JP3518929B2 - Optical reader - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical reading device for optically scanning a symbol having a portion having different light reflection characteristics such as a bar code, and particularly to a portable and distant symbol. The present invention relates to an optical reading device having an aiming function of aiming and reading.

[0002]

2. Description of the Related Art Conventionally, printed on articles, or
Various optical reading devices and optical scanning devices have been developed which optically read a symbol such as a barcode symbol indicating information on the article, which is printed on a tag or the like attached.
The bar code symbol itself is a coded pattern in which bars and spaces of various widths are connected, and the bars and spaces have different light reflectivities. The optical reader and optical scanner optically scan the bar code symbol to read and decode the pattern.

These optical scanning devices emit laser light
A user emits it from a portable laser head, aiming the laser beam at the symbol to be read,
The laser beam is scanned so as to cross the bar code symbol, the scanning device detects the laser reflected light, and the detected reflected light signal is processed and decoded.

Usually, a visible red semiconductor laser having a wavelength of 675 nanometers (675 nm) is used as the laser light source. However, this wavelength is near the visible limit, and the helium-neon gas laser (wavelength 633n
m) Not as clearly visible. Especially when scanning a distant barcode or a barcode placed in a place with high ambient illuminance (bright place), the visibility of the scanning line is not sufficient, so it is easy to aim at the desired barcode,
I couldn't scan accurately.

For this reason, there has been proposed a scanning device having a plurality of scanning modes as disclosed in JP-A-2-144786 and JP-A-4-280388.
Specifically, two scanning functions are set and read: an aiming mode with a narrow scanning angle of laser light (for example, a scanning angle of 1 to 5 °) and a scanning mode with a larger scanning angle (for example, 20 to 40 °). There has been proposed an optical reading apparatus that aims at a barcode in a desired aiming mode according to a distance to an article to be processed and then performs decoding in a scan mode.

[0006]

However, in the optical reader according to the above-mentioned publication, the scanning angle is very small in the aiming mode, so that the user or a person in the vicinity accidentally looks at the beam. The laser light was continuously emitted to the eyes, which was dangerous. further,
Even in a scan mode where the scan angle is relatively large, there is a similar risk when the scan mechanism fails and the scan angle decreases or the scan stops. In particular, reading for long distances is more dangerous because it uses a laser beam with a high power exceeding 1 mW.

Therefore, an object of the present invention is to provide an optical reading device which can be easily aimed at a desired patterned symbol, has improved safety, and has high reliability.

[0008]

In order to achieve the above object, the present invention provides a light source composed of a semiconductor laser in a scanning device for optically reading information from symbols patterned by bars and spaces having different reflectances. A power control means for controlling the emission power of the light source, a polarization scanning means for polarizing the emitted light from the light source to a predetermined angle and scanning a barcode, and a polarization scanning amount control for controlling the polarization amount by the polarization means. Means, an abnormal laser stopping means for monitoring the abnormal operation of the polarizing means and stopping the laser emission power when the abnormal operation is detected, a prohibiting means for prohibiting the operation of the abnormal laser stopping means, and various emission operations. A plurality of scanning modes in which a power and a polarization amount are combined, and a scanning mode selecting unit for selecting a desired scanning mode is provided. Based on the scanning mode selected by, providing an optical reading device for determining the light source of the emission power, polarized light quantity of light emitted from the light source, the operation permission or prohibition of the abnormality detecting means. The wavelength of the laser beam generated by the semiconductor laser is 660 nm or less.

[0009]

Of the operating conditions determined based on the selected scanning mode having the above configuration, in the first mode, the emission power of the light source is lowered and the polarization amount of the emitted light is reduced.
The operation of the anomaly detection means is prohibited, and a desired patterned symbol is searched for. Then, after the symbol to be read is selected, the second scanning mode is switched to the next, and the output power of the light source is increased to a level suitable for reading and the polarization amount of the emitted light is set to a value capable of scanning the entire symbol. The size is increased to permit the operation of the abnormality detecting means. Further, the visibility of the scanning line is improved by shortening the wavelength of the laser diode to 660 nm or less.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows an external configuration of an optical reading apparatus as an embodiment according to the present invention and will be described.

