JP2004145630A - Optical information reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a probability to succeed quickly in decoding by reducing as much as possible failure in decoding due to influence of a camera shake or changes in an external milieu. <P>SOLUTION: When instructed to take in an image by a trigger switch, a microprocessor calculates a taking-in condition (e period) of the image suitable when carrying out decoding by image data taken in after a lapse of a standby period by using image data captured by a taking-in means during standby period, and carries out decoding (f period) by the image data of the image captured after the lapse of the standby period, without performing decoding by the image data of the image captured from the point of time when this taking-in instruction being given to the lapse of the waiting period. Therefore, a percentage of successful decoding rises as compared with before, and a probability for decoding quickly and successfully can be improved. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical information reading device including a microprocessor that decodes an information code included in image data of an image in a detection area.
[0002]
[Prior art]
This type of optical information reading apparatus is configured to capture an image located in a detection area when a user gives an instruction to capture an image by, for example, a trigger switch. The captured image is stored in a memory as image data, and the content represented by the information code is obtained by decoding the information code included in the image data based on the image data stored in the memory. Is decoded and, for example, data is output to the outside.
[0003]
FIGS. 11A and 11B show an example of a conventional reading operation. In FIG. 11A, processes required for a reading operation are executed in synchronization with a frame signal. Hereinafter, only the main part of this processing will be described. That is, when a capture instruction is given, the detection area is irradiated with light and exposed, and captured as image data in the image data memory (b, d, c periods). Then, after calculating the next exposure condition (period e), the position of the information code included in the image data is detected and decoded (period f).
[0004]
At this time, as shown in FIG. 11A, when the decoding process is completed normally, the decrypted data is output to the outside (g period). However, as shown in FIG. If it is found that the decoding process cannot be performed normally (that is, failed) in the middle, it is found that the decoding process does not end normally, and then the detection area is irradiated with light again and exposed (the second time). (B, d periods), the information code included in the image data of the captured image is decoded (second f period), and the repetition processing is performed until the decoding processing is successful.
[0005]
[Problems to be solved by the invention]
However, when a trigger switch is operated, for example, a hand-held type camera shake may occur. Due to the occurrence of camera shake, the captured image is distorted, and the image data is in a state where decoding of the information code by the microprocessor is not possible, or even if decoding can be performed, much of the image data is subjected to correction processing. It is often taken as image data in a state requiring a long time.
[0006]
Therefore, if the normal series of reading processes is performed many times, the decoding process is performed based on the image data taken in the initial first time, as shown in FIG. The decoding process may be performed normally, or as shown in FIG. 11B, the decoding process may not be performed properly especially for the first (initial) image data. In general, the frequency of the processing shown in FIG. 11B is higher than the frequency of the processing shown in FIG. Further, the decoding process may be repeated three or more times. Such a decoding process failure may be caused not only by a camera shake but also by an influence of a change in an external environment (ambient brightness or the like) at the time of starting the capture.
[0007]
The present invention has been made in view of the above circumstances, and an object of the present invention is to improve the probability that decoding processing will succeed quickly by minimizing decoding processing failures due to the effects of camera shake and changes in the external environment. It is an object of the present invention to provide an optical information reading device capable of reading the information.
[0008]
[Means for Solving the Problems]
According to the first aspect of the present invention, when the user gives a capture instruction using the operation switch means, for example, the image data of the initially captured image (especially the first time) is affected by the effects of camera shake and changes in the external environment. In some cases, even if the microprocessor decodes the image code based on the captured image data, it is unlikely that the information code can be correctly decoded as shown in the conventional example, but the information code is not received until the waiting period elapses. Since decoding processing is not performed on the image data of the inserted image, the rate of successful decoding processing increases as compared with the related art. As a result, the probability that the decoding process succeeds quickly can be improved. Specifically, for example, the image data of the initial (especially the first or second) image captured by the capture unit by the microprocessor may be configured to wait for the standby period without performing the decoding process. . In addition, reading processing is performed in order to use image data of an image captured during the standby period to calculate image capturing conditions suitable for decoding image data after the standby period has elapsed. Even if the influence of camera shake or the change of the surrounding environment occurs each time, it is possible to set a capture condition adapted to this influence.
[0009]
In this case, if the camera shake or the external environment greatly affects the success of the decoding process, that is, if the decoding process does not succeed without repeating the decoding process many times, the time required for the decoding process is reduced. Can be shortened.
