JP6358888B2 - Optical information reading apparatus, optical information reading method and program - Google Patents

Description

  The present invention relates to an optical information reading apparatus, an optical information reading method, and a program for optically reading information.

  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.

JP 2011-76519 A

  In order to read a two-dimensional code of a workpiece conveyed on the production line, a reader may be installed on the production line. In this case, there are a method in which the work is transported by the transport belt, the transport belt is stopped at the reader and reading is performed, and a method in which reading is performed while the work is transported by the transport belt. Since the former can increase the exposure time, the reading success rate is improved, but the number of readings per unit time is reduced. The latter has the advantage that the number of readings per unit time can be increased, but since the exposure time cannot be increased, the reading success rate is reduced. If the conveyance speed is up to a certain level, the shooting blur of the read image of the two-dimensional code is small. Therefore, the reader will succeed in decoding by performing error correction on the reading result of the two-dimensional code. However, conventionally, in order to obtain the fastest conveyance speed at which a desired reading success rate can be achieved, the user has to perform a workpiece reading test while gradually increasing the conveyance speed of the conveyance belt. Therefore, it takes a lot of time to determine the conveyance speed.

  Therefore, an object of the present invention is to reduce a user's burden for obtaining a work conveyance speed capable of achieving a desired reading success rate.

According to the present invention, for example,
An image pickup means for picking up an image of a code provided on a workpiece conveyed on the line;
Decoding means for decoding image data acquired by the imaging means;
Computation means for computing the maximum conveyance speed of the workpiece capable of decoding the code based on the exposure time of the imaging means and the maximum allowable blur amount of the code in the image data that can be decoded by the decoding means An optical information reading apparatus is provided.

According to the present invention, for example,
An image pickup means for picking up an image of a code provided on a workpiece conveyed on the line;
Decoding means for decoding image data acquired by the imaging means;
A difference is obtained by subtracting the length of the cord in the conveyance direction of the workpiece from the length of the visual field range of the imaging means in the conveyance direction of the workpiece, and the cord passes through the visual field range with the difference. Computation means for computing the upper limit transport speed of the workpiece by dividing by the number of times the code is imaged and decoded and the processing time required to image and decode the code An optical information reader is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the burden of the user for calculating | requiring the conveyance speed of the workpiece | work which can achieve a reading success rate can be reduced.

The figure which shows an optical information reader The figure which shows an example of the two-dimensional code from which blurring amount differs Diagram showing the relationship between the code and the field of view of the reader Diagram explaining how to find the viewing distance Diagram explaining the code size calculation method Diagram showing the effect of reading conditions on decoding results Diagram showing the effect of reading conditions on decoding results Figure showing the user interface for specifying the tuning method Block diagram showing electronic configuration of reader Block diagram showing electronic configuration of computer The figure which shows the user interface which displays conveyance speed and the number of times of imaging Flow chart showing a method for determining the conveyance speed Diagram explaining allowable depth Diagram explaining how to determine the allowable depth

  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.

<Maximum allowable blur amount>
FIG. 2 shows an example of a two-dimensional code having a different blur amount. The code 21a is a code image obtained by capturing an image of the work 2 in a stationary state. The code 21b is a code image captured when transported at the maximum transport speed vmax that can achieve a desired reading success rate. The conveyance speed may be referred to as a movement speed. The code 21b is a code image obtained by capturing an image while conveying the workpiece 2 at such a high speed that reading fails. Even if there is some blurring as in the code 21b, decoding can be performed correctly by the error correction function or the like. Here, the amount of shake that can achieve the desired reading success rate is referred to as the maximum allowable amount of shake. The maximum allowable blur amount c may be expressed by, for example, the number of cells 22 that is the minimum unit constituting the two-dimensional code. It is assumed that the maximum allowable shake amount c is obtained in advance at the time of shipment from the factory and is stored in a storage device such as a ROM of the reader 3.

  The maximum conveyance speed vmax of the workpiece 2 when performing one reading (taking the workpiece 2 once and decoding the obtained image) can be calculated from the following equation.

vmax = c / t (1)
Here, t is the exposure time. The exposure time t is a value that varies depending on the installation environment of the reader 3. Since the maximum allowable blur amount c is known, the maximum transport speed vmax can be calculated if the exposure time t is determined according to the installation environment.

