Optical information reading device

Abstract

To promptly read, in an optical information reading device, a symbol without an occurrence of a region that is difficult to read.SOLUTION: An imaging device includes a first fixed-focus camera 33, a second fixed-focus camera 34, and a variable-focus camera 35. A control device 20 reads information on a symbol 11 based on the first image of the first fixed-focus camera 33, the second image of the second fixed-focus camera 34, and the third image of the variable-focus camera 35. The control device 20 controls a focal length changing device 47 of the variable-focus camera 35 in such a way that the focal length of the variable-focus camera 35 becomes longer than the first focal length of the first fixed-focus camera 33, and becomes shorter than the second focal length of the second fixed-focus camera 34. The control device 20 reads the information on the symbol 11 based on a third image which is generated by the variable-focus camera 35 at the focal length having undergone the control, and which is in focus at a farther distance than the first image at a closer distance than the second image.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an optical information reader such as a handheld terminal. [Background technology]

[0002] An optical information reader is a device that captures an image of a symbol to be read and reads information from the captured image. The optical information reader described in Patent Document 1 irradiates an aiming light onto the symbol and then captures an image of the symbol.

[0003] Patent Document 1 discloses an optical information reading device that uses two cameras, a fixed-focus camera and an autofocus camera, and uses the autofocus camera when it is determined that imaging with the fixed-focus camera is inappropriate for reading symbols, thereby reducing the frequency of use of the autofocus camera and preventing an increase in imaging time and a shortening of its mechanical lifespan.

[0004] Patent Document 2 discloses an optical information reading device that uses four fixed-focus cameras to reduce deviations in the reading area. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-055005 [Patent Document 2] Japanese Patent Publication No. 2020-177306 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the optical information reading device described in Patent Document 1 performs sequential operations by activating a fixed-focus camera and then an autofocus camera, which poses the problem that processing takes a long time when it is determined that imaging using a fixed-focus camera is inappropriate for reading a symbol.

[0007] In the optical information reader described in Patent Document 2, even if the code or symbol is at the same distance, as the code size decreases, the distance range in which a decodable image can be generated narrows, which can result in areas that are difficult to read, i.e., gaps.

[0008] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an optical information reader that can quickly read symbols without creating any areas that are difficult to read. [Means for solving the problem]

[0009] In order to achieve this object, an optical information reader according to a first aspect of the present invention captures an image of a symbol to be read and reads information about the symbol, The imaging device includes: a first fixed focus camera including a first fixed focus optical system having a first focal length and configured to receive light incident on a symbol and reflected by the symbol, and a first image sensor configured to convert the light received by the first fixed focus optical system into an electrical signal to generate a first image; a second fixed focus camera including a second fixed focus optical system having a second focal length longer than the first focal length and receiving light incident on a symbol and reflected by the symbol; and a second image pickup element that converts the light received by the second fixed focus optical system into an electrical signal and generates a second image focused at a longer distance than the first image; a variable focus camera including a variable focus optical system having a variable focal length and configured to receive light incident on a symbol and reflected by the symbol, a third image pickup element configured to convert the light received by the variable focus optical system into an electrical signal to generate a third image, and a focal length change device configured to change the focal length of the variable focus optical system; and the optical information reader further includes a control device capable of reading symbol information based on the first image, the second image, and the third image; The control device controlling the focal length variation device so that the focal length of the variable-focus optical system is longer than the first focal length and shorter than the second focal length; and The information in the symbol is read based on the third image, which is generated by the variable-focus camera under the controlled focal length and is focused at a longer distance than the first image and a closer distance than the second image. [Effects of the Invention]

[0010] According to the optical information reader of the first aspect of the present invention, the variable-focus camera can read between the reading distance of the first fixed-focus camera for short distances and the reading distance of the second fixed-focus camera for long distances. This allows the overall readable distance range to be expanded without sacrificing the readable range on the short distance side by the first fixed-focus camera or the long distance side by the second fixed-focus camera. Furthermore, since processing by the fixed-focus camera and processing by the variable-focus camera do not need to be performed sequentially and can be performed simultaneously, symbol reading can be performed quickly. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a three-dimensional view illustrating the appearance of an optical information reader according to an embodiment of the present invention; [Figure 2] FIG. 2 is another three-dimensional view showing the appearance of the optical information reader. [Figure 3] FIG. 2 is a block diagram of the optical information reader. [Figure 4] 3 is a cross-sectional view showing the configuration of a focal length changing device in the optical information reading device. FIG. [Figure 5] 3A and 3B are diagrams illustrating examples of the arrangement of cameras and lighting elements of the optical information reader. [Figure 6] 10A and 10B are diagrams showing other examples of the arrangement of the camera and the lighting elements of the optical information reader. [Figure 7] 10 is a diagram showing still another example of the arrangement of the camera and the lighting elements of the optical information reader. FIG. [Figure 8] 3 is a diagram showing an example of an operating area of ​​a fixed-focus camera and an operating area of ​​a variable-focus camera in the optical information reader. FIG. [Figure 9] 10 is a diagram showing another example of the operating area of ​​the fixed-focus camera and the operating area of ​​the variable-focus camera in the optical information reader. FIG. [Figure 10] 10 is a diagram showing still another example of the operating area of ​​the fixed-focus camera and the operating area of ​​the variable-focus camera in the optical information reader. FIG. [Figure 11] 10 is a diagram showing still another example of the operating area of ​​the fixed-focus camera and the operating area of ​​the variable-focus camera in the optical information reader. FIG. [Figure 12] 10 is a diagram showing still another example of the operating area of ​​the fixed-focus camera and the operating area of ​​the variable-focus camera in the optical information reader. FIG. [Figure 13] 3 is a diagram showing the entire operating area of ​​a fixed-focus camera and the entire operating area of ​​a variable-focus camera in the optical information reader; FIG. [Figure 14] 10A and 10B are diagrams showing examples of an operating area of ​​a fixed-focus camera and an operating area of ​​a variable-focus camera in an optical information reading device that is not an embodiment of the present invention. [Figure 15] FIG. 10 is a diagram showing the entire operating area of ​​a fixed-focus camera in another optical information reading device that is not an embodiment of the present invention. [Figure 16] FIG. 10 is a diagram showing the entire operating area of ​​a fixed-focus camera in still another optical information reading device that is not an embodiment of the present invention. [Figure 17]FIG. 10 is a diagram showing the entire operating area of ​​a fixed-focus camera in still another optical information reading device that is not an embodiment of the present invention. [Figure 18] FIG. 4 is an enlarged view of a main part in FIG. 3. [Figure 19] 3 is a flowchart showing the operation of the optical information reader according to the embodiment of the present invention. [Figure 20] 4 is a time chart showing the operation of the optical information reader. [Figure 21] FIG. 10 is a diagram illustrating data processing of images from a fixed-focus camera and an image from a variable-focus camera by multiple cores. [Figure 22] FIG. 10 is another diagram showing how multiple cores process data of images from a fixed-focus camera and images from a variable-focus camera. DETAILED DESCRIPTION OF THE INVENTION

