JP2004094876A - Optical information reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To successfully read a code image even when a surface to be imaged which is provided with the code image is inclined to a proper imaging surface. <P>SOLUTION: A CCD line sensor 6 converts an image of a bar code label, which is formed on the CCD line sensor 6, to an electric signal according to light and darkness of the image and stores the electric signal as imaging data. The picked-up image data are given to a CPU 18 of a control circuit 14 through an amplification circuit 15 and a binarizing circuit 16. The CPU 18 constitutes a first distance measuring instrument 21 together with a pointer light source 12a and constitutes a second distance measuring instrument together with a pointer light source 12b. An angle detector 23 for detecting an angle of a label surface P to the proper imaging surface is constituted of these distance measuring instruments 22. The CPU 18 functions as not only a correction means for correcting the imaging data on the basis of the detected angle and a decoding means for performing decoding on the basis of the corrected imaging data. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical information reading device that reads one-dimensional codes and two-dimensional codes.
[0002]
[Prior art]
FIG. 9 schematically shows a conventional optical information reading apparatus, for example, a bar code handy terminal (hereinafter referred to as BHT), which includes a CCD line sensor 101 and a lens 102 as image pickup means and is not shown. A binarization circuit for binarizing image data captured by the CCD line sensor 101, a decoding unit for decoding the binarized data, and the like are provided. In this BHT, the proper imaging surface of the label is in a plane state perpendicular to the optical axis 103 of the CCD sensor 101 and the lens 102 (see a phantom line T indicated by a dashed line). Then, imaging data with the least error is obtained.
[0003]
[Problems to be solved by the invention]
However, the label may be inclined as shown by a solid line J in FIG. In this case, in the BHT, the barcode is decoded in units of characters of a predetermined number of modules, and reading is possible even if the label is slightly inclined with respect to the appropriate imaging surface T. However, there is a limit to this, and if the inclination is further increased, the degree of unevenness of the module interval becomes large, and there is a problem that reading cannot be performed.
[0004]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical system capable of reading a code image satisfactorily even when the imaging surface provided with the code image is inclined with respect to a proper imaging surface. The present invention relates to a dynamic reading device.
[0005]
[Means for Solving the Problems]
According to the first aspect of the present invention, the angle detection unit detects the angle between the image-captured surface on which the code image is provided and the appropriate image-capturing surface, and the correction unit corrects the image data based on the detected angle. . Then, the decoding means performs decoding based on the corrected image data. Therefore, even if the imaging surface is inclined with respect to the proper imaging surface, the code image can be read well.
[0006]
In this case, the code image pickup timing by the image pickup means and the angle detection timing by the angle detection means may not overlap in time (the invention of claim 2). In this case, the code image pickup and the angle detection control When the control is performed by a single microcomputer or the like, the control becomes relatively easy.
[0007]
The code image may be a one-dimensional code or a two-dimensional code. When the code image is a one-dimensional code, the angle detection means may be one or more (the invention of claim 3). May be two or more (the invention of claim 4).
[0008]
Further, the angle detecting means includes distance measuring means for measuring a distance between each of a plurality of positions on the imaging surface provided with the code image and the reading port, and a plurality of distances measured by the distance measuring means. The angle between the imaging surface and the proper imaging surface may be detected based on the difference (the invention of claim 5). This increases the angle detection accuracy.
[0009]
The distance measuring means may include a pointer light source and measure the distance based on the position of the pointer light on the imaging surface (the invention of claim 6). By doing so, the distance measurement accuracy is high, and thus the angle detection accuracy is high.
[0010]
In this case, the distance can be accurately measured by turning on the pointer light source during a period other than the code image imaging period by the imaging unit (the invention of claim 7). In other words, when capturing a code image, illumination light is applied to the code image. However, when the pointer light source is turned on to perform distance measurement at the time of this imaging, the illumination light blurs the position of the pointer light of the pointer light source. There is a risk that it will. However, according to the above configuration, the distance can be accurately measured without the pointer light becoming unclear.
[0011]
The distance measuring means may measure the distance from the position of the pointer light imaged immediately before the imaging of the code image by the imaging means (the invention of claim 7). As a result, it is possible to correct and decode the imaging data using the latest angle detection result.
[0012]
When the code image is a one-dimensional code, two or more pointer light sources may be provided (the invention of claim 8), and when the code image is a two-dimensional code, three or more pointer light sources may be provided (claim). 9 invention). Further, it is preferable that the appropriate imaging surface is a plane orthogonal to the optical axis of the imaging means (the tenth aspect of the present invention).
