JPS586187B2 - information reading device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an information reading device for reading information on, for example, a barcode label using a television camera.

Generally, barcode labels, which correspond to price tags attached to products, are automatically read.The barcode label attached to the product is imaged with a television camera, and the imaged video signal is processed to create a barcode label. There is something that reads the information in the code.

When reading information on a barcode label using such a television camera, FIG. 1 shows the barcode label used and a video signal based on the barcode obtained by scanning with the television camera.

In FIG. 1, reference numeral 1 denotes a barcode label, and a barcode 2 with a black and white pattern represents the price of a product, etc. in binary code.

When reading the barcode information on barcode label 1 with a television camera, the information on barcode 2 cannot be read unless the barcode 2 direction on barcode label 1 and the scanning direction of the television camera that captures the image are aligned. , it is necessary to align the direction of the scanning line with the two directions of the barcode.

Here, H regarding the scanning line direction and the two barcode directions.

are shown in FIG. 1A when the directions match, and H and H are shown in FIG.

An information reading device in which the scanning direction of a conventional television camera and the barcode direction are aligned will be explained with reference to FIG.

In FIG. 2, reference numeral 10 denotes an information reading device, which is located above the case 11 and has a transparent window 12 for placing a product on it, and a pedestal 13 for placing the product on the product. a television camera 14 that images the barcode label;
A circular light source 15 that illuminates the transparent window section 12 from above and below, a light shielding plate 16 that prevents the light from the light source 15 from directly entering the television camera 14, a scanning circuit 17 that rotates and scans the television camera 14, and a bar code. It is comprised of a signal processing circuit 18 that detects.

The signal processing circuit 1B includes a video amplifier 19 that amplifies the video signal output from the television camera 14, and an information detection circuit that converts the video signal into a digital signal and detects a signal corresponding to the barcode information printed on the barcode label. 2
Consists of 0.

The scanning circuit 17 controls the rotation of the scanning plane formed by the scanning lines of the television camera 14.

The operation will be explained below.

A product with a barcode label pasted on the pedestal 13 is placed on the transparent window 12 with the barcode label facing down, illuminated by the light source 15, imaged by the television camera 14, and sent to the signal processing circuit 18. The barcode signal of the code label is sent as a video signal.

By the way, when the direction of the barcode 2 on the barcode label 1 and the scanning direction of the television camera 14 almost match, one scanning line H is formed.

Since the entire barcode 2 can be traversed, a complete set of video signals corresponding to the barcode (shown in FIG. 1B) is sent to the output of the television camera 14. However, if the barcode label 1 If the direction of the code 2 and the scanning direction of the television camera 14 do not match and one scanning line H1 cannot cross the barcode 2, an incomplete video signal with some bars missing (as shown in Figure 1C) (as shown in the figure), so the barcode label cannot be read.

Therefore, the scanning surface of the television camera 14 is rotated at a constant speed by the scanning circuit 17, and when the output signal of the television camera 14 is detected and the detected signal is verified to be in a perfect form, then the direction of the barcode 2 is detected. The barcode label 1 attached to the product is read based on the fact that the scanning line H matches the barcode label 1. By the way, the image pickup tube used in a normal television camera has a have.

That is, when light is irradiated, the surface potential of the photoconductive film of the image pickup tube increases with time and with a constant time constant as shown in FIG. 3A.

Next, when the light irradiation is stopped and a scanning electron beam is applied to it, the surface potential of the photoconductive film decreases according to the number of scans, as shown in Figure 3B (in this case, scanning at a rate of 60 fields/second). do.

If a television camera with an image pickup tube having such characteristics is used to capture an image without rotating its scanning plane,
It will look like this:

FIG. 4 is a diagram illustrating the relationship between the scanning plane and the scanning line.

In FIG. 4, the solid line shows the scanning line in the i-th field, and the chain line shows the scanning line in the (i-1)th field, which is rotated by an angle θ with respect to the direction of the i-th field. It is something that

In addition, each conventional scanning line has a width of d1 and an interval between each scanning line of d2.

As explained in Fig. 3, once the image pickup tube is scanned with an electron beam, the surface potential of the photoconductive film does not rise immediately even if the light irradiation continues, so the surface potential of the photoconductive film does not increase immediately in the (i+1)th field. Among the parts to be scanned, the output level is different between part a which is scanned in the i-th field and part b which is not scanned.

FIG. 5 shows the appearance of this video signal. In this way, the television camera used in conventional information reading devices scans with a gap d2 between the scanning lines, so when the scanning surface is rotated to read the barcode, the target bar In addition to the code information, the above-mentioned error signal is generated, which has the disadvantage of posing an obstacle to signal detection.

The present invention has been made in view of the above points, and it is an object of the present invention to provide an information reading device that can reduce reading errors caused by afterimages of a television camera by using a selection circuit to reject video signals caused by non-uniform afterimages.

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 6, the same reference numerals as in FIG. 2 indicate the same or corresponding parts.

Reference numeral 21 denotes a scanning plane control circuit which controls the scanning plane made up of scanning lines to rotate in stages.

