JPH0568753B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to improvements in barcode scanners.

[Prior Art] Conventionally, as a barcode scanner, one shown in FIG. 4 is known. This involves installing a linear light source 1 made of a rod-shaped tungsten lamp or a plurality of LEDs arranged in a row, and emitting light obliquely from the linear light source 1 to a medium 2 on which a barcode is printed. The light is received by a reflecting mirror 3 provided almost directly above, and the light from the reflecting mirror 3 is transmitted to a lens system 4.
The light is incident on the one-dimensional line sensor 5 via the.

After the light incident on the line sensor 5 is converted into an analog electrical signal, it is input to a signal processing circuit 6 where it is amplified, sampled and held as shown in FIG. It is converted into a digital signal of "1" and "0" indicating the This digital signal is compressed by a run-length encoding circuit 8 into a run-length code indicating the width of the black and white bars, then converted into a character signal by a decoding circuit 9, and then format checked and modulus by an editing circuit 10. After checking and correction of the reading direction, the data is transferred from the interface circuit 11 to a data processing unit such as a terminal.

[Problems to be solved by the invention] In such a device, for example, from the linear light source 1 to the medium 2
Assuming that the angle between the incident optical path and the reflected optical path from the medium 2 to the reflecting mirror 3 is θ°, the reading surface A of the barcode scanner is parallel to the medium 2 as shown in Fig. 6. When the reflector 3 is installed and is located almost directly above, the angle of incidence and the angle of reflection are not symmetrical with respect to the plane perpendicular to the surface of the medium 2, so the reflector 3
When viewed from above, no specular reflection occurs on the surface of the medium 2, and therefore the output from the line sensor 5 becomes a signal whose level changes correctly depending on the white and black of the barcode, as shown in FIG.

However, as shown in Figure 8, if the reading surface of the barcode scanner is tilted by Aθ/2° with respect to the surface of medium 2, the angle of incidence and angle of reflection will be symmetrical with respect to the plane perpendicular to the surface of medium 2. When viewed from the reflector 3, specular reflection occurs on the surface of the medium 2, and as a result, the output from the line sensor 5 has a higher level in the black part of the barcode as shown in Figure 9, making it difficult to read the barcode. A difficult problem arose. In particular, when a glossy medium such as a plastic film with a barcode printed on it or an aluminum can with a barcode printed on it is used as the medium 2, this problem becomes noticeable and the barcode cannot be read at all.

This invention was made to solve this problem, and even if the reading surface is tilted with respect to the medium, it is possible to read barcodes without causing specular reflection. The purpose of the present invention is to provide a barcode scanner that can reliably read barcodes.

[Means for solving the problem] This invention irradiates light from a line light source onto a medium on which a barcode is printed, reads the barcode on the medium with a one-dimensional line sensor, and digitizes the read data. In a barcode scanner that decodes and transmits data to the outside, at least two linear light sources of the same color are installed, each of which is placed parallel to the reflected optical path from the medium to the line sensor at different angles, and sequentially time-divided. The lighting is controlled by

[Function] In the present invention having such a configuration, at least two linear light sources of the same color that irradiate light onto the medium are provided, and each of the linear light sources is controlled to turn on in a sequential time-sharing manner. Even if specular reflection occurs due to the light from the line sensor, the bar code on the medium can be reliably read by the line sensor because no specular reflection occurs when other line light sources are turned on.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

As shown in Figure 1, two lamps are made of rod-shaped tungsten lamps or multiple LEDs arranged in a row.
Two linear light sources 21 and 22 are provided tilted at a predetermined angle, for example θ°, in front and back with respect to a plane perpendicular to the reading surface. Also, a reflecting mirror 23 is placed on a surface perpendicular to the reading surface.
has been established. The linear light sources 21 and 22 alternately irradiate light onto a medium 24 on which a barcode is printed, the reflected light from the medium 24 is received by the reflecting mirror 23, and the light from the reflecting mirror 23 is transmitted through a lens system 25. and enters the one-dimensional line sensor 26.

The light incident on the line sensor 26 is converted into an analog electrical signal, processed by a circuit similar to the circuit shown in FIG. 5, and then transferred to a data processing unit such as a terminal. It's summery.