[0012] 1 and 2 are three-dimensional diagrams showing the appearance of an example of an optical information reading device according to an embodiment of the present invention. The optical information reading device is a terminal device for reading symbols such as barcodes and two-dimensional codes. The optical information reading device includes not only a handheld scanner that reads and outputs symbols, but also an optical information reading device 10 having a handheld terminal structure as shown in the figure that performs any data processing such as registering the read information and data collation, and a business PDA.

[0013] The symbol 11 (Figure 1) to be read can be a standardized code such as a barcode or two-dimensional code, or a proprietary code, as well as a string of characters consisting of letters and numbers. These symbols are printed directly on the product to be read, on the surface of the shelf that stores the product, or on a label affixed to the surface of the product. Reading a symbol generally means decoding the information encoded in the symbol. As a special case, when the symbol is a string of characters, reading the symbol means optical character recognition (OCR) of the letters and numbers.

[0014] The optical information reader 10 having the configuration of a handheld terminal shown in the figure has a racket-shaped casing 12 that is elongated in one direction. An imaging module 13 is provided at the tip of the casing 12 as an imaging device for optically reading the symbol 11 to be read. Details of the imaging module 13 will be described later.

[0015] A display 14 is provided on one end of the casing 12, and a key arrangement section 15 is provided on the other end of the casing 12 on the top surface thereof. The display 14 is provided in a display section 16 of the optical information reader 10, and the key arrangement section 15 is provided in a grip section 17. A user who operates the optical information reader 10 holds the grip section 17 in his / her hand and operates each operation key of the key arrangement section 15 arranged on the grip section 17 while referring to the contents displayed on the display 14 provided on the display section 16. The display section 16 of the casing is wide, and the grip section 17 is narrow. This makes it easy for the user to hold the grip section 17.

[0016] The display 14 displays various information such as an image of the symbol 11 to be read captured by the imaging module 13, decoded information from the symbol 11, and other setting information. The display 14 is configured, for example, as a liquid crystal display (LCD) or an organic EL display. The display 14 may be configured as a touch panel. The display 14 configured as a touch panel also functions as a key input unit.

[0017] The key arrangement unit 15 has a plurality of operation keys arranged thereon, such as a numeric keypad for performing various operations, a power key, and function keys. The optical information reader 10 is provided with a trigger key 18. When the operator operates the trigger key 18, the timing of data collection for collecting information about the symbol 11 is determined. That is, when the imaging module 13 detects that the trigger key 18 has been operated, it starts an imaging process. In the imaging process, the imaging module 13 receives light that is incident on the symbol 11 to be read and reflected by this symbol 11, converts it into an electrical signal, and generates image data. That is, the trigger key 18 determines the trigger signal. The trigger key 18 is not limited to a physical key and may be, for example, a virtual key displayed on a user interface.

[0018] Fig. 3 is a block diagram of the optical information reader 10. As shown in Fig. 3, the optical information reader 10 includes the above-mentioned imaging module 13, the above-mentioned display 14, the above-mentioned trigger key 18, a control device 20 such as a CPU that controls the operation of the optical information reader 10, a RAM 21, and a ROM 22.

[0019] The control device 20 is connected to the above-mentioned hardware components of the optical information reader 10 via an internal system bus 26 or the like. The control device 20 thereby controls the operation of the above-mentioned hardware components and executes various software functions in accordance with a computer program 23 and firmware 24 stored in a ROM 22. Such a control device 20 can be suitably realized by a CPU, MPU, SoC, ASIC, or the like. The RAM 21 is composed of a volatile memory such as an SRAM or SDRAM, into which a load module is expanded when a computer program is executed, and stores temporary image data 25 generated when the computer program is executed, i.e., "image data 1," "image data 2," ..., "image data n," etc.

[0020] In addition to the internal system bus 26 described above, the control device 20 also includes a plurality of cores 27 and image capture interfaces 28 , 29 , and 30 for acquiring images from the camera provided in the imaging module 13 .

[0021] The configuration of imaging module 13 as an imaging device will be described. Imaging module 13 has a first fixed-focus camera 33, a second fixed-focus camera 34, and a variable-focus camera 35. Imaging module 13 also has an illumination device 36 for fixed-focus cameras 33 and 34, an illumination device 37 for variable-focus camera 35, and an aiming light irradiation device 38.

[0022] The first fixed-focus camera 33 has a fixed focus configuration and includes a first fixed-focus optical system 40 and a first image sensor 41. The first fixed-focus optical system 40 has a fixed first focal length. The first fixed-focus optical system 40 receives light reflected by the symbol 11 in FIG. 1 when light emitted from the illumination device 36 is incident on the symbol 11. The first image sensor 41 converts the light received by the first fixed-focus optical system 40 into an electrical signal to generate a first image. Image data of the first image is sent to the control device 20, captured by the image capture interface 28 of the control device 20, and stored in the RAM 21 as image data 25.

