JP2939034B2 - How to read hologram information - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for mechanically reading information recorded in the form of a hologram, and more particularly to a method for reading hologram information which is less affected by scratches, dirt, etc. on the hologram surface.

[0002]

2. Description of the Related Art The applicant of the present invention has disclosed Japanese Patent Application No. 3-304522.
Japanese Patent Application No. Hei 3-327683 proposes reproducing a hologram on which a barcode pattern is recorded by applying a thin light beam to the hologram. When a hologram is reproduced by applying a thin light beam, the depth of focus of the reproduced image is increased, and therefore, the dependence of the resolution of the reproduced image on the detection position is reduced, which is advantageous in that the restriction on the installation position of the reading sensor is reduced. It is.

[0003]

However, in such a case where the reproduction light is a thin beam light beam, if the hologram surface in the irradiation area has dirt or scratches, the intensity of the diffracted light is reduced. When reading information recorded in the form of data by binarizing it at a certain slice level,
Read error is likely to occur.

The present invention has been made in view of such circumstances, and has as its object to read or record information by irradiating a hologram with a thin light beam and transmit or specularly reflect without being diffracted by the hologram. By detecting the zero-order light and detecting the intensity of the diffracted light while referring to the intensity, it is possible to eliminate the influence on the reading accuracy such as dirt and scratches on the hologram surface.

[0005]

According to the present invention, there is provided a method for reading hologram information which achieves the above object by photoelectrically reading recorded density pattern information of a single continuous Fresnel hologram on which density pattern information is recorded. So,
A method of photoelectrically reading density pattern information recorded on a hologram by illuminating a light beam having a cross section smaller than that of a hologram recording area while moving the light beam relatively to the hologram surface, and photoelectrically detecting diffracted light. At
The method is characterized by detecting the intensity of the zero-order light transmitted or specularly reflected without being diffracted by the hologram, and reading the information recorded on the hologram by detecting the intensity of the diffracted light with reference to the intensity.

In this case, the information recorded on the hologram can be read by dividing the diffracted light intensity signal by the zero-order light intensity signal. The information recorded on the hologram can be read by comparing the signal with the signal and determining that the information is recorded on the hologram when the intensity of the diffracted light intensity signal is larger by a predetermined factor.

[0007] Specifically, it is preferable that the recorded density pattern information is a pattern composed of a plurality of parallel bars, and is read in such a manner that the light beam moves in a direction intersecting each bar. In addition, such a hologram can be provided on a card so that it can be read.
In that case, the authenticity of the card can be determined based on the recorded information.

Further, it is also possible to simultaneously detect the punched holes formed in the hologram from the interruption time of the zero-order light.

[0009]

In the present invention, the information recorded on the hologram is read by detecting the intensity of the zero-order light transmitted or specularly reflected without being diffracted by the hologram and detecting the intensity of the diffracted light with reference to the intensity. Even if the intensity of the diffracted light decreases due to dirt or scratches in the illumination area of the hologram, the zero-order light intensity also decreases at the same rate as the diffracted light intensity. By detecting the light intensity, the decrease in the intensity of the diffracted light is compensated, and the density pattern information recorded on the Fresnel hologram can be accurately read.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for reading hologram information according to the present invention will be described below based on embodiments. FIG. 5 is a perspective view for explaining a method of reading a card provided with a bar code Fresnel hologram. A bar code Fresnel hologram 2 is attached to a stripe region of the card 1 and a hologram 2 surface is formed. Reproduced light beam 3
Is irradiated. The bar code pattern 6 whose bar is directed in the direction crossing the hologram stripe area 2 is reproduced by the diffracted light 5 from the minute irradiation area 4. When the reproduction light 3 is fixed and the card 1 is sent in the longitudinal direction of the stripe region 2, the reproduced barcode pattern 6 also moves in the same direction. As a result, a read signal as shown in FIG. 6 is obtained.

In this manner, the bar code recorded on the hologram 2 can be read. However, if the irradiation area 4 is dirty or has a dent, the intensity of the diffracted light 5 is reduced, and the signal Is smaller than the threshold value for determining that the bar code pattern 6 exists, and the bar code pattern 6 may not be accurately read. Therefore, in the present invention, the 0th-order light intensity that is transmitted or specularly reflected without being diffracted by the hologram is detected, and, for example, the ratio of the diffracted light intensity to the 0th-order light intensity is determined, and the ratio exceeds a predetermined value. At the time of the occurrence of the signal.

FIG. 1 is a diagram showing a configuration for carrying out a reading method according to one embodiment of the present invention. A Fresnel hologram 2 of a bar code is attached to a stripe area of a card 1, and FIG. In the same manner as described above, the reproduction beam 3 in the form of a thin beam is irradiated on the hologram 2 surface. The hologram stripe region 2 is formed by the diffracted light 5 from the minute irradiation region 4.
The bar code pattern 6 with the bar directed in the direction crossing the line is reproduced, but when the reproduction light 3 is fixed and the card 1 is sent in the longitudinal direction of the stripe area 2, the reproduced bar code pattern 6 also moves in the same direction. I do. A light receiving element 7 for signal reading is arranged at the reproduction position, and the bar code pattern 6 is read with the movement of the card 1. In addition to this, another light receiving element 9 for detecting the zero-order light is disposed at a position for detecting the zero-order light 8 in which the reproduction light 3 is not diffracted from the irradiation area 4 and is specularly reflected, and detects the zero-order light intensity I do. In this embodiment, a divider 10 is provided so as to divide the output signal from the light receiving element 7 by the output signal from the light receiving element 9.

