JP5168245B2 - Optical information reader - Google Patents

Description

  The present invention relates to an optical information reader.

  In an optical information reader such as a barcode reader, a light receiving sensor (for example, a CCD sensor, a CMOS sensor, etc.) in which a plurality of light receiving elements are arranged is generally used, and an information code such as a barcode is used by the light receiving sensor. In addition to receiving reflected light from the light, a light reception signal (electric signal) corresponding to the image of the information code is output. The output received light signal is binarized by a binarization circuit, and the binary data is decoded by a decoding means.

JP 2005-293327 A Japanese Patent Laid-Open No. 10-320496

  In this type of optical information reader, there is a problem of how to remove noise contained in the light reception signal. For example, Patent Documents 1 and 2 disclose techniques for removing noise contained in a light reception signal. Patent Document 1 discloses a technique for removing high-frequency noise components from a light reception signal using a low-pass filter or the like. ing. Further, Patent Document 2 discloses a technique for solving a problem when a low-pass filter is used.

  On the other hand, as a noise removal method, an illumination light source that emits illumination light of a specific color is provided, and an optical filter that transmits light in a frequency band corresponding to the specific color and blocks light in other frequency bands is used in combination. It is also possible to consider a configuration that performs the above. According to this configuration, it is possible to satisfactorily remove disturbance light having a frequency that is significantly different from that of the illumination light, and to effectively suppress noise caused by the disturbance light in the received light signal.

  In addition, both the configuration using the low-pass filter and the configuration using the optical filter have specific advantages, and more effective noise removal can be expected if they are used in combination. However, there are various cases for the display mode of the information code to be read, and in some cases, noise removal may not be sufficiently performed even if the low-pass filter and the optical filter are used in combination. For example, in recent optical information readers, there is an increasing need to read information codes displayed on a color display device, and thus information codes displayed on a color display device are to be read. Even if the low-pass filter and the optical filter are used in combination, noise removal may not be performed properly due to circumstances peculiar to the color display device.

  For example, when an illumination light source that emits red illumination light is used and an optical filter that suppresses light other than a predetermined frequency band corresponding to red is used, a light / dark code (for example, a barcode) that is read on a paper medium or the like If so, it is possible to selectively transmit the red reflected light from the light color region, and to effectively remove disturbance light other than red, so the pattern of the light color region and the dark color region can be appropriately set. A reflected waveform can be obtained. However, when imaging a light and dark code (for example, a barcode) displayed on a color display device such as a liquid crystal display device, light other than the color to be transmitted through the optical filter (in this case, red) is generated from the light color region. There is a problem that light from a part of the bright color area is cut off.

  For example, as shown in FIG. 10, R pixel Ra, G pixel Ga, and B pixel Ba (sub pixel) are combined to form one display pixel Sa (pixel), and a plurality of such display pixels Sa are arranged. In the case of a liquid crystal display device, when displaying a white color on a certain display pixel Sa, in reality, the R pixel Ra, the G pixel Ga, and the B pixel Ba (sub-pixel) can be visually recognized as white by visually emitting light. It is generating light. When imaging a light / dark code displayed on such a liquid crystal display device, as shown in FIG. 11A, the red light generated from the R pixel Ra passes through the optical filter F for the R pixel Ra. It will be recognized as a bright color area. However, as shown in the middle and lower parts of FIG. 11A, for the G pixel Ga and the B pixel Ba, since the green light and blue light from these pixels are suppressed by the optical filter F, the amount of light received by the light receiving sensor. Is suppressed, and although it should be an area that should originally be recognized as a bright color area, it is erroneously recognized as a dark color area. Note that the upper part of FIG. 11A illustrates a barcode displayed on the liquid crystal display device. Further, the middle part of FIG. 11A shows a part (dark color bar B1, light color bar W1, dark color bar B2) of an image pickup position (position of a dashed line L) when such a barcode is imaged by a line sensor. The arrangement of display pixels in FIG. Further, the lower part of FIG. 11A conceptually shows a light reception signal generated by receiving light from each display pixel Sa in the middle part of FIG.

  FIG. 11B shows a signal obtained by binarizing the light reception signal in the lower part of FIG. 11A. This binarized signal is essentially a series of bright colors as shown in FIG. 11C. In an area AR (an area corresponding to the light color bar W1) to be specified as an area, a part of the area AR is a value indicating a dark color area (L level in this example). If such a misrecognition is made, the size of each bright color area of the information code cannot be properly recognized, leading to a decoding failure of the entire information code.

  The present invention has been made to solve the above-described problems, and can read both the information code displayed on the color display device and the information code attached to the object, and can be displayed on the color display device. It is an object of the present invention to provide an optical information reader capable of properly removing noise and accurately recognizing a bright color area and a dark color area even when reading an information code.

