JP2014228345A - Distance detection device, reading device including distance detection device, distance detection method, and distance detection program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the need to incorporate a module dedicated to distance measurement and prevent reading of a barcode located at an unexpected distance.SOLUTION: A distance detection device performs predetermined processing on the basis of a result of first frequency analysis to image data obtained by reading a reading object image with a reading device, and a result of second frequency analysis to image data obtained by reading the reading object image with the reading device distant by a predetermined distance, so as to detect the distance between a reading object and the reading device.

Description

  The present invention relates to a distance detection device, a reading device including a distance detection device, a distance detection method, and a distance detection program for detecting a distance.

  Barcodes are widely used for the purpose of managing articles. As a method of using a bar code, a method of reading a bar code attached to or printed on an article by using a bar code reader (hereinafter referred to as “bar code scanner” as appropriate) held by a user is generally used. Is.

  However, when using the barcode reader, there may be a problem that a label far away from the hand is unexpectedly read instead of the barcode label desired to be read.

  This problem will be specifically described. “Distance at which barcode label can be read” is defined as a design specification of the barcode scanner. However, in reality, it is not defined after the distance between the barcode scanner and the barcode label is accurately measured to determine whether decoding is possible. Realistic barcode label reading distance is the distance that the illumination reaches with effective intensity, and the optical to properly image the barcode scanner sensor (focal length, aperture, sensor tolerance) This depends on the effective focal width (depth of field) and the like. Furthermore, the size of the bar code label and the width of each stripe pattern constituting the bar code (minimum module width) are greatly affected.

  In other words, regardless of the distance to the barcode label, the barcode scanner determines the “readable distance” as a result depending on whether or not the video imaged on the sensor can be decoded. The area outside the distance between the barcode scanner and the label that can be read is in a so-called out-of-focus state, and thus is a “distance that cannot be practically decoded”.

  By the way, when reading a bar code label with a bar code scanner, depending on the conditions, the label may not be at the user's hand, but a label on the table or a label on the foot, etc. There was a problem that the label could be read. For example, if the barcode label is printed so large that it is out of the expected range, and it is far from the expected reading distance, reading beyond the expected range becomes possible. It is such a problem.

  In order to technically solve this problem, a method of incorporating a distance measurement module into the barcode scanner can be considered. This distance measurement module is, for example, an optical or ultrasonic module.

  An example of such a technique is described in the specification paragraph [0018] and the specification paragraph [0034] of Patent Document 1.

  Specifically, the barcode reader described in Patent Document 1 optically reads the barcode data described on the barcode label, and electrically converts the barcode data optically read by the reading unit. It includes a portion as a general bar code reader, which is a photoelectric conversion unit for converting into a signal and a decoding unit for decoding a data character from an electric signal converted by the photoelectric conversion unit. The barcode reader of the cited document 1 further includes a distance sensor that is a distance measuring means for measuring the distance from the barcode reader to the barcode label. Then, by comparing the distance measured by the distance sensor with the measurement allowable distance range stored in the memory, it is determined whether or not the barcode data currently read by the reading unit is valid. Note that Patent Document 1 describes that the distance sensor may be constituted by an infrared LED and a phototransistor, or may be measured by ultrasonic waves or laser light.

JP 2006-201921 A

  Solution of the problem of erroneously reading a barcode existing at an unexpected distance by adopting a method of incorporating a distance measurement module into the barcode scanner as described in Patent Document 1 and the like described above Leads to. However, in the method of incorporating a module for distance measurement as described in Patent Document 1 or the like, strictly speaking, a distance at a position slightly different from the object to be actually measured is measured. It was. Further, there are problems that the barcode scanner becomes larger and the cost increases due to the increase in the number of parts.

On the other hand, as another distance measurement method, a method of mixing a distance measurement pulse with an illumination light source of a barcode scanner and measuring a time difference of the pulse response with an image acquisition sensor is also conceivable. However, while the time that must be observed is as short as 10 ^-11 seconds, the time that data can be acquired from the sensor is about 10 ^-3 seconds, so both data acquisition and distance measurement can be ensured. It was difficult to realize.

  In this way, with bar code readers, it is necessary to measure the distance by some means so as not to misread bar code labels in the distance. There was no means.

  Therefore, the present invention eliminates the need for incorporating a dedicated module for distance measurement, and can prevent reading of a barcode at an unexpected distance, and a distance detection device and a reader equipped with the distance detection device An object of the present invention is to provide a distance detection method and a distance detection program.

  According to the first aspect of the present invention, the result of the first frequency analysis on the image data obtained by reading the reading target image with the reading device and the reading target image separated by a predetermined distance by the reading device. The distance between the reading object and the reading device is detected by performing a predetermined process based on the result of the second frequency analysis on the image data obtained by reading. A detection device is provided.

  According to the second aspect of the present invention, the result of the first frequency analysis on the image data obtained by reading the reading target image with the reading device and the reading target image separated by a predetermined distance by the reading device. The distance between the reading object and the reading device is detected by performing a predetermined process based on the result of the second frequency analysis on the image data obtained by reading. A detection method is provided.

  According to the third aspect of the present invention, the result of the first frequency analysis on the image data obtained by reading the reading target image with the reading device and the reading target image separated by a predetermined distance by the reading device. The distance between the reading object and the reading device is detected by performing a predetermined process based on the result of the second frequency analysis on the image data obtained by reading. A distance detection program is provided that causes a computer to function as the detection device.

  According to the present invention, it is not necessary to incorporate a dedicated module for distance measurement, and bar code reading at an unexpected distance can be prevented.