The reading device 1 has a shape suitable for carrying, for example, a pistol type, and a trigger 3 is provided near a position where the index finger is naturally placed when the user holds the handle 2. ing. When the trigger 3 is pulled, the barcode scanning light composed of the laser light is emitted from the scanning substrate (scanning substrate 11 shown in FIG. 2) provided in the beam emitting portion 5 through the transparent window 4. In addition, a host computer 6 for performing various data processing is connected to the reading device by a cable 7.

FIG. 2A shows a cross-sectional top view of the reading device 1 shown in FIG. 1, and FIG. 2B shows a side cross-sectional view. The reading device 1 incorporates a scanning substrate 10 on which a light source (laser diode), a laser polarization mechanism, a light source and polarization mechanism drive circuit, a reflected light detection circuit from a bar code symbol, and the like are mounted. Further, in the handle portion 2, a decoding board 2 for decoding the signal output from the scanning board 10 and transmitting it to the host computer 6.
5 is incorporated. The trigger 3 is supported by one end 19 of an elastic arm 20 so that it can be moved, and the other end of the elastic arm 20 is fixed to the scanning substrate 10 and a trigger switch 21 provided on the scanning substrate 10 is pressed. Is provided.

The trigger switch 21 is configured as a two-step operation push button switch, and when the button is pushed to the first level, the TRG1 terminal is switched from the off state to the on state. Further, when the button is pushed to the second level, the TRG2 terminal is switched from the off state to the on state. Therefore, when the trigger 3 is pulled and the button is pushed down to the first level, the switch 21
The TRG1 terminal is turned on, and when it is pushed to the second level, the TRG2 terminal is turned on.

Further, the laser diode 11 is incorporated so that the laser light emitting direction is directed toward the center of the scanning / collecting mirror 13. The scanning / condensing mirror 13 is pressed into the shaft of the scanning motor 22 and driven by the scanning motor 22 to swing. Further, the scanning / collecting mirror 13 is
A scanning mirror unit 13a for polarizing and scanning the beam from the laser diode 11 is provided at the center thereof, and a focusing mirror unit 13b for focusing the reflected light from the bar code symbol is provided on the outer periphery of the scanning mirror 13a. There is. When the scanning / focusing mirror 13 swings, laser light is emitted to the outside of the housing along the optical path 18 through the optically transparent window 4, and scans the bar code symbol. Further, the reflected light from the bar code symbol condensed by the condenser mirror 13b passes through the optical path 17 and the photodiode 1
It is incident on 2. The photodiode 12 converts the reflected light into a current, the detection circuit provided on the scanning substrate 10 electrically processes it, and outputs it to the decoding substrate 25.

FIG. 3 shows a block configuration of the control circuit mounted on the scanning substrate 10 described above and will be described. In this configuration, the output signal TRG1 of the trigger switch 21
Are connected to the set (S) terminals of the flip-flops 31 and 32. Further, another output signal TRG2 of the trigger switch 21 is connected to the reset (R) terminal of the flip-flop 31. Further, as the output signal of the decoder 25, the DCD_S signal that is output when the barcode is successfully read is input to the reset (R) terminal of the flip-flop 32.

The output signal AIM from the flip-flop 31 is input to the scanning angle control circuit 33, the motor abnormality detection circuit 34, and the laser power control circuit 35, respectively. The output signal SCAN of the flip-flop 32 is
Scan angle control circuit 33 and laser power control circuit 35
Has been entered in. The scanning angle control circuit 33 supplies a predetermined current to each phase of the scanning motor 22 based on the AIM signal. The motor abnormality detection circuit 34 is configured to determine whether or not an abnormality has occurred based on the AIM signal and the feedback signal Vr from the scanning motor, and output the result as an LDOFF signal to the laser power control circuit 35. When an abnormality occurs by the laser power control circuit 35, the laser power is turned off. Further, the laser power control circuit 35 controls the current supplied to the laser diode to a predetermined value by the AIM and SCAN signals.

