共查询到20条相似文献,搜索用时 437 毫秒
1.
2.
3.
A new method is presented for constructing a computer-generated Fourier-transformed line hologram using an xy plotter. Phase and amplitude of the complex amplitude in the hologram plane are represented by varying, respectively, the position and height of triangles formed in the cells composing the hologram. An image reconstructed optically from the hologram can be moved arbitrarily from the optical axis since the hologram contains information about the phase and amplitude of the complex amplitude in the hologram plane. A three-dimensional hologram from which an image was successfully reconstructed is also presented. 相似文献
4.
5.
The volume hologram is considered as a series of coupled Fabry-Perot etalon. The interference of multi beam makes the band width of volume hologram very narrow. The positive feedback of Fabry-Perot provides high diffraction efficiency of volume hologram. The computer simulations for volume hologram based on the new model shows a good consistency with the coupled wave theory and the experimental results. 相似文献
6.
This paper describes a simple method for making dual beam encoded extended fractional Fourier transform (EFRT) security holograms.
The hologram possesses different stages of encoding so that security features are concealed and remain invisible to the counterfeiter.
These concealed and encoded anticounterfeit security features in the security hologram can only be read through a key hologram.
Key hologram also facilitates in-built repositioning of security hologram. The method of fabrication, the principle of reconstruction
and the experimental results are presented.
相似文献
7.
The viewing angle of a computer-generated hologram (CGH) can be expanded by lens-less Fourier configuration. However, a laser is required to illuminate the CGH for reconstruction. We proposed earlier making a second hologram for white-light reconstruction; here, we propose a method to calculate CGH for a full-color rainbow hologram with enlarged viewing angle. First, we calculate the master hologram with three virtual slits whose positions correspond to red, green and blue wavelength. The transfer hologram can be made from the master CGH with a single exposure. In the experimental result, we obtain a full-color computer-generated rainbow hologram with 17° of viewing angle and 3.0mm × 2.5 mm image size. 相似文献
8.
9.
Spatial resolution of a dynamic hologram in a reversible photochromic medium is analyzed, with allowance made for diffusion of photochromic particles. It is shown that the bandwidth of spatial frequencies of a thin hologram decreases over time, approaching the value determined by the diffusion coefficient and the hologram recording/erasing time. The optimum relationship between the intensity of the beam that records the volume hologram and the parameters of the photochromic particles is found for which the difference between the limiting value of the bandwidth of spatial frequencies of the volume hologram and the value of the band-width of spatial frequencies of a thin hologram located in the plane z=0 is the greatest. 相似文献
10.
A new class of holography is proposed, in which (1) the evanescent part of a guided wave, or (2) the guided wave in a thin-film hologram is utilized as the reference wave and/or the illuminating one. The hologram was designated as “wave-guide hologram” and has advantages in the possibility of integration, wide field of view, and compactness and high reliability of the reconstructing system. The possibility of the waveguide hologram has been proved through reconstruction experiments with a guided wave of a waveguide hologram recorded with a plane reference wave. 相似文献
11.
在传统的纯相位全息显示系统中, 一般基于快速傅里叶变换(FFT)算法来计算相位全息图, 在FFT的计算中需要遵循Nyquist采样定理, 因此, 重建图像的尺寸往往受限于空间光调制器的固定采样率. 这个限制可以通过卷积算法或者两步菲涅耳衍射算法来解决, 但是需要使用多个FFT的计算, 导致计算量增大. 鉴于此, 提出了一种基于透镜的纯相位全息图计算方法. 在全息图的计算中, 通过透镜的成像原理建立一个采样率可变的虚拟全息面, 通过调节相应的距离参数使得在全息图的计算中可以任意调节原始图像的采样率, 摆脱了传统方法中液晶空间光调制器带宽积对重建图像尺寸的限制, 并且这种算法只需使用一次FFT就能达到变采样率的衍射计算, 大幅提高了全息图的计算速度. 数值模拟及光学实验结果证明了此方法可以在全息显示光学系统中清晰地重建不同尺寸的图像. 同时该系统可以有效地消除由空间光调制器的像素化结构带来的零级衍射. 相似文献
12.
通过分析两步法制彩色全息图中全息图空间带宽积与物体大小、全息图记录距离的关系,提出了一种拍摄大尺寸物体彩色全息图的方法。经编码,设置参数,在视窗处平面记录下三分色全息图, 以保证用最小的幅面记录下物体的完整信息,并且H1rgb处于同一平面经原参考光的共轭光再现时,他们的再现像能完全重合;将H1rgb再现,获得大视场的物光波信息,三基色物波信息重合后,用光学方法记录大幅面的彩色全息。该方法能提高全息图再现像的视场和解决大尺寸物体的全息图难拍摄问题。 经实验验证,该方法能将全息图再现像的视场提高6倍左右。 相似文献
13.
Ding Wang 《Optics Communications》2006,267(1):79-82
A true color stereoscopic hologram is made with one-wavelength laser. Under illuminating incandescent lamp, a true color stereoscopic image can be seen from the hologram. A diffused reference light and a project object light are used in the recording of the hologram. The three primary color images of natural scenery are encoded on a white-and-black film. With the help of the encoded film, a true color hologram is recorded on a plate by single exposure and a true color stereoscopic by two exposures. The simplification of this method is apparent. Further more, it largely decreases the scattering noise of the hologram and averts the problem of color lack fidelity of the holographic image. 相似文献
14.
This paper describes a method for converting a complex Fresnel hologram into a phase-only hologram that can be embedded with large amount of data. Briefly, each row of pixels in the hologram is scanned sequentially in a left-to-right direction. The magnitude of each visited pixel is set to a constant, and its phase is embedded with the data. Subsequently, the error is diffused to the neighborhood pixels. The phase hologram realized with such means, which is referred to as the data-embedded-error-diffusion (DEED) hologram, is capable of preserving high fidelity on the content of the hologram and the embedded data. 相似文献
15.
透射型彩色全息图的拍摄与再现 总被引:2,自引:2,他引:0
提出一种透射型彩色全息图的拍摄与再现技术,所再现的图象可以突出物体的三维立体感和原有色彩.同时提出一种透射型彩色全息图的象素化显示方法,并用全息光栅作为全息光学元件(HOE)进行了实验验证,这种方法特别适合于大尺寸彩色全息图的显示,它将为显示全息的广泛应用和市场开发提供一种新的方法和途径. 相似文献
16.
17.
18.
A computer-generated hologram was recorded on a thermoplastic film using an electron-beam recording device. The hologram was a binary one of detour phase type and of surface relief type. A bright image was reconstructed from the recorded hologram. 相似文献
19.
20.
在数字全息成像中, 利用CCD的RGB模式采样全息图时, 全息重构像会出现特定的周期性分布. 本文从理论和实验上详细研究了这种周期像产生的机理、分布特性和应用. 研究结果显示, 由于CCD的光谱滤镜会使全息图的RGB三个单色采样阵列出现部分像素信号的缺失, 因此, 需要通过特定的demosaicing数学算法对缺失的像素信号进行重建以形成完整的单色采样阵列, 这是数字全息再现像周期分布产生的根源. 而基于demosaicing算法的采样阵列重建会在全息图频谱中引入调制函数, 导致物体再现像和零级衍射斑的周期分布差异. 本文揭示了全息图的RGB采样、demosaicing算法与全息重构像周期性之间的内在关联. 最后, 讨论了结合空间移位和图像形态学技术, 利用重构像的周期性抑制零级衍射斑的应用. 所有理论与实验研究结果完全一致.
关键词:
数字全息
图像周期性
零级斑抑制 相似文献