It is a figure showing the basic composition of the embodiment of the present invention. It is a figure showing the flow of the light at the time of reading of embodiment of this invention. It is a figure showing an example of the functional block contained in the processor in embodiment of this invention. It is a figure showing the relationship between barcode reading and a focus position. It is a figure (1/6) explaining the frequency analysis in embodiment of this invention. It is a figure (2/6) explaining the frequency analysis in embodiment of this invention. It is a figure (3/6) explaining the frequency analysis in embodiment of this invention. It is a figure (4/6) explaining the frequency analysis in embodiment of this invention. It is a figure (5/6) explaining the frequency analysis in embodiment of this invention. It is a figure (6/6) explaining the frequency analysis in embodiment of this invention. It is a figure showing an example of a general barcode label. It is a figure showing the label which modeled the barcode label for explanation. It is a figure showing about the received light intensity at the time of reading the label shown in FIG. 6 in appropriate distance. FIG. 7 is a diagram in which the received light intensity when the label shown in FIG. 6 is read at an appropriate distance and the received light intensity when read at an inappropriate distance are superimposed. FIG. 7 is a diagram in which the received light intensity when the label shown in FIG. 6 is read at an appropriate distance and the frequency analysis result of the received light intensity when read at an inappropriate distance are superimposed. It is the figure which expanded a part of FIG. It is a figure showing the label which modeled the barcode label for explanation. It is a flowchart showing the basic operation | movement of embodiment of this invention. FIG. 12 is a diagram illustrating received light intensity when the label illustrated in FIG. 11 is read at an inappropriate distance. It is a figure showing about the light reception intensity | strength at the time of reading the label shown in FIG. 11 in appropriate distance. FIG. 12 is a diagram in which the received light intensity when the label shown in FIG. 11 is read at an appropriate distance and the received light intensity when read at an inappropriate distance are superimposed. FIG. 12 is a diagram in which the received light intensity when the label shown in FIG. 11 is read at an appropriate distance and the frequency analysis result of the received light intensity when read at an inappropriate distance are superimposed.

  First, an outline of an embodiment of the present invention will be described. The embodiment of the present invention is characterized in that the distance between a barcode scanner (barcode reader) and a barcode label is roughly measured by analyzing the image of the barcode reflected on the sensor of the barcode scanner. is there. Furthermore, this embodiment is characterized in that no special sensor other than the sensor for functioning as a barcode scanner is required to realize this.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  1-1 and FIG. 1-2 show a barcode scanner 100 and a barcode label 106 according to the present embodiment. Here, FIG. 1-1 is a diagram exclusively showing an example of the components of the barcode scanner 100. FIG. 1-2 is a diagram illustrating an optical path when the barcode scanner 100 further performs reading.

  Referring to FIGS. 1-1 and 1-2, the barcode scanner 100 of this embodiment includes a processor 101, an image sensor 102, a condenser lens / filter 103, a reflection mirror 104, and an illumination light source 105. In addition, FIGS. 1-1 and 1-2 show a barcode label 106 to be read by the barcode scanner 100. FIG.

  The basic configuration of the barcode scanner 100 is the same as the basic configuration of a general barcode scanner, and an image sensor 102 for acquiring an image is included in order to realize a function as a barcode scanner. However, other special sensors and physical mechanisms are not included. In other words, the barcode scanner 100 is not provided with a special physical module only for distance acquisition.

  The barcode scanner 100 reads the barcode label 106 under the control of the processor 101. Specifically, the illumination light source 105 irradiates the barcode label 106. Then, the reflection mirror 104 reflects the reflected light of the barcode label 106 based on the irradiation of the illumination light source 105. Then, the reflected light from the reflecting mirror 104 is acquired by the image sensor 102 through the condenser lens / filter 103 that appropriately passes the condenser lens and the irradiation light. The acquired reflected light is decoded by the processor 100, and the decoding result is transmitted to the host device via a line for communicating with the host device.

  Note that the reflection mirror 104 can be omitted depending on the shape of the barcode scanner 100. Further, the condensing lens / filter 103 may be realized only by the condensing lens if no filter is required.

  The processor 101 corresponds to the “distance detection device” of the present invention. The barcode scanner 100 corresponds to the “reading device including the distance detection device” of the present invention.

  Next, functional blocks included in the processor 101 will be described with reference to FIG.

  Referring to FIG. 2, the processor 101 includes a sensor control unit 101-1, a processing unit 101-2, a storage unit 101-3, and a data transmission / reception unit 101-4.

  The sensor control unit 101-1 includes a function for controlling the image sensor 102 and a function for acquiring data by the image sensor 102. The acquired data is stored in the storage unit 101-3. In this description, it is assumed that the image sensor 102 is an image sensor having a width of 256 dots. However, this is only an example for explanation, and the dot width of the image sensor 102 is particularly limited. There is no limit.

  The processing unit 101-2 has a function of controlling the entire barcode scanner 100. The processing unit 101-2 receives the data acquired by the image sensor 102 from the sensor control unit 101-1, and stores the data in the storage unit 101-3. Then, the processing unit 101-2 performs processing such as image analysis based on the data stored in the storage unit 101-3 and the “distance / normalization correspondence table” stored in the storage unit 101-3. It also has a function of detecting the distance between the code scanner 100 and the barcode label 106. Here, the specific data of the distance / normalization correspondence table will be described later.

  The storage unit 101-3 is a storage unit that stores data acquired from the image sensor 102. The storage unit 101-3 also stores a distance / normalization correspondence table that is data measured in advance.

  When the distance between the barcode scanner 100 and the barcode label 106 is within an appropriate range, the image data acquired by the image sensor 102 is binarized, and the binarized data corresponds to the barcode type. The decoded data is output to the data transmitting / receiving unit 101-4.

  The data transmission / reception unit 101-4 has a function for transmitting / receiving data between the barcode scanner 100 and the host device. The data transmitting / receiving unit 101-4 transmits the data input from the processing unit 101-2 to the higher-level device.

  It should be noted that each functional block included in the processor 101 is unique to the present embodiment in which an arithmetic processing device (not shown) included in the processor 101 is stored in the storage unit 101-3 or another storage unit (not shown). This is realized by performing arithmetic processing based on a program and controlling various hardware based on the result of the arithmetic processing. Further, a part of the functions included in the processor 101 may be realized by another device such as a host device. A part or all of the distance detection apparatus configured using the processor 101 may be configured by hardware that operates without using a program.

  Next, a method for detecting the distance between the barcode scanner 100 and the barcode label 106 in the processing unit 101-2 of this embodiment will be described in detail.