<Maximum transport speed for multiple readings (upper transport speed)>
By the way, it is also possible to execute reading a plurality of times when the two-dimensional code passes through the imaging field range of the reader 3. This is because it is possible to decode a two-dimensional code more accurately by executing multiple readings.

  FIG. 3 is a diagram showing the relationship between the two-dimensional code and the visual field range 30 of the reader 3. Here, it is assumed that the workpiece 2 to which the two-dimensional code 21 is applied is conveyed in the lateral direction (horizontal direction). That is, it is assumed that the conveyance direction of the workpiece 2 and the horizontal direction of the visual field range 30 are parallel. As shown in FIG. 3, the length of the visual field range 30 in the horizontal direction is called a visual field distance h, and the length of the two-dimensional code 21 in the horizontal direction is called a code size CS. In this case, the distance for staying in the visual field range 30 without the whole two-dimensional code 21 being missing is h-CS. Here, the number of times RC that can read the two-dimensional code while the two-dimensional code stays in the visual field range 30 can be calculated by the following equation.

RC = ST / RT (2)
Here, RT is a processing time (reading time) related to one reading, and ST is a time during which the code stays in the visual field range 30 (staying time). The reading time RT is a value specific to the reader 3 and is known. The stay time ST can be calculated by the following equation.

ST = (h−CS) / v (3)
Here, v is the upper limit transport speed when performing RC readings. From equations (2) and (3), the upper limit transport speed v can be calculated by equation (4).

v = (h-CS) / (RC · RT) (4)
Here, the upper limit transport speed v must be equal to or less than the above-described maximum transport speed vmax. Therefore, the maximum number of readings RCmax is calculated as the maximum integer among RCs that satisfy the following equation.

vmax> = (h-CS) / (RC · RT) (5)
The upper limit transport speed v is calculated by substituting RCmax obtained by equation (5) into RC of equation (4). Note that the number of readings RC may be calculated by substituting vmax for v in equation (4).

  RC = (h−CS) / (vmax · RT) (5) ′.

<Calculation method of viewing distance h and code size CS>
Although the visual field distance h and the code size CS described above may be manually input by the user, it may be convenient for the user if the reader 3 calculates them.

  FIG. 4 is a diagram for explaining a method for obtaining the viewing distance h. The distance from the reader 3 to the workpiece 2 is referred to as an installation distance d. θ is an angle of view of the optical system of the reader 3 and is known. The installation distance d may be measured and input by the user using a scale, or may be calculated by the reader 3. If the laser distance measuring device is mounted on the reader 3, the installation distance d may be measured thereby. Further, in the reader 3 equipped with an autofocus (AF) mechanism, the position of the focusing lens (the number of steps of the AF motor, the amount of rotation, etc.) and the refractive index (liquid lens) when the two-dimensional code of the work 2 is focused. The adjustment amount Δ of the applied voltage to () may be converted into the installation distance d. This can be easily realized by preparing a conversion formula or conversion table between the adjustment amount Δ and the installation distance d in advance. The viewing distance h is calculated by substituting the installation distance d thus obtained in the equation (6).

h = 2d · tan (θ / 2) (6)
FIG. 5 is a diagram illustrating a method for calculating the code size CS. The horizontal size output by the reader 3 and the vertical size of the image are known as 1280 × 768 pixels. Further, it can be easily counted how many pixels the two-dimensional code 21 is configured in the read image. Further, the viewing distance h corresponds to the horizontal size of the read image 32. Therefore, the code size CS can be calculated from the following equation.

CS = (h / HP) × n (7)
Here, n is the number of horizontal pixels constituting the two-dimensional code 21 in the read image 32.

  Thus, since the reader 3 can obtain the maximum transport speed vmax when reading once and the upper limit transport speed v when performing reading a plurality of times, the burden on the user can be greatly reduced.

<Reading condition control (tuning)>
The reader 3 adjusts various reading conditions so that the two-dimensional code can be successfully decoded. Here, of the reading conditions, the relationship between the exposure time and the gain will be described. The gain is a rate (also referred to as an amplification factor or magnification) for amplifying image brightness by digital image processing.

