JP5007388B2 - Medium surface detection program and medium surface detection method applied to code reader - Google Patents

Description

  The present invention relates to a program and a method for causing a computer to function as a means for automatically detecting a medium surface entering an imaging area of an imaging means, and more particularly to a barcode or QR code (registered trademark) written on the medium surface. The present invention relates to a medium surface detection program and a medium surface detection method applied to an apparatus having a code reading function such as the above.

  Conventionally, in order to recognize management information of products and parts in a short time, one-dimensional or two-dimensional codes in which product and part numbers, product names, prices and other information are symbolized with black and white stripes are widely used. It has been. A code such as a one-dimensional code or a two-dimensional code (also referred to as a “label” or “symbol”) represented by a code formed by the difference between these different reflectances, specular reflection, and diffused light is, for example, a one-dimensional code. A series of numbers is represented by a combination of line width ratios, and various types of information such as product and part numbers are replaced with the above numbers. Such a code reader that optically reads a one-dimensional code composed of a one-dimensional bar or a secondary code composed of a two-dimensional cell is a hand-held type (handheld type) that an operator uses while holding the device. Type) (see, for example, Patent Document 1), and a stationary type (also referred to as a stationary type) fixed at a predetermined position on the conveyance path (see, for example, Patent Document 2).

  Hand-held code readers are widely used at supermarkets and department stores as a POS (point-of-sale information management) system, for example, and are also used in the manufacturing and distribution stages.

  On the other hand, stationary code readers are used in distribution distribution centers and the like. For example, in a distribution center, an article with a random destination and type is conveyed by a conveying means such as a belt conveyor, and information on a label attached to the surface of the conveyed article is imaged by an imaging means. A code is read by processing an image, and various articles are automatically sorted by a sorting device based on the information. In recent years, mobile phones having a QR code (registered trademark) reading function have also been realized.

JP 2001-52105 A JP 2005-148786 A

  Conventional hand-held type code readers are set so that when a person reads a code with his / her hand, he / she triggers himself by operating a reading switch, etc., or always performs a reading operation in continuous reading mode. The method of reading is taken. In the former, it is necessary to place a code or a code reader at a position where it can be read by itself and repeat the operation of triggering until the reading is completed. The latter always performs a reading operation in the continuous reading mode. Therefore, even when reading is not performed, unnecessary operations such as a mode switching operation and illumination control are performed for reading. In addition, in a portable information processing apparatus for personal use such as a mobile phone having a code reading function, it is necessary to operate by capturing a code while viewing an image on a display unit. Therefore, any of the code reading devices is not easy to operate, and it is difficult to perform the reading operation efficiently.

  The present invention has been made in the circumstances as described above, and an object of the present invention is to provide a code reading apparatus capable of improving operability when reading a code and improving the efficiency of code reading work at low cost. It is to provide a medium surface detection program and a medium surface detection method applied to

The present invention relates to a medium surface detection program and a medium surface detection method applied to a code reader. The above object of the present invention relates to an image capturing unit that captures an image and the image capturing unit with respect to the medium surface detection program. A medium surface detection program that is applied to a code reading device that includes a code reading unit that processes an image captured by the image processing unit and reads a code written on the medium surface, wherein the code reading device reads the code. An image capturing unit that operates the imaging unit during standby to periodically capture an image within the imaging range, and a predetermined number of blocks in an image area at the center of the image captured by the image capturing unit divided, as one or more specific blocks only monitoring block of the divided blocks, the image between the corresponding monitoring blocks before and after the image in which the regularly scheduled preparative written Compared minute while monitoring the variation of the image components in the monitoring block, the image changes to a monitoring means for monitoring the position of each block of the monitoring blocks, the variation of the image component during the reading stand of the code Based on detection information and position information from the monitoring means, an entry detection means for detecting that the medium surface is present in the center of the imaging range of the imaging means, and the medium surface is present in the center This is accomplished by functioning as a trigger command output means for outputting a trigger command for starting the code reading operation when it is detected.

Further, the entry detection means compares the image components between the monitoring blocks for each block corresponding to the same block position, and the change state of the image component of at least one block changes from no change to a change state. In addition, when it is determined that the state of change in the image component of each block corresponding to the same block position is the same in all blocks, the medium surface is present at the center in the imaging range of the imaging unit. And the trigger command output means outputs a trigger command for starting the code reading operation when it is detected that the medium surface is stationary at the central portion. , if the elapsed time from the start of the reading operation of the previous SL code had elapsed set timeout period as the leaving determination time of the medium surface, the medium surface is the imaging range Thereby detecting the pressurizing et al are away de, as the leaving detection means for transitioning to a wait state read for the next code, the code reading device to be further feature, the variation of the image components, between the monitoring block The standard deviation of the luminance value or the amount of change in the average luminance value, the image capturing means changes the gain of the video signal and the shutter speed to a plurality of patterns when capturing the image, and The image capturing is performed, and the monitoring unit is more effectively achieved by monitoring the amount of change of the image component in each pattern when comparing the image components between the monitoring blocks.

