JP2849326B2 - Barcode 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 bar code reader for preventing a reading performance from being deteriorated by disturbance light in a laser scan type bar code reader.

[0002]

2. Description of the Related Art As the use range of a bar code reader is expanded, the reading performance is deteriorated due to the use environment conditions, and a bar code reader which can cope with a severe use environment is required. If the barcode reader is used in the vicinity of the lighting equipment, the emission spectrum of white light such as a fluorescent lamp and the emission spectrum of the visible light semiconductor laser used in the barcode reader overlap, so that the It is difficult to completely remove disturbance light using an optical filter.

FIG. 5 is a block diagram showing the configuration of a bar code reader according to the prior art, and a visible light semiconductor laser 101 as a light source of a laser scan type bar code reader.
Irradiates a bar code label 103 via a polygon mirror 102, and the reflected light is input to an optical filter 105 via a condenser lens 104 together with disturbance light such as a fluorescent lamp. The semiconductor laser light component from which the disturbance light component determined by the characteristics of the optical filter 105 has been removed is input to the optical sensor 106 and photoelectrically converted.
After being amplified in the light receiving circuit 107, it is input to the CPU 109 via the signal processing circuit 108, and the information displayed by the bar code label is decoded.

[0004]

FIG. 4 shows the relationship between the wavelength and the relative power between the emission spectrum of the fluorescent lamp of the inverter lighting system and the emission spectrum of the semiconductor laser, as shown in FIG. The emission spectrum (wavelength 670 nm) overlaps. The optical filter 105 constituting the bar code reader according to the prior art is a band-pass filter, which transmits the disturbance light in the emission spectrum of the semiconductor laser and the vicinity thereof together, so that only the disturbance light can be removed. In principle, it was impossible, and only the effect of disturbance light was reduced. For this reason, the lighting waveform from the lighting fixture appears in the barcode signal as low-frequency noise, and when the signal is amplified, the signal is saturated and the barcode signal may disappear. SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-described defect of the bar code reader according to the related art, and is provided with a low-frequency noise removing circuit that electrically removes disturbance light components that cannot be completely removed by an optical filter. And a bar code reader.

[0005]

In order to achieve the above-mentioned object, a bar code reader according to the present invention uses a light reflected from a bar code label surface irradiated by a light source 1 provided on the bar code reader and a bar code peripheral portion. The incident disturbance light is input to the light receiving element 6 via the optical filter 4 and the condenser lens 5, and the light receiving element 6 outputs the output signal composed of the reflected light component from the bar code label surface and the disturbance light component that has been photoelectrically converted. Amplifier 7, peak detection circuit, bottom detection circuit,
The low-frequency noise included in the bar code signal is removed by passing through a low-frequency noise removing circuit 8 including an adder circuit, an inverting amplifier circuit, and a differential amplifier circuit. It is configured to detect barcode information via the decoder 11.

[0006]

[Function] Bar code signal V _{1 including} low frequency noise component
Was input to the peak detection circuit and bottom detection circuit forming a low-frequency noise removing circuit detects a peak detection signal V ₂ and the bottom detection signal V ₃ to form the envelope of a bar code signal V _1. Furthermore, we obtain the amplitude center V ₄ of the peak detection signal V ₂ and the bottom detection signal V ₃ in the adder circuit, low-frequency noise is removed and determine the difference between the two signals V ₁ and V ₄ in the differential amplifier circuit Bar code signal V
₅ is obtained.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a barcode reader according to the present invention. In FIG. 1, a semiconductor laser beam from a visible light semiconductor laser 1, which is a light source of a laser scan type bar code reader, irradiates a bar code label 3 via a polygon mirror 2, and reflected light from the bar code label 3 The light is input to the light receiving element 6 via the optical filter 4 and the condenser lens 5 and photoelectrically converted together with disturbance light from an illumination device or the like provided near the bar code reader. Since the optical filter 4 is a bandpass filter, the optical filter 4 removes disturbance light except for the vicinity of the bar code signal, but passes the bar code signal and the disturbance light component in the vicinity thereof as they are to the light receiving element 6 via the condenser lens 5. input. Therefore, the optical filter 4 can reduce the influence of the disturbance light but cannot completely remove the influence of the disturbance light. Therefore, the disturbance signal is included in the output signal from the light receiving element 6 as low-frequency noise. ing. The electric signal output from the light receiving element 6 is voltage-amplified by the amplifier 7, the low-frequency noise elimination circuit 8 removes low-frequency noise due to disturbance light components, and the voltage is amplified by the amplifier 9. The output signal of the amplifier 9 is binarized by a binarization processing circuit 10 and decoded by a decoder 11 as barcode information indicated by a barcode label 3.