[0023] The second fixed-focus camera 34 has a similar configuration to the first fixed-focus camera 33. That is, the second fixed-focus camera 34 has a fixed focus configuration and includes a second fixed-focus optical system 42 and a second imaging element 43. The second fixed-focus optical system 42 has a fixed second focal length. The fixed second focal length of the second fixed-focus optical system 42 is longer than the fixed first focal length of the first fixed-focus optical system 40. That is, the second fixed-focus camera 34 with the second fixed-focus optical system 42 has a longer focal length than the first fixed-focus camera 33 with the first fixed-focus optical system 40, and therefore can capture an image of a symbol 11 located farther away than the imageable range of the first fixed-focus camera 33. Conversely, the first fixed-focus camera 33 with the first fixed-focus optical system 40 has a shorter focal length than the second fixed-focus camera 34 with the second fixed-focus optical system 42, and therefore can capture an image of a symbol 11 located closer than the imageable range of the second fixed-focus camera 34.

[0024] The second fixed-focus optical system 42 of the second fixed-focus camera 34 receives light reflected by the symbol 11 in FIG. 1 when light emitted from the lighting device 36 is incident on the symbol 11. The second imaging element 43 converts the light received by the second fixed-focus optical system 42 into an electrical signal to generate a second image. Image data of the second image is sent to the control device 20, captured by the image capture interface 29 of the control device 20, and stored in the RAM 21 as other image data 25.

[0025] The variable-focus camera 35 has a variable focal length. That is, the variable-focus camera 35 includes a variable-focus optical system 45, a third image sensor 46, and a focal length changer 47. The variable-focus optical system 45 receives light reflected by the symbol 11 in FIG. 1 when light emitted from the lighting device 37 is incident on the symbol 11. The third image sensor 46 converts the light received by the variable-focus optical system 45 into an electrical signal to generate a third image. Image data of the third image is sent to the control device 20, captured by the image capture interface 30 of the control device 20, and stored in the RAM 21 as further image data 25.

[0026] The focal length changer 47 changes the focal length of the variable-focus optical system 45. Any configuration can be adopted for the focal length changer 47 for changing the focal length of the variable-focus optical system 45. For example, the focal length changer 47 can be configured as a device for changing the focal position of the variable-focus optical system 45. In that case, the focal length of the variable-focus optical system 45 is changed by changing the position of the lens that makes up the optical system 45 along the optical axis, thereby changing the focal position. The focal length changer 47 is driven and controlled by the control device 20.

[0027] A specific example of the focal length changer 47 is shown in FIG. 4. In the example of FIG. 4, the focal length changer 47 provided in the variable-focus camera 35 includes a voice coil motor (VCM) 49 as a mechanism for mechanically moving the lens unit 48 of the variable-focus optical system 45 along its optical axis. The variable-focus optical system 45, including the lens unit 48, and the third image sensor 46 are disposed inside a casing 50 of the variable-focus camera 35. The lens unit 48 is held by a holder 51, which is supported on the casing via a spring 52 such as a disc spring. The voice coil motor 49 includes a coil 53 provided in the holder 51 and a magnet 54 attached to the casing 50 and disposed opposite the coil 53. When a current is applied to the coil 53, the coil 53 receives a force from the magnet 54. When the force acting on the coil 53 becomes greater than the force of the spring 52, the lens unit 48 is mechanically moved along its optical axis. The variable-focus optical system 45 may be a liquid lens or a deformable lens whose focal length can be adjusted by applying force to a layer made of a flexible material (for example, a thin glass layer).

[0028] The first imaging element 41 of the first fixed-focus camera 33 and the second imaging element 43 of the second fixed-focus camera 34 are both global shutter image sensors using CMOS. In other words, the first fixed-focus camera 33 and the second fixed-focus camera 34 are both called scan camera modules. In contrast, the third imaging element 46 of the varifocal camera 35 is a rolling-shutter color image sensor. In other words, the varifocal camera 35 is called a color camera module.

[0029] By making the range of view of the first and second fixed-focus cameras 33, 34 different from the range of view of the variable-focus camera 35, it is possible to capture an image of a wider range in a single operation.

[0030] The aiming light emitting device 38 emits aimer light. An image captured by any of the cameras 33, 34, 35 after the aimer light is emitted by the aiming light emitting device 38 is called an aimer image.

[0031] The first fixed-focus camera 33, the second fixed-focus camera 34, the variable-focus camera 35, the lighting device 36, the lighting device 37, and the aiming light emitting device 38 may be arranged arbitrarily in the imaging module 13. For example, as shown in Figures 5 and 6, the first fixed-focus camera 33, the second fixed-focus camera 34, the variable-focus camera 35, the lighting device 36, the lighting device 37, and the aiming light emitting device 38 may be arranged in a straight line along the window 55 formed in the imaging module 13 shown in Figures 1 and 2.

[0032] 5, the second fixed-focus camera 34, the aiming light irradiation device 38, the first fixed-focus camera 33, the lighting device 36 for the fixed-focus cameras 33 and 34, the variable-focus camera 35, and the lighting device 37 for the variable-focus camera 35 are arranged in this order on a straight line. By arranging them on a straight line in this manner, the imaging module 13 can be made thin.

[0033] 6, the second fixed-focus camera 34, the lighting device 36 for the fixed-focus cameras 33 and 34, the first fixed-focus camera 33, the aiming light irradiation device 38, the variable-focus camera 35, and the lighting device 37 for the variable-focus camera 35 are arranged in this order on a straight line. In this case, too, by arranging them on a straight line as in the example of FIG. 5, the imaging module 13 can be configured to be thin.

[0034] 7 shows an example of an arrangement that prioritizes the performance of the imaging module 13 over the thinness of the imaging module 13. In the example of Fig. 7, the aiming light emitting device 38 is placed in the center of the window 55, and the first fixed-focus camera 33, the second fixed-focus camera 34, the illumination device 37 for the varifocal camera 35, the varifocal camera 35, and the illumination device 36 for the fixed-focus cameras 33 and 34 are arranged in this order to surround the aiming light emitting device 38. Such a configuration in which the aiming light emitting device 38 is placed in the center can improve the accuracy of reading the symbol 11 aimed at by the optical information reader shown in Fig. 1.

