Optical information reading device

Abstract

To provide a configuration capable of calculating an allowable distance based on an evaluation result acquired by generating plural pieces of distance change image data and evaluating each one without requiring a focus adjustment mechanism.SOLUTION: When a distance between an imaging unit 23 and an information code C at the time of successful reading is set as a reference distance Xo, and image data at the time of successful reading is used as base image data, plural pieces of distance change image data where an image data generation distance Xk is changed from the reference distance Xo are generated from the base image data. Then, when readability of each of the generated, plural pieces of distance change image data is evaluated, a distance between an information code and the imaging unit 23, which is allowed for reading the information code, is calculated based on this evaluation result as an allowable distance, and information about the allowable distance is indicated.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to an optical information reading device for optically reading an information code.

Background Art

[0002] Conventionally, when a work with an information code such as a QR code (registered trademark) printed thereon is conveyed on a production line, the information code is optically read by a fixed optical information reading device installed on the production line. In such an operation, by focusing on the information code, the information to be read can be stably read from the captured image of the information code that is imaged without blurring. By the way, even if an information code whose reading distance (the distance from the imaging means of the optical information reading device to the information code) is slightly deviated from the best focus distance to the near-point side or the far-point side can be stably read, if the reading distance varies due to differences in the size of the work or misalignment, etc., the reading may become unstable. And when such variation in the reading distance becomes large, there is a problem that the reading of the information code fails.

[0003] For this reason, for example, an optical information reading device disclosed in Patent Document 1 below is known. In this optical information reading device, when the adjustment amount in the focus adjustment mechanism is changed in a plurality of ways, a decoding result is obtained for each image data acquired for each adjustment amount. Then, based on the correspondence relationship between the reading distance obtained by converting the adjustment amount and the decoding result, a depth of tolerance (tolerance distance: the range of distances capable of achieving a desired reading success rate) is calculated, and by presenting the depth of tolerance calculated in this way to a user or the like, stable reading of the information code is maintained.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] By the way, in a configuration where the allowable distance (allowable depth of field) is calculated by changing the adjustment amount of the focus adjustment mechanism in multiple ways, as described above, a focus adjustment mechanism is essential, and there is a problem that optical information reading devices that do not have a focus adjustment mechanism cannot calculate the allowable distance to be notified.

[0006] The present invention was made to solve the above-mentioned problems, and its objective is to provide a configuration that can generate multiple distance change image data and calculate an acceptable distance based on the evaluation results obtained from evaluating each of them, without requiring a focus adjustment mechanism. [Means for solving the problem]

[0007] To achieve the above objective, the invention described in claim 1 of the claims is: A fixed optical information reading device (10) that optically reads an information code (C) printed on a workpiece (W), Imaging means (23), The reading means (21) decodes and reads the image data captured by the imaging means, When the distance between the imaging means and the information code at the time of successful reading by the reading means is defined as the reference distance (Xo), and the image data at the time of successful reading is defined as the base image data, a distance change image data generation means (21) generates a plurality of distance change image data from the base image data, each obtained by changing the distance (Xk) between the imaging means and the information code from the reference distance. An evaluation means (21) for evaluating the readability (S) of each of the multiple distance change image data generated by the distance change image data generation means, An allowable distance calculation means (21) calculates the distance between the information code and the imaging means that is permissible to read the information code based on the evaluation result of the evaluation means, Notification means (25) for notifying information regarding the allowable distance calculated by the allowable distance calculation means, It is characterized by having the following features. The symbols within the parentheses above indicate the correspondence with the specific means described in the embodiments described later. [Effects of the Invention]

[0008] In the invention of claim 1, when the distance between the imaging means and the information code at the time of successful reading by the reading means is used as the reference distance and the image data at the time of successful reading is used as the base image data, a plurality of distance-changed image data, each obtained by changing the distance between the imaging means and the information code from the reference distance, is generated from the base image data by the distance-changed image data generation means. Then, the readability of each of the generated plurality of distance-changed image data is evaluated by the evaluation means, and based on this evaluation result, the distance between the information code and the imaging means that is permissible for reading the information code is calculated as the permissible distance by the permissible distance calculation means, and information regarding this permissible distance is notified by the notification means.

