JP6266746B2 - Optical information reader - Google Patents

Description

  The present invention relates to a fixed optical information reading device among optical information reading devices that optically read information.

  The optical information reading device includes a handy type optical information reading device in which an operator reads a code by hand, and a fixed optical information reading device that fixes the device and moves an object to which the code is attached. . Two-dimensional code readers (hereinafter referred to as readers) that read two-dimensional codes such as barcodes and QR codes (registered trademark) are widely used. An example of such a reader is described in Patent Document 1. Patent Documents 1 and 2 describe that a polarizing filter is provided in each of the illumination optical system and the imaging optical system.

JP 2011-76519 A Japanese Patent Laid-Open No. 7-282175 Japanese Patent Laid-Open No. 10-187873

  If the reader is downsized, the optical axis of the image sensor and the optical axis of the illumination system must be parallel. This is because the distance between the optical axis of the image sensor and the optical axis of the illumination system must be shortened. In such a reader, the illumination light is reflected on the surface of the workpiece (product to be inspected), and the regular reflection light is incident on the image sensor, making it difficult to read the two-dimensional code. Therefore, the reader must be installed with the optical axis tilted with respect to the normal so that the normal of the workpiece surface does not coincide with the optical axis of the reader. This is called diagonal mounting. Note that attaching the reader so that the normal of the surface of the workpiece and the optical axis of the reader are parallel will be referred to as front attachment. If the surface of the workpiece is substantially flat, the two-dimensional code can be read with high accuracy by inclining the optical axis with respect to the normal by the recommended angle.

  In recent years, two-dimensional codes are also printed on the surface (cast surface) of castings such as engine blocks by laser marking or the like (so-called direct part marking (DPM)). As is well known, since there are fine irregularities on the surface of the casting, the reading accuracy is higher in the front mounting than in the diagonal mounting. Further, since the two-dimensional code such as the surface (milling surface) of the milled workpiece, black resin, or substrate is printed on various parts, an appropriate reading method is different for each part. Therefore, the user has to search for an appropriate installation angle according to each workpiece. In addition, in oblique mounting, an image obtained by reading a two-dimensional code is distorted, which may cause a reading error. Therefore, in the case of front mounting, it is not necessary to search for the installation angle, and the installation burden on the user can be reduced. Further, there is an advantage that the image is not distorted if it is mounted on the front.

  As shown in Patent Documents 1 and 2, by providing a polarizing filter, it is possible to reduce the influence of specularly reflected light even in front mounting. However, if a polarizing filter is provided, it becomes impossible to read a code that is directly part-marked on the casting surface. Although it is conceivable that the polarizing filter can be removed, a new labor is required for removal.

  As described above, there is a demand from the market to reduce a user's installation burden on a reader that reads various workpieces. SUMMARY OF THE INVENTION An object of the present invention is to provide an optical information reading apparatus that can reduce a user's installation burden and can accurately read codes attached to various workpieces.

According to the present invention, for example,
A fixed code reader for reading a code provided on a workpiece,
A first illuminating means for illuminating the work and irradiating the work with illumination light through the first polarizing filter;
A second illuminating means for illuminating the work and irradiating the work with illumination light without using a polarizing filter;
As a lighting mode, a polarization mode in which the first illumination means is turned on and the second illumination means is not turned on, and a non-polarization mode in which the first illumination means is not turned on and the second illumination means is turned on. Illumination control means for controlling the first illumination means and the second illumination means according to a set illumination mode;
A second polarizing filter having a polarization direction different from the polarization direction of the first polarizing filter is provided, and the light irradiated by at least one of the first illuminating means and the second illuminating means is reflected by the workpiece. Imaging means for receiving light through the second polarizing filter and imaging a code provided on the workpiece;
Imaging control means for controlling imaging conditions relating to the imaging means;
An indicator indicating the readability of the code based on a plurality of image data obtained from the workpiece for each of a plurality of imaging conditions and illuminated by the polarization mode, and a plurality of illuminations by the non-polarization mode Setting means for setting an illumination mode in which a good index is obtained among the indices indicating the readability of the code based on a plurality of image data acquired from the workpiece for each of the imaging conditions in the illumination control means When,
Decoding means for decoding image data acquired by imaging the workpiece illuminated according to the illumination mode set by the setting means by the imaging means;
A code reader is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the optical information reader which can reduce the installation burden of a user and can read the code provided to various workpiece | work accurately is provided.

The figure which shows an optical information reader The figure which shows the structure of an optical information reader The figure which shows the support structure of an image display apparatus The figure which shows the display and operation panel of an optical information reader The figure which shows the electrical structure of an optical information reader. The figure which shows the computer connected to an optical information reader The figure which shows an example of the shape of a polarizing filter The figure which shows an example of the shape of a polarizing filter Flowchart diagram showing tuning of reading conditions Flow chart showing coarse adjustment of brightness level The figure which shows an example of the search range of the brightness level about each illumination mode

  An embodiment of the present invention is shown below. The individual embodiments described below will help to understand various concepts, such as the superordinate concept, intermediate concept and subordinate concept of the present invention. Further, the technical scope of the present invention is determined by the scope of the claims, and is not limited by the following individual embodiments.

