JPS60156180A - Bar code reader - Google Patents

Abstract

PURPOSE:To attain a handy reader with low cost and excellent spectral characteristic while keeping the accuracy of identification by using an incandescent lamp as a light source and correcting the wavelength of a light reflected from a bar code at a cut-off filter. CONSTITUTION:A bar code pattern is formed on a photodiode array 7 from the luminous flux B' collected on a collecting means (concaved mirror) 5 and an output signal of the photodiode array 7 is fed to a detector. In such a case, the spectrum is the continuous spectrum because the incandescent lamp 2 is used for the light source, the identification of the bar width is not clear. Then the cut-off filter 6 (in transmission characteristic curve rises at the wavelength 400mm., >=70% of transmittivity is shown at wavelengths of 450-700mm., and falls to <=1% of transmittivity at wavelengths >=800mm.) is inserted in the optical path to correct the wavelength. The cut-off filter is provided just before the photodiode array 7.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a barcode reader that reads barcode symbols recorded on a recording medium, and in particular uses an incandescent lamp as a light source and a photodiode as a photoreceptor.
This invention relates to a handy barcode reader using an array.

In recent years, PO8 systems that automate product sales management have become popular, and as part of this system, various data such as product unit price, purchase price, and attributes are encoded in an array of bars, and the PO8 system is used to encode stickers, labels, etc. A barcode system is used in which the barcode is printed on a recording medium, affixed to the product, and the barcode is optically read and converted into an electrical signal. This barcode system is expressed as an array of ``pleasants'' to be displayed, and is encoded by a combination K of bar width and interval between these bars.There are various code systems including JAN code, but For example, in the JAN code, the basic unit of bar width is 0.33 mm, and the code content depends on whether the reading device can accurately identify this minute bar width.
It is determined whether or not it can be read correctly.

For this reason, conventionally, a laser has been used as the light for percodon irradiation, and the linearity and convergence of the laser have often been relied upon. However, when a laser Y is used, the device becomes bulky, expensive, inconvenient to carry, and has poor operability. There was an inconvenience that I had to have.

In response to this, various efforts have been made to miniaturize the reader device by using non-coherent general light as a light source, but barcodes with combinations other than black vs. sun, such as blue vs. white or green vs. white, have been devised. When the bar width is printed, the classification of the bar width is not clear, which causes a reading error.

The purpose of the present invention is to solve the above-mentioned problems, to be small and low-cost, easy to carry and handle, and to be able to irradiate the product at will without having to place the product in a specific position. Moreover,
The object of the present invention is to provide a handy and cost-effective barcode reader with excellent spectral characteristics and accurate identification.

In order to achieve the above object, the present invention uses an incandescent light bulb as a light source, corrects the wavelength of the reflected light from the barcode with a t-cut filter, and measures the light beam with a t-photodiode array. Features:

Hereinafter, the present invention will be explained in detail with reference to examples and drawings.

FIG. 1 is a sectional view showing an example of a barcode reader embodying the present invention, in which FIG. 1A is a plan view and FIG. 1B is a sectional view taken along line A-λ in FIG.

In the figure, the barcode reader includes a tungsten lamp 2 that emits one light inside a main body 1 integrally formed with a handle, a first plane mirror 3, a second plane mirror 4, and a concave mirror 5. It is constructed by arranging a cut filter 6 and a photodiode array 1. A tungsten lamp, which is a mini-sized incandescent light bulb, is used as a general light source for illuminating the barcode number pattern. K to cover the entire area of pattern 10, main body 1
Corresponding to the fact that the lamp has a rectangular shape whose longitudinal direction is at an angle to the handle axis, a plurality of tungsten lamps 2 are also arranged in the longitudinal direction. The general light emitted from the incandescent lamp source is reflected by the printed barcode pattern IOI'C on the recording medium and enters the main body 1 again through the window 8. This reflected light B sets a return optical path by the first plane mirror 3 and the second plane mirror 4, and reaches the concave mirror 5, which is the third reflecting mirror.゛Do the two plane mirrors above reflect the optical path or cover the entire barcode reader? It is used for miniaturization. The concave mirror 5 is a reflecting mirror that folds back the optical path, and at the same time, it is also a condensing means that condenses the reflected light reflected by the parcordon into a luminous flux having a thickness corresponding to the photo diode array. Here, the reason why a concave mirror is used as a condensing means instead of using the lens Y is as follows:
One is that the optical system is shortened accordingly, and the other is that using lenses causes chromatic aberration and blurs the image. Now, the light beam B' condensed by the concave mirror 5 is a photo.
A barcode pattern is imaged on the diode 9 array 7, and the output signal of this photodiode array is ? However, since the light source is an incandescent bulb and it is a continuous light source, it is difficult to clearly identify the bar width. The cut filter can be inserted at any position on the optical path after entering the main body, but in this example, the cut filter is inserted into the filter where the correction effect is most directly applied.
A diode O array of 70 liters is installed in front of FtK.

When an incandescent light bulb is used as a light source and a photodiode array is used as a photoreceptor, wavelength correction by inserting a cut filter is technically the most important feature of the present invention. Therefore, a more detailed explanation will be given below with reference to the drawings.