[0010]
As in the second aspect of the present invention, it is preferable that the capturing means is configured to capture the images during the waiting period after the capture instruction is given by the operation switch means. In this case, an image can be captured in a shorter time than the time required for normal capturing. In this case, a condition that the image data amount is set to one third of the image data amount to be normally taken and the acquisition time is set to one third of the time required for the normal acquisition. It is desirable to capture the image with.
[0011]
According to the fourth aspect of the present invention, even if the surrounding brightness changes abruptly each time a capture instruction is given to the capture means, the image data is based on at least the maximum luminance and the minimum luminance of the image data. Since at least one of the exposure condition (exposure time, illumination light amount) or the amplification factor of the amplifier circuit is set as the capture condition, it is possible to capture image data of an image adapted to a sudden change in brightness.
[0012]
According to the invention described in claim 5, whether or not the information code is present in the detection area is detected based on at least the maximum luminance and the minimum luminance of the image data. Then, it is possible to shift to the next processing without performing the decoding processing. Thus, when the information code does not exist in the detection area, the processing time can be reduced.
[0013]
According to the invention described in claim 6, when the microprocessor detects the presence of the information code in the detection region, the microprocessor performs the decoding process of the information code after roughly detecting the position in the detection region where the information code exists. The decoding process only needs to be performed for the roughly detected position, and the processing time can be reduced as compared with, for example, decoding the entire detection area.
[0014]
According to the seventh aspect of the present invention, if the microprocessor fails to decode the information code included in the image data of the second and subsequent images after the capture instruction is given by the operation switch means, Is used to calculate an image capture condition suitable for decoding the subsequent image data, so that the capture condition can be made closer to a condition that is optimal for the decoding process.
[0015]
According to the eighth aspect of the present invention, the microprocessor learns the number of times the decoding process has succeeded, and changes the number of times the image capturing is performed by the capturing unit when the operation switch unit is operated next time. Since the decoding process is performed on the image data of the image captured afterward, the number of times the image has been successfully decoded can be learned and reflected later.
[0016]
According to the ninth aspect of the present invention, since the microprocessor changes the number of times of image capturing within a range not exceeding the preset upper limit number, it is possible to prevent the processing from being prolonged indefinitely. .
[0017]
According to the tenth aspect of the present invention, the microprocessor learns the capture time at which the decoding process was successful, and waits until the image to be decoded is captured after the capture instruction is given by the next operation switch means. Is changed, the time at which the decoding process was successful can be learned and reflected later, even if camera shake or the influence of an external environment occurs. According to the eleventh aspect of the present invention, the microprocessor changes the waiting time until the image to be decoded is acquired within a range not exceeding the preset upper limit time. Therefore, it is possible to prevent the processing from being extended indefinitely without elapse of a predetermined time or more.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a first embodiment of an optical information reading apparatus applied to a barcode scanner according to the present invention will be described with reference to FIGS.
The bar code scanner 1 is also called a handy type bar code handy terminal, and reads a two-dimensional code (information code) such as a bar code or a QR code like a POS system such as a supermarket cash register. It is configured.
[0019]
In FIG. 1 schematically showing an electrical configuration of the barcode scanner 1, the barcode scanner 1 is mainly configured by a microprocessor 2. A battery 4 composed of a secondary battery or a primary battery is connected to the microprocessor 2 via a power supply circuit 3, and is driven by being supplied with power from the battery 4. The microprocessor 2 is connected to an irradiating unit 6 made of a red light-emitting diode via an illumination drive circuit 5, and the microprocessor 2 is connected to a trigger switch 7 functioning as an operation switch.
[0020]
When the user turns the reading port (not shown) of the barcode scanner 1 toward the detection area A and operates the trigger switch 7, the microprocessor 2 detects an operation signal of the trigger switch 7 and irradiates the microprocessor 2. Based on the instruction signal, light is uniformly emitted from the irradiation unit 6 toward the detection area A via the reading port. The illumination light amount at the time of this irradiation is configured to be controllable by the microprocessor 2.
[0021]
The light applied to the detection area A is reflected by the information code P located in the detection area A, is converged by the lens 8, and forms an image on the optical sensor 9. The optical sensor 9 comprises a CCD area sensor (two-dimensional sensor) having a shift register, and is connected to the microprocessor 2 via a sensor drive circuit 10. When the microprocessor 2 supplies an image exposure instruction signal to the optical sensor 9 via the sensor drive circuit 10, the optical sensor 9 exposes an image corresponding to one image area of the detection area A, and Then, the image signal is transmitted to the waveform shaping unit 12.
