JP2745945B2 - Barcode detection device - 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 detecting device used in POS, distribution management, production management and the like.

[0002]

2. Description of the Related Art When reading bar code information expressed in black and white by an optical sensor, an analog signal obtained by scanning a bar code with a light spot and converting the bar code into an electric signal includes: Electric signals other than the bar code information may be mixed due to the influence of optical non-uniformity, stains and deposits on the bar code surface, and various types of information for identifying only the bar code information may be mixed. Attempts have been made. Generally, an analog signal is amplified, subjected to appropriate preprocessing, and then binarized by a binarization circuit.
Value conversion is performed. There are many types of such binarization circuits including a pre-processing portion according to the application field. Therefore, the pre-processing circuit and the binarization circuit are selected in consideration of the advantages and disadvantages and the use conditions of the binarization circuit to ensure reliability.

A typical example of a conventional binarizing circuit is shown in FIG.
And an envelope binarization circuit shown in FIG.

In the case of the floating binarizing circuit shown in FIG. 3, when two diodes D1 and D2 having the same characteristics in FIG. 3 are used, the terminal voltage of the capacitor C1 is changed from the peak of the analog signal A to the diode. Since the voltage is lower by the voltage drop (about 0.6 V) or higher than the valley of the analog signal A by the voltage drop of the diode, this voltage value is set as the threshold value G and the analog input signal A Binarized and output C
Have gained. As a result, when the floating binarization circuit shown in FIG. 3 operates with an input having an appropriate amplitude, the voltage waveform shown in FIG. 4A appears in each part of the floating binarization circuit. FIG.
In (a), 3 at the top indicates a bar code.
Indicates dirt attached to the white background of the barcode.
A indicates an analog input signal, G indicates a threshold value, and C indicates an output of the floating binarization circuit. A correct binarized output C for the analog input signal A is obtained.

On the other hand, in the case of the envelope binarization circuit shown in FIG. 5, the capacitor C2 in FIG. 5 is connected to the positive peak corresponding to the black level of the analog input signal A (input level corresponding to the black portion of the bar code). And the positive envelope signal H is formed, and the capacitor C3
Holds the voltage of the negative bottom value corresponding to the white level of the analog signal A (the input level corresponding to the white portion of the bar code) to form the negative envelope signal I. The intermediate value obtained by synthesizing the envelope signals was set as the threshold value J. The envelope binarization circuit electrically measures the peak height and the valley depth of the analog input signal A based on the threshold value J, and outputs a binary signal D. That is, when the envelope binarization circuit shown in FIG. 5 operates, a voltage waveform as shown in FIG. 6 appears in each section of the envelope binarization circuit.

In FIG. 6, the uppermost numeral 3 is a bar code, and the numeral 3a is dirt attached to a white background portion of the bar code 3. A is an analog input signal, H is a positive envelope signal corresponding to the analog signal A, I is a negative envelope signal corresponding to the analog signal A, and J is an intermediate value obtained by combining the positive and negative envelope signals. The threshold, D
Indicates the output of the envelope binarization circuit.

[0007]

However, in the above-mentioned floating binarization circuit, when the amplitude of the analog input signal A becomes excessive as shown in FIG. For example, when binarizing an analog signal A having noise Aa due to specular reflection as shown in FIG. 4B, the difference between the white level and the black level of the bar code is large and the amplitude of the threshold value also increases. However, the intersection of the analog input signal A and the threshold value fluctuates due to the influence of noise Aa due to specular reflection, which may cause a bar code bar width to be erroneously read. That is, in FIG. 4B, the binary output C
Is abnormal in the width of the third pulse C3. In addition, the variation of the waveform of the analog signal A due to dirt 3a or stain on a white background portion of the bar code increases, crosses the threshold value, and
The third pulse C3 of the binarized output C in FIG.
And the pulse generated between the fourth pulse C4 and
Dirt 3a and stains on the white background of the bar code are also bar code.
There is a problem that erroneous reading, such as reading as a code, occurs.

In the case of an envelope binarization circuit,
The state before reading the bar code, that is, the starter
In the range of the gin, the difference between the positive envelope H and the negative envelope I is small, and the threshold value and the analog signal A
Are close to each other, and as shown in FIG.
Before the detection of the code, there is a risk that the noise Aa crosses the threshold value J and the noise Aa is erroneously read as a barcode. Also, in FIG. 6, as in the peak Ac of the analog signal A corresponding to the white background following the first bar, the peaks do not reach the threshold G, and the pulses D1 and D2, which should be originally two pulses, are 1 There was a problem that the first bar was erroneously read as it was output as one pulse.

