JPS5810270A - Converting circuit for bar code reader reading signal - Google Patents

Abstract

PURPOSE:To obtain a conversion pulse with fidelity to a pattern from an analog signal independently of an interval and an angle between a bar code and a reader, and dirt of the bar code, by obtaining a conversion pulse from a reading analog signal of a bar at the scanning initial of the bar code reader. CONSTITUTION:An operational amplifier 2 amplifies an output signal Ea of a bar code reader. Further, a reference voltage circuit 3 consisting of diodes D1 and D2, capacitors C1-C3 and resistors R1-R3 receives an output signal of the amplifier 2 and generates a reference voltage Er. A comparator 4 converts an analog signal Ea' from the amplifier 2 based on the reference voltage given from the reference voltage circuit 3, into a pulse corresponding to a bar code pattern. The pulse generated from an output terminal 5 is processed at an electronic computer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a barcode reader reading signal conversion circuit that converts an analog signal output from a barcode reader into a pulse signal corresponding to a barcode pattern to be read.

In product distribution departments of factories, supermarkets, department stores, etc., stickers with a barcode symbol as shown in Figure 1 are pasted on packaging boxes to identify large quantities of products. A system is used to optically read the barcode and manage the number of people and stock of the product.

In this type of crowd management or inventory management system, the barcode is read by a pen-type barcode reader, and the analog signal read by the barcode reader is converted into a barcode that corresponds to the barcode pattern. It is converted into a pulse signal, and the converted pulse signal is processed by an electric X machine.

Therefore, the converted pulse signal obtained from the analog signal of the barcode reader must faithfully correspond to the barcode pattern to be read.

When scanning a barcode as shown in Figure 1 from point 0 to point P at a constant speed with a barcode symbol on a pen-shaped barcode reader, the output signal of the ideal Parcode reader is as shown by the solid line in Figure 2. As shown by Ea, the maximum value Emax and minimum value Emln of the output signal waveform are approximately constant.

However, the maximum value Emax and the minimum value Emin may change as shown by the dotted line in FIG. 2 due to the influence of the overall dirt of the barcode, printing unevenness, the gap between the barcode and the reader, the corner #L, etc. Therefore, it is necessary to convert the output signal into pulses corresponding to the barcode pattern without being affected by the overall dirt on the barcode, uneven printing, the gap between the barcode and the reader, and the angle.

As shown in Figure 2, the maximum value Emax and minimum value 1i, min of the read signal of a barcode reader are generally affected by dirt on the barcode, the gap between the barcode and the reader, the angle, etc. The period, ie, the time rlJ of the read signal, faithfully reflects the barcode pattern without being affected by the overall dirt on the barcode, the gap between the barcode and the reader, and the angle. Therefore, the second method for obtaining a pulse signal that faithfully corresponds to the barcode pattern from the analog signal of the barcode reader is
As shown in the figure, the average flI\Emean of the output signal Ea that changes from the maximum value Emax to the minimum value Emix is calculated, and the analog signal Ea is converted into a digital signal by the conversion circuit using the average value Emean as a reference voltage. E
It is possible to obtain conversion pulses that are faithful to the barcode pattern as shown in FIG. However, in this method, as shown in FIG. 3, at least at time imf, and in the output signal shown by the broken line in FIG. 2, the minimum value Emi is reached at time t3-1.
Since n is unknown, it is not possible to determine the average value Emean at time '1+112 at time t3, so until these times a reference voltage cannot be obtained and a conversion pulse faithful to the barcode pattern cannot be obtained. There will be no. That is, the first method has the disadvantage that the conversion pulse of at least the first bar B of the bar code as shown in Figure 1 will be inaccurate or not obtained at all.