[0009] This allows for the generation of multiple distance-change image data from a single base image data, without having to capture and generate image data each time the adjustment amount of the focus adjustment mechanism is changed. Therefore, it is possible to generate multiple distance-change image data without requiring a focus adjustment mechanism, and then calculate and notify the acceptable distance based on the evaluation results of each image data.

[0010] As in the invention of claim 2, the allowable distance may be calculated such that the evaluation result by the evaluation means satisfies a predetermined threshold condition, and is between a first distance where the distance between the information code and the imaging means is closest and a second distance where the distance between the information code and the imaging means is farthest.

[0011] The invention of claim 3 includes a threshold condition setting means capable of setting the above-mentioned predetermined threshold conditions, so that the threshold conditions can be set to match the environment in which the optical information reading device is employed.

[0012] In the invention of claim 4, the threshold condition setting means sets the predetermined threshold conditions in response to instructions from an external device, so the user does not need to input setting values ​​each time, thus improving convenience in setting threshold conditions.

[0013] In the invention of claim 5, the permissible distance calculation means calculates the near-point margin, which is the difference between the distance between the information code and the imaging means and the closest permissible distance between the information code and the imaging means for reading purposes, and this information regarding the near-point margin is notified by the notification means. As a result, the user who receives this notification can clearly understand the near-point margin.

[0014] In the invention of claim 6, the permissible distance calculation means calculates the afar point margin, which is the difference between the distance between the information code and the imaging means and the furthest distance between the information code and the imaging means that is permissible for reading, and this information regarding the afar point margin is notified by the notification means. As a result, the user who receives this notification can clearly understand the afar point margin.

[0015] In the invention of claim 7, the base image data is the image data obtained when reading is successful, with the reference distance being the distance at which the imaging means focuses on the information code by the focus adjustment mechanism. This not only makes it possible to determine that the base image data is image data captured without blurring the information code, but also clarifies the distance at which multiple distance-change image data should be generated, thereby reducing the processing load related to the generation of each distance-change image data.

[0016] The invention of claim 8 includes a means for acquiring a reference distance, so that it is easy to determine whether the base image data is image data captured at the distance to be focused or at a distance far from the distance to be focused. Since the distance at which the base image data was captured (reference distance) is clearly defined, the distance at which multiple distance-changing image data should be generated becomes clearer compared to the case where the reference distance is not acquired, thus reducing the processing load related to the generation of each distance-changing image data.

[0017] In the invention of claim 9, when the distance from the imaging means on which distance-changing image data is created is defined as the image data generation distance, the distance-changing image data generation means generates a plurality of distance-changing image data from the base image data based on the image data generation distance, the image data generation distance, and the magnification factor of the image determined from the field of view of the imaging means, using the relationship between the distance from the best focus position of the imaging means and the diameter of the circle of confusion as a basis for determining the image data generation distance.

[0018] The circle of confusion diameter for light focused by the optical system at the pixel level is smallest at the reading distance corresponding to the best focus position, and increases as the reading distance increases, resulting in a blurred image. The degree of change in the circle of confusion diameter differs depending on whether the reading distance is near or far from the best focus position, and this degree of change depends on the configuration of the optical system. If the configuration of the optical system is known, the degree of change in the circle of confusion diameter can be determined in advance, and the circle of confusion diameter at any reading distance relative to the best focus position can be calculated.

[0019] Therefore, since the degree of change in the circle of confusion diameter related to the optical system of the imaging means can be grasped based on the configuration of the optical system, distance-changing image data at a certain image data generation distance can be generated by correcting the base image data so that each pixel is blurred according to the circle of confusion diameter at the image data generation distance, and then scaling it up or down according to the magnification ratio. Furthermore, by changing the image data generation distance, multiple distance-changing image data can be generated from a single base image data.