The invention according to claim 1 is an optical information reading device capable of reading an information code displayed on a color display device and an information code attached to an object as a reading target code, and illuminating light to the reading target code Illuminating means for irradiating light, an optical filter for passing light in a predetermined frequency band corresponding to the illumination light, and suppressing passage of light outside the predetermined frequency band, and reflected light from the reading target code in the optical filter A light receiving sensor that outputs a light receiving signal corresponding to the reflected light, a sensor driving circuit that outputs a driving signal having a set frequency to the light receiving sensor, and the light output from the light receiving sensor. A light-receiving signal is input and a low-pass filter circuit that suppresses signals with a frequency higher than the specified cutoff frequency is output from the low-pass filter circuit. The binarizing means for binarizing the received light signal, the decoding means for performing a decoding process based on the binarized signal generated by the binarizing means, and the setting change between the first mode and the second mode Possible mode switching means.
The sensor driving circuit sets the frequency of the driving signal to the first frequency when the mode switching unit sets the first mode, and when the mode switching unit sets the second mode, The configuration is such that the frequency of the drive signal is changed to a second frequency that is higher than the first frequency, and the light receiving sensor is configured to output the drive signal of the first frequency from the sensor drive circuit. The light reception signal corresponding to the reflected light from the code to be read is output at a speed corresponding to the first frequency, and the reflection signal is output when the drive signal of the second frequency is output. The light reception signal corresponding to light is output at a speed corresponding to the second frequency.

  According to a second aspect of the present invention, in the optical information reading device according to the first aspect, the color display device is formed by arranging a plurality of display pixels constituted by combinations of R pixels, G pixels, and B pixels. It is characterized by being.

  According to a third aspect of the present invention, in the optical information reading apparatus according to the second aspect, the illuminating unit irradiates the red illumination light, and the optical filter is emitted from the G pixel and the B pixel. It is characterized in that the passage of light is suppressed more than the passage of light emitted from the R pixel.

  According to a fourth aspect of the present invention, in the optical information reading device according to any one of the first to third aspects, the color display device is a display device provided in a portable terminal. .

  According to a fifth aspect of the present invention, in the optical information reading device according to any one of the first to fourth aspects, the mode order defining means for determining a setting order of the first mode and the second mode is further provided. Provided, and the mode switching means sets either the first mode or the second mode as the previous mode according to the order defined by the mode order defining means, and is set to the previous mode. When the decoding process performed in the state fails, the setting is changed to the other.

  A sixth aspect of the present invention is the optical information reading apparatus according to the fifth aspect, further comprising a mode in which the decoding process is performed on the result of the decoding process performed in the first mode or the second mode. Storage means that can be stored in association with each other, and the mode order defining means, based on the storage contents of the storage means, of the first mode and the second mode, the mode in which the decoding process was successful last time. It is characterized by priority setting.

The invention according to claim 1 is provided with an optical filter that transmits light in a predetermined frequency band corresponding to the illumination light and suppresses passage of light other than the predetermined frequency band, and reflects the reflected light from the reading target code as an optical filter. The light receiving sensor is configured to receive light via By doing in this way, disturbance light other than the reflected light which illumination light reflected in the reading object code | cord | chord can be removed effectively.
On the other hand, with such a configuration, when the information code displayed on the color display device is the code to be read, a part of pixels in the area displaying the bright color pattern (pixels that emit light suppressed by the optical filter) There is a concern that the light from the light is suppressed by the optical filter, and the waveform component indicating the dark color is included in the waveform of the light color pattern portion in the light reception signal as noise.
On the other hand, the present invention sets the frequency of the drive signal to the first frequency when set to the first mode, and sets the frequency of the drive signal to the first frequency when set to the second mode. The setting is changed to a second frequency larger than that. When the drive signal having the first frequency is output, the light reception signal corresponding to the reflected light from the reading target code is output at a speed corresponding to the first frequency, and the drive signal having the second frequency is output. Is output at a speed corresponding to the second frequency.
In this case, when the information code displayed on the color display device is to be read, and the waveform component indicating the dark color is included as noise in the waveform of the bright color pattern region, the light receiving sensor is operated at the second frequency. By driving, it is possible to relatively increase the frequency of the waveform of the light color pattern region (the waveform of the light / dark alternating signal including the normal signal indicating the light color and the noise indicating the dark color). As a result, when the received light signal is input to the low-pass filter circuit, the attenuation level of the signal in the bright color pattern area is increased, and noise indicating the dark color included in the signal in the bright color pattern area is effectively removed. Can do.
On the other hand, since the light receiving sensor can be driven at the first frequency as needed, it is difficult to misrecognize the bright color pattern area when reading the information code attached to the paper medium (that is, the bright color). In the case where it is difficult for the received light signal in the pattern area to contain dark-colored noise), the drive frequency can be suppressed to a setting that is advantageous for finer reading.

  According to the second aspect of the present invention, the color display device to be read has a configuration in which a plurality of display pixels constituted by combinations of R pixels, G pixels, and B pixels are arranged. According to the present invention, the information code displayed on the color display device can be read well with the RGB color display device widely used in various places as an object to be read. Can be increased.

