An azo-functionalized copolymer derived from Poly (CACzE-MMA), CACzE, and DPP in is introduced as an innovative material to address challenges in vectorial holography. This copolymer surpasses existing materials by achieving a maximum diffraction efficiency of 85%, retaining holographic information for over 30 days, and allowing for fast writing at low intensity. By utilizing the copolymer's re-writability, polarization-angular multiplexing, and hybrid polarization-spatial multiplexing techniques are successfully implemented, which enables recording multiple images without significant crosstalk. This advancement has significant implications for holographic technology, expanding its applications in data storage, imaging, and display systems.
Holographic data storage has emerged as one of the promising technologies to satisfy the demands of high-density data storage and retrieval. Here we propose the usage of Azo functionalized copolymer as the storage material and structured light as data encoding technique to realize high-density data storage and retrieval. A hybrid polarization-angle-depth multiplexing technique us employed to further increase the data density without crosstalk. The material also exhibits long retention time and faster re-writability and thereby possesses the potential to satisfy the demands of next generation data storage technologies.
This paper presents a novel multiplexing approach termed ‘hybrid-polarization-angular-depth multiplexing’, integrating angular, depth, and polarization multiplexing. The proposed multiplexing technique is successfully implemented on a highly efficient azo-carbazole polymer film. The demultiplexing of the generated holograms is achieved simply by modifying the polarization of the reading beam.
In this paper, we introduce a simplified technique for the generation of vector beams employing polarization holograms recorded on azo-functionalized copolymer film. The method involves recording two holograms sequentially on the same area of the sample using an interferometer setup. After recording, simply illuminating the hologram with a Gaussian beam from a laser produces a vector beam. By rotating the polarization state of the reading beam, different vector beams on the higher-order Poincare sphere (HOPS) can be generated. This technique is simple, compact, and scalable and holds promising potential in optical information processing applications.
Azo-functionalized copolymer holograms were fabricated for efficient generation of structured light beams. Holograms of size 2mm x 2mm were recorded/printed on polymer samples of size 3cm x 3cm and thickness 35 µm. When irradiated with a laser beam, the hologram emits several arbitrary structured light beams. A structured beam array consisting of 100 optical vortices was practically generated. Experimental generation of vector beams and Poincare beams are also reported. Diffraction efficiencies up to 85%, retention time up to 90-days, and a small size footprint of 2mm x 2mm makes it a promising candidate for optical information processing applications.
KEYWORDS: 3D displays, Heads up displays, Digital holography, Holograms, Holography, Flexible displays, 3D image processing, Projection systems, Head, Modulation
A large-size, flexible and see-through 3D head-up display is presented. A practical 3D curved display of size 20cm x 20cm capable of reconstructing 3D scenes upto a depth of 5cm from the display at viewing angle of 20-degrees has been realized. This is a light field type display system which requires only a commercial projector and hologram screen for its working. The hologram screen is a digitally printed volume hologram which includes multiple functions such as, micro lens array, vertical tilt and horizontal curvature. These multiple functions on a single hologram screen assists in overcoming several major issues in realizing large-size and flexible 3D light field displays.
An optical system based on a Fizeau interferometer with instantaneous phase-shifting using a Wollaston prism is presented. To measure dynamic phase change of objects, a high-speed video camera of 10−5 s with a pixelated phase-mask. The laser light is split into orthogonal polarization states by passing through a Wollaston prism. Then the beam is passed through expanding and collimating optics onto a sample through a half mirror. The half mirror acts as the reference surface. The light beams reflected back from the sample and the reference half mirror are filtered with a pin hole and arrives at the pixelated camera. By adjusting the tilt of the reference surface it is possible to make the reference and object beam with orthogonal polarizations states to coincide and interfere. Digital holography based on this system is also discussed.
We can record digitally-designed information of three-dimensional (3D) objects or optical elements on a holographic photosensitive material by using wavefront printing technology. But the hologram data generated from the digitally-designed information are very huge and there are often the occurrences of the unnecessary bidirectional communications. To solve this problem, we studied on a special-purpose computer for wavefront printing technology. This technique consists of generating the light-ray information from digitally-designed information of 3D objects, converting the light-ray information to the wavefront information and generating the hologram data locally from the wavefront information in interaction. In this paper, we designed the emulator of the special-purpose computer for wavefront printing technology and obtained the amount of information (the number of bits) required for the circuit by comparing the 3D images reconstructed from the holograms generated by the emulator. As a result, the amount of information of the wavefront information converted from the light-ray information most affected the quality of the 3D images reconstructed from the holograms generated by the emulator and we can design the emulator that can reduce the noise component from those 3D images. In the future, we will design the special-purpose computer for wavefront printing technology by using hardware description language and implement that special-purpose computer on a programmable logic device such as a field programmable gate array.