Next, FIG. 4 shows an example of a concrete configuration of the control circuit shown in FIG. In the figure, Vcc is about DC5V
Of the power supply, and Vref1 indicates a reference voltage of about 2.5 V generated by a reference voltage circuit (not shown). Vref2 indicates a reference voltage generated by a circuit different from Vref.

In this configuration, the flip-flop 31
And 32 are, for example, TTL74LS74, and U
3, U5 and U6 are differential amplifiers, and U4 is a comparator. The oscillator Y1 is an oscillator that outputs two motor drive signals (AC1 and AC2) when the AIM signal is high (H). The two signals AC1 and AC2 are intermittent triangular waves whose phases are shifted by 180 °. Current Is1 from DC current source
Is supplied to the motor only when the AIM signal is H.

Further, the laser power control circuit 35 feeds back the photocurrent of the power detecting photodiode 11b installed in the same package as the laser diode 11a to the inverting input terminal of the differential amplifier U3, and the differential amplifier U3. U
An APC (auto power control circuit) for controlling the output power proportional to the voltage value of the non-inverting input terminal 3 is configured. Then, the scanning angle control circuit 33 uses the scanning motor 2
A triangular wave is supplied to the AC1 phase and the AC2 phase of No. 2 and a predetermined DC current is supplied to the DC phase to drive the scanning motor 22 so that the scanning mirror 23 swings.

Further, the motor abnormality detection circuit 34 detects the back electromotive force generated in the DC phase, and when the time when this value is less than the threshold value is more than a predetermined value, it is judged that the motor has failed, and the SCAN signal is output. Is configured to be disabled.

Next, the driving method of the scanning motor 22 and the motor abnormality detecting method will be described with reference to FIGS. FIG. 5 shows a schematic configuration of a scanning motor, for example, a two-phase, 18 ° step stepping motor is shown as an example. The AC1 phase coil and the AC2 phase coil are wound around the same core, and the winding directions are opposite to each other. on the other hand,
The DC phase coil is independent of the other phases. Each of the AC1 phase and the AC2 phase has 5 poles, and the DC phase has 10 poles on the stator.

FIG. 6 shows the waveform of the current passed through each phase of the motor shown in FIG. A constant direct current is applied to the DC phase and AC
An intermittent triangular wave as shown in the figure is input to the first phase and the AC2 phase. In addition, the AC1 phase and the AC2 phase have a phase difference of 18
0 ° different. In this motor, each phase is magnetized to the south pole when the current flows in the forward direction.
Therefore, the DC phase is always excited to the S pole.

At time t1, the AC1 phase is excited to the S pole and the AC2 phase is AC1 as shown in FIG. 7A.
Since it is excited in the opposite polarity to the phase, the N pole formed by the permanent magnet on the rotor 41 is attracted to the AC1 phase side, and the rotor 41 rotates to the left.

Next, at t2 in FIG. 6, the AC1 phase,
Since neither of the AC2 phases is excited, the N pole on the rotor 41 is attracted to the DC phase, and the rotor 41 rotates to the right.
As shown in (b). Further, at t3 in FIG. 6, contrary to t1, the AC1 phase is excited to the N pole and the AC2 phase is excited to the S pole. Therefore, the rotor rotates further to the right as compared with time t2, as shown in FIG. 7 (c). Again, at t4 in FIG. 6, since only the DC phase is excited,
The rotor 41 returns to the position shown in FIG.

By repeating such an operation, the rotor 41 repeats right rotation and left rotation, and the mirror 13 pressed into the shaft can be swung. When this driving method is adopted, the rotation of the rotor 41 becomes smoother than the driving by the square wave. In addition, by changing the peak value of the current that flows in the AC1 and AC2 phases, one step angle (18 °) that cannot be realized by ordinary digital (square wave) driving
The scanning angle within the range can be selected in an analog manner (freely from 1 to 18 °).