[0020] In the invention according to claim 10, after the allowable distance is calculated by the allowable distance calculating means, when the difference between the distance between the information code imaged by the imaging means and the imaging means and the allowable distance becomes equal to or less than a predetermined distance, a predetermined warning is notified by the notification means. Thereby, it is possible to prompt a user or the like who has received the above-described predetermined warning to change the distance (reading distance) from the imaging means to the information code in order to perform stable reading.

[0021] In the invention according to claim 11, since the notification means visually notifies the above-described predetermined warning, a user or the like who has received the above-described predetermined warning can easily visually recognize not only the presence or absence of the warning but also the level of the warning.

[0022] In the invention according to claim 12, since the notification means notifies by transmitting the above-described predetermined warning to an external device, it is also possible to prompt an administrator or the like who manages the above-described external device to change the reading distance or the like for performing stable reading.

Brief Description of the Drawings

[0023] [Figure 1] It is an explanatory diagram schematically showing an optical information reading device according to the first embodiment. [Figure 2] It is a block diagram schematically showing an electrical configuration of the optical information reading device. [Figure 3] It is an explanatory diagram explaining the reading stability that changes according to the reading distance. [Figure 4] It is an explanatory diagram explaining the diameter of the confusion circle that changes according to the reading distance. [Figure 5] It is an explanatory diagram explaining the magnification that changes according to the reading distance. [Figure 6] It is an explanatory diagram explaining a state in which an information code is imaged in a state where the reference distance coincides with the reading distance that is the best focus position. [Figure 7]Figure 7(A) is an explanatory diagram illustrating distance-changing image data created by shifting the base image data of Figure 7(B) toward the near point, Figure 7(B) is an explanatory diagram illustrating base image data captured at the reading distance that is the best focus position, and Figure 7(C) is an explanatory diagram illustrating distance-changing image data created by shifting the base image data of Figure 7(B) toward the far point. [Figure 8] This diagram illustrates a situation where the information code is captured when the reference distance is deviated from the reading distance that results in the best focus position. [Figure 9] This is an explanatory diagram illustrating the process of determining the diameter of the circle of confusion at a given reference distance from the acquired reference distance. [Modes for carrying out the invention]

[0024] [First Embodiment] A first embodiment of the optical information reading device of the present invention will be described below with reference to the drawings. The optical information reading device 10 according to this embodiment is a fixed information reading device that optically reads information codes (such as barcodes and QR codes) and character information. Specifically, as shown in Figure 1, the optical information reading device 10 is positioned on a transport path on which a workpiece W is transported, so as to read the information code C printed on the workpiece W, and is configured to transmit the reading results to a higher-level terminal 100. The information code C may be applied to the workpiece W by direct marking (DPM) or by printing on the workpiece W.

[0025] As shown in Figure 1, the housing 11 that constitutes the outer casing of the optical information reading device 10 is formed in a roughly rectangular parallelepiped shape, and the display screen of the display unit 25 and the operation switches of the operation unit 26 are arranged on its front surface. In addition, a reading opening is provided on the lower surface of the housing 11 for taking in reflected light from information codes, etc., into the housing 11.

[0026] As shown in Figure 2, the optical information reading device 10 includes a control unit 21 that oversees overall control, a storage unit 22 consisting of semiconductor memory or the like, an imaging unit 23 configured as a camera that captures information codes or the like through a reading port, an illumination unit 24 that illuminates the field of view captured by the imaging unit 23 with illumination light, a display unit 25 whose display content is controlled by the control unit 21, an operation unit 26 that outputs operation signals to the control unit 21 in response to input operations on operation switches, etc., a communication unit 27 for communicating with external devices such as a host terminal 100, and a power supply unit (not shown). In this embodiment, the imaging unit 23 may correspond to an example of an "imaging means" that does not have a focus adjustment mechanism.

