JPH0896060A - Output correction method for bar code verifier - Google Patents

Abstract

PURPOSE: To eliminate the deterioration of accuracy of a bar code verifier that is caused by the uneven light emision of a light source by reading previous ly the beams reflected on both white and black reference plates with a scanner and correcting each pixel of the scanner by a specific calculation expression. CONSTITUTION: A scanner 2 is set opposite to a white reference plate 5 and the white reflection output Rw received from each pixel of a sensor 2b is stored in an analyzing computer. Then, the scanner 2 is set opposite to a black reference plate and the black reflection output Rb received from each pixel of the sensor 2b is stored in the analyzing computer. The analyzing computer calculates a genuine reflectivity factor (= BR+(WR-BR)×Rt), where BR and WR show the black and white reference plate reflectivities respectively, and corrects each pixel of the sensor 2b by an expression, i.e., a genuine reflectivity factor of a bar code Rt= (RX-Rb)/(Rw-Rb)}×100 (%). Thus, the genuine reflection output is calculated for the bar code set at a position corresponding to a relevant pixel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bar code described on a product for the purpose of displaying a product name, for example, a bar code for verifying whether or not the bar code is correctly described. It relates to a code verifier.

[0002]

2. Description of the Related Art Conventional bar code verifiers include, for example, a pen type and a laser type. In these devices, a photo sensor consisting of dots is moved along a barcode, and the image of the entire barcode is obtained as a signal by this movement. The advantage of this type is that you can always illuminate the barcode with a constant illuminance,
Alternatively, it is possible to obtain a signal from a photosensor under the same conditions. However, since this type has a movable mechanism for moving the photosensor, the mechanism is complicated and there is a problem in reliability. Therefore, as a verification device using a line sensor,
For example, there is a bar code verifier 90 shown in FIG. The bar code verifier 90 is roughly classified into a scanner 91 and an analysis computer 92 such as a personal computer.
The scanner 91 shown in FIG.
As shown in FIG. 4, a light source 91a by an LED and a sensor 91b for recognizing a shape by an output waveform by scanning such as a CCD element are provided. By analyzing an output waveform from the scanner 91 with an analysis computer 92, a predetermined base is obtained. The barcode 80 having the bar portion 82 and the space portion 83 formed on the surface of the material 81 is determined by printing or the like.

[0003]

However, in the above-described conventional bar code verifier 90, if the light source 91a has uneven light distribution and the entire surface of the bar code 80 is not illuminated with uniform illuminance. , The output Ro from the sensor 91b varies, and the sensitivity of each pixel forming the sensor 91b also varies, and the lens 91c is used to form an image on the sensor 91b. Therefore, due to the cosine fourth law of the lens, it becomes darker from the center to the periphery, causing a bend as shown in FIG. 8, and measurement of reflectance, contrast, etc. for the purpose of verification becomes uncertain, This causes a problem that the verification accuracy decreases.

No matter how the light source 91a is an LED, which is said to have a semi-permanent life, it is inevitable that the illuminance will change due to changes over time, and each pixel of the CCD will also be affected. There is also a variation in sensitivity, and for these reasons also the measurement of the reflectance of the bar code 80 becomes uncertain, and there arises a problem that the verification accuracy decreases, and the solution of these points becomes an issue. ing.

[0005]

As a concrete means for solving the above-mentioned conventional problems, the present invention provides a method for verifying a bar code from the output of reflected light from the bar and the space of the bar code. , The reflected light from the white reference plate and the black reference plate having a known reflectance is read in advance by a scanner, the reflected light from the bar code is further read, and the white reflection output Rw of the white reference plate is obtained. From the black reflection output Rb of the black reference plate and the sample reflection output Rx of the barcode, the true reflectance coefficient Rt of the barcode is Rt =
By providing an output correction method for a barcode verifier characterized by performing correction for each pixel of the scanner by a calculation formula of {(Rx−Rb) / (Rw−Rb)} × 100 (%), It is intended to solve the above-mentioned conventional problems by solving the deterioration of accuracy caused by the uneven light distribution of the light source.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail based on an embodiment shown in the drawings. Reference numeral 1 in FIG. 1 is a bar code verifier according to the present invention.
Is basically composed of a scanner 2 and an analysis computer 3, and is attached with a flexible desk 4 storing a program for functioning as the analysis computer 3 and the like. The point that the barcode 10 formed by printing or the like is tested is the same as the conventional example.