[0035] The provision of the first fixed-focus camera 33, the second fixed-focus camera 34, which has a longer focal length than the first fixed-focus camera, and the varifocal camera 35 has the following advantage: Between a first region within a first distance range from the first fixed-focus camera 33 where the first fixed-focus camera 33 can read the symbol 11, and a second region within a second distance range from the second fixed-focus camera 34 where the second fixed-focus camera 34 can read the symbol 11, there may be a third region where the symbol 11 cannot be read by either the first fixed-focus camera 33 or the second fixed-focus camera 34. In this case, the symbol 11 can be read in the third region by controlling the focal length of the varifocal camera 35 to be within this region. As a result, the symbol 11 can be read over a wide area.

[0036] 8 to 12 are diagrams in which the horizontal axis represents the distance from the optical information reader 10 to the symbol, and the vertical axis represents the code size of the symbol 11 that is the target to be read by the optical information reader 10.

[0037] In Figures 8 to 12, the first readable area 56, which is the area in which the code of symbol 11 can be read by the first fixed focus camera 33, the second readable area 57, which is the area in which the code of symbol 11 can be read by the second fixed focus camera 34, and the third readable area 58, which is the area in which the code of symbol 11 can be read by the variable focus camera 35, are all areas above the first limit line 59, second limit line 60, and third limit line 61, which are V-shaped with a bottom, in Figures 8 to 12.

[0038] In each of the readable areas 56, 57, 58, at or near the focal distance of the cameras 33, 34, 35, the limit lines 59, 60, 61 correspond to the bottom portions 62, 63, 64 of the V-shaped base. That is, at or near the focal distance of the cameras 33, 34, 35, even symbols 11 with small code sizes can be read. In contrast, as the distance from the focal distance of the cameras 33, 34, 35 increases, the limit lines 59, 60, 61 correspond to a pair of inclined portions 65, 66, 67 and 68, 69, 70 of the V-shaped base. That is, the readable code size gradually increases with increasing distance from the focal distance of the cameras 33, 34, 35. That is, the further the distance from the focal distance of the cameras 33, 34, 35, the smaller the code size becomes, becoming increasingly unreadable.

[0039] 8 to 12, the bottom portions 62, 63, 64 of the bottomed V-shaped limit lines 59, 60, 61 are inclined gently upward to the right as they move away from the cameras 33, 34, 35. This corresponds to the phenomenon where the minimum readable code size gradually increases as the distance from the cameras 33, 34, 35 increases.

[0040] 8 to 12, a bottom portion 62 of the first limit line 59 of the first fixed focus camera 33 is located at a distance closer to the optical information reader 10. In contrast, a bottom portion 63 of the second limit line 60 of the second fixed focus camera 34 is located at a distance farther from the optical information reader 10 than the bottom portion 62 of the first limit line 59 of the first fixed focus camera 33. This corresponds to the fact that the second fixed focal length of the second fixed focus optical system 42 of the second fixed focus camera 34 is longer than the first fixed focal length of the first fixed focus optical system 40 of the first fixed focus camera 33.

[0041] As described above, the first limit line 59 defining the first readable area 56, which is the area where the code of the symbol 11 can be read by the first fixed focus camera 33, and the second limit line 60 defining the second readable area 57, which is the area where the code of the symbol 11 can be read by the second fixed focus camera 34, are both V-shaped with a bottom. Therefore, between the first readable area 56 and the second readable area 57 along the horizontal axis in Figures 8 to 12, there is an unreadable area 72 in which the small code-sized symbol 11 that can be read at the bottom portion 62 of the first limit line 59 of the first fixed focus camera 33 or the bottom portion 63 of the second limit line 60 of the second fixed focus camera 34 cannot be read by the first fixed focus camera 33 or the second fixed focus camera 34. This unreadable area 72 is an upwardly pointed triangular area in Figures 8 to 12.

[0042] The variable focus camera 35 equipped with the variable focus optical system 45 is capable of reading small code-sized symbols 11 that can be read at the bottom portion 62 of the first limit line 59 of the first fixed focus camera 33 and the bottom portion 63 of the second limit line 60 of the second fixed focus camera 34 in the unreadable area 72 that cannot be read by the first fixed focus camera 33 and the second fixed focus camera 34.

[0043] 10 shows a state where the focal length of the variable-focus optical system 45 of the variable-focus camera 35 is set to an intermediate value between the focal length of the first fixed-focus camera 33 and the focal length of the second fixed-focus camera 34. In this case, the third readable area 58 of the variable-focus camera 35 is located in a portion along the horizontal axis of FIG. 10 between the first readable area 56 of the first fixed-focus camera 33 and the second readable area 57 of the second fixed-focus camera 34, i.e., a portion corresponding to the unreadable area 72. In other words, the bottom portion 64 of the third limit line 61 of the third readable area 58 of the variable-focus camera 35 is located in a portion along the horizontal axis of FIG. 10 between the bottom portion 62 of the first limit line 59 that defines the first readable area 56 and the bottom portion 63 of the second limit line 60 that defines the second readable area 57.

[0044] This allows the variable focus camera 35 to read the symbol 11 in the unreadable area 72 where the fixed focus cameras 33, 34 cannot read the symbol 11. As a result, the symbol 11 located close to the optical information reader 10 can be read by the first fixed focus camera 33, the symbol 11 located far from the optical information reader 10 can be read by the second fixed focus camera 34, and the symbol 11 located between the close and far positions can be read by the variable focus camera 35. Therefore, the optical information reader 10 can reliably read all of the symbols 11 that exist over a wide range of distances from the optical information reader 10.

[0045] Depending on how the first to third readable areas 56, 57, 58 are set, it may be possible to reliably read all of the symbols 11 present over a wide range of distances from the optical information reader 10, as described above, using only the first and second readable areas 56, 57 and the third readable area 58 at the changed focal length set by the variable-focus camera 35. However, if the first to third readable areas 56, 57, 58 are not set to a very wide range or cannot be set, narrow but similar unreadable areas 73 and 74 may occur at least either between the first readable area 56 and the third readable area 58 or between the second readable area 57 and the third readable area 58, as shown in Fig. 10.

