Device and method for reading optical information

Abstract

To provide an optical information reading device which suppresses flickering of light for reading an optical code.SOLUTION: An optical information reading device is provided, comprising a light source, an image sensor configured to repeat first exposure and second exposure, and a control unit configured to control the light source such that the light intensity centers of exposure illumination during the first exposure and the light intensity centers of dummy illumination before and after, or before, the second exposure lie at equal time intervals.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to an optical information reading device and an optical information reading method. [Background technology]

[0002] 2. Description of the Related Art Optical information readers, such as code scanners, are used to read optical codes, such as one-dimensional codes and two-dimensional codes. Optical information readers are widely used in various fields, such as product management and position detection.

[0003] As optical codes, for example, one-dimensional codes, two-dimensional codes, etc., which express information using symbols with a light reflectance different from the surroundings, are used. One-dimensional codes are also called barcodes, linear codes, etc. One-dimensional codes are made by arranging lines of various widths adjacent to each other in a straight line, and expressing information such as alphanumeric characters using the line parts and blank parts. One-dimensional codes express, for example, universal product codes. Two-dimensional codes are also called two-dimensional symbols, etc., and express information using symbols arranged vertically and horizontally. Two-dimensional codes have a high information density and can store more information than one-dimensional codes. QR Code (registered trademark) is a type of two-dimensional code. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-55396 A [Patent Document 2] U.S. Pat. No. 9,659,199 [Patent Document 3] U.S. Patent No. 7,234,641 [Patent Document 4] U.S. Patent No. 8,902,353 Summary of the Invention [Problem to be solved by the invention]

[0005] Some optical information readers illuminate the optical code with a blinking light in order to read the optical code. If the interval between the blinking lights is long, it may appear flickering to the human eye, which may cause discomfort.

[0006] The present disclosure has been made in consideration of the above-mentioned points, and contributes to providing an optical information reading device and an optical information reading method that can suppress flickering of light for reading optical codes. [Means for solving the problem]

[0007] The optical information reading device of the present disclosure includes a light source, an imaging element that repeats a first exposure and a second exposure, and a control unit that controls the light source so that the center of light quantity of the exposure illumination during the first exposure and the center of light quantity of the dummy illumination before, after, or before the second exposure are equidistant in time.

[0008] The optical information reading method disclosed herein repeats a first exposure and a second exposure, and controls a light source so that the center of light quantity gravity of the exposure illumination during the first exposure and the center of light quantity gravity of the dummy illumination before, after, or before the second exposure are equidistant in time. Effect of the Invention

[0009] According to the present disclosure, flickering of light for reading optical codes can be suppressed. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing an example of a schematic hardware configuration of a code scanner according to an embodiment of the present disclosure. [Diagram 2] FIG. 1 is a diagram illustrating an example of detection of specular reflection. [Diagram 3] FIG. 1 is a diagram for explaining an example of the timing of lighting and photography; [Figure 4] FIG. 1 is a diagram for explaining another example of the timing of lighting and photography; [Diagram 5] A diagram explaining code scanner operation example 1 [Figure 6] A diagram explaining code scanner operation example 2 [Figure 7] A diagram explaining code scanner operation example 3 [Figure 8] Diagram explaining verification of lighting flicker DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. In the present disclosure, a case where a code scanner is used as an example of an optical information reading device will be described. The code scanner of the present disclosure may be used, for example, in a store or the like to read product information of a product purchased by a customer. In addition, the code scanner of the present disclosure may be attached to a vehicle that travels on a track installed on the ceiling of a factory or the like to transport parts or the like, and used to read an optical code affixed to a predetermined position.

[0012] <Code scanner configuration example> 1 is a diagram showing an example of a schematic hardware configuration of a code scanner 100 according to an embodiment of the present disclosure. The code scanner 100 is composed of an optical head unit 110 and a decoder unit 120. The optical head unit 110 and the decoder unit 120 may be separate or integrated.

[0013] The optical head unit 110 includes a lens 111 and a CMOS (Complementary Metal Oxide Semiconductor) image sensor (hereinafter simply referred to as "CMOS") 112, which is an example of a solid-state imaging element. The optical head unit 110 also includes a light-emitting diode (LED) 113, which is an example of a light source.

[0014] The lens 111 is, for example, an optical lens, which takes in an image of an object to be read, including an optical code, into the optical head unit 110 and forms an image on the imaging area of ​​the CMOS 112 .

