CN100417934C - Anti-counterfeit holographic product characteristic parameter detection method and detector - Google Patents

Abstract

The present invention relates to a detection method and a detector for detecting the characteristic parameters of anti-counterfeiting holographic products. The detection method uses a displacement mechanism to drive a sample platform to carry out one-dimensional displacement, so that anti-counterfeiting holographic samples to be measured can move relatively to the incident light spots of a laser, and the marks of anti-counterfeiting holographic products can be automatically scanned in a one-dimensional mode. In the process of scanning, a photoelectric detector obtains multipoint light intensity signals in scanning direction in real time, the collection of the light intensity signals is controlled by a computer or a microprocessor, the collected row of data is analyzed and processed after preprocessed by software so as to measured the characteristic parameters such as signal-to-noise ratio and diffraction efficiency, and the measuring results are displayed and printed. The detector comprises a light source, the sample platform, the displacement mechanism, a photoelectricity receiving device, data acquisition and control module. The present invention changes the problems of excess adjustment and incapability of automatic measurement, and the design of the detector realizes automatic measurement, so that the measurement process is simple and fast with high operability, and the requirement of professional knowledge toward an operator is lowered.

Description

Anti-counterfeit holographic product characteristic parameter detection method and detector

【Technical field】：

The invention relates to the field of quality detection of anti-counterfeiting holographic products, in particular to a detection method and a detection device for its characteristic parameters: signal-to-noise ratio and diffraction efficiency.

【Background technique】:

Anti-counterfeiting holographic products are safe and anti-counterfeiting products based on laser holographic plate-making technology, and are often made into anti-counterfeiting marks for product safety and anti-counterfeiting. The quality of anti-counterfeiting holographic products should meet certain requirements to achieve the purpose of anti-counterfeiting. Anti-counterfeit holographic product characteristic parameter detection method is applied to detect anti-counterfeit holographic product characteristic parameter indicators: signal-to-noise ratio and diffraction efficiency, to achieve the purpose of monitoring the quality of holographic anti-counterfeit label products, and to implement the "General Technology for Anti-counterfeit Holographic Products" for technical supervision departments and manufacturers "National standards provide quantitative testing methods.

The detection principle is to calculate the signal-to-noise ratio and diffraction efficiency characteristic parameters of the anti-counterfeiting mark by measuring the signal light intensity and noise light intensity in the diffraction pattern of the rainbow hologram slit image, as well as the light intensity of the laser light source.

First measure the light intensity at the position of the holographic grating on the mark as the signal light intensity I _S , then measure the light intensity of the part without the grating structure on the mark as the noise light intensity I _N , and the light intensity of the collected light source is I ₀ , using The following two formulas can calculate the signal-to-noise ratio SNR and diffraction efficiency η

$\mathrm{<span\; class="notranslate">\; SNR</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; N</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

$\mathrm{<span\; class="notranslate">\; \&eta;</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; \%</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

In the past, the measurement of the characteristic parameters of anti-counterfeiting holographic products was often carried out by means of visual inspection by personnel, or with measurement devices, but only for a certain point of characteristic parameters. At the same time, there are too many adjustment links during the measurement, and the measurement is more cumbersome. When collecting signal light intensity and noise light intensity, it needs to be adjusted before the data can be read and recorded, and the signal-to-noise ratio and diffraction efficiency can be calculated through the formula.

【Invention content】：

The purpose of the present invention is to solve the shortcomings of the above methods, and provide a detection method and detector for characteristic parameters of anti-counterfeit holographic products that can realize the function of one-dimensional automatic scanning of anti-counterfeit holographic product marks.