[0027] In the optical information reading device 10 configured in this way, the imaging unit 23 captures the information code C of the workpiece W as it is sequentially transported along the transport path, and the control unit 21 performs a reading process to decode and read the image data in which the information code C has been captured. The reading result of this reading process is transmitted to the host terminal 100 via the communication unit 27 at a predetermined timing. The control unit 21 that performs the above reading process may correspond to an example of a "reading means".

[0028] In this embodiment, before starting the reading process described above, a graph showing the reading stability S, which changes depending on the distance from the imaging unit 23 of the optical information reading device 10 to the information code C of the test workpiece (hereinafter also simply referred to as the reading distance X), is created as described later, as shown in Figure 3. The reading stability S is an index indicating the ease of reading the information code, which is determined from the relationship between the number of images taken and the number of successful decodes in the reading process performed by the control unit 21. It is highest near the position (reading distance) where the imaging unit 23 is in best focus, and decreases as the distance from this best focus position to the near or far point increases due to the greater effect of blurring in the captured image. Depending on the state of the information code being captured and the surrounding environment, the reading stability S may be high even with some blurring, and the position where the best focus occurs is not necessarily where the reading stability S is highest.

[0029] In this embodiment, as shown in Figure 3, among the reading distances X at which the reading stability S is equal to or greater than a predetermined threshold St, the closest distance is defined as the near-point limit distance Xt1, and the furthest distance is defined as the far-point limit distance Xt2. The reading distance X between the near-point limit distance Xt1 and the far-point limit distance Xt2 is then calculated as the allowable distance. The near-point limit distance Xt1 and the far-point limit distance Xt2 calculated in this way are stored in the storage unit 22 as information related to the allowable distance. The control unit 21 that performs the processing of calculating the near-point limit distance Xt1 and the far-point limit distance Xt2 as information related to the allowable distance may correspond to an example of an "allowable distance calculation means". Furthermore, the predetermined threshold St may correspond to an example of a "predetermined threshold condition", and the near-point limit distance Xt1 may correspond to an example of a "first distance" at which the distance between the information code C and the imaging unit 23 is closest, and the evaluation result satisfies the predetermined threshold condition. Furthermore, the far-point limit distance Xt2 is a distance at which the evaluation result satisfies predetermined threshold conditions, and may correspond to an example of a "second distance" where the distance between information code C and the imaging unit 23 is the farthest.

[0030] Therefore, the information regarding the allowable distance calculated as described above is notified via screen display or the like by the display unit 25 or the upper-level terminal 100 that receives this information via the communication unit 27. This allows the user who receives this notification to understand the allowable distance at which the information code C can be reliably read before actually transporting the workpiece W. Furthermore, when the workpiece W is actually transported, if the reading distance X to the captured information code C is within the allowable distance, it is determined that the information code C can be reliably read. On the other hand, if the reading distance X to the captured information code C is not within the allowable distance, it is determined that the information code C cannot be reliably read.

[0031] In particular, in this embodiment, a graph of reading stability S (see Figure 3) for determining the near-point limit distance Xt1 and far-point limit distance Xt2 for the imaging unit 23 is generated based on a single image data taken when the information code C of a test workpiece is successfully read. This is because the optical information reading device 10 does not have a focus adjustment mechanism, and therefore the reading distance X cannot be freely changed for the same information code C.

[0032] Specifically, the distance-changed image data generation process performed by the control unit 21 uses the distance between the imaging unit 23 and the information code C at the time of successful reading as the reference distance Xo, and the image data at the time of successful reading as the base image data. Multiple image data (hereinafter also referred to as distance-changed image data) are then generated from the base image data, each with a distance between the imaging unit 23 and the information code C (hereinafter also referred to as the image data generation distance Xk) that is different from the reference distance Xo. The control unit 21 that performs the above distance-changed image data generation process may correspond to an example of a "distance-changed image data generation means".