Further, the monitoring means, when setting the monitoring block, varies at least one element of the image range to be divided, the shape and size of the block, and the number of divisions, The means varies the element in accordance with the operation mode of the code reading device, and the entry detection means determines the number of blocks in which the amount of change in the image component is outside the threshold range in the medium surface detection. Detecting entry of the medium surface as an element, and when the code reading means has a function of decoding the code, the separation detecting means sets the timeout time according to the decoding status of the code, the detection The medium surface to be subjected to the printing includes the surface of the print medium, the image display medium, and the medium on which the code is directly marked. It is made.

In addition, regarding a medium surface detection method, a medium in a code reading device including an image pickup unit that picks up an image and a code reading unit that processes an image picked up by the image pickup unit and reads a code written on the medium surface A method for detecting a surface, the step of operating the image pickup means at the time of waiting for reading the code to periodically take an image in the image pickup range, and an image of a central portion of the image taken by the image capture means The area is divided into a predetermined number of blocks, and only one or more specific blocks among the divided blocks are set as monitoring blocks, and image components between corresponding monitoring blocks are compared in the images before and after the periodic capture. and monitors the change amount of the image components in the monitoring block, the steps of monitoring the position of each block of the monitoring blocks image change, reading of the code waiting Sometimes the detection to the said code reading operation simultaneously be present in the central portion of the imaging range of the medium surface is the image pickup means on the basis of the position information from the change amount of the detected information and said monitoring means of said image component And detecting the separation of the medium surface from the imaging range based on the information on the change amount of the image component and the elapsed time from the start time of the code reading operation, and for the next code Transitioning to a read standby state.

  According to the present invention, the image captured during the code reading standby time is processed to automatically detect the medium surface and automatically start the code reading operation. It is possible to automatically detect the surface of the medium and read the code without providing a medium detection sensor. Therefore, there are excellent effects such as improvement in operability when reading a code and improvement in the efficiency of code reading work at a low cost.

  The present invention can be applied not only to a hand-held type code reader, but in the following embodiments, a case where the present invention is applied to a hand-held type and a hand-held type code reader will be described as an example. The “medium surface” as used in the present invention is not limited to the surface of the print medium on which the code is printed, the display surface of an image display medium such as a display on which the code is displayed, the product with the code label attached, etc. This refers to the surfaces (including curved surfaces) of all objects on which codes are written, such as the surfaces of objects. The “code” referred to in the present invention is a code in which predetermined information is encoded, and is a general one-dimensional code or two-dimensional code (QR code (registered trademark)) encoded in a pattern such as black and white. And various codes including marks directly formed on the surface of an object such as metal, ceramics, or a polymer compound (for example, an object surface such as a semiconductor wafer or an engine block). Further, symbols such as seals and fingerprints may be read.

  FIGS. 1A and 1B are external views showing an example of a code reading device having a medium surface detection function according to the present invention, and FIG. 1A is an example in the case of being used as a handheld code reading device. FIG. 1B shows an example in the case of using as a stationary code reader. A code reading device 10 of this example is a portable information processing device having an image reading function of a code 2 (for example, a code printed on a label attached to a product) written on a medium surface 1, and a POS register device. It is preferably used in stores equipped with

  When the code reading device 10 is used as a hand-held device, the user holds the code reading device 10 by hand and, as shown in FIG. 1A, the reading surface 10a (the image pickup surface of the image pickup means) has a medium surface. Bring 1 closer. By this operation, the entry of the medium surface 1 into the imaging range is automatically detected without operating the reading switch 10b or the like, and the image of the code 2 on the medium surface 1 is read to decode the code 2. Is executed. Further, when the medium surface 1 comes out of the imaging range, it automatically enters a standby state. Note that the “imaging range” in the present invention refers to a three-dimensional imaging range (an imaging range in which a code can be decoded) in which no blur is generated.

  On the other hand, when used as a stationary code reader, the code reader 10 is mounted on the support 10c as shown in FIG. The support base 10c is a support base that is tiltably and pivotally supported around a fulcrum, and images within a predetermined distance and angle of view range from the position of the imaging means of the code reader 10 installed on the support base 10c. It becomes a range. When the medium surface 1 approaches, the image of the code 2 on the medium surface 1 is automatically read and the code 2 is decoded as in the case of the hand-held type. Then, when the medium surface 1 is extracted from the imaging range, it automatically enters a standby state. In addition, by appropriately inserting / removing the next medium into / from the imaging range of the code reader 10, the codes attached to the plurality of medium surfaces 1 can be continuously read without operating the reading switch 10b or the like. Can do. For example, in a POS system, for a label 1 to be attached to a product, a code 2 (information indicating the price of the product) printed on each label 1 is appropriately read by a code reading device 10, and the decoded data of the code 2 is read. The price information of each product can be registered in the database by transmitting it to the computer of the POS system.

  As described above, the code reading device 10 according to the present invention does not operate the reading switch 10b (or input a command from the operation unit or the host system) in any use form, and also includes an entry detection sensor and a detachment. The reading operation of the code 2 on the medium surface 1 is automatically started / finished without providing hardware such as a detection sensor.

  Next, the configuration of the code reading device 10 will be described.

  FIG. 2 is a block diagram illustrating a configuration example of the code reading device according to the present invention. The code reading device 10 processes an image captured by the imaging unit 11 and an imaging unit 11 that captures an image of a subject. Code reading means 12 (hereinafter referred to as “code decoding means”) having a function of reading an image of the code 2 written on the medium surface 1 and decoding (decoding) the encoded information; On the other hand, the illuminating means 13 for emitting illumination light, the medium surface detecting means 14 for detecting the entry of the medium surface 1 into the imaging range of the imaging means 11 and the detachment of the medium surface 1 from the imaging range, and each means 11 And control means 15 for controlling the operation of the entire apparatus including -14.