[0015] The CMOS 112 captures an image of the object to be read using reflected light from the object captured by the lens 111, generates image data expressed in digital brightness values ​​from the analog image signal obtained by the image capture, and outputs the image data to the decoder unit 120.

[0016] The LED 113 emits light to illuminate the object to be read, thereby enabling the CMOS 112 to capture a clear image.

[0017] The decoder unit 120 includes a first input / output interface (first I / O) 121, a processor 122, a RAM (Random Access Memory) 123, a ROM (Read Only Memory) 124, and a second input / output interface (second I / O) 125.

[0018] The first I / O 121 is an interface for data communication between the optical head unit 110 and the decoder unit 120. The image data output from the CMOS 112 is input to the processor 122 via the first I / O 121.

[0019] The processor 122 is, for example, a central processing unit (CPU). The processor 122 may be referred to as a control unit.

[0020] The processor 122 controls the CMOS 112 and the LED 113, performs filtering to remove noise from the image data input from the CMOS 112 via the first I / O 121, processes data in preparation for decoding, and decodes the optical code included in the processed image data. Details of the decoding process may be any known method, such as the method described in Japanese Patent Application Laid-Open No. 2005-25417.

[0021] The RAM 123 is a storage means for temporarily storing image data input from the CMOS 112, for use as a work memory during data processing in preparation for decoding, and for storing dynamically changed data such as data necessary for the operation of the code scanner 100. Note that a part of the RAM 123 may be made non-volatile.

[0022] The ROM 124 is a non-volatile storage means for storing a program for starting the code scanner 100 and the like.

[0023] The second I / O 125 is an interface for data communication between the processor 122 and other devices such as a server or a vehicle. The decoded data information output from the processor 122 is input to other devices such as a server or a vehicle via the second I / O 125.

[0024] <Analysis> When a code scanner (CMOS) reads an optical code, the light (illumination) output from the LED is irradiated onto the optical code. If the light irradiated onto the optical code is specularly reflected by the optical code, the code scanner may not be able to read the optical code properly.

[0025] Therefore, the code scanner compares an image of the optical code captured with the lighting (LED) turned on with an image of the optical code captured with the lighting turned off, and detects whether or not light is reflected specularly by the optical code.

[0026] Fig. 2 is a diagram for explaining an example of detection of regular reflection. Fig. 2(A) shows an image of optical code A2a captured by the code scanner when the illumination is turned on. Fig. 2(B) shows an image of optical code A2b captured by the code scanner when the illumination is turned off.

[0027] When specular reflection of light occurs in the optical code, part of the image of the optical code A2a becomes invisible due to specular reflection, as shown in (A) of Fig. 2. Therefore, the code scanner detects specular reflection of light in the optical code A2a by comparing the image of the optical code A2a when the illumination is turned on with the image of the optical code A2a when the illumination is turned off.

[0028] The interval between photographing the optical code A2a must be close in time. For example, if the interval between photographing the optical code A2a is long, even if the optical code A2a is captured when the light is turned on, the optical head or the optical code A2a may move when the light is turned off, and the optical code A2a may not be captured. In this case, the code scanner cannot detect the regular reflection of light from the optical code A2a. Therefore, it is possible to alternate between photographing with the light on and photographing with the light off.

[0029] Fig. 3 is a diagram for explaining an example of the timing of illumination and exposure. Fig. 3(A) shows a timing chart for repeating exposure with illumination on. Fig. 3(B) shows a timing chart for alternately repeating exposure with illumination on and exposure with illumination off to detect specular reflection.

[0030] In addition, in (A) of Fig. 3, it is not possible to detect the presence or absence of regular reflection of light in the optical code. (A) of Fig. 3 is illustrated for comparison with the timing chart in (B) of Fig. 3.

[0031] The horizontal axis "t" in FIG. 3 indicates time. The vertical axis "A" in FIG. 3 indicates the amount of light. "Exposure" in FIG. 3 indicates the exposure time of the CMOS. "Image data transfer" in FIG. 3 indicates the time it takes for image data captured by the CMOS to be transferred to the processor. "Data processing" in FIG. 3 indicates the image data processing time of the processor (e.g., the time it takes to decode an optical code). "Lighting on" in FIG. 3 indicates the time (period) that the lighting is on.