[0033] The generation method for generating multiple distance-varying image data from base image data will be described in detail below with reference to the diagram. The circle of confusion diameter R of light focused by the optical system at the pixel level is smallest at the reading distance Xf, which is the best focus position, as illustrated in Figure 4. It increases as you move away from the best focus position, resulting in a blurred image. The degree of change in the circle of confusion diameter R differs depending on whether you move towards the near point or the far point from the best focus position, and this degree of change depends on the configuration of the optical system. If the configuration of the optical system is known, the degree of change in the circle of confusion diameter R, as illustrated in Figure 4, can be determined in advance, and the circle of confusion diameter R at any reading distance X relative to the best focus position (reading distance Xf) can be calculated.

[0034] Therefore, since the degree of change in the circle of confusion diameter R of the optical system of the imaging unit 23 used in the optical information reading device 10 can be grasped based on the configuration of the optical system, distance change image data at a certain image data generation distance Xk can be generated by correcting the base image data so that each pixel blurs according to the circle of confusion diameter R at the image data generation distance Xk, and then scaling it up or down according to the magnification ratio described later. For example, as illustrated in Figure 4, the circle of confusion diameter R1 at the image data generation distance X1 can be determined. Then, since image data is a collection of light points at the pixel level, distance change image data at the image data generation distance X1 can be generated by correcting the image data at the reading distance Xf, which is the best focus position (base image data), so that each pixel blurs according to the circle of confusion diameter R1, and then performing the scaling process described later (so-called filtering). Similarly, distance change image data at different image data generation distances Xk can be generated by correcting the image data at the reading distance Xf, which is the best focus position, so that each pixel blurs according to the circle of confusion diameter R at that image data generation distance Xk, and then performing the scaling process.

[0035] Furthermore, since the field of view of the imaging unit 23 is constant, in the above-described scaling process, as illustrated in Figure 5, the image data is scaled based on a scaling factor (reduction factor) that linearly increases or decreases according to the reading distance X, with the reading distance Xf, which is the best focus position, as the reference.

[0036] For example, as shown in Figure 6, since the information code C of the test work is at the reading distance Xf, which is the best focus position, we assume that image data in which information code C is not blurred is captured as the base image data, as shown in Figure 7(B) (Xo=Xf). In this case, the distance-changed image data at the image data generation distance X1 (see Figure 6), which is shifted towards the near point, is generated as illustrated in Figure 7(A) by first correcting each pixel of the base image data so that it is blurred according to the circle of confusion diameter R calculated based on the image data generation distance X1, and then enlarging it according to the magnification factor calculated based on the image data generation distance X1. Similarly, the distance-changed image data at the image data generation distance X2 (see Figure 6), which is shifted towards the far point, is generated as illustrated in Figure 7(C) by first correcting each pixel of the base image data so that it is blurred according to the circle of confusion diameter R calculated based on the image data generation distance X2, and then shrinking it according to the magnification factor calculated based on the image data generation distance X2.

[0037] In this way, when a predetermined number (e.g., 10) of distance-changing image data that gradually move away from the near point and a predetermined number (e.g., 10) of distance-changing image data that gradually move away from the far point are generated from the image data at the best focus position, the control unit 21 performs an evaluation process. In this evaluation process, the readability of each distance-changing image data is evaluated by the reading process, and a reading stability S is calculated for each image data generation distance Xk. The control unit 21 that performs the above evaluation process may correspond to an example of an "evaluation means".

[0038] This allows for the creation of a graph showing the reading stability S, which changes with the reading distance X. From this graph, the near-point limit distance Xt1 and the far-point limit distance Xt2 can be calculated as information regarding the allowable distance, as described above. The information regarding the allowable distance calculated in this way is then notified to the display unit 25 or the upper-level terminal 100 that receives this information via the communication unit 27, using a screen display or the like. The user who receives this notification can then determine the allowable distance at which the information code C can be read stably before actually transporting the workpiece W. The display unit 25 or the communication unit 27 may be considered an example of a "notification means" for notifying information regarding the allowable distance.

