Currently, diffractive optical elements with light guide substrates are used in miniature display systems especially in systems for vehicles, aircraft, and systems, where the observed image overlaps with the real scene. It is possible to get rid of the double image and zero order (this feature is inherent in computer generated hologram Fourier) as a result of synthesis of complex Fresnel hologram. As a result, we can synthesize a complex hologram that is free of the twin image and the zero-order light using a single spatial light modulator. The holograms are recorded with a spatial light modulator in a projection mode. This configuration consists of glass substrate with computer generated holograms Fresnel and diffraction gratings, as a diffractive optical element, for input and output of radiation. Reconstructing beam is incident on the computer generated holograms Fresnel, and then through diffraction grating 1 radiation is introduced into the plate at an angle of TIR and spread in it. When the light reaches the surface of the substrate with a diffraction grating 2, part of the light emerges from it. diffraction gratings are two diffraction gratings, which should have different diffraction to ensure uniform brightness of the observed image. It should be noted that to ensure the non-uniform diffraction efficiency of diffraction grating exit area was divided into multiple zones. Thus, the zonal diffraction grating was recorded with its exposure value. Light beams diffracted on computer generated holograms Fresnel enter and then multiple output from substrate, thus forming for observer an increased image of the test object.
This paper presents new high-performance optical-electronic scanner for security holograms authentication. Scanning speed is increased due to the use of sophisticated modern scanning systems, high-speed sensors and specifically designed and manufactured optical system components. Correlation filters used in the information processing decrease total processing time and increase resulting reliability of the authentication process.
A holographic wavefront sensor scheme using a phase-only spatial light modulator (SLM) with reduced cross-talk noise influence is proposed. A novel method for plane wave aberration measuring using a phase-only computer-generated hologram is devised. The proposed scheme and algorithm are validated with numerical simulations and experiments.
KEYWORDS: Holograms, Scanners, Information security, Optoelectronics, Optics manufacturing, Diffraction, Control systems, Reliability, Inspection, Process control
At present time, security holograms are widely used to protect against counterfeiting of various documents and identity cards. To control the security holograms authenticity on documents, devices that exclude the influence of the human factor and increase the speed and reliability of identification are needed. The paper presents an automatic optic-electronic scanner for operational control of security holograms authenticity on documents. The algorithm of data processing, operation principle of scanner and its design are described. The use of modern scanning systems, high-speed recording devices, specially designed and manufactured components of the optical system, as well as the use of correlation filters in the algorithm for recognizing the information received from the hologram, significantly reduce the time and raise the reliability of the security holograms authenticity control process.
Security holograms are widely used for anti-counterfeiting of banknotes, documents and consumer products. The development of automated devices for operative authentication and quality inspection of security holograms is still an actual task. There are several approaches to solving this problem. One of them is based on an image comparison of inspected and reference holograms. Also for quality inspection of security holograms, the methods based on direct and indirect measurements of microrelief parameters are used. In this article we present a complex solution for automated quality inspection and authentication of security holograms.
The holographic disk reading device for recovery of CGFH is described. Principle of its work is shown. Analyzed approaches for developing algorithms, used in this device: guidance and decoding. Listed results of experimental researches.
Holographic memory systems provide such advantages as long data storage term, high data density and do not need a power supply. Instead of recording interference pattern, it is proposed to record computer generated 1D Fourier holograms (CGFH). High information density is reached by multiplexing 1D Fourier Holograms. In this work factors, which impact the quality of recorded CGFH are analyzed in mathematical modelling and experimental researches.
This paper is dedicated to mathematical modelling of microwave signal processing by photonic time-stretch system. Photonic time-stretch system consists of wideband laser source, electro-optic modulator, two parts of optical fiber, photodiode and electronic ADC. Laser radiation is chirped in fiber, and then modulated by radio signal, which after that is stretched in fiber. Being stretched by second fiber module a pulse is send to photodiode, which converts a light intensity to electronic signal to be processed by ADC. Examples of simulation results are presented.
Holographic memory systems provide such advantages as long data storage term, high data density and do not need a power supply. But traditional holographic systems require vibration isolation and are rather complicated. So computer generation of Fourier holograms (CGFH) is proposed. Instead of recording interference pattern, it is calculated on computer. High information density is reached in new method by multiplexing 1D Fourier Holograms. Optical equivalent of the 1D Fourier holograms computer synthesis is listed. Different spatial light modulators are analyzed for displaying CGFH. System for hologram recording is described. Results of recovering information CGFH are also listed.
We address the recognition problem of grayscale images of object subjected to out-of-plane rotation distortion. We compare filter realization as computer generated hologram and filter projection on modulator domain. Our study results of the filter discriminating characteristic analysis are shown. The results of the filter implementation modeling in 4-f correlator and the initial experimental result are represented.
Computer holographic synthesis allows to significantly simplify the recording scheme of microholograms in holographic memory system as the classic high precision holographic setup based on two-beam interference is removed by simple scale reduction projection scheme. Application of computer generated 1D-Fourier holograms provides the possibility of selective reconstruction of the multiplexed holograms with different orientation of data lines by corresponding rotation of anamorphic objective (cylindrical lens), used in the read-out systems. Two configurations of read-out optical scheme were investigated by our team: full-page scheme and line-by-line scheme. In the present article we report the specificities of these schemes and consider their advantages and disadvantages. The results of experimental modeling of both read-out configurations are also presented.
Minimum Noise And Correlation Energy (MINACE) filters application provides good ability to recognize in case of grayscale input images of an object with background noises. For fast correlation matching MINACE filters can be used in 4-f correlators as a computer generated hologram (holographic filters). In this paper different variants of holographic filters realization were discussed. The results of correlation recognition with holographic MINACE filters are presented.