  According to a third aspect of the present invention, the illumination means emits red illumination light, and the optical filter suppresses passage of light emitted from the G pixel and B pixel as compared with passage of light emitted from the R pixel. doing. In this case, when the information code attached to the object is read as the reading target code, the light reflected by the bright color region (red light) can be selectively transmitted by the optical filter, The disturbance light can be removed well. On the other hand, when reading the information code displayed on the color display device, the light component from the G pixel and B pixel is suppressed by the optical filter in the region where the bright color pattern is displayed, and the waveform component indicating the dark color in the waveform of the bright color pattern portion May be included as noise. However, since the frequency of the sensor drive signal can be increased as necessary, the frequency of the light reception signal can be relatively increased, and noise (G pixel and B pixel) indicating a dark color in the signal waveform of the bright color pattern region. In the case where noise due to the noise is included, it is possible to increase the degree of attenuation of the signal in the light color pattern region in the low-pass filter circuit. Therefore, even if the signal waveform in the light color pattern region includes noise indicating a dark color (noise due to the G pixel and B pixel), the noise can be effectively removed.

  In the invention of claim 4, the information code displayed on the color display device provided in the portable terminal is used as the reading object code. In this way, it is possible to satisfactorily read an information code displayed on the mobile terminal using a mobile terminal widely used in various places as a reading target, and the convenience for the user can be further enhanced.

  According to a fifth aspect of the present invention, mode order defining means for determining the setting order of the first mode and the second mode is provided. Then, the mode switching means sets one of the first mode and the second mode as the previous mode according to the order defined by the mode order defining means, and is performed in a state where the previous mode is set. When the decoding process fails, the setting is changed to the other. In this way, when the decoding process fails in one mode, it is possible to quickly and smoothly switch to the other mode and execute the decoding process again in the other mode, which imposes a special burden on the user. Therefore, it is possible to effectively increase the decoding success probability.

  In the invention of claim 6, there is provided storage means capable of storing the result of the decoding process when the decoding process is performed in the first mode or the second mode in association with the mode in which the decoding process is performed, Based on the stored contents of the storage means, the mode in which the decoding process was last successful is preferentially set out of the first mode and the second mode. The mode in which the decoding process was successful last time is more likely to succeed in the decoding mode than the other mode, and if this mode is set with priority, the success probability of the decoding process can be effectively increased. The reading process can be speeded up.

FIG. 1 is a block diagram illustrating an optical information reading apparatus according to the first embodiment of the invention. FIG. 2 is a flowchart illustrating the flow of reading processing performed by the optical information reading apparatus of FIG. FIG. 3A is an explanatory diagram illustrating a sensor drive signal output in the first mode, and FIG. 3B is an explanatory diagram illustrating a sensor drive signal output in the second mode. FIG. FIG. 4 is an explanatory diagram for explaining a case where an information code displayed on the color display device is to be read. FIG. 5 conceptually shows the waveform of the bright color region converted by the low-pass filter circuit in the upper stage, and conceptually shows the binary data in the lower stage. FIG. 5A shows the light receiving sensor at the first frequency. (B) shows the case where the light receiving sensor is driven at the second frequency. FIG. 6 is a waveform diagram illustrating a light reception signal when a bar code displayed on the liquid crystal display device is imaged. FIG. 6A illustrates a case where the light reception sensor is driven at the first frequency. , (B) shows a case where the light receiving sensor is driven at the second frequency. FIG. 7A is a waveform diagram showing a signal obtained by converting the received light signal of FIG. 6A by a low-pass filter circuit, and FIG. 7B is a binarization circuit for the signal of FIG. 7A. It is a wave form diagram which shows the signal binarized. FIG. 8A is a waveform diagram showing a signal obtained by converting the received light signal of FIG. 6B by a low-pass filter circuit, and FIG. 8B shows the signal of FIG. 8A as a binarization circuit. It is a wave form diagram which shows the signal binarized. FIG. 9 is a flowchart illustrating a reading process performed by the optical information reading apparatus according to the second embodiment. FIG. 10 is an explanatory diagram for conceptually explaining a pixel configuration of a color display device conventionally used. FIG. 11 is an explanatory diagram for explaining a problem in reading a barcode displayed on the color liquid crystal display device.

[First embodiment]
The optical information reading apparatus according to the first embodiment will be described below with reference to the drawings.
(overall structure)
FIG. 1 is a block diagram illustrating the electrical configuration of the optical information reading apparatus according to the first embodiment. First, the overall configuration of the optical information reading apparatus 1 according to this embodiment with reference to FIG. 1 and the like. Will be described. As shown in FIG. 1, the optical information reader 1 according to the present embodiment is configured as a code reader that reads an information code B such as a barcode, and an outer case is formed by a case (not shown). It has a configuration in which various electronic components are accommodated.

  The optical information reading apparatus 1 mainly includes an optical system such as an illumination light source 20, a light receiving sensor 26, an optical filter 28, and an imaging lens 27, a memory 35, a control circuit 40, an operation switch 42, a liquid crystal display device 46, and the like. And a power source system such as a power switch 41 and a battery 49. These are mounted on a printed wiring board (not shown) or housed in a case (not shown).