When the reading circuit is configured as described above, the output signal from the light receiving element 7 for detecting the diffracted light 5 corresponds to, for example, as shown in FIG. There is a possibility that the recorded bar code pattern 6 cannot be accurately read by simply setting the threshold value. By the way, the output signal of the light receiving element 9 for detecting the zero-order light also decreases at the same rate at a position corresponding to dirt or the like as shown in FIG. When the signal from the light receiving element 7 (FIG. 2 (a)) is divided by the signal from the light receiving element 9 (FIG. 2 (b)) in the device 10, the signal drop due to dirt or the like is corrected and shown in FIG. Such a correct signal is obtained.

As a method of correcting a decrease in a read signal due to dirt or scratches on the read surface by using the 0th order light intensity,
The present invention is not limited to this embodiment, and various types can be considered. FIG. 3 shows the configuration of another embodiment. In this case, the comparator 11
And a diffracted light intensity signal (strictly, a signal obtained by multiplying the signal detected by the light receiving element 7 by a predetermined value. However, even if the magnification is 1 or more, it is 1 or less. The signal is obtained from the light receiving element 7 only when the value exceeds the value. Also in this case, as shown in FIG. 4, the signal level from the light receiving element 9 shown by the dotted line becomes the threshold, and the level is the same as that of the signal from the light receiving element 7 shown by the solid line at the position of dirt or the like. As a result, a correct signal as shown in FIG. 6 is obtained from the comparator 11.

By the way, according to such a reading method, when a punched hole is made in the hologram 2 area for displaying the frequency of the prepaid card, the punched hole can be detected simultaneously with reading the hologram information. Become. That is, if the hologram 2 is provided with the punched holes 12, the zero-order light 8 is not emitted for a certain period of time determined by the diameter of the punched holes 12. Therefore, by detecting this from the signal obtained from the light receiving element 9, The hole 12 can be recognized. It is to be noted that the distinction between the punch hole 12 and the scratches or dirt can be made by detecting the cutoff time of the signal obtained from the light receiving element 9.

Although the method of reading hologram information of the present invention has been described above by taking as an example the reading of a Fresnel hologram on which a barcode is recorded, the present invention records various digital and analog information other than such information. It can be applied to reading of a hologram that has been performed. Further, the present invention is not limited to the above embodiment, and various modifications are possible.
The information to be recorded on the hologram may be any type of information such as information for determining the authenticity of a card. Also, as a card to provide a hologram,
Various things such as a CD card, a prepaid card, and a commuter pass are possible.

[0017]

As is clear from the above description, according to the hologram information reading method of the present invention, the intensity of the zero-order light transmitted or specularly reflected without being diffracted by the hologram is detected, and the intensity is referred to. Because the information recorded on the hologram is read by detecting the intensity of the diffracted light, the intensity of the 0th-order light is the same as the intensity of the diffracted light even if the intensity of the diffracted light decreases due to dirt, scratches, etc. in the illumination area of the hologram. Therefore, by detecting the diffracted light intensity with reference to the reduced 0th-order light intensity, the decrease in the diffracted light intensity is compensated, and the density pattern information recorded on the Fresnel hologram can be accurately read. .

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration for implementing a reading method according to an embodiment of the present invention.

FIG. 2 is a waveform diagram of signals obtained from a diffracted light receiving element and a zero-order light receiving element.

FIG. 3 is a diagram illustrating a configuration for implementing a reading method according to another embodiment.

FIG. 4 is a diagram for explaining the operation of the configuration of FIG. 3;

FIG. 5 is a perspective view for explaining a method of reading a card provided with a Fresnel hologram of a barcode according to the above proposal.

FIG. 6 is a waveform diagram showing an example of a read signal according to FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Card 2 ... Hologram 3 ... Reproduction light 4 ... Irradiation area 5 ... Diffraction light 6 ... Reproduction pattern 7 ... Light receiving element 8 ... 0th order light 9 ... Light receiving element 10 ... Divider 11 ... Comparator 12 ... Punch hole

Claims (7)

(57) [Claims] 1. A continuous pattern on which density pattern information is recorded.
Lights the recording density pattern information of a single Fresnel hologram
In this method, a light beam whose cross section is smaller than that of the hologram recording area is illuminated while moving relatively to the hologram surface, and the hologram is recorded on the hologram by photoelectrically detecting the diffracted light. In the method of photoelectrically reading the density pattern information, the information recorded on the hologram is detected by detecting the intensity of the zero-order light transmitted or specularly reflected without being diffracted by the hologram and detecting the intensity of the diffracted light with reference to the intensity. A method for reading hologram information, comprising reading hologram information. 2. The hologram information reading method according to claim 1, wherein the information recorded on the hologram is read by dividing the diffracted light intensity signal by the zero-order light intensity signal. 3. A hologram is determined by comparing a predetermined-fold diffracted light intensity signal with a zero-order light intensity signal and determining that information is recorded on the hologram when the predetermined-fold diffracted light intensity signal is large. 2. The method for reading hologram information according to claim 1, wherein the recorded information is read. 4. The recorded density pattern information is a pattern comprising a plurality of parallel bars, and the moving direction of the light beam is a direction intersecting each bar. A method for reading hologram information according to claim 1. 5. The hologram information reading method according to claim 1, wherein the hologram is provided on a card. 6. The method according to claim 5, wherein the authenticity of the card is determined based on the recorded information. 7. The method for reading hologram information according to claim 1, wherein a punched hole formed in said hologram is simultaneously detected from a zero-order light blocking time.