Interferometric moiré pattern encoded security holograms

This paper describes a simple method for making interferometric moiré pattern encoded security holograms. These security holograms contain multi-fold concealed and encoded anti-counterfeit security features which can only be decoded by using an encoded key hologram in the final reading process. The concealed codes in these holograms are recorded with an encoded feature, so that they remain invisible to the counterfeiters, thereby enhancing the anti-counterfeiting ability of security holograms. In the final reading process, a specific moiré-like fringe pattern is formed on the security hologram only when a reconstructing beam generated from the encoded key hologram illuminates this hologram. Further, a careful spatial filtering results in the generation of a specific moiré pattern in the observation plane and it disappears when perfectly repositioned. These can also be used as security codes for better protection against counterfeiting in embossed holograms. Recording schemes for the formation of such security holograms and typical experimental results have been presented

Holographic optical elements encoded security holograms with enhanced features

A simple and cost-effective two-step method for forming encoded security holograms with enhanced features is described in this paper. These security holograms contain enhanced encoded/concealed anti-counterfeit security features, which can only be decoded using a key hologram in the final reading process. The encoded key hologram and the security hologram are in the form of special encoded complex holographic optical elements. When the security hologram is illuminated with the decoding beam, specific moiré-like fringe patterns are formed on the security hologram and in addition several spatially separated bright focused spots are also generated from the security hologram. A careful spatial filtering of these bright spots results in specific moiré patterns at different locations in the observation plane and moreover these patterns contain variable interferometric features. Further, these moilé patterns disappear when the security hologram is perfectly repositioned and only the variable interferometric features are formed. Since these security holograms contain variable interferometric features in addition to the specific moiré patterns and bright focused spots, thus making these holograms suitable for both visual and as well as machine inspection

Security Holograms Readable with an Encoded Key Hologram

A simple and cost effective two-step method for making security holograms, which are readable with an encoded key hologram, has been presented. These security holograms contain an additional security feature which can be read only by using an encoded key hologram in the reading process. In the final reading process, the sharp focus spot emerges only when the security hologram is illuminated by the decoding, reconstructing beam generated from the encoded key hologram. Since the verification/identification pattern in these holograms is a sharp focus spot rather than an image pattern, this type of security holograms are suitable for both visual as well as machine inspection. They can also be used as security codes for better protection against counterfeiting in the embossed holograms. Experimental results achieved have been discussed

Interferometry based security hologram readable with an encoded key hologram

A simple and cost-effective method for making security holograms has been presented, which incorporates holographic interferometry as verification feature in addition to spatially separated sharp focus spots. When the security hologram is illuminated with decoding reconstructing beam generated from an encoded key hologram, two spatially separated sharp focus spots emerge at the predefined positions and can be read through a photoelectric detector array. In addition, these focused spots upon divergence in longitudinal direction further generate specific kind of interferometric fringe patterns of random profile contained in them, which are suitable for further visual inspection. These machine-readable and visual verifiable features can be used for better counterfeit-resistant security codes in embossed holograms. Recording schemes for the formation of such security holograms and typical experimental results have been presente

Holographic optics based interferometer for real-time testing of phase objects

A simple and cost effective method for making holographic optics-based interferometer, which is suitable for performing optical test studies on phase (transparent) objects in real-time, has been described. The optical arrangement in the proposed method involves a very simple alignment procedure and inexpensive holographic recording material is used in the formation of holographic optical elements. Recording schemes for the formation of holographic optical elements and the related techniques for the realisation of the proposed interferometer along with typical experimental results have been presente

Encoded Reference Wave Security Holograms with Enhanced Features

A simple and cost effective two-step method for making encoded reference wave security holograms with enhanced features, which are readable with an encoded key hologram, has been presented. In the final reading process, two spatially separated sharp focus spots (bright spots) emerge only when the security hologram is illuminated by the decoding, reconstructing beam, generated from the encoded key hologram. In addition these focused spots, upon divergence in the longitudinal direction, further generate variable interferometeric features, i.e. circular and linear interference fringe patterns contained respectively in them. Since the verification/identification pattern in these security holograms are variable interferometric features in addition to the spatially separated sharp focus spots, this type of security hologram is suitable for both visual as well as machine inspection. They can also be used as security codes for better protection against counterfeiting embossed holograms. Recording schemes for the formation of such security holograms and typical experimental results have been presented

Direct Visualization of Young’s Boundary Diffraction Wave

Experimental investigations on Young’s boundary diffraction wave are presented where a wavefront division interferometric scheme is used on diffracted wavefront to generate two-beam interference fringes in the geometrically shadow region. These fringes have good visibility and are observable in the whole space, strongly advocating the physical existence of Young’s boundary diffraction wave as a separate entity. Analysis of these fringes may provide vital information about the structure and nature of boundary diffraction wave e.g. existence in whole space, dependence of amplitude on obliquity factor etc

Realization of an optical interferometer based on holographic optics for real-time testing of phase objects

Abstract. The paper describes a simple and cost e®ective method for the realization of an optical interferometer based on holographic optics, which use minimal bulk optical components. The optical arrangement in the proposed method involves a very simple alignment procedure and inexpensive holographic recording material is used in the forma- tion of holographic optical elements. The proposed interferometer set-up is quite suitable for performing optical test studies on phase (transparent) objects in real-time. Recording schemes for the formation of holographic optical elements and the related technique for the realization of the interferometer set-up along with the experimental results have been presented

Concealed moiré pattern encoded security holograms readable by a key hologram

This paper describes a novel method of incorporating concealed coding features in security holograms in the form of moiré patterns, which need an encoded key hologram to decode them. These concealed codes in the holograms are in turn recorded with an encoded feature, so that these remain invisible to the counterfeiters thereby enhancing the anti-counterfeiting ability of security holograms. These security features, which are specific kinds of moiré patterns, can only be decoded by using an encoded key hologram in the final reading process. Though these type of security holograms are quite suitable for visual inspection, they possess high degree of anti-counterfeit ability and also do not require expensive reading machines. They can also be used as security codes for better protection against counterfeiting embossed holograms. Two different recording schemes for the formation of such security holograms and typical experimental results have been presented

A compact holographic optics based interferometer

A compact holographic optics-based interferometer involving the use of minimal bulk optical components is described. The optical arrangement in the proposed system involves a simple alignment procedure, and conventional holographic recording material is used in the formation of holographic optical elements. Recording schemes for the formation of holographic optical elements and related techniques for the realization of the proposed interferometer along with typical experimental results are presented. The interferometer is quite suitable for performing optical test studies on phase (transparent) objects in real time