  The optical system includes an illumination light source 20, a light receiving sensor 26, an optical filter 28, an imaging lens 27, and the like. The illumination light source 20 corresponds to an example of “illumination means”, and includes, for example, a red LED, a diffusion lens provided on the emission side of the LED, a condenser lens, and the like, and irradiates the red illumination light Lf. It is configured to do. In the present embodiment, the illumination light source 20 is provided on both sides of the light receiving sensor 26, and the illumination light Lf can be irradiated toward the reading object R through a reading port (not shown) formed in the case. It is configured. Examples of the reading object R include various objects such as a resin material, a metal material, paper, or a color display device described later. In the optical information reading device 1 according to the present embodiment, In the reading object R, an information code (bar code in FIG. 1) indicated by processing such as printing, direct marking, or display by a display device is a “reading object code”. In the following description, the barcode B is exemplified as the information code. However, the information code may be replaced with a two-dimensional code such as a QR code, a data matrix code, or a maxi code.

  The light receiving sensor 26 is configured to be able to receive the reflected light Lr irradiated and reflected on the reading object R or the information code B. For example, the light receiving sensor 26 is a primary element such as a C-MOS or CCD. A line sensor originally arranged or an area sensor arranged two-dimensionally corresponds to this. The light receiving sensor 26 is mounted on a printed wiring board (not shown) so that incident light incident through the imaging lens 27 can be received by the light receiving surface 26a. The light receiving sensor 26 is configured to receive a pulse signal (driving signal) having a frequency set from the control circuit 40, and the signal of each light receiving element is synchronized with the input of each pulse from the control circuit 40. Are output in order.

  In the following description, a configuration in which the light receiving sensor 26 is a line sensor will be described as a representative example. In this representative example, a light receiving signal with a lower voltage is output as the amount of received light increases in each light receiving element of the light receiving sensor 26. It has become so.

  The optical filter 28 has a function of allowing light in a predetermined frequency band corresponding to the illumination light Lf to pass therethrough and suppressing light outside the predetermined frequency band. Specifically, the light of the predetermined red light wavelength band including the wavelength of the red light emitted from the illumination light source 20 is allowed to pass, and the light deviated from the predetermined red light wavelength band (for example, green light, blue light) ), And is provided between a reading port (not shown) formed in the case and the imaging lens 27, for example. Thereby, the light (reflected light Lr) reflected by the reading object R is selectively received by the illumination light Lf, and unnecessary light greatly deviating from the wavelength of the reflected light Lr is prevented from entering the light receiving sensor 26. doing.

  The imaging lens 27 is constituted by, for example, a lens barrel and a plurality of condensing lenses accommodated in the lens barrel. In the present embodiment, the image forming lens 27 is incident on a reading port (not shown) formed in the case. The reflected light Lr is collected and a code image of the information code B is formed on the light receiving surface 26 a of the light receiving sensor 26.

  The microcomputer system is configured around a control circuit 40 and a memory 35 that can function as a microcomputer (information processing apparatus), and performs signal processing on the image signal of the information code B imaged by the optical system described above in hardware and software. It is possible.

  The control circuit 40 is a microcomputer capable of controlling the entire optical information reading apparatus 1 and includes a CPU, a system bus, an input / output interface, and the like, and has an information processing function. Various input / output devices (peripheral devices) are connected to the control circuit 40 via a built-in input / output interface. In this embodiment, a power switch 41, an operation switch 42, an LED 43, a buzzer 44, A liquid crystal display device 46, a communication interface 48, and the like are connected. The communication interface 48 can be connected to a host computer HST corresponding to the host system of the optical information reader 1.

  The memory 35 is a semiconductor memory device, and corresponds to, for example, a RAM (DRAM, SRAM, etc.) or a ROM (EPROM, EEPROM, etc.). In addition to the above-described image data storage area, the RAM of the memory 35 is configured to be able to secure a work area and a reading condition table that are used by the control circuit 40 in each processing such as arithmetic operation and logical operation. . The ROM stores in advance a predetermined program that can execute a reading process and the like that will be described later, and a system program that can control each hardware such as the illumination light source 20 and the light receiving sensor 26.

  The low-pass filter circuit 31 is provided on the output side of the light receiving sensor 26 and has a function of removing a high frequency component of the light receiving signal using the light receiving signal output from the light receiving sensor 26 as an input signal. The low-pass filter circuit 31 is configured as a known low-pass filter, passes a signal having a frequency equal to or lower than a predetermined cutoff frequency without being attenuated, and inputs a signal in a high frequency region exceeding the cutoff frequency. The higher the signal frequency, the more the output signal that has passed through the filter is suppressed (attenuated).

  The low-pass filter circuit 31 may be a known low-pass filter (known low-pass filter using an operational amplifier) configured as an inverting amplifier circuit, or may be a known low-pass filter configured as a non-inverting amplifier circuit. . Alternatively, a known CR filter that does not use an operational amplifier may be used (in this case, it is desirable to provide a separate amplifier circuit between the light receiving sensor 26 and the low-pass filter circuit 31. In the following description, the low-pass filter circuit is provided. An example in which 31 is a “known low-pass filter configured as an inverting amplifier circuit” will be described as a representative example.

  The binarization circuit 33 corresponds to an example of “binarization means”, and has a function of converting a signal output from the low-pass filter circuit 31 into binary data. This binarization circuit compares the output signal from the low-pass filter circuit 31 (light-receiving signal from which high-frequency noise has been removed) with a set threshold value, and outputs an L level signal if the threshold value is exceeded. If it is less than that, an H level signal is output. Note that the signal output from the binarization circuit 33 is stored in the memory 35 as pattern data of the information code B.