A second method to deal with the shortcomings of the first method described in AfI is to vary the period of the analog signal Ea as indicated by the broken line in FIG. Create a voltage Ed that is smaller than the maximum voltage by an arbitrary constant voltage e and larger than each minimum value by a voltage e, and convert the analog signal Ea in the conversion circuit using the voltage E (l as a reference voltage) as shown by the broken line Ee in Figure 4. There is a method of converting into a pulse signal corresponding to a barcode pattern. According to this second method, it is possible to convert the initial scanning signal of the barcode reader without missing it. As mentioned above, the method of using the voltage Ed, which changes as Ea changes, as the reference voltage, is based on the maximum value E of the analog signal due to the overall dirt on the barcode, the gap between the barcode and the reader, and the angle.
If the max+minimum value Emln is affected, the amplitude ratio centered on the average value Em6an will not be constant, making it impossible to obtain a conversion pulse faithful to the barcode pattern.

Therefore, the present invention makes use of the advantages of the first method and the second method, and uses the second method at the initial stage of scanning by the barcode reader to determine whether bar B+I or B1+Bs at the initial stage of scanning. Reliably obtain the conversion pulse from the read analog signal, and then use the first method to obtain the fL conversion pulse from the analog signal faithfully to the PAL code pattern regardless of dirt on the barcode, the gap between the barcode and the reader, the angle, etc. It is an object of the present invention to provide a barcode reader reading signal conversion circuit that can be obtained.

Next, the invention will be explained in detail using the drawings.

FIG. 5 is a circuit diagram showing an embodiment of the barcode reader reading signal conversion circuit according to the present invention, and FIG. 6 is a circuit diagram showing the amplified analog signal Ii:a/of the barcode reader for explaining its operation. FIG. 3 is a diagram showing the relationship between the reference voltage Er of the comparator and the reference voltage Er of the comparator. In FIG. 5, 1 is an input terminal, and the output signal Ea of the barcode reader is input to the input terminal. 2 is an operational amplifier that amplifies the output signal Ea of the barcode reader (I Dl* DB + D
B + D4 is a diode, D 1 r D 2 has the function of regulating the charging and discharging of the capacitor Clr C2,
D B + D 4 has the function of selectively applying the reference voltage Er and the bias voltage Eb to the comparator 5, as will be described later. CI l C2+ Cm is a capacitor, and capacitors C1+ and C2 are equal and larger than capacitor 03. R1+ J*R
1 is a resistor, and the resistor R1*Rg*R3 is set so that its time constant is equal to that of the corresponding capacitor and is sufficiently larger than the maximum cycle of the barcode output waveform. The diode D11D1. Capacitor CI, C! .

A circuit composed of C3r resistors R1+R1+Rs is a reference voltage circuit 6 that receives the output signal of the amplifier 2 and generates a reference voltage Er. A comparator 4 has the function of converting the analog signal Ea' from the amplifier 2 into a pulse corresponding to a bar code pattern based on the reference voltage generated from the reference voltage circuit 3. 5 is an output terminal, and the output terminal 5
The pulses emitted are processed by a computer.

In FIG. 6, 'Ea' is a signal obtained by amplifying the barcode reader reading signal, and represents the voltage at point X of the circuit in FIG. 5, and Er is a reference voltage, which is the output of the reference voltage circuit 3 in FIG. The voltage at the end Y point is shown.