  In this example, the image pickup means 11 is a means for picking up an image in an area including the code 2 using the code 2 written on the medium surface 1 as a subject. As the image pickup device, a monochrome or color image is used. An image pickup device including an image pickup element and a lens for picking up an image, for example, a CCD type or CMOS type image pickup camera, or a line sensor in which color image elements are arranged in a straight line is used.

  The code decoding means 12 is configured by software (computer program and decoding data) or hardware, and processes the image data of the code 2 to decode the code information. The code decoding unit 12 may be a unit that only reads the image of the code 2, but in the present embodiment, the code decoding unit 12 will be described as having a code decoding function.

  The illumination means 13 is a means (additional component) for irradiating the light from the light source to the cord 2, and is composed of an LED (light emitting diode) array or the like, for example, a cord used in a dark environment. It is mounted on a reader or a portable code reader used in various places.

  The medium surface detecting means 14 is means for realizing the code reader having the medium surface detecting function according to the present invention. In the present embodiment, software (program for causing the computer to realize the medium surface detecting function) , Control data, etc.). In the present invention, when detecting the entry of the medium surface 1 into the imaging range of the imaging unit 11 and the departure from the imaging range, the medium surface detection is performed without using hardware such as an entry detection sensor or a separation detection sensor. The entry / exit is automatically detected by the means 14 to control the start / end of the code reading operation. In addition, the apparatus having the illumination unit 13 has a function of controlling lighting / extinction of the illumination unit 13, the amount of light, and the like according to the ambient light amount detected based on image data captured during the reading standby.

  A functional configuration and an operation example of the medium surface detection unit 14 will be described later with a specific example.

  The control means 15 includes a CPU 15a for controlling each means, a memory 15b, an input / output interface, and the like. Other means include communication means for transmitting data to and from the host system 20 via a communication cable or a wireless communication network, code decoding data (or raw image data) in a memory, a PC card, Data storage means for storing and recording in a transferable storage medium such as a flash memory is mounted.

  Next, functions of the medium surface detection unit 14 will be described. Hereinafter, the “function” of the medium surface detection means 14 will be referred to as “means”.

  FIG. 3 is a functional block diagram illustrating an example of the configuration of the medium surface detection unit 14. The medium surface detection unit 14 operates the image pickup unit 11 during reading standby and periodically captures an image within the image pickup range. The capturing means 14a and the monitoring means for monitoring the amount of change of the image component in the image area during the standby for reading by comparing the image components of the images before and after being captured in time series from the image capturing means 14a. 14b, an entry detection means 14c for comparing the amount of change in the image component (for example, luminance value) and a threshold value to detect entry into the imaging range of the medium surface 1, and reading of the code when entry is detected The trigger command output means 14d for outputting a trigger command (reading start command) for starting the operation, and after the entry is detected, the amount of change of the image component is compared with the threshold value, and from within the imaging range of the medium surface 1 Detecting the withdrawal of And a separation detection means 14e for transitioning to a read standby state for over de.

  The monitoring by the monitoring unit 14b is performed by dividing an image within the image area captured by the image capturing unit 14a or an image within a specific range into a predetermined number of blocks and dividing one or more specific blocks (for example, the image area into n It is preferable that the amount of change in the image component in the monitoring block is monitored by using the monitoring block as an annular block on the outer peripheral edge side in the block group divided into pieces. Hereinafter, the case of processing in this monitoring mode will be described as an example.

  The means 14a to 14e are functionally classified by assigning means names to the constituent elements in order to show the functional configuration of the medium surface detecting means 14 according to the present invention for convenience of explanation, and the software configuration It does not limit etc.

  The outline of the medium surface detection processing according to the present invention having the above-described configuration will be described with reference to the flowcharts of FIGS.

  First, the medium surface detection unit 14 periodically captures an image within the imaging range by operating the imaging unit 11 during the code reading standby by the image capturing unit 14a (step S1).

  In the medium surface detection process (step S2), the monitoring unit 14b divides the image area of the image captured in step S1 into fixed blocks (step S2a in FIG. 5), and specifies one or more specified blocks. Using the block as a monitoring block, the change in the image component between the corresponding monitoring blocks is monitored in the images before and after being periodically captured in step S1.

  FIGS. 6A to 6D show examples of monitoring blocks, and the shaded block 3 in the divided block indicates the monitoring block. 6A shows an example in which all nine divided blocks are used as monitoring blocks, FIG. 6B shows an example in which only the central block is used as a monitoring block, and FIG. 6C shows monitoring blocks in the surrounding blocks. FIG. 6D shows an example in which four corners are monitored blocks.

  The monitoring block may be fixed or variable. For example, the block shape, size, number of divisions, block position and orientation in the divided area of the captured image (at least one of them), for example, the operation mode of the code reader (reading standby mode) , A reading operation mode, an entry detection mode, a separation detection mode, etc.), an angle of view of an imaging unit, and an entry direction of a medium detected by image processing.