[0046] In that case, as shown in Fig. 9, by making the focal length of varifocal camera 35 slightly shorter than in Fig. 10, third readable area 58 can be moved closer to first readable area 56 along the horizontal axis of the figure. This can eliminate the occurrence of unreadable area 73. Similarly, as shown in Fig. 11, by making the focal length of varifocal camera 35 slightly longer than in Fig. 10, third readable area 58 can be moved closer to second readable area 57 along the horizontal axis of the figure, which can eliminate the occurrence of unreadable area 74.

[0047] The variable-focus camera 35 has a wide variable range of focal length, so that the focal length can be set shorter than that of the first fixed-focus camera 33 and longer than that of the second fixed-focus camera 34.

[0048] 8 shows the distribution of first to third readable areas 56, 57, 58 when the focal length of the variable-focus camera 35 is set shorter than the focal length of the first fixed-focus camera 33. As shown in the figure, the third readable area 58 of the variable-focus camera 35 is located closer to the optical information reader 10 than the first readable area 56 of the first fixed-focus camera 33.

[0049] 12 shows the distribution of first to third readable areas 56, 57, 58 when the focal length of variable-focus camera 35 is set longer than the focal length of second fixed-focus camera 34. As shown in the figure, third readable area 58 of variable-focus camera 35 is located farther from optical information reader 10 than second readable area 57 of second fixed-focus camera 34.

[0050] 9 to 11, the width of the readable area by optical information reader 10 along the horizontal axis of the diagram can be increased compared to when third readable area 58 of variable-focus camera 35 is simply set between first readable area 56 of first fixed-focus camera 33 and second readable area 57 of second fixed-focus camera 34. In other words, compared to when the displacement area of ​​third readable area 58 based on a change in focal length of variable-focus camera 35 is only set between first readable area 56 of first fixed-focus camera 33 and second readable area 57 of second fixed-focus camera 34, symbols 11 present at positions with a wider range of distances from optical information reader 10 can be reliably read.

[0051] Fig. 13 shows the entire range of readable areas 56, 57, 58 by first fixed-focus camera 33, second fixed-focus camera 34, and variable-focus camera 35 when the focal length of variable-focus camera 35 is changed as shown in Figs. 8 to 12. In detail, readable area 58 by variable-focus camera 35 is a range corresponding to each changed focal length of variable-focus camera 35, but Fig. 13 shows the entire range of third readable area 58 that can be set by variable-focus camera 35. It can be seen from Fig. 13 that the provision of variable-focus camera 35 expands the readable area by adding third readable area 58 by variable-focus camera 35 to first readable area 56 by first fixed-focus camera 33 and second readable area 57 by second fixed-focus camera 34.

[0052] Operating the varifocal camera 35 requires operations such as changing the focal length, which makes the operation more complicated. However, there is a first readable area 56 by the first fixed-focus camera 33 and a second readable area 57 by the second fixed-focus camera 34, and it is not necessary to operate the varifocal camera 35 in the range where these first readable area 56 and second readable area 57 exist. This makes it possible to improve operability and controllability compared to, for example, operating only the varifocal camera 35 over the entire range.

[0053] For example, as shown in FIG. 14, it is possible to set a readable area 76 by a single fixed-focus camera and a readable area 77 by a single variable-focus camera. However, in this case, the ranges of the readable areas 76 and 77 are significantly narrower than when two fixed-focus cameras 33 and 34 are provided, as shown in FIG. 13. It is, of course, possible to set a wider readable area 77 by the variable-focus camera so that the range of the readable area does not become narrower. However, in this case, as in the above case, it would be necessary to frequently change the focal length of the variable-focus camera 35 to operate it. This would correspondingly reduce the operability and controllability of the variable-focus camera 35.

[0054] As shown in Fig. 15, by installing four fixed-focus cameras with different focal lengths, the range of the readable area 80 can be expanded to the same range as in Fig. 13. However, in this case, there will be an excessive number of fixed-focus cameras, which can cause problems such as a complicated device configuration, reduced controllability when operating the cameras, and an excessive amount of data to be processed from each camera.

[0055] To solve this problem, the number of fixed-focus cameras can be increased to three, as shown in Fig. 16. However, in that case, the range of the readable area 80 will be narrowed as shown in the figure. In Fig. 16, in contrast to the case of Fig. 15, an unreadable area 81 occurs on the farther side from the optical information reader 10.

[0056] To solve the problem of the occurrence of the unreadable area 81 shown in Fig. 16, it is possible to widen the range of the readable area 80 by greatly differentiating the focal lengths of the three fixed-focus cameras, as shown in Fig. 17. However, in that case, an unreadable area 81 will occur between the readable areas 80 of adjacent fixed-focus cameras, as shown in the figure.

[0057] In the end, none of the means shown in Figures 14 to 17 can provide the advantages of providing the first fixed focus camera 33, second fixed focus camera 34, and variable focus camera 35 as described above.

[0058] In the above embodiment, the third readable area 58 of the variable-focus optical system changes mainly to fill the unreadable area 72 between the first readable area 56 by the first fixed-focus camera 33 and the second readable area 57 by the second fixed-focus camera 34. In contrast to this, a modified example is also conceivable in which the fixed-focus camera having the readable area 80 on the right end shown in Fig. 16 is replaced with a variable-focus camera, and the variable-focus camera reads the unreadable area 81 that occurs on the far side from the optical information reader 10.

[0059] However, in this case, the readable areas 80 of the multiple fixed-focus cameras are adjacent to each other, so the overlapping degree of the readable areas 80 of the multiple fixed-focus cameras must be increased to reduce the unreadable area 81, which shortens the readable distance. Also, by positioning the readable range of the varifocal camera farther away than the multiple fixed-focus cameras, the angle of view becomes relatively narrow. As a result, when the varifocal camera attempts to read a closer code, the upper limit of the angle of view increases the possibility that the code will not fit into the field of view.

