JP3911685B2 - Machine recognition optical code - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a machine recognition optical code, and more particularly, to a machine recognition optical code using a light diffraction effect such as a diffraction grating and a hologram as one of an authentication code or an optical recording method for preventing forgery.
[0002]
[Prior art]
Conventional techniques include a method that uses the direction in which an optical diffraction image of a diffraction grating appears as an optical code, a method that records interference fringes of object light and reference light transmitted through a transmission original provided with a barcode as a Fresnel hologram, and the like. is there.
[0003]
[Problems to be solved by the invention]
Conventionally, the optical code reading method using the light diffraction effect is generated from the contrast on the light receiving element between the bright spot and the dark spot of the received bar by photoelectrically converting the light diffraction pattern by the light receiving element. The bar position of the light diffraction pattern is detected by analyzing the voltage difference and detecting the peak of the bright spot and the dark spot.
[0004]
On the other hand, when the voltage difference obtained from the contrast exceeds a certain threshold value, a method of binarizing by determining the presence position of the bar and turning it OFF otherwise can be considered. Since it changes greatly due to subtle changes in diffracted light due to the luminance stability of the laser light source, the conveyance speed of the medium, the warp of the medium, etc., it is possible to prevent misreading more by using the peak detection method. This method is used.
[0005]
However, in the peak detection method, only the potential difference between the bright spot / dark spot peak position and the peak is used as information, so the position of the light diffraction image position is not affected by the variation in brightness between the light diffraction bars due to the warping or waviness of the diffraction image. Compared to the binarization method that uses thresholds, the probability of simultaneous detection of disturbance light such as device white noise and diffracted light from holograms and diffraction grating patterns around the barcode part is detected as a signal. And misreading was likely to occur due to this.
[0006]
The present invention has been made in view of such problems of the prior art, and an object thereof is a machine recognition optical code that can be reproduced by diffracted light from a diffraction grating or a hologram, and prevents erroneous reading due to noise. It is to provide a machine recognition optical code.
[0007]
[Means for Solving the Problems]
The machine recognition optical code of the present invention is a machine recognition optical code that can be reproduced by diffracted light from a diffraction grating or a hologram, and reproduces a bar with a specific number of diffracted lights set in advance in a region aligned at equal intervals at a reading position. The machine-recognition optical code is reproduced and the start and end bars are reproduced by two diffracted lights in both ends of the N + 2 (N is a positive integer) region provided at equal intervals at the reading position. A bar formed by diffracted light is reproduced in m areas (m is a positive integer of m <N) between the bar and the end bar, and is not reproduced in Nm areas. Different codes are expressed by the difference between the two.
[0009]
In this case, it is desirable to make the peak intensity of the start bar and end bar larger than the peak intensity of other bars.
[0010]
Also, by confirming that the number of bars by the diffracted light detected at the reading position is m + 2 including the start bar, end bar, and m bars between them, the machine recognition optical code It is desirable that true / false can be determined.
[0011]
In the present invention, it is desirable to reproduce a predetermined number of diffracted light bars in a region aligned at equal intervals at the reading position, so that it is easy to judge reading errors, check the authenticity of codes, etc. And can be read without noise. In addition, the sensor density of the detector can be reduced, and the detection speed can be increased.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The principle and examples of the machine recognition optical code of the present invention will be described below.
As described above, the peak detection method can minimize the influence of the quality of the diffraction grating or hologram on which the code is recorded or the quality of the base material, but it cannot prevent the noise misreading. there were.
[0013]
In order to solve this problem, the following rules have been devised as a method for ensuring detection on the code side and incorporating reliable means of parity check in the code system.
[0014]
(1) The presence / absence of a light diffraction bar in a region aligned at equal intervals is detected. Since the light diffraction bar is reproduced only in a region set at equal intervals, the sensor density of the detector can be reduced, and the detection speed can be increased. Moreover, white noise is not detected by reducing the sensor density.
[0015]
(2) Provide both start and end bars at both ends of the area. In addition, an area where the bar exists is determined in N areas provided at equal intervals between both the start bar and the end bar. By doing so, the light diffraction bar is detected only in a region where the interval between the start bar and the end bar is equally divided by N. Therefore, when a light diffraction bar is detected in a region that is greatly deviated from the center of the region, it is possible to determine a reading error.
