JP4161907B2 - Information code reading system and method for determining illumination time of information reading device - Google Patents

Description

  The present invention includes a camera device that captures an image in a fixed arrangement, an illumination device that illuminates an imaging target of the camera device, and an information reading device that decodes an information code read by the camera device. And an information code reading system and a method for determining a time at which the information reading device causes the lighting device to perform illumination.

In Patent Document 1, light from a light source is emitted to a test pattern in which information is recorded in a predetermined pattern, and an orientation pattern obtained by a read signal output from a light receiving unit that receives reflected light and a preset ideal pattern. A light source adjustment method for a barcode reader is disclosed in which the light emission time of the light source when the deviation between both is within a certain value or less is initially set as the best light emission time.
JP-A-9-6890

  However, in general, environmental conditions for reading information codes that are optically read, such as barcodes and two-dimensional codes, are generally easily changed. For example, assuming that an information code attached to a product conveyed on a production line is read, the ambient illuminance changes due to external light, or individual differences between products in the production process (manufacturing variation, information code (Including the variation of the application state) also exists as a variation factor. Therefore, when the ideal orientation pattern is fixedly set, there is no guarantee that it matches the actual reading environment.

  In Patent Document 1, the initial setting is made assuming that the light emission time is the best when the difference in light intensity between the portions in the alignment pattern based on reading and the ideal alignment pattern falls within a certain value. However, in consideration of the change in the environmental conditions as described above, the fact that the difference in light intensity is within a certain value does not necessarily indicate the ideal reading condition of the information code.

  Further, the system for reading the information code has a camera device, an illumination device, and a reading device that decodes the information code, each of which is a separate device so as to have flexibility to cope with each user's application. There are many cases that are configured in combination. When such a system configuration is adopted, it is not easy to change the shutter time for the camera device to read the information code, and for example, a troublesome operation such as changing a jumper switch setting is required. Therefore, when setting the optimal illumination time in the illumination device in such a system configuration, the shutter time set in the camera device must be premised, but with the technique disclosed in Patent Document 1, Since the preconditions are different, it cannot be applied as it is.

  The present invention has been made in view of the above circumstances, and an object thereof is to optimally set an illumination time in a system configured by combining a camera device, an illumination device, and an information reading device. .

  According to the information code reading system of claim 1, when the information reading device detects the shutter time based on a control signal transmitted to and received from the camera device that performs imaging in a fixedly arranged state, the shutter time is detected. The lighting time of a plurality of stages is determined with the upper limit of. The information codes read when the illumination device is illuminated for each illumination time are decoded, and the illumination time with the best reading state evaluated for each decoding result is given priority in the subsequent reading processing. To set.

Therefore, since the subsequent reading process is attempted with the illumination time in which the reading state is the best within the range of the shutter time set in the camera device, the illumination conditions suitable for the system configuration and the actual environmental conditions are set. Can be set. And, unlike the prior art, instead of setting the light emission time when the light intensity of the reflected light is in a predetermined state, it sets the illumination time when the reading state evaluated based on the decoding result is the best. It is possible to set an optimal illumination time that matches the reading environment conditions in the.
Then, the information reading device detects, as the shutter time, the time from when the imaging start signal is transmitted to the camera device until the image data output start signal output by the camera device is received. That is, when the imaging start signal is given, the camera device opens the shutter to capture the information code pattern, and when the shutter is closed and the imaging is completed, the camera device starts data output to transmit image data to the information reading device side. A signal indicating is transmitted. Accordingly, when viewed from the information reader side, the input / output interval of these two signals corresponds to the shutter time, so that the shutter time can be detected easily and accurately.

  According to the information code reading system of the second aspect, the information reading apparatus evaluates that the number of times of error correction processing generated when decoding the information code is smaller, that the reading state is good. In other words, if the reading state is good, the number of error correction processes should be reduced. Therefore, with this configuration, the reading state can be evaluated appropriately.

According to the information code reading system of claim 3 , when the reading performed by setting any lighting time among the plurality of selected lighting time candidates fails, the information reading device has the next highest priority. Set a high illumination time for and retry reading. That is, as described above, since the reading environment condition of the information code is likely to fluctuate, there is no guarantee that the illumination time when the reading state is best at a certain point in time will always provide the best reading state after that. . Therefore, with such a configuration, even if reading fails, there is a possibility that subsequent readings will be performed normally.