[0060] Even when the readable range of the varifocal camera is positioned closer than the multiple fixed-focus cameras, the degree of overlap of the readable areas 80 of the multiple fixed-focus cameras must be increased to reduce the unreadable area 81, which shortens the readable distance. Also, by positioning the readable range of the varifocal camera closer than the multiple fixed-focus cameras, the angle of view becomes relatively wider. However, this increases the possibility that the resolution will be insufficient due to the lower limit of the angle of view when the varifocal camera attempts to read a code on the far side.

[0061] A method for processing image data acquired by the fixed-focus cameras 33, 34 and the variable-focus camera 35 by the control device 20 will be described. FIG. 18 is an enlarged view of the main parts of FIG. 3. As shown in FIGS. 3 and 18, the control device (CPU) 20 is made up of multiple cores 27, 27, .... Different cores 27 are assigned to the first fixed-focus camera 33, the second fixed-focus camera 34, and the variable-focus camera 35, respectively. As a result, processing of images from the first fixed-focus camera 33, the second fixed-focus camera 34, and the variable-focus camera 35 is simultaneously performed by the individual cores 27, 27, ....

[0062] FIG. 19 is a flowchart for explaining a method for reading image data by the control device 20. In FIG.

[0063] 1 and 2 is provided with a trigger key 18 (see FIGS. 1 to 3) that is operated by an operator when starting use of the device 10. In step S1 of FIG. 19, when the operator operates the trigger key 18, aiming light, i.e., aimer light, is irradiated from the aiming light irradiating device 38 of FIG. 3 toward the object to be read (step S2).

[0064] During the first reading process after the trigger key 18 is operated, the focal length of the variable-focus camera 35 is set to a predetermined distance between the focal length of the first fixed-focus camera 33 and the focal length of the second fixed-focus camera 34, as shown in Fig. 10. If it is not set to that distance, it is set to that distance by the focal length change device 47. Hereinafter, the focal length position of this variable-focus camera 35 will be referred to as the "predetermined focus position," and the data for this can be stored or memorized in the ROM 22 or RAM 21 shown in Fig. 3.

[0065] In step S3, it is determined whether it is necessary to move the focal length position of the varifocal camera 35 to a position other than the predetermined focus position. However, as described above, during the first reading process after the trigger key 18 is operated, the focal length of the varifocal camera 35 is set to a predetermined distance between the focal length of the first fixed-focus camera 33 and the focal length of the second fixed-focus camera 34, as shown in FIG. 10. Therefore, during the first reading process after the trigger key 18 is operated, it is determined that movement is not necessary, and the process proceeds to step S4. In step S4, the aimer light irradiated in step S2 is turned off. This is because the aimer light is not necessary during the reading process of the symbol 11.

[0066] As will be described in detail later, if the symbol 11 cannot be read in the first reading process after the trigger key 18 is operated, the process returns to step S2, the aimer light is irradiated again, and step S3 is executed again. In this case, based on the fact that the symbol 11 could not be read, it is determined in step S3 that the focal length position of the varifocal camera 35 needs to be moved to a position other than the predetermined focus position.

[0067] As a result, the process proceeds to step S5, where the aimer light reflected from the symbol 11 is captured by one of the three cameras 33, 34, and 35. This allows the distance to the symbol 11 to be measured as described below. Note that when measuring distance using aimer light in this way, it is necessary for the aimer to be captured fairly clearly in the camera image. It is also necessary for the entire aimer to be within the field of view of the camera.

[0068] In step S6, the distance to the symbol 11 is measured from the captured aimer light image. The aimer light image can be acquired by at least one of the three cameras 33, 34, and 35. For example, since there is a fixed relationship between the distance to the symbol 11 and an output value, such as an output voltage, of the image acquired by the aimer light, by storing this relationship, the distance to the symbol 11 can be measured from the output value of the acquired image. Alternatively, there is a fixed relationship between the lateral position of the symbol 11 in the image acquired by the aimer light and the output value of the acquired image, by storing this relationship, the distance to the symbol 11 can be measured from the output value of the acquired image. Alternatively, the distance to the symbol 11 can be measured using a time-of-flight method, or the distance to the symbol 11 can be measured by adjusting the focus using the contrast of the image. The distance to the symbol 11 can also be estimated using a phase difference method. In short, any method can be used to measure the distance to the symbol 11.

[0069] In the next step S7, the focal length of the varifocal camera 35 is changed based on the measured distance to the symbol 11. Then, the process proceeds to step S4, where the aimer light is turned off. Although not shown in detail, the control device 20 includes a focus determination unit for determining the focal length of the varifocal camera 35. The control device 20 then drives the focal length change device 47 so that the focal length of the varifocal camera 35 becomes the focal length determined by the focus determination unit.

[0070] Thereafter, in step S8 and subsequent steps, the reading of the symbol 11 is performed. First, in step S8, the lighting devices 36 and 37 for the cameras 33, 34, and 35 are turned on to irradiate the symbol 11 with illumination light. It is optional whether to use both of the lighting devices 36 and 37 or just one of them. The manner in which they are used may be manually set by the operator of the optical information reading device 10, or may be set automatically according to the brightness of the area.

[0071] As described above, the first imaging element 41 of the first fixed-focus camera 33 and the second imaging element 43 of the second fixed-focus camera 34 are both global shutter image sensors using CMOS, and the third imaging element 46 of the varifocal camera 35 is a rolling shutter color image sensor. In other words, the first fixed-focus camera 33 and the second fixed-focus camera 34 are both referred to as scan camera modules. The varifocal camera 35 is referred to as a color camera module. Correspondingly, the illumination devices 36 and 37 emit multiple or single pulsed lights as illumination light.

[0072] Once the illumination light is irradiated onto the symbol 11, in steps S9, S10, and S11, imaging processing is simultaneously performed by the three cameras 33, 34, and 35. This imaging processing can be performed, for example, by sending an imaging trigger signal from the control device 20 to each of the cameras 33, 34, and 35.

[0073] FIG. 20 shows a timing chart corresponding to steps S4, S8, S9, S10, and S11 in FIG. 19. The illumination device 36 for a fixed-focus camera shown in FIG. 3 exhibits the light-emitting characteristics shown in FIG. 20. That is, as described above, the scan camera module is a global shutter type, so all pixels of the image sensor are exposed simultaneously, and the exposure time is relatively short. For this reason, the illumination device 36 for a fixed-focus camera is required to emit a large amount of light instantaneously. This is shown in the timing chart in FIG. 20, and the illumination device 36 for a fixed-focus camera tends to instantaneously increase its initial rise.

