JP2836297B2 - Optical information reader - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of scanning a light such as a laser beam, irradiating an object on which optical information such as a bar code is described, and converting the reflected light into an electric signal. The present invention relates to an optical information reader for reading information.

[0002]

2. Description of the Related Art Conventionally, in a device for reading optical information such as a bar code, for example, as disclosed in Japanese Patent Application Laid-Open No. 56-140467, a laser beam is scanned and optical information such as a bar code is read. The printed object is irradiated, and optical information is read from the reflected light.

[0003] For example, a conventional bar code reader is shown in FIG.
As shown in FIG. 2, a laser beam from a laser light source 51 is converted into a parallel light beam by a collimating lens 53, and then emitted to a mirror 57 which is reciprocated in a direction indicated by an arrow in FIG. , Code 39, barcode label 59 on which barcodes of various standards such as ITF are printed, and the reflected light reflected from barcode label 59 by this scanning is transmitted through condensing lens 61 to receive light quantity. An optical system configured to guide the electric signal to the photodetector 63 that generates an electric signal corresponding to the optical signal; an amplifier circuit 71 that amplifies a weak electric signal output from the photodetector 63; A binarization circuit 73 for binarizing an electric signal;
A counter unit 75 that determines the narrow bar and wide bar of the bar code by counting the width of the digitized signal, and a bar code is decoded (decoded) based on an output signal from the counter unit 75 and the decoding result is output to the outside. A signal processing system including a decoding section 79 for performing the operation, a mirror driving circuit 81 for driving the step motor 55, and the laser light source 5
A driving system including a laser driving circuit 83 for driving
Laser light is emitted from the laser light source 51 via the laser drive circuit 83, and the stepper motor 55 is driven via the mirror drive circuit 81, whereby the mirror 57 is reciprocated at a predetermined cycle (about 50 Hz), and And a control system including a control unit 84 that operates the decoding unit 79 in synchronization with the operation. Generally, the counter unit 75, the decoding unit 79, and the control unit 84
It is realized as one process of an electronic control unit (ECU) composed of a microcomputer mainly including U, ROM, RAM and the like.

[0004]

However, in such a conventional bar code reader, the bar code label 5 is used.
9 is irradiated with light and the bar code is read by the reflected light, so that not only the reflected light from the bar code label 59 but also the light around the bar code label 59 is incident on the photodetector 63. This light is disturbed, and the SN ratio (signal-to-noise ratio) of the received light signal is reduced, and an error may occur in the binarization result of the received light signal and, consequently, the decoding result of the bar code.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and in an apparatus for reading optical information such as a bar code by irradiating light as described above, the influence of disturbance is reduced and the reading accuracy of optical information is reduced. The aim is to improve.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a light source for projecting light, and a screw.
High-speed scanning means for scanning the light from the light source at a predetermined cycle by the vibration of the resonator, and receiving reflected light reflected from an object on which optical information is written by scanning of light by the high-speed scanning means. An optical information reading apparatus comprising: a light receiving means for generating an electric signal corresponding to the amount of received light; and a reading means for reading the optical information by the electric signal from the light receiving means. the electrical signal path to at delay amount said scanning means corresponding to the period for performing optical scanning in a predetermined direction, and an analog delay line for delaying the electric signals from said light receiving means in an analog manner, 該A
An addition unit that adds the electric signal delayed by the analog delay line and the electric signal output from the light receiving unit,
The gist of the present invention is an optical information reading apparatus including a synchronous adding means for outputting an electric signal corresponding to the addition result by the adding means to the reading means.

[0007]

In the optical information reading apparatus of the present invention configured as described above, the scanning means scans the light from the light source, and the light receiving means scans the object on which the optical information is written by the scanning of the light. It receives reflected light reflected from an object and generates an electric signal corresponding to the amount of received light. Then, the electric signal from the light receiving means is converted into an analog signal by the synchronous addition means.
The analog delay (in other words, the state of the analog signal) with the delay amount corresponding to the cycle of the optical scanning in the predetermined direction by the delay line
) , Is added to the delayed electric signal by the adding means, and then input to the reading means.