According to the information code reading system of claim 4 , when an information reading device having a high reading success frequency other than the preferentially set lighting time appears, the information reading device preferentially sets the lighting time having a high success frequency. Switch as follows. That is, since the reading environment condition of the information code is likely to fluctuate as described in claim 4, the illumination time for providing the best reading condition may vary from time to time. The illumination time can be set more flexibly to improve the possibility of correct reading.

According to the information code reading system of the fifth aspect , the information reading device sets an unselected illumination time out of a plurality of stages of illumination time when reading fails due to any of the plurality of selected illumination time candidates. And try reading. In other words, depending on fluctuations in the reading environment conditions, it is assumed that the illumination time in which the reading state was not necessarily good before is now a condition that gives a good reading state. Therefore, if configured in this way, the possibility of correct reading can be further improved.

(First embodiment)
Hereinafter, a first embodiment in which the present invention is applied to an information code reading system for reading a QR code (two-dimensional code), which is a kind of information code, will be described with reference to FIGS. . FIG. 4 shows the configuration of the information code reading system. The information code reading system is mainly composed of a CCD camera (camera device) 1, an LED illumination device 2, and a decoder (information reading device) 3. In the CCD camera 1, the QR code reading timing is controlled by the decoder 3, and the QR code image data read by the CCD camera 1 is transmitted to the decoder 3.

  The LED illumination device 2 is configured by, for example, a plurality of LEDs (not shown) arranged in a ring-shaped frame, and is arranged coaxially with the imaging center of the CCD camera 1 as shown in FIG. Illuminate the object to be imaged. The LED lighting device 2 is also controlled to be turned on / off by the decoder 3. FIG. 5 shows a case where the QR code 5 that is directly marked on the circuit board 4 conveyed on the production line using a laser beam or the like is read by the CCD camera 1. The apparatus 2 reads the QR code 5 marked on the circuit board 4 passing under the line information while being fixed to the line information.

  The decoder 3 decodes the QR code image data transmitted from the CCD camera 1, and is given a control command by a personal computer 6 (or a sequencer) as a host controller. Information obtained as a result of decoding by the decoder 3 is transmitted to the personal computer 6 side. The decoder 3 is connected to an NTSC monitor TV 7, a mouse 8, and the like. The image data captured by the CCD camera 1 is displayed on the monitor TV 7, information obtained as a result of decoding is displayed, and a monitor is displayed. The menu screen displayed on the television 7 can be operated with the mouse 8.

  FIG. 6 schematically shows the electrical configuration of the decoder 3. Image data transmitted from the CCD camera 1 is input via an image signal input interface (I / F) 10 to a control circuit 9 which is mainly composed of a microcomputer and performs overall control and decoding processing. The control circuit 9 inputs and outputs control signals to and from the CCD camera 1 via the camera control interface 11.

  Further, the control circuit 9 performs turning on / off control of the LED lighting device 2 via the illumination control interface 12 and receives an operation signal of the mouse 8 via the mouse interface (for example, PS / 2 (registered trademark)) 13. . Further, the control circuit 9 outputs an image signal to the monitor television 7 via the monitor interface (NTSC) 14 and communicates with the personal computer 6 via the communication interface (for example, RS-232C) 15.

  The decoder 3 includes an amplifier circuit 17, an A / D conversion circuit 18, a memory 19, a specific ratio detection circuit 20, a synchronization signal generation circuit 21, an address generation circuit 22, etc., which are also controlled by the control circuit 9. It has become so. As a result, the image pickup signal from the CCD camera 1 is amplified by the amplifier circuit 17, converted into a digital signal by the A / D conversion circuit 18, and stored in the memory 19 as image data. At this time, a specific pattern in the image data is detected by the specific ratio detection circuit 20. A synchronization signal is supplied from the synchronization signal generation circuit 21 to the light receiving sensor 3, the specific ratio detection circuit 20, and the address generation circuit 22.

Next, the operation of the present embodiment will be described with reference to FIGS. FIG. 1 is a flowchart showing the contents of the illumination time adjustment process performed by the control circuit 7 of the decoder 3 when the power is turned on. When this adjustment process is performed, a QR code 5 as a test sample to be read by the CCD camera 1 is prepared.
First, as shown in FIG. 3A, the control circuit 7 outputs a VD signal as an imaging start signal to the CCD camera 1 (step S1), and starts counting by an internal timer (step S2). . Then, the CCD camera 1 opens the shutter, images the QR code 5 image data, and when the imaging is completed, transmits the VI signal indicating the start of data output to transmit the image data to the decoder 3. (See FIG. 3B).