[0074] In Fig. 20, the light emission characteristics of the aiming light emitting device 38, i.e., the light emission characteristics of the aimer light, are shown next to the lighting device 36 for the fixed focus camera. As shown in the flowchart of Fig. 19, the aimer light is turned off in step S4 and then the lighting device 36 for the fixed focus camera is turned on, and this is shown in the timing chart of Fig. 20.

[0075] 20, after the timing chart of the aimer light, the operation of the scan camera module, i.e., the CMOS serving as the first image sensor 41 of the first fixed-focus camera 33, is shown. The first image sensor 41 is exposed to light in response to light emission from the illumination device 36 to form an image (step S9 in FIG. 19), and the formed image is transferred to the control device (CPU) 20 shown in FIG. 3 and stored in the RAM 21. Similarly, the CMOS serving as the second image sensor 43 of the second fixed-focus camera 34 is also exposed to light in response to light emission from the illumination device 36 to form an image (step S10 in FIG. 19), and the formed image is transferred to the control device (CPU) 20 shown in FIG. 3 and stored in the RAM 21.

[0076] 20, following the time chart for the second image sensor 43 of the second fixed-focus camera 34, there are shown, in that order, a time chart for the operation of the illumination device 37 for the varifocal camera, a time chart for the operation of the varifocal optical system 45 of the varifocal camera 35, and a time chart for the operation of the CMOS, which is the third image sensor 46 of the varifocal camera 35. As shown in the figure, the varifocal optical system 45 starts operating before the illumination device 37 is turned on, and the illumination device 37 is turned on simultaneously with the illumination device 36.

[0077] The operation of the CMOS, which is the third image sensor 46 of the varifocal camera 35, will be described in detail. The varifocal camera 35, also known as a color camera module, uses a rolling shutter for the third image sensor 46, which results in a timing difference between the first and last rows. Therefore, if the illumination device 36 for the fixed-focus cameras 33 and 34 receives a momentary large amount of light, the difference in brightness between the first and last rows in the image captured by the third image sensor 46 will be large. To avoid this, as shown in FIG. 20, the start of exposure by the third image sensor 46, i.e., the start of operation of the third image sensor 46, is delayed until a predetermined period of time has elapsed, during which the illumination device 36 for the fixed-focus cameras 33 and 34's momentary rise ends and the light intensity stabilizes. With this slight delay, the third image sensor 46 is exposed to light emitted by the illumination device 37 to form an image (step S11 in FIG. 19). The formed image is then transferred to the control device (CPU) 20 shown in FIG. 3 and stored in RAM 21.

[0078] Next, in step S12 of FIG. 19, decoding processing of the image data stored in RAM 21 begins. Specifically, in the control device (CPU), a core 27 is assigned to each of the cameras 33, 34, and 35, and parallel decoding processing is performed by these multiple cores 27, 27, .... That is, image processing, i.e., decoding processing, is performed simultaneously on the image data acquired by each of the cameras 33, 34, and 35. FIG. 21 shows an example of such decoding processing. The horizontal direction in the figure represents time. Here, decoding processing 82 for the image from the first fixed-focus camera 33, decoding processing 83 for the image from the second fixed-focus camera 34, and decoding processing 84 for the image from the varifocal camera 35 are started simultaneously. Since the exposure times of the cameras 33, 34, and 35 are usually different, the time required for storing the images in RAM 21 and the timing at which the decoding of the images acquired by each of the cameras 33, 34, and 35 begins also differ.

[0079] Then, in step S13 of Fig. 19, it is determined whether the decoding was successful. For example, Fig. 21 shows an example in which decoding failed from the image data of the first fixed-focus camera 33 and also failed from the image data of the varifocal camera 35, but decoding was successful from the image data of the second fixed-focus camera 34. In this way, if even one decoding is successful, it is determined in step S13 that the decoding was successful.

[0080] As a result, the image of the symbol 11 is successfully read as shown in step S14, and the process ends in step S15.

[0081] If it is determined in step S13 that decoding has failed for image data from all cameras 33, 34, and 35, it is determined that "decoding has failed" and step S16 is executed. In step S16, the brightness of the image captured by the camera is calculated and the exposure time for the next re-exposure is calculated. After that, the process returns to step S2 and repeats the same process. At this time, if it is determined that "decoding has failed" in step S13, step S16 and the next focus process thereafter are performed without waiting for the completion of the decoding process. This allows for rapid processing.

[0082] 22 shows an example of a decoding process where decoding is successful after multiple iterations, where decoding processes 82, 83, and 84 of images captured by cameras 33, 34, and 35 are performed simultaneously and repeatedly.

[0083] In the second and subsequent processing iterations, in step S3, it is determined that it is necessary to move the focal length position of the varifocal camera 35 to a position other than the predetermined focus position, based on the fact that the symbol 11 could not be read as described above. In this case, steps S5, S6, and S7 are executed as described above, and then the process proceeds to step S4.

[0084] As described above, during the first reading process after the trigger key 18 is operated, the focal length of the varifocal camera 35 is set to a predetermined distance between the focal length of the first fixed-focus camera 33 and the focal length of the second fixed-focus camera 34, as shown in Fig. 10. That is, during the first reading process, the processing time can be shortened by adjusting the focus of the varifocal camera 35 to a predetermined position without measuring the distance. On the other hand, measuring the distance to the symbol 11 and adjusting the focal length of the varifocal camera 35 from the first reading process may result in excessive power consumption or early deterioration of the power source, such as the motor in the focal length changer 47, which adjusts the focal length.

[0085] During the initial reading, as described above, instead of setting the focal length of the varifocal camera 35 to a predetermined distance between the focal length of the first fixed-focus camera 33 and the focal length of the second fixed-focus camera 34 as shown in Fig. 10, it is also possible to set it to the distance of the focus position at which decoding was successful in the previous processing. Also, in some cases, it is possible to set it so that the processing of steps S5, S6, and S7 is always performed even during the initial reading. Alternatively, at any stage after the initial reading, the processing of steps S5, S6, and S7 can be omitted, as in the initial reading.