  FIG. 1 is a diagram showing an example of a reader system (optical information reader). A line 1 is a conveyance belt that conveys a workpiece 2 that is an inspection object. The reader 3 is a two-dimensional code reader that reads and decodes a two-dimensional code. Note that the reader 3 itself is an optical information reading device in a narrow sense. The programmable logic controller (PLC 5) is a control device that controls the line 1 and the reader 3. The computer 4 is an information processing apparatus that sets operating conditions and the like for the reader 3 and acquires and displays a decoding result from the reader 3.

<Structure of reader 3>
2A is a perspective view of the reader 3, and FIG. 2B is a development view of main components. Since the shape of the reader 3 is a substantially rectangular parallelepiped, the outer surface of the housing has approximately six surfaces. As shown in FIG. 2B, the front case 10 is provided with four openings. The opening on the top surface side is provided with a holder 13, an image display device 14 supported by the holder 13, a display panel 15 arranged so as to cover the image display device 14, and a main sheet 16. An opening on the front side of the front case 10 is provided with a light-transmitting window 11 and a front cover 12. In particular, in this embodiment, a polarizing filter is provided in a part of the window portion 11. The reflector 17 and the illumination board 18 are inserted from the opening on the back side of the front case 10 and are covered by the rear case 19. The rear case 19 is provided with a main board 21, an optical system 50 fixed to the main board 21, and an AF mechanism 51. The reflector 17 is a structural component for efficiently irradiating the light from the light emitting element provided on the illumination substrate 18 forward. The reflector 17 has cone-shaped condensing units 176 to 179 for condensing and irradiating the light from the light emitting element for illumination forward, and the light from the light emitting element for the pointer forward. A cone-shaped condensing part 175 for condensing and irradiating is provided. These are plated with gold or the like to increase the light collection efficiency. A connector holder 20 is attached to the opening on the lower surface side of the front case 10. Two communication cables are connected to the connector holder 20, and are connected to the computer 4 and the PLC 5, respectively. A connector substrate is attached to the connector holder 20.

  FIGS. 3A to 3C are views for explaining the structure around the holder 13. As shown in FIGS. 3A and 3B, the holder 13 is a support member that supports the image display device 14. The illumination board 18 extends in a direction perpendicular to the holder 13 and engages the holder 13 to support the holder 13. That is, the holder 13 is provided in parallel with the upper surface of the front case 10, and the illumination board 18 is provided in parallel with the front surface of the front case 10, and both are orthogonal to each other. Note that a groove 131 is provided on the lower surface side of the holder 13, and the holder 13 may be firmly fixed to the illumination board 18 by fitting the end of the illumination board 18 in the groove 131. By adopting such a holder 13, a circuit board to which the image display device 14 is attached can be eliminated.

  As shown in FIGS. 3A and 3C, the illumination board 18 is provided with push button type switches 24 and 25 having a pressing surface on the same side as the display surface of the image display device 14. May be. The switches 24 and 25 may be pressed by the pressing members 22 and 23 formed integrally with the holder 13 so that the respective contacts are closed. Since the pressing direction of the switches 24 and 25 coincides with the length direction of the illumination board 18 indicating the holder 13, the holder 13 is not easily bent even when the switches 24 and 25 are pressed. The pressing member 22 is supported by an elastic arm portion 39 a extending from the main body of the holder 13. Similarly, the pressing member 23 is supported by an elastic arm portion 39 b extending from the main body of the holder 13. The pressed pressing members 22 and 23 are returned to their original positions by the elasticity of the arm portions 39a and 39b. Since the arm portions 39a and 39b are integrally formed with the holder 13, there is an advantage that an additional member for return such as a spring can be omitted.

  As shown in FIGS. 3A and 3B, the illumination substrate 18 has a circular shape for mounting an optical system module (such as the optical system 50 and the AF mechanism 51) provided corresponding to the imaging element 31. The opening 33 is provided. Around the opening 33, four light emitting elements 26 to 29 for illumination are provided. As shown in FIG. 3A, one or a plurality of light emitting elements 32 functioning as indicators are provided in the vicinity of the engaging portion between the illumination board 18 and the holder 13. A light guide opening 34 is provided in the holder 13 so that light from the light emitting element 32 is output to the outside from the upper surface of the front case 10. That is, an indicator is disposed between the two switches 24 and 25. As shown in FIG. 3C, since the four sides of the opening 34 are surrounded by the light shielding walls 36a to 36d, the light from the indicator is less likely to leak toward the image display device 14. The holder 13 is provided with an accommodation groove 37 for accommodating the image display device 14. Further, a hole 38 for passing a signal cable of the image display device 14 is provided at the bottom of the accommodation groove 37.