The method for detecting the characteristic parameters of anti-counterfeit holographic products provided by the present invention includes in sequence:

——Place the tested anti-counterfeit holographic sample on the sample platform and fix it;

——Let the light beam emitted by the light source enter the anti-counterfeiting holographic sample along the angle θ with the sample normal, and the θ angle is 30°-60°;

——Place a concave reflector in the direction of the sample normal N, the normal M of the concave reflector and the sample normal N form an included angle ψ, ψ is 10°±2°;

——Let the sample platform drive the tested anti-counterfeiting holographic sample to perform one-dimensional displacement movement along the direction perpendicular to the normal line of the sample;

——Place the photodetector on the other side of the concave mirror, and acquire multi-point light intensity signals in the scanning direction in real time;

——Send the light intensity signal acquired by the photodetector to the computer or microprocessor, analyze and process the collected line data, and calculate its characteristic parameters through the formula: signal-to-noise ratio SNR and diffraction efficiency η, and display and print Measurement results, the formula stated:

$\mathrm{<span\; class="notranslate">\; SNR</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; N</span>}}}$

$\mathrm{<span\; class="notranslate">\; \&eta;</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; \%</span><span\; class="notranslate">\; ,</span>$

Among them, I _S is the signal light intensity, I _N is the noise light intensity, and I ₀ is the light source light intensity.

A detector for realizing the above detection method, comprising:

——Light source: used to generate incident light and incident the anti-counterfeit holographic sample at an angle θ with the sample normal, the θ angle is 30°-60°;

——Sample platform: used to fix the anti-counterfeiting holographic sample to be tested;

——Displacement mechanism: It is composed of screw pair, the nut in the screw pair is fixed with the sample platform, and the screw is connected with the stepping motor, which is used to drive the sample platform to perform one-dimensional displacement movement, and realize the one-dimensional identification of the tested anti-counterfeiting holographic sample Dimensional automatic scanning; the stepper motor is controlled and driven by the control module;

——Photoelectric receiver: used for real-time acquisition of the anti-counterfeit holographic sample in the scanning direction, a line of diffracted light intensity signals reflected by the concave mirror, and convert the light intensity signals into voltage signals;

——Data acquisition module: used to collect the voltage signal converted by the photoelectric receiver and send it to the control module;

——Control module: used to receive the voltage signal sent by the data acquisition module, extract the signal light intensity I _S and noise light intensity I _N after processing, use the light source light intensity I ₀ that has been obtained before scanning, and calculate according to the formula The characteristic parameters of anti-counterfeiting holographic product mark: signal-to-noise ratio SNR and diffraction efficiency η, described formula:

$\mathrm{<span\; class="notranslate">\; SNR</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; N</span>}}}$

$\mathrm{<span\; class="notranslate">\; \&eta;</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; \%</span><span\; class="notranslate">\; .</span>$

The photoelectric receiver is completed by photocell, and the data acquisition module and control module are realized by computer or microprocessor.

Advantages and positive effects of the present invention: the present invention proposes a detection method in an automatic scanning mode and a detection instrument for realizing the method. This method uses a displacement mechanism to drive the sample platform to perform one-dimensional displacement movement to complete the function of one-dimensional automatic scanning and measurement of the characteristic parameters of the anti-counterfeiting holographic product mark, which has changed the problem of excessive adjustment and automatic measurement; for data collection and The processing is completed by a computer or microprocessor, which automatically calculates the characteristic parameters of the anti-counterfeiting holographic product to be tested, and directly displays and prints the measurement results; the design of the instrument realizes the measurement automation, making the measurement process simple, fast, and highly operable. Requirements for operator expertise are reduced.

[Description of drawings]:

Figure 1 is a measurement light path diagram;

Fig. 2 is a system control and acquisition structure block diagram;

Figure 3 is a sample diagram of an anti-counterfeiting holographic product identification;

Fig. 4 is the light intensity distribution curve of sampling points along the scanning direction;

Fig. 5 is the light intensity distribution curve of sampling points after computer preprocessing;

Fig. 6 is an explanatory diagram of signal light intensity and noise light intensity in the light intensity distribution curve;

Fig. 7 is a schematic diagram of the scanning displacement mechanism of the anti-counterfeiting holographic product characteristic parameter detector.

