Nonplanar photolithography with computer-generated holograms

We outline a method for accomplishing photolithography on grossly nonplanar substrates. First we compute an approximation of the diffraction pattern that will produce the desired light-intensity distribution on the substrate to be patterned. This pattern is then digitized and converted into a format suitable for manufacture by a direct-write method. The resultant computer-generated hologram mask is then used in a custom alignment tool to expose the photoresist-coated substrate. The technique has many potential applications in the packaging of microelectronics and microelectromechanical systems.     

Nonlinear computer-generated holograms

We propose a novel technique for arbitrary wavefront shaping in quadratic nonlinear crystals by introducing the concept of computer-generated holograms (CGHs) into the nonlinear optical regime. We demonstrate the method experimentally showing a conversion of a fundamental Gaussian beam pump light into the first three Hermite-Gaussian beams at the second harmonic in a stoichiometric lithium tantalate nonlinear crystal, and we characterize its efficiency dependence on the fundamental power and the crystal temperature. Nonlinear CGHs open new possibilities in the fields of nonlinear beam shaping, mode conversion, and beam steering.     

Three-dimensional displays using computer-generated holograms

A hologram of a three-dimensional object is synthesized by a computer using the technique of holographic stereograms. A sequence of perspective views of an object is calculated and their Fourier transform holograms are synthesized by a computer. Each hologram is arranged in the order of the view points to produce the final composite hologram. The experimental reconstruction of the three-dimensional object can be successfully performed.     

Improved double-phase computer-generated holograms implemented with phase-modulation devices

A modification of the double-phase holographic code, based on phase modulation devices, that substantially improves the signal-to-noise ratio in the reconstruction plane without the need to increase the complexity of hologram cells (or macropixels) is proposed.     

Wavefront-linearization in construction of computer-generated holograms

The application of computer-generated holograms for 3-D information handling requires reconstructions of image details at finite distances from the hologram plane. To calculate the hologram structure Huygens' principle may be used. To treat this problem in an alternative mathematical way a linearization was introduced. The effects of such a procedure are evaluated and illustrated with analytical and optical reconstructions.     

On-axis computer-generated holograms for three-dimensional display

The feasibility of on-axis synthetic near-field amplitude holograms for three-dimensional display applications is demonstrated. An iterative optimization algorithm is used that generates an object-dependent diffuser that utilizes the phase and, to some extent, amplitude freedoms in the reconstruction plane. The discrimination between twin images and undiffracted terms is thus improved. The on-axis approach presents important advantages: a low coherence requirement for the illuminating source, a lower spacebandwidth and higher viewing angle than with the off-axis alternatives. Defocusing and parallax are experimentally attained with an extended white-light source and a lensless setup.     

利用合成谱在计算全息图中编码多个物体的方法

 提出在迂回位相傅里叶变换计算全息图中利用合成谱记录多个物体的方法。该方法利用多个物体合成的傅里叶频谱,代替传统的迂回位相型计算全息图中的单一频谱,在一幅计算全息图中完成多个物体的编码。再现时多个物体同时再现在同一衍射级的周围,并且再现像的形式可以多种多样。采用液晶空间光调制器(LC SLM)完成计算全息图的光学再现,实验验证了方法的有效性。结果表明：该方法可有效提高计算全息图的信息容量。     

Improvement of 1D off-axis computer-generated holograms

Creation of Fresnel off-axis computer-generated holograms and improvement of images reconstructed from the holograms are described. To improve the reconstructed images, we have created the holograms with high construct diffraction patterns by using a histogram method. From reconstruction experiments of the holograms, clear images have been obtained and 3D images have been seen directly with eyes.     

Two-channel computer-generated holograms: a simplified method

A simplified approach is presented, to obtain two-channel computer-generated holograms of detour type. The method allows effectively to handle up to two flat objects (two digitized images), in x and ydirections. The experimental results demonstrate the effectiveness of the suggested procedure.     

Using computer-generated holograms to test cubic surface

Computer-generated holograms (CGH) have been widely used to evaluate symmetrical aspherical surfaces in combination with Fizeau interferometers. Because the CGH can create any wavefront shape, it can also be used in unsymmetrical aspherical surfaces testing. Taking the cubic surface as an example, this paper gives a thinking of testing unsymmetrical surfaces. First we deduce the expression of the aberration for the cubic phase when propagating and the CGH null lens design has been carried out while taking into consideration the higher order aberrations. The separation of the diffraction orders of the CGH is discussed. We fabricated the CGH using e-beam photography and tested a 13-mm diameter cubic surface.     