  The power supply system includes a power switch 41, a battery 49, and the like, and conduction and interruption of the drive voltage supplied from the battery 49 are controlled by turning on and off the power switch 41 managed by the control circuit 40. The battery 49 is a secondary battery that can generate a predetermined DC voltage, and corresponds to, for example, a lithium ion battery.

(Reading process)
Next, a reading process performed by the optical information reading apparatus 1 according to the present embodiment will be described with reference to FIG. FIG. 2 is a flowchart illustrating the flow of reading processing performed by the optical information reading apparatus 1 according to this embodiment.

  In the present embodiment, for example, the reading process shown in FIG. 2 is started by a predetermined operation by the user (for example, a predetermined operation on the operation switch 42), and the process of driving the illumination light source 20 is first performed (S1). In this process, a light source drive signal is given from the control circuit 40 to the illumination light source 20, and the illumination light source 20 emits red illumination light Lf.

Thereafter, a process of setting the reading mode to the first mode is performed (S2). In the present embodiment, the reading mode can be switched between a first mode (mode in which the frequency of the drive signal is set to f1) and a second mode (mode in which the frequency of the drive signal is set to f2). As the reading process No. 2 starts, the “first mode” is set with priority over the “second mode”. Note that data indicating whether the currently set mode is the “first mode” or the “second mode” is recorded in the memory 35, for example.
In the present embodiment, the control circuit 40 corresponds to an example of “mode switching means” and has a function of changing the setting between the first mode and the second mode.

  An imaging process is performed after the process of S2 (S3). In the present embodiment, the control circuit 40 corresponds to an example of a “sensor drive circuit”. When the process of S3 is started, the control circuit 40 sends a pulse signal (drive) with a set frequency to the light receiving sensor 26. Signal) is output. Specifically, a pulse signal having a frequency corresponding to the current mode is output, and when the first mode is set, the frequency of the drive signal is set to the first frequency f1 (FIG. 3 ( a)), when the second mode is set, the frequency of the drive signal is set to a second frequency f2 higher than the first frequency (see FIG. 3B). ). Immediately after the start of the reading process in FIG. 2 (immediately after the process in S2), the reading mode is set to “first mode” in S2, so that the first frequency f1 is set as shown in FIG. A pulse signal (drive signal) is output.

  The light receiving sensor 26 receives the reflected light reflected by the reading target code and transmitted through the optical filter 28 by each light receiving element, and the reflected light from the reading target code based on the amount of light received by each light receiving element. The light reception signal corresponding to the is output. Specifically, driving is performed according to a pulse signal (driving signal) given from the control circuit 40, and each signal of each light receiving element arranged in a line is sequentially input every time each pulse is inputted from the control circuit 40. Output. Therefore, when a pulse signal (drive signal) having the first frequency f1 is output from the control circuit 40 (sensor drive circuit) as shown in FIG. 3A, the light received according to the reflected light from the reading target code. When a signal is output at a speed corresponding to the first frequency f1 and a pulse signal (drive signal) of the second frequency f2 is output as shown in FIG. 3B, reflection from the code to be read is performed. A light reception signal corresponding to the light is output at a speed corresponding to the second frequency f2. For example, when the light receiving sensor 26 is configured as a line sensor in which N light receiving elements are arranged in a line, the signals of all the light receiving elements are output by inputting N pulses from the control circuit 40. In other words, the signals of all the light receiving elements are output in a shorter time at the second frequency f2 than at the first frequency f1.

  In the imaging process of S3 immediately after the process of S2, the reading mode is set to the “first mode”, and the pulse signal (drive signal: FIG. 3A) set to the first frequency f1 from the control circuit 40. Is output at a speed corresponding to the first frequency f1, and the light reception signals of all the light receiving elements are output in a slightly longer time than the case of the second frequency f2. The Rukoto.

  The light reception signal output from the light reception sensor 26 is converted into binary data by the binarization circuit 33 after the high frequency component is suppressed by the low-pass filter circuit 31 described above, and stored in the memory 35. .

  After the imaging process of S3, a decoding process is performed (S4). In this decoding process, the size and position of each bright color area and each dark color area are specified based on the binary data stored in the memory 35, and decoding is performed by a known decoding method. In the present embodiment, the control circuit 40 corresponds to an example of “decoding means”.

  After the decoding process in S4, it is determined whether or not the decoding process is successful in S5. If the decoding process is successful (S5: Yes), the decoding result is output to the liquid crystal display 46 (FIG. 1), for example. (S6).

  On the other hand, if the decoding process in S4 has failed, the process proceeds to No in S5, and it is determined whether or not both modes (first mode and second mode) have been executed (S7). At this time, if both modes are not executed (that is, only the first mode is executed and the second mode is not executed), the process proceeds to No in S7, and the reading mode is set to the second mode. (S8). Then, an imaging process (S3) and a decoding process (S4) described later are performed in the set second mode.