  In the present embodiment, from the video read by the image sensor 102 of the barcode scanner 100, the received light intensity distribution of light based on the video is analyzed, and frequency analysis (for example, Fourier transform) is performed. Processing for obtaining the distance from the barcode label 106 is also performed.

  More specifically, in the present embodiment, the video image projected on the image sensor 102 and read by the image sensor 102 is subjected to frequency analysis, and the video image projected on the image sensor and read by the image sensor 102 is decoded. A process for obtaining the distance between the barcode scanner 100 and the barcode label 106 is performed by comparing the binarized signal with a frequency analysis result.

  In this regard, as described in the section [Means for Solving the Problems], in the general technique, strictly speaking, a position slightly different from the barcode label which is an object to be actually measured and the barcode scanner are different. In addition to measuring the distance between them, the problem is that the barcode scanner becomes larger and the cost increases due to an increase in the number of parts.

  However, if this means of the present embodiment is used, the distance measurement object can be the barcode label itself. Furthermore, according to the present embodiment, distance measurement can be realized with a general barcode scanner component. That is, in the present embodiment, it is possible to solve the problems that the general technology has.

  Note that Fourier transform may be used to read frequency domain data to be subjected to frequency analysis from image data. In particular, in order to increase the speed, a fast Fourier transform (FFT) may be used.

  Here, the basic principle of the present embodiment will be described with reference to FIG.

  First, as a premise, when the barcode label 106 moves away from the focal position as compared with the barcode label 106 at the optical focal position of the barcode scanner 100, an image reflected on the image sensor of the barcode scanner 100 is blurred. This is represented by 301 to 303 shown in the upper part of FIG.

  The bar code label 106 is realized by a two-color portion (for example, a white portion and a black portion) having no intermediate color. When the barcode label 106 is at an appropriate focal position, the boundary between the white part and the black part is clear as in 301. However, when the barcode label 106 is slightly separated from the appropriate focal position, the image formed on the image sensor of the barcode scanner 100 becomes blurred as indicated by 302. When the image is further away from 302, the image is more blurred than 302, as indicated by 303.

  When the image formed on the image sensor of the barcode scanner 100 is not blurred, the received light intensity at the image sensor of the barcode scanner 100 is steep at the white / black boundary portion of the barcode. Or it changes in a step shape. On the other hand, when the image formed on the image sensor of the barcode scanner 100 is blurred, the received light intensity at the image sensor of the barcode scanner 100 is the boundary between the white and black boundaries of the barcode. It will change gently. This is indicated by 304 to 306 in FIG. When the barcode label 106 is in an appropriate focal position and the read image 301 can be obtained, the portion where the reflectance changes, that is, the white / black boundary portion of the barcode is clear (that is, at the boundary portion). Waveform data 304 (having a steep or step change) is obtained. On the other hand, when the barcode label 106 is separated from the appropriate focal position and the read image 302 is obtained, the portion where the reflectance changes, that is, the white / black boundary portion of the barcode is unclear ( That is, waveform data 305 is obtained in which the change at the boundary portion is gentle. When the barcode label 106 is further away from the appropriate focal position to obtain the read image 303, the portion where the reflectance changes, that is, the white / black boundary portion of the barcode is further unclear (ie, the boundary). Waveform data 306 is obtained. As described above, when the video is blurred and the boundary between white and black is gentle, the frequency tends to be low when the frequency analysis is performed, compared to the case where the barcode label 106 is at an appropriate focal position. On the other hand, an object at an appropriate focal position tends to have a high frequency because the boundary between white and black changes sharply. That is, when the barcode label 106 is at the focal position from the barcode reader, the waveform data to be read is rectangular data with a steep black and white changing portion. However, when the barcode label 106 is at a position deviated from the focal position from the barcode reader, the waveform data to be read is rectangular data with a gentle black and white changing portion. Therefore, only low-order harmonics are included.

  In the present embodiment, the relationship between the frequency deviation by the frequency analysis of the image and the distance from the barcode reader of the barcode label is examined in advance for each distance and stored as a distance / normalization correspondence table. Stored in the unit 101-3. The amplitude sum of the AC frequency components in the frequency data obtained by performing Fourier transform on the waveform data obtained from the image data read by the sensor image sensor 102 is included in the distance / normalization correspondence table. Compared with the amplitude sum of the frequency components, the distance corresponding to the frequency data with the closest amplitude sum is obtained as an estimated value of the actual distance.

  Here, frequency analysis that is preprocessing for comparison will be described in detail with reference to FIGS.

  The image sensor in the description of the frequency analysis is assumed to be a line image sensor in which a total of 256 pixels are arranged one by one in the horizontal direction. Each light receiving element is assumed to be numbered 0, 1,..., 255 from the left. The maximum value of received light intensity is set to 1, and the minimum value is set to 0.

  At this time, when the horizontal axis is the number of the light receiving element and the vertical axis is the light receiving intensity of each light receiving element, the waveform is as shown in FIG. Here, the waveform of FIG. 4A is a sine waveform.

  In the example of FIG. 4A, a sinusoidal waveform for one cycle is set for 256 light receiving elements, and this is defined as a wavelength 1.

  When the 256 received light intensity data in FIG. 4A are subjected to frequency analysis (using the absolute value of the complex number obtained as a result of analysis by FFT), the result is as shown in FIG. The horizontal axis of the frequency analysis result in Fig. 4-2 is

That is, the frequency itself. In FIG. 4B, the vertical axis is 128 when the horizontal axis is 0, and the vertical axis is 64 when the horizontal axis is 1.

  In general, in the case of sound waves and radio waves, the equation of wavelength × frequency = velocity is established, but in the present embodiment, there is no specific velocity component or time component. It is assumed that the frequency = constant, and constant = 1 for further simplicity.

  In FIG. 4B, 0 on the horizontal axis indicates a direct current component that is not indicated as a frequency or wavelength. This means that the data in the state where the waveform in FIG. 4A is raised by +0.5 with respect to the sine waveform is the total value of 256, that is, 0.5 × 256 = 128 components are expressed. .

  The horizontal axis 1 appearing in FIG. 4-2 is as described above.

That is, it means that the wavelength is 1 and the frequency is 1.