That is, in the optical information reading apparatus of the present invention, the electric signal output from the light receiving means is converted into an analog signal.
Synchronous addition using synchronous addition means consisting of extension lines and addition means
As a result, the noise component included in the electric signal is reduced, and the electric signal after the noise component reduction is input to the reading unit. In the present invention, the synchronous addition means is
The analog delay line and the adding means
As a scanning means for inspection, a conventional apparatus shown in FIG. 3 is used.
The mirror for light scanning is rotated by a step motor
Instead of using motor-driven scanning means
High-speed scanning hand that can perform optical scanning at high speed by vibrating resonator
This is because a step is used. In other words, reading optical information
When high-speed scanning means having a torsional resonator is used,
Optical information can be read at high speed.
Since the time per scan is extremely short, for example, synchronous
If the addition is performed by digital arithmetic processing,
Calculation process for the change in the electrical signal per scan
Unable to follow, unable to perform synchronous addition satisfactorily
Become. Therefore, in the present invention, the synchronous addition means is provided with an analog delay.
And an electric signal from the light receiving means.
To enable synchronous addition in the state of analog signals
Therefore, even if the period of the electric signal from the light receiving means is short,
Synchronous addition can be performed at high speed by following signal changes.
I am trying to do it.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 is a schematic configuration diagram illustrating a configuration of an entire barcode reader according to an embodiment to which the present invention is applied.

As shown in FIG. 1, an optical system of a bar code reader according to the present embodiment includes a laser light source 2 for generating laser light,
A collimating lens 4 for converting the laser beam from the laser light source 2 into a parallel light beam; 8, a photodetector 10 as light receiving means for generating an electric signal according to the amount of incident light, and a condensing lens for condensing laser light (scattered light) reflected from the barcode label 6 on the photodetector 10 12.

The laser light source 2 is composed of a light emitting element such as a laser diode, a He-Ne laser, a focusing lens formed of a plano-convex lens, and an aperture stop. 20 is projected at the center position. The photodetector 10 includes a light receiving element including a photodiode, a phototransistor, and the like, and a laser light source 2.
(The wavelength is 670 nm when the light emitting element is a laser diode, and the light emitting element is He-Ne)
And an optical filter that transmits only light having a wavelength of 630 nm in the case of a laser.

Next, the quartz optical scanner 8 uses a mirror unit 20 and
A torsion resonator 28 is integrally formed with a coil portion 22 having a coil (not shown) formed therein, a torsion bar portion 24, and a fixing portion 26 fixed in a housing (not shown). The mirror portion 20 is formed of an Au thin film. By coating with a laser beam, a reflectance of about 90% can be obtained at the wavelength of the laser beam used.

The magnets 29a and 29 for applying a magnetic field in a predetermined direction to the coil portion 22 of the torsional resonator 28 to cause the torsional resonator 28 to torsionally oscillate.
b is provided. The magnets 29a and 29b are positioned and fixed in a housing (not shown), like the torsional resonator 28.

In the quartz optical scanner 8 configured as described above, a magnetic force is generated by applying a current to the coil formed in the coil portion 22 of the torsional resonator 28, and the magnet 2
Under the influence of the magnetic fields from 9a and 29b, the torsional vibration occurs. The mirror section 20 of the torsional resonator 28 reciprocates at a high speed (for example, 800 Hz) due to the torsional vibration, and scans the laser light from the laser light source 2.

For details of such a torsional resonator, see “Quartz Light Scanner for Laser Printer” Sugiyama et al., Proceedings of the 28th SICE Academic Lecture Meeting, pp.581-582.
Page, (1989)}, further description is omitted. Next, the signal processing system of the bar code reader according to the present embodiment includes, as in the conventional apparatus shown in FIG. A synchronous addition unit, which is a main part of the present invention, which performs synchronous addition of the electric signal amplified by the amplifier circuit 31 and outputs the synchronous addition result to the binarization circuit 33. A circuit 40 is provided. The drive system includes a torsional resonator drive circuit 41 that self-resonates the torsional resonator 28 by energizing the coil of the torsional resonator 28, and a laser drive circuit 43 that drives the laser light source 2. , Torsional resonator drive circuit 41, laser drive circuit 4
3 and a control unit 44 that controls the operation of the decoding unit 39 and is implemented as one process of the ECU.

Here, in order to cause the torsional resonator 28 to self-resonate, the coil of the torsional resonator 28 is
What is necessary is just to add an oscillation waveform signal corresponding to the resonance frequency of
The torsional resonator drive circuit 41 drives the torsional resonator 28 by passing this signal through the coil of the torsional resonator 28. A laser driving circuit 4 for driving the laser light source 2;
Reference numeral 3 performs power control, temperature control, and the like in order to output a stable laser beam from the laser light source 2. The torsional resonator 28 may be driven by self-resonance,
There is a method of controlling the current flowing through the coil of the torsional resonator 28 to cause torsional vibration at a desired frequency.