FIG. 2 is an explanatory diagram showing a side lighting method of a barcode pattern. Figure (A) shows an example of a barcode pattern. The basic unit for one bar width is 0.33rm1, and the first two ◎ in the scanning direction are set as the opening code. One string of bows (7 pieces ■~■ are assigned to the '# information code. In the example shown in the figure, ■, ■, ■
and ■ are white information, and ■, ■, and ■ are black information. Visually, the white information portion appears as a bar interval, ■ is a thin bar, and ■ and ■ are two thick bars. When photometering with a laser, the light beam is a beam, so the irradiated light spot also becomes a minute spot.As shown in Figure (B), the light spot L-& is scanned in a direction perpendicular to the bar of the barcode. The reflected light can be detected by a single light-receiving element.1) Light blurring can be used to read the bulletin regardless of the presence or absence of reflection or its size, but if the light source is an incandescent light bulb, it is continuous light, so the entire barcode pattern can be photographed. The image is formed on a diode array, and as shown in Figure (c), for example, five pendulums F1 to F5'r are assigned to the width of one bar, and each of these elements measures light, resulting in Y li' 1→ Reading IC7,C by self-scanning of the serial array of F5. What is important in this case is that the data measured by the final element J'5 that measures the white information part ■ must clearly be white information, and the data measured by the final element J'5 that measures the white information part ■w m:1 must be element j
It is a seemingly ordinary principle that the data measured by No. 1 must be clearly black information.

However, when the barcode pattern is printed in pure white versus black (as well as white versus blue or white versus green, which is also allowed in the JAN code), the light energy busy photo carrier is added, The difference in light amount between the two elements f5 and 11 becomes unclear.

FIG. 3 is a graph showing the reflectance characteristics of light for each color in order to explain the above problem. In the figure, the horizontal axis of the graph 27 indicates the wavelength of the irradiated light, and the vertical axis of the graph indicates the spectral characteristic Y of the light reflected from each color printed on the label.
It is expressed as a percentage based on the white reflectance of 100%.

As shown in the figure, the reflectance for white is constant at 100% at any wavelength, and for black it is approximately constant at less than 45%, so the barcode pattern is printed white to black.1.7 E4.2. Ioh 1.8
+. , 11ka, -2( are not confused. However, for blue and green, the spectral characteristic curve is at wavelength 80
At 0rrrn or more, the reflectance is almost equal to or higher than that of white. This is because there is near-infrared light near the upper limit of visible light, and when this light energy is photoelectrically converted by an optical diode, white becomes blue.

It becomes impossible to distinguish between white and opposite edges. In particular, the sensitivity characteristics of the 7-diode array show a peak at a wavelength of 750 rrm, and since it is thicker on the long wavelength side, it absorbs a large amount of near-infrared light, causing confusion. Also, if the photometric standard is set to 100% of white, there may be cases where current leaks to adjacent bits of the photodiode array due to the energy of near-infrared light, such as when blue exceeds 100%. Occur. In order to prevent these damage Z, in the present invention, a cut filter is inserted on the optical path.

Figure 4 shows how the present invention is put into practice. 1 is a graph showing a transmission characteristic curve of an example of a cut filter suitable for filtering. In the figure, the horizontal axis of the graph represents the wavelength of transmitted light, and the vertical axis represents the percentage of the amount of light on the transmittance Y side. As shown in the figure, the transmission characteristic curve rises at a wavelength of 400 mn and rises at a wavelength of 450 mn.
It exhibits a transmittance of 70% or more at ~700 rrm, and the transmittance drops to below 1% at wavelengths of 8001'rIT1 or more.
In the optical path in front of the diode play (11 people are
The reflected light with the reflectance characteristics shown in Figure 83 also has a wavelength of 450.
Since only the wavelength range of ~700mm is transmitted, the amount of light emitted by each photodiode element differs depending on the color, even when white versus blue or white versus edge.Barcode pattern? Can be clearly identified.

As explained above, according to the present invention, an incandescent light bulb is used as a light source? A compact, low-cost, easy-to-carry and handle barcode reader that uses a photo die and an ordnance array in the light receiving section has been developed. A cut filter that lets it pass through? By inserting it into the optical path, it is possible to accurately identify the barcode pattern, which greatly contributes to the cost performance of the P08 system.

[Brief explanation of the drawing]

Figure 1 shows a cross section 1 of a barcode reader implementing the present invention.
, FIG. 2 is an explanatory diagram of the barcode pattern side light method, FIG. 3 is a reflection characteristic curve diagram of reflected light, and FIG. 4 is a transmission characteristic curve diagram of the cut filter of this embodiment. DESCRIPTION OF SYMBOLS 1... Main body, 2... Incandescent light bulb, 3 and 4... Plane mirror, 5... Light condensing means, 6... Cut fist filter,
7... Photo diode array, 8... Window, 1
0...Recording medium, B and B'...Reflected light, L...
-Laser spot, F1-F5...photo-diode element. Figure 1 Figure 2 (a)

Claims (1)

[Claims] In a barcode reader that irradiates light onto a barcode recorded on a recording medium and converts the reflected light into electricity to read the barcode, one or more incandescent light bulbs as a light source for irradiating the barcode and the barcode are used. It consists of a cut filter that transmits only a predetermined wavelength range of light reflected from A barcode reader with several features.