  Therefore, the control circuit 7 waits until the VI signal is input (step S3). When the VI signal is input ("YES"), the timer count value TS at that time is read (step S4). That is, the time from when the VD signal is output until the VI signal is input corresponds to the shutter opening time set in the CCD camera 1. Note that the purpose of the processing so far is to detect the shutter time of the CCD camera 1, so there is no need to turn on the LED illumination device 2.

  Next, when the control circuit 7 calculates the minimum unit TU of the illumination time by, for example, 1/16 of the count value TS (step S5), the value of the counter n is initialized to “1” (step S6). . Then, when the illumination time TLn for turning on the LED illumination device 2 is set as n · TU (step S7), a VD signal is output to the CCD camera 1 and the LED illumination device 2 is lit for the illumination time TLn. 5 is read (step S8).

  Subsequently, the control circuit 7 takes in the image data transmitted after receiving the VI signal from the CCD camera 1, and performs a decoding process of the image data (step S9). During the decoding process, the number of times that 1-bit error correction has occurred due to the Reed-Solomon code incorporated in the QR code 5 is written and stored in the memory 19 (step S10). If the value of the counter n has not reached “16” (step S11, “NO”), the counter n is incremented (step S12) and the process returns to step S7.

As described above, the processes in steps S7 to S12 are repeated until “n = 16”. That is, as shown in FIG. 3C, each time the loop is repeated, the illumination time TLn gradually increases by the minimum unit TU. As the illumination time TLn changes, the reading state of the QR code 5 changes. When “n = 16” is reached (step S11, “YES”), the control circuit 7 selects the top four illumination times in which the number of error corrections is small among the readings performed 16 times (step S13). The process ends.
The four illumination times selected here are used when a normal reading process is performed thereafter. Then, priorities (1 to 4) are assigned from the one with the smallest number of error corrections, and the first illumination time used in the subsequent reading is set to the priority “1”.

  FIG. 2 is a flowchart showing the processing contents when the control circuit 7 of the decoder 3 reads the QR code 5 in the normal operation state. The control circuit 7 waits until a read start control signal is given from the personal computer 6 as a host (step S21). When the control signal is given ("YES"), the set priority order is the highest. The QR code 5 is read in the illumination time (priority order 1) (step S22).

As a result of decoding the read data, if the reading is successful (step S23, “YES”), the processing is terminated. On the other hand, when the reading has failed (“NO”), the control circuit 7 performs the reading process with the next illumination time (priority order 2) (step S24), and returns to step S23. That is, until reading is successful
Priority: 1 → 2 → 3 → 4 → 1 → 2 → ・ ・ ・
To repeat the reading process.

  As described above, according to the present embodiment, the decoder 3 of the information code reading system receives the control signal transmitted / received to / from the CCD camera 1 that images the QR code 5 while being fixedly arranged on the production line. Based on this, the shutter time TS set in the CCD camera 1 is detected, and the 16-stage illumination time TLn is determined with the shutter time as the upper limit. Then, the QR code 5 read when the LED lighting device 2 is illuminated in each illumination time TLn is decoded, and the illumination time TLn in which the reading state evaluated for each decoding result is the best is hereinafter The priority is set in the reading process.

  Therefore, since the subsequent reading process is attempted within the illumination time TLn in which the reading state is the best within the range of the shutter time set in the CCD camera 1, illumination suitable for the system configuration and the actual environmental conditions. Conditions can be set. And instead of setting the light emission time when the light intensity of the reflected light is in a predetermined state as in the prior art, the illumination time TLn is set so that the reading state evaluated based on the decoding result is the best. It is possible to set an optimal illumination time that matches the reading environmental conditions at the time.

In particular, when the QR code 5 is directly marked on the circuit board 4 using a laser beam or the like, it is assumed that the marking state (shallow, deep, etc.) differs for each lot of the circuit board 4. In this case, it is possible to set a good reading state flexibly.
Further, since the decoder 3 evaluates that the read state is good when the number of times of error correction processing that occurs when the QR code 5 is decoded, the evaluation can be performed appropriately. Furthermore, since the decoder 3 detects the time from when the VD signal is transmitted to the CCD camera 1 until the VI signal is received as the shutter time TS, the shutter time can be detected easily and accurately.