[0039] Furthermore, because the optical information reading device 10 does not have a focus adjustment mechanism, as illustrated in Figure 8, the information code C of the test workpiece may be imaged at a reference distance Xo that is shifted from the reading distance Xf, which is the best focus position, and the reading of this information code C may be successful. In this case, information regarding the reference distance Xo is acquired in response to an input operation by the operation unit 26 or instructions from the upper-level terminal 100 via the communication unit 27, and this information can be used to create a graph showing the reading stability S. The operation unit 26 or the communication unit 27 may correspond to an example of a "reference distance acquisition means" for acquiring the reference distance Xo.

[0040] Specifically, as described above, the degree of change in the circle of confusion diameter R related to the optical system of the imaging unit 23 can be known in advance, so the circle of confusion diameter Ro corresponding to the acquired reference distance Xo can be determined, as illustrated in Figure 9. Then, distance change image data at each image data generation distance Xk can be generated by correcting each pixel of the base image data so that it is blurred according to the circle of confusion diameter R calculated based on each image data generation distance Xk, and then scaling it up or down according to the magnification ratio calculated based on that image data generation distance Xk. When a graph showing the reading stability S is created from the multiple distance change image data generated in this way, the near-point limit distance Xt1 and the far-point limit distance Xt2 can be calculated from this graph as information regarding the allowable distance, as described above.

[0041] Even if information regarding the reference distance Xo is not obtained, the reference distance Xo can be calculated based on the circle of confusion diameter R determined from the degree of blurring of the base image data and a previously obtained graph of the circle of confusion diameter R. However, depending on the degree of blurring of the base image data, it is conceivable that not only will the accuracy of calculating the reference distance Xo be low, but the processing load related to generating distance-changing image data may also increase.

[0042] Therefore, as described above, by obtaining the reference distance Xo, it is easy to determine whether the base image data was captured at the focus distance or at a distance farther from the focus distance. Since the reference distance Xo is clearly defined in this way, the image data generation distance Xk at which multiple distance-changing image data should be generated becomes clearer compared to the case where the reference distance Xo is not obtained, thus reducing the processing load related to the generation of each distance-changing image data.

[0043] As described above, in the optical information reading device 10 according to this embodiment, when the distance between the imaging unit 23 and the information code C at the time of successful reading is set as the reference distance Xo and the image data at the time of successful reading is set as the base image data, a plurality of distance-changed image data are generated from the base image data, each with an image data generation distance Xk that is different from the reference distance Xo. Then, when the readability of each of the generated plurality of distance-changed image data is evaluated, the distance between the information code and the imaging unit 23 that is permissible for reading the information code is calculated as the permissible distance based on this evaluation result, and information regarding this permissible distance is notified.

[0044] This allows for the generation of multiple distance-change image data from a single base image data, without having to capture and generate image data each time the adjustment amount of the focus adjustment mechanism is changed. Therefore, it is possible to generate multiple distance-change image data without requiring a focus adjustment mechanism, and then calculate and notify the acceptable distance based on the evaluation results of each image data.

[0045] In particular, when the distance from the imaging unit 23 where distance-changing image data is created is defined as the image data generation distance Xk, multiple distance-changing image data are generated from the base image data based on the relationship between the distance from the best focus position of the imaging unit 23 and the circle of confusion diameter R, which is determined according to the image data generation distance Xk, the image data generation distance Xk, and the magnification factor of the image determined from the field of view of the imaging unit 23.

[0046] As described above, the degree of change in the circle of confusion diameter R of the imaging unit 23's optical system can be determined based on the configuration of that optical system. Therefore, distance-changing image data at a certain image data generation distance Xk can be generated by correcting the base image data so that each pixel is blurred according to the circle of confusion diameter R at the image data generation distance Xk, and then scaling it up or down according to the magnification ratio. By changing the image data generation distance Xk, multiple distance-changing image data can be generated from a single base image data.