  The monitoring unit 14b obtains an image component (for example, standard deviation, average luminance) for each monitoring block as described above, and monitors a change in the image component (step S2b). Then, for example, using the number of blocks having a change in the image component as a determination element, it is determined whether or not the number of blocks in which the change in the image component has been detected is equal to or greater than the specified number of blocks (determination reference value for medium surface detection) ( In step S2c), if there is less than the specified number of blocks, “no change” is determined (step S2d), and if there is a change beyond the specified number of blocks, it is determined that “changed” (step S2e).

  The medium surface detection means 14 (entrance detection means 14c) determines that the medium surface 1 has entered the imaging range if the determination result at the time of standby is “changed”, and automatically enters from the entry detection means 14c. A trigger command (code reading operation start command) is sent to start the code 2 reading operation. For example, as shown in the schematic diagram of FIG. 7A, the monitoring block B1 (i) of the previous captured image in time series (in this example, 9 blocks obtained by dividing the captured image into 9 are monitoring blocks. , I = 1 to 9) and the subsequent captured image monitoring block B2 (i), and if there is no change in the image component, the reading operation is not started and the standby state is maintained. Also, as shown in FIG. 7B, if there is a change in the number of designated blocks (for example, 3 blocks) or more in the monitoring block, the determination result of “with change” is received from the monitoring means 14b and it is determined that the entry is detected, The code 2 reading operation is started (step S3).

  The medium surface detection unit 14 continues the medium surface detection process even during the code 2 reading operation by the code decoding unit 12 (steps S4 to S6). Then, in the separation detection unit 14e, as shown in FIG. 7C, if it is determined that a state in which there is no change in the image in the monitoring block has passed a certain time (exceeded a timeout time described later), the medium surface 1 Is separated from the imaging range (step S7), the reading operation of the code 2 is stopped, and the reading standby state is entered again.

  By repeating the above operation, it is possible to automatically detect the medium surface and read the code without operating the reading switch or providing a medium entry detection sensor. In addition, in the continuous reading mode or the like, it is possible to automatically read a plurality of codes without switching the reading operation mode.

Next, an operation example of the code reading apparatus to which the present invention is applied and details of the medium surface detection process will be described along the flow of the flowchart of FIG.
<Image capture processing during reading standby>
First, the image capturing means 14a periodically captures an image (image for medium surface detection) within the imaging range by operating the image capturing means 11 during the code reading standby. At that time, images within the imaging range are periodically taken as the same setting without changing certain conditions, for example, the gain of the video signal, the shutter speed, and the internal illumination, and are stored in the storage means in time series. The images to be captured here may be all images within the imaging range, but in the present embodiment, images within a specific range smaller than the image region (for example, an area having a vertical and horizontal half (area ratio is 1/4)) Image) (step S11).

  In the case of a device having the illumination means 13, the illumination is not turned on when there is a certain amount of ambient light, and is turned on when it is dark. In this illumination control, the medium surface detecting means 14 detects the amount of ambient light based on the image data captured during reading standby, and performs lighting control or the like according to the light quantity when the code decoding means 12 reads the code. In the preferred embodiment, in step S11, when images are taken in regularly, for example, the gain of the video signal is set so as to correspond to a certain range of illuminance without the internal illumination by the illumination means 13. And a plurality of shutter speed settings (for example, three patterns of setting A, setting B, and setting C), and when capturing an image, setting A (t1) → setting B (t2) → setting C (t3) ) → Setting A (t4) → Setting B (t5) → Setting C (t6)... The video signal gain and the shutter speed are sequentially changed. Then, as shown in FIG. 8, image data (GA (t1), GB (t2), GC (t3),...) Corresponding to each setting pattern is taken into the medium surface storage area, and the medium surface is detected. When performing processing (medium surface presence / absence determination processing), it is preferable to use a processing method in which comparison is made with an immediately preceding image of the same brightness (comparing images before and after the same set pattern in chronological order). Alternatively, in the case of an apparatus having the illuminating means 13, a processing method in which the illuminating means 13 is operated and the amount of illumination light is controlled so that a plurality of types of images are sequentially captured and compared with the immediately preceding image having the same brightness. It is also good.

As other processing forms, (1) a form in which the number of setting patterns of the video signal gain and shutter speed is changed, and (2) a video signal gain based on the average brightness and maximum brightness of the captured image. Is controlled so that becomes a reference value (optimum value), and an image of the same condition (adjusted video signal gain) is taken in. (3) Two image data of each pattern (image corresponding to setting A) Data GA (t1) → GA (t2), image data GB (t3) → GB (t4).. May be adopted.
<Media surface detection processing>
When detecting the surface of a medium such as a print medium or an image display medium (paper surface in this example), the image area of the image captured by the image capturing unit 14a is divided into a predetermined number of blocks by the monitoring unit 14b. Then, one or more specific blocks are set as monitoring blocks, and image components between corresponding monitoring blocks are compared in images before and after being periodically captured, and the amount of change in the image components in the monitoring block is monitored. At this time, in order to increase the processing speed, for example, it is preferable that a predetermined ratio of pixels in the pixel group in the monitoring block is thinned out, and the image components of the blocks including the pixel group are compared. In the present embodiment, for example, 1/2 pixel is thinned when entering the paper, and 1/4 pixel is thinned when the paper is removed. I try to change it. At that time, the number of pixels to be thinned out may be changed according to the size of the image, such as 1, 2, 3, 4.