FIG. 2 is a block diagram showing a configuration of a low frequency noise elimination circuit according to the present invention. In FIG. 2, a bar code signal V ₁ containing a disturbance light component is input to a peak detection circuit 21 via a diode 31 and is input to a bottom detection circuit 22 via a diode 32 having a polarity opposite to that of the diode 31. The peak detection circuit 21 includes an operational amplifier 33 having a grounded resistor 41 and a capacitor 43 connected to a positive input terminal, and the bottom detection circuit 22 has an operational amplifier 34 having a grounded resistor 42 and a capacitor 44 connected to a positive input terminal. It is constituted by. Detection signal V ₂ and the detection signal V ₃ of the bottom detection circuit 22 of the peak detector circuit 21 is a low-frequency noise envelope components barcode signal V ₁ that contains FIGS. 3 (a)
As shown in FIG. The detection signals V ₂ and V ₃ are input to the minus input terminal of the operational amplifier 33 forming the addition circuit 23 via the resistors 45 and 46, respectively, and added, and the average of the amplitudes of the _two detection signals V ₂ and V ₃ is obtained. Find the value. Further, the detection signal of the addition circuit 23 is input via a negative input terminal to the resistor 48 of the operational amplifier 36 constituting the inverting amplifier circuit 24, outputs a signal V ₄ the polarity of the signal is inverted. The waveforms of the signals V ₁ , V ₂ , V ₃ and V ₄ are shown in FIG.
This is as shown in FIG. Bar code signal V ₁ and the signal V ₄ which includes a low-frequency noise through a resistor 50 and 51 is inputted to the minus side and the plus-side input terminal of the operational amplifier 37 constituting the differential amplifier circuit 25, the output of the operational amplifier 37 and it outputs a signal V ₅ which is the difference between the signals V ₁ and V ₄ from the terminal. That is, the low-frequency noise components included in the signals V ₁ and V ₄ are canceled by the differential amplifier circuit 25 to form a bar code signal V ₅ from which the low-frequency noise components have been removed.
This is as shown in FIG.

[0009]

As described above, the bar code reader according to the present invention photoelectrically converts the reflected light component and the disturbance light component from the bar code label surface input to the light receiving element via the optical filter and the condenser lens. The voltage of the converted and photoelectrically converted electric signal is amplified by an amplifier, and then input to a low-frequency noise removing circuit to remove a low-frequency noise component.
After the voltage is amplified by the amplifier, the barcode information is detected by the decoder via the binarization processing circuit. Therefore, in the barcode reader according to the present invention, since a low-frequency noise component can be removed without using a high-pass filter, a stable barcode signal can be obtained without deteriorating the low-frequency characteristics of the barcode signal,
Barcode reading characteristics can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of a bar code reader showing an embodiment according to the present invention.

FIG. 2 is a block diagram of a low-frequency noise removing circuit according to the present invention.

FIG. 3 is a waveform diagram.

FIG. 4 is an emission spectrum distribution diagram of a fluorescent lamp and a semiconductor laser.

FIG. 5 is a block diagram showing a configuration of a conventional barcode reader.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Visible light semiconductor laser 2 Polygon mirror 3 Bar code label 4 Optical filter 5 Condensing lens 6 Light receiving element 7, 9 Amplifier 8 Low frequency noise removal circuit 10 Binarization processing circuit 11 Decoder

Claims (2)

(57) [Claims] An optical filter (4) and a condensing lens (5) reflect reflected light from a barcode label surface irradiated by a light source (1) provided on a barcode reader and disturbance light incident from a peripheral portion of the barcode reader. ) To the light receiving element (6), and an output signal composed of the reflected light component from the bar code label surface and the disturbance light component that has been photoelectrically converted by the light receiving element (6) is voltage-amplified by the amplifier (7). Input to the low-frequency noise elimination circuit (8). The low-frequency noise elimination circuit (8) removes the low-frequency noise component contained in the bar code signal.
A bar code reader, comprising: amplifying a voltage in an amplifier (9); and detecting bar code information in a decoder (11) via a binarization processing circuit (10). And detecting a peak detection signal and a bottom detection signal that form an envelope of the bar code signal from the bar code signal containing the disturbance light component, and generating a signal obtained by averaging the amplitudes of the two detection signals. The bar code reader according to claim 1, wherein a low frequency noise component included in the bar code signal is removed by detecting a difference from the bar code signal.