CN102759441A - Multiband polarization imaging anti-counterfeiting element identification system - Google Patents

Abstract

The invention relates to a multiband polarization imaging anti-counterfeiting element identification system. The identification system is characterized by comprising a light filter rotary wheel, three CCD (Charge Coupled Device) cameras, a motor system, a halogen lamp and a computer; the front and the back of a to-be-tested sample are respectively provided with the halogen lamp and the light filter rotary wheel, and the light filter rotary wheel is provided with multiple polarizing films; the three CCD cameras are arranged behind the light filter rotary wheel, and the light filter rotary wheel is controlled by the motor system; and the three CCD cameras output the captured images to the computer for processing. According to the invention, a polarized light source, a wave plate, the polarizing films, the CCD cameras and a stepped motor are integrated in one system, so that optical electromechanical integration is realized; and the multiband 1/4 lambda wave plate and the polarizing cameras are used, the light filtering band is selected according to the detection aim in a customization manner to perform anti-counterfeiting identification, the three CCD cameras work at the same time and accurately control the rotation of the motor through a DSP (Digital Signal Processor) so as to quickly obtain images; and the identification system further has the functions, such as image filtering, fusion, storage and on the like, thereby realizing the aim of working steadily and reliably, and saving human and financial resources.

Description

Multiband polarization imaging Security element identification system

Technical field

The present invention relates to a kind of multiband polarization imaging Security element identification system; For the polarization test pieces of using the polarization anti-counterfeiting technology to make, stealthy labeling etc.; Can effectively detect the information of wherein hiding; And the detection method of native system is easy to use, testing result is intuitive and reliable, is with a wide range of applications in false proof discriminating field.

Background technology

In order to protect article; For example value document and paper; And the spare part of consumer product area, medicine, textile or other registered trademark products avoid imitated and forge and distort, and in order to detect the true and false of these article, for they have disposed specific Security element.Making Security element needs some special material and pigment, because they have specific optical characteristics, so be not easy by imitated.Known Security element has watermark, be combined in anti-counterfeiting line in the paper, luminous or magnetic-particle etc.; Can Security element be added in printing-ink or the relief hologram, be applied on the packing with shielded article surface or article as the paper tinsel element then.

At present; The method of the Security element that the identification polarized material is made; Mainly be to rely on that the color that manifests under the polarized light is different with the color that under natural light or light, manifests to be realized; Although relatively more directly perceived, it does not make full use of the spectrum and the polarization characteristic of implicit pattern, can not accurately find out the information of hiding in the Security element subtly.

Summary of the invention

The technical matters that solves

Weak point for fear of prior art; The present invention proposes a kind of multiband polarization imaging Security element identification system; A plurality of hardware modules such as integrated data collection and processing, motor Spin Control; Have multiband, automatically space-time registration and characteristics such as real-time, satisfy the performance requirement of polarization Security element identification.

Technical scheme

A kind of multiband polarization imaging Security element identification system is characterized in that comprising optical filter runner, three CCD cameras, electric system, Halogen lamp LED and computing machines; Be provided with Halogen lamp LED and optical filter runner in the front and back of false proof print to be measured, the optical filter runner is provided with a plurality of polaroids; The postposition of optical filter runner is three CCD cameras, and the optical filter runner is controlled by electric system; Three CCD cameras export the image that absorbs to computing machine and handle; After the optical filter runner circled, computing machine calculated polarization parameter and carries out image registration image rectification, and then sent signal is controlled double-deck optical filter runner to electric system rotation; Said double-deck optical filter runner is provided with a plurality of circular holes, and a double-deck optical filter is set in each circular hole, and each double-deck optical filter only allows the light of the specific band in the white light to pass through; The polarization angle of the preposition polaroid of said three CCD cameras is 0 °, 45 ° and 90 °; Shuttling movement relation between three CCD cameras, electric system and the Computer Processing is: when electric system is controlled double-deck optical filter runner and changeed for 1/6 week; Trigger the CCD camera imaging; When double-deck optical filter runner accomplished for 1 week, computing machine carried out image rectification and calculates polarization parameter; Image rectification finishes storage to be accomplished, and the motor of computer control electric system makes that again changeing double-deck optical filter runner changeed for 1/6 week, started following one-period.