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a first embodiment in which the present invention is applied to a BHT will be described with reference to FIGS. The BHT 1 shown in FIG. 2 mainly includes a hand-held case 2, and the case 2 is provided with a number of switches 3, a liquid crystal display 4, and the like. A printed wiring board 5 is provided in the case 2. The key switch 3 group and the liquid crystal display 4 are mounted on one surface of the printed wiring board 5, and the other surface is used as an image pickup means. A CCD line sensor 6 composed of a CCD image sensor and an imaging lens 7 are mounted.
[0014]
The front opening of the case 2 is a reading opening 8, and a printed wiring board 9 disposed in the case 2 so as to be located near the reading opening 8 has a hole 9 a formed in the center thereof. , An illumination LED 10 serving as illumination means and an illumination lens 11 are provided to face the illumination LED 10. Further, the printed wiring board 9 is provided with a pair of left and right pointer light sources 12a and 12b for distance measurement. A reflection mirror 13 is provided between the reading port 8 and the imaging lens 7.
[0015]
FIG. 1 shows the electrical block configuration of the BHT 1 together with an optical schematic configuration. The key switch 3 group, the liquid crystal display 4, the CCD line sensor 6, the illumination LED 10, and the pointer light sources 12a and 12b are shown. In addition, a control circuit 14, an amplification circuit 15, a binarization circuit 16, a communication I / F circuit 17 as a transfer unit, and the like are provided. The control circuit 14 is configured as a computer system including a CPU 18, a ROM 19, a RAM 20, and the like. The control circuit 14 operates according to an input signal from the key switch group 3 and a program stored in the ROM 19 in advance, and the liquid crystal display 4, the CCD line sensor 6, the amplifying circuit 15, the binarizing circuit 16, the communication I / O It controls the F circuit 17 and the like.
[0016]
The CCD line sensor 6 is configured by linearly arranging CCDs as light receiving elements. The illumination light of the illumination LED 10 is reflected by the bar code label, enters the reading port 8, is further bent by the reflection mirror 13, and is imaged on the CCD line sensor 6 by the imaging lens 7. Then, the CCD line sensor 6 converts the formed image of the barcode label into an electric signal corresponding to the brightness and stores the converted image as optical data. The image data of the CCD line sensor 6 is output to the amplifier circuit 15 as a scanning line signal, and the amplifier circuit 15 amplifies the scanning line signal from the CCD line sensor 6 and supplies it to a binarization circuit 16 as a conversion unit.
[0017]
The binarizing circuit 16 converts the analog scanning line signal into a digital signal of a light and dark pattern, and the digital signal is corrected based on the angle detection result and stored in the RAM 20 as storage means, as described later. Is done. The CPU 18 as a decoding means decodes the corrected digital signal (bar code) stored in the RAM 20 based on the decoding algorithm stored in the ROM 19, stores the decoded data in the RAM 20, and displays the decoded data on the liquid crystal display 4 and the like. To display (notify) the completion of reading, and then transfer the decoded data from the communication I / F circuit 17 to the host device.
[0018]
The CPU 18 and the pointer light source 12a constitute a first distance measuring device 21 as a distance measuring device, and the pointer light source 12b constitutes a second distance measuring device 22 as a distance measuring device.
[0019]
A distance measuring method using the distance measuring devices 21 and 22 will be described with the distance measuring device 21 as a representative. In FIG.
The distance from the reading port 8 to the barcode label surface P is L1 (mm),
The distance from the reading port 8 to the imaging lens 7 is L2 (mm),
The distance from the imaging lens 7 to the CCD line sensor 6 is L3 (mm),
The distance from the center of the optical axis to the pointer light source 12a is a1 (mm),
Let A1 (mm) be the distance that the pointer light source 12a illuminates the label surface P from the center of the optical axis,
The imaging distance of the pointer light source at the CCD line sensor 6 from the center of the optical axis is b (mm),
When the angle between the pointer light source 12a and the optical axis is θ (rad),
L1 is L1 = {(L3 · tan θ−b) · L2 + a1 · L3} / (b−L3 · tan θ) (1)
Here, L2, L3, a1, and θ are known values. B is a value that can be determined by the CPU 18. That is, b is represented by “pixel pitch” × “the number of pixels from the center of the optical axis to the image formation of the pointer light source 12a by the CCD line sensor 6”, and the pixel pitch is a known value. The number of pixels can be measured by the CPU 18 based on the electric signal from the CCD line sensor 6, and b can be determined by the CPU 18. Thus, the CPU 18 can obtain L1.