On the other hand, the binarization circuit 33 uses a comparator having a hysteresis characteristic, and converts the electric signal input from the synchronous addition circuit 40 into a binary signal by a floating binarization method or a differential binarization method. Become Therefore, the binarization circuit 33
As the electric signal input to the circuit has a smaller noise component, the hysteresis characteristic of the comparator can be made gentler, and a more reliable binarization characteristic can be obtained.

Next, the synchronous addition circuit 40 applies the electric signal from the amplifier circuit 31 to the torsional resonator 28 where the torsional resonator 28 undergoes torsional vibration.
An analog delay line 46 composed of a glass ultrasonic delay line, a SAW (surface acoustic wave) delay line, or the like for delaying by a period, and an electric signal delayed by one period of the torsional resonator 28 by the analog delay line 46. An adder 47 for adding the electric signal from the amplifying circuit 31 and an attenuator 48 for attenuating the electric signal output from the adder 47 to half the size;
It is composed of

In the bar code reader of the present embodiment configured as described above, the laser light from the laser light source 2 is projected on the mirror section 20 of the torsional resonator 28, and is scanned on the bar code label 6 at high speed. You. Then, the reflected light from the barcode label 6 is condensed by the condenser lens 12 and then enters the photodetector 10. Then, the photodetector 10
An electric signal corresponding to the amount of incident light is generated. The electric signal is amplified by the amplifier circuit 31, synchronously added by the synchronous addition circuit 40, and then input to the binarization circuit 33.

The synchronous addition circuit 40 includes an analog delay line 46
The electric signal delayed by one cycle of the torsional resonator 28 and the electric signal from the amplifier circuit 31 by the adder 47
And attenuate it to half the size of 1
Since the signal is output to the binarization circuit 33, the SN ratio of the electric signal input to the binarization circuit 33 is improved by 3 dB compared to the case where the electric signal from the amplifier circuit 31 is directly input to the binarization circuit 33. You.

That is, a signal containing a noise component (S
When (i + Nj) is added, the signal has the same characteristic, and the noise component has no correlation with the signal, and the signal obtained by optical scanning one cycle before is (Si-1 + Nj-1).
, The added signal W is

[0022]

(Equation 1)

## EQU1 ## Therefore, the S / N ratio of this signal (S /
N)

[0024]

(Equation 2)

This is improved by 3 dB. Where S
i, Si-1 are signals obtained by optical scanning, and Si-1 is Si
Is a signal by optical scanning one cycle before, and is equal to Si. Nj and Nj-1 are noise signals generated by disturbance during optical scanning, and Nj-1 is a noise signal generated during optical scanning one cycle before Si and is different from Nj. Thus, according to the bar code reader of the present embodiment, the S / N ratio of the electric signal from the amplifier circuit 31 is improved by 3 dB and the binarization circuit 3
It can be seen that 3 can be input.

As described above, according to the bar code reader of this embodiment, the synchronous addition circuit 40 can improve the S / N ratio of the electric signal from the amplification circuit 31 and input the electric signal to the binarization circuit 33. , It is possible to reduce the reading error of the bar code. In addition, since the influence of the disturbance light can be reduced in this manner, the device can be used even in a relatively bright place with respect to the conventional device, and the use conditions can be expanded.

In this embodiment, since the electric signal from the amplifier circuit 31 is synchronously added, in order to obtain a reading speed similar to that of the conventional bar code reader, the optical signal is amplified at a magnification not less than the number of times of performing the synchronous addition. Although it is necessary to perform scanning, in this embodiment, a quartz light scanner is used as the optical scanning device, so that the optical scanning is 10 times or more as compared with the conventional device in which the mirror is rotated by the step motor. Speed, so that the reading speed does not decrease.

In the above embodiment, the amplifier circuits 31 and 2
Although one synchronous adding circuit 40 is provided between the value adding circuit 33 and the synchronous adding circuit 40, the synchronous adding circuit 40 may be connected in cascade as shown in FIG. In this case, since an improvement effect of the SN ratio of about 3 dB can be obtained by one synchronous addition circuit 40, if the number of connection stages of the synchronous addition circuit 40 is M, an improvement effect of M × 3 dB can be obtained.

