Qing-Long Deng

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.

Binary blazed grating based on autostereoscopic display mechanism

The diffractive optical element blazed grating is proposed as the beam splitter for autostereoscopic displays in this study. With Lithographie Galvanoformung Abformung and inductively coupled plasma reactive-ion etching, a four-level blazed grating structure is produced. Moreover, highly translucent polydimethylsiloxane is transformed into symmetrical four-level blazed grating films. The experimental results show that the film can successfully transmit the left and the right images to the accurate positions, and the diffraction efficiency is 70.4% and the contrast ratio is above 80%, presenting the original stereoscopic image without it being affected by brightness and crosstalk. In the experiment of stereoscopic imaging, both the left and the right images could be clearly acquired, which proves the feasibility of blazed gratings as practical for the beam splitter of autostereoscopic displays.

A hybrid temporal and spatial speckle-suppression method for laser displays

We propose a system that reduces laser display speckles by vibrating the light pipe. A small displacement of the light pipe appears to allow the total reflection of the laser, thereby resulting in a homogenized speckle field that changes with time. In this case, the speckle interference generated by the pattern projected by the laser through the light pipe destroys the spatial homogenization of the laser beams when the light pipe is vibrated. Moreover, when the light pipe begins the sequential vibration, the phases and paths of the beams are changed after the beams traverse the light pipe. Consequently, temporal speckle wavefront superposition can homogenize the luminous intensity distribution of the speckle pattern. This process reduces the speckle contrast to less than 4% while maintaining a luminous intensity of greater than 70%.

Panoramic stereo photography based on single-lens with a double-symmetric prism

Different from traditional panorama stereo acquisition technique shooting with numerous cameras, this study equips a double-symmetric prism in front of a single-lens camera to acquire images from four different angles of view, and the images acquired from the cameras every 20 degrees complete a pair of panorama stereo images with vertical angle of view ( ± 16 degrees) by image-based rendering. The panorama stereo acquisition technique reduces the number of cameras by three-fourth, and the acquired images contain vertical angles of view. Moreover, the image resolution is enhanced several times of the resolution of integral photography without moiré effect.

Quartz-Blazed Grating Applied on Autostereoscopic Display

By applying reactive ion etching (RIE) to a blazed grating on quartz substrates, the grating can be utilized as a splitter in autostereoscopic displays. Furthermore, a solution for the pattern alignment on transparent substrates is also proposed. By measuring the diffraction efficiency and crosstalk between the left and right fields of view (FOV), the capability of the element to deliver stereoscopic images is demonstrated.

Integral computer-generated hologram via a modified Gerchberg-Saxton algorithm

An integral computer-generated hologram, which modulates the phase function of an object based on a modified Gerchberg–Saxton algorithm and compiles a digital cryptographic diagram with phase synthesis, is proposed in this study. When the diagram completes position demultiplexing decipherment, multi-angle elemental images can be reconstructed. Furthermore, an integral CGH with a depth of 225 mm and a visual angle of ±11° is projected through the lens array.

MGSA-Type Computer-Generated Holography for Vision Training With Head-Mounted Display

A computer-generated holography head-mounted display (HMD) for vision training is proposed in this study. Based on modified Gerchberg-Saxton algorithm (MGSA) to calculate the phase distribution of light wave and the position multiplexing, the images with fixation disparity or changed disparity are successfully coded as phase only function. After decryption and reconstruction, the left and the right images are transmitted to HMD for a trainee viewing the images with disparity changes and moderating the stereoacuity of both eyes, ranging from 32.24 arcsec to 2.14 arcmin. The images reconstructed with MGSA-type CGH present the relative diffraction efficiency about 86% and visibility 94%, which not only provide high-contrast image quality, and the changing disparity allows achieving the training effect.

Pulfrich autostereo display with micro-prism array

A micro-prism film, with spectral characteristics, is attached on a display panel to show images appearing with + 10° ~ + 50° and -10° ~-50° bright regions and with a + 10° ~-10° dark region. When both eyes separately receive the bright region and the dark region of an image, interocular delay would appear to generate a stereo perception. With the optical simulation software, LightTools 7.3.0, to simulate the brightness change, the light with lower brightness appears on the 0° region and the light with the highest brightness appears on the ± 10° region. The optimal viewing distance of 25 cm