However, when such a drive system is adopted, a counter electromotive voltage Vr proportional to the amount of rotation of the rotor 41 appears in the DC phase, as shown in FIG. This counter electromotive voltage Vr is
It increases as the rotation angle of the rotor increases. On the contrary, when some failure occurs in the motor 22 and the scanning angle decreases, the counter electromotive voltage Vr decreases like the abnormal waveform shown in FIG. Therefore, when the counter electromotive voltage Vr does not exceed the predetermined value, it is possible to determine that the scanning motor 22 that is the scanning mechanism has failed and stop the laser emission.

The operation of the control circuit shown in FIG. 4 will be described with reference to the timing chart of FIG. First, when the trigger switch 21 is pressed to the first level, the TRG1 signal indicating the setting to the aiming mode is high (H).
To low (L). Then, the flip-flops 31 and 32 set the AIM signal and the SCAN signal.

The transistor Q2 is turned off, and the differential amplifier U
The inverting input terminal of No. 3 is not fixed to a voltage value near Vcc, and has a voltage value determined by the feedback current Ipin from the photodiode in the laser diode package. As a result, the laser power control circuit 35 causes a current to flow through the laser diode 11, and laser light of a predetermined power is emitted from the laser diode. At the same time, the AIM signal turns on the transistor Q4, setting the voltage at the non-inverting input terminal of the differential amplifier U3 to a low voltage value. As a result,
The output power is controlled to a low output of 1 mW.

The set SCAN signal is generated by the oscillator Y1.
At the same time that the oscillating operation and the operation of the current source Is1 are started, the transistors Q7 and Q8 are turned on, and the outputs of the oscillator Y1 are changed to resistors R18, R19, R20 and R2, respectively.
2, divided by R23, R24, AC of the scanning motor 22
A relatively low voltage is applied to the 1 and AC2 phases to start scanning at a small scanning angle (2 to 5 °). At this time, the transistor Q5 is turned on, and the operation of the motor abnormality detection circuit 34 is prohibited.

Next, when the trigger switch 21 is further pushed to the second level, the TRG2 signal for switching to the scan mode is output. Then, the AIM signal is reset, Q3, Q5, Q7, and Q8 are turned off, the laser emission power is about 2 mW, and the scanning angle is 10 to 20.
The motor abnormality detection circuit enters the operation permitting state. Finally, when the decoder completes reading the bar code, it outputs the DCD_S signal, which causes the SC
The AN signal is reset, and the emission of laser light and the scanning operation are completed.

Here, in the scan mode, when the scan angle of the scan motor 22 decreases and the DC phase counter electromotive voltage Vr does not reach a predetermined value (Vref2 shown in FIG. 8),
When the comparator U4 stops discharging the electric charge of C2 and the voltage of C2 becomes equal to or higher than Vbe of the transistor Q6, the transistor Q6 is turned on, the SCAN signal is set to L, and the operation of the laser power control circuit 35 and the oscillator Y1 is stopped. Then, the laser emission and scanning are stopped.

Next, an example in which a bar code is read on a paper surface using the optical reading apparatus of this embodiment will be described. In FIGS. 10A and 10B, first, aiming is performed in an aiming mode in which the scanning angle and the laser emission power are small, and the reading device is aimed at an appropriate bar code symbol. Next, as shown in FIG. 10C, the trigger is pulled further deeper to switch to the scan mode in which the scan angle and the laser emission power are large, and the barcode symbol is read. By repeating the scanning in such a procedure, the barcode symbol can be easily, accurately and safely read.