Further, as shown in FIG. 2, the scanner 2 has a light source 2a formed of an LED and a sensor 2 formed of a CCD element.
b is provided, and the bar code 10 is illuminated by the light source 2a, and the bar code 10 is verified by outputs from a plurality of pixels provided in the sensor 2b. Is the same as.

In the present invention, in addition to the above, a white reference plate 5 and a black reference plate 6 are prepared. At this time, the white reference plate 5 is, for example, a flat surface formed of magnesium oxide, The black reference plate 6 is a matte black coated surface or a black velvet surface, and both reference plates 5 and 6 have a uniform reflectance and are known.

Next, an output correction method by the barcode verifier 1 of the present invention having the above-mentioned structure will be described.
In the present invention, prior to the verification of the barcode 10, the scanner 2 is opposed to the white reference plate 5 (see FIG. 2), and the white reflection output Rw from each pixel of the sensor 2b is held in the analysis computer 3. Then, the scanner 2 is made to face the black reference plate 6, and the black reflection output Rb from each pixel of the sensor 2b is held in the analysis computer 3.

FIG. 3 is a graph of the white reflection output Rw from the white reference plate 5 and the black reflection output Rb from the black reference plate 6 obtained by the above procedure, and as described above. Since both the white reference plate 5 and the black reference plate 6 have a uniform reflectance over the entire surface, there is no illumination unevenness in the light source 2a and there is no difference in sensitivity between the pixels of the sensor 2b. Both the white reflection output Rw and the black reflection output Rb are constant, and should be horizontal straight lines on the graph.

However, in reality, as shown in the figure, both the white reflection output Rw from the white reference plate 5 and the black reflection output Rb from the black reference plate 6 have curved output potentials,
A closer examination will show that the output of the light source 2a or the sensor 2b fluctuates due to environmental conditions such as the ambient temperature when the above-mentioned measurement is performed, or changes over time. As indicated by -d, the output level is moved in parallel with each measurement, and the curved or translated numerical values are held in the analysis computer 3.

After the above preparatory work has been carried out, in the present invention, the bar code 10 for the purpose of verification is confronted with the scanner 2, and the sample reflection output Rx from the sensor 2b is sent to the analysis computer 3 and A white reflection output Rw from the white reference plate 5 having the same sample reflection output Rx,
The comparison for each pixel is performed like the black reflection output Rb by the black reference plate 6 of the same pixel.

At this time, the reflectance of the white reflection output Rw is known (for example, 99%) regardless of the potential.
Is the output from the white reference plate 5, and the black reflection output Rb is also the output from the black reference plate 6 having a known reflectance (for example, 1%). Therefore, the sample reflection output Rx is the white reflection output Rw. The true reflection output Rt of the bar code 10 is calculated as a calculated value by calculating which position between the black reflection output Rb and the black reflection output Rb is present, without being influenced by the curvature of the output potential due to the uneven illumination. 3 is required.

That is, in the analyzing computer 3, for each pixel of the sensor 2b, the bar code true reflectance coefficient Rt = {(Rx-Rb) / (Rw-Rb)} * 100.
True reflectance = BR + (WR-BR) according to the formula (%)
The true reflection output of the bar code 10 at the position corresponding to the pixel is calculated by performing the correction of × Rt (BR: black reference plate reflectance (known), WR: white reference plate reflectance (known)). It will be required. Therefore, the analysis computer 3 can obtain extremely accurate results by performing various analyzes based on the true reflection output.

FIG. 4 shows an essential part of another embodiment of the present invention. In the previous embodiment, the white reference plate 5 and the black reference plate 6 are prepared, and the substantially upper limit value of the output from the sensor 2b is set. However, in this embodiment, in addition to the white reference plate 5 and the black reference plate 6, for example, the reflectance is set to 5
A gray reference plate 7 having 0% is provided.

By doing so, the output from the sensor 2b is approximately the upper limit value due to the white reflection output Rw from the white reference plate 5 and the black reflection output Rb from the black reference plate 6 as shown in FIG. The correction is made at three points, that is, a substantially lower limit value and a substantially intermediate value by the gray reflection output Rg from the gray reference plate 7.