  The above description can be similarly applied to the case of the wavelength 1/4 and the case of the wavelength 1/16.

  FIG. 4C is a diagram illustrating a received light intensity distribution in the case of the wavelength ¼ (meaning that the waveform has four periods with respect to the entire width of the image sensor element). FIG. 4-4 is a diagram illustrating a result of frequency analysis of FIG. 4-3. Referring to FIG. 4-4, similarly to FIG. 4-1, the vertical axis 128 is obtained when the horizontal axis is 0, and the vertical axis 64 is obtained at the horizontal axis 4. “4” on the horizontal axis indicates the frequency.

  FIG. 4-5 is a diagram illustrating (a part of) the received light intensity distribution when the wavelength is 1/16. 4-6 is a diagram illustrating a result of frequency analysis of FIG. 4-5. Referring to FIG. 4-6, as in FIG. 4A, the vertical axis 128 when the horizontal axis is 0, and the vertical axis 64 at the horizontal axis 16. The horizontal axis “16” indicates the frequency.

  Thus, if the periodic waveform having one period in the entire width of the image sensor is wavelength 1, and the frequency at this time is 1, the horizontal axis of the result of frequency analysis of the waveform data indicating the image sensor received light intensity is the frequency, The vertical axis indicates the intensity of the frequency component. As the intensity of the frequency component, as described above, an amplitude that is an absolute value of a complex value obtained as a result of analysis by FFT may be used, but a power that is the square thereof may be used.

  When the value on the horizontal axis is small, the frequency is “low”, and when the value is large, the frequency is “high”.

  Hereinafter, the data of the figure shown by the above-mentioned description is shown as a table | surface. Here, Table 1-1 and Table 1-2 show the sensor light reception intensity of each waveform, and Table 2 shows the result of frequency analysis of the sensor light reception intensity of each waveform.

  In the above description, Fast Fourier Transform (FFT) is used for frequency analysis. For this reason, the number of valid data of the analysis result is half of the number of data of the analysis source. That is, in this example, the number of waveform data of the analysis source is 256 from 0 to 255, so the number of effective data of the frequency data of the analysis result is 128 from 0 to 127.

  The above is the concept of frequency analysis in the present embodiment. Next, frequency analysis using a specific example and comparison based on the analysis result will be described in detail.

  FIG. 5 shows a general barcode label 501 as a specific example of the barcode label 106. What is actually read when the barcode scanner 100 is normally used is a general barcode label such as the barcode label 501. However, in the following description, in order to simplify the description, a description will be given using a label 601 in which vertical stripes are drawn at equal intervals simulating the barcode label shown in FIG.

  When the label 601 in FIG. 6 is arranged at a position that becomes the optical focus of the barcode scanner, an image is appropriately formed on the image sensor unit 102. The white portion of the label 601 has a high light reception intensity, and the black portion has a light reception intensity. The image sensor output can be obtained in a low state.

  In order to simplify the description, the value of the received light intensity of the white portion acquired by the image sensor 102 when reading is performed at an appropriate distance is set as the maximum value of the image sensor output. In addition, the value of the received light intensity of the black portion acquired by the image sensor 102 when reading is performed at an appropriate distance is set to zero. Further, it is assumed that the light receiving element of the image sensor has 256 pixels. In this case, when the received light intensity value obtained from the image sensor is normalized with the maximum value being 1, the horizontal axis represents the pixel position of the image sensor 102 and the vertical axis represents the received light intensity value. It will be done.

  Next, FIG. 8 enlarges a part of FIG. 7 (for 40 pixels), and shows the received light intensity when the barcode label is at a predetermined distance from the position where it becomes the optical focus of the barcode scanner. FIG.

  A broken line 801 in FIG. 8 shows a received light intensity waveform of the image sensor when the barcode label is at a position where it becomes the optical focus of the barcode scanner. That is, reference numeral 801 is an enlarged version of the waveform shown in FIG. As apparent from reference numeral 801, there is a certain pixel having a light reception intensity of 1, and the light reception intensity is 0 in a pixel adjacent to the certain pixel. In this way, when the barcode label is at a position where it becomes the optical focus of the barcode scanner, it is possible to accurately measure whether the received light intensity is 1 or 0, so that the waveform is steep. .

  On the other hand, when the bar code label is not at the position where it becomes the optical focus of the bar code scanner, the boundary between the white part and the black part becomes a gentle curve as shown by the solid line 802 in FIG. This is because the received light intensity in the vicinity of the boundary takes a value other than 1 or 0 and changes gently. In this example, there are about six pixels having a value greater than 0 and less than 1 between a pixel having a value of 0 and a pixel having a value of 1.

  Next, FIG. 9 shows a case where the barcode label is at a position where it becomes the optical focus of the barcode scanner, and a position where the barcode label is separated from the position where it becomes the optical focus of the barcode scanner by a predetermined distance. , The results of frequency analysis by fast Fourier transform are superimposed on the received light intensity waveform (corresponding to the waveform of the broken line 801 and the waveform of the solid line 802 in FIG. 8). A broken line 901 is a frequency analysis of a binarized waveform of the image sensor intensity waveform (corresponding to the waveform of the broken line 801 in FIG. 8), and a solid line 902 is a frequency analysis of the image sensor intensity (corresponding to the waveform of the solid line 802 in FIG. 8). It is a thing.

  FIG. 10 is a partially enlarged graph obtained by enlarging the frame 903 in FIG. Also in the enlarged view, a broken line 901 is a frequency analysis of a binarized waveform of the image sensor intensity waveform (corresponding to the waveform of the broken line 801 in FIG. 8), and a solid line 902 is the image sensor intensity (the waveform of the solid line 802 in FIG. 8). Is equivalent to frequency analysis.

  Referring to FIG. 10, the frequency / amplitude characteristics (see solid line 902) as a result of frequency analysis when the barcode label 501 is located at a predetermined distance from the optical focus of the barcode scanner 100 are shown in FIG. Compared with the frequency / amplitude characteristics (see the broken line 901), which is the result of frequency analysis when the code label 501 is located at the optical focal point of the barcode scanner 100, the overall amplitude of the value of the high frequency component It can be seen that is smaller.