Next, the case where the decoding process fails in the first mode and the imaging process and the decoding process are performed after resetting to the second mode will be described in detail with reference to FIGS.
FIG. 4 is an explanatory diagram for explaining a case where a barcode (information code) displayed on the color display device is to be read. FIG. 5 conceptually shows the waveform of the bright color region converted by the low-pass filter circuit 31 in the upper stage, conceptually shows the binary data in the lower stage, and (a) shows the first frequency. The case where the light receiving sensor 26 is driven by f1 is shown, and (b) shows the case where the light receiving sensor 26 is driven at the second frequency. FIG. 6 illustrates a light reception signal when a bar code displayed on the liquid crystal display device is imaged. FIG. 6A illustrates a case where the light reception sensor 26 is driven at the first frequency f1. (B) shows a case where the light receiving sensor 26 is driven at the second frequency. FIG. 6B shows a case where the same object as that in FIG. 6A is imaged. In both FIGS. 6A and 6B, the horizontal axis represents time and the vertical axis represents voltage. Waveforms are shown, and the horizontal scale of time (time per division) is the same in (a) and (b). 7A shows a signal obtained by converting the received light signal of FIG. 6A by the low-pass filter circuit 31, and FIG. 7B shows the binary signal of FIG. 7A. A signal binarized by the digitizing circuit 33 based on a predetermined threshold is shown. Further, FIG. 8A shows a signal obtained by converting the received light signal of FIG. 6B by the low-pass filter circuit 31, and FIG. 8B shows the binary signal of FIG. 8A. A signal binarized by the digitizing circuit 33 based on a predetermined threshold is shown. 7 and 8 also show signal waveforms with the horizontal axis representing time and the vertical axis representing voltage, and FIGS. 7A, 7B, and 8A, 8B all show time on the horizontal axis. The scale (time per division) is the same.

  When the decoding process fails in the first mode, the second mode is reset and the imaging process and decoding process should be performed again. For example, as shown in FIG. The case where the barcode B displayed on the liquid crystal display device 100 provided in the terminal (mobile terminal) is read can be considered. Similar to FIG. 10, the liquid crystal display device 100 is configured by arranging a plurality of display pixels Sa configured by a combination of the R pixel Ra, the G pixel Ga, and the B pixel Ba, and as described above, the optical filter 28. , The passage of light emitted from the G pixel Ga and the B pixel Ba is suppressed more than the passage of light emitted from the R pixel (see also FIG. 4).

  In such a case, as shown in the lower part of FIG. 4 and FIG. 6A, in the waveform of the bright color region output from the light receiving sensor 26 (see WA1), a signal indicating a dark color is included as noise, Even if it is input to the low-pass filter circuit 31, since the frequency of the waveform in the light color region is low, noise can be attenuated as indicated by reference numeral WA2 in the upper part of FIG. 5 (a) and FIG. 7 (a). Therefore, noise removal is insufficient. As a result, a part of the bright color area is recognized as a dark color area as shown by reference numeral WA3 in the lower part of FIG. 5A and FIG. 7B, and this causes a decoding defect. .

  In the present embodiment, when such a decoding failure occurs, as shown in FIG. 2, the second mode is set in S8, and the imaging process of S3 is executed in the second mode. In this second mode imaging process, the control circuit 40 gives a pulse signal (drive signal) set to the second frequency f2 to the light receiving sensor 26 (see FIG. 3B). Accordingly, a light reception signal corresponding to the light emitted from the bar code B (read target code) displayed on the liquid crystal display device 100 is output at a speed corresponding to the second frequency f2, and from the time of the first frequency f1. The signals of all the light receiving elements are output in a short time.

  As shown in FIGS. 6 (a) and 6 (b), even when the time T1 is required for the signal output of a part of the light receiving sensor 26 at the first frequency f1, this is the case at the second frequency f2. The partial signal output can be performed in a shorter time T2, and the frequency of the received light signal as a whole is increased at the second frequency f2. Accordingly, as indicated by reference numeral WB1 in FIG. 6B, the frequency of the waveform in the light color region (the waveform including noise recognized as a dark color) is also the case of the first mode (reference numeral WA1 in FIG. 6A). ), And as shown by reference numeral WB2 in the upper part of FIG. 5B and FIG. 8A, the noise can be attenuated and the noise can be removed. As a result, as indicated by reference numeral WB3 in the lower part of FIG. 5 (b) and FIG. 8 (b), in the binary data, the region to be the light color region accurately indicates a value corresponding to the light color region. As a result, the decoding failure can be effectively eliminated.

  In the present embodiment, the control circuit 40 determines the setting order of the first mode and the second mode based on the program that executes the processing of FIG. It corresponds to an example of “means”. Then, the control circuit 40 functioning as the “mode switching unit” sets the first mode (the mode using the drive signal of the first frequency f1) as the “previous mode” according to the order defined by the program, When the decoding process performed in the state set to the first mode fails, the setting is changed to the second mode (the mode using the drive signal of the second frequency f2).

