device for internally storing representative data signals read by the image sensor, the microcontroller Identifies and decodes the stored data signal in the memory device when the SOS signal is at the second level, and provides a digital data representative of the bar code.
An apparatus for scanning and decoding bar code symbols , comprising means for determining whether the signal is valid or invalid and controlling the duration of time the SOS signal is at a second level as a function of the validity of the bar code data signal.