  As shown in FIG. 3B, an image sensor 31 is arranged on the main board 21. As shown in FIG. 3B, the illumination board 18 is provided with a light emitting element 35 that outputs pointer light. As described above, the reflector 17 is provided with the light collecting portions 176 to 179 for the light emitting elements 26 to 29 in addition to the light collecting portion 175 for the light emitting element 35. The condensing parts 175 to 179 have a cone shape, and light enters from the opening on the top side of the cone and exits from the bottom side.

  FIG. 4 is a view showing the main seat 16. A display surface 40 of the image display device 14 is provided at the center of the main sheet 16. A select key 42, an indicator 44, and an enter key 43 are provided below the main sheet 16. The select key 42 includes the switch 24 and the pressing member 22 described above. The enter key 43 includes the switch 25 and the pressing member 23 described above. The indicator 44 is composed of two light emitting elements 32. For example, when the two-dimensional code is successfully read, the green light-emitting element is turned on, and when the two-dimensional code reading is unsuccessful, the red light-emitting element is turned on. In addition to the image (still image or moving image) acquired by the image pickup device 31, the image display device 14 displays an image (SEL and MENU in FIG. May be displayed))).

<Control unit>
FIG. 5 is a block diagram showing an electronic configuration of the reader 3. The camera unit (imaging unit) of the reader 3 includes an imaging element 31, an optical system 50, an AF mechanism 51, an illumination unit 52, and the like. The image sensor 31 is an image sensor such as a CCD or CMOS that converts an image of a two-dimensional code formed through the optical system 50 into an electrical signal. The AF mechanism 51 is a mechanism that adjusts the position and refractive index of the focusing lens in the optical system 50. The AF mechanism 51 and the optical system 50 are disposed between the image sensor 31 and the opening 33 in FIG. The AF mechanism 51 and the optical system 50 may be integrated to form an optical system module.

  The illumination unit 52 has one or more light emitting elements and is a unit that illuminates a two-dimensional code. The illumination part 52 has the light emitting elements 26-29 for illumination and the light emitting element 35 for pointers, for example. The light from the pointer serves as a guide for the optical axis of the optical system 50, and the user may refer to the position of the pointer and place the workpiece 2 at the correct position.

  The decoding unit 53 is a unit that decodes the image data 72 of the two-dimensional code acquired by the image sensor 31 and writes the decoding result 71 in the storage unit 70. The communication unit 54 is a unit that communicates with the PLC 5 and the computer 4. The communication unit 54 may include, for example, an I / O unit that communicates with the PLC 5, a serial communication unit such as RS232C, a network communication unit such as a wireless LAN or a wired LAN, and the like.

  The display unit 55 includes the image display device 14 and the indicator light emitting element 32. The display unit 55 includes, for example, a character string that is the decoding result 71 of the two-dimensional code, a reading success rate (average reading success rate when the reading process is executed a plurality of times), and a matching level (reading margin indicating ease of reading). Degree), PPC (a value indicating how many pixels a single cell constituting the two-dimensional code corresponds to: pixel per cell), and the like may be displayed. The input unit 56 is a unit that accepts an input operation such as a switch, and includes a select key 42 and an enter key 43.

  The control unit 60 is a unit that comprehensively controls each unit of the reader 3. Although the control unit 60 has various functions, these may be realized by a logic circuit or by executing software. An autofocus control unit (AF control unit) 61 is a unit that controls the AF mechanism 51. The imaging control unit 62 is a unit that controls the amount of illumination light of the illumination unit 52 and controls the exposure time (shutter speed) of the imaging device 31. In particular, the imaging control unit 62 functions as a lighting control unit that controls which of the plurality of light emitting elements of the lighting unit 52 is turned on in response to an instruction from the tuning unit 65 or the calculation unit 63.

  The calculation unit 63 executes various calculation processes. For example, the calculation unit 63 calculates a reading success rate, a matching level, and a PPC by using a decoding result and image data. Of course, these calculations may be executed by units other than the calculation unit 63 such as the decoding unit 53 and the tuning unit 65.

  The tuning unit 65 functions as a reading condition control unit that controls reading conditions or a condition determination unit that determines illumination conditions. The reading conditions are, for example, imaging conditions such as exposure time, illumination light quantity, gain, and image processing conditions (such as filter coefficients) in the decoding unit 53. Appropriate imaging conditions and image processing conditions change due to the influence of external light on the workpiece 2 conveyed on the line 1. Therefore, the tuning unit 65 searches for a more appropriate reading condition and sets the AF control unit 61, the imaging control unit 62, and the decoding unit 53.

  The UI management unit 66 is a unit that displays image data on the image display device 14, receives a user instruction from the input unit 56, and controls lighting of the indicator.

  The storage unit 70 is a storage device such as a memory. The decoding result 71 acquired by the decoding unit 53, the image data 72 acquired by the image sensor 31, the data set in the reader 3 by the setting device such as the computer 4, The setting data 73 that is data set by the input unit 56 is stored.