Said double-deck optical filter runner is provided with six circular holes that are used to install optical filter; Each diameter is about 25mm; Wherein, circular hole is empty, and the fast axle that four circular holes are installed the wavelength that differs from one another respectively becomes 0 ° 1/4 λ wave plate with reference direction; Another circular hole is installed fast axle becomes 90 ° with reference direction 1/4 λ wave plate, and its bandwidth must cover the wavelength of four the single wave plates in front.

It is degree of polarization DoLP and polarization position angle AoP that said image rectification calculates polarization parameter, and calculation method is:

$\mathrm{DoLP}=\sqrt{\frac{Q^2+U^2+V^2}{I}},$ $\mathrm{AoP}=\frac{1}{2}{\tan }^{-1}\frac{U}{Q};$

Wherein: I representes the total intensity of light wave, and I=I (0 °, 0 °)+I (90 °, 0 °);

Q representes the intensity of linearly polarized light on the horizontal direction, and Q=I (0 °, 0 °)-I (90 °, 0 °);

U representes the intensity of linearly polarized light on 45 ° of directions, and U=2I (45 °, 0 °)-I (0 °, 0 °)-I (90 °, 0 °);

V representes the circular polarization light intensity, and V=2I (45 °, 90 °)-I (0 °, 0 °)-I (90 °, 0 °).

Beneficial effect

A kind of multiband polarization imaging Security element identification system that the present invention proposes; Polarized light source, wave plate, polaroid, CCD camera and stepper motor are integrated in the system, have realized optical, mechanical and electronic integration, and adopt multiband 1/4 λ wave plate and polarization camera; Can carry out anti-counterfeiting identification according to surveying the self-defined selection optical filtering of purpose wave band; Three CCD cameras are worked simultaneously, have advantages such as compact conformation, volume are little, quick, accurately control motor through DSP and rotate and obtain image fast; And system also has functions such as image filtering, fusion and storage, therefore can reach the purpose of reliable and stable work, saving manpower and financial resources.

Description of drawings

Fig. 1 multiband polarization imaging anti-counterfeiting identification system hardware structure figure;

Fig. 2 multiband polarization imaging anti-counterfeiting identification system works flow process figure;

Fig. 3 runner quarter wave plate scheme of installation

Light path travel path and polarization multi-wavelength data cube synoptic diagram in Fig. 4 imaging device;

Fig. 5 polarization parallel light-source structure figure;

Fig. 6 embodiment image registration process flow diagram;

Required scaling board synoptic diagram during Fig. 7 embodiment image registration is handled.

Embodiment

Combine embodiment, accompanying drawing that the present invention is further described at present:

In the technical scheme of the present invention, mainly comprise polarized light source module, multiband runner control module (being motor control module), ingredients such as polarization camera set image capture module, image processing module.

The light source that this embodiment adopted is four Halogen lamp LEDs, forms polarized light source with four groups of sources of parallel light and polaroid, uses Halogen lamp LED as light source, before light source, places linear polarizer, adds lens behind the polaroid, and is as shown in Figure 5.Each linear polarizer light transmission shaft equates that with the angle of reference direction light is after the target area overlaps, and area coverage is not less than 50 * 75mm, is used for realizing the polarizing light irradiation to Security element to be measured.

The computing machine that this embodiment adopted comprises the camera acquisition software, and computer model is Lenovo Qitian M7300, and in addition, the multiway images transmitting device is made up of the PCI1394 video frequency collection card usually, loads in the host computer system.

The CCD camera of this embodiment adopts dimension to look MV-1300, and the drive motor leadshine-1.8/4.0A stepper motor of runner, 1/4 λ wave plate adopt wavelength for covering visible light wave range and other 5 wave bands.The control module of runner is the polarization multiband imager control system of seminar's exploitation.