  As shown in FIG. 6, when the exposure time becomes longer, the read image of the two-dimensional code becomes brighter, but blurring occurs, and the reader 3 fails to decode. If the exposure time is appropriate, the brightness of the read image of the two-dimensional code remains sufficient and no blurring occurs, so the reader 3 succeeds in decoding. When the exposure time is shortened, the two-dimensional code read image does not blur, but the read image becomes dark, and the reader 3 fails to decode.

  As shown in FIG. 7, when the exposure time is set short and the gain is set high, the read image of the two-dimensional code becomes bright and no blur occurs, but the noise component of the read image is also amplified. The reader 3 fails to decode. If the exposure time is set longer and the gain is set lower, the read image of the two-dimensional code becomes brighter, but the image tends to be blurred, and the reader 3 fails to decode.

  Therefore, the exposure time and gain need to be adjusted appropriately. In the present embodiment, the target is to read the two-dimensional code with the reader 3 while the workpiece 2 is conveyed. For this reason, the exposure time is specified and fixed in advance so that the exposure time is short enough to prevent blurring. On the other hand, the gain is variable, and the reader 3 searches for an appropriate gain.

  FIG. 8 is a diagram illustrating an example of a user interface (UI) for designating a tuning method when the workpiece 2 is a moving body. The UI 40 is displayed on the display of the computer 4, for example. The UI 40 is provided with a designation unit 41 for adjusting the brightness when the work 2 is a moving body, and a designation unit 42 for the exposure time when the work 2 is a moving body. When the user designates the exposure time, the reader 3 calculates an appropriate gain corresponding to the exposure time.

<Control unit>
FIG. 9 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 illumination unit 52 has one or more light emitting elements and is a unit that illuminates a two-dimensional code.

  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 an image display device and a light emitting element for an indicator. 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. In particular, the display unit 55 of the present embodiment is a display unit that displays the maximum conveyance speed vmax, the upper limit conveyance speed v, and the number of times RC that can be decoded by capturing a two-dimensional code while the work 2 stays in the visual field range 30. May function. These pieces of information may be displayed on a display such as the computer 4. The input unit 56 is a unit that receives an input operation such as a switch.

  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 adjusts the above-described gain, controls the amount of illumination light of the illumination unit 52, and controls the exposure time (shutter speed) of the imaging device 31.

  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 a unit other than the calculation unit 63 such as the decoding unit 53. The setting unit 64 is a unit for setting the IP address of the communication unit 54 and the like. The calculation unit 63 may calculate the maximum conveyance speed vmax, the upper limit conveyance speed v, and the number of times RC that can be decoded. These calculations may be executed by the computer 4.

  The tuning unit 65 is a reading condition control unit, and is a unit that controls imaging conditions such as exposure time, illumination light quantity, and 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 display unit 55, receives a user instruction from the input unit 56, and controls lighting of the indicator. For example, the display unit 55 causes the display unit 55 to display a UI for inputting information necessary for calculating the maximum transport speed vmax, the upper limit transport speed v, and the number of times RC that can be decoded, or the maximum transport speed vmax and the upper limit transport speed. A UI for displaying the speed v and the number of times RC that can be decoded is created and displayed on the display unit 55.

  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, which is data set by the setting unit 64, is stored.

  FIG. 10 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 one function of the calculation unit 81, generates a user interface for setting the imaging conditions of the reader 3, and a user interface for displaying the decoding result 71, the image data 72, and the like output from the reader 3. Are displayed on the display unit 84. For example, the UI control unit 83 may create the UI 40 as shown in FIG. 8 and display it on the display unit 84, or create the UI 110 as shown in FIG. 11 and display it on the display unit 84. . The UI 110 includes a display area 111 for displaying the conveyance speed of the work 2, a display area 112 for the number of times of imaging, and a designation unit 113 for the number of times of imaging. The transport speed is, for example, at least one of the maximum transport speed vmax and the upper limit transport speed v. The UI control unit 83 increases or decreases the number of times of imaging one by one according to an instruction to the specifying unit 113. The calculation unit 81 is a unit that executes various calculations. All or part of the calculations performed by the calculation unit 63 of the reader 3 may be performed by the calculation unit 81. 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.

