JPH0341584A - Barcode detection device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a barcode detection device used in POS, logistics, production management, and the like.

2. Description of the Related Art Conventionally, a waveform shaping circuit has consisted only of a low-pass filter that removes a reset pulse waveform component from a discrete signal and passes a barcode signal corresponding to a barcode image.

FIG. 4 shows a specific circuit of a conventional waveform shaping circuit.

sB is a low-pass filter whose cutoff frequency is determined by the constants of resistor 9d and capacitor 90.

When the value of the resistor 9d is R and the value of the capacitor 90 is C, the cutoff period e! , the number f is f = 1/(sπR
C) It will be decided on the mountain. If this cutoff frequency f is set between the frequency of the reset pulse and the frequency of the barcode signal, the component of the reset pulse waveform can be removed from the discrete signal and the barcode signal can be passed.

Problem to be Solved by the Invention However, it is difficult to remove only the reset pulse waveform component from the discrete signal without affecting the barcode signal at all using the low-pass filter alone; Barcode signal 1 corresponding to bar
is attenuated by However, it was difficult to read barcodes with thin bars.

FIG. 5 shows waveforms at various parts of the circuit of FIG. 4. a is a barcode, and b is C corresponding to the barcode.
This is the output signal of the CD image sensor, and is a discrete signal that includes a reset pulse. When this discrete signal is passed through a low-pass filter, it becomes a barcode signal from which the reset pulse has been removed.If the cutoff frequency is set to a value close to the frequency of the barcode signal, the C
The barcode signal corresponding to a thin bar, such as , becomes an attenuated signal, making it impossible to detect the thin bar. Also,
If the cutoff frequency is set to a value close to the frequency of the reset pulse, the result will be a noisy signal that cannot completely remove the reset pulse like d.

Means for Solving the Problems In order to solve the above problems, a first aspect of the present invention includes: a light projector for illuminating a bar code; an image sensor for receiving reflected light from the bar code; For a barcode detection device equipped with a waveform shaping circuit that converts a discrete signal output from a CCD image sensor into a continuous signal, the waveform shaping circuit is connected to a reset pulse integrating circuit that integrates a reset pulse signal of the discrete signal. It is composed of

The second aspect of the present invention also provides a light projector for illuminating a barcode, an image sensor for receiving reflected light from the barcode, and a continuous signal that converts the discrete signal output from the CCD image sensor into a continuous signal. In a barcode detection device equipped with a waveform shaping circuit for converting the discrete signal into It is composed of.

Operation In the above configuration, the discrete signal input to the reset pulse integration circuit is amplified by a PNP transistor.

When the potential of the discrete signal decreases, the PNP transistor acts as an emitter follower circuit, and when the potential of the discrete signal increases, it acts in the cutoff direction. At this time, the charge stored in the capacitor is discharged through the resistor,
The emitter potential of a PNP transistor increases only gradually. The input discrete signal of tb magnitude is integrated by the capacitor and resistor only in the direction in which the potential increases (in the direction in which the reset pulse of the discrete signal is generated). The output waveform of this reset pulse integration circuit becomes a signal in which the reset pulse component of the discrete signal is substantially removed.

The low-pass filter extracts the barcode signal from the waveform of the signal from which the reset pulse outputted from the reset Hullless integration circuit has been substantially removed, and converts it into a smoothed continuous signal. Since the reset pulse component of the discrete signal is almost removed by the reset pulse integration circuit, the reset pulse component can be removed even if the cutoff frequency of the rover filter is set to a value close to the reset pulse frequency. , without attenuating the barcode signal.

Therefore, barcode signals corresponding to thin bars can also be detected with high accuracy, and barcodes with narrow bar widths can be read easily.

Examples Examples of the present invention will be described below. In FIG. 1, 1 is a barcode label, and a barcode is printed on the surface of the label. 2 is a case of a barcode detection device, and the length of the reading margin is 65n. Reference numeral 3 denotes a light source that illuminates the barcode, and is composed of an LED array in which six LEDs with a peak wavelength of 660 nm are arranged. 4 is a reflecting mirror that reflects light reflected from the barcode in a specific direction.

The reflected light is passed through a lens (focal length f = 29.2511) 6
CCD image sensor with 2048 pixels through
(MN3644 manufactured by Neko Electronics Industry Co., Ltd.) A barcode image is formed on 6.

The dash-dotted line in FIG. 1 shows the locus of light applied to the optical shape.

Reference numeral 7 denotes a drive circuit for the CCD image sensor 6, which generates a series of pulses necessary for driving the CCD image sensor 6 from the clock of the clock generator 8. In response to this series of pulses, the CCD image sensor 6 converts the barcode image into an electrical signal by electronic scanning. Furthermore, since this electrical signal is a discrete signal containing pulses synchronized with the series of pulses, this discrete signal is converted into a continuous signal by a waveform shaping circuit 9 composed of a reset pulse integration circuit and a low-pass filter. . 10 is an analog amplifier circuit that amplifies the continuous signal output from the waveform shaping circuit 9.