22 is a gate circuit provided between the video amplifier 19 and the detection circuit 20 in the signal processing circuit 18;
This constitutes a selection circuit that selects a video signal based on a control signal from the scanning plane control circuit 21.

The specific function of the scanning plane control circuit 21, which is control for rotating the scanning plane in stages, will be described.

Among the scanning lines that effectively cross the barcode 2 printed on the barcode label 1 shown in FIG. 1, the scanning line with the highest angle is H.

1. The scanning line with the lowest angle is H02, and the angle difference is θ1
2, scanning is performed in a fixed direction during two or more field scans in a certain stage, and the scanning direction is rotated by (θ12−α) every time the field scan is performed twice or more.

Here, α is a constant determined by the number and width d of scanning lines required for barcode reading.

The specific control for rotating the angle (θ12 - α) stepwise is to apply a deflection signal similar to that of a normal television camera to the deflection coil for scanning the electron beam in the television camera 14, and then This is performed using a pulse motor by applying pulses at intervals corresponding to two or more fields.

As another control, the deflection coil of the television camera 14 is connected to a pair of deflection coils (vertical and horizontal deflection coils) used in a normal television camera, and another pair of deflection coils are rotated 90' relative to this pair of deflection coils. This is accomplished by applying to each pair of deflection coils electrical signals obtained by balanced modulation of vertical and horizontal deflection frequency signals with stepwise rotation signals.

Next, the operation shown in FIG. 6, which shows an embodiment of the present invention, will be explained.

In the i-th field, the video signal from the television camera 14 is amplified by the video amplifier 19 and then input to the gate circuit 22 .

The gate circuit 22 is kept open during the i-th field by a control signal from the scanning plane control circuit 21.
The video signal is input to the data detection circuit 20 and subjected to signal processing.

When the scanning in the i-th field is completed, the scanning plane is rotated by an angle (θ12-α) and the gate circuit 22, which is a selection circuit, is kept closed for this period by a control signal from the scanning plane control circuit 21. Control.

In this way, scanning of the (i+1)th field begins.

By doing so, the video signal containing the afterimage signal due to the scanning line one field before is blocked and is not subjected to signal processing.

In the next (i+2)th field period, if the scanning plane is not rotated and the gate circuit 22 is the same as the (i+1)th field, the afterimage signal of the i-th field similar to the (i+1)th field will be generated. The included video signal will not undergo any signal processing.

At the same time, after the (i+1)-th and (i+2)-th fields are completed, the influence of the afterimage caused by the i-th field scanning is reduced.

In this state, during the (i+3)th field period, the gate circuit 22 is opened and the video signal is processed as in the i-th field period.

Next, after rotating the scanning plane, the same excitation is repeated.

With such a configuration, reading errors due to afterimages of the television camera can be reduced.

Here, in the above embodiment, when the video signal is processed by the data detection circuit 20, the two fields are rejected after the scanning plane is rotated. Thereafter, the video signal of the (i+1)th field is discarded while leaving the scanning plane as it is.

It is clear that the same result can be obtained by rotating the scanning plane and processing the video signal of the (i+3)th field after discarding the video signal of the (i+2)th field in this state. It is.

Further, by increasing the number of fields in which the video signal is rejected by the gate circuit 22, which is a selection circuit, more than the above-mentioned number of times, the effect becomes greater.

As described above, the present invention can reduce the number of reading devices caused by afterimages of television cameras by configuring an information reading device in which a selection circuit rejects video signals caused by uneven afterimages.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing the relationship between the barcode label and the scanning direction as well as its video signal, Figure 2 is a configuration diagram of a conventional information reading device that reads barcode labels, and Figure 3 is a characteristic curve diagram of a television camera. , FIG. 4 is an explanatory diagram showing a conventional scanning line, FIG. 5 is a waveform diagram showing a video signal output during the scanning shown in FIG. 4, and FIG. 6 is a configuration of an information reading device according to an embodiment of the present invention. It is a diagram. In the figure, 12 is a transparent window, 13 is a pedestal, 14 is a television camera, 20 is a bar code detection circuit, 21 is a scanning plane control circuit, and 22 is a gate circuit constituting a selection circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A pedestal having a transparent window portion, a television camera provided corresponding to the transparent window portion of the pedestal and having a rotating scanning surface formed by scanning lines, and a video camera from the television camera. a detection circuit that converts the signal into a digital signal and detects a signal corresponding to barcode information; and a detection circuit that is connected to the television camera and mechanically or electrically controls the rotation of the scanning surface in stages. When the scanning plane is rotated by the scanning plane control circuit after one field scanning, the video signal containing the afterimage signal from the scanning line one field before is not sent to the detection circuit. An information reading device comprising a selection circuit for rejecting a predetermined number of fields. 2. Information according to claim 1, characterized in that a pulse motor is used in the scanning plane control unit and the deflection coil of the television camera is mechanically rotated so that the rotation of the scanning plane becomes stepwise. reading device. 3. The information reading device according to claim 1 or 2, characterized in that the selection circuit is provided at the output of the television camera or at the input of the detection circuit.