By the way, in the aiming mode, since the emission power is lowered, it is safe, but the visibility may be slightly lowered. Therefore, as a more preferable embodiment, the wavelength of the light emitted from the laser diode is set to 6
The wavelength can be shortened from 75 nm. At present, some semiconductor manufacturers have announced a semiconductor laser having a wavelength of 660 to 630 nm. For example, a semiconductor laser having a wavelength of 660 nm or shorter, which is shorter than that of a conventional semiconductor laser, and more preferably 633 ± 10 nm is used in this embodiment. By using it as a light source, sufficient visibility can be ensured. Further, although the scanning angle in the aiming mode is set to 2 to 5 ° in the present embodiment, it goes without saying that the same effect can be obtained even when the scanning angle is set to 0 ° in the aiming mode and the beam is stopped.

Further, although the embodiment in which the stepping motor is adopted as the scanning motor and the triangular wave is applied has been described, the normal square wave drive (one-phase / two-phase excitation system etc.) is adopted and the current flowing in each phase is monitored. However, even if it is detected that an abnormal current larger than a predetermined current value flows, the abnormality of the motor can be detected as in this embodiment.

Further, as a scanning means, Japanese Patent Laid-Open No. 5-266
The present invention can also be realized by using a scanning device equipped with an electromagnetic coil, a permanent magnet, a leaf spring, etc. as described in Japanese Patent No. 236. In this scanning device, a permanent magnet is attracted by an electromagnetic coil (driving coil), and the emitted light from a light source is deflected by using the vibration of a leaf spring to perform barcode scanning.

Further, as shown in FIG.
If the detection coil 52 is provided inside or at a place where a change in the magnetic field due to the reciprocating motion of the permanent magnet can be detected, a voltage signal can be generated in the detecting coil 52 by the reciprocating motion of the permanent magnet. In this scanning device, as the scanning angle increases, the speed at which the permanent magnet crosses the detection coil also increases, and the voltage amplitude generated in the detection coil 52 accordingly increases. Therefore, by detecting the voltage generated in the detection coil 52, the control of the scanning angle and the abnormal operation of the deflection unit can be confirmed.

In FIG. 11, R37 is a scanning angle control trimmer. If the scanning angle control circuit portion shown in FIG. 4 is changed to the circuit shown in FIG. 11, it will be easily understood that the present invention can be realized with this scanning device. Further, in the present embodiment, the case where the permanent magnet is attracted to the drive coil has been described, but it goes without saying that the invention can be realized even when the attraction and the repulsion are alternately repeated or when the repulsion is performed.

As described above, according to the optical reading apparatus of the present embodiment, in the aiming mode narrower than the normal scanning angle, the emission power of the laser light is reduced to a safe level and the scanning mechanism abnormality detection function is provided. In the non-operating state, in the normal scanning mode (scan mode), raise the emission power of the laser light to the desired level,
In addition, since the scanning mechanism abnormality detection function is operated, it is easy to aim the bar code and a safe scanning device can be obtained.

Further, an additional aiming light source (LED
Etc.) is not used, power consumption can be suppressed. Further, in the aiming mode, since the emission power of the laser diode is kept low, it can be expected that the life of the laser diode is extended.

Although described based on the above-described embodiments, the present invention also includes the following inventions. (1) In a scanning device for detecting a symbol patterned by bars and spaces having different reflectances and optically reading information from the symbol, a light source formed of a semiconductor laser and a power control means for controlling the emission power of the light source. A polarization scanning unit that polarizes the light emitted from the light source at a predetermined angle and scans a bar code; a polarization scanning amount control unit that controls the polarization amount by the polarization unit; and an abnormal operation of the polarization unit is monitored. An abnormal laser stop means for stopping the laser emission power when detecting an abnormal operation, a prohibition means for prohibiting the operation of the abnormal laser stop means, and a plurality of scanning modes in which various emission powers and polarization amounts are combined. Is set,
And a scanning mode selection means for selecting a desired scanning mode, and a desired patterned symbol is captured by the emitted light of the first scanning mode set to a smaller polarization amount and a lower emission power than during reading. After that, the symbol is read in the second scanning mode in which a predetermined level of emission power for reading and a predetermined amount of polarization are set, an abnormality of the polarization scanning means is detected, and the operation of the laser stop means at the time of abnormality is detected. An optical reading device characterized by determining permission / prohibition.