[0022]
The waveform shaping section 12 has an amplifier circuit 12a, and can control an amplification factor based on an amplification factor control signal from the microprocessor 2. The amplifying circuit 12 amplifies the sensor signal voltage of the image signal serially transferred from the optical sensor 9, and the waveform shaping unit 12 converts the data of one image area for each pixel. The level of the luminance signal is determined, binarized and binarized into binary data (image data) based on the level of the luminance signal and a predetermined threshold set in advance. ) Is digitized and stored in the memory 13, and the level of the luminance signal for one image area is digitized for each pixel and stored in the memory 13 as luminance data.
[0023]
The memory 13 has a storage area capable of storing at least image data of a plurality of images, and is sequentially stored for each image area. When the data cannot be secured, for example, the image data of the oldest image is sequentially overwritten. The microprocessor 2 is connected to the memory 13 and performs a decoding process based on the binarized data stored in the memory 13.
[0024]
In this way, when the image capture instruction is given from the trigger switch 7, the control circuit 11 captures an image for one image area of the detection area A, captures the binary data, and includes the binary data in the image data. The information code P to be decoded is decoded. Further, a display 14 and a data output unit 15 are connected to the microprocessor 2 so that the microprocessor 2 outputs a decoding result obtained by decoding the information code P. The decoding result decoded by the microprocessor 2 is stored in the memory 13. The microprocessor 2, the illumination driving circuit 5, the irradiating unit 6, the sensor driving circuit 8, the optical sensor 9, the waveform shaping unit 12, and the memory 13 function as a capturing unit 16, and when a capturing instruction is given, an image is given. It is designed to take in.
[0025]
The operation of the above configuration will be described with reference to FIGS.
FIG. 2 is a timing chart showing a series of processes until the decoding process succeeds in correspondence with a frame signal. The frame signal is generated by the microprocessor 2 when starting a predetermined process for one image. Although FIG. 2 shows a fixed cycle (for example, 33 milliseconds), it does not always have a fixed cycle.
[0026]
By the way, when the reading of the information code P is started, the user presses the trigger switch 7 with the reading port facing the detection area A. In this case, the microprocessor 2 generates a frame signal when detecting a press signal of the trigger switch 7. Then, the microprocessor 2 causes the excess charge accumulated in the optical sensor 9 to be discharged via the sensor drive circuit 8. This is the stable period of the optical sensor 9 (see FIG. 2: a: sensor stable period).
[0027]
When this process is completed, the microprocessor 2 generates a frame signal again and gives an irradiation instruction signal to the irradiation unit 6 via the illumination drive circuit 5, so that the irradiation unit 6 irradiates light to the detection area A. . Then, an image of the detection area A is formed by the optical sensor 9, exposed, and taken in (see FIG. 2: first bd period: exposure period and illumination lighting period). At this time, the image data of the first image is thinned out and taken in. The signal to be decimated is preset in the optical sensor 9 as two thirds of the normal image data. Specifically, FIG. 3 shows a schematic description. When a sensor drive signal is supplied from the sensor drive circuit 10 to the optical sensor 9, one image is exposed. In this case, image data of pixels in a substantially horizontal line from the upper part of the image (the upper part of FIG. The waveform is sent to the waveform shaping unit 12. Further, the optical sensor 9 thins out image data of pixels in two columns from the upper second column, and sends a signal of pixels in the next one column to the waveform shaping unit 12. In this manner, the process of sequentially thinning out two columns and sending the signal of the pixels for one column is repeated, and finally, the image for one image region is captured.
[0028]
At this time, the signal amount of the image sent to the waveform shaping unit 12 is one third of the normal amount. The amplification circuit 12a of the waveform shaping section 12 amplifies the image signal and takes it into the memory 13 as the above-described image data (FIG. 2: period c: image acquisition period). FIG. 3B and FIG. 3D schematically show images of image data taken into the memory 13. Normally, when fetching image data for one image area, image data including the entire information code P is stored in the memory 13 as shown in FIG. However, since the image taken in the first time is thinned out to one third of a normal image, information of two thirds of the image is lost as shown in FIG. However, it is possible to save the time for capturing an image by the amount of the thinned image, and the frame signal interval is narrowed as shown in FIG. This time (FIG. 4 (b)) is one third of the time (FIG. 4 (a)) for capturing the normal image. Thus, an image can be captured in a shorter time than the time required for normal capturing.