[0020]
Similarly, L1 ′ shown in FIG. 4 can be measured by the distance measuring device 22. The distance measuring devices 21 and 22 and the CPU 18 constitute an angle detecting device 23 as angle detecting means. A method of detecting the angle β between the barcode label surface P and the appropriate imaging surface (indicated by line T) by the angle detection device 23 will be described. The angle β is β = tan ⁻¹ {(L1-L1 ′) / A}.
A is a numerical value obtained by summing A1 in the distance measuring device 21 and A1 'in the distance measuring device 22.
[0021]
Further, the CPU 18 also functions as a correction unit. That is, the measured value X2 of the black pattern portion K of the bar code in the inclined state shown in FIG. 5 is corrected based on the detected angle β to obtain the true length Lb (the number of modules).
[0022]
Lb = X2 · (L1 + L1 ′) / {(L1 + L1 ′) · cosβ-2 (X1 + X2) · sinβ} (2)
Here, X1 and X2 are measured by the CCD line sensor 6, and since the angle β is known, the length Lb can be obtained. In other words, the true light and dark pattern size (Lb and La) can be obtained by correcting the light and dark pattern size (X1 and X2) of the barcode that is the imaging data.
[0023]
Here, the CPU 18 performs the above-described control in the time sequence shown in FIG. That is, when there is a switch input signal for reading a bar code from the key switch group 3, the CPU 18 first detects an angle β between the bar code label surface P and the appropriate imaging surface T as shown in step S1. . This angle detection is performed by turning on the pointer light sources 12a and 12b as described above, and does not turn on the illumination LED 10.
[0024]
Thereafter, as shown in step S2, the barcode is imaged to obtain imaged data. At this time, the pointer light sources 12a and 12b are turned off. Next, as shown in step S3, the imaging data is corrected based on the angle detection result. Then, the process shifts to step S4 to decode the corrected imaging data as described above, and then transfers the decoded data to the host device as shown in step S5. 4 displays the completion of reading.
[0025]
As described above, according to the present embodiment, the angle detector 23 detects the angle β between the barcode label surface P and the appropriate imaging surface T, and the CPU 18 corrects the imaging data based on the detected angle. . Then, the CPU 18 performs decoding based on the corrected imaging data. Therefore, even if the barcode label surface P is inclined with respect to the proper imaging surface T, the code image can be read well.
[0026]
Further, according to the present embodiment, the timing of capturing the code image by the CCD line sensor 6 and the timing of detecting the angle by the angle detection device 23 do not overlap with each other in time. The control is relatively easy when performed by a control means (CPU 18) such as one microcomputer.
[0027]
Furthermore, according to the present embodiment, the angle detecting device 23 is provided with a distance measuring device 21 that measures the distance between each of the plurality of positions on the barcode label surface P and the reading opening 8 that is a predetermined reference position. Since the angle β between the barcode label surface P and the appropriate imaging surface T is detected based on the difference between the plurality of distances L1 and L1 ′ measured by the distance measurement devices 21 and 22, The angle detection accuracy increases.
[0028]
In this case, since the distance measuring devices 21 and 22 are provided with the pointer light sources 12a and 12b and configured to measure the distance based on the position of the pointer light on the barcode label surface P, the distance measuring accuracy is high. As a result, the angle detection accuracy is increased.
[0029]
Furthermore, according to the present embodiment, since the pointer light sources 12a and 12b are turned on during periods other than the code image capturing period, the distance can be measured accurately.
[0030]
Then, since the distance measuring devices 21 and 22 measure the distance from the position of the pointer light imaged immediately before the code image is imaged, correction of the imaged data and correction of the imaged data using the latest distance measurement value and thus the latest angle detection result are performed. Decoding can be performed.
[0031]
In the above embodiment, a one-dimensional code is illustrated, and one angle detecting device is provided as the angle detecting device. However, two angle detecting devices may be provided. That is, as shown in FIG. 7 shown as a second embodiment of the present invention, a pointer light source 31a constituting a part of the first distance measuring device 31 and a pointer light source constituting a part of the second distance measuring device 32 The light source 32a and the pointer light source 33a constituting a part of the third distance measuring device 33 are arranged, for example, equally, and the first distance measuring device 31 and the second distance measuring device 32 serve as an angle detecting means. One angle detecting device 34 is constituted, and the second distance measuring device 32 and the third distance measuring device 33 constitute a second angle detecting device 35 as angle detecting means.
[0032]
According to this, for example, the angle β1 between the tangent portion at the center C1 of the left half surface of the arc-shaped barcode label surface attached to a circular article such as a can and the appropriate imaging surface, and the center of the right half surface The angle β2 between the tangent portion at C2 and the appropriate imaging surface can be detected, so that the imaging data of the code image of the arc-shaped barcode label can be corrected by the left and right halves, and the arc-shaped barcode label can be accurately read. .