[0032] The frequency of "lights on" shown in Fig. 3(A) is, for example, 60 Hz. In this case, the blinking of the lights is difficult for the human eye to detect, and is unlikely to cause discomfort.

[0033] On the other hand, if an exposure with "lighting off" is inserted between an exposure with "lighting on" and the next exposure with "lighting on" in order to detect specular reflection of light, as shown in (B) of Fig. 3, the interval (frequency) at which the lighting is turned on becomes, for example, 60 Hz or less. In this case, the blinking of the lighting becomes easily noticeable to the human eye, which may cause discomfort.

[0034] Fig. 4 is a diagram explaining another example of the timing of illumination and exposure. In the timing chart shown in Fig. 4, in contrast to the timing chart of Fig. 3(B), in order to suppress the blinking of illumination seen by the human eye, dummy illumination is turned on after exposure with "illumination off" (see "dummy illumination on" in Fig. 4). As a result, in Fig. 4, the interval at which illumination is turned on is shorter than the interval of "illumination on" in Fig. 3(B), and the blinking of illumination seen by the human eye is suppressed.

[0035] However, in the timing chart of Figure 4, the intervals at which the lights are turned on (the intervals between "lights on" and "dummy lights on") are not equal, so the lights may appear to flicker to the human eye, which may cause discomfort.

[0036] Therefore, in this disclosure, in order to reduce flicker that is unpleasant to the human eye, the center of light quantity of the illumination that is turned on during exposure and the center of light quantity of the dummy illumination are controlled to be equal to each other at nominal tolerance.

[0037] <Example 1> 5 is a diagram for explaining an operation example 1 of the code scanner 100. In order to detect specular reflection of light, the code scanner 100 performs exposure of the CMOS 112 using illumination (light) from the LED 113 and exposure of the CMOS 112 without using illumination from the LED 113.

[0038] For example, the code scanner 100 performs exposure of the CMOS 112 using illumination from the LED 113 as shown by arrows A5a and A5c in FIG. 5, and exposure of the CMOS 112 without illumination from the LED 113 as shown by arrows A5b and A5d in FIG.

[0039] Exposure using illumination can be considered as exposure in which the LED 113 is turned on when exposing the CMOS 112. Exposure without illumination can be considered as exposure in which the LED 113 is not turned on when exposing the CMOS 112.

[0040] Hereinafter, exposure using illumination may be referred to as illumination exposure. Exposure without illumination may be referred to as non-illumination exposure. Furthermore, illumination turned on during exposure may be referred to as exposure illumination. Illumination turned on when not exposure may be referred to as dummy illumination.

[0041] Illuminated exposure and non-illuminated exposure are alternately and repeatedly performed at intervals as shown by arrows A5a to A5d in Fig. 5. The code scanner 100 turns on dummy illumination (see "dummy illumination on" in Fig. 5) between illuminated exposure and non-illuminated exposure, before and after non-illuminated exposure (see arrows A5b and A5d in Fig. 5).

[0042] The dotted lines A5e and A5g in Fig. 5 indicate the center of gravity of the light amount of the exposure illumination. For example, as shown in "illumination on" in Fig. 5, when the exposure illumination emits light in a pulsed (rectangular) manner, the center of gravity of the light amount of the exposure illumination is the timing (time) at which the area of ​​the rectangle is halved.

[0043] The dotted lines A5f and A5h in Fig. 5 indicate the center of gravity of the light amount of the dummy lighting. For example, as shown in "dummy lighting on" in Fig. 5, when two dummy lighting before and after non-illumination exposure emit light in pulses with the same light amount, the center of gravity of the light amount of the dummy lighting is the middle timing of the two dummy lighting before and after non-illumination exposure.

[0044] The processor 122 controls the on-time and light amount of the LED 113 so that the center of light amount of the exposure illumination and the center of light amount of the dummy illumination alternately have equal intervals in time (on the time axis). For example, the processor 122 controls the on-time and light amount of the exposure illumination and the dummy illumination so that the intervals of the dotted lines A5e to A5h in FIG. 5 are equal.

[0045] The on-time and light amount of the LED 113 may be controlled so that the center of light amount of the exposure lighting and the center of light amount of the dummy lighting are alternately spaced at equal intervals. Therefore, the intervals between the exposure lighting and the dummy lighting do not have to be equal. For example, the intervals between the rectangles shown for "lighting on" and "dummy lighting on" in FIG. 5 do not have to be equal.