[0029]
Returning to FIG. 2, after that, the microprocessor 2 generates a frame signal again, irradiates light to the detection area A by the irradiation unit 6, and an image of the detection area A is exposed by the optical sensor 9. . The microprocessor 2 uses the image data captured during the standby period (FIG. 2: period a and the first period b, d, c) in parallel with the process of exposing the image of the detection area A. Then, the next image capture condition is calculated as capture condition data (FIG. 2: first e period: next capture condition calculation process period). Specifically, the microprocessor 2 searches the captured image data for a level at which the maximum value and the minimum value of the luminance signal are obtained, and compares the maximum value and the minimum value with a predetermined threshold value. To calculate the capture condition data. The capture condition data to be subjected to the calculation processing includes an amplification rate control signal for an amplification rate of the amplification circuit 12 a of the waveform shaping section 12, an exposure time instruction signal for an exposure time in the optical sensor 9, and illumination emitted from the illumination section 6. It is generated as a light amount irradiation instruction signal.
[0030]
That is, the microprocessor 2 creates an exposure condition setting signal for changing the exposure time (exposure time instruction signal) of the optical sensor 9 and the illumination light amount (irradiation instruction signal) of the irradiation unit 6 as the exposure condition, By creating an amplification factor control signal for changing the amplification factor of No. 12, the level of the luminance signal of the image data to be taken in next time is created as data for obtaining an image suitable for decoding processing.
[0031]
The image data value output as a result of the exposure by the optical sensor 9 is such that the closer the imaging target in the detection area A is to white, the greater the amount of received light and the higher the data value. The closer to black, the smaller the amount of received light and the lower the data value. As described above, in order to facilitate recognition of the information code, binarization is performed based on a predetermined threshold. For example, when the maximum luminance is lower than the predetermined threshold, the microprocessor 2 An amplification factor control signal for increasing the amplification factor is created, and an irradiation instruction signal for increasing the illumination light amount is created. It is sufficient that at least one of the exposure condition and the amplification factor can be changed.
[0032]
When the calculation of the capture conditions and the exposure for one image area are completed, the microprocessor 2 generates a frame signal and captures the image data for one image area into the memory 13 (second c period). When the microprocessor 2 captures the image data for one image area by the normal capturing procedure described above (see FIGS. 3C and 3D), the microprocessor 2 generates a frame signal again and exposes the optical sensor 7 to the frame signal. An exposure instruction signal including a time instruction signal is given to set an acquisition condition, and the optical sensor 7 is exposed (FIG. 2; third b period). That is, at the time of this exposure processing, the capture condition data calculated last time is reflected. The result of this exposure processing is taken into the memory 13, but is not taken into decoding because the microprocessor 2 does not take it. Further, while the optical sensor 7 continues the exposure processing, the microprocessor 2 calculates again the capturing condition data of the capturing condition for capturing the next image (FIG. 2; second e period). The capture condition data is calculated based on the image data acquired in the second period c, so that the capture condition can be further adapted to changes in the surrounding environment and use state of the barcode scanner 1. Become.
[0033]
When the calculation process of the capture condition data is completed, the microprocessor 2 captures the image data of one image area captured in the memory 13 and performs the decoding process (FIG. 2: period f). Specifically, first, the microprocessor 2 determines whether or not the information code P exists in the detection area A. As a method for detecting this presence, for example, the following method is used. That is, since the information code P is generally composed of white and black, the maximum luminance and the minimum luminance of the captured image are compared with those of a picture or the like in which black and white (bright and dark) is not clear. The difference is large. That is, the microprocessor 2 compares the maximum value and the minimum value of the level of the luminance signal in the captured one image data, and supposes that the difference is larger than a predetermined threshold value. Is detected in the detection area A. In order to detect whether or not the information code P exists in the detection area A in this manner, when the microprocessor 2 detects that the information code P does not exist in the detection area A, it should perform a decoding process. Instead, the process can be shifted to the next process (again, image data fetching process; not shown (refer to the conventional example)), and the processing time can be reduced.
[0034]
On the other hand, when the microprocessor 2 detects the presence of the information code P in the detection area A, it roughly detects the position of the information code P in the detection area A. Specifically, in the pixel data at the location where the information code P is located, unlike the location where the information code P is not located (such as a picture), black and white changes between adjacent pixel data in the captured image data. More points to be given.
[0035]
Therefore, for example, the microprocessor 2 divides the detection area A into a plurality of rectangular blocks, and converts the light points (white points) to dark points (black points) or the dark points to light points of the image data corresponding to the blocks. Is counted for each block of one image data, and it is detected which position (block) in the detection area A exists based on the counting result. Thus, the approximate position of the information code P in the detection area A can be detected. When the information code P does not exist in the detection area A, since the black and white is not clear, the counting result described above is small, and the picture or the like located in the detection area A may not be detected as the information code P. Few.