[0033]
FIG. 8 shows a third embodiment of the present invention. In this embodiment, an optical information reading apparatus for reading a two-dimensional code as a code image is schematically shown. In this case, a CCD area sensor 41 composed of a CCD image sensor is provided as an imaging means, and three pointer light sources 42a, 43a, and 44a are provided. The first pointer light source 42a forms a part of the first distance measuring device 42, the second pointer light source 43a forms a part of the second distance measuring device 43, and the third pointer light source 44a 3 constitutes a part of the distance measuring device 44. The first distance measuring device 42 and the second distance measuring device 43 constitute a first angle detecting device 45 as an angle detecting means, and the second distance measuring device 43 and the third distance measuring device 44 Constitute the second angle detecting device 46 as another angle detecting means. Thereby, a two-dimensional angle of the two-dimensional code can be detected. Note that three or more angle detection means may be used.
[0034]
The distance measuring means may be an ultrasonic distance measuring device. As an imaging means, a CMOS image sensor may be used instead of the CCD image sensor. Further, the optical information reading device of the present invention is not limited to the BHT, but can be applied to a stationary type.
[Brief description of the drawings]
FIG. 1 is a block diagram of a BHT. FIG. 2 is a longitudinal side view of the BHT. FIG. 3 is a principle diagram for explaining a distance measuring method by a distance measuring device. FIG. 4 is a principle diagram for explaining an angle detecting method. FIG. 5 is a principle diagram for explaining correction of imaging data. FIG. 6 is a flowchart of bar code reading control. FIG. 7 is a diagram corresponding to FIG. 4 showing a second embodiment of the present invention. FIG. 9 is a schematic perspective view showing a third embodiment. FIG. 9 is a schematic configuration diagram showing a conventional example.
6 is a CCD line sensor (imaging means), 8 is a reading port, 12a and 12b are pointer light sources, 14 is a control circuit, 18 is a CPU (correction means and decoding means), 21 is a first distance measuring device (distance measuring means) ), 22 is a second distance measuring device (distance measuring device), 23 is an angle detecting device (angle detecting device), 31a, 32a, 33a are pointer light sources, 31 is a first distance measuring device (distance measuring device), 32 is a second distance measuring device (distance measuring device), 33 is a third distance measuring device (distance measuring device), 34 is a first angle detecting device (angle detecting device), and 35 is a second angle detecting device. (Angle detecting means), 41 is a CCD area sensor (imaging means), 42a, 43a, 44a are pointer light sources, 42 is a first distance measuring device (distance measuring means), 43 is a second distance measuring device (distance measuring device) Means), 44 Third distance measuring device (distance measuring means) 45 first angle detection device (angle detector), 46 denotes second angle detecting device (angle detection means).

Claims (10)

Imaging means for imaging a code image and outputting imaging data;
Angle detection means for detecting the angle between the image-captured surface provided with the code image and the appropriate image-capturing surface,
Correction means for correcting the imaging data based on the detected angle,
An optical information reading apparatus comprising: decoding means for decoding based on the corrected image data. 2. The optical information reading apparatus according to claim 1, wherein the code image pickup timing by the image pickup means and the angle detection timing by the angle detection means do not overlap in time. 3. The optical information reading apparatus according to claim 1, wherein the code image is a one-dimensional code, and at least one angle detecting unit is provided. 3. The optical information reading apparatus according to claim 1, wherein the code image is a two-dimensional code, and two or more angle detecting means are provided. The angle detecting means includes distance measuring means for measuring a distance between each of a plurality of positions on the imaging surface provided with the code image and a predetermined reference position, and a plurality of distances measured by the distance measuring means. 2. The optical information reading device according to claim 1, wherein an angle between the imaging surface and the proper imaging surface is detected based on a difference in distance. 6. The optical information reading apparatus according to claim 5, wherein the distance measuring means includes a pointer light source, and measures the distance based on a position of the pointer light on the imaging surface. 7. The pointer light source is turned on during a period other than the code image capturing period by the image capturing unit, and the distance measuring unit measures the distance from the position of the pointer light captured immediately before the code image capturing by the image capturing unit. The optical information reading device according to claim 1. 7. The optical information reading device according to claim 6, wherein the code image is a one-dimensional code, and two or more pointer light sources are provided. 7. The optical information reading apparatus according to claim 6, wherein the code image is a two-dimensional code, and three or more pointer light sources are provided. 10. The optical information reading apparatus according to claim 1, wherein the appropriate imaging surface is a plane orthogonal to an optical axis of the imaging unit.

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