<Flowchart>
Here, each step executed by the control unit 60 of the reader 3 will be described with reference to FIG. Each step may be executed while the CPU 80 of the computer 4 controls the reader 3. It is assumed that a work 2 to which a two-dimensional code is assigned in advance is placed on the optical axis of the reader 3. The order of the following steps can be changed as long as the overall processing is not hindered.

  In S1201, the calculation unit 63 instructs the tuning unit 65 to start tuning. The tuning unit 65 controls the imaging control unit 62 to determine an appropriate exposure time t based on the video signal from the imaging device 31. Alternatively, the calculation unit 63 may determine the exposure time t by acquiring the exposure time t specified through the UI 40 illustrated in FIG. 8 from the setting data 73.

  In S1202, the calculation unit 63 causes the tuning unit 65 to determine the gain and the reading time RT based on the exposure time t. It is assumed that an appropriate gain value for the exposure time t is prepared as a function or a table and is stored in the storage unit 70. The tuning unit 65 determines a gain corresponding to the exposure time t determined by the imaging control unit 62 using a function or table stored in the storage unit 70. The reading time RT with respect to the exposure time t is prepared as a function or a table and is stored in the storage unit 70. The tuning unit 65 determines a reading time RT corresponding to the exposure time t using a function or table stored in the storage unit 70.

  In step S <b> 1203, the calculation unit 63 causes the AF control unit 61 to perform autofocus through the tuning unit 65 and acquires the AF adjustment amount Δ from the AF control unit 61.

  In S1204, the calculation unit 63 causes the imaging control unit 62 to perform imaging of the two-dimensional code through the tuning unit 65. It is assumed that the entire two-dimensional code is captured in the image acquired by the image sensor 31 without being lost.

  In S1205, the calculation unit 63 determines the installation distance d based on the AF adjustment amount Δ. As described above, it is assumed that a function and a table for converting the AF adjustment amount Δ into the installation distance d are stored in the storage unit 70.

  In S1206, the calculation unit 63 determines the viewing distance h based on the installation distance d. For example, the above-described equation (6) is stored in the storage unit 70, and the calculation unit 63 calculates the visual field distance h based on the installation distance d using the equation (6).

  In S1207, the calculation unit 63 determines the code size CS based on the viewing distance h. The calculation unit 63 calculates the code size CS using the above-described equation (7).

  In S1208, the calculation unit 63 determines the maximum transport speed vmax for one reading. As described above, the calculation unit 63 calculates the maximum transport speed vmax from the exposure time t and the maximum allowable shake amount c using the equation (1).

  In S <b> 1209, the calculation unit 63 acquires a predetermined number of readings RC from the setting data 73. The number of times of reading RC may be designated by the user through the UI 110 and written to the setting data 73, or may be a value fixed in advance.

  In S1210, the calculation unit 63 determines the upper limit transport speed v. For example, as described using equation (4), the calculation unit 63 calculates the upper limit transport speed v based on the viewing distance h, the code size CS, the number of readings RC, and the reading time RT.

Arithmetic unit 63 in S1211, the calculated upper conveying speed v is determined whether exceeds the maximum conveying speed. The upper limit of the conveying speed v proceeds to S121 2 does not exceed the maximum transport speed vmax, maximum transport speed v is advanced the maximum transport speed vmax to S1213 if exceeded. That is, if the upper limit transport speed v exceeds the maximum transport speed vmax at a certain number of times of reading RC, the immediately preceding number of times of reading RC + 1 is the above-mentioned maximum integer, and the upper limit transport speed v at that time is the maximum transport speed vmax. The upper limit transport speed is as follows.

In S1212, the calculation unit 63 decrements the reading count RC by one, returns to S1210, and calculates the upper limit transport speed v again. Thus, processing to S1210 without until the transport speed of the upper limit equal to or less than the maximum transport speed vmax S1212 is repeatedly executed.

  In S1213, the calculation unit 63 passes the number of readings RC, the maximum conveyance speed vmax, and the upper limit conveyance speed v to the UI management unit 66, and the UI management unit 66 displays the number of readings RC, the maximum conveyance speed vmax, and the upper limit conveyance speed v. A UI is created and displayed on the display unit 55. When reading once, S1209 to S1212 may be omitted, and only the maximum transport speed vmax may be displayed on the display unit 55. When reading a plurality of times, S1209 to S1212 are executed, and the readable count RC and the upper limit transport speed v are displayed on the display unit 55. Note that the display of the readable number of times RC may be omitted.