Multiband runner control module mainly realizes the setting of runner self optical filter and the accurate control that motor rotates coaxial runner.On runner, designed six circular holes that are used to install optical filter altogether, each diameter is about 25mm, wherein; A circular hole is empty; Circular hole is installed fast axle becomes 90 ° with reference direction 1/4 λ wave plate, and its bandwidth must cover the wavelength of four the single wave plates in front, designs like this and is convenient to the Stokes calculation of parameter; The fast axle that all the other four circular holes are installed the wavelength that differs from one another respectively becomes 0 ° 1/4 λ wave plate with reference direction, as shown in Figure 3.

Be right after the polarization camera behind the multiband runner, polarization camera set image capture module is mainly realized the collection and the storage of three road polarization images.This module relates to three CCD cameras and three hardware such as linear polarizer, and three linear polarizer become 0 °, 45 °, 90 ° fixed angle three CCD camera lens fronts with the axis of homology respectively with reference direction, and the image of collection is shown by computing machine.

Software flow of the present invention is:

IMAQ, image registration, polarization parameter calculate

Referring to Fig. 2, introduce runner control and IMAQ

Circuit control unit is integrated on the DSP disposable plates, is the core component of native system, and its concrete control procedure is following:

1. the motor control module in the circuit control unit carries out initialization operation to motor, accurately controls runner to the tram through coaxial manner, and promptly the runner hole combines with camera lens fully;

2. feed back signal to polarization camera image acquisition module by sending near switch, control three road CCD cameras simultaneously, automatic exposure is carried out to picture, carries out the storage of image after imaging finishes automatically;

3. send and feed back signal to motor control module, control driven by motor runner rotates 60 °;

4. after rotation finishes, repeat 2.,,, send and feed back signal to circuit control unit, suppressed zero position by doing zero correction near switch 3. until the number of turns that is provided with in advance;

5. during 4., if amount of images satisfies the requirement of calculating the Stokes parameter, can read, the operations such as calculating of geometry correction and polarization parameter memory image.

According to the influence of in calculating the degree of polarization process, whether ignoring circularly polarized light intensity V, the collection of polarization image is divided into two kinds of situation:

(1) ignores the influence of V: only need to consider the calculating of polarization parameter under natural light incident condition this moment.Promptly only need obtain three images under the polarization angle and just can calculate polarization parameter through the circular hole of sky;

(2) influence of consideration V: consider the calculating of polarization parameter under monochromatic light incident condition this moment.The circular hole that promptly needs single 0 ° of 1/4 λ wave plate is forming images three polarization angles under and 90 ° of 1/4 λ wave plate forms images under 45 ° of linear polarizer that four width of cloth images just can calculate polarization parameter successively totally.

Referring to accompanying drawing 6,7, mainly introduce the process of image registration.At first scaling board is positioned over the target location, and keeps same plane with target as far as possible, obtain the scaling board image by three CCD cameras.Extract the SIFT unique point of three width of cloth images then; Calculate the associating descriptor of each unique point then; Next be benchmark with one of them image of camera; Use two-way matching method that all the other two width of cloth images and benchmark image are mated, adopt at last based on the method for parameter estimation of RANSAC algorithm and least square method and find the solution the transformation model parameter, realize the registration between three width of cloth images.

Introducing polarization parameter calculates:

In the polarization imaging technical applications, generally adopt the polarization state of the accurate monochromatic plane wave of Stokes vector analysis, the Stokes vector can be described as: S=[IQUV] ^TWherein, I representes the total intensity of light wave, and Q representes the intensity of linearly polarized light on the horizontal direction, and U representes the intensity of linearly polarized light on 45 ° of directions.V representes the circular polarization light intensity.In application, V is generally very little, in native system, when using panchromatic photometry to calculate the polarization parameter image, ignores the size of V, and when using a certain single band photometry to calculate the polarization parameter image, V can not ignore.

