Wei-Chia Su

Distortion aberration correction device fabricated with liquid crystal lens array

A distortion aberration (DA) correction device is fabricated using a liquid crystal lens array (LCLA), which is placed at the intermediate image plane of the optical system. Without voltage, the LCLA does not work, the image is distorted due to the aberration from the optical system; with voltage, the incident light is focused by the LCLA and then the distorted image is corrected. The correction of distorted image by LCLA is attributed to the redirection of the off-axis propagated chief ray approaches the principal point of the lens element.

Full Color Image Splitter Based on Holographic Optical Elements for Stereogram Application

A color holographic beam splitter (CHBS) applied to an autostereoscopic display is proposed in this study. With high-stability polymer-dispersed-liquid-crystals (PDLC) being the holographic materials, holographic grating is utilized as a full-color beam splitter to split left and right field of views (FOVs) of a stereoscopic display. When CHBS is attached, the experimental results show that the correct left/right FOVs images could be successfully obtained at the preset observing distance of 25 cm. Moreover, the diffraction efficiency of the red, green and blue (RGB) left/right FOVs of the PDLC materials remained at 30.0% on average. Apparently, the brightness efficiency of the proposed CHBS stereo-displays is better than the traditional stereo-displays with a parallax barrier (22.4%). In addition, a crosstalk contrast with 95.0% indicates the crosstalk problem is almost avoided in the proposed technique.

Effect of recording-beam ratio on diffraction efficiency of polarization holographic gratings in dye-doped liquid-crystal films

The +1 order diffraction of polarization holographic gratings generated by two linear orthogonally polarized writing beams in dye-doped liquid-crystal films were increased by using two recording beams with unequal intensity. The maximum diffraction efficiency of the polarization holograms in our experimental sample can reach 23% when the intensity ratio of two recording beams is 7:1, and this value is almost triple that when the intensity ratio of two recording beams is 1:1.

Design of a novel symmetric microprism array for dual-view display

Abstract This research is to design a microprism array optical film which can be attached on 2.2-in. liquid crystal displays. The sizes of the base width of the microprism and the sub-pixel of the panel were corresponding. After the selection of the appropriate vertex angles, two images could be delivered to left and right viewing zones of the panel. This research also used flexible material polydimethylsiloxane (PDMS) with high transmission as the optical film. Besides, it utilized LightTools software to process the ray tracing, which obtained the left and the right images, respectively, delivered to the visual angles of −47.5 to +16.5° and −11.5 to +48.5°. Slight crosstalk only located within −31.5 to −25.5° and +28.5 to +30.5°, respectively. It shows that the microprism sheet can actually make general panels have dual-view display function.

Switchable holographic image splitter fabricated with dye-doped liquid crystals.

Two electrically controllable holographic polarization gratings are spatially multiplexed to serve as an image splitter for further stereogram application. An external AC voltage is used to modulate the diffraction efficiency of the fabricated holographic image splitter for the switching of a 3D stereogram and a 2D plane image. The polarization grating was generated by two writing beams with orthogonal circular-polarization state in dye-doped liquid crystal films. With proper experimental arrangements, a quasi single order diffraction was obtained and the other non-zero order diffractions were suppressed in this presented polarization grating. This characteristic leads to a good image contrast ratio for a stereogram. Finally, a switchable stereogram system using circular-polarization beam as backlighting was demonstrated successfully.

Effect of a diffuser on distortion reduction for a virtual image projector

Distortion aberration of a virtual image generated by a projection lens system is reduced by a diffuser. This technique is implemented by putting a diffuser on the intermediate image plane in the imaging system. Theoretical simulation and experimental imaging results of the proposed technique are analyzed and demonstrated.

Design and fabrication of quartz-based micro prism array of dual-view display by using reactive ion etching

In this paper, a quartz-based micro-prism array structure is newly proposed as the parallax barrier, and such a device is designed only for fitting the size of a 2.2 inch LCD panel, the most popular size for the TV on mobile phone. The optical simulation software LightTools was applied to verify whether the designed structure can work or not. The parameters we considered including the viewing angle, viewing distance, vertex angle of prism, refractive index of quartz (=1.46) and the sub-pixel width (=66 μm). 1,000,000 rays emitted from the dual view display panel are simulated, as the result, our designed quartz-based micro-prism array structure can successfully separate images from odd or even sub-pixels into two different viewers and the view angle is indeed 80° as our requirement. The key to control the red, green, blue light from different sub-pixels can be precisely guided into the same direction is ascribed to the arrangement of the vertex angles of the relative prisms (R:47.1°, G:47.2 °, B:47.4 ° ). Three steps of lithography and the reactive ion etching can fabricate the precise angle and size of our needs. The left and right images generated by our designed dual-view display are quite pellucid without color difference, and very similar to our simulation.

Dye adsorption induced nonvolatile reading of erasable polarization holograms in liquid crystal films

A nonvolatile reading of erasable polarization holograms in dye-doped liquid-crystal films using the same writing wavelength is presented. The recorded hologram can be easily erased with the illumination of one p-polarized wave; nevertheless, it becomes nonvolatile when reading the hologram with one s-polarized wave. We have proven the nonvolatile reading property is induced by dye adsorption on the substrate of the sample.

Three-dimensional/two-dimensional convertible display based on computer-generated holograms and an amplitude-modulated spatial light modulator

Abstract. A three-dimensional/two-dimensional (3-D/2-D) convertible display was proposed. The display system offers 2-D images via the traditional display technology and offers 3-D images via the computer-generated hologram (CGH) technology. In this system, 2-D and 3-D images are generated from the same amplitude-modulated spatial light modulator (SLM). In the 2-D display mode, the panel displays an amplitude-modulated image and the 2-D image is projected on a polarization-dependent diffuser (PD) screen. In the 3-D display mode, the SLM panel displays CGHs to generate 3-D images. The zero-order diffraction of the amplitude-type CGH will be blocked by a spatial filter (SF), which is designed by a polarizer. Furthermore, a liquid crystal element was employed to modulate the polarization state of the reconstructed light to let the 3-D image quality not to be reduced by the PD. Finally, the proposed system can offer 2-D and 3-D images both clearly. The system suppresses the zero-order diffraction noise of the amplitude-type CGH system successfully.

Two-color holographic recording in a single-doped photorefractive LiNbO3 crystal

b National Changhua University of Education, Graduate Institute of Photonics, No. 1, Jin-De Rd., Changhua 500, Taiwan, R.O.C. Abstract. We recorded a hologram in a photorefractive LiNbO3:Fe crystal with a two-color recording technique in transmission geometry. The holographic recording involves a light with wavelength 633 nm for interference, and a light with wavelength 532 nm for exciting. The short wavelength light excites more charges so that the holographic recording is affected, and the storage capacity M-number and the sensitivity vary accordingly. We found that the optimized in- tensity ratio of the interference lights and the exciting light is between 50 and 60. In the optimized conditions, the M num- ber and the sensitivity are enhanced by 43 and 35%, respec- tively. Because the crystal we used is a typical iron-doped LiNbO3 crystal and the short wavelength exciting light source is inexpensive now, the proposed method is easy to