JPS588022B2 - Barcode label reader - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a barcode label reading device that reads barcodes with a light and shade pattern.

In a barcode label reading device that uses a television camera to capture images of barcode labels affixed to products placed on a product stand, one way to read barcodes on barcode labels is to scan the barcode while changing the scanning direction of the television camera. There is a method of capturing an image of a code label and reading an image signal when the direction in which the barcodes on the label are arranged coincides with the scanning direction of a television camera.

If the image signal is read continuously while changing the scanning plane in this way, if the number of scanning lines on the screen is small and there are gaps, the scanning lines may be distorted due to the afterimage effect of the television camera's image pickup tube. Unread signals from gaps between scanning lines on different screens are output in an overlapping manner.

Therefore, there is a drawback that it is not possible to extract only the necessary signals and accurately read the information on the barcode label.

The present invention provides a barcode label reading device that can accurately read barcode label information by providing a light shielding plate that blocks the optical path at a predetermined interruption ratio in the optical path from the product placement stand to the television camera. This is what we provide.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of a reading device according to the present invention, in which 1 is a housing, 2 is a product table having a transparent plate, and 3 is a barcode label affixed to a product placed on the product table 2. A television camera captures an image through a transparent plate, 4 is a light source that illuminates the barcode label on the product stand 2, 5 is a first light shielding plate that prevents the light from the light source 4 from directly entering the television camera 3, and 6 is a bar. A second light-shielding plate 7 is provided in the optical path from the code label to the television camera 3 and interrupts the optical path at a predetermined ratio. Reference numeral 7 indicates a drive device that rotates the light-shielding plate 6 at a predetermined speed.

As shown in FIG. 2, the second light-shielding plate 6 is formed by cutting out a part of a circular plate to form a light-shielding part 61 and a light-passing part 62.

Next, the operation shown in FIG. 1 will be explained.

When you place a product with a barcode label on product placement stand 2,
The television camera 3 images this and outputs an image signal.

At this time, check the alignment direction of the barcode labels and the TV camera 3.
If the scanning directions of the barcode labels do not match, reading will not be possible, so the scanning direction of the television camera 3 should be constantly rotated, and reading will be performed when the direction in which the barcode labels are lined up and the scanning direction of the television camera 3 match. ing.

On the other hand, the disc-shaped second light shielding plate 6 is rotated at a constant cycle by a driving device 7.

The rotational speed of the scanning plane of the television camera 3 is set to θ/n per frame, and the rotational speed of the second light-shielding plate 6 is controlled to rotate once per n frames.

Note that θ is a constant determined by the width and length of the barcode, and for example, θ−20° is selected.

Assume that n=4. That is, the rotational speed of the scanning plane of the television camera 3 and the rotational speed of the second light shielding plate 6 are synchronized with each other, and the second light shielding plate 6 is rotated at a predetermined period.

If the above relationship is chosen, as shown in Figure 3A, 4
The light from the barcode label enters the TV camera 3 only once per frame (i frame period), and is blocked during other periods (i+1, i+2, i+3 frame periods), so the video output of the TV camera 3 is is shown in Figure 3B.
As shown in FIG. 2, it becomes larger when light passes through it, and as the light shielding period passes, it becomes smaller as the afterimage due to light passing is almost eliminated.

Then, the output (i+
There is almost no possibility that the output of four frames will be disturbed by afterimages caused by the previous passing of light and errors will occur.

In this way, the signals extracted during the period (i and i+4 frame periods) shown in FIG. It is determined whether the direction of the scanning line and the direction of the scanning line match, and if they match, a responsive data signal is sent out.

In the above embodiment, the second light shielding plate 6 has a pair of light shielding part 61 and light passing part 62, but the angle of this light shielding part 61 and light passing part 62 is 1/m. By providing m sets of light shielding portions 61 and light passing portions 62 on one light shielding plate 6, the rotation speed of the light shielding plate 6 can be reduced to 1/m, and the reliability of the rotation mechanism can be improved.

In addition, in the above example, the case where the light shielding plate is mechanical was explained, but it is also possible to use an electronic light shielding plate made of liquid crystal and change the transparency by changing the voltage applied to the liquid crystal to control light blocking and light passing. You can also do this.

As described above, according to the present invention, signal detection is performed by blocking light from a barcode label for a certain period of time, so even if signal detection is performed while rotating the scanning plane, the influence of errors caused by afterimages is minimized. can be reduced to

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of a barcode label reading device according to the present invention, FIG. 2 is an enlarged view of a part of FIG. 1, and FIG. 3 is a diagram for explaining the operation of the device in FIG. 1. This is a time chart. 2 is a product placement stand, 3 is a television camera, 6 is a light shielding plate, 61 is a light shielding part, and 62 is a light transmitting part.

Claims (1)

[Claims] 1 A mounting means having a transparent part on which an object having a barcode label is placed, and a scanning surface rotated at a predetermined speed so that reading can be performed when the alignment direction of the barcode label and the scanning direction match, an imaging means for imaging the barcode label through the transparent portion; and an imaging means provided between the placement means and the imaging means, the optical path from the barcode label to the imaging means being synchronized with the rotational speed of the scanning surface. What is claimed is: 1. A barcode label reading device comprising: a light shielding means for removing light and blocking light at a predetermined period.