[0047] Furthermore, when notifying the near-point limit distance Xt1 and far-point limit distance Xt2 as information regarding the permissible distance as described above, the near-point margin, which is the difference between the reference distance Xo and the near-point limit distance Xt1, may be calculated, and information regarding the calculated near-point margin may also be notified. Similarly, the far-point margin, which is the difference between the reference distance Xo and the far-point limit distance Xt2, may be calculated, and information regarding the calculated far-point margin may be notified together with the information regarding the permissible distance. This allows users who receive this notification to clearly understand not only the permissible distance but also the near-point margin and far-point margin. The near-point margin corresponds to the difference between the distance between the information code C and the imaging unit 23 that is actually captured and the closest distance between the information code C and the imaging unit 23 that is permissible for reading, and the far-point margin may correspond to the difference between the distance between the information code C and the imaging unit 23 that is actually captured and the furthest distance between the information code C and the imaging unit 23 that is permissible for reading.

[0048] Furthermore, the threshold condition setting process performed in the control unit 21 may be configured to set a predetermined threshold St for determining the near-point limit distance Xt1 and the far-point limit distance Xt2 in response to a predetermined operation on the operation unit 26. This allows the predetermined threshold St to be set to match the environment in which the optical information reading device 10 is employed.

[0049] In the threshold condition setting process described above, a predetermined threshold St may be set in response to instructions from an external device such as a higher-level terminal 100. This eliminates the need for the user to input setting values ​​to the operation unit 26 each time, thus improving convenience in setting the predetermined threshold St.

[0050] Furthermore, after the allowable distance etc. has been calculated as described above, during operation in which the workpiece W is sequentially transported along the transport path, the distance between the information code C captured by the imaging unit 23 and the imaging unit 23 is obtained using a distance sensor or the like. If the difference between this distance and the near-point limit distance Xt1 or far-point limit distance Xt2 of the allowable distance is less than or equal to a predetermined distance, a predetermined warning may be issued.

[0051] Specifically, for example, when the distance to information code C approaches the near-point limit distance Xt1, the display unit 25 can visually notify the user that information code C may not be able to be read stably because it is too close to the optical information reading device 10. This allows the user who has received the above-mentioned warning to change the distance from the imaging unit 23 to information code C in order to perform a stable reading. In particular, since the above-mentioned warning is notified visually, the level of the warning is also displayed, so the user who has received the above-mentioned warning can easily see not only whether there is a warning but also the level of the warning.

[0052] Furthermore, for example, if the distance to information code C approaches the far-point limit distance Xt2, a message to that effect is transmitted to the higher-level terminal 100 via the communication unit 27. This notifies the administrator or other person managing the higher-level terminal 100 that there is a possibility that information code C may not be able to be read stably because it is too far from the optical information reading device 10. This allows the administrator or other person to be prompted to change the reading distance or take other measures to ensure stable reading.

[0053] The present invention is not limited to the embodiments described above, and may be further embodied as follows, for example. (1) The present invention is not limited to being applied to an optical information reading device 10 that does not have a focus adjustment mechanism as described above, but may also be applied to an optical information reading device that has a focus adjustment mechanism. In this configuration, the base image data can be the image data obtained when reading is successful, with the reference distance Xo being the distance at which the imaging unit 23 is focused on the information code C by the focus adjustment mechanism. In this case, it can be determined that the base image data is image data in which the information code C is captured without blurring, and the image data generation distance Xk at which multiple distance change image data should be generated becomes clear, thus reducing the processing load related to the generation of each distance change image data.

[0054] (2) The present invention is not limited to being applied to an optical information reading device 10 that reads an information code C attached to a workpiece W being transported along a transport path, but may also be applied to a fixed optical information reading device that optically reads information codes attached to each moving body as it sequentially passes through predetermined imaging points.

[0055] (3) As a method for generating multiple distance-varying image data from base image data, the method of generating the image data using the degree of change of the circle of confusion diameter R described above is not limited to the method of generating the image data using other methods that reflect blurring and scaling for each image data generation distance Xk.