  Here, the block division mode and the monitoring block setting mode will be described with specific examples.

  In the detection processing of the entry into the imaging range of the medium surface 1, for example, an area of 50% from the center of the captured image range is divided into 9 blocks (3 × 3). Here, 50% is a ratio to the length of the side (in the area, the area of 25% is divided). On the other hand, in the detection process of leaving from the imaging range, for example, 100% of the captured image range is divided into 9 blocks (3 × 3). The reason for dividing into a plurality of blocks is that monitoring a partial change in the image can detect the change in the image with higher accuracy than monitoring the change in the entire image.

  In the monitoring unit 14b, one or more specific blocks in the divided block group are set as monitoring blocks. The specific block is, for example, the circumference of (1) n × n, (2) n × m, (3) n × n blocks (annular block on the outer peripheral side), where n and m are integers of 2 or more. Only, (4) only around the m × n block, (5) only one or more blocks in the center, (6) any one of the four blocks separated by diagonal lines (or either 2 or 3 blocks). The shape of the block is not limited to a square, and the divided areas (1) to (5) may be a rectangle, a circle, a polygon, or the like, and these shapes are the shapes of a medium surface to which a code is attached. Alternatively, it may be set according to the type of code, the direction of entry of the medium, and the like.

  Furthermore, the pattern of these specific blocks may be made variable upon detection when the medium enters or leaves, or may be made variable depending on the image range. For example, if the target is made smaller, the processing speed becomes faster. Therefore, if the approach is detected only at the center of the angle of view suitable for decoding, it is sufficient to detect only one block at the center. If the position and movement within the detected angle of view are to be detected in detail, it is effective to increase the number of block divisions for the entire angle of view. The processing speed and accuracy can be improved by changing the number of blocks and the shape to be divided according to the part to be detected, the size of the detection target, and the angle of view.

  The monitoring unit 14b monitors the change amount of the image component using the specific block as a monitoring block. When detecting the medium surface, for example, a standard deviation of luminance values or an average luminance value is used as an image component. That is, the medium surface is detected by capturing a change in brightness and a change in pattern. Alternatively, in addition to the standard deviation and the average luminance value, the maximum value, minimum value, median value, average deviation, and 1/2 of the difference between the maximum value and the minimum value (a rough error is obtained), Standard deviation / average luminance, derivative, integral, X, Y profile, contrast, frequency component, histogram skewness, kurtosis, etc. as parameters, at least one of those parameters, or a combination thereof The amount of change may be monitored as an image component (step S12).

  The approach detection means 14c compares the amount of change in the image component between corresponding monitoring blocks and the threshold value in the images before and after being captured periodically, and detects the entry into the imaging range on the medium surface. For example, when the number of blocks to be determined (the number of designated blocks) is 1, the amount of change (the amount of change in standard deviation or average luminance in the preceding and following images) is outside the threshold range in the block group of the monitoring blocks. It is determined whether or not there is one or more blocks (step S13). If it is determined that there is one or more blocks, it is determined that the medium surface has entered, and the operation related to the medium surface detection is set to the standby state, and the code A trigger command for starting the reading operation is output by the trigger command output means 14d to start the code reading operation.

Note that the threshold value used for the determination of the medium surface approach detection (and medium surface departure detection) in step S13 is not fixed, but is preferably variable according to the environment when the image is captured. In the present embodiment, the threshold level is divided into five levels in consideration of the difference in color and pattern between the background and the medium surface. For example, an image captured before detecting the medium surface is used as a background image, and the threshold level is varied according to the difference between the image component of the background image and the image component when a change in the image component is detected. Even if the threshold level is not five steps, the number of steps may be reduced if the sensitivity is easily adjusted, and the number of steps may be increased if the sensitivity is adjusted accurately according to the environment. Further, the approach detection means 14c may detect the approach direction in addition to the entry detection. For example, using the change of the above-mentioned parameters other than the standard deviation and the average brightness, the changed block position and the changed order are stored to detect the direction in which the medium surface has entered, and the approach direction detection information is monitored block It may be used to set the shape of the image, or may be used in the code image extraction process.
<Image reading process for code reading>
In response to the trigger command, the control means 15 controls the operation of the imaging means 11 (and the illumination means 13) to capture an image under a certain condition (step S14). Note that, in order to be automatically applicable to the environment, in step S14, an image is captured using the gain of the video signal (adjusted video signal gain) detected in step S11 and the shutter pattern. Is desirable. Further, “other processing modes (1) to (3)” described in <Image capture processing during reading standby> may be employed.
<Decoding process>
The code decoding means 12 processes the image captured in step S14, extracts the image of the code written on the medium surface, decodes the code, and stores the decoded result in the decoding area. Since this decoding process is a known technique, a detailed description thereof will be omitted. In the case of a business code reader, the read code data (data after decoding the code in this example) is, for example, in the real-time transmission mode, via a communication cable or wireless communication means, the host system 20 In the batch processing mode, the data is accumulated and stored in the storage medium 18 (step S15).
<Leave detection processing>
The monitoring unit 14b targets the monitoring block for detecting separation (specific block) during the code reading operation (steps S14 and S15), and the image captured by the monitoring block during the reading operation. The component change amount monitoring process (similar to the above-described monitoring process in the <medium surface detection process>) is continued, and the separation detection unit 14e detects the amount of change in the image component being monitored and the threshold value (the threshold value for separation determination). ) Is detected from the imaging range of the medium surface, and the detection result (information indicating presence / absence = information indicating presence / absence of the medium surface) is stored in the medium surface detection area. In the present embodiment, the threshold value is a threshold value indicating a determination range (lower limit value 0 to upper limit value L), and in the separation detection unit 14e, the change amount of the image component continues for a certain period of time and changes within the above range. If it is the amount, that is, if there is no change in the image before and after a certain time, it is determined that there is no movement and the medium surface has been removed, and the state is shifted to a reading standby state for the next code (step S16). Thereafter, it is possible to automatically detect the medium surface and decode the code by repeating the operations in steps S11 to S16.