  Tables relating to the contents shown in FIGS. 7 to 10 are shown below. Here, Table 3-1 and Table 3-2 represent the sensor light reception intensity of each waveform, and Table 4 represents the result of frequency analysis of the sensor light reception intensity of each waveform.

  Tables 3-1 and 3-2 show the correspondence between the pixel number in the image sensor 102 and the received light intensity corresponding to each pixel number, and the barcode label 501 is at the optical focal position of the barcode scanner 100. The table shows the case where the barcode label 501 is not at the optical focal length of the barcode scanner 100 for comparison.

  Table 4 shows the correspondence between the frequency number in the frequency domain and the amplitude corresponding to each frequency number, when the barcode label 501 is at the optical focus position of the barcode scanner 100, and when the barcode label 501 is a bar code. It is the table | surface shown side by side so that it can compare with the case where it is not in the optical focal distance of the code scanner 100. FIG.

  In order to quantitatively show the difference in the frequency analysis results as shown in Table 4, the frequency analysis results are arranged in a table, and then the total values of the frequency analysis results are compared. That is, in the above example, the total value from the amplitude corresponding to frequency number 1 to the amplitude corresponding to frequency number 127 is obtained for each case, and the two total values obtained thereby are compared. As a comparison, for example, the ratio of the total value corresponding to the case where it is not known whether or not it is in the focal position to the total value corresponding to the case where it is in the focal position is obtained.

  Then, the sensor total value corresponding to the case where the barcode label is at the focal position (referred to as “total value 1”) and the total value corresponding to the case where the barcode label is located at a predetermined distance from the focal position ( And “total value 2”), it can be seen that the total value 2 is about 21.9% smaller than the total value 1.

  However, it is possible to determine whether or not the barcode label is at a position away from the focal length of the barcode scanner 100 by using the total value itself of the frequency analysis results or the comparison result of the total values. It is not easy to determine how far away they are.

  Therefore, in the present embodiment, a plurality of distances between the barcode label and the barcode scanner 100 are set in advance, and the barcode label and the barcode scanner 100 are separated by the distance for each set distance. The total value of the frequency analysis values obtained in this case (that is, the value obtained by summing the amplitude for each frequency for frequencies other than DC) is obtained. The correspondence between the distance and the total value is held. The distance includes a focal length (that is, an appropriate distance). Then, a ratio between the total value corresponding to each distance and the total value corresponding to the focal length is obtained. Then, the ratio corresponding to each distance and the total value corresponding to the focal length are stored in the storage unit 101-3 in advance.

  When the barcode scanner 100 reads a barcode, the ratio between the total value obtained by the reading and the focal length stored in the storage unit 101-3 is calculated, and the ratio closest to the calculated ratio Is stored in the storage unit 101-3, and the distance corresponding to the closest ratio is estimated as the actual distance between the barcode scanner 100 and the barcode when the barcode is read.

  In the above example, the ratio is used, but instead, the correspondence relationship between each distance and the total value corresponding to the distance is stored in advance in the storage unit 101-3 for a plurality of distances. When the code scanner 100 reads the barcode, the total value closest to the total value obtained by the reading is searched from the storage unit 101-3, and the distance corresponding to the closest total value is read from the barcode. The actual distance between the barcode scanner 100 and the barcode may be estimated.

  Furthermore, in any of the above cases, it is preferable to perform the above processing after normalizing the amplitude of each frequency with the amplitude of the direct current.

  Note that the memory 101-3 may be used as a memory for storing the distance / normalization correspondence table, but other memory may be used.

  In the above method, the above-described ratio corresponding to each distance and the total value corresponding to the focal length are stored in the storage unit 101-3 in advance, or each distance is stored in the storage unit 101-3 in advance. It is necessary to store the correspondence between the distance and the total value corresponding to the distance for a plurality of distances. That is, it is necessary to perform measurement and calculation in advance and store the calculation result in the storage unit 101-3. In the above method, the accuracy of distance estimation can be maintained when reading the same barcode, but the accuracy of distance measurement cannot always be maintained when reading different barcodes.

  On the other hand, when the method described below is used, it is not necessary to store any data in the storage unit 101-3, and the barcode image itself obtained by one barcode reading operation can be used. It can be determined whether or not the barcode is at the focal position of the barcode scanner 100. That is, each time a barcode is read, it can be determined from the barcode image obtained at the time of reading whether the barcode is at the focal position of the barcode scanner 100.

  That is, in this method, binarized data obtained by the “step of binarizing the received light intensity waveform”, which always exists when the bar code label is decoded by the bar code scanner, is used.

  Then, the binarized data obtained in this binarization step is regarded as virtual ideal waveform data (waveform data when the barcode label is at the focal position). Then, the binarized data is subjected to frequency analysis. On the other hand, the original barcode image before binarization is also subjected to frequency analysis. Then, using the results of these two frequency analyses, it is determined whether or not the barcode is at the focal position of the barcode scanner 100.

  Thus, the frequency analysis result when the barcode label is assumed to be at the focal position of the barcode scanner 100 and the frequency when it is unknown whether the barcode label is at the focal position of the barcode scanner 100 or not. Using the analysis result, it is determined whether or not the barcode label is actually at the focal position of the barcode scanner 100, and if it is not at the focal position, the distance from the focal distance is obtained. be able to.

  In more detail, on the other hand, the sum of the amplitudes of all the AC frequencies obtained by frequency analysis of the data before binarizing the read barcode image (referred to as “amplitude sum before binarization”). On the other hand, the data after binarizing the read barcode image is subjected to frequency analysis to obtain the sum of amplitudes of all AC frequencies (referred to as “pre-binary amplitude sum”). . Then, a ratio of the amplitude sum before binarization to the amplitude sum after binarization is calculated. If the calculated ratio is within a predetermined range from 100%, it is determined that the barcode is at the focal position of the barcode scanner 100. In addition, if there is existing data regarding the relationship between the distance between the barcode position and the focal position of the barcode scanner 100 and the ratio of the amplitude sum before binarization to the amplitude sum after binarization, this data is present. By referring to, it is possible to estimate how far the currently read barcode is from the focal position of the barcode scanner 100 based on the ratio obtained from the currently read barcode.