(2) In the first scanning mode,
The optical reading device according to the item (1), wherein the emission power of the light source is 1 mW or less. (3) In the first scanning mode, the prohibiting means is in an operating state to prohibit the operation of the abnormal laser stopping means, and in the second scanning mode, the prohibiting means is in a non-operating state to cause the abnormal condition. The optical reading device according to the item (1), wherein the operation of the laser stop means is permitted.

[0042]

As described in detail above, according to the present invention, it is possible to provide an optical reading device which can be easily aimed at a desired bar code, which is improved in safety and which is highly reliable.

[Brief description of drawings]

FIG. 1 is a diagram showing an external configuration of an optical reading device as an embodiment according to the present invention.

2 (a) is a diagram showing a top cross-section of the reading device shown in FIG. 1, and FIG. 2 (b) is a diagram showing a side cross-section thereof.

3 is a block diagram showing a configuration of a control circuit mounted on the scanning substrate shown in FIG. 2 (a).

FIG. 4 is a diagram showing a specific configuration example of the control circuit shown in FIG.

5 is a diagram showing a schematic configuration of the scanning motor shown in FIG.

FIG. 6 is a diagram showing a waveform of a current passed through each phase of the motor shown in FIG.

FIG. 7 is a diagram showing a relationship between magnetic poles of a rotor and a coil in a motor.

FIG. 8 is a diagram showing a relationship between a counter electromotive voltage Vr proportional to a rotation amount of a rotor and an abnormal waveform.

9 is a timing chart showing the operation of the control circuit shown in FIG.

FIG. 10 is a diagram showing an example of reading a barcode on a paper surface by applying the present embodiment.

FIG. 11 is a diagram showing a modification of the scanning angle control circuit portion in the present embodiment.

[Explanation of symbols]

1 ... Reading device, 2 ... Handle part, 3 ... Trigger, 4 ...
Window, 5 ... Beam emitting part, 6 ... Cable, 7 ... Host computer, 10 ... Scanning substrate, 11 ... Laser diode, 12 ... Photodiode, 13 ... Scanning / focusing mirror, 13a ... Scanning mirror part, 13b ... Focusing Mirror part,
16, 17, 18 ... Optical path, 20 ... Elastic arm, 21 ... Trigger switch, 22 ... Scan motor, 25 ... Decode board.

Claims (3)

(57) [Claims] 1. An optical reading device for optically reading information from a symbol patterned by bars and spaces having different reflectances, a light source formed of a semiconductor laser, and a power control means for controlling the emission power of the light source. A polarization scanning unit that polarizes the light emitted from the light source at a predetermined angle and scans the symbol, a polarization scanning amount control unit that controls the polarization amount by the polarization unit, and an abnormal operation of the polarization unit. Abnormal laser stop means for monitoring and stopping the laser emission power when detecting abnormal operation, prohibiting means for prohibiting the operation of the abnormal laser stop means, and a plurality of scans combining various emission powers and polarization amounts A scanning mode selecting means for setting a mode and selecting a desired scanning mode, based on the scanning mode selected by the mode selecting means. The light source of the emission power, polarized light quantity of light emitted from the light source, an optical reader and determines the operation enabling and disabling of the abnormality detecting means. 2. The optical reader according to claim 1, wherein the wavelength of the laser beam generated by the semiconductor laser is 660 nm or less. 3. At least the scanning mode setting is such that the polarization amount is smaller than when the symbol is read, only a part of the symbol is scanned, and the emission power of the light source is set lower than when the symbol is read. The first scanning mode described above and the second scanning mode in which a predetermined emission power for reading the symbol is set with the polarization amount that scans the entire symbol are set. Item 1. The optical reader according to Item 1.