The present invention solves these various problems of the prior art, and eliminates erroneous reading even in the initial stage of bar code reading and reduces noise that is not affected by the amplitude of an analog signal. It is an object of the present invention to provide a bar code detector which is strong and has high read reliability.

[0010]

In order to achieve the above object, a bar code detecting apparatus according to the present invention comprises a plurality of different types of binarizing circuits, for example, a floating binarizing circuit. An envelope detecting circuit for detecting the amplitude of an analog input signal is provided by using an envelope binarizing circuit in parallel. When the output value of the amplitude detecting circuit is less than a predetermined voltage, the output value of the floating binarizing circuit is provided. And a selection circuit for selecting the output value of the envelope binarization circuit when the output value of the amplitude detection circuit is equal to or higher than a predetermined voltage is provided in the bar code detection device.

[0011]

According to the above configuration, an amplitude detection circuit and a selection circuit are added to two types of binarization circuits, that is, a floating binarization circuit and an envelope binarization circuit. In the step, the threshold value is set to a voltage value that is lower than the peak value by a certain value for the peak of the waveform of the analog signal, and the peak is applied to the valley of the waveform of the analog input signal. Since the threshold value is a voltage value that is higher by a certain value than the value, the problem that the first bar is erroneously read between the peaks and valleys of the analog input signal and the first bar is erroneously read can be eliminated. Also, in the range of the start margin, the threshold value is a voltage value lower than the analog signal by a fixed value, so that the distortion portion of the analog signal due to the mixed noise does not cross the threshold value, and Is not erroneously read as a barcode.

Next, after the amplitude of the analog signal reaches the reference voltage, the envelope binarization circuit uses the envelope binarization circuit to make the analog input signal have a positive envelope and a negative envelope. Because the threshold value is an intermediate value between the envelope and the threshold value, the noise caused by specular reflection and the distortion part of the analog signal caused by noise such as dirt or stains on the white background of the bar code cross the threshold value. Since there is no error, no error occurs in the pulse width of the binarized output, and it is possible to prevent erroneous reading due to dirt or stain on the white background of the bar code.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a bar code detecting device according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a barcode detecting apparatus of the present invention using a plurality of binarizing circuits. FIG. 2 is a diagram showing signal waveforms of respective parts for explaining the operation state of the above-mentioned embodiment. FIG. 4 is a characteristic diagram showing individual output waveforms of a floating binarization circuit and an envelope binarization circuit constituting the barcode detection device of FIG. 1 and an output waveform of the barcode detection device of the present invention.

In FIG. 1, a laser beam 1a emitted from a laser diode unit 1 comprising a semiconductor laser (emission wavelength: 670 nm) and a lens system is 600
The light reflected by the polygon mirror 2 rotating at 0 rpm scans the bar code 3. The reflected light from the bar code 3 is detected as an analog signal by a sensor 4 composed of a PIN photodiode. The detected analog signal is once amplified by the amplifier circuit 5 and becomes the analog input signal A from which the DC component has been removed.
The amplitude detection circuit 6 detects the amplitude of the analog input signal A and outputs an amplitude signal B. The floating binarization circuit 7 binarizes the analog input signal A to form a floating binarization signal C, and the envelope binarization circuit 8 binarizes the analog input signal A to form an envelope binarization signal D. Is output. At this time, floating 2
The operating threshold value of the value conversion circuit 7 is a voltage value which is about 0.6 V lower than the peak value by the voltage drop of the diode D1 shown in FIG. The valley has a voltage value that is about 0.6 V higher than the bottom value by the voltage drop of the diode D2 shown in FIG. As an operation threshold value of the envelope binarization circuit 8, an intermediate value between a positive envelope and a negative envelope of the analog input signal A is used. The selection circuit 9 compares the amplitude signal B with a preset reference voltage F, and outputs the binary signal C of the floating binarization circuit 7 as a binary signal E when the amplitude signal B is lower than the reference voltage. When the amplitude signal B is higher than the reference voltage, selection is made so that the binarized signal D of the envelope binarizing circuit 8 is output as the binarized signal E. Finally, the decoding circuit 1
By means of 0, the selected binarized signal E is transmitted to the host computer as a bar code signal.