<Summary>
According to the present embodiment, the calculation unit 63 determines the maximum work that can decode a code based on the exposure time t of the image sensor 31 and the maximum allowable blur amount c of the image data that can be decoded by the decoding unit 53. The conveyance speed vmax is calculated. Therefore, it is possible to reduce the burden on the user for obtaining the workpiece conveyance speed that can achieve the predetermined reading success rate.

  As described using the equation (1), the calculation unit 63 may calculate the maximum conveyance speed vmax of the workpiece by dividing the maximum allowable blur amount c by the exposure time t.

The calculation unit 63 may calculate the upper limit transport speed v when performing reading a plurality of times. As described using the equation (4), the calculation unit 63 calculates the length of the cord in the transport direction of the workpiece 2 from the length of the field of view of the imaging element 31 (view distance h) in the transport direction of the workpiece 2 (code Subtract size CS) to find the difference. The calculation unit 63 uses this difference as the number of times that the code is imaged and decoded when the code passes through the visual field range (reading number RC) and the processing time (reading) required to image and decode the code. The conveyance speed v is calculated by dividing by (time RT). As a result, it is possible to reduce a user's burden for obtaining a work conveyance speed that can achieve a predetermined reading success rate. The arithmetic unit 63, the process, until the transport velocity v of the upper limit equal to or less than the maximum transport speed vmax, may be repeatedly performed while reducing the number of reads RC one. As a result, it is possible to easily calculate the transport speed that is the upper limit when reading a plurality of times.

  (5) As described using the equation ', the calculation unit 63 subtracts the code size CS from the visual field distance h to obtain a difference (h−CS), and the difference is calculated from the maximum conveyance speed vmax and the reading time RT. The number of times of decoding (number of readings RC) may be calculated by dividing by. As a result, the number of times of reading when the workpiece 2 is conveyed at the maximum conveyance speed vmax can be known.

  Based on the angle of view θ of the image sensor 31 in the workpiece conveyance direction and the installation distance d from the image sensor 31 to the workpiece 2, the calculation unit 63 determines the length of the field of view of the image sensor 31 in the workpiece conveyance direction (view distance) h) may be calculated. This saves the user from having to calculate the viewing distance h.

  The calculation unit 63 may acquire the focus adjustment amount Δ from the autofocus function (the AF mechanism 51 and the AF control unit 61), and convert the adjustment amount Δ into the installation distance d from the image sensor 31 to the workpiece. In this case, the user can save the trouble of measuring the installation distance d. Further, a dedicated distance measuring device for measuring the installation distance d can be omitted, which is advantageous in terms of manufacturing cost.

  The calculation unit 63 obtains a quotient by dividing the visual field distance h by the number of pixels HP of the image sensor 31 in the conveyance direction of the workpiece 2 and multiplies the number of pixels n of the code in the conveyance direction of the workpiece 2 in the image data. The code size CS in the workpiece conveyance direction may be calculated. This saves the user from having to input and calculate the code size CS.

  The tuning unit 65 and the imaging control unit 62 may function as an adjustment unit that adjusts the exposure time t and the gain g of the imaging device 31 based on the decoding result of the decoding unit 53. In the above-described embodiment, it has been described that the exposure time t is obtained in advance. However, the exposure time t and the gain g may be adjusted using the decoding result as described above. This saves the user the trouble of inputting the exposure time t. As a result of tuning, when the exposure time t changes, the maximum transport speed vmax and the like also change. Therefore, the calculation unit 63 may recalculate the maximum transport speed vmax when the exposure time t is changed by the tuning unit 65 and the imaging control unit 62.

  The display units 55 and 84 display first display means for displaying a maximum conveyance speed vmax that is an upper limit conveyance speed when the workpiece 2 is captured and decoded only once while the workpiece 2 passes through the visual field range of the image sensor 31. May function as Similarly, the display units 55 and 84 display the upper limit transport speed v that is the upper limit transport speed when the workpiece 2 passes through the visual field range of the image sensor 31 and is imaged and decoded a plurality of times. It may function as one display means. Furthermore, the display units 55 and 84 may function as second display means for displaying the number of times that decoding is possible.