  In the code reading apparatus according to the present invention, in order to prevent the same code from being read twice, as shown in steps S17 to S27 in the flowchart of FIG. 8, the reading operation time depends on the decoding result and the detection result of the medium surface. (Timeout time) is set, and the code reading process and the medium surface separation detection process are performed.

  Hereinafter, the process relating to the twice reading prevention (double reading prohibition control) will be described along the flow of the processes shown in steps S17 to S27.

  The separation detection unit 14e sets an initial value of a reading operation time (hereinafter referred to as “timeout time”) used as a medium surface separation determination time (step S17), and reads the decoding result of the code decoding unit 12 from the decoding area. Whether the reading is successful, the twice reading state, or the reading failure (the code cannot be read) is determined based on the decoding result (step S18). If it is determined that the reading is successful (decoding is successful in this example), a reading prohibition time is set twice (step S19). On the other hand, if it is determined in step S18 that the reading state is twice, the twice reading prohibition time is extended (step S20), and the image change determination result in the medium surface detection process in step S16 is checked (step S21). ), If it is determined that there is a change, the timeout time is extended (step S22). On the other hand, if it is determined in step S18 that reading is unsuccessful, it is determined whether or not the reading time (1.5 seconds in this example) has elapsed (step S23). A buffer for collating whether the codes are the same code (reading state twice) is initialized (step S24). Subsequently, the image change determination result in the medium surface detection process in step S16 is checked (step S25). If it is determined that there is a change, the timeout time is extended (step S26).

  As in steps S17 to S26 described above, the separation detection unit 14e adjusts the time-out time according to the code reading state (decoding result) and the image change state (presence / absence of changes in the preceding and following images). Subsequently, the time from the start time of the code reading operation is compared with the timeout time to determine whether or not the timeout time has elapsed (step S27). If the time-out time has not elapsed, the process returns to step S14, and the code reading operation is repeated. If the time-out time has elapsed, the next code is placed in a reading standby state, and the code reading operation is terminated.

  FIG. 9 is a diagram illustrating an example of the operation time (medium surface separation determination time) setting table () used for the above-described separation detection processing, where “A” in FIG. 9 is a flag indicating that the reading timeout time is not extended, “ “B” is a flag indicating that the reading prohibition time is not extended twice, “C” is a flag indicating initialization of a buffer for checking whether the code is the same, “X” is a flag indicating an extension of the reading timeout time, and “Y” is two A flag indicating the extension of the reading prohibition time is shown. The X and Y times can be changed in stages.

  Using the control table as described above, the code decoding unit 12 adjusts the reading operation time according to the code reading state and the image change state, and executes the code reading process shown in steps S14 to S27 described above. Like to do.

  As another method for detecting the separation of the medium surface, as shown in the flowchart of FIG. 10, step S15A for capturing an image is provided after step S15 (decoding process) of the flowchart shown in FIG. It is also possible to detect the detachment of the medium surface by capturing an image under the same imaging conditions as in the reading standby. Or, similarly, an image is captured under the same imaging conditions as when waiting for code reading, and the first captured image (the image captured in step S14) and the captured image are captured when the medium surface is detected to enter. There is a method of comparing with an image (the image captured in step S15A) and determining that the image is out of the imaging range if a similar image is obtained or if the image has not changed for a certain period of time. May be adopted.

  Next, it is detected that the medium surface exists (or is stationary) at the center of the field of view (imaging range) of the image pickup means, and at that time, the code displayed on the medium surface is decoded. An embodiment to be started will be described. Since the overall operation is the same as that of the above-described embodiment, the description will be omitted or simplified.

  In the above-described embodiment, the condition of “with change” of the monitoring unit 14b is only whether or not the number of monitoring blocks in which an image change has been detected is equal to or greater than the specified number of blocks. As a monitoring function of the monitoring unit 14b, a function of monitoring the position of each block of the monitoring block whose image has changed is provided in addition to the “changed” monitoring. Further, as a detection function of the entry detection unit 14c, the medium surface exists in the center of the imaging range of the imaging unit 11 based on the positional information from the monitoring unit 14b (position information of the “changed” block). The function to detect that there is. In a preferred embodiment, the medium surface is present at (a) the central portion within the imaging range, and (b) is stationary at the central portion within the imaging range (stationary at substantially the central portion). ) Has a function that can be detected. In that case, either (a) or (b) can be selected as the trigger command depending on the situation. For example, when using a high-speed shutter or strobe lighting, the detection mode (a) can be used. Then, the trigger command output means 14d issues a trigger command for starting the code reading operation when it is detected that the medium surface exists in the center of the imaging range or is stationary. It is set as the form which outputs. Note that the series of processing by each of the above means is the processing of the medium surface detecting means 14, and does not limit the software configuration or the like. Hereinafter, the present embodiment will be described with specific examples. In the following specific example, the case of the detection mode (b) will be described as an example.