Security holograms (SH) are widely used for authenticity protection of document and product due to difficulties of such a protection mark falsification. Mass production of SH uses widespread technology of hot foil or lavsan paper stamping. The quality of holograms significantly depends on perfection of nickel master-matrix that is used in stamping equipment. We represent the method for automated quality inspection of nickel mastermatrix based on digital processing of its surface relief images. Proposed processing algorithm is based on combination of image spatial frequency analysis and image matching using distortion invariant correlation filters. The results of our method application for real master-matrix inspection are shown in this paper.
Classic holographic memory systems use two-beam approach based on fixation of interference pattern between object and reference coherent beams on holographic recording medium. The size of single pattern is about several micrometers. High precision optical set up is required to form such a microhologram, that is the reason of excessive price for holographic recording devices. Methods of computer holographic synthesis allow to calculate holographic patterns numerically as 2D images. These images can be realized with the use of spatial light modulator, then reduced in optical projection system and exposed on holographic medium. In this paper we represent the research of holographic memory system based on computer generated Fourier holograms projection.
Security holograms (SH) are perspective for document and product authenticity protection due to difficulties of
such a protection mark falsification. Mass production of SH uses widespread technology of hot foil or lavsan
paper stamping. The quality of holograms significantly depends on perfection of nickel master-matrix that is
used in stamping equipment. We represent the method of automatic quality inspection of nickel master-matrix
based on digital processing of its surface relief microphotographs. Proposed processing algorithm is based on
combination of image spatial frequency analysis and image matching using distortion invariant correlation filters.
The results of our method application for real SH master-matrices inspection are shown in this paper.
Optical correlators are well known to be perspective for real time image recognition. Application of distortion invariant filters (DIF) provides image recognition with increased speed of correlation image matching. Minimum noise and correlation energy filters (MINACE filters) provide good recognition in the case of gray-scale input images. These filters possess a good mathematical basis and can be efficiently implemented in digital processing systems or in hybrid opto-digital correlators at a high rate. This paper is subjected to synthesis and realization of MINACE filters for 4-f correlator as computer generated holograms (holographic filters).
Application of distortion invariant filters (DIF) provides the possibility of invariant image recognition with
increased speed of correlation matching. DIF with the minimization of correlation energy enable to control the
properties of output correlation signal due to the parameterization during its synthesis. There are several types
of such a filters presented nowadays. The relevance degree of each type of filter application is determined by the
specific conditions of the recognition task. Thus it requires a comparative analysis of the filters performance.
The simulations were provided for the DIF of the following types: MACE (Minimum Average Correlation
Energy Filter), GMACE (Gaussian-minimum average correlation energy filters), MINACE (Minimum noise and
correlation energy filter) and WMACE (the version of GMACE where the smoothing function is the wavelet).
The synthesis of filters was carried out under identical conditions of gray-scale image recognition problem (out
of plane rotated objects). The comparison results of discrimination characteristics and the requirements of DIFs
synthesis are described and discussed.
Realization of distortion invariant correlation filters in optical image correlators open possibilities for object identification with remarkably high computational capabilities. Application of the linear phase coefficient composite filter (LPCCF) is attractive for recognition of binary edged images. We use methods of digital holographic synthesis to realize LPCCF in a coherent 4-F correlator as a computer-generated amplitude holographic filter. A high resolution spatial light modulator (SLM) has to be implemented for such a filter representation. Transparency limitations of high frame rate and high resolution SLM's and its effect on recognition performance of holographic filter in the 4-F correlator are discussed in the given paper.
Invariant correlation filters application is the method to achieve invariance of image recognition in presence
of input object distortions. Composite filter with linear phase coefficients (LPCC filter) is one of the perspective
types of correlation filters. LPCCF can be realized in a scheme of optoelectronic Vander Lught's correlator as
synthesized holographic filters for recognition in real time conditions. Application of binary spatial light modulators
for realization of holographic LPCCF is especially interesting. Variants of "pixel to pixel" binarization
methods or representation of grayscale gradation using binary "subpixel" raster can be used for binary representation
of the initial hologram. The results of correlation recognition with binary amplitude holographic LPCCF
application are represented in the paper.
Invariant correlation filters application allows to achieve correlation peak invariance in the presence of distortions of
input object in comparison with reference object. One of the most perspective correlation filters are Linear Phase
Coefficient Composite Filters (LPCC filter). These filters provide good recognition results in the case of geometrically
distorted contoured binary input objects. LPCC filter realization in 4-f correlator demands formation of corresponding
impulse response of the optical system. The results of synthesis and realization of LPCC filters as holographic diffraction
elements are presented in the paper.
The results of realization of linear phase coefficient composite (LPCC) filters in 4-f correlator are presented in this paper.
LPCC filters application allows achieving invariance of correlation peak in the presence of geometric distortions of
contour objects. Invariant correlation filters were synthesized as amplitude holograms with continuous transparency and
realized as binary amplitude holograms. The results of correlator signals modeling for the cases with different numbers
of hologram counts which used to represent grayscale level gradation are presented.
This paper contains the results of synthesis and realization of linear phase coefficient composite (LPCC) filters in 4-f
correlator. LPCC filters application allows achieving invariance of correlation peak in the presence of geometric
distortions of contour objects. LPCC filters were realized as computer generated binary amplitude holograms for
application in optical correlator. Experimental results of invariant pattern recognition are presented.
Image recognition methods based on evaluation of intensity Fourier-spectrum circular and radial harmonics are attractive
for applications due to the possibility to obtain a range of features invariant to the shift, rotation and change scale of the
input image. Application of array of photodetectors with special topology in a combination with digital postprocessing
allows to achieve high accuracy of measurement of harmonics in optics. In paper results of experiments of high accuracy
measurement of circular and radial harmonics are presented.
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