[0016]
{Circle around (3)} Of the N areas, bars are set in m areas and not in N−m areas, and different codes are represented by differences in the m areas. Therefore, if there are light diffraction bars in more than m areas, the light diffraction bar image contains noise.
[0017]
(4) In the detector, the authenticity of this code is confirmed by confirming that the number of detected light diffraction bars is m + 2 including the start bar and end bar added to the m bars. It is possible to confirm m signal portions.
[0018]
Hereinafter, examples of the machine recognition optical code of the present invention satisfying such requirements will be described. FIG. 1 is a diagram showing a code table of the optical code of this embodiment, and the left column (number surrounded by ◯) is the number to be encoded. The numbers 1 to 8 in the upper row represent eight areas arranged at equal intervals. Among them, 1 represents a start area S and 8 represents an end area E. In addition, six regions (N) from 2 to 7 are signal regions, and in this example, a bar due to diffracted light is present in four regions (m) in the six signal regions (bars of the bars). Existence is represented by “1” and non-existence is represented by “0”.) The code table as shown in FIG. 1 is completed, and a total of 15 different codes (numbers 1 to 15 surrounded by circles) can be assigned. it can.
[0019]
FIG. 2 is a diagram showing a light diffraction bar pattern (FIG. (A)) of a code representing, for example, the number (3) in the code table of FIG. 1 and a diffracted light intensity distribution (FIG. (B)) when it is read. It is. The light diffraction bars are present in the first 1 (S) and last 8 (E) of the eight regions 1 to 8 that are equally spaced, and in the two, three, six, and seven regions between them. However, it does not exist in the areas 4 and 5.
[0020]
In the case of FIG. 2, the intensity of diffracted light at the peaks of the start bar S and end bar E is the same as that of the signal bars in the regions 2, 3, 6, and 7, but as shown in FIG. If the peak intensity of the end bar E is larger than the peak intensity of the signal bars in the regions 2, 3, 6, and 7, the code can be recognized more reliably.
[0021]
Now, in order to record such an optical code as a Fresnel hologram, as shown in FIG. 4, it is aligned at equal intervals according to the code table of FIG. 1, and the start bar area, end bar area, and between them are arranged. A mask plate 10 having a signal bar region of “1” provided as a slit-shaped opening is prepared. For example, the mask plate 10 is arranged facing a hologram photosensitive material 11 made of a photoresist, and the diffusion plate 12 is interposed. Then, the mask plate 10 may be illuminated with the illumination light 13, and the object light 14 and the reference light 15 that have passed through the opening of the mask plate 10 may interfere with each other in the hologram photosensitive material 11 to be recorded and developed. Since the relief hologram recorded in this way is a transmission type, a reflection layer is provided on the relief surface for the reflection type hologram.
[0022]
In order to read the bar pattern provided by the mask plate 10 from the hologram thus recorded, a line sensor such as a CCD or an image sensor is arranged at the position where the mask plate 10 is arranged, and reproduction corresponding to the reference light 15 is performed. When the hologram is irradiated with illumination light and the diffracted light incident on the line sensor or image sensor is photoelectrically converted, a signal waveform as shown in FIG. 2A is obtained. A code recorded as a Fresnel hologram can be read by reading peak signals at equally spaced positions corresponding to the signal regions 1 to 8.
[0023]
In this case, as shown in FIG. 3, in order to make the peak intensity of the start bar S and end bar E of the recorded code larger than the peak intensity of the signal bars in the regions 2 to 7, as shown in FIG. The transmittance of the slit-shaped opening 22 corresponding to 10 signal bars may be made smaller than the transmittance of the slit-shaped opening 21 corresponding to the start bar and the end bar. For this purpose, for example, the slit-shaped opening 21 may be a completely transparent opening, and the slit-shaped opening 22 may be provided with a halftone dot or the like so as to have a transmittance of, for example, 50% smaller than 100%.