  FIG. 11 and FIGS. 12A to 12F are schematic views for explaining the processing mode of the medium surface detection means in the present embodiment. Here, as shown in FIG. 11, the area of 50% from the center of the imaging range 4 (captured image range) is divided into 9 blocks (3 × 3), and all of the divided 9 blocks are monitored block 3. The case will be described as an example.

  The medium surface detection means 14 monitors the position of the monitoring block whose image has changed, and starts the code reading operation when it is detected that the medium surface 1 is stationary at the center of the imaging range 4. For example, in the state of FIG. 12A, since there is no monitoring block with “changed”, it is determined that there is no medium, and for example, FIG. 12A → B → C. The image components between corresponding monitoring blocks in the preceding and following images are compared, and if the “change presence / absence” state at the position of each block transitions, it is determined that “medium surface approaching”. In FIG. 12, “0” indicates “no change” and “1” indicates “change”. The medium surface detection means 14 writes “1” to the position of the block where “changed” is detected, for example, using a table that stores the presence or absence of the change in correspondence with the position information of the monitoring block, and the monitoring block whose image has changed The movement of the medium surface is recognized by monitoring the position of the medium.

  Then, when comparing the image components between corresponding monitoring blocks in the preceding and following images and the state of “presence or absence of change” at the position of each block is fixed without transition, for example, FIG. As shown in (D), if the “changed” state of the same block position in the monitoring block group has not changed, it is determined that “the medium is stationary near the center in the imaging range”. To do. Also, as shown in FIGS. 12E and 12F, for example, if all of the monitoring blocks are “changed” in the preceding and following images, “the medium is stationary at the center in the imaging range. Is determined. At that time, if the monitoring block adopts the form of FIG. 6B (the form in which only the central block is the monitoring block), the state of the block at the central position remains “changed” and has not changed. At this time, it is recognized that “the medium is stationary near the center in the imaging range”. As described above, the medium surface detection unit 14 estimates the movement of the medium surface by monitoring the change state of the monitoring block at the position, and determines whether the medium surface is stationary or moving. When it is determined that the camera is stationary near or near the center, the decoding process is executed. It should be noted that the number of blocks for monitoring the stationary state by the variable factors such as the size of the medium surface 1, the size of the code 2, the notation position on the medium surface, the number of block divisions, etc. Is different. However, the number of blocks is set to be changeable according to a variable element on condition that at least the code 2 to be read is within the imaging range 4 (captured within the field of view of the imaging means 11).

  As described above, by monitoring the block position where the image has changed, the movement of the medium position can be known, so that it is possible to detect that the medium surface has come to the center of the image and is stationary. As a result, the media plane is captured at the center of the field of view and decoding is performed, so that incomplete images with codes outside the field of view are reduced, and image quality (image distortion, resolution near the center of the field of view) is reduced. ), The reading accuracy is improved.

  In addition, when applied to a stationary code reading device (for example, a code reading device in which a code reading device is arranged downward on a desk) that reads a code written on a medium surface of a card or a display surface of a mobile phone. However, in the case of the conventional code reader, the following problems occur, but in the case of the code reader to which the present invention is applied, no problem occurs.

  In a conventional stationary type code reader, for example, a person inserts a medium surface (a label on which a code encoded with a price etc.) is written on a reading surface (below the device) Will rest around the center of the field of view of the device and wait until it can be read. In this process, if you simply process “Imaging-Decoding-Imaging-Decoding ...”, the decoding time of the reader is long, so the image that is being inserted into the page (an image with a partial code in the field of view) If the paper surface is detected based on this and the decoding process is performed, the decoding will not only fail, but the decoding process time will be lost. Eventually, an image in which the code portion written on the medium surface is near the center of the visual field can be obtained, but the time loss causes the operator to become frustrated and to reduce efficiency.

  In the case of the code reading apparatus to which the present invention is applied, it is possible to detect the timing when the medium surface comes to the central visual field, and an image in the middle of approaching (an image in which part of the code is outside the imaging range) is decoded. It has excellent effects such as eliminating waste.

  In the above-described embodiment, the case where the present invention is mainly applied to a handy type business code reader used at a supermarket or a department store cash register has been mainly described as an example. However, the present invention can be read as described above. The surface is provided on the upper surface of the housing, and can be applied to a stationary code reading device that reads codes written on the medium surface of a card or the display surface of a mobile phone, and for business use only. In addition, the present invention can also be applied to various personal information processing apparatuses such as a mobile phone having a code reading function and PDA (Personal Digital Assistants).

It is an external view which shows an example of the code reader which has a medium surface detection function based on this invention.

It is a block diagram which shows the structural example of the code reader which concerns on this invention.

It is a functional block diagram which shows an example of a structure of the medium surface detection means which concerns on this invention.

It is a flowchart for demonstrating the outline | summary of this invention.