[0036]
Thereafter, the microprocessor 2 performs a decoding process. In this case, as described above, since the block in which the information code P exists is roughly detected, only the data of the detected block is cut out (code cutout processing), and the decoding processing is performed with only this part as a decoding target. . As a result, the decoding process can be performed quickly. The details of the decoding process are the same as those in the related art, and a description thereof will be omitted. When the decoding process is completed, the microprocessor 2 displays the result of the decoding process on the display 14 or outputs the result to the outside through the data output unit 15 (FIG. 2: g period: output processing period). During the decoding process, the exposure process for the detection area A is continuously performed as shown in FIG.
[0037]
According to the first embodiment described above, the microprocessor 2 stores the image data of the image affected by the camera shake captured from the time when the capture instruction is given by the trigger switch 7 until the standby period elapses. In this case, the decoding process is performed on the image data of the image captured by the capturing unit after the elapse of the standby period without performing the decoding process. Decoding processing is not performed on the image data in which decoding is likely to occur, and the ratio of successful decoding processing is increased as compared with the related art, so that the probability of successful decoding processing can be improved. In addition, a reading process is performed in order to use image data of an image captured during the standby period to calculate image capturing conditions suitable for decoding the image data after the standby period has elapsed. Even if the influence of camera shake or the change of the surrounding environment occurs each time, it is possible to set a capture condition adapted to this influence.
[0038]
In this case, if the camera shake or the external environment greatly affects the success of the decoding process, that is, if the decoding process does not succeed without repeating the decoding process many times, the time required for the decoding process is reduced. Can be shortened.
[0039]
After the capture instruction is given by the trigger switch 7, the image during the standby period is reduced to approximately one-third and captured, so that the time required for capture is shorter than the time required for normal capture by approximately one-third. Images can be captured.
[0040]
The maximum value and the minimum value of the luminance signal level in one image data are compared with a predetermined threshold value, and the exposure condition (exposure time, illumination light amount) or the amplification factor of the amplification circuit is determined as the image capture condition. Since at least one is set, image data of an image adapted to a sudden change in brightness can be quickly acquired.
[0041]
In order to detect that the information code P exists in the detection area A on the condition that the maximum value and the minimum value of the level of the luminance signal in one image data are compared and the difference exceeds a predetermined threshold value. If the information code P does not exist in the detection area A, the process can proceed to the next fetching process without performing the decoding process.
[0042]
(Second embodiment)
FIG. 5 shows a second embodiment of the present invention. The difference from the first embodiment is that the waiting period is extended. The same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. Hereinafter, only different parts will be described. FIG. 5 is a timing chart showing the operation until the decoding process succeeds.
[0043]
In FIG. 5, when a capture instruction is given by the user operating the trigger switch 7, a sensor stabilization period, an exposure period (illumination lighting period), an image acquisition period, a second exposure period and an illumination lighting period, and a next capture period are performed. Each process is executed in the condition calculation processing period and the second image acquisition period (see the description of the first embodiment and FIG. 5). This period corresponds to the standby period in the present invention. In the first next acquisition condition calculation processing period (period e), the microprocessor 2 uses the image data acquired in the first image acquisition period to acquire the image after the elapse of the standby period. Calculate the condition. That is, even if the image data captured during the first image acquisition period is affected by camera shake or a change in the external environment, a capture condition adapted to the influence is calculated. Thereafter, the capture condition calculated in this manner is set before the third exposure period (second capture condition calculation period), and the image is exposed again under the set capture condition. Thereafter, image data of the image is acquired in a third image acquisition period.
[0044]
Then, the microprocessor 2 calculates the next capture condition (third time) and performs decoding processing on the image data captured in the third image acquisition period. If the decoding process is completed normally, the result is output to the outside.
[0045]
According to the second embodiment, substantially the same operation and effect as those of the first embodiment can be obtained, and even if there is an influence of a camera shake or an external environment during the standby period, the system can adapt to the environment. Since the decoded image data is taken in, the decoding process by the microprocessor 2 is more likely to succeed.
[0046]
(Third embodiment)
FIGS. 6 to 9 show a third embodiment of the present invention. The difference from the first embodiment is that the microprocessor learns the standby time of the image that has been successfully decoded, and then switches the next trigger switch. 7, the standby time until the image to be decoded is acquired after the acquisition instruction is issued.
In FIG. 6, which shows the entire flow of reading the information code P in a flowchart, the microprocessor 2 sets a variable T2 to 0 for the first time. This variable T2 indicates 0 hour at the time of the first reading, and indicates a standby time generated by repeating the reading operation from the second time on, and indicates the variable T2 during the sensor stabilization period (this period is substantially constant). Adding the time represents the waiting period in the present invention. See the timing chart shown in FIG.