  The tuning unit 65 and the imaging control unit 62 may function as a reading condition control unit that controls reading conditions including the imaging conditions of the imaging element 31 and the image processing conditions in the decoding unit 53. The calculation unit 63 may calculate the maximum conveyance speed after the reading condition is determined by the tuning unit 65 and the imaging control unit 62. Thus, by calculating the maximum conveyance speed after the reading conditions are appropriately determined, the maximum conveyance speed can be calculated more accurately according to the installation environment of the reader 3.

  The calculation unit 63 may function as an allowable depth calculation unit. The allowable depth is an installation distance d at which a desired decoding result (reading success rate or matching level) can be achieved when the workpiece 2 and the reader 3 are installed at a certain installation distance d (reference distance RD). Is the range of change.

  As shown in FIG. 13, the reader 3 and the work 2 are installed such that the installation distance d is the reference distance RD. The reference distance RD is an arbitrary distance. In FIG. 13, the reference distance RD is a distance from the end P0 of the reader 3 to the position of the two-dimensional code 21 (referred to as a reference position Pr). Pn is a position where a desired decoding result can be achieved even if the two-dimensional code 21 is moved to the near side. Pf is a position where a desired decoding result can be achieved even if the two-dimensional code 21 is moved to the far side. Therefore, the allowable depth DD is a range from Pn to Pf. It may be very troublesome to obtain the allowable depth DD while manually moving the leader 3 or the work 2. This is because the reader 3 is fixed to the production line.

  Accordingly, the calculation unit 63 decodes the image data acquired by the image sensor 31 for each adjustment amount by the decoding unit 53 when the adjustment amount Δ in the autofocus function of the image sensor 31 is changed in a plurality of ways. Get the matching level as The matching level is an index indicating the ease of decoding of the two-dimensional code as is well known in the art.

  As illustrated in FIG. 14, the calculation unit 63 obtains a correspondence relationship between the installation distance d obtained by converting the adjustment amount Δ and the decoding result. UML is the matching level desired by the user. If the matching level corresponding to the installation distance d is UML or more, the installation distance d is within the allowable depth range. As described above, the calculation unit 63 calculates the allowable depth DD, which is the distance from the image sensor 31 to the work that is allowed to decode the code based on the correspondence between the installation distance d and the decoding result. In the example shown in FIG. 14, the reference distance RD is 170 mm, the allowable depth DD is 130 mm to 220 mm, the near side margin Mn is 40 mm, and the far side margin Mf is 50 mm.

  The calculation unit 63 may calculate the maximum transport speed vmax and the upper limit transport speed v after the allowable depth DD is determined. This is because when the allowable depth DD is determined, the installation distance d between the reader 3 and the work 2 is appropriately adjusted, so that tuning is also appropriately performed and calculation accuracy such as a conveyance speed is improved.

  DESCRIPTION OF SYMBOLS 1 ... Line, 2 ... Work, 3 ... Illuminating device, 4 ... Camera, 5 ... Image processing apparatus, 6 ... Input part, 7 ... Display part

Claims (16)