FIG. 5 is a partial view of the flowchart of FIG. 4.

It is a schematic diagram which shows the example of the monitoring block used for the medium surface detection process based on this invention.

It is a schematic diagram for demonstrating the outline | summary of the medium surface detection process based on this invention.

It is a flowchart for demonstrating the operation example of the code reader to which this invention is applied, and the detail of a medium surface detection process.

It is a figure which shows an example of the operation time setting table used for the separation detection process of a medium surface.

It is a flowchart for demonstrating the other example of the medium surface detection process based on this invention.

It is a 1st figure for demonstrating the other processing form of the medium surface detection means based on this invention.

It is a 2nd figure for demonstrating the other processing form of the medium surface detection means based on this invention.

Explanation of symbols

1 Medium 2 Reading target (code)
3 Monitoring block 4 Imaging range 10 Code reader 10a Reading surface 10b Reading switch 10c Support base 11 Imaging means 12 Code decoding means 13 Illuminating means 14 Medium surface detecting means 14a Image capturing means 14b Monitoring means 14c Intrusion detecting means 14d Trigger command output Means 14e Detachment detection means 15 Control means 15a CPU
15b Memory 20 Host system

Claims (11)

A medium surface detection program applied to a code reading device including an image pickup means for picking up an image and a code reading means for processing an image picked up by the image pickup means and reading a code written on the medium surface. ,
The code reader;
An image capturing means for operating the imaging means during standby to read the code and periodically capturing an image within the imaging range;
The image area in the center of the image captured by the image capturing means is divided into a predetermined number of blocks, and only one or more specific blocks among the divided blocks are captured as the monitoring blocks periodically. Monitoring means for comparing the image components between the corresponding monitoring blocks in the images before and after being inserted to monitor the amount of change in the image components in the monitoring block, and for monitoring the position of each block of the monitoring block in which the image has changed ,
An approach for detecting that the medium surface is present in the center of the imaging range of the imaging unit based on detection information of the change amount of the image component and position information from the monitoring unit during the code reading standby Detection means;
When detecting that the medium surface is present in the central portion, the medium surface detection is made to function as a trigger command output means for outputting a trigger command for starting the code reading operation. program. The entry detection means compares the image components between the monitoring blocks for each block corresponding to the same block position, and the change state of the image component of at least one block transitions from no change to a change state, and When it is determined that the state of change in the image component of each block corresponding to the same block position is the same in all blocks, it is detected that the medium surface is present at the center in the imaging range of the imaging means. The trigger command output means outputs a trigger command for starting the code reading operation when it is detected that the medium surface is stationary at the central portion. The medium surface detection program according to claim 1. If the elapsed time from the start of the reading operation of the previous SL code has passed the set timeout period as the leaving determination time of the medium surface, when the medium surface is removed either within et away the imaging range 3. The medium surface detection program according to claim 1, wherein the code reader further functions as a departure detection unit that detects and shifts to a reading standby state for the next code. 4. The medium surface detection program according to any one of claims 1 to 3, wherein the change amount of the image component is a change amount of a standard deviation or an average luminance value of the luminance values between the monitoring blocks. The image capturing means captures the image of each pattern by changing the gain and shutter speed setting of the video signal into a plurality of patterns when capturing the image, and the monitoring means captures image components between the monitoring blocks. 5. The medium surface detection program according to claim 1, wherein a change amount of an image component in each of the patterns is monitored when comparing the two. The monitoring unit, when setting the monitoring block, varies at least one of an image range to be divided, a shape and size of the block, and a number of divisions. Item 6. The medium surface detection program according to any one of Items 1 to 5. 7. The medium surface detection program according to claim 6, wherein the monitoring unit varies the element according to an operation mode of the code reader. The said approach detection means detects the approach of the said medium surface by using the number of the blocks from which the variation | change_quantity of the said image component is outside the range of a threshold value as a determination element of a medium surface detection. The medium surface detection program according to any one of the above. 4. The medium surface detection program according to claim 3, wherein when the code reading unit has a function of decoding the code, the separation detection unit sets the time- out period according to a decoding state of the code. 10. The medium surface detection program according to claim 1, wherein the medium surface to be detected includes a surface of a print medium, an image display medium, and a medium on which the code is directly marked. . A medium surface detection method in a code reading apparatus comprising: an image pickup unit that picks up an image; and a code reading unit that processes an image picked up by the image pickup unit and reads a code written on the medium surface,
Activating the imaging means at the time of waiting for reading the code to periodically capture an image within the imaging range;
The image area in the center of the image captured by the image capturing means is divided into a predetermined number of blocks, and only one or more specific blocks among the divided blocks are captured as the monitoring blocks periodically. Comparing the image components between corresponding monitoring blocks in the images before and after being loaded, monitoring the amount of change in the image components in the monitoring block, and monitoring the position of each block of the monitoring block where the image has changed ,
At the same time as detecting that the medium surface is present in the center of the imaging range of the imaging unit based on the detection information of the change amount of the image component and the positional information from the monitoring unit during the code reading standby. Starting the reading operation of the code;
Based on the change amount of the image component and the information on the elapsed time from the start time of the code reading operation, the separation of the medium surface from the imaging range is detected, and a transition to the reading standby state for the next code is made. Steps,
A medium surface detection method comprising:

Images