When the synchronous addition circuits 40 are cascaded in this manner, delay lines, adders, and attenuators corresponding to the number of connection stages are required, and the scale, power consumption, and
This causes an increase in signal delay time and the like. Therefore, for example, FIG.
As shown in (5), if the synchronous adder circuit 40 is configured such that the adder 47 and the attenuator 48 are connected in series, and the output of the attenuator 48 is fed back to the adder 48 via the analog delay line 46, A delay line, an adder,
The effect of improving the SN ratio can be improved without increasing the number of attenuators. That is, if the synchronous addition circuit 40 is configured as shown in FIG. 3B, the number of times of passing through the field back loop including the analog delay line 46 corresponds to the number of connection stages of the synchronous addition circuit 40 shown in FIG. Therefore, the synchronous addition circuit 40
The effect of improving the S / N ratio can be improved without increasing the scale.

In this case, an attenuator for attenuating the input signal by half may be used as the attenuator 48 as in the above embodiment. When a feedback loop is configured in this manner, optical scanning is performed at a scanning speed (about 8
(100 Hz to 1600 Hz), and the quartz light scanner 8 used in the above embodiment can sufficiently cope with this.

Next, in the above-described embodiment, the quartz light scanner 8 having the torsional resonator 28 is used for optical scanning, and the laser light reciprocates on the bar code label 6, so that the analog delay The electric signal from the amplifier circuit 31 is delayed by the time required for the reciprocating scanning by setting the amount of delay of the line 46 to one cycle of the torsional vibration of the torsional resonator 28, but optical scanning in only one direction is repeated . Place
In this case , the electric signal from the amplifier circuit 31 may be delayed by the scanning time in one direction.

In the above embodiment, the bar code reader for scanning a light and reading a bar code from the reflected light has been described. However, the present invention is not limited to such a bar code reader, and reads characters and figures, for example. OCR (Op
A device that scans light and reads optical information from the reflected light, such as a tical character reader, can be applied.

[0033]

As described above, according to the optical information reading apparatus of the present invention, the electric signal output from the light receiving means is synchronously added by the analog delay line and the adding means.
After the synchronous addition is performed by using, the signal is input to the reading unit. Therefore, it is possible to improve the SN ratio of the electric signal input to the reading unit and reduce the reading error of the optical information. Further, since the influence of disturbance light can be reduced, it is also possible to expand the use conditions of the reading device. In the present invention, the scanning means
Optical scanning at high speed using the vibration of a torsional resonator
Because high-speed scanning means that uses
The period of the input electric signal is much shorter than that of the conventional device.
However, the synchronous addition means is replaced by an analog delay line and an addition means.
The synchronous addition of electrical signals is analyzed by
Since it is performed in a log form, the synchronous addition means side
Can satisfactorily perform synchronous addition of electric signals. Therefore,
According to the present invention, the noise reduction effect of the synchronous addition means can be reduced.
Reads optical information at high speed
Can be.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a configuration of a barcode reading device according to an embodiment.

FIG. 2 is an explanatory diagram illustrating another configuration example of the synchronous addition circuit.

FIG. 3 is a schematic configuration diagram illustrating a configuration of a conventional barcode reading device.

[Explanation of symbols]

2 laser light source 4 collimating lens 6
... Barcode label 8 ... Crystal light scanner 10 ... Photodetector 12 ... Condenser lens 28 ... Torsion resonator 29a, 29b ... Magnet 31
... Amplifier circuit 33 ... Binarization circuit 35 ... Counter section 39 ... Decoding section 40 ... Synchronous addition circuit 41 ... Resonator drive circuit 43
... Laser drive circuit 44 ... Control unit 46 ... Analog delay line 47 ... Adder 48 ... Attenuator

Claims (1)

(57) [Claims] 1. A light source for projecting light and a vibration of a torsional resonator.
High-speed scanning that scans light from the light source at predetermined intervals by movement
Means for receiving reflected light reflected from an object on which optical information is written by scanning light with the high-speed scanning means, and generating an electric signal corresponding to the amount of received light; and the light receiving means A reading unit for reading the optical information by an electric signal from the optical device, wherein a period in which the scanning unit performs optical scanning in a predetermined direction on an electric signal path from the light receiving unit to the reading unit. The electric signal from the light receiving means is converted into an analog signal with a delay amount corresponding to
An analog delay line for delaying the, and an adding means for adding the electric signal outputted from the electric signal and the light-receiving means which is delayed by the analog delay line, an electric signal corresponding to the addition result by the adding means An optical information reading device, further comprising a synchronous adding means for outputting a signal to the reading means.