[0047]
Further, the selection flag for selecting the variable T2 is set to "flag 1" (step S1). This selection flag is a flag provided to change the variable T2 for each reading, and each time reading is completed, “flag 1” → “flag 2” → “flag 1” → “flag 2” →. (See steps T6 to T10 in FIG. 7: described later).
[0048]
In the first reading process, when a trigger instruction is given by the trigger switch 7 (step S2), after the sensor stabilization period, the measurement of the times T1 and T3 is started using the timer interrupt function built in the microprocessor 2. (Steps S3 and S4). Thereafter, at the time of the first reading process, the process is repeated as in the conventional case. In this case, the microprocessor 2 captures an image (step S5) and calculates the next capturing condition (step S6; see (1) in FIG. 8).
[0049]
If the timer time T1 is equal to or greater than the variable T2 (step S7: YES), the microprocessor 2 decodes the captured image data. That is, if the standby time has elapsed, the microprocessor 2 performs the decoding process (step S9). If the standby time has not elapsed in step S7 (step S7: NO), the microprocessor 2 sets the time of the timer T3. Is cleared, and the process returns to step S4 to capture an image.
[0050]
Since the variable T2 is 0 the first time the barcode scanner 1 is used for the first time, the process proceeds to step S9. If the decoding process has failed in step S9 ((2) in FIG. 8), the variable T3 is cleared (step S8), the process returns to step S4, the timer T3 starts measuring again, and the image is captured. In step S9, the decoding process is repeated. In this case, if the decoding process is successful ((3) in FIG. 8), the microprocessor 2 ends the measurement of the timers T1 and T3 (steps S11 and S12), and outputs the decoding process result to the outside (step S13). ; See (4) in FIG. 8). That is, the timer T1 is a time from immediately after the acquisition instruction is issued to the time when the decoding process succeeds, and the timer T3 is required for one acquisition time when the decoding process succeeds, and the next condition calculation and the decoding process. This is the total time, and these times are measured. Then, the microprocessor 2 calculates a variable T2 at the time of reading the information code P next time (step S14), and performs learning and preparations for the next time a trigger instruction is given by the trigger switch 7.
[0051]
FIG. 7 shows a process for calculating the variable T2.
First, the microprocessor 2 determines whether or not the timer time T1 for which the measurement has been completed in step S11 is equal to or less than a predetermined limit value (upper limit time: for example, 1 second) (step T1). If there is (Step T1: NO), the limit value is substituted for the variable T1 (Step T2). This process represents a process for setting an upper limit on the time from when the trigger switch 7 is pressed to when the decoding process is performed, thereby preventing the process from being prolonged without limit. Then, the microprocessor 2 increments the number of times of reading (step T3), and stores the variable T1 in the memory 13. Then, a first average value T1average of the variable T1 is calculated (step T4). The first average value T1average is calculated based on the number of readings up to this time and the value of the variable T1 stored in the memory 13. Then, the microprocessor 2 subtracts the value of the timer time T3 measured and completed in step S12 from the calculated first average value T1average, and calculates a second average value T1average2 (step T5). Here, if the T2 selection flag is “flag 1” (step T6: YES), the microprocessor 2 substitutes the second average value T1average2 for the variable T2 (step T7) and sets “flag2” as the T2 selection flag. (Step T8), and the process ends.
[0052]
If the T2 selection flag is "flag 2" in step T6, the first average value T1average is substituted for the variable T2, and the flag is changed to "flag 1" as the T2 selection flag (step T10). At the end of the first reading process, the variable T2 is set to the second average value T1average2, and the T2 selection flag is set to “flag 2”. When the calculation processing of the variable T2 is performed in this manner (see (5) in FIG. 8), the process returns to step S2 of the reading processing and the processing is performed again.
[0053]
<Second reading process>
When an instruction to capture an image is given by the trigger switch 7 for the second time, the reading process is performed again. In this case, after the second reading, setting processing of a standby time until decoding processing is performed using the sensor stabilization period is performed (see (6) in FIG. 9). This standby time setting process is performed based on the setting of the variable T2. For example, assuming that the time is set as shown in FIG. 9, in step S7, until the time indicated by T2 elapses. Then, the next capturing condition is calculated and set based on the image capturing process and the captured image. During this time, the decoding process is not performed, and the calculation and setting of the capture condition are performed.