Next, the operation of the bar code detector of the present invention will be described with reference to FIG. In FIG. 2, 3 at the top indicates a barcode, and 3a indicates dirt on a white background portion of the barcode. A is an analog input signal, and is a noise Aa due to specular reflection and a noise Ab due to dirt on a white background portion of a barcode.
Contains. B is an amplitude signal indicating the amplitude of the analog signal, which is small at the start of scanning including the start margin, gradually increases when the black level of the bar starts to be detected by scanning, and gradually becomes a certain value. Stabilize.
When the amplitude signal B reaches a preset reference voltage F, switching from the floating binarization circuit 7 to the envelope binarization circuit 8 is performed. By this switching, switching from the output C of the floating binarization circuit 7 to the output D of the envelope binarization circuit 8 is performed, and the output E from the selection circuit 9 is performed.
Is obtained. By setting the reference voltage F for selecting the binarization circuit to a voltage value smaller than the above stable value, a floating binary value is detected in the first bar detection at the start of scanning in consideration of the start margin. The output C of the conversion circuit 7 is selected, and the output D of the envelope binarization circuit 8 is selected for another analog signal A subsequently detected.

As described above, according to the bar code detection device of the present invention, two types of binarization circuits are provided, and two types of binarization circuits are switched and used according to the amplitude value of the analog input signal A. Therefore, there is no erroneous reading at the start of scanning including the start margin, and the detection accuracy of the binarized signal can be increased regardless of the amplitude value of the analog signal A, and disturbance such as specular reflection or noise can be prevented. A strong binarization circuit can be configured.

[0017]

As is clear from the above embodiments, the bar code detecting apparatus of the present invention includes two different types of binarizing circuits and an analog signal amplitude detecting circuit, and performs an initial bar code reading operation. In the stage, the analog signal is binarized by selecting a floating binarization circuit having high reliability in the initial stage of reading, and the amplitude of the analog signal is increased in a range where the amplitude of the analog signal increases after the initial stage. Since the analog signal is binarized by the envelope binarization circuit which is not affected by the influence of noise and noise, there is no erroneous reading of the bar code in the entire range from the start to the end of bar code detection. High reliability is obtained without being affected by noise.

[Brief description of the drawings]

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

FIG. 2 is a waveform diagram of each part in the apparatus.

FIG. 3 is a circuit configuration diagram of a floating binarization circuit;

4A is a waveform diagram of each part of the floating binarization circuit when the amplitude of the analog input signal is proper; FIG. 4B is a diagram showing the floating waveform when the amplitude of the analog input signal is excessive;
Waveform diagram of each part of the digitizing circuit

FIG. 5 is a circuit configuration diagram of an envelope binarization circuit;

FIG. 6 is a waveform characteristic diagram of each part of the envelope binarization circuit.

[Explanation of symbols]

 Reference Signs List 4 light sensor 6 amplitude detection circuit 7 floating binarization circuit (binarization circuit) 8 envelope binarization circuit (binarization circuit) 9 selection circuit A analog signal

Claims (4)

(57) [Claims] A bar comprising an optical sensor and a binarizing circuit for binarizing an analog signal output from the optical sensor.
A bar code detecting device, wherein said binarizing circuit is constituted by a plurality of different types of binarizing circuits. 2. An amplitude detection circuit for detecting an amplitude of an input analog signal, and a selection circuit for selecting one of a plurality of binarization circuits from a level of an output value of the amplitude detection circuit. 2. The bar code detecting device according to claim 1. 3. A plurality of binarization circuits, wherein a threshold value is a voltage value lower than a peak value by a fixed value for a peak of a waveform of an analog signal, and a voltage value is constant from a peak value to a valley of a waveform of the analog signal. 2. The floating binarizing circuit according to claim 1, wherein the floating binarizing circuit uses a high voltage value as a threshold value, and the envelope binarizing circuit uses an intermediate value between a positive envelope and a negative envelope of the analog input signal as a threshold value. Barcode detector. 4. A threshold value of a voltage value which is lower than a peak value by a constant value for a peak of a waveform of an analog input signal and a threshold value of a photo sensor and a constant value which is higher than a peak value for a valley of a waveform of an analog input signal. A floating binarizing circuit for binarizing an analog output signal of the optical sensor having a voltage value as a threshold value, and a threshold value for an intermediate value between a positive envelope of the analog input signal and a negative envelope of the analog input signal Similarly, an envelope binarization circuit for binarizing the analog output signal of the optical sensor, an amplitude detection circuit for detecting the amplitude of the analog output signal of the optical sensor, and a voltage value whose output of the amplitude detection circuit is set in advance. If the output value is less than the predetermined value, the output value of the envelope binarization circuit is selected. And a selection circuit for selecting the bar code.