(Main effects of this embodiment)
In the optical information reading apparatus 1 according to the present embodiment, an optical filter 28 that allows light in a predetermined frequency band corresponding to illumination light to pass and suppresses light other than the predetermined frequency band is provided. The reflected light from the light is received by the light receiving sensor 26 through the optical filter 28. By doing in this way, disturbance light other than the reflected light which illumination light reflected in the reading object code | cord | chord can be removed effectively.
On the other hand, with such a configuration, when the information code displayed on the color display device is the code to be read, a part of pixels in the area displaying the bright color pattern (pixels that emit light suppressed by the optical filter) There is a concern that the light from the light is suppressed by the optical filter 28, and the waveform component indicating the dark color is included as noise in the waveform of the bright color pattern portion in the light reception signal.
In contrast, in this embodiment, when the first mode is set, the frequency of the drive signal is set to the first frequency f1, and when the second mode is set, the frequency of the drive signal is set to the first frequency. The setting is changed to the second frequency f2, which is larger than the frequency f1. When the drive signal having the first frequency f1 is output, a light reception signal corresponding to the reflected light from the reading target code is output at a speed corresponding to the first frequency f1, and the second frequency f2 is output. Is output at a speed corresponding to the second frequency f2.
In this case, when the information code displayed on the color display device is to be read, and the waveform component indicating the dark color is included as noise in the waveform of the bright color pattern region, the light receiving sensor at the second frequency f2. 26 can be driven to relatively increase the frequency of the waveform of the bright color pattern region (the waveform of the bright and dark alternating signal including the normal signal indicating the bright color and the noise indicating the dark color). Thereby, when the received light signal is input to the low-pass filter circuit 31, the degree of attenuation of the signal in the light color pattern region increases, and noise indicating the dark color included in the signal in the light color pattern region is effectively removed. be able to.
On the other hand, since it is possible to drive the light receiving sensor at the first frequency f1 as necessary, it is difficult to erroneously recognize the bright color pattern area, such as when reading an information code attached to a paper medium (that is, bright In the case where it is difficult for the received light signal in the color pattern area to contain dark-colored noise), the driving frequency can be suppressed to a setting that is advantageous for finer reading.

  Further, the color display device to be read has a configuration in which a plurality of display pixels Sa configured by a combination of R pixel Ra, Ga pixel, and Ba pixel are arranged. In this way, an RGB color display device widely used in various places is used as a reading object, and an information code displayed on the color display device is used as a reading object code, and such an information code can be read satisfactorily. Thus, the convenience for the user can be improved.

  Specifically, a mobile terminal that is carried and used in various places is used as an object to be read, and an information code displayed on the mobile terminal is used as a read target code, and such an information code can be satisfactorily read. By doing so, user convenience can be further enhanced.

  Further, the optical information reading apparatus 1 according to the present embodiment includes “mode order defining means” that determines the setting order of the first mode and the second mode, and the order defined by the “mode order defining means”. Accordingly, one of the first mode and the second mode is set as the previous mode, and when the decoding process performed in the state set in the previous mode fails, the setting is changed to the other mode. In this way, when the decoding process fails in one mode, it is possible to quickly and smoothly switch to the other mode and execute the decoding process again in the other mode, which imposes a special burden on the user. Therefore, it is possible to effectively increase the decoding success probability.

[Second Embodiment]
Next, a second embodiment will be described with reference to FIG. FIG. 9 is a flowchart illustrating the flow of reading processing performed by the optical information reading apparatus according to this embodiment.

  In the present embodiment, only the reading mode setting method in the reading process is different from that of the first embodiment, and other than that is the same as that of the first embodiment. For example, the description based on FIGS. 1 and 3 to 8 is the same as that of the first embodiment, and therefore, these drawings will be referred to as appropriate. As for the reading process, the process of S21 of FIG. 9 is the same as S1 of FIG. 2, and the imaging process of S25 and the decoding process of S26 in each mode performed in the reading process of FIG. This is the same as the imaging process in S3 and the decoding process in S4 in each mode described in the embodiment. Therefore, description of these details is omitted.

  In this embodiment, the decoding result when the decoding process is performed in the first mode or the second mode is associated with the mode in which the decoding process is performed, and the memory 35 (the memory 35 is an example of “storage means”). In the first mode and the second mode, the mode in which the decoding process was successful last time is preferentially set based on the stored contents of the memory 35. In the present embodiment, the program and control circuit 40 in FIG. 9 corresponds to an example of “mode order defining means”.

  Specifically, as shown in FIG. 9, after the illumination light source 20 is driven in S21, the stored contents of the memory 35 are confirmed, and it is confirmed whether or not the previous successful reading mode is the “second mode”. In the present embodiment, the memory 35 stores whether the previous successful mode is the first mode or the second mode, and the determination process is performed with reference to this in S22. If the previous successful reading mode is not the second mode, the process proceeds to No in S22, and is set to “first mode” (or maintains the setting of the first mode) (S23).

  When the first mode is set in S23, the same imaging process (S25) and decoding as the imaging process (S3) and decoding process (S4) performed in the first embodiment in the first mode. Processing (S26) is performed. If the decoding process is successful, the process proceeds to Yes in S27 to output a decoding result (S28), and the successful mode (first mode) is stored as the previous successful mode (S29). On the other hand, when the decoding process has failed (for example, when decoding using the barcode of the liquid crystal display device 100 as a reading target code as described in the first embodiment), the process proceeds to No in S27. It is determined whether or not both modes have been executed (S30). If the second mode is not executed, the process proceeds to No in S30, and after changing the setting to the other second mode (S31), the imaging process in S23 and the decoding process in S26 are performed.

  On the other hand, if it is determined in S22 that the previous successful reading mode is “second mode”, the process proceeds to Yes in S22, and the reading mode is set to “second mode” (S24). Then, imaging processing (S25) and decoding processing (S26) similar to the imaging processing (S3) and decoding processing (S4) performed in the first embodiment in the second mode are performed. If the decoding process is successful, the process proceeds to Yes in S27 to output a decoding result (S28), and the successful mode (second mode) is stored as the previous successful mode (S29). On the other hand, if the decoding process has failed, the process proceeds to No in S27 to determine whether or not both modes have been executed (S30). In this case, when the first mode is not executed, the process proceeds to No in S30, and after changing the setting to the other first mode (S31), the imaging process of S23 and the decoding process of S26 are performed.

  In the optical information reading apparatus according to the second embodiment, a memory 35 that can store the decoding result when the decoding process is performed in the first mode or the second mode in association with the mode in which the decoding process is performed ( Storage means) is provided, and based on the storage contents of the memory 35 (storage means), the mode in which the decoding process was last successful is preferentially set out of the first mode and the second mode. The mode in which the decoding process was successful last time is more likely to succeed in the decoding mode than the other mode, and if this mode is set with priority, the success probability of the decoding process can be effectively increased. The reading process can be speeded up.

[Other Embodiments]
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.

  In the above embodiment, an example in which the light receiving sensor 26 is configured as a line sensor (one-dimensional sensor) has been shown as a representative example.

  In the above-described embodiment, an example in which the illumination light source 20 that emits red illumination light is provided and the optical filter 28 that selectively passes light in a predetermined frequency band corresponding to red is provided. However, the present invention is not limited to this configuration. . For example, an illumination light source that emits illumination light of other colors (green, blue, etc.) may be provided, and an optical filter that selectively transmits the other colors may be provided.

  In the above-described embodiment, the configuration in which the frequency of the sensor drive signal supplied from the control circuit 40 to the light receiving sensor 26 can be switched in two stages is exemplified.

  In the above embodiment, the liquid crystal display device 100 (FIG. 4) is exemplified as the color display device. However, an information code displayed on another color display device such as an EL display may be used as a reading target code.

DESCRIPTION OF SYMBOLS 1 ... Optical information reader 20 ... Illumination light source (illumination means)
26... Light receiving sensor 28... Optical filter 31 .. Low pass filter circuit 33... Binarization circuit (binarization means)
35 ... Memory (storage means)
40... Control circuit (sensor drive circuit, decoding means, mode switching means, mode order defining means)
DESCRIPTION OF SYMBOLS 100 ... Color display apparatus Ra ... R pixel Ga ... G pixel Ba ... B pixel Sa ... Display pixel

Claims (6)

An optical information reading device capable of reading an information code displayed on a color display device and an information code attached to an object as a reading target code,
Illuminating means for illuminating the reading target code with illumination light;
An optical filter that transmits light in a predetermined frequency band corresponding to the illumination light and suppresses light other than the predetermined frequency band; and
A light receiving sensor that receives reflected light from the reading target code via the optical filter and outputs a light receiving signal corresponding to the reflected light;
A sensor driving circuit that outputs a driving signal of a set frequency to the light receiving sensor;
A low-pass filter circuit configured to receive the light reception signal output from the light reception sensor, and to suppress a signal having a frequency equal to or higher than a predetermined cutoff frequency;
Binarization means for binarizing the received light signal output from the low-pass filter circuit;
Decoding means for performing decoding processing based on the binarized signal generated by the binarization means;
Mode switching means capable of changing the setting between the first mode and the second mode;
With
The sensor drive circuit sets the frequency of the drive signal to the first frequency when set to the first mode by the mode switching means, and the drive signal when set to the second mode. The frequency is set to a second frequency that is higher than the first frequency.
The light receiving sensor responds to the first frequency with respect to the light receiving signal corresponding to the reflected light from the code to be read when the driving signal having the first frequency is output from the sensor driving circuit. When the drive signal having the second frequency is output, the light reception signal corresponding to the reflected light is output at a speed corresponding to the second frequency. An optical information reader.   2. The optical information reading apparatus according to claim 1, wherein the color display device is formed by arranging a plurality of display pixels configured by combinations of R pixels, G pixels, and B pixels. The illumination means is configured to irradiate the red illumination light,
The optical information reading apparatus according to claim 2, wherein the optical filter suppresses passage of light emitted from the G pixel and B pixel rather than passage of light emitted from the R pixel.   The optical information reader according to claim 1, wherein the color display device is a display device provided in a mobile terminal. A mode order defining means for determining a setting order of the first mode and the second mode;
The mode switching means sets one of the first mode and the second mode as the previous mode according to the order defined by the mode order defining means, and performs the operation in the state set to the previous mode. 5. The optical information reading apparatus according to claim 1, wherein, when the decoded processing fails, the setting is changed to the other. 6. Storage means capable of storing the result of the decoding process performed in the first mode or the second mode in association with the mode in which the decoding process is performed;
6. The mode order defining means preferentially sets a mode in which the decoding process has been successful last time out of the first mode and the second mode based on the stored contents of the storage means. An optical information reading device described in 1.

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