  In addition, when the reading performed by setting any lighting time TLn among the plurality of selected lighting time candidates fails, the decoder 3 sets the lighting time with the next highest priority and reads. Try again. That is, since the reading environment condition of the QR code 5 is likely to fluctuate, there is no guarantee that the illumination time TLn that is considered to be the best reading state at a certain time always provides the best reading state. For example, the longer the illumination time, the better the reading state will not be, and if the illumination is too strong, the bright / dark pattern difference of the QR code 5 becomes too small, and it may be assumed that the reading cannot be performed normally. Therefore, if the reading is retried while changing the illumination time, even if reading fails at a certain point in time, there is a possibility that reading after that will be performed normally.

(Second embodiment)
FIG. 7 shows a second embodiment of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted. Only different parts will be described below. FIG. 7 is a view corresponding to FIG. 2 in the first embodiment. In the second embodiment, if “NO” is determined in step S23, the control circuit 7 increments the number of use frequencies for the illumination time for which reading is successful and stores the incremented frequency in the memory 19 (step S25). Then, when the lighting time with the highest use frequency at that time is set to the highest order (step S26), the process is terminated. Accordingly, the illumination time selected in step S22 every time the QR code 5 is read is set to the highest rank in step S26.

  As described above, according to the second embodiment, the decoder 3 preferentially sets an illumination time with a high success frequency when a high read success frequency appears in addition to the illumination time set with priority. I switched. That is, since the reading environment condition of the QR code 5 is likely to fluctuate, the illumination time for providing the best reading condition may change from time to time, so that the best illumination time can be set more flexibly and the reading can be performed correctly. The possibility can be improved.

(Third embodiment)
FIG. 8 shows a third embodiment of the present invention, and only the parts different from the first embodiment will be described below. In FIG. 8 corresponding to FIG. 2, when the control circuit 7 of the decoder 3 determines “NO” in step S23, it uses the lowest rank (eg, “4”) in step S24 among the selected illumination time candidates. It is determined whether or not reading has been attempted (step S27). And if it is judged as "NO", it will transfer to step S24.

On the other hand, if the lowest rank “4” has already been selected in step S24 and “YES” is determined in step S27, the top four initially selected in step S13 among the 16 levels of illumination time set in the process of FIG. Among the other illumination times, the one with the highest ranking (here, “5”) is selected and read (step S28). Then, the process proceeds to step S23 to determine whether the reading is correct.
Also in this case, if reading fails and the process reaches step S27, S28, in step S28, reading is performed by selecting “6” in the next order among the illumination times not selected in step S13. Like that. Thereafter, the same processing is performed.

  As described above, according to the third embodiment, when reading fails due to any of the plurality of illumination time candidates originally selected in step S13, the decoder 3 sets the illumination time that is not selected in step S13. And try reading. In other words, depending on fluctuations in the reading environment conditions, it is assumed that the illumination time in which the reading state was not necessarily good before is now a condition that gives a good reading state. Therefore, if configured in this way, the possibility of correct reading can be further improved.

The present invention is not limited to the embodiments described above and shown in the drawings, and the following modifications or expansions are possible.
In the first embodiment, the number of illumination time candidates to be selected with priorities is not limited to four, and may be three or less or five or more. Further, only one with the highest ranking may be selected as a candidate.

When determining the minimum unit of the illumination time, it is not limited to 1/16 of the shutter time, and may be determined at a necessary ratio as appropriate.
Further, the stage of changing the illumination time does not necessarily have to be set as a multiple of the minimum unit of the shutter time equally divided. As long as the shutter time is the upper limit, any time difference may be set within the range.

  The first embodiment may be implemented as follows. For example, when there is a possibility that four types of information codes may flow on the production line, the illumination time that optimizes the reading state is selected one by one. In the first embodiment, four types of illumination times are automatically switched and repeatedly executed until reading is successful. Therefore, even when reading is performed in a state where four types of information codes are mixed, Each can be read in an optimal state without being aware of the difference.

You may implement combining 2nd Example and 3rd Example.
The evaluation of the reading state is not limited to a method based on the number of error corrections. For example, it may be evaluated that reading with the same illumination time is repeated a plurality of times, and a reading with a large number of successful readings is good.
The information to be read is not limited to the one marked on the circuit board 4, but may be an information code marked on another metallic casing or packaging cardboard box. Moreover, it is not restricted to what is direct-marked, You may attach the sticker of the information code printed beforehand.

  The information code to be read is not limited to the QR code 5, but other two-dimensional codes such as micro QR code (registered trademark), DataMatrix (registered trademark), PDF417 (registered trademark), UPC-A / E (Registered trademark), EAN-13 / 8 (registered trademark), CODE39 (registered trademark), CODABAR (registered trademark), Interleaved 2 of 5 (registered trademark), CODE128 (registered trademark), or the like may be used.