Axis of homology direction and the reference direction angle of supposing linear polarizer are θ, and wave plate quick shaft direction and reference direction angle are φ, and then the strength formula of Stokes does

$I(\mathrm{\θ},\mathrm{\φ})=\frac{1}{2}[I+Q\cos 2\mathrm{\θ}+U\cos \mathrm{\φ}\sin 2\mathrm{\θ}+V\sin \mathrm{\φ}\sin 2\mathrm{\θ}]$

Thereby derive and can know that Stokes parameter and polarization parameter (degree of polarization DoLP, polarization position angle AoP) are:

I＝I(0°,0°)+I(90°,0°)

Q＝I(0°,0°)-I(90°,0°)

U＝2I(45°,0°)-I(0°,0°)-I(90°,0°)

V＝2I(45°,90°)-I(0°,0°)-I(90°,0°)

$\mathrm{DoLP}=\frac{\sqrt{Q^2+U^2+V^2}}{I}$

$\mathrm{AoP}=\frac{1}{2}{\tan }^{-1}\frac{U}{Q}.$

Claims (3)

1. a multiband polarization imaging Security element identification system is characterized in that comprising optical filter runner, three CCD cameras, electric system, Halogen lamp LED and computing machines; Be provided with Halogen lamp LED and optical filter runner in the front and back of false proof print to be measured, the optical filter runner is provided with a plurality of polaroids; The postposition of optical filter runner is three CCD cameras, and the optical filter runner is controlled by electric system; Three CCD cameras export the image that absorbs to computing machine and handle; After the optical filter runner circled, computing machine calculated polarization parameter and carries out image registration image rectification, and then sent signal is controlled double-deck optical filter runner to electric system rotation; Said double-deck optical filter runner is provided with a plurality of circular holes, and a double-deck optical filter is set in each circular hole, and each double-deck optical filter only allows the light of the specific band in the white light to pass through; The polarization angle of the preposition polaroid of said three CCD cameras is 0 °, 45 ° and 90 °; Shuttling movement relation between three CCD cameras, electric system and the Computer Processing is: when electric system is controlled double-deck optical filter runner and changeed for 1/6 week; Trigger the CCD camera imaging; When double-deck optical filter runner accomplished for 1 week, computing machine carried out image rectification and calculates polarization parameter; Image rectification finishes storage to be accomplished, and the motor of computer control electric system makes that again changeing double-deck optical filter runner changeed for 1/6 week, started following one-period.

2. multiband polarization imaging Security element identification system according to claim 1; It is characterized in that: said double-deck optical filter runner is provided with six circular holes that are used to install optical filter, and each diameter is about 25mm, wherein; A circular hole is empty; The fast axle that four circular holes are installed the wavelength that differs from one another respectively becomes 0 ° 1/4 λ wave plate with reference direction, another circular hole is installed fast and become 90 ° 1/4 λ wave plate with reference direction, and its bandwidth must cover the wavelength of four the single wave plates in front.

3. multiband polarization imaging Security element identification system according to claim 1 is characterized in that: it is degree of polarization DoLP and polarization position angle AoP that said image rectification calculates polarization parameter, and calculation method is:

$\mathrm{DoLP}=\sqrt{\frac{Q^2+U^2+V^2}{I}},$ $\mathrm{AoP}=\frac{1}{2}{\tan }^{-1}\frac{U}{Q};$

Wherein: I representes the total intensity of light wave, and I=I (0 °, 0 °)+I (90 °, 0 °);

Q representes the intensity of linearly polarized light on the horizontal direction, and Q=I (0 °, 0 °)-I (90 °, 0 °);

U representes the intensity of linearly polarized light on 45 ° of directions, and U=2I (45 °, 0 °)-I (0 °, 0 °)-I (90 °, 0 °);

V representes the circular polarization light intensity, and V=2I (45 °, 90 °)-I (0 °, 0 °)-I (90 °, 0 °).

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