Therefore, for example, even when the output characteristic of the sensor 2b has non-linearity, the correction can be performed more accurately. At this time, when the gray reference plate 7 is provided for the above purpose, that is, for the purpose of correcting the non-linearity, the reflectance is not limited to 50%. For example, when the sensor 2b is on the low output side. When the non-linearity is remarkable, the reflectance may be set to the most appropriate reflectance for achieving the purpose, such as the reflectance is low.

The correction using the gray reference plate enables accurate verification of the low-contrast bar code, and
It is expected that color-coded barcodes will appear in the future, and in this case, when verifying the barcode 10, it is considered that more accurate intermediate reflectance measurement is required than in the present case. Therefore, in such a case, the gray reference plate 7 may be set to have a reflectance in the vicinity where accurate measurement is required. Therefore, if there are two reflectances for which accurate measurement is required, it is sufficient to prepare two types of the gray reference plate 7.

[0019]

As described above, according to the present invention, a white reference plate having a known reflectance is prepared when the bar code is verified from the output of the reflected light from the bar and the space of the bar code. The reflected light from the black reference plate is read in advance by a scanner, and the reflected light from the bar code is further read, and the white reflected output Rw of the white reference plate, the black reflected output Rb of the black reference plate, and the bar code are read. From the sample reflection output Rx of Rt = {(Rx−Rb) / (Rw−Rb)} × 100
A bar code for correcting the true reflectance = BR + (WR−BR) × Rt (BR: reflectance of black reference plate, WR: reflectance of white reference plate) for each pixel of the scanner by the calculation formula (%). By using the output correction method of the verification device, the unevenness of the local output characteristics caused by uneven light distribution of the light source, etc. will be eliminated first, and originally it will not be involved in the barcode verification content. It is possible to prevent the verification accuracy from being deteriorated due to a non-reliable factor, and to achieve an extremely excellent effect in improving the verification accuracy of this type of barcode.

Secondly, since the white reference plate and the black reference plate are referred to before the verification of the bar code, for example, the parallel movement of the output characteristic caused by the aging of the light source or the like. Is also corrected, thereby improving the reliability of the verification device and also improving the durability.

Thirdly, by using a gray reference plate in addition to the white reference plate and the black reference plate, it is possible to measure a bar code formed by color printing, especially in an intermediate reflectance. Even when accuracy is required, the accuracy is increased by referring to the output from the gray reference plate, and the verification accuracy is further improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of an output correction method for a bar code verifier according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a graph showing an example of output waveforms of the same embodiment.

FIG. 4 is a perspective view showing another embodiment of the output correcting method of the bar code verifying device according to the present invention.

FIG. 5 is a graph showing an example of an output waveform of another embodiment.

FIG. 6 is a perspective view showing a conventional example.

7 is a cross-sectional view taken along the line BB of FIG.

FIG. 8 is a graph showing an example of an output waveform of a conventional example.

[Explanation of symbols]

 1 ... Bar code verifier 2 ... Scanner 2a ... Light source 2b ... Sensor 3 ... Analysis computer 4 ... Flexible desk 5 ... White reference plate 6 ... Black reference plate 7 ... Gray reference plate 10 ... … Bar code Rw …… White reflection output Rb …… Black reflection output Rg …… Gray reflection output Rx …… Sample reflection output Rt …… True reflection output

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yoshiki Furukawa 2-8-7 Kumamatsu, Hadano City, Kanagawa Prefecture (72) Inventor Naoki Matsumura 11-37, Midoricho, Hadano City, Kanagawa Prefecture

Claims (2)

[Claims] 1. A reflected light from a white reference plate and a black reference plate, each of which has a known reflectance, is prepared in advance when the bar code is verified from the output of the reflected light from the bar and the space of the bar code. The scanner reads the reflected light from the bar code, and the white reference output Rw of the white reference plate and the black reflection output Rb of the black reference plate are read.
And the sample reflection output Rx of the barcode, the true reflectance coefficient Rt = {(Rx-Rb) / (Rw of the barcode.
-Rb)} × 100 (%) is used to perform correction for each pixel of the scanner, and an output correction method for a barcode verifier. 2. The bar code verifying device according to claim 1, wherein the correction is also performed on a gray reference plate having a reflectance between the white reference plate and the black reference plate. Output correction method.