【Detailed ways】:

Embodiment 1: detection method

As shown in Figure 1, the anti-counterfeiting holographic sample to be tested is placed on the sample platform and fixed; the light beam emitted by the light source 1 is irradiated on the anti-counterfeiting holographic product sample 2 at an incident angle θ (30°-60°); in the normal direction of the sample A concave mirror 3 is placed, and the normal M of the concave mirror and the normal N of the sample form an included angle of ψ (about 10°±2°). The diffracted light of the sample is reflected by the concave mirror and collected by the photoelectric receiver 4 .

The invention uses a stepping motor to drive the sample to move, and the sample is displaced relative to the incident light spot. Since the incident light is irradiated on different positions of the sample, the intensity of the diffracted light in the normal direction of the sample is different, and the photoelectric receiver receives the change. The light intensity signal is collected by the computer at the same time, so as to obtain the light intensity distribution curve of the sample along the scanning direction. For the sample shown in Figure 3, after data collection by computer, the light intensity distribution curve shown in Figure 4 is obtained, after computer processing, the light intensity distribution curve shown in Figure 5 is obtained, and then analyzed and processed by computer software , extract the signal light intensity I _S (shown by 5 in Figure 6) and the noise light intensity I _N (shown by 6 in Figure 6), and use the laser light source light intensity I ₀ that has been obtained before scanning, then According to the formula (1) and formula (2), the characteristic parameters of the anti-counterfeiting holographic product mark: signal-to-noise ratio and diffraction efficiency are calculated.

Embodiment 2: detector

The detector (shown in Fig. 1, Fig. 2 and Fig. 7) includes a light source 1, a one-dimensional automatic displacement mechanism, a photoelectric receiver 4 and a data acquisition and control module. The light source 1 uses a He-Ne laser. In order to realize the scanning function of anti-counterfeiting holographic product marks, the instrument uses a stepping motor 7 to drive the movement of the sample platform; the photoelectric receiver uses a photocell to complete the conversion of the light intensity signal into a voltage signal, and the back-end data acquisition card performs Acquisition; the data acquisition module and the control module are all completed by the computer, the data acquisition uses the PCI acquisition card, and the motor control utilizes the digital I/O interface of the PCI acquisition card to realize.

Figure 2 is a structural block diagram of system control and acquisition. Using the digital I/O port of the PCI acquisition card, the computer sends instructions to the drive circuit of the stepper motor to control the stepper motor to drive the movement of the displacement platform, thereby driving the sample platform and samples to perform one-dimensional The movement makes the light intensity received by the photoelectric receiver change, and it is converted into a voltage signal through the processing circuit. The processing circuit mainly uses a zero-volt bias circuit to convert the photocurrent into a voltage signal, and gains it through an operational amplifier. The PCI acquisition card collects this voltage signal.

Fig. 7 is a structural diagram of the scanning displacement mechanism. In the figure: 7. Stepper motor; 8. Lead screw; 9. Sample platform; 10. Sample holder; 11. Rotary platform; 12. One-dimensional manual displacement platform; 13. Linear bearing guide rail. The working process is as follows: the computer controls the rotation of the stepping motor 7, and converts the rotation of the stepping motor into a linear motion through the screw 8, thereby driving the sample platform 9 to perform linear motion. The function of the one-dimensional manual displacement platform 12 and the rotating platform 11 is to adjust the position of the initial scanning point and the scanning direction of the sample. The function of the linear bearing guide rail 13 is to make the movement of the sample platform more stable, and also to guide and reduce resistance. The role of the sample platform 9 and the sample holding piece 10 is to effectively clamp the sample, wherein a magnet is embedded in the sample platform 9, and is connected with the sample holding piece by magnetic adsorption to play the role of clamping the sample.