The camera device is not limited to the CCD camera 1 and may be configured using, for example, a CMOS image sensor.
Moreover, the kind of light source does not ask | require an illuminating device.

The flowchart which shows the content of the illumination time adjustment process which is the 1st Example at the time of applying this invention to the information code reading system for reading QR Code etc. and the control circuit of a decoder performs power-on. Flowchart showing the processing contents when the control circuit reads the QR code in the normal operation state (A) is a VD signal transmitted from the decoder to the CCD camera, (b) is a VI signal transmitted from the CCD camera to the decoder, and (c) is a timing chart showing illumination times changed in a plurality of stages. The figure which shows the constitution of the information code reading system The perspective view which shows the state which reads the QR code marked on the circuit board with CCD camera Functional block diagram schematically showing the electrical configuration of the decoder FIG. 2 equivalent diagram showing a second embodiment of the present invention. FIG. 2 equivalent view showing a third embodiment of the present invention.

Explanation of symbols

  In the drawings, 1 is a CCD camera (camera device) 2 is an LED illumination device, 3 is a decoder (information reading device), 5 is a QR code (information code), and 9 is a control circuit.

Claims (10)

A camera device that captures images in a fixed arrangement;
An illumination device for illuminating an imaging target of the camera device;
In an information code reading system configured with an information reading device that controls the camera device and the illumination device and decodes information based on image data of an information code read by the camera device,
The information reading device, when detecting a shutter time set in the camera device based on a control signal transmitted to and received from the camera device, determines a plurality of stages of illumination time with the shutter time as an upper limit, When the illumination device is illuminated at each illumination time, the information code read by the camera device is decoded, and the illumination time with the best reading state evaluated for each decoding result is read from then on. It is configured to preferentially set in the processing, and the time from when the imaging start signal is transmitted to the camera device until the reception of the image data output start signal output by the camera device is An information code reading system, wherein the information code is detected as a shutter time . When the information code has an error correction function,
2. The information code reading system according to claim 1, wherein the information reading device evaluates a reading state having a smaller number of error correction processes that occur during decoding as a good reading state. The information reading apparatus selects a plurality of illumination time candidates to be set in the subsequent reading process, and when reading performed by setting any one of these illumination times fails, the next highest priority illumination 3. The information code reading system according to claim 1, wherein the reading is retried by setting a time . As a result of executing the subsequent reading process, the information reading device preferentially sets an illumination time having a high success frequency when a high-read success frequency appears in addition to the preferentially set illumination time. 4. The information code reading system according to claim 3 , wherein the information code reading system is switched to . If the information reading device fails to read any of the plurality of selected illumination time candidates as a result of performing the subsequent reading process, the information reading device selects the selected illumination time from a plurality of stages with the shutter time as an upper limit. 5. The information code reading system according to claim 3, wherein reading is attempted by setting an outside illumination time . A camera device that performs imaging in a fixed arrangement, an illumination device that illuminates an imaging target of the camera device, the camera device and the illumination device, and image data of an information code read by the camera device In an information code reading system comprising an information reading device that decodes information based on the method, the information reading device determines a time for which the lighting device performs illumination,
The time from when the imaging start signal is transmitted to the camera device until the reception of the image data output start signal output by the camera device is detected as the shutter time set for the camera device,
A plurality of stages of illumination time is determined with the shutter time as an upper limit,
When the illumination device is illuminated at each illumination time, the information code read by the camera device is decoded respectively.
An illumination time determination method for an information reading apparatus, wherein the illumination time in which the reading state evaluated for each decoding result is the best is preferentially set in a subsequent reading process. When the information code has an error correction function,
7. The method of determining an illumination time for an information reading apparatus according to claim 6, wherein a reading state having a smaller number of error correction processes during decoding is evaluated as having a good reading state . Select multiple lighting time candidates to be set in the subsequent reading process,
8. If reading performed by setting any one of the illumination times fails, the reading is retried by setting the lighting time having the next highest priority. Method for determining the illumination time of the information reading apparatus. As a result of executing the subsequent reading process, when a high reading success frequency appears in addition to the preferentially set lighting time, the lighting time with the high success frequency is switched to be set preferentially. An illumination time determination method for an information reader according to claim 8. As a result of performing the subsequent reading process , if reading fails due to any of the selected lighting time candidates,
10. The illumination time determination method for an information reading apparatus according to claim 8, wherein reading is attempted by setting an illumination time outside the selection among a plurality of stages of illumination times with an upper limit of the shutter time .

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