Simple computer-generated holograms displayed by an x-y plotter

New simple computer-generated holograms displayed by an x-y plotter are proposed and investigated. In the construction of holograms by computer, phase coding methods are used in order to distribute the Fourier-transform values of an original object over the whole of the receiving plane where the hologram is to be constructed. It is found that relatively good images are reconstructed from the computer-generated holograms proposed here.     

Phase coding in iterative synthesis of computer-generated holograms

A new method is investigated for phase-only hologram synthesis. The method combines iterative calculation of the hologram phase function with the coding of the amplitude-phase characteristics of the complex transmission function into phase characteristics. The results of computational experiments are presented. The phase masks and reconstructed object images are also presented.     

Diffraction-limited laser beam shaping by use of computer-generated holograms with dislocations

A new method that reshapes a Gaussian laser beam into a polygon of diffraction-limited size with a flat or a pyramidal top is presented. The technique is based on the use of computer-generated holograms with phase dislocations (singularities).     

Optical particle trapping with computer-generated holograms written on a liquid-crystal display

Computer-generated holograms written on a liquid-crystal display can be used to generate dynamic light fields of arbitrary shape. This method was used to simultaneously trap polystyrene particles laterally and to displace them independently of one another.     

Color representation method using RGB color binary-weighted computer-generated holograms

We propose a method for color electroholography using a simple red–green–blue(RGB) gradation representation method without controlling the respective brightness of the reference RGB-colored lights. The proposed method uses RGB multiple bit planes comprising RGB binary-weighted computer-generated holograms with various light transmittances. The object points of a given three-dimensional(3D) object are assigned to RGB multiple bit planes according to their RGB gradation levels. The RGB multiple bit planes are sequentially displayed in a time-division-multiplexed manner. Consequently, the proposed method yields a color gradation representation of a reconstructed 3D object.     

A new theta modulation multiplexing scheme for computer-generated holograms

In this paper, a new theta modulation multiplexing scheme for producing multiplexed computer-generated holograms (CGHs) is proposed. Under this scheme, normal Lohmann-type CGHs are individually modulated by gratings with different orientations and then superimposed to form a single hologram. The proposed method results in a higher storage capacity without the increase of hologram space. Theoretical analysis and experimental results are presented.     

The use of commercial fine-grain films for computer-generated holograms

The possible use of commercial fine-grain films for computer-generated binary holograms is described. Three different types of film are used. Image quality improves with film resolution but if the resolving power is higher than a minimum value needed for the phase level resolution, the contrast (γ value) of the film has a pronounced effect on the quality of the image reconstructed optically from the hologram. The possible generation of binary holograms by computers with reduced central memory is also studied.     

Embedded birefringent computer-generated holograms fabricated by femtosecond laser pulses

Birefringent computer-generated holograms are fabricated in bulk fused silica by tight focusing of infrared femtosecond laser pulses. The polarization properties of the elliptically polarized diffracted light are in excellent agreement with the theoretical model. We experimentally demonstrate that for such birefringent structures the signal-to-noise ratio increases by approximately 9 dB when polarization filtering is used to suppress the undiffracted beam.     

Reconstruction from computer-generated holograms displayed by a line printer

Experimental results are shown of optically reconstructed images from computer-generated holograms made with only binary-quantized levels in the real parts of the Fourier-transform complex disturbance of a signal and displayed by a line printer. Relatively good images having no distortion due to the high-pass filtering effect are reconstructed from computer generated holograms multiplied by the random phase factor. Reconstruction is also possible from the present holograms for signals having various degrees of light intensity.     

Problems on fabrication of computer-generated holograms for testing aspheric surfaces

Interferometric optical testing using computer-generated hologram （CGH） can give highly accurate measurement of aspheric surfaces has been proved. After the system is designed, a phase function is obtained according to the CGH＇s surface plane. For the requirement of accuracy, an optimization algorithm that transfers the phase function into a certain mask pattern file is presented in this letter, based on the relationship between the pattern error of CGH and the output wavefront accuracy. Then the writing machine is able to fabricate such a mask with this kind of file. With that mask, an improved procedure on fabrication of phase type CGH is also presented. Interferometrie test results of an aspherie surface show that the whole test system obtains the demanded accuracy.