  FIG. 6 is a block diagram showing functions of the computer 4. If the size of the reader 3 is reduced, it becomes difficult to set all the functions of the reader 3 with only the display unit 55 and the input unit 56 of the reader 3. Therefore, some setting data 73 may be created by the computer 4 and transferred to the reader 3. The CPU 80 is a unit that controls each unit included in the computer 4 based on a program stored in the storage unit 90. The UI control unit 83, which is a function of the calculation unit 81, outputs the user interface for setting the imaging conditions of the reader 3 (in particular, whether or not to use a light emitting element with a polarizing filter) and the reader 3 outputs. A user interface for displaying the decoding result 71, the image data 72, and the like is generated and displayed on the display unit 84. The calculation unit 81 is a unit that executes various calculations. The communication unit 86 is wired or wirelessly connected to the communication unit 54 of the reader 3 and receives the decoding result 71 and the image data 72 and transmits the setting data 73 generated by the setting unit 82. The storage unit 90 is a memory, a hard disk drive (HDD), a solid state drive (SSD), or the like.

<Illumination mode (polarization mode and non-polarization mode)>
In this embodiment, in order to reduce the user's installation burden and to be able to accurately read codes attached to various workpieces, a plurality of illumination means are provided, and a polarizing filter is arranged in the first illumination means. The polarizing filter is not disposed in the second illumination means. And a 1st illumination means and a 2nd illumination means are used properly according to a workpiece | work. As a result, the user can save the trouble of adjusting the installation angle of the reader 3 for each workpiece.

  As described above, when the reader 3 is attached to the work 2 in front, a large amount of specularly reflected light from the work 2 is likely to enter the image sensor 31. This is likely to occur when the installation surface of the two-dimensional code on the workpiece 2 is a smooth surface, and causes a failure in decoding the two-dimensional code. As a means for reducing specular reflection light, it is conceivable to arrange polarizing filters having different polarization directions in the image sensor 31 and the illumination unit 52, respectively. However, if the entire illumination unit 52 is covered with a polarizing filter, the two-dimensional code marked with direct parts on the surface of the casting cannot be read with high accuracy. That is, the reading accuracy of the two-dimensional code printed on the casting surface is higher when the illumination unit 52 is not provided with a polarizing filter. Thus, depending on the surface of the work 2 and the method of applying the two-dimensional code, it is appropriate to provide a polarizing filter or not to provide a polarizing filter. When a polarizing filter is provided, the light amount is attenuated to ½ by the light-emitting side polarizing filter, and the light amount is further attenuated to ½ by the light-receiving side polarizing filter. That is, the total amount of light is attenuated to ¼. When the amount of light is attenuated, reading of the two-dimensional code tends to fail. Increasing the amount of light emitted from the light emitting element to compensate for the attenuation will not only increase power consumption but also increase heat. These can be disadvantages.

  As a method of dealing with various workpieces 2 with one reader 3, it is conceivable to employ a detachable polarizing filter that covers the emission regions of all the light emitting elements. However, in this case, it is necessary for the user to determine whether to install or remove the polarizing filter, and to attach and remove the polarizing filter manually. That is, it is not necessary for the user to adjust the installation angle, but instead, a polarizing filter installation / removal operation is required.

  Therefore, in the present embodiment, a reader 3 is proposed in which a first illuminating unit provided with a polarizing filter and a second illuminating unit not provided with a polarizing filter are provided, and these are switched according to the work 2 and used. .

  FIG. 7A is a perspective view of the reader 3, and FIG. 7B is an enlarged view of the window portion 11. In the window portion 11, a polarizing filter 91 is provided in a portion where the light of the light emitting element 26 emits (light emission region) and a portion where the light of the light emitting element 27 emits. In addition, a polarizing filter 92 is provided in a portion (light incident region) where light enters the optical system of the image sensor 31 in the window portion 11. Note that the polarization direction of the polarization filter 91 and the deflection direction of the polarization filter 92 are different, for example, 90 degrees. On the other hand, a polarizing filter is not provided in a portion of the window portion 11 where the light from the light emitting element 28 is emitted and a portion where the light from the light emitting element 29 is emitted. As described above, the light emitting element 26 and the light emitting element 27 may form the first illumination unit, and the light emitting element 28 and the light emitting element 29 may form the second illumination unit. That is, instead of the user performing installation or removal of the polarization filter, it is only necessary to electrically switch which illumination means the reader 3 turns on. For example, for a work (for example, casting) which is more advantageous without a polarizing filter, the second illumination unit is turned on and the first illumination unit is turned off. On the other hand, for a work that is more advantageous with a polarizing filter (for example, a work having a two-dimensional code on a printed circuit board, a milled surface, a black resin, etc.), the first illumination means is turned on, and the second illumination means is used. Turn off the light. As a result, the burden on the user can be greatly reduced, and two-dimensional codes provided on various workpieces can be accurately read with one reader 3.