An image pickup means for picking up an image of a code provided on a workpiece conveyed on the line;
Decoding means for decoding image data acquired by the imaging means;
An arithmetic means for calculating a maximum transport speed of the workpiece capable of decoding the code based on an exposure time of the imaging means and a maximum allowable blur amount of the code in the image data that can be decoded by the decoding means;
An optical information reading apparatus comprising:   The optical information reading apparatus according to claim 1, wherein the calculation unit calculates the maximum conveyance speed of the workpiece by dividing the maximum allowable shake amount by the exposure time. The calculation means obtains a difference by subtracting the length of the code in the conveyance direction of the work from the length of the visual field range of the imaging means in the conveyance direction of the work, and calculates the difference as the code in the visual field range. There the process of the code by capturing calculates the conveying speed by dividing the processing time by capturing the number and the code for decoding required to decode as it passes through, one pre Symbol number by repeatedly executing while decreasing by, according to claim 2, wherein the obtaining and upper conveying speed of equal to or less than the maximum transport speed, and the number of times when the conveying speed of the upper limit was obtained Optical information reader.   The calculation means obtains a difference by subtracting the length of the code in the workpiece conveyance direction from the length of the field of view of the imaging means in the workpiece conveyance direction, and calculates the difference as the maximum conveyance speed and the By dividing by the processing time required to capture and decode the code, the number of times that the code can be captured and decoded when the code passes through the visual field range is calculated. The optical information reader according to claim 2. An image pickup means for picking up an image of a code provided on a workpiece conveyed on the line;
Decoding means for decoding image data acquired by the imaging means;
A maximum conveyance speed of the workpiece capable of decoding the code is calculated based on an exposure time of the imaging unit and a maximum allowable blur amount of the code in the image data that can be decoded by the decoding unit, and further the conveyance of the workpiece A difference is obtained by subtracting the length of the cord in the conveyance direction of the workpiece from the length of the visual field range of the imaging means in the direction, and the difference is calculated when the code passes through the visual field range. the by imaging is divided by the processing time required to image the number and the code to be decoded to decode, and arithmetic means for calculating an upper limit conveying speed of the workpiece such that following said maximum transport speed An optical information reading apparatus comprising:   The computing means calculates the length of the visual field range of the imaging means in the workpiece conveyance direction based on the angle of view of the imaging means in the workpiece conveyance direction and the distance from the imaging means to the workpiece. The optical information reader according to claim 3, wherein the optical information reader is an optical information reader.   The imaging means has an autofocus function, and the calculation means acquires a focus adjustment amount from the autofocus function, and converts the adjustment amount into a distance from the imaging means to the workpiece. The optical information reader according to claim 6.   The arithmetic means obtains a quotient by dividing the length of the visual field range of the imaging means by the number of pixels of the imaging means in the workpiece conveyance direction, and the pixel of the code in the workpiece conveyance direction in the image data The optical information reading apparatus according to claim 3, wherein the length of the code in the conveyance direction of the workpiece is calculated by multiplying by a number. An adjustment unit that adjusts an exposure time and a gain of the imaging unit based on a decoding result of the decoding unit;
9. The optical information reading according to claim 1, wherein the calculating unit recalculates the maximum conveyance speed when the exposure time is changed by the adjusting unit. 10. apparatus. Further comprising a first display means for displaying the maximum conveying speed and most significant conveying speed at which the workpiece by imaging only once decoding while the workpiece passes through the field of view of said image pickup means An optical information reader according to any one of claims 1 to 9. 4. The apparatus according to claim 3, further comprising first display means for displaying the upper limit transport speed when the workpiece is imaged and decoded a plurality of times while the workpiece passes the visual field range of the imaging means. Or an optical information reading apparatus according to 5;   5. The optical information reading apparatus according to claim 4, further comprising second display means for displaying the number of times that can be decoded. A reading condition control means for controlling a reading condition including an imaging condition of the imaging means and an image processing condition in the decoding means;
13. The optical information reading apparatus according to claim 1, wherein the calculating unit calculates the maximum transport speed after the reading condition is determined by the reading condition control unit. . When the adjustment amount in the autofocus function of the imaging unit is changed in a plurality of ways, the decoding result by the decoding unit is acquired for each image data acquired by the imaging unit for each adjustment amount, and the adjustment amount is calculated. The correspondence between the distance from the imaging means obtained by conversion to the workpiece and the decoding result is obtained, and the distance from the imaging means to the workpiece allowed to decode the code based on the correspondence is obtained. A calculation means for calculating a certain allowable depth;
The optical information reading apparatus according to claim 1, wherein the calculation unit calculates the maximum transport speed after the allowable depth is determined. An image pickup means for picking up an image of a code provided on a workpiece conveyed on the line;
Decoding means for decoding image data acquired by the imaging means;
As a computing means for computing the maximum transport speed of the workpiece capable of decoding the code based on the exposure time of the imaging means and the maximum allowable blur amount of the code in the image data that can be decoded by the decoding means. A program that makes it work. An imaging step of imaging a code provided on a workpiece conveyed through the line;
A decoding step of decoding the image data acquired in the imaging step;
A calculation step of calculating a maximum conveyance speed of the workpiece capable of decoding the code based on an exposure time in the imaging step and a maximum allowable blur amount of the code in the image data that can be decoded in the decoding step;
An optical information reading method comprising: