JP4622992B2 - Optical information reader - Google Patents

Description

The present invention relates to an optical information reading apparatus that reads optical information such as a barcode printed or pasted on a product or the like.

2. Description of the Related Art There is known an optical information reading apparatus that attaches a substrate such as paper printed with optical information such as a barcode to an article or document, optically reads it, and identifies the article. Such an optical information reading device illuminates optical information to which a reading port is directed from a light irradiation means such as an LED inside the case, and guides light reflected from the optical information to the inside of the case from the reading port. The image is formed on a CCD or the like, and the information represented by the optical information is decoded from the brightness distribution of the image. Here, Patent Document 1 discloses a barcode reader capable of setting an exposure time of a one-dimensional sensor and an amplification factor of an amplifier circuit.
JP 2001-60244 A

Optical information readers can convert light signals into electrical signals normally when the light incident on the CCD sensor becomes strong (for example, sunlight) and the sensor output becomes saturated in a high ambient illuminance environment. In general, however, reading is impossible, but an unexpected electric signal may be output, which may cause misreading. For example, if the reflected light intensity from the label surface is strongly saturated due to strong light hitting the label surface from one side, a part of the barcode is lost and the data is different from the barcode data. Sometimes it can be decoded. Specifically, phenomena such as lack of the number of digits of CODABAR occur. Alternatively, depending on the type of sensor, a phenomenon may occur in which the waveform of the saturated portion is reversed, and the black and white data may be completely reversed. Since there are bar codes that have different data due to the inversion of white and black, if the sensor output is saturated, the possibility of misreading is unavoidable.

In general, optical information readers adjust the exposure time of the light receiving sensor stepwise so that the output of the light receiving sensor does not saturate in a high ambient illuminance environment. A light receiving sensor output voltage can be obtained. Specifically, as shown in FIG. 10A, the exposure time is gradually increased as exposure time 1 → exposure time 2 → exposure time 3 → exposure time 4 and reading condition a (for example, signal amplification factor a) The decoding is repeated while changing the reading condition b (for example, the threshold value b for the binarization of the signal), the reading condition c (for example, the decoding condition c), etc. Processing to return. For example, when reading is not possible under the reading condition c of the exposure time 1, reading is attempted under the reading condition d of the exposure time 2, and when reading is not possible here, reading is attempted under the reading condition e of the exposure time 2. For this reason, it takes time to shift to a readable exposure time, which leads to deterioration in reading feeling.

Note that the ambient illuminance resistance can be enhanced by shortening the exposure time. However, in general, an inexpensive CCD sensor does not have a shutter function, and shortening the exposure time has a limit in shortening the exposure time because the entire signal waveform is shortened and the waveform resolving ability is reduced. For this reason, if there is a possibility that the scan data is finally wrong, it is necessary to cancel the barcode data.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an optical information reader capable of reading an information code in a short time without error under various ambient illuminance environments. There is to do.

In order to achieve the above object, the invention of claim 1 is an optical information reader for decoding an information code from an image captured by the light receiving sensor 12,
Saturation detecting means 20 for directly monitoring the output voltage from the light receiving sensor 12 to detect the presence or absence of saturation of the light receiving sensor output;
Saturation intensity estimation means 38 for estimating the saturation intensity by integrating the time when saturation is detected;
Bright decoding stop means (S20, S24) for preventing the decoding of the information code from the image when the saturation intensity is not less than a predetermined value;
Technical features include dark exposure condition setting means (S22, S26) for setting the exposure condition for capturing the next image to be dark according to the saturation intensity.

In the optical information reader according to the first aspect, the output voltage from the light receiving sensor is directly monitored to detect the presence or absence of saturation of the light receiving sensor output, and the saturation intensity is estimated by integrating the time when the saturation is detected. Then, when the saturation intensity is greater than or equal to a predetermined value, the information code from the image is not decoded. Therefore, when the output of the light receiving sensor is saturated and it is difficult to decode the information code from the image, the decoding is not performed. Can be eliminated. In particular, when a light receiving sensor whose output is inverted when saturated, an information code can be prevented from being misread. Further, the information code is read by setting the exposure condition for capturing the next image to be dark according to the saturation intensity without decoding. For this reason, an information code can be read in a short time under various ambient illuminance environments.

According to another aspect of the optical information reading apparatus of the present invention, in order to set a first exposure condition having a dark exposure condition and a second exposure condition that is darker than the first exposure condition in accordance with the magnitude of the saturation intensity. The exposure conditions according to the ambient brightness can be set quickly, and the information code can be read in a short time under various ambient illuminance environments.

According to another aspect of the optical information reading device of the present invention, the output voltage from the light receiving sensor is monitored to detect whether or not the readable voltage is reached, and the underexposure intensity is estimated by integrating the time when the readable voltage is detected. In accordance with the insufficient intensity, the exposure condition for capturing the next image is set to be brighter. For this reason, when the exposure is insufficient, the information code is read by setting the exposure condition for capturing the next image to be bright according to the underexposure intensity. For this reason, an information code can be read in a short time under various ambient illuminance environments.

In the optical information reading apparatus according to claim 4, in order to prevent the information code from being decoded from the image when the underexposure intensity is not more than a predetermined value, the decoding is performed in an excessively dark illuminance environment where the exposure condition is not suitable. You can eliminate wasted time trying.

[First embodiment]
Hereinafter, a first embodiment in which an optical information reader of the present invention is applied to a printed barcode optical information reader will be described with reference to the drawings. First, an outline of the configuration of the optical information reading apparatus 10 according to the first embodiment will be described with reference to the explanatory diagram of FIG.
The barcode B is illuminated by the light emitting diodes 22a and 22b, the barcode image is formed on the CCD sensor 12 through the imaging lens 24, the optical signal is converted into an electrical signal by the CCD sensor 12, and the signal is amplified. After being amplified by the circuit 14 and binarized by the binarization circuit 16, it is decoded by the decoding unit 32 of the CPU 30. The CPU 30 adjusts the exposure time of the CCD sensor by the sensor drive control unit 42 when the decoding fails and when saturation of the output of the CCD sensor is detected, and the amplification circuit control unit 36 adjusts the amplification circuit 14. The binarization circuit controller 34 adjusts the binarization threshold value in the binarization circuit 16.

In the first embodiment, saturation of the output of the CCD sensor 12 is monitored. For this purpose, the output signal of the CCD sensor 12 is applied to the inverting input side of the operational amplifier 20, and the voltage of the voltage dividing circuit 18 in which the saturation output voltage of the CCD sensor 12 is set is applied to the non-inverting input side. The voltage dividing circuit 18 outputs the potential of the middle point of two resistors to which one side is grounded and the power supply voltage is applied to the other side. Thereby, the operational amplifier 20 compares the voltage level of the output signal of the CCD sensor 12 with the voltage of the voltage dividing circuit 18 and binarizes it. That is, the output of the operational amplifier 20 is inverted when the output of the CCD sensor 12 is saturated. Then, the timer 38 of the CPU 30 accumulates the time when the output is inverted. The approximate saturation intensity of the CCD sensor 12 is estimated from this integration time.

4A and 4B are graphs showing the difference in the output waveform of the CCD sensor 12 depending on the ambient illuminance. FIG. 4A shows the output waveform when the ambient illuminance is 5000 lx. ) Shows an output waveform when the ambient illuminance is 10,000 lx. 3A shows the output waveform of the CCD sensor when the ambient illuminance is bright, FIG. 4B shows the output waveform when the ambient illuminance is very bright, and FIG. 3C shows when the CCD sensor output is not saturated. It is explanatory drawing which shows these output waveforms. As shown in FIGS. 4A and 4B, the CCD sensor 12 is applied with a driving voltage of 5 V, and the voltage value of the output waveform decreases when the illuminance is high, and reaches the saturation voltage when saturated. . In the first embodiment, the output of the operational amplifier 20 is inverted by saturation of the output of the CCD sensor 12 by setting a saturation voltage or a voltage slightly higher than this as the voltage of the voltage dividing circuit 18. Then, the timer 38 of the CPU 30 accumulates the time when the output is inverted.

The optical information reading device can normally read without problems even when the ambient illuminance is 0 lx by self-illumination (illumination light from the light emitting diodes 22a and 22b in the first embodiment). For this reason, it becomes a problem when ambient illuminance is too bright. In the optical information reading apparatus according to the first embodiment, in order to cope with a case where the brightness is too bright, the voltage of the voltage dividing circuit 18 is set to a voltage slightly higher than the saturation voltage of the CCD sensor 12, and the time exceeding the saturation voltage is integrated by the timer 38. Then, this is used as the sensor saturation time, and an optimum exposure time is calculated from the accumulated time, and a short exposure time adapted to the ambient illuminance that is too bright is newly set. If it is determined that the saturation has been reached, the decode data (image data) is canceled regardless of whether or not decoding is established.

Switching of reading conditions by the optical information reading apparatus of the first embodiment will be described with reference to the explanatory diagram of FIG.
In the optical information reading apparatus of the first embodiment, the reading condition is set in the same manner as in the prior art described above with reference to FIG. 10A unless the ambient illuminance is too bright and the output of the CCD sensor 12 is saturated. The exposure time is gradually increased from exposure time 1 → exposure time 2 → exposure time 3 → exposure time 4 to read condition a (signal amplification factor a), read condition b (signal binarization threshold b), Decoding is repeated while changing the reading condition c (decoding condition c), etc., and when decoding cannot be performed at the exposure time 4, processing is performed to return to the exposure time 1. For example, if reading is not possible under the reading condition c (decoding condition c) at the exposure time 1, reading is attempted under the reading condition d (signal amplification factor d) at the exposure time 2, and exposure is also performed when reading is not possible here. Reading is attempted under the reading condition e at time 2 (threshold value e for binarizing the signal). Then, when the reading is performed, the reading condition is set and the next reading is performed.

On the other hand, in the optical information reading apparatus of the first embodiment, when it is detected that the ambient illumination is too bright (saturation of the CCD sensor 12) from the integrated value of the time when the output of the operational amplifier 20 is inverted, the image data captured is decoded. The exposure time is adjusted according to the saturation intensity. For example, when the saturation of the CCD sensor 12 is detected under the reading condition j (signal amplification factor j) of the exposure time 4, when the saturation intensity time is short as shown in FIG. As shown in FIG. 3B, when the saturation intensity time is long, the exposure time 1 is started.

Processing by the optical information reading apparatus of the first embodiment will be described with reference to the flowchart of FIG.
First, initial values are set (S12), and an image is captured (S13). Then, the sensor saturation determination time integrated value Ta stored in the timer 38 is called (S14), and it is determined whether the sensor saturation determination time integrated value Ta is 0, that is, whether the output of the CCD sensor 12 is saturated. (S16). Here, when the output of the CCD sensor 12 is saturated (S16: Yes), it is determined whether or not the sensor saturation determination time integrated value Ta is longer than the threshold time T (S18). If the saturation time is shorter than the threshold time T as shown in FIG. 3A and the saturation intensity is relatively low (S18: Yes), the captured image data is cleared (S20), and the exposure shown in FIG. The process jumps to the reading condition d at time 2 (S22), and image capture is performed (S13). Here, as shown in FIG. 3B, when the saturation intensity is relatively higher than the threshold time T (S18: No), the captured image data is cleared (S24), and the exposure time 1 The reading condition a is jumped to (S26), and the image is captured (S13).

On the other hand, if the sensor output waveform does not reach the saturation voltage as shown in FIG. 3C, the determination of S16 described above becomes Yes, and the decoding process is performed based on the captured image data (S30). Here, when the decoding is successful (S32: Yes), the process is terminated. On the other hand, if the decoding fails (S32: No), it is determined whether the reading condition is final (S34). When the reading condition is final, that is, the reading condition 1 at the exposure time 4 shown in FIG. (S34), the process jumps to the reading condition g for the exposure time 3 (S36), and performs image capture (S13). If the reading condition is not final (S34: No), the reading condition and the exposure time are changed in order in the routine shown in FIG. 5 (S38).

In the optical information reader of the first embodiment, the output voltage from the CCD sensor 12 is directly monitored by the operational amplifier 20 to detect the presence or absence of saturation of the output of the CCD sensor 12, and the time when saturation is detected (sensor saturation determination time). The integrated value Ta) is integrated by the timer 38 to estimate the saturation intensity. Then, when the output is saturated, or when the saturation intensity is equal to or higher than a predetermined value, the information code from the image is not decoded. For this reason, when the output of the CCD sensor 12 is saturated and it is difficult to decode the information code from the image, the decoding is not performed. Waste can be eliminated. Further, without decoding, the information code is read by setting the exposure condition for capturing the next image to be dark according to the saturation intensity. For this reason, an information code can be read in a short time under various ambient illuminance environments.

Further, in the optical information reading apparatus according to the first embodiment, the first exposure condition (S22) with dark exposure conditions and the second exposure that is darker than the first exposure conditions according to the magnitude of the saturation intensity. Since the condition (S26) is set, the exposure condition according to the ambient brightness can be quickly set, and the information code can be read in a short time under various ambient illuminance environments.

Further, the output voltage from the CCD sensor 12 is directly monitored by the operational amplifier 20 without passing through the amplifier circuit 14 to detect whether the output of the CCD sensor 12 is saturated. In the first embodiment, the drive voltage of the CCD sensor 12 is 5V, and the drive voltage of the operational amplifier 20 is also 5V. Therefore, when the output of the 5V CCD sensor 12 is amplified by the amplifier circuit 14 and then input to the operational amplifier 20, the output of the 5V drive operational amplifier 20 is inverted before the output of the CCD sensor 12 is saturated. In other words, in the first embodiment, the output voltage from the CCD sensor 12 is not amplified but directly monitored by the operational amplifier 20 so that the output saturation timing can be accurately detected.

[Second Embodiment]
Next, an optical information reading apparatus according to a second embodiment of the present invention will be described with reference to FIGS.
In the first embodiment described above, when it is detected that the ambient illumination is too bright (saturation of the CCD sensor 12), the exposure time is adjusted according to the saturation intensity. On the other hand, the optical information reading apparatus of the second embodiment adjusts the exposure time not only when the ambient illumination is too bright but also when the illumination is too dark.

FIG. 6 is a block diagram illustrating a configuration of the optical information reading apparatus according to the second embodiment.
In the first embodiment described above with reference to FIG. 1, the output of the CCD sensor 12 is binarized by the operational amplifier 20 to detect the output saturation of the CCD sensor 12. On the other hand, in the second embodiment, the output of the CCD sensor 12 is digitized from a predetermined saturation threshold level by multi-value (for example, 256 gradations) by the A / D conversion circuit 50. When the signal level is high, the output of the CCD sensor is saturated, and when the digitized signal level is higher than a predetermined reading threshold level, the output level is readable. Here, the adjustment of the exposure time by integrating the output saturation time with the timer 38 is the same as in the first embodiment, but in the second embodiment, the time when the CCD sensor readable output level is reached is determined by the timer. To adjust the exposure time.

FIG. 9 is an explanatory diagram of switching of reading conditions by the optical information reading apparatus of the second embodiment. FIG. 9A shows switching of the exposure time when the output of the CCD sensor 12 is saturated, as in the first embodiment. In the case of the output waveform of the CCD sensor with a bright ambient illuminance as shown in FIG. 8A, the output waveform jumps to the exposure time 2 and the output waveform when the ambient illuminance is very bright as shown in FIG. 1 is set to the exposure time 1.

FIG. 9B shows switching of the exposure time when the integrated time (readable voltage integrated time Tb) within one scan when the output of the CCD sensor 12 reaches the readable voltage is equal to or less than the setting. Here, as shown in FIG. 8C, when the integration time Tb within one scan that has reached the readable voltage is equal to or less than the threshold time T1, the C pattern indicated by the chain line in FIG. Switch. That is, the switching pattern jumps from exposure time 1 to exposure time 3, shifts from exposure time 3 to exposure time 4, and returns from exposure time 4 to exposure time 1. The reason for jumping from the exposure time 1 to the exposure time 3 is that sufficient illuminance is not obtained at the exposure time 1, and therefore underexposure is expected even at the exposure time 2.

On the other hand, as shown in FIG. 8D, when the integrated time Tb within one scan that has reached the readable voltage exceeds the threshold time T1, switching is performed with a D pattern indicated by a solid line in FIG. 9B. . That is, it is a switching pattern in which the exposure time 1 shifts to the exposure time 2, the exposure time 2 shifts to the exposure time 3, and the exposure time 3 returns to the exposure time 1. When the integration time Tb exceeds the threshold time T1, the illumination light with sufficient brightness is obtained, so the longest exposure time 4 is not set.

Processing by the optical information reading apparatus according to the second embodiment will be described with reference to the flowchart of FIG.
Here, the processing from S12 to S26 is the same as that of the first embodiment described above with reference to FIG.
If there is no saturation of the output of the CCD sensor 12 (S16: Yes), an integrated time (readable voltage integrated time Tb) within one scan when the output of the CCD sensor 12 reaches the readable voltage is called (S54), It is determined whether or not the output of the CCD sensor 12 has reached an image readable level by comparing the readable voltage integration time Tb with the threshold time T1 (S56). Here, as described above with reference to FIG. 8C, when the readable voltage integration time Tb is shorter than the threshold time T1, that is, the output of the CCD sensor 12 has not reached the level at which image reading is possible. In this case (S56: No), the captured image data is cleared (S58), the exposure time is switched along the transition pattern C described above with reference to FIG. 9B (S60), and the image is captured (S60). S13).

On the other hand, in the determination of whether or not the output of the CCD sensor 12 at S56 has reached a level at which image reading is possible, the readable voltage integration time Tb is the threshold time as described above with reference to FIG. When it is longer than T1, that is, when the output of the CCD sensor 12 reaches a level at which image reading is possible (S56: Yes), decoding is performed (S30), and it is determined whether or not the decoding is successful (S32). ). If the decoding is successful (S32: Yes), the process is terminated. On the other hand, when decoding fails (S32: No), the exposure time is switched along the transition pattern D described above with reference to FIG. 9B (S33), and image capture is performed (S13).

In the optical information reader according to the second embodiment, the output voltage from the CCD sensor 12 is monitored to detect whether the voltage reaches the readable voltage (S54), and the time when the readable voltage is detected is integrated to calculate the underexposure intensity. And the exposure condition for capturing the next image is set to be bright according to the underexposure intensity. For this reason, when the exposure is insufficient, the exposure condition for capturing the next image is set to be bright according to the underexposure intensity (S60, S33), and the information code is read. Thereby, an information code can be read in a short time under various ambient illuminance environments.

In the optical information reading apparatus of the second embodiment, when the underexposure intensity is less than or equal to a predetermined value (S56: No), the image data is cleared so that the information code is not decoded from the image data (S58). ), It is possible to eliminate wasted time trying to decode in an excessively dark illuminance environment where the exposure conditions are not suitable.

FIG. 10B shows the switching of the exposure time when the CCD sensor 12 is not saturated in the modification of the second embodiment.
Although exposure time 1 and exposure time 2 are too dark to be suitable for imaging, but when the output of CCD sensor 12 is not saturated, exposure time 1 and exposure time 2 are not performed, exposure time 3 and exposure time 4 are set. It is also preferable to switch to exposure time 1 and exposure time 2 only when the output is saturated and the CCD sensor 12 is saturated.

In the above-described embodiment, an example in which the configuration of the present invention is applied to an optical information reading device that reads a barcode is described. However, the configuration of the present invention can be applied to an optical information reading device that reads a two-dimensional code such as a QR code. Needless to say.

It is a block diagram which shows the structure outline | summary of the optical information reader which concerns on 1st Embodiment of this invention. It is a flowchart which shows the process in the optical information reader which concerns on 1st Embodiment. 3A shows the output waveform of the CCD sensor when the ambient illuminance is bright, FIG. 3B shows the output waveform when the ambient illuminance is very bright, and FIG. 3C shows the output waveform when the ambient illuminance is not saturated. It is explanatory drawing shown. 4A and 4B are graphs showing the difference in output waveform of the CCD sensor depending on the ambient illuminance. FIG. 4A shows the output waveform when the ambient illuminance is 5000 lx, and FIG. Indicates an output waveform when the ambient illuminance is 10,000 lx. It is explanatory drawing of the switching of the reading conditions by the optical information reader of 1st Embodiment. It is a block diagram which shows the structure outline | summary of the optical information reader which concerns on 2nd Embodiment. It is a flowchart which shows the process in the optical information reader which concerns on 2nd Embodiment. 8A shows the output waveform of the CCD sensor when the ambient illuminance is bright, FIG. 8B shows the output waveform when the ambient illuminance is very bright, and FIG. 8C shows when the illumination is very dark. FIG. 8D is an explanatory diagram showing the output waveform when the illumination is dark. It is explanatory drawing of the switching of the reading conditions by the optical information reader of 2nd Embodiment. FIG. 10A is an explanatory diagram of switching of reading conditions by a conventional optical information reader, and FIG. 10B is an explanatory diagram of switching of exposure conditions when not saturated in the embodiment.

Explanation of symbols

12 CCD sensor (light receiving sensor)
14 Amplifying circuit 16 Binary circuit 18 Voltage dividing circuit 20 Operational amplifier (saturation detecting means)
30 CPU
38 timer (saturation intensity estimation means)
40 Timer value integration unit 50 A / D conversion circuit

Claims (4)

An optical information reader that decodes an information code from an image captured by a light receiving sensor,
Saturation detecting means for directly monitoring the output voltage from the light receiving sensor and detecting the presence or absence of saturation of the light receiving sensor output,
A saturation intensity estimating means for estimating the saturation intensity by integrating the time when saturation is detected;
A bright decoding stop means for not decoding the information code from the image when the saturation intensity is equal to or higher than a predetermined value;
An optical information reading apparatus comprising: dark exposure condition setting means for setting an exposure condition for capturing the next image to be dark according to the saturation intensity. The dark exposure condition setting means sets a first exposure condition having a dark exposure condition and a second exposure condition that is darker than the first exposure condition in accordance with a saturation intensity. The optical information reader according to claim 1. Underexposure detection means for monitoring the output voltage from the light receiving sensor and detecting underexposure depending on whether it reaches a readable voltage;
Underexposure intensity estimation means for estimating the underexposure intensity by integrating the time when the readable voltage is detected;
3. The optical information reading apparatus according to claim 1, further comprising: a bright exposure condition setting unit that sets an exposure condition for capturing the next image to be bright according to the underexposure intensity. 4. The optical information reading apparatus according to claim 3, further comprising dark decoding stop means for preventing decoding of an information code from an image when the underexposure intensity is not more than a predetermined value.

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