[0056] 10…Optical information reading device 21...Control unit (reading means, evaluation means, distance change image data generation means, allowable distance calculation means, threshold condition setting means) 23…Imaging unit (imaging means) 25...Display section (notification means) 26...Operation unit (reference distance acquisition means) 27...Communication department (notification means, reference distance acquisition means) 100... Higher-end device (external device) C... Information Code R...Diameter of confusion S... Readability (ease of reading) St... predetermined threshold (predetermined threshold condition) X... Reading distance Xk...Image data generation distance Xo... base distance Xt1…Peripheral limit distance (first distance) Xt2…Apocere limit distance (second distance) W...work

Claims

1. A fixed optical information reading device that optically reads information codes printed on a workpiece, Imaging means, The reading means decodes and reads the image data captured by the imaging means, When the distance between the imaging means and the information code at the time of successful reading by the reading means is taken as the reference distance and the image data at the time of successful reading is taken as the base image data, a distance change image data generation means generates a plurality of distance change image data obtained by changing the distance between the imaging means and the information code from the reference distance, each from the base image data. An evaluation means for evaluating the readability of each of the multiple distance change image data generated by the distance change image data generation means by the reading means, An allowable distance calculation means calculates the distance between the information code and the imaging means that is permissible to read the information code based on the evaluation result of the evaluation means, A notification means for notifying information regarding the allowable distance calculated by the allowable distance calculation means, An optical information reading device characterized by comprising the following:

2. The optical information reading device according to claim 1, characterized in that the allowable distance is calculated to be the distance at which the evaluation result by the evaluation means satisfies a predetermined threshold condition, and is between a first distance at which the distance between the information code and the imaging means is closest and a second distance at which the distance between the information code and the imaging means is farthest.

3. The optical information reading device according to claim 2, further comprising threshold condition setting means capable of setting the predetermined threshold conditions.

4. The optical information reading device according to claim 3, characterized in that the threshold condition setting means sets the predetermined threshold condition in response to an instruction from an external device.

5. The allowable distance calculation means calculates a near-point margin, which is the difference between the distance between the information code and the imaging means and the closest allowable distance between the information code and the imaging means for reading. The optical information reading device according to claim 1, characterized in that the notification means notifies information regarding the near-point margin calculated by the allowable distance calculation means.

6. The allowable distance calculation means calculates the far point margin, which is the difference between the distance between the information code and the imaging means and the furthest distance between the information code and the imaging means that is allowed for reading. The optical information reading device according to claim 1, characterized in that the notification means notifies information regarding the far point margin calculated by the allowable distance calculation means.

7. The imaging means includes a focus adjustment mechanism, The optical information reading device according to claim 1, characterized in that the base image data is image data obtained when reading is successful in a state where the reference distance is the distance at which the imaging means focuses on the information code by the focus adjustment mechanism.

8. The optical information reading device according to claim 1, further comprising a means for acquiring the aforementioned reference distance.

9. The optical information reading device according to claim 1, wherein the distance-changing image data generation means generates the plurality of distance-changing image data from the base image data, based on the distance from the imaging means where the distance-changing image data is created being defined as the image data generation distance, the circle of confusion diameter determined according to the image data generation distance from the relationship between the distance from the best focus position of the imaging means and the circle of confusion diameter, the image data generation distance and the magnification factor of the image determined from the field of view of the imaging means.

10. The optical information reading device according to claim 1, characterized in that the notification means notifies a predetermined warning when, after the allowable distance has been calculated by the allowable distance calculation means, the difference between the distance between the information code captured by the imaging means and the imaging means and the allowable distance becomes less than or equal to a predetermined distance.

11. The optical information reading device according to claim 10, characterized in that the notification means visually notifies the predetermined warning.

12. The optical information reading device according to claim 10, characterized in that the notification means notifies by transmitting the predetermined warning to an external device.

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