  FIG. 8A shows an example of the shape of the polarizing filter 91 and the polarizing filter 92. In particular, the polarizing filter 92 for the image sensor has a substantially circular shape, and alignment members 93 a and 93 b are provided on the left end and the right end of the polarizing filter 92, respectively. The left end and the right end of the bottom of the polarizing filter 91 are aligned with the shapes of the alignment members 93a and 93b, and in this example, are linear. The center of the bottom of the polarizing filter 91 is substantially semicircular and matches the shape of the upper part of the polarizing filter 92. As described above, by using the alignment members 93a and 93b, the polarizing filter 91 and the polarizing filter 92 are easily attached to the window portion 11 accurately. Moreover, since the shape of the top part of the polarizing filter 91 is matched with the shape of the top part of the window part 11, it is easy to attach the polarizing filter 91 with respect to the window part 11 accurately.

<Switching whether or not a polarizing filter is used>
A method for switching between the polarization mode and the non-polarization mode will be described with reference to FIGS. FIG. 9 is a flowchart showing each step of the tuning process. When tuning is instructed from the input unit 56 or tuning is instructed from the computer 4, the tuning unit 65 executes the following steps.

  In step S901, the tuning unit 65 performs code search. For example, the tuning unit 65 causes the imaging control unit 62 to perform imaging to acquire image data, and causes the decoding unit 53 to search for a two-dimensional code based on the image data. The imaging control unit 62 reads out reading conditions (imaging conditions for the imaging device 31, illumination conditions for the illumination unit 52, image processing conditions for the decoding unit 53, etc.) that are valid at that time from the setting data 73, and the illumination unit 52, the image pickup device 31, the decoding unit 53, and the like. The decoding unit 53 searches for the two-dimensional code from the image data 72 of the two-dimensional code acquired by the image sensor 31 and outputs the search result to the tuning unit 65. The illumination condition includes information indicating whether the polarization mode is enabled or the non-polarization mode is enabled.

  In step S <b> 902, the tuning unit 65 performs rough adjustment on the brightness of the illumination unit 52. FIG. 10 is a flowchart showing in detail the coarse brightness adjustment in S902. In the present embodiment, it is assumed that coarse adjustment is performed on the brightness, the better reading result is selected from the polarization mode and the non-polarization mode, and the fine adjustment of the brightness is performed on the selected illumination mode.

  In S921, the tuning unit 65 switches to an illumination mode different from the illumination mode set in the illumination unit 52 at that time. In other words, the tuning unit 65 switches to the non-polarization mode if the polarization mode is set in the illumination unit 52, and switches to the polarization mode if the non-polarization mode is set.

  In S922, the tuning unit 65 executes a reading test. For example, the tuning unit 65 causes the imaging control unit 62 to perform imaging, and causes the decoding unit 53 to search for a two-dimensional code. Of the reading conditions that are valid at that time, only the illumination mode is changed. The decoding unit 53 searches the two-dimensional code for the image data 72 of the two-dimensional code acquired by the image sensor 31 and outputs the search result to the tuning unit 65.

  In S923, the tuning unit 65 determines whether the reading test is successful based on the search result from the tuning unit 65. When the reading test is executed a plurality of times while changing the reading conditions, it is determined whether or not the reading is successful even once. If the reading test is successful, it means that the two-dimensional code can be decoded in both the polarization mode and the non-polarization mode. Therefore, the process proceeds to S924.

  In S924, the tuning unit 65 executes a reading test for each of n (eg, 27) brightness levels out of N (eg, 256) for each illumination mode. As a result, a reading result for each of the 27 brightness levels is obtained for the polarization mode, and a reading result for each of the 27 brightness levels is obtained for the non-polarization mode. As shown in FIG. 11, the brightness level to be tuned may be different between the polarization mode and the non-polarization mode. As described above, the brightness of the polarization mode is half that of the non-polarization mode. Therefore, N / 2 levels or more out of N may be assigned to the brightness level in the polarization mode, and less than N / 2 levels out of N may be assigned to the brightness level in the non-polarization mode. As a result, the time required for the reading test can be reduced by half compared to a case where all N levels are searched exhaustively. Of course, if there is no request for time reduction, all N levels may be exhaustively searched in each illumination mode.

  In S925, the tuning unit 65 determines an illumination mode with a better decoding result among the plurality of illumination modes. For example, the tuning unit 65 compares the number of successful reading tests in each illumination mode, and determines a more successful illumination mode. For example, if 27 reading tests are successful in the polarization mode and 10 reading tests are successful in the non-polarization mode, the polarization mode is selected. If the number of successful polarization modes is the same as the number of successful non-polarization modes, or if there is no significant difference between the two, the tuning unit 65 may select the non-polarization mode. This is because the non-polarization mode is more advantageous in terms of power consumption and heat when realizing the same brightness. However, in an environment where disturbance light or the like is likely to be generated, the polarization mode can cut a part of the disturbance light with the deflection filter, so that the reading success rate is increased. Therefore, in such a case, the polarization mode may be preferentially adopted. Although the number of successful reading tests is compared here, the tuning unit 65 may compare the reading success rates, or may calculate and compare a matching level indicating the readability.

  In S926, the tuning unit 65 determines the result of coarse brightness adjustment. For example, assume that the brightness level can be changed from 0 to 255. Among them, in S924, a reading test is executed for n levels. Then, the tuning unit 65 calculates a level (eg, average value) that is the center of the m levels that have been successfully read. In this way, rough brightness adjustment is performed.

  By the way, if the reading test is not successful once in the other illumination mode in S923, the tuning unit 65 omits or cancels the reading condition search process in the other illumination mode, and selects the original illumination mode. The process proceeds to S927. In S927, the tuning unit 65 performs a reading test for each of n (eg, 27) brightness levels for the original illumination mode. As a result, a reading result for each of the 27 brightnesses is obtained for the polarization mode or the non-polarization mode which is the original illumination mode. Thereafter, the process proceeds to S926, and the tuning unit 65 calculates a level (eg, average value) that is the center of the m levels that have been successfully read.

  When the coarse adjustment is completed, the fine adjustment of S903 is executed. In step S903, the tuning unit 65 varies the brightness around the brightness level determined by the coarse adjustment, and searches for and determines the brightness level with the highest reading success rate or matching level.

  In S904, the tuning unit 65 executes the reading test again. In S905, the tuning unit 65 determines whether the reading success rate or the number of successes exceeds a threshold value. If the reading success rate or the number of successes exceeds the threshold value, the tuning unit 65 ends the tuning process. On the other hand, if the reading success rate or the number of successes does not exceed the threshold, the process proceeds to S906. In S906, the tuning unit 65 changes reading conditions other than brightness (eg, exposure time, gain, image processing filter coefficient, etc.), and returns to S901.

<Summary>
In the present embodiment, as described with reference to FIG. 3B and FIG. 7, the light emitting elements 26 and 27 that irradiate the work 2 with illumination light through the polarizing filter 91 as illumination means for illuminating the work 2, Light emitting elements 28 and 29 for irradiating the work 2 with illumination light without using a polarizing filter are provided. The imaging element 31 is provided with a polarization filter 92 having a polarization direction different from the polarization direction of the polarization filter 91 of the light emitting elements 26 and 27. The imaging element 31 receives light from the work 2 illuminated by at least one of the light emitting elements 26 and 27 and the light emitting elements 28 and 29 via the polarizing filter 92 and images a code provided on the work 2. . The decoding unit 53 decodes the image data acquired by the image sensor 31. As described above, in the present embodiment, since the light source for polarization and the light source for non-polarization are provided, it is possible to selectively select one of the light sources. In particular, by using a polarizing filter, the influence of specular reflection light can be reduced, and the front mounting of the reader 3 is allowed. Therefore, the installation burden on the user is reduced. In addition, since the polarized light source and the non-polarized light source can be selectively used according to the workpiece 2, the reader 3 capable of accurately reading the code attached to the workpiece 2 is realized. For example, for a work 2 that is easily regularly reflected, such as a printed circuit board, a polarization mode in which only a light source for polarization is turned on may be advantageous. On the other hand, a non-polarization mode in which only a light source for non-polarization is turned on is advantageous for a code that is directly marked on a casting. In the present embodiment, the explanation has focused on selectively turning on the light source for polarization and the light source for non-polarization (not turning on both at the same time). Alternatively, the imaging control unit 62 may turn on both at the same time.

  As described with reference to FIGS. 9 and 10, the tuning unit 65 turns on the light emitting elements 26 and 27 for polarization and decodes the decoding unit 53 acquired without turning on the light emitting elements 28 and 29. Based on whether the decoding result of the decoding unit 53 obtained by lighting the non-polarization light emitting elements 28 and 29 without lighting the light emitting elements 26 and 27 is a better decoding result, Lighting conditions may be determined. Depending on the work 2, which of the polarization mode and the non-polarization mode is advantageous varies. Therefore, the reading success rate will be improved by actually performing a reading test and selecting an illumination mode that has obtained better results. As the decoding result, a matching level that is an index indicating the ease of reading the code, the number of successful decoding of the code, or the like may be employed. Since there are only two reading results, success or failure, each time, the superiority or inferiority cannot be determined. Therefore, by using the matching level and the number of successes obtained by executing a plurality of readings as a criterion for determination, an illumination mode that is advantageous for each workpiece can be easily determined.

  Note that there may be no significant difference between the polarization mode decoding result and the non-polarization mode decoding result. In such a case, a polarization mode may be adopted. Since the polarization mode reduces disturbance light with a deflection filter, it may be advantageous in factories with a lot of disturbance light.

  Further, when decoding is successful in both the polarization mode and the non-polarization mode, the non-polarization mode may be employed. By adopting the non-polarization mode, there is an advantage that the power consumption in the light emitting element can be reduced and the heat radiation amount can be reduced. In particular, power consumption and the like may be important in an environment with little disturbance light. Therefore, in such a case, it is desirable to adopt the non-polarization mode.

