The s and t formulae for holographic lens elements

By considering the propagation of an astigmatic wavefront through a hologram on a curved surface expressions for the distances to the principal foci are obtained. In the special case of a system with a plane of symmetry these reduce to expressions similar to the conventional refraction/reflection s and t formulae.     

Bifocal-polarization holographic lens

We present a holographic lens with novel features recorded in an azopolymer film. Two holographic modulations, bulk birefringence and surface relief, are induced in the medium at the same time. The resultant holographic element has two focal planes, and the polarization of light in the focal points depends on the polarization of the incident light. Applications of this device for writing-reading information in two planes simultaneously or separately are described.     

Testing of holographic optical elements for holographic gun-sight

Conventional methods of measuring the various parameters of holographic optical elements are tedious for mass production. A novel approach is described for the holographic elements used in the holographic sight, in which the parameters are defined and measured as per their intended final application. Since the holographic sight is used for accurate target acquisition along with the other features, parallax in the sight becomes a critical parameter. Besides, the maximum brightness of the reticle is another parameter of the device, which is important for the use of sight in the strong sunlight in summers. There are two holographic elements, namely holographic reticle and holographic lens in the sight. Both can be tested in a simple set-up in terms of the parallax of the sight and the brightness of the reticle. The masters for both elements are required to be benchmarked once and rest of the elements in a mass production can be tested with the reference of masters.     

全息透镜的焦距测量

本文首先给出了全息透镜像散成像的焦距公式,介绍了用全息光栅法测量全息透镜焦距的原理,对两块自制的全息透镜在原光路再现情况下测量了其焦距,并用另一种参数测量方法对测量结果进行了验证,两者基本相符。通过分别测量全息透镜两个焦距,从而可得出其像散大小。最后指出了使用这种方法应注意的问题。     

Space-variant filtering with holographic multifacet elements

We present a spatial filtering method for space-variant operations. The method is based on the combination of a holographic lenslet array and an appropriate filter array. The lenslets produce local Fourier transforms of the object which are filtered in parallel and independently by the spatial filters. The most obvious space-variant setup based on lenslet arrays would consist of many narrow 4f-setups, arranged side by side. The total object would be partitioned into many small object patches, as many as there are lens elements in the lenslet array. However this setup shows the undesired effect of local inversion. Therefore we choose a setup with only one lenslet array and an imaging lens which avoids the local inversion.     

Computer-generated holographic optical elements produced by photolithography

We report the creation of novel computer-generated holographic optical elements. The method of computing diffraction gratings producing a continuous focal pattern in the form of a line and also gratings that have N orders in a row of equal energy is described. The method has also been developed for coding the filter-complex transmittance functions in order to form and analyze the transverse modes. All the above elements are realized as glass-substrate binary-phase refractive holograms by projection photolithography by using photoreduction. The minimum line width is 2·5 mkm. These elements may also be fabricated as reflective holograms.

Phot-masks and the results of an investigation of the intensity distribution produced by the elements are presented. The investigation results confirm the synthesized elements' high quality.     

Color holographic zoom system based on a liquid lens

In this Letter, we propose a color holographic zoom system based on a liquid lens. We use the spatial multiplexing method to realize color reconstruction. By controlling the focal lengths of the liquid lens and the encoded digital lens on the spatial light modulator panel, we can change the magnification of the reconstructed image very quickly, without mechanical parts and keeping the output plane stationary.     

用全息光学元件实现对眼睛的激光防护

反射式全息滤光片具有很好的滤光特性,可作为一种激光防护元件.本文对这种元件的波长选择性,角度选择性,所能承受的功率密度进行分析,并讨论了实际应用的可能性.     

DCG全息元件的简化处理及特性研究

本文提供了重铬酸明胶（ＤＣＧ）的一种简化处理步骤，最高衍射效率和透明度均达９７％，测量和分析了处理后ＤＣＧ光栅的衍射特性，讨论了高质量ＤＣＧ全息元件的应用。     

A flat field holographic lens with no first order astigmatism

By a suitable choice of the position of the stop, holographic lenses which are free from first order astigmatism are obtained. Furthermore it is found that these lenses are flat field for all pairs of conjugates for all field angles.     

Reflection holographic lens having nonspherical wavefront designed by a microcomputer

A design of a reflection holographic lens with nonspherical wavefront is described, which is based on a ray-tracing program and a simple search algorithm suitable for a microcomputer. The optimized wavefront is encoded into a computer- generated hologram (CGH). The reflection holographic lens with the optimum wavefront produced by CGH reduces the rms spot radius at large field angles, and allows for a compact folded system and for Bragg diffraction into a single order. Experimental results are shown. Helpful data on the diffraction efficiency and the spectrally diffracted intensity of reflection holograms are presented.     