  For reference, a normal method of arithmetically determining the distance from the total frequency analysis result itself or the difference from the ideal waveform can accurately determine the distance of the barcode to the barcode scanner 100. The following explains why it is difficult. That is, the focal length of the lens of the barcode scanner, the performance of the lens, the optical F value, the permissible circle of confusion (pixel size) of the image sensor, the distance at which the barcode label is focused, and the irradiation from the barcode scanner Since the distance from the barcode to the barcode scanner 100 determined by a normal method depends on the design specifications of the barcode scanner itself, such as the intensity of illumination, even if such a distance is calculated by a normal method The distance accuracy cannot be increased. In other words, since the difference between the total frequency analysis result itself and the ideal waveform depends on the type of barcode scanner, it is usually necessary to set a predetermined standard that can be applied uniformly to multiple types of barcode scanners. It is difficult to find the distance by this method.

  Next, the operation of this embodiment will be described with reference to FIG. FIG. 12 is a flowchart and an image diagram showing the basic operation of the present embodiment. This operation is an example of an operation assuming a case where a general bar code label such as the label 501 in FIG. 5 is read. In order to simplify the explanation, the label 1001 in FIG. 11 simulating an actual label is used.

  First, the reading process of the barcode scanner 100 is started (step S11). An image diagram of the barcode to be read is shown together with step S11 in the flowchart.

  Next, each part in the bar code scanner 100 cooperates to form an image on the bar code label on the image sensor 102 (step S12). Note that an image of a label schematically representing a bar code label is shown together with step S12 in the flowchart.

  Then, the image sensor control unit 101-1 acquires barcode image data having a waveform indicating the received light intensity from the image sensor 102. The acquired barcode image data is stored in the storage unit 101-3 by the processing unit 101-2 (step S13). A schematic waveform diagram of the barcode image data having a waveform indicating the sensor light reception intensity is also shown together with step S13 in the flowchart.

  Next, the binarized barcode image data is obtained by binarizing the pre-binarized barcode image data obtained in step S13 (step S14). A schematic waveform diagram of the waveform of the barcode image data after binarization is shown together with step S14 in the flowchart.

  At this time, if the bar code 106 is deviated from the optical focus position of the bar code scanner 100, the bar code label 106 appears unclearly on the image sensor 102 without being in focus, thereby binarizing. The black and white border portion of the previous barcode image data becomes gentle. For example, it is assumed that the received light intensity waveform as shown in FIG. 13 is obtained in the image sensor 102 with respect to the label of FIG. Note that the numerical values in FIG. 13 are normalized (the maximum value is 1).

  The waveform of the pre-binarized barcode image data in FIG. 13 has a slightly smooth white / black boundary. FIG. 14 shows the waveform of the binarized barcode image data obtained by binarizing the pre-binarized barcode image data whose waveform is shown in FIG.

  Further, the partial enlargement obtained by superimposing the waveform of the pre-binarized barcode image data and the post-binarized barcode image data shown in FIGS. 13 and 14 and further magnifying a part thereof. The figure is FIG. In FIG. 15, the broken line 1501 is the waveform of the barcode image data after binarization (corresponding to the waveform shown in FIG. 14), and the solid line 1502 is the waveform of the barcode image data before binarization with the received light intensity as it is (see FIG. 15). 13).

  Next, frequency analysis is performed on the pre-binarized barcode image data (step S16). In parallel with this, the binarized barcode image data is subjected to frequency analysis (step S15). For these frequency analysis, for example, a fast Fourier transform is used. In addition, the image figure of each frequency analysis result is written together with step S15 and step S16 in a flowchart.

  FIG. 16 shows the result of the frequency analysis in step S15 and the result of the frequency analysis in step S16 in an overlapping manner. A broken line 1601 indicates the result of the frequency analysis in step S15, and a solid line 1602 indicates the result of the frequency analysis in step S16. That is, the broken line 1601 indicates the frequency / amplitude characteristic that is the result of the frequency analysis of the binarized barcode image data, and the solid line 1602 indicates the frequency that is the result of the frequency analysis of the pre-binarized barcode image data.・ Shows amplitude characteristics.

  Next, the binarized amplitude sum described above, which is the sum of the amplitudes of all AC frequencies obtained by frequency analysis of the binarized barcode image data in step S15, and binarization in step S16 The above-mentioned pre-binarization amplitude sum, which is the sum of the amplitudes of all AC frequencies obtained by frequency analysis of the previous barcode image data, is obtained, and then, according to the following calculation formula, A ratio of the difference to the sum of amplitude after binarization (that is, a normalized difference) is obtained (step S17).

Normalized difference = difference / amplitude sum after binarization
= (Pre-binarization amplitude sum-binarization amplitude sum) / binarization amplitude sum On the other hand, before or after the processing of steps S15 to S17, or in parallel with the processing of steps S15 to S17, step S18 Is implemented.

  In step S18, the post-binarized barcode image data obtained in step S14 is decoded by a method corresponding to the barcode standard (step S18). Next, it is confirmed whether or not the decoding is successful (step S19).

  Here, if the decoding is successful (Yes in step S19), the process proceeds to step S20 which is a step of determining the distance.

  Here, the storage unit 101-3 stores a distance / normalized difference correspondence table in which correspondence between the distance of the barcode to the barcode scanner 100 and the normalized difference is summarized for a plurality of assumed distance ranges. ing. In step S20, the range of the normalized difference calculated in step S17 belongs to which range of the normalized difference correspondence table, and the distance range corresponding to the normalized difference range in the normalized difference correspondence table. Is estimated as the actual distance range of the barcode to the barcode scanner 100 (step S20). An image diagram of the distance / normalization difference correspondence table obtained from the distance / normalization correspondence table is shown together with step S20 in the flowchart.

  An example of the distance / normalization correspondence table is shown in Table 5 below. Note that this is only an example, and for example, how many centimeters the items are divided and how many levels of the items can be arbitrarily set.