Each of the linear light sources 21 and 22 is as shown in FIG.
NPN type transistors 27 and 2 for V _C power supply respectively
8. The line sensor 26 is connected to the base of each of the transistors 27 and 28.
Signals S ₁ and S ₂ that alternately go high level are input in synchronization with the scanning period.

In this embodiment having such a configuration, the transistors 27 and 28 are turned on and off alternately in synchronization with the scanning period of the line sensor 26 using the signals S ₁ and S ₂ , thereby turning on and off each of the line light sources 21 and 22. The medium 24 is alternately irradiated with light, and the reflected light is incident on the line sensor 26 via the reflecting mirror 23 and the lens system 25. The barcode printed on the medium 22 is then read by the line sensor 26.

In this device, for example, as shown in FIG.
If the angle of incidence from the linear light source 21 to the medium 24 and the angle of reflection from the medium 24 to the reflecting mirror 23 are tilted backward by θ/2° relative to the plane of They almost match and specular reflection occurs. However, when one scanning period of the line sensor 26 ends, the line light source 21 turns off and the line light source 22 turns on. The light from the linear light source 22 enters the medium 24 at a fairly shallow angle, so that no specular reflection occurs when viewed from the reflecting mirror 23. Thus, the line sensor 26 can reliably read the barcode on the medium 24.

For example, as shown in FIG. 3b, if the reading surface A of the barcode scanner is tilted forward by θ/2° with respect to the surface of the medium 24, the angle of incidence from the linear light source 22 to the medium 24 will change. The angles of reflection from the medium 24 to the reflecting mirror 23 substantially coincide with each other with a plane perpendicular to the surface of the medium 24 in between, and specular reflection occurs. However, when one scanning period of the line sensor 26 ends, the line light source 22 is turned off and the line light source 21 is turned on. The light from the linear light source 21 enters the medium 24 at a fairly shallow angle, so that no specular reflection occurs when viewed from the reflecting mirror 23. Thus, the line sensor 26 can reliably read the barcode on the medium 24.

In this way, even if the reading surface of the barcode scanner is tilted backward or forward with respect to the medium 24 and specular reflection occurs due to one line light source, no specular reflection will occur at all when the other line light source is turned on. Therefore, the line sensor 21 can reliably read the barcode from the medium 24.

In the above embodiment, the two linear light sources were provided at an angle of the same θ degrees in front and back with respect to a plane perpendicular to the reading surface of the barcode scanner, but the invention is not necessarily limited to this, and the inclination angle of each linear light source may be may be different. Further, in the embodiment described above, two line light sources were provided, but the invention is not necessarily limited to this, and three or more line light sources may be provided.

[Effects of the Invention] As detailed above, according to the present invention, barcodes can be read without specular reflection even if the reading surface is tilted with respect to the medium. It is possible to provide a barcode scanner that can reliably read barcodes.

[Brief explanation of drawings]

1 to 3 show embodiments of the present invention, in which FIG. 1 is a perspective view showing a schematic configuration, FIG. 2 is a control circuit diagram of a line light source, and FIG. 3 is a bar code for a medium. 4 to 9 show conventional examples, and FIG. 4 is a perspective view showing a schematic configuration, and FIG. is a block diagram showing the circuit configuration, FIG. 6 is a diagram for explaining the barcode reading state when the reading surface of the barcode scanner is set parallel to the medium, and FIG. 7 is the state shown in FIG. 6. Figure 8 shows the output waveform of the line sensor at
The figure is a diagram for explaining the barcode reading state when the reading surface of the barcode scanner is tilted backwards with respect to the medium. Figure 9 is a diagram showing the output waveform of the line sensor in the state of Figure 8. It is. 21, 22...Line light source, 23...Reflector, 24
...Medium, 26...One-dimensional line sensor.

Claims (1)

[Claims] 1 In a barcode scanner that irradiates light from a line light source onto a medium on which a barcode is printed, reads the barcode on the medium with a one-dimensional line sensor, digitizes the read data, decodes it, and transmits it to the outside. , characterized in that at least two of the linear light sources of the same color are provided, each of the linear light sources is provided parallel to the reflected optical path from the medium to the line sensor at different angles, and lighting is controlled sequentially in a time-sharing manner. barcode scanner.