Reference numeral 11 denotes a comparator circuit which converts the amplified signal from the analog amplifier circuit 1° into high level and low level binary signals corresponding to the black and white bars. A counter 12 counts the clocks generated by the clock generator 8 while the binary signal is inverted at 1. This count value corresponds to bar 1 of the barcode. This count file is stored in the memory of a microcomputer (Hitachi HD847180) 13.

Based on the bar width information stored in this memory, the microphone computer 13 executes arithmetic processing and decodes the barcode. 14 is a communication circuit which communicates the data decoded by the microcomputer 13 to the Honuto computer.

Next, the operation of the above configuration will be explained.

In FIG. 1, barcode label 11Y:i3 is irradiated. As a result, the reflectance differs according to the white and dark areas of the barcode, so that reflected light having a light intensity distribution corresponding to the barcode is generated. This reflected light is reflected by mirror 4. A barcode image is formed as an image on a CCD image sensor-e through a lens 5. The CCD image sensor 6 receives a series of pulses necessary for driving from the driving circuit 7, and converts the barcode image into an electrical signal corresponding to the barcode by an electronic scanning operation. This electrical signal is a discrete signal containing pulses synchronized with the series of pulses. This discrete signal is applied to the waveform shaping circuit 9.

The operation of this waveform shaping circuit 9 will be explained with reference to FIG. 2 and FIG. 3. 9A is a reset pulse integration circuit that integrates only when the reset pulse of the discrete signal is generated. The input discrete signal (a in Figure 3) is P
It is amplified by the NP type transistor 9a. When the potential of the discrete signal decreases, the PNP transistor 9a functions as an emitter follower circuit, and when the potential of the discrete signal increases, it functions in the cutoff direction. At this time, the charge stored in the capacitor 9b is discharged through the resistor 9C, and the emitter potential of the PNP transistor 9a gradually increases. The discrete signal inputted one by one is integrated by the capacitor 9b and the resistor 9c only in the direction in which the potential increases (in the direction in which the reset pulse of the discrete signal is generated). The output waveform of this reset pulse integration circuit 9A is the third
As shown in b of the figure, a signal is obtained in which the reset pulse component of the discrete signal is almost removed. 9B is a low-pass filter that extracts the barcode signal component from the signal output from the reset pulse integration circuit 9A, from which the reset pulse component has been almost removed, and converts it into a smooth continuous signal (C in Figure 3).
).

As described above, the waveform shaping circuit 9 can convert the above-mentioned separation circuit into a smooth continuous signal.

This continuous signal is amplified by an analog amplifier circuit 1o and converted by a comparator 11 into a binary signal of high level and low level corresponding to the black bar and the white bar of the bar court. This 2
The width of the high level and low level of the digitized signal is measured by the counter 12 and the clock generator 8, and the length information of the bar of the bar code is taken into the microcomputer 13.

Arithmetic processing is performed based on this imported bar length information to decode the oil barcode. The decoded barcode is communicated to the host computer by communication circuit 14.

Effects of the Invention As described above, the present invention has the excellent effect of improving the resolution of the device because only the reset pulse component can be removed without attenuating the barcode signal. When a barcode was actually decoded by a barcode detection device with a reading port of 66 m, it was found that a barcode (code Cl2s) with a minimum par width of 0.17On was obtained using the conventional circuit.
However, a barcode detection device using the circuit of the present invention can now decode a barcode (code Cl2a)j with a minimum bar of 1i0.12s tm.

Another advantage is that the waveform shaping circuit can be realized with a simple circuit configuration.

[Brief explanation of drawings]

Fig. 1 is a block circuit diagram of a barcode detection device showing an embodiment of the present invention, Fig. 2 is an electric circuit diagram of the same main part, Fig. 3 is a signal waveform diagram of each part of Fig. 2, and Fig. 4 5 is a circuit diagram of a main part of a conventional bar code detection device, and FIG. 5 is a signal waveform diagram of each part of FIG. 4.

Claims (2)

[Claims] (1) A light projector for illuminating the barcode, a CCD image sensor for receiving reflected light from the barcode, and a CCD output from the CCD image sensor.
A barcode detection device comprising a waveform shaping circuit that converts a discrete signal containing a reset pulse corresponding to each pixel into a continuous signal, wherein the waveform shaping circuit is a reset pulse integrating circuit that integrates the reset pulse signal of the discrete signal. A barcode detection device consisting of. (2) A light projector for illuminating the barcode, a CCD image sensor for receiving reflected light from the barcode, and a CCD output from the CCD image sensor.
A barcode detection device comprising a waveform shaping circuit that converts a discrete signal containing a reset pulse corresponding to each pixel into a continuous signal, wherein the waveform shaping circuit is a reset pulse integrating circuit that integrates the reset pulse signal of the discrete signal. and a low-pass filter that smoothes the output signal of the reset pulse integration circuit.