In this example, the following results are obtained. The total range is the 0th to 127th data.
-Total value of the result of frequency analysis of binarized data (binarized amplitude sum): 6.560
Total value of results of frequency analysis of received light intensity waveform itself (sum of amplitude before binarization): 4.929
The ratio of the above difference (normalized difference): 1.631 / 6.560 = 0.2486
-By comparing the normalized difference with Table 3, the distance range of the barcode label 106 with respect to the barcode scanner 100 is found to be 6 to 10 cm.

  As the distance / normalization correspondence table used in step S20, advance measurement is performed for each barcode type, and a distance / normalization difference correspondence table corresponding to each barcode type is prepared. Also good. In this case, the distance / normalized difference correspondence table corresponding to the barcode type is referred to using the barcode type information obtained from the result of decoding in step S18. By doing so, the distance can be determined with higher accuracy since the type of the barcode can be handled.

  Next, the distance corresponding to the “distance range” obtained in the step S20 (for example, the maximum value of the distance range, the average value of the distance range, etc.) is an allowable range of “distance” that should be permitted to be read. It is judged whether it is in (step S21). If the distance corresponding to the “distance range” obtained in the process in step S20 is within the allowable range of “distance” that should be permitted to be read (Yes in step S21), the decoding result in the process in step S18. Is output to the host device (step S22). An allowable range of “distance” that should be permitted to be read is determined in advance according to the function and application of the barcode scanner 100.

  On the other hand, if the decoding in step S18 is not successful (No in step S19), or the comparison in step S21 is performed and the distance corresponding to the “distance range” obtained in the process in step S20 is outside the allowable range. In the case of (No in step S21), the process is terminated and the result is not output. As a result, even if the barcode scanner 106 positioned outside the allowable range is erroneously read, the reading result is not output to the host device. Therefore, in this embodiment, there is an effect that it is not necessary to incorporate a dedicated module for distance measurement, and it is possible to prevent reading of a barcode at an unexpected distance.

  Moreover, although the above-described embodiment is a preferred embodiment of the present invention, the scope of the present invention is not limited only to the above-described embodiment, and various modifications are made without departing from the gist of the present invention. Implementation in the form is possible.

  For example, the processing content of the present embodiment may be used as part of the decoding process of the barcode scanner.

  In addition, in the above description, a one-dimensional barcode is taken as an example as a reading target of the barcode scanner. However, the distance may be measured for a two-dimensional code based on the same idea as described above.

  In addition, the above-described processor of the present embodiment is combined with a barcode scanner further including a focusing mechanism, and the focusing mechanism is controlled so that the sum of amplitudes before binarization of the frequency analysis result is maximized. Thus, the auto focus of the barcode scanner may be realized. If the normalized difference is a value corresponding to a distance outside the allowable range, the autofocus mechanism may be operated until the normalized difference reaches a value corresponding to the distance outside the allowable range.

  In addition, in the above description, the frequency analysis is performed using the sensor light reception intensity of all the pixels acquired by the image sensor. However, the frequency analysis is performed using the sensor light reception intensity of some pixels. Anyway. In the above description, the amplitude sums of all the AC frequencies of the frequency analysis results are compared. However, the amplitude sums of only some AC frequencies may be compared. For example, only high-frequency portions that are considered to be easily different may be compared. By doing so, it is also possible to reduce the amount of arithmetic processing. If such a comparison method is adopted, a distance / normalization correspondence table may be created by the same method.

  The above processor and the barcode scanner including the processor can be realized by hardware, software, or a combination thereof. The distance measurement method performed by the above processor and the barcode scanner including the processor can also be realized by hardware, software, or a combination thereof. Here, “realized by software” means realized by a computer reading and executing a program.

  The program may be stored using various types of non-transitory computer readable media and supplied to the computer. Non-transitory computer readable media include various types of tangible storage media. Examples of non-transitory computer readable media include magnetic recording media (for example, flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (for example, magneto-optical disks), CD-ROMs (Read Only Memory), CD- R, CD-R / W, and semiconductor memory (for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (random access memory)). The program may also be supplied to the computer by various types of transitory computer readable media. Examples of transitory computer readable media include electrical signals, optical signals, and electromagnetic waves. The temporary computer-readable medium can supply the program to the computer via a wired communication path such as an electric wire and an optical fiber, or a wireless communication path.

  A part or all of the above-described embodiment can be described as in the following supplementary notes, but is not limited thereto.

  (Additional remark 1) The result of the 1st frequency analysis with respect to the image data obtained by reading a reading object image with a reading device, and the image data obtained by reading a reading object image at a predetermined distance apart with the reading device A distance detection device that detects a distance between the reading target and the reading device by performing a predetermined process based on the result of the second frequency analysis for the.

(Supplementary note 2) The distance detection device according to supplementary note 1, wherein
Image data obtained by reading a reading target image at a predetermined distance by the reading device is obtained from image data obtained by reading the reading target image by the reading device. Distance detection device.

(Supplementary note 3) The distance detection device according to supplementary note 2,
The image data obtained by reading the reading target image at a predetermined distance by the reading device is obtained by binarizing the image data obtained by reading the reading target image by the reading device. A distance detecting device characterized by being.

(Supplementary note 4) The distance detection device according to any one of supplementary notes 1 to 3,
The predetermined processing is processing based on the amplitude of the AC frequency component obtained from the result of the first frequency analysis and the amplitude of the AC frequency component obtained from the result of the second frequency analysis. A distance detection device.

(Supplementary note 5) The distance detection device according to supplementary note 4, wherein
The processing based on the amplitude of the AC frequency component obtained from the result of the first frequency analysis and the amplitude of the AC frequency component obtained from the result of the second frequency analysis is obtained from the result of the first frequency analysis. The difference between the sum of the amplitudes of one or more AC frequency components and the sum of the amplitudes of the one or more AC frequency components obtained from the result of the second frequency analysis is obtained from the result of the second frequency analysis. The distance is a process using the correspondence between the normalized difference obtained by dividing by the sum of the amplitudes of the above AC frequency components and the distance between the image to be read and the reading device. Detection device.