The working process of the instrument is: place the anti-counterfeit holographic sample to be tested on the sample platform and fix it; let the beam emitted by the He-Ne laser irradiate the sample at an incident angle θ (30°-60°); the diffracted light of the sample passes through the concave mirror The reflection is received by the photocell; the computer software issues instructions, and the digital I/O interface on the PCI acquisition card is used to control the stepper motor drive circuit, so that the stepper motor rotates, and the rotation of the stepper motor is changed to the sample through the screw pair. The displacement movement of the stage drives the sample to move; the sample is displaced relative to the incident light spot. Since the incident light is irradiated on different positions of the sample, the intensity of the diffracted light in the normal direction of the sample is different, and the photoelectric receiver receives the change. Light intensity signal; it is converted into a voltage signal by the processing circuit, and the signal collected by the PCI acquisition card is controlled by computer software to obtain the light intensity distribution curve of the sample along the scanning direction; then the computer software is used to process the light intensity distribution curve and Analyze and calculate the characteristic parameters of anti-counterfeiting holographic products: signal-to-noise ratio and diffraction efficiency, and display and print the measurement results.

Claims (3)

1. An anti-counterfeiting holographic product characteristic parameter detection method is characterized in that the method comprises successively: ——Place the tested anti-counterfeit holographic sample on the sample platform and fix it; ——Let the light beam emitted by the light source enter the anti-counterfeiting holographic sample along the angle θ with the sample normal, and the θ angle is 30°-60°; ——Place a concave reflector in the direction of the sample normal N, the normal M of the concave reflector and the sample normal N form an included angle ψ, ψ is 10°±2°; ——Let the sample platform drive the tested anti-counterfeiting holographic sample to perform one-dimensional displacement movement along the direction perpendicular to the normal line of the sample; ——Place the photodetector on the other side of the concave mirror, and acquire multi-point light intensity signals in the scanning direction in real time; ——Send the light intensity signal acquired by the photodetector to the computer or microprocessor, analyze and process the collected line data, and calculate its characteristic parameters through the formula: signal-to-noise ratio SNR and diffraction efficiency η, and display and print Measurement results, the formula stated: $\mathrm{<span\; class="notranslate">\; SNR</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; N</span>}}}$ $\mathrm{<span\; class="notranslate">\; \&eta;</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; \%</span><span\; class="notranslate">\; ,</span>$ Among them, I _S is the signal light intensity, I _N is the noise light intensity, and I ₀ is the light source light intensity. 2. A detector for realizing the detection method according to claim 1 is characterized in that the detector comprises: ——Light source: used to generate incident light and incident the anti-counterfeit holographic sample at an angle θ with the sample normal, the θ angle is 30°-60°; ——Sample platform: used to fix the anti-counterfeiting holographic sample to be tested; ——Displacement mechanism: It is composed of screw pair, the nut in the screw pair is fixed with the sample platform, and the screw is connected with the stepping motor, which is used to drive the sample platform to perform one-dimensional displacement movement, and realize the one-dimensional identification of the tested anti-counterfeiting holographic sample Dimensional automatic scanning; the stepper motor is controlled and driven by the control module; ——Photoelectric receiver: used for real-time acquisition of the anti-counterfeit holographic sample in the scanning direction, a line of diffracted light intensity signals reflected by the concave mirror, and convert the light intensity signals into voltage signals; ——Data acquisition module: used to collect the voltage signal converted by the photoelectric receiver and send it to the control module; ——Control module: used to receive the voltage signal sent by the data acquisition module, extract the signal light intensity I _S and noise light intensity I _N after processing, use the light source light intensity I ₀ that has been obtained before scanning, and calculate according to the formula The characteristic parameters of anti-counterfeiting holographic product mark: signal-to-noise ratio SNR and diffraction efficiency η, described formula: $\mathrm{<span\; class="notranslate">\; SNR</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; N</span>}}}$ $\mathrm{<span\; class="notranslate">\; \&eta;</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; \%</span><span\; class="notranslate">\; .</span>$ 3. The detector according to claim 2, characterized in that the photoelectric receiver is completed by a photocell, and the data acquisition module and the control module are realized by a computer or a microprocessor.

Images