[0046] In this way, the processor 122 controls the on-time and light amount of the LED 113 so that the light amount center of the exposure lighting and the light amount center of the dummy lighting alternate at equal intervals. This reduces flickering of the lighting seen by the human eye and reduces discomfort, even if the exposure lighting and the dummy lighting are not at equal intervals.

[0047] The processor 122 may control the LEDs 113 so that the total amount of light of the exposure illumination is equal to the total amount of light of the dummy illumination.

[0048] 5, the time of exposure illumination may be the same as the exposure time of the CMOS 112. The time of exposure illumination may be shorter than the exposure time of the CMOS 112 (see, for example, "Exposure Illumination" in FIG. 8C). The time of exposure illumination may be longer than the exposure time of the CMOS 112.

[0049] Also, two or more dummy lights may be provided before the non-illumination exposure and two or more after the non-illumination exposure. In this case, flickering of the lights is further suppressed. Note that, as shown in FIG. 5, when one dummy light is provided before the non-illumination exposure and one after the non-illumination exposure, power consumption is suppressed more than when two or more dummy lights are provided before the non-illumination exposure and two or more dummy lights are provided after the non-illumination exposure.

[0050] <Example 2> In the first operational example, a pulsed illumination is output, but this is not limiting. The illumination waveform may have any shape.

[0051] 6 is a diagram for explaining the second operation example of the code scanner 100. As explained in the first operation example, the processor 122 controls the on-time and light amount of the LED 113 so that the light amount center of the exposure lighting and the light amount center of the dummy lighting alternate at equal intervals. This reduces discomfort caused by lighting flicker.

[0052] Therefore, if the on-time and light amount of the LED 113 are controlled so that the light amount center of the exposure illumination and the light amount center of the dummy illumination alternate at equal intervals, the waveform of the light amount of the light output from the LED 113 may have any shape as shown in Fig. 6. That is, the code scanner 100 can flexibly control the profiles (light amount in a time series, i.e., the waveform of the light amount) of the exposure illumination and the dummy illumination. For example, as shown by the arrows A6a to A6f in Fig. 6, the profiles of the exposure illumination and the dummy illumination may be different from each other.

[0053] In addition, there is a blank between the data processing and the non-illumination exposure shown in Fig. 6, and during this blank period, the processor 122 may calculate the profile of the exposure illumination and the dummy illumination. If the processor 122 does not calculate the profile of the exposure illumination and the dummy illumination, there is no need to provide a blank between the non-illumination exposure. The same applies to the operation example 1 described in Fig. 5.

[0054] <Example 3> In the operation examples 1 and 2, the dummy illumination is output before and after the non-illumination exposure, but this is not limited to the above. The dummy illumination may be output before the non-illumination exposure and may not be output after the non-illumination exposure.

[0055] FIG. 7 is a diagram for explaining an operation example 3 of the code scanner 100. The processor 122 turns on the dummy illumination before the non-illumination exposure shown by the arrow A7a in FIG. 7. As described in the operation examples 1 and 2, the processor 122 controls the on-time and light amount of the LED 113 so that the light amount center of the exposure illumination and the light amount center of the dummy illumination alternate at equal intervals. For example, the processor 122 controls the on-time of the LED 113 after a predetermined delay (so that the light amount center of the exposure illumination and the light amount center of the dummy illumination alternate at equal intervals) after data processing of the optical code, as shown by the arrow A7b in FIG. 7.

[0056] In this way, the processor 122 may output the dummy illumination before the non-illumination exposure. Even in this case, the processor 122 controls the on-time and light amount of the LED 113 so that the light amount center of the exposure illumination and the light amount center of the dummy illumination alternately have equal intervals, thereby suppressing discomfort caused by flickering of the illumination. Also, the power consumption of the code scanner 100 is suppressed.

[0057] <Verification> Fig. 8 is a diagram for explaining the verification of lighting flicker. Fig. 8(A) shows a timing chart in the model of Fig. 4. That is, Fig. 8(A) shows a timing chart of a code scanner that outputs dummy lighting but is not controlled so that the light quantity center of the exposure lighting and the light quantity center of the dummy lighting are alternately spaced at equal intervals.

[0058] FIG. 8B shows a timing chart of the code scanner when dummy illumination is output after non-illumination exposure.