[0054]
For example, even if the image captured at the first capture (see {circle around (7)} in FIG. 9) is affected by camera shake or the external environment, the effect of camera shake or the external environment is not The microprocessor 2 calculates the next fetching condition in the standby state during the standby time (including the standby period) (see (8) in FIG. 9). The next capture condition is calculated during the standby period, and after the standby period has elapsed, the microprocessor 2 captures an image again in step S5 (see (9) in FIG. 9).
[0055]
At this time, the image of the detection area A is exposed by the optical sensor 9, and in parallel with the process of exposing the image of the detection area A, the microprocessor 2 uses the previously captured image data. Then, the next image capture condition is calculated as capture condition data. Since the next capture condition is calculated again based on the image captured at the time of the second capture, even if the influence of camera shake or the influence of the external environment continues after the first capture, decoding is performed. The capture condition with reduced influence is calculated again without performing the processing, and if the capture condition is set and loaded into the microprocessor 2, the influence can be eliminated as much as possible.
[0056]
In step S5, when the image capturing is completed, the microprocessor 2 calculates the next capturing condition again. If the time T1 of the timer is equal to or longer than T2 in step S7, the decoding process is performed in the same manner as in the above-described embodiment. If the decoding process is successful, the timers T1 and T3 are stopped, and the processing result is output to calculate T2. . These series of processes are repeated.
[0057]
According to the third embodiment, the operation and effect of the first embodiment are substantially the same as those of the first embodiment, and the microprocessor 2 learns the standby time in which the decoding process has been successfully performed. In order to change the waiting time before capturing the image to be decoded after the capture instruction is issued, even if camera shake or the influence of the external environment occurs, the standby time of the image can be learned and reflected later. it can.
[0058]
Since the microprocessor 2 changes the standby time within a range not exceeding the upper limit time, the predetermined time does not elapse before the start of image capture, and the processing can be prevented from being infinitely prolonged.
[0059]
(Fourth embodiment)
FIG. 10 shows a fourth embodiment of the present invention. The difference from the third embodiment is that the illumination is not turned on during the standby time, and the calculation of the next capturing condition is also performed. There is no place.
FIG. 10 shows a timing chart corresponding to FIG. 9 described in the third embodiment. In the set time T2, the image is exposed and captured without turning on the illumination. In addition to the substantially same operation and effect as the embodiment, the illumination is not turned on, so that the power consumption can be reduced during the standby time.
[0060]
(Other embodiments)
The present invention is not limited to the embodiment described above and shown in the drawings, and the following modifications or extensions are possible.
When the microprocessor 2 decodes the information code P included in the image data of the second and subsequent images after the capture instruction is given by the trigger switch 7 and fails, the subsequent image is used by using the image data. An arrangement may be made to calculate image capture conditions suitable for decoding with data. In this case, the capturing condition can be made closer to the condition that is optimal for the decoding process.
[0061]
In the above-described first embodiment, an embodiment is described in which the capture condition is calculated for the first time (period e) and the calculated result is not reflected in the image data to be subjected to the decoding process (period f). You may comprise so that it may be reflected on a decoding process result. That is, in FIG. 2, before the microprocessor 2 captures image data (exposure, image acquisition) of the second image, the microprocessor 2 calculates capture conditions, immediately sets the capture conditions, and then converts the image data. You may comprise so that it may take in and decode. The same applies to the second or third embodiment. In the flowchart shown in FIG. 6 of the third embodiment, this processing can be realized by exchanging the processing of step S5 and the processing of step S6.
[0062]
In the above-described embodiment, the capturing unit 16 includes the microprocessor 2, the illumination driving circuit 5, the irradiation unit 6, the sensor driving circuit 8, the optical sensor 9, the waveform shaping unit 12, and the memory 13. It is sufficient that the configuration is such that an image can be captured. If necessary, some of these components may be deleted.
[0063]
In the third or fourth embodiment, the embodiment in which the capture time is learned and the standby time until the capture of the image to be decoded after the trigger switch 7 is operated next time is changed has been described. Instead of the time and the standby time, the set unit is the number of times of image capture (the number of times the bcd process (range T2) in FIG. 9 is performed or the number of times the b process (range T2) in FIG. 10 is performed). It is good. In this case, it is possible to learn the number of captures of an image that has been successfully decoded and reflect the number of captures until a subsequent image is captured. Further, it is desirable to set an upper limit on the number of times of taking. In this case, the image is not taken in more than the upper limit number of times, and the processing can be prevented from being infinitely prolonged.
[0064]
The optical sensor 9 may be a two-dimensional sensor such as a line sensor (one-dimensional sensor) or a CMOS image sensor.