[0024]
Further, in order to record the optical code as described above as a diffraction grating, as shown in FIG. 6, elongated bar-like regions 23 arranged at equal intervals according to the code table of FIG. For example, a relief-type and reflection-type diffraction grating 25 having the same grating interval in the same direction is provided in an elongated bar-like region 24 representing a signal bar of “1” between them. In this case, for example, reading is performed from the diffraction grating 25 by sequentially irradiating the regions 23 and 24 with a monochromatic beam from a predetermined direction while moving a medium on which such an optical code is recorded in a direction orthogonal to the regions 23 and 24. The light receiving elements may be arranged in the diffraction direction, and a signal as shown in FIG. 2B or FIG. 3 may be obtained as a temporal signal waveform.
[0025]
When the optical code of the present invention is recorded as the diffraction grating as described above, a dummy diffraction grating may be provided around the regions 23 and 24 as shown in Japanese Patent Application No. 4-329232. It is.
[0026]
As one specific example, the optical code according to the present invention was recorded as a reflection-type and relief-type Fresnel hologram so that bars were reproduced at equal intervals of 5 mm, and a diffraction pattern was obtained by irradiation with 650 nm red laser light. However, six light diffraction bars were obtained at intervals of 5 mm and 10 mm in the area of the sensor having a width of 40 mm (in the case of numerals 6 to 15). Although there was a slight voltage difference variation in each peak output, noise was generated extremely low at positions that were not equally spaced, so that the code could be read normally without detecting this as a peak.
[0027]
The principle and examples of the machine recognition optical code of the present invention have been described above. However, the present invention is not limited to these examples, and various modifications can be made. Also, the format for recording such an optical code is not limited to the relief type, and may be a volume type in either case of a hologram or a diffraction grating. Moreover, even if such a hologram or diffraction grating is superposed on a hologram or diffraction grating on which such an optical code is recorded, it is easy to read the optical code of the present invention. These other holograms, diffraction gratings, and diffracted light due to printed patterns are not misread.
[0028]
【The invention's effect】
As is apparent from the above description, according to the machine recognition optical code of the present invention, a predetermined number of diffracted light bars are reproduced in a region aligned at equal intervals at the reading position. Judgment of reading error, confirmation of authenticity of code, etc. can be easily performed, and there is no erroneous reading due to noise. In addition, the sensor density of the detector can be reduced, and the detection speed can be increased.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a code table of a machine recognition optical code according to one embodiment of the present invention.
FIG. 2 is a diagram showing a light diffraction bar pattern of a code representing a specific numeral in the code table of FIG. 1 and a diffracted light intensity distribution when the code is read.
FIG. 3 is a diagram illustrating a diffracted light intensity distribution of a read signal according to a modification.
FIG. 4 is a diagram showing an arrangement for recording the optical code of the present invention as a Fresnel hologram.
FIG. 5 is a plan view showing a mask plate used when recording an optical code of a modified example as a Fresnel hologram.
FIG. 6 is a plan view of an example of an optical code of the present invention recorded as a diffraction grating.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Mask plate 11 ... Hologram photosensitive material 12 ... Diffusing plate 13 ... Illumination light 14 ... Object light 15 ... Reference light 21 ... Slit-like opening 22 corresponding to a start bar and an end bar ... Slit-like opening 23 corresponding to a signal bar ... Start Elongated bar-like region 24 representing bar and end bar ... Elongated bar-like region 25 representing signal bar ... Diffraction grating

Claims (3)

In a machine recognition optical code that can be reproduced by diffracted light from a diffraction grating or a hologram, a machine recognition optical code that reproduces a predetermined number of diffracted light bars in a region aligned at equal intervals at a reading position, Among the N + 2 regions (N is a positive integer) provided at equal intervals at the reading position, the start and end bars by the two diffracted lights are reproduced in both end regions, and m (m between the start bar and end bar is reproduced. Is a positive integer of m <N), and the bar due to the diffracted light is reproduced in the number of areas, and is not reproduced in the number N−m areas, and different codes are expressed by the difference in the number m areas. A machine-recognized optical code. The machine recognition optical code according to claim 1 , wherein the peak intensity of the start bar and end bar is larger than the peak intensity of other bars. In claim 1 or 2 , by confirming that the number of bars by the diffracted light detected at the reading position is m + 2 including a start bar, an end bar, and m bars therebetween, A machine-recognizing optical code, wherein the authenticity of the machine-recognizing optical code can be determined.

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