[0086] In the above, an example has been described in which a separate core 27 of the control device 20 is assigned to each of the cameras 33, 34, 35, and the multiple cores 27, 27, ... are used to perform parallel simultaneous processing. However, if similar parallel simultaneous processing is possible using only a single core 27, it is also possible to perform processing using that single core.

[0087] It is most preferable that the control device 20 processes the images acquired by each of the cameras 33, 34, and 35 independently of each other. By enabling each of the cameras 33, 34, and 35 to be processed independently of each other, not only is the simultaneous processing described above possible, but it is also possible to perform processing with staggered timing as shown in Fig. 22, if necessary. [Explanation of symbols]

[0088] 10 Optical information reader 11 Symbols 18 Trigger Key 20 Control device 25 Image data 27 cores 28 Image Capture Interface 29 Image Capture Interface 30 Image Capture Interface 33 First fixed focus camera 34 Second fixed focus camera 35 Varifocal Camera 36 Lighting Devices 37 Lighting Devices 38 Aiming Light Illumination Device 45 Variable focus optical system 47 Focal length change device 56 First readable area 57 Second readable area 58 Third readable area 59 First Limit Line 60 Second Limit Line 61 Third Limit Line 76 readable area 77 Readable area

Claims

1. An optical information reading device that captures an image of a symbol to be read and reads information about the symbol, The imaging device includes: a first fixed focus camera including a first fixed focus optical system having a first focal length and configured to receive light incident on a symbol and reflected by the symbol; and a first image sensor configured to convert the light received by the first fixed focus optical system into an electrical signal to generate a first image; a second fixed focus camera including: a second fixed focus optical system having a second focal length longer than the first focal length, which receives light incident on a symbol and reflected by the symbol; and a second image pickup element which converts the light received by the second fixed focus optical system into an electrical signal and generates a second image focused at a longer distance than the first image; a variable focus camera including a variable focus optical system having a variable focal length and configured to receive light incident on a symbol and reflected by the symbol, a third image pickup element configured to convert the light received by the variable focus optical system into an electrical signal to generate a third image, and a focal length change device configured to change the focal length of the variable focus optical system; and the optical information reader further includes a control device capable of reading symbol information based on the first image, the second image, and the third image; The control device controlling the focal length variation device so that the focal length of the variable-focus optical system is longer than the first focal length and shorter than the second focal length; and reading information about the symbol based on the third image, which is generated by the variable-focus camera under the controlled focal length and is focused at a longer distance than the first image and a closer distance than the second image; Optical information reading device.

2. The control device a first image capture interface connected to the first fixed focus camera to capture the first image; a second image capture interface connected to the second fixed focus camera to capture the second image; a third image capture interface connected to the variable focus camera for capturing the third image; one or more cores capable of performing decoding processes on the first image, the second image, and the third image in parallel; Equipped with 2. The optical information reader according to claim 1, wherein the timings for acquiring the first image, the second image, and the third image are independent of each other.

3. the optical information reading device further comprises a trigger key operated by an operator to define the timing of imaging by the imaging device; The control device 3. The optical information reading device according to claim 2, wherein when it detects that the trigger key has been operated, an imaging trigger is transmitted to each camera to expose the first fixed focus camera, the second fixed focus camera, and the variable focus camera in parallel.

4. The optical information reader further includes an illumination device that irradiates the symbol with illumination light, the first imaging element and the second imaging element are global shutter type image sensors, the third imaging element is a rolling shutter type image sensor, The control device 4. The optical information reading device according to claim 3, wherein the illumination light is emitted by the illumination device, and exposure is started in the first fixed focus camera and the second fixed focus camera, and then exposure in the variable focus camera is started after a predetermined period of time has elapsed.

5. The control device controlling the focal length variation device so that the focal length of the variable-focus optical system is shorter than the first focal length; and 2. The optical information reading device according to claim 1, wherein the information in the symbol is read based on the third image, which is focused at a closer distance than the first image and is generated by the variable-focus camera whose focal length is made shorter than the first focal length by the control.

6. The control device controlling the focal length variation device so that the focal length of the variable-focus optical system is longer than the second focal length; and 2. The optical information reading device according to claim 1, wherein the information in the symbol is read based on the third image, which is focused at a longer distance than the second image and is generated by the variable-focus camera whose focal length is made longer than the second focal length by the control.

7. the control device further includes a focus determination unit for determining a focal length of the variable-focus camera; The control device driving the focal length changing device so that the focal length of the variable-focus camera becomes the focal length determined by the focus determination unit; and transmitting an imaging trigger to each of the first fixed-focus camera, the second fixed-focus camera, and the variable-focus camera adjusted to the focal length determined by the focus determination unit in parallel to expose the cameras; 2. The optical information reader according to claim 1.

8. The optical information reader is a trigger key operated by an operator to define the timing of image capture by the image capture device; a storage device that stores information about a predetermined focal length for realizing a predetermined focal length between the first focal length and the second focal length in the variable-focus camera; Furthermore, The control device At the first imaging timing after detecting that the trigger key is operated, the variable-focus camera is adjusted to the predetermined focal length; and performing imaging with the variable-focus camera adjusted to the predetermined focal length; 2. The optical information reader according to claim 1.

9. The optical information reader is an illumination device that irradiates the symbol with illumination light; an aiming light emitting device that emits aiming light onto the symbol; Furthermore, 2. The optical information reader according to claim 1, wherein the first fixed focus camera, the second fixed focus camera, the variable focus camera, the illumination device, and the aiming light irradiation device are arranged in a straight line.

10. The optical information reader is an illumination device that irradiates the symbol with illumination light; an aiming light emitting device that emits aiming light onto the symbol; Furthermore, 2. The optical information reader according to claim 1, wherein the first fixed focus camera, the second fixed focus camera, the variable focus camera and the illumination device are arranged around the aiming light irradiation device.

Images