The two-dimensional code is not limited to the QR code, and may be, for example, PDF417, DataMatrix, or MaxiCode.
[Brief description of the drawings]
FIG. 1 is an electrical configuration diagram of an optical information reading apparatus according to a first embodiment of the present invention.
FIG. 2 is a timing chart showing a processing flow;
FIG. 3 is a diagram schematically showing an image capture image ((a) and (b) show the case of thinning out, (c) and (d) show the case of normal capture)
FIG. 4 is a diagram showing a comparison of frame signal intervals.
FIG. 5 is a view corresponding to FIG. 2, showing a second embodiment of the present invention;
FIG. 6 is a flowchart of a reading process according to a third embodiment of the present invention.
FIG. 7 is a flowchart illustrating processing for calculating a variable T2.
FIG. 8 is a diagram corresponding to FIG. 2 (part 1);
FIG. 9 is a diagram corresponding to FIG. 2 (part 2);
FIG. 10 is a view corresponding to FIG. 2, showing a fourth embodiment of the present invention;
FIGS. 11A and 11B show a conventional example and are equivalent to FIGS.
[Explanation of symbols]
1 is a bar code scanner (optical information reading device), 2 is a microprocessor, 6 is an irradiation unit, 7 is a trigger switch (operation switch means), 9 is an optical sensor, 12 is a waveform shaping unit, 12a is an amplification circuit, Reference numeral 16 denotes a capturing unit, A denotes a detection area, and P denotes an information code.

Claims (11)

Operation switch means for instructing image capture;
Capturing means for capturing an image of the detection area when an image capturing instruction is given;
An information code included in the image data of the image of the detection area captured by the capturing unit is decoded. If the decoding process fails, a capturing instruction is given to the capturing unit to convert the image data. An optical information reading device comprising: a microprocessor that repeats a decoding process by taking in;
The microprocessor does not perform decoding processing on the image data of the image captured until the standby period elapses after the capture instruction is given by the operation switch means. An optical information reading apparatus configured to use image data for calculating image capturing conditions suitable for decoding image data captured after a standby period has elapsed. The optical information reading device according to claim 1,
An engineering information reading apparatus according to claim 1, wherein said capturing means thins out and captures the images during the standby period. The optical information reading device according to claim 2,
The capturing means is configured to set the image data amount to be thinned out to be approximately one-third of the image data amount to be normally captured, and to set the time to thin out and capture to approximately one-third of the normal image capturing time. An optical information reading apparatus for capturing an image. The optical information reading device according to any one of claims 1 to 3,
The microprocessor, as a pre-process of the decoding process, based on at least a maximum luminance and a minimum luminance of the image data of the image captured by the capturing unit, an exposure condition when the capturing unit captures an image. Alternatively, at least one of the amplification factors of an amplifier circuit for amplifying a signal when the capturing unit captures an image is calculated as the capturing condition. The optical information reading device according to any one of claims 1 to 4,
The microprocessor detects whether an information code exists in a detection area based on at least a maximum luminance and a minimum luminance of image data of an image captured by the capturing unit, as a pre-process of the decoding process. An optical information reading device, comprising: The optical information reading device according to claim 5,
When the microprocessor detects the presence of the information code in the detection area, the microprocessor is configured to roughly detect a position in the detection area where the information code exists, and then perform a decoding process. Information reader. The optical information reading device according to any one of claims 1 to 6,
The microprocessor decodes the information code included in the image data of the second and subsequent images after the capture instruction is given by the operation switch means and, when the decoding fails, uses the image data to perform the subsequent image processing. An optical information reading device configured to calculate an image capturing condition suitable for performing decoding processing on data. The optical information reading device according to any one of claims 1 to 7,
The microprocessor learns the number of times of image capture by the capture unit that succeeds in the decoding process, and changes the number of captures until the next time the image is captured after the capture instruction is given by the operation switch unit. An optical information reading apparatus configured to decode an information code included in image data of an image captured after the image of the capture number is captured. The optical information reading device according to claim 8,
The optical information reading device according to claim 1, wherein the microprocessor changes the number of times of image capture within a range not exceeding a preset upper limit number. The optical information reading device according to any one of claims 1 to 7,
The microprocessor is configured to learn a capture time in which decoding processing is successful, and to change a standby time until a capture of an image to be decoded after the capture instruction is given by the operation switch means next time. An optical information reading device, comprising: The optical information reading device according to claim 10,
The optical information reading device according to claim 1, wherein the microprocessor changes a standby time until an image to be decoded is taken within a range not exceeding a preset upper limit time.

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