  As described above, the tuning unit 65 controls the reading conditions including the imaging conditions of the imaging element 31 and the image processing conditions in the decoding unit 53. The tuning unit 65 may start searching for the reading condition after the illumination condition is determined. That is, after first determining whether the mode is the non-polarization mode or the polarization mode, the exposure time and gain as the reading conditions, the coefficient of the image processing filter, and the like may be adjusted to be more appropriate. In the process for determining the illumination mode and the process for determining the reading condition, the latter tends to be a huge work. For example, if the reading condition adjustment process is executed for each illumination mode, the overall amount of work becomes very large. Therefore, by determining the illumination mode and then executing the reading condition adjustment process, the overall amount of work can be greatly reduced.

  As described with reference to FIGS. 9 and 10, the tuning unit 65 turns on the light emitting elements 26 and 27 and turns on the light emitting elements 26 and 27 and the polarization mode in which the light emitting elements 28 and 29 are not turned on. In addition, the brightness parameter of the reading conditions is roughly adjusted for each of the non-polarization modes in which the light emitting elements 28 and 29 are turned on, and the decoding succeeds more in both the polarization mode and the non-polarization mode. The brightness parameter may be further finely adjusted for a mode that has succeeded in decoding among the polarization mode and the non-polarization mode. Thereby, it becomes possible to determine an illumination mode and a brightness parameter efficiently.

  In the coarse adjustment, the tuning unit 65 performs a code search process for searching for a code from image data in one of the polarization mode and the non-polarization mode, and when a code is found by the code search process, Switch to the other mode and the non-polarized mode and execute the code search process again. If no code is found in the other mode, stop adjusting the reading conditions in the other mode and read in one mode. Condition adjustment may be performed. As described above, when there is little chance of correct reading in the other mode, the time required for the rough adjustment can be greatly shortened by omitting the adjustment in the other mode.

  As described with reference to FIG. 11, the search range of the brightness parameter may be different between the polarization mode and the non-polarization mode. The polarization mode and the non-polarization mode have the property that the brightness is exactly two times different. Therefore, the start level of the search range for the polarization mode may be set to twice the start level of the search range for the non-polarization mode. Similarly, the end level of the search range for the polarization mode may be set to twice the end level of the search range for the non-polarization mode. As a result, the search time can be reduced by about half compared to the case of exhaustively searching for the brightness level in each illumination mode.

  As described with reference to FIGS. 2A and 2B, the connector holder 20 functions as a connection means for connecting a communication cable for outputting the decoding result to the outside. The light emitting elements 26 and 27 are disposed farther from the light receiving part of the image sensor 31 as viewed from the connector holder 20, and the light emitting elements 28 and 29 are disposed closer to the light receiving part of the image sensor 31 from the connector holder 20. May be.

  As described with reference to FIG. 2B, the window portion 11 is disposed as a translucent plate in the housing on the light emission surface side of the light emitting elements 26 and 27 and the light emitting elements 28 and 29. Further, as described with reference to FIGS. 7 and 8, the polarizing filter 91 is attached to a partial region of the window portion 11 and a region through which light from the light emitting elements 26 and 27 is transmitted. In addition, an incident area of light to the image pickup device 31 is provided at substantially the center of the translucent plate that is the window portion 11, and the light emission area of the light source for polarization and the light from the non-polarized light source are disposed around the incident area May be arranged. Further, the number of light-emitting elements that constitute the light source for polarization may coincide with the number of light-emitting elements that constitute the light source for non-polarization. This is because the light emitting elements can be arranged in a balanced manner around the optical axis of the image sensor 31. Since the amount of light is halved when the polarizing filter 91 is attached, the number of light-emitting elements that constitute the light source for polarization may be double the number of light-emitting elements that constitute the light source for non-polarization. As a result, the light amounts of the respective light sources can be made substantially equal.

  As described above, the polarization direction of the polarization filters of the light emitting elements 26 and 27 and the deflection direction of the polarization filter of the imaging element 31 are different by 90 degrees. This is efficient in efficiently attenuating regular reflection light. Note that it is not necessary to be completely 90 degrees, and some tolerance is naturally allowed.

  As described with reference to FIG. 8, the shape of the polarizing filter 92 of the image sensor 31 is substantially circular. Although it is possible to make the shape of the polarizing filter 92 rectangular, since the shape of the lens of the optical system is circular, it is easy to reduce the size of the reader 3 by making the shape of the polarizing filter 92 circular. right. Alignment members 93a and 93b may extend from the left end and the right end of the polarizing filter 92, respectively. As a result, alignment when attaching the polarizing filter 92 to the window portion 11 will be facilitated. The shape of the polarizing filter 92 including the alignment members 93a and 93b may be symmetrical. In addition, it is not necessary to provide a polarizing filter in the light emission region of the pointer light emitting element 35. This is because the intensity of the reflected light from the pointer light emitting element 35 is preferably higher.

  The tuning unit 65 may select either the polarization mode or the non-polarization mode according to setting information received from a control device provided outside the reader 3 such as the computer 4 or the PLC 5. In this way, the illumination mode may be forcibly set and fixed from the computer 4 or the PLC 5. Thereby, it will be possible to fix the lighting mode according to the user's convenience.