[0059] Fig. 8(C) shows a timing chart of the code scanner 100. That is, Fig. 8(C) shows a timing chart of the code scanner 100 that controls the output of the exposure illumination and the dummy illumination so that the centers of light quantity of the exposure illumination and the centers of light quantity of the dummy illumination alternate at equal intervals.

[0060] In the verification of FIG. 8, the illumination exposure and non-illumination exposure times were set to 8 ms. The image data transfer time for non-illumination exposure was set to 10 ms. The exposure illumination and dummy illumination times in FIG. 8(A) and FIG. 8(B) were set to 4 ms. The exposure illumination time in FIG. 8(C) was set to 4 ms, and the dummy illumination time was set to 2 ms. The intervals between the exposure illumination and dummy illumination in FIG. 8(A) were set to 22 ms and 6 ms. The interval between the exposure illumination and dummy illumination in FIG. 8(B) was set to 22 ms. The interval between the exposure illumination and dummy illumination in FIG. 8(C) was set to 11 ms, and the interval between the dummy illumination was set to 8 ms.

[0061] In the timing charts of Fig. 8(A) and Fig. 8(B), flickering of the illumination was perceived by the naked eye. In contrast, in the timing chart of Fig. 8(C), flickering of the illumination was not perceived by the naked eye. In other words, in the code scanner 100 of the present disclosure, flickering of the illumination was not perceived by the naked eye.

[0062] <Summary of the embodiment> As described above, the CMOS 112 repeats illumination exposure and non-illumination exposure, and the processor 122 controls the LED 113 so that the center of light quantity of the exposure illumination during illumination exposure and the center of light quantity of the dummy illumination before, after, or before non-illumination exposure are equidistant in time. This suppresses flickering of the illumination seen by the human eye, thereby suppressing discomfort.

[0063] The above describes the embodiment. Although the above describes the case where a code scanner is used as an optical information reading device, the present disclosure can also be applied to the case where other optical information reading devices are used. In this specification, "same" may include "approximately the same." "Center" may include "approximately the center." "Equal intervals" may include "approximately equal intervals." "Exposure" may be read as "photographing." The processor 122 may control at least one of the on-time and light amount of the LED 113 so that the light amount center of the exposure illumination and the light amount center of the dummy illumination are equidistant in time.

[0064] The hardware configuration example in Fig. 1 is an example, and is not limited to the configuration example in Fig. 1. For example, the first I / O 121 and the second I / O 125 may be included in the processor 122. For example, storage means such as the RAM 123 and the ROM 124 may be included in the processor 122. In addition, the means for realizing the functions described in the above operation examples 1 to 3 are not limited to a processor, etc., and may be realized by a dedicated circuit. For example, the functions of the optical head unit 110 and the decoder unit 120 may be realized by a device such as an FPGA (Field Programmable Gate Array). [Industrial Applicability]

[0065] The present disclosure is suitable for use in an optical information reading device and an optical information reading method for reading optical codes. [Explanation of symbols]

[0066] 100 Code Scanner 110 Optical head unit 111 Lens 112 CCD 113 LED 120 Decoder section 121 1st I / O 122 processors 123 RAM 124 ROM 125 2nd I / O

Claims

1. A light source; an image sensor that repeats a first exposure and a second exposure; a control unit that controls the light source so that a center of light quantity of the exposure illumination during the first exposure and a center of light quantity of the dummy illumination before, after, or before the second exposure are equidistant in time; An optical information reading device having the above structure.

2. the control unit controls the light sources so that a total amount of light of the exposure illumination and a total amount of light of the dummy illumination are equal to each other.

2. The optical information reader according to claim 1.

3. the control unit controls the light source so that the light quantity waveforms of the exposure illumination in the first exposure sandwiching the second exposure are different from each other.

2. The optical information reader according to claim 1.

4. the control unit controls the light source so that the light amount waveform of the dummy illumination is different before and after the second exposure.

2. The optical information reader according to claim 1.

5. The control unit controls at least one of the light amount and the on-time of the light source.

2. The optical information reader according to claim 1.

6. Repeating the first exposure and the second exposure, a light source is controlled so that a center of light quantity of the exposure illumination during the first exposure and a center of light quantity of the dummy illumination before, after, or before the second exposure are spaced equally apart in time. Optical information reading method.

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