  (Additional remark 6) The distance detection apparatus of Additional remark 5 characterized by determining the classification of the said reading object, and using the said corresponding relationship of a different content according to a determination result.

  (Supplementary Note 7) Decoding means for decoding data obtained by binarizing the image data in accordance with a rule corresponding to the object to be read, and outputting the decoding result when the detected distance is within a predetermined length range The distance detection device according to any one of appendices 1 to 6, further comprising:

(Supplementary note 8) A reading device including the distance detection device according to any one of supplementary notes 1 to 7,
Means for acquiring the image data by reading the reading object;
Means for supplying the acquired image data to the distance detection device;
A reading apparatus comprising:

  (Additional remark 9) The result of the 1st frequency analysis with respect to the image data obtained by reading a reading object image with a reading apparatus, and the image data obtained by reading a reading object image at a predetermined distance away with the reading apparatus A distance detection method comprising: detecting a distance between the reading target and the reading device by performing a predetermined process based on the result of the second frequency analysis for the above.

  (Additional remark 10) The result of the 1st frequency analysis with respect to the image data obtained by reading a reading object image with a reading apparatus, and the image data obtained by reading a reading object image at a predetermined distance with the reading apparatus The computer is caused to function as a distance detecting device that detects a distance between the reading target and the reading device by performing predetermined processing based on the result of the second frequency analysis for A distance detection program characterized by that.

(Appendix 11) Acquiring the image data by reading the reading target;
Supplying the acquired image data to the distance detection device;
The result of the first frequency analysis for the image data obtained by reading the read target image with the reading device and the second for the image data obtained by reading the read target image with a predetermined distance away by the reading device. And a step of detecting a distance between the reading object and the reading device by performing a predetermined process based on the result of the frequency analysis.

  The present invention is suitable for a barcode scanner, but can be applied to any device as long as it is used for measuring the received light intensity of light reflected from a measurement object.

DESCRIPTION OF SYMBOLS 100 Barcode scanner 101 Processor 101-1 Sensor control part 101-2 Processing part 101-3 Storage part 101-4 Data transmission / reception part 102 Image sensor 103 Condensing lens / filter 104 Reflection mirror 105 Illumination light source 106 Barcode label

According to the first aspect of the present invention, the amplitude of the AC frequency component obtained from the result of the first frequency analysis on the image data obtained by reading the reading target image with the reading device, and the reading target image are read. By performing a predetermined process based on the amplitude of the AC frequency component obtained from the result of the second frequency analysis on the image data obtained by reading at a predetermined distance by the apparatus, the reading object and the reading apparatus are A distance detecting device is provided that detects a distance between the two.

According to the second aspect of the present invention, the amplitude of the AC frequency component obtained from the result of the first frequency analysis on the image data obtained by reading the reading target image with the reading device, and the reading target image are read. By performing a predetermined process based on the amplitude of the AC frequency component obtained from the result of the second frequency analysis on the image data obtained by reading at a predetermined distance by the apparatus, the reading object and the reading apparatus are A distance detection method is provided that detects the distance between the two.

According to the third aspect of the present invention, the amplitude of the AC frequency component obtained from the result of the first frequency analysis on the image data obtained by reading the read target image with the reading device, and the read target image are read. By performing a predetermined process based on the amplitude of the AC frequency component obtained from the result of the second frequency analysis on the image data obtained by reading at a predetermined distance by the apparatus, the reading object and the reading apparatus are There is provided a distance detection program characterized by causing a computer to function as a distance detection device characterized by detecting a distance between the two.

Claims (10)

  The result of the first frequency analysis for the image data obtained by reading the read target image with the reading device and the second for the image data obtained by reading the read target image with a predetermined distance away by the reading device. A distance detection apparatus that detects a distance between the reading object and the reading apparatus by performing predetermined processing based on a result of frequency analysis. The distance detection device according to claim 1,
Image data obtained by reading a reading target image at a predetermined distance by the reading device is obtained from image data obtained by reading the reading target image by the reading device. Distance detection device. The distance detection device according to claim 2,
The image data obtained by reading the reading target image at a predetermined distance by the reading device is obtained by binarizing the image data obtained by reading the reading target image by the reading device. A distance detecting device characterized by being. The distance detection device according to any one of claims 1 to 3,
The predetermined processing is processing based on the amplitude of the AC frequency component obtained from the result of the first frequency analysis and the amplitude of the AC frequency component obtained from the result of the second frequency analysis. A distance detection device. The distance detection device according to claim 4,
The processing based on the amplitude of the AC frequency component obtained from the result of the first frequency analysis and the amplitude of the AC frequency component obtained from the result of the second frequency analysis is obtained from the result of the first frequency analysis. The difference between the sum of the amplitudes of one or more AC frequency components and the sum of the amplitudes of the one or more AC frequency components obtained from the result of the second frequency analysis is obtained from the result of the second frequency analysis. The distance is a process using the correspondence between the normalized difference obtained by dividing by the sum of the amplitudes of the above AC frequency components and the distance between the image to be read and the reading device. Detection device.   The distance detection apparatus according to claim 5, wherein the type of the reading target is determined, and the correspondence relationship having different contents is used according to the determination result.   Decoding means for decoding the binarized data of the image data according to a rule corresponding to the object to be read, and outputting the decoding result when the detected distance is within a predetermined distance length The distance detection apparatus according to claim 1, wherein A reading device comprising the distance detection device according to any one of claims 1 to 7,
Means for acquiring the image data by reading the reading object;
Means for supplying the acquired image data to the distance detection device;
A reading apparatus comprising:   The result of the first frequency analysis for the image data obtained by reading the read target image with the reading device and the second for the image data obtained by reading the read target image with a predetermined distance away by the reading device. A distance detection method comprising: detecting a distance between the reading object and a reading device by performing predetermined processing based on a result of frequency analysis.   The result of the first frequency analysis for the image data obtained by reading the read target image with the reading device and the second for the image data obtained by reading the read target image with a predetermined distance away by the reading device. The computer is caused to function as a distance detecting device that detects a distance between the reading target and the reading device by performing predetermined processing based on a result of the frequency analysis. Distance detection program to do.