  The plurality of light emitting elements 26 and 27 constituting the first illuminating means are arranged along the carrying direction of the two-dimensional code, and the plurality of light emitting elements 28 and 19 constituting the second illuminating means are also arranged along the carrying direction. It was explained as being. However, the combination of the first illumination means and the second illumination means may be changed. For example, the first illuminating means may be composed of the light emitting elements 28 and 29, and the second illuminating means may be composed of the light emitting elements 26 and 27. Alternatively, the first illumination means may be constituted by the light emitting elements 26 and 28, and the second illumination means may be constituted by the light emitting elements 27 and 29. Similarly, the first illuminating means may be composed of the light emitting elements 27 and 29, and the second illuminating means may be composed of the light emitting elements 26 and 28. The first illumination means may be constituted by the light emitting elements 26 and 29, and the second illumination means may be constituted by the light emitting elements 27 and 28. Further, the first illuminating means may be composed of the light emitting elements 27 and 28, and the second illuminating means may be composed of the light emitting elements 26 and 29.

  Since the first illumination means is provided with a polarizing filter, the amount of light is reduced compared to the second illumination means. Therefore, the number of light emitting elements constituting the first illuminating means may be larger than the number of light emitting elements constituting the second illuminating means. Similarly, a light emitting element with a large maximum amount of light may be adopted as the light emitting element constituting the first illumination unit, and a light emitting element with a small maximum amount of light may be adopted as the light emitting element constituting the second illumination unit. As a result, it will be possible to compensate for a decrease in the amount of light due to the polarizing filter.

  Although the polarizing filters 91 and 92 have been described on the premise that they are fixed to the window portion 11, they may be detachable polarizing filters.

  A plurality of combinations (banks) may be prepared in advance as reading conditions to be tuned. The tuning unit 65 may determine an appropriate bank for each work by switching banks and executing a reading test. This bank includes setting information indicating which of the polarization mode and the non-polarization mode described above is adopted.

  As described with reference to FIG. 2B and the like, the reflector 17 that is a condensing member may be employed in at least one of the optical system, the first illumination unit, and the second illumination unit of the image sensor 31. The condensing member for the image sensor in the reflector 17 may be a condensing member having a circular cross-sectional shape parallel to the imaging surface of the image sensor 31. That is, a cone-type or truncated cone-type light collecting member may be employed. Similar light condensing members may be employed for the light emitting elements 26 to 29. In particular, if a polarizing filter is used, the amount of light decreases, so the condensing member will compensate for the decrease in the amount of light.

  1 ... line, 2 ... work, 3 ... lighting device, 4 ... camera, 5 ... image processing device, 6 ... input unit, 7 ... display unit

Claims (7)

  A fixed code reader for reading a code provided on a workpiece,
  A first illuminating means for illuminating the work and irradiating the work with illumination light through the first polarizing filter;
  A second illuminating means for illuminating the work and irradiating the work with illumination light without using a polarizing filter;
  As a lighting mode, a polarization mode in which the first illumination means is turned on and the second illumination means is not turned on, and a non-polarization mode in which the first illumination means is not turned on and the second illumination means is turned on. Illumination control means for controlling the first illumination means and the second illumination means according to a set illumination mode;
  A second polarizing filter having a polarization direction different from the polarization direction of the first polarizing filter is provided, and the light irradiated by at least one of the first illuminating means and the second illuminating means is reflected by the workpiece. Imaging means for receiving light through the second polarizing filter and imaging a code provided on the workpiece;
  Imaging control means for controlling imaging conditions relating to the imaging means;
  An indicator indicating the readability of the code based on a plurality of image data obtained from the workpiece for each of a plurality of imaging conditions and illuminated by the polarization mode, and a plurality of illuminations by the non-polarization mode Setting means for setting an illumination mode in which a good index is obtained among the indices indicating the readability of the code based on a plurality of image data acquired from the workpiece for each of the imaging conditions in the illumination control means When,
  Decoding means for decoding image data acquired by imaging the workpiece illuminated according to the illumination mode set by the setting means by the imaging means;
A code reading device comprising:   The code reading apparatus according to claim 1, wherein the setting unit sets the imaging condition based on an index indicating the readability of the code.   The code reading device according to claim 1, wherein the setting unit finely adjusts the imaging condition after setting an illumination mode in which the good index is obtained in the illumination control unit.   A search range of imaging conditions searched for setting the illumination mode, wherein a search range of imaging conditions for the polarization mode is different from a search range of imaging conditions for the non-polarization mode. The code reader according to any one of claims 1 to 3, wherein   The imaging condition is any one of a brightness level of the first illumination unit, a brightness level of the second illumination unit, a gain of the imaging unit, and an exposure time of the imaging unit. Item 5. The code reading device according to any one of Items 1 to 4.   6. The code reading apparatus according to claim 1, wherein the number of light emitting elements included in the first illumination unit is greater than the number of light emitting elements included in the second illumination unit.   The code reading apparatus according to claim 1, wherein the index indicating the readability of the code is a probability of successful reading of the code or a matching level for the code.