KEYWORDS: Projection systems, Holography, Optical design, Heads up displays, Digital holography, Displays, LCDs, Collimation, 3D displays, Holographic optical elements
A see-through light-field 3D display that works in head-up configuration is being presented. The display system consists of only a commercial projector and a holographic screen and works on the principle of Integral Imaging. The holographic screen is a volume hologram that is digitally fabricated, which functions as a micro concave- mirror array. The screen also has other optical functions embedded that helps to eliminate the bulk of optical components needed otherwise. This significantly simplifies the system, there by taking it closer to the consumer market. A color 3D scene of size 20cm x 10cm x 5cm (depth) has been successfully reproduced and can be seen through naked eye for a viewing angle of 10-degrees.
KEYWORDS: Holography, Wavefronts, Printing, 3D displays, 3D printing, Electromagnetism, Communication engineering, Communication and information technologies, Photonics, Electro-optical engineering
A hologram of a scene can be digitally created by using a large set of images of that scene. Since capturing such a large amount is infeasible to accomplish, one may use view synthesis approaches to reduce the number of cameras and generate the missing views. We propose a view interpolation algorithm that creates views inside the scene, based on a sparse set of camera images. This allows the objects to pop out of the holographic display. We show that our approach outperforms existing view synthesis approaches and show the applicability on holographic stereograms.
In this paper, we introduce hologram printing technology. This technology includes the following technologies, computer-generated hologram, hologram printer, duplication, and application-depended technologies. When this technology is applied to static hologram, the media can present static 3D objects more clearly than traditional 3D technologies such as lenticular lens and integral photography(IP) because it is based on holography. When this technology is applied to holographic optical elements(HOE), the HOE will be useful for many purposes especially for large optical elements. For example, when it is used as screen, the visual system which consists of the screen and projector can present dynamic 2D or 3D objects. Since this technology digitally designs hologram/HOE and manufactures them by wavefront printer, it is good at generating small lot of production. As a result, it is effective for the research stage of both 2D and 3D display. In addition, it is also effective for commercial stage due to simple duplication method.
Several wavefront printers have been recently proposed. Since the printers can record an arbitrary computer-generated wavefront, they are expected to be useful for fabricating complex mirror arrays used in front projection 3-D screens without using real existing optics. We prototyped two transparent reflective screens using our hologram printer in experiments. These screens could compensate for a spherically distorted reference wave caused by a short projection distance to obtain an ideal reference wave. Owing to the use of the wavefront-printed screen, the 3-D display was simply composed of a normal 2-D projector and a screen without using extra optics. In our binocular system, reflected light rays converged to the left and right eyes of the observer and the crosstalk was less than 8%. In the light field system, the reflected light rays formed a spatially sampled light field and focused a virtual object in a depth range of ±30 mm with a ±13.5-deg viewing angle. By developing wavefront printing technology, a complex optics array may easily be printed by nonprofessionals for optics manufacturing.
This paper presents a fast calculation method for spherical computer-generated hologram by using a spherical harmonic transform. A three-dimensional (3D) object defined in the 3D Cartesian coordinate system is numerically Fourier transformed with fast Fourier transforms (FFTs). Fourier components on the spherical surface of the radius 1/λ are extracted. The wavefronts on the spherical surface can be calculated from the single spherical Fourier components. This paper reveals the analytical diffraction integral between the spherical Fourier components and the wavefront on the spherical surface. This diffraction integral is expressed in the form of convolution integral on the sphere and can be calculated very fast based on the spherical harmonic transform. By the numerical simulation, the validity and the effectiveness of our proposal has been verified.
A Fizeou interferometer with instantaneous phase-shifting ability using a Wollaston prism is designed. to measure dynamic phase change of objects, a high-speed video camera of 10-5s of shutter speed is used with a pixelated phase-mask of 1024 × 1024 elements. The light source used is a laser of wavelength 532 nm which is split into orthogonal polarization states by passing through a Wollaston prism. By adjusting the tilt of the reference surface it is possible to make the reference and object beam with orthogonal polarizations states to coincide and interfere. Then the pixelated phase-mask camera calculate the phase changes and hence the optical path length difference. Vibration of speakers and turbulence of air flow were successfully measured in 7,000 frames/sec.
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