Simplified processing and characteristic investigation of DCG holographic elements

In this paper,the simplfied procedures of processing dichromated gelatin(DCG)holographic optical elements(HOE's) are presented.Both diffraction efficiency and transmis-sion of DCG grating made by the procedures have been achieved up to 97%.The diffractioncharacteristics of the DCG gratings are measured and analysed,the applications of DCG grat-ings with high quality are also discussed.     

Compact photonic delay line constructed by holographic optical elements

To fully support phased-array antenna and other applications, a 3-range (long time, moderate time, and short time) delay line structures with holographic optical elements is proposed. Flexibility, light-weight, on-axis coupling, easy alignment, easy fabrication, and compactness are their advantages. When use holographic optical elements to build the photonic delay line system, all of the delay and non-delay paths in these three photonic delay lines are setting in a compact structure. They do not need any extra components, such as mirrors and optical paths in free space, and can bear stronger vibration. Therefore, the holographic optical elements are more suitable to design the photonic delay lines. In these three structures, their losses and crosstalk s are balanced. All of delay and non-delay cases in these three delay line structures, their crosstalk, signal-to-noise ratio, and loss are 1/81,000, 59.1 dB, and 3.2 dB, respectively. Finally, to support complete applications, a polarization independent photonic delay line system with holographic optical elements is proposed, too.     

Modified phase contrast for recording of holographic optical elements

A modified phase contrast method is described for the fabrication of holographic optical elements with in-line diffraction patterns. In this method, a liquid crystal phase modulator is addressed by computer-generated holograms to achieve variable phase gratings. The phase gratings are imaged onto photosensitive material by a phase contrast method without a Fourier filter. We show the analytical treatment of the modified phase contrast method and demonstrate the application in holographic recording.     

Experimental evaluation of entropy for transmission holographic optical elements

An experimental study of transmission holographic optical elements is presented. Several important aspects related to the diffractional analysis of these elements have been considered. The case of the spherical object wave is analyzed in detail. The emphasis is on obtaining the entropy from the intensity distribution on an image plane. We use the calculated entropy to locate experimentally the position of the best image plane in the sense of minimal aberrations for a holographic lens. The comparison of experimental and theoretical results is presented and good agreement between theory and experimentation has been obtained.Part of this paper was presented at the IS & T/SPIE symposium in Electronic Imaging, Science and Technology (Practical Holography IX) February 4–10, 1995, San José, CA, USA     

Investigation of a free convective current using holographic interferometry

By the method of holographic interferometry in real time, an investigation is carried out of the development of free convective currents in an enclosed cavity filled with different liquids exposed to heat fluxes from either linear or point sources. Characteristic times of the processes are measured. Temperature fields in the current are plotted.     

Light-induced lens analysis in photorefractive crystals employing phase-shifting real-time holographic interferometry

The purpose of this work is to study the potentialities of phase-shifting real-time holographic interferometry for the analysis of light-induced lens in photorefractive and nonlinear optical materials. We show that this technique can be used for quantitative evaluation of the phase distribution of a wavefront changed by a light-induced lens and, consequently, the refractive index changes in these materials. The basic principle of this technique combines real-time holographic interferometry with phase-shifting technique for interferogram analysis. This method is demonstrated with in situ visualization, monitoring and analysis in real-time and uses a Bi₁₂SiO₂₀ crystal as the holographic medium and a Bi₁₂TiO₂₀ as the test sample.     

Demultiplexer based on an off-axis holographic lens with low monochromatic aberrations

A novel scheme is proposed,in which the aberrations in the off-axis holographic lenses used as demultiplex-ers are reduced to a low enough level for relatively small channel spacing. The scheme includes optimizing the recording and reconstruction geometries and collimating the reconstruction wave with a gradient-index lens. A demultiplexer operated in the 1 550-nm band with 5-nm channel spacing and ∞-dB crosstalk is obtained using the scheme. The channel spacing can be decreased to 2 nm by etching the cladding of the output fibers to a smaller size.     

电控聚合物分散液晶全息透镜及特性研究

报道位相型电控聚合物分散液晶(H-PDLC)全息衍射透镜的研制及特性研究,理论上,根据耦合波理论,研究了不同的相分离程度系数下,理想位相型电控聚合物分散液晶(H-PDLC)全息衍射透镜在可见光波长(400—800nm)的衍射特性.实验研制了衍射效率最高为70%的电控H-PDLC变焦透镜样品,研究表明H-PDLC透镜具有优良的成像特性,和快速响应的电控开关特性,在光学成像系统,光通信系统中具有良好的应用前景.     

等倍变焦全动型变焦距物镜理论分析

变焦系统是一种焦距可以连续变化而像面保持稳定的光学系统。而全动型变焦距物镜是一种新型的变焦系统 ,它的各组元垂轴放大率在变焦运动过程中保持相等。对等倍变焦全动型变焦距物镜做了理论分析 ,并推导出一套切实可用的高斯光学公式