Next, the operation of the circuit shown in FIG. 5 will be explained. As voltage Ea' increases from time t1 in FIG.
Capacitor C1+C1 passes voltage E through diode D1.
Charged until a' reaches its maximum value, the respective voltage becomes E1+E
Becomes 1. Next, the voltage Ea' starts to decrease and the capacitor becomes 0.
3, capacitor 03 is discharged through diode D2 until voltage g a / reaches its minimum value, capacitor C2 is charged, and the voltages are respectively lowered to E4.3.
El, and the capacitor C maintains the voltage E1. Next, when the evening pressure Ea' rises again and becomes more than the voltage Et1E4, the capacitor C1+ CB is charged again through the diode DI until the evening pressure Ea' reaches its maximum value, and the voltage of the capacitor 〇l further increases. It becomes Es. The voltage of capacitor C3 becomes R6, and capacitor Ct maintains voltage E3. Then the voltage Ea′ decreases again and the voltage E・
-When it becomes less than Es, the capacitor〇s becomes a diode Dg
The voltage Ea' is discharged through the capacitor C2 until it reaches the minimum value, and the capacitor C2 is charged again, and the voltage Ea' increases further to become the voltage E7 and the voltage of the capacitor C3 becomes Ea. In this way, the voltage of capacitors C1+C2 gradually increases, and the voltage fluctuation of capacitor C3 becomes smaller, and the voltage Ea'
stabilizes at the average value between the maximum and minimum values. In other words, the voltage at point Y has the waveform of voltage gr shown by the broken line in FIG. Therefore, if the voltage Er is used as a reference voltage and the voltage Ea' is applied to the comparator 4, the scanning initial stage of the barcode reader converts the analog signal Ea using the second conversion method, that is, using the voltage Ed shown in FIG. 6 as the reference voltage. This method is then gradually switched to a method of converting the average value Emean as a reference voltage. Also, in Fig. 6, the voltage E
b is the output of the comparator when there is no signal at a low potential (
The bias voltage is used to maintain the black level of the barcode.
Diode DBrD4 has reference voltage Er and bias voltage g
It has the function of selecting b and applying it to the comparator 4.

FIG. 7 is an example of a modification of the circuit shown in FIG. 5, and a voltage of ga' -Er appears at point Y as shown in FIG.

Therefore, if this is applied to the comparator 4 at zero level, the desired converted pulse output can be obtained. In Figure 8, the voltage E
b' is a bias voltage for keeping the output of the comparator 4 at black level when there is no signal.

As described in detail above, the barcode reader read signal conversion circuit according to the present invention receives the read analog signal from the barcode reader and outputs the magnitude corresponding to the maximum value and minimum value of the analog signal. A reference voltage generating circuit is provided, which consists of a circuit that generates an output signal, and a circuit that generates an output of a magnitude corresponding to the average value of the maximum and minimum values of the analog signal. value and minimum 1+f
A reference voltage of a magnitude corresponding to i K is gradually obtained and a magnitude corresponding to the average value of the maximum value and minimum value is obtained, and a pulse corresponding to the barcode pattern is obtained by a comparator based on this reference voltage, Alternatively, a pulse corresponding to the barcode pattern is obtained by a comparator based on the base IL pressure from the voltage signal of the difference between the read analog signal from the barcode reader and the reference voltage. It is possible to reliably obtain a conversion pulse from a read signal of a bar, and it is possible to obtain a conversion pulse that is faithful to the barcode pattern from the read analog signal regardless of the overall dirt on the barcode, the gap between the barcode and the reader, the angle, etc. It has an excellent effect of making it possible to obtain.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the barcode, Figure 2 is a diagram showing the output signal of the barcode reader, Figure 6 is a diagram showing the relationship between the output signal of the barcode reader and the reference voltage, and Figure 4 is a diagram showing the conversion pulse. FIG. 5 is a circuit diagram showing an embodiment of the barcode reader reading signal conversion circuit according to the present invention, FIG. 6 is a schematic diagram of the station 1, and FIG. 7 is a barcode reader reading signal according to the present invention. A circuit diagram showing another embodiment of the conversion circuit, FIG. 8, is shown in lighter color. 2: Arithmetic amplifier +13 unit, 3: Reference voltage circuit, 4: Comparator, Ea: Signal read by barcode reader, E
('Reference voltage, Eb: Bias voltage Patent applicant: Mechano Co., Ltd. Representative: Patent attorney: Tsuji Sanagai, 2 persons------

Claims (1)

[Claims] A circuit that receives an analog output signal read from a barcode reader generates an output having a size corresponding to the maximum value f + ji minimum value of the analog output signal, and a circuit that generates an output having a size corresponding to the maximum value and the minimum value of the analog output signal. a reference voltage generating circuit which generates an output signal of Barcode reader read signal conversion characterized in that a conversion puffless is obtained from the analog signal using the output signal of a reference voltage generation circuit as a reference voltage, or a conversion pulse is obtained from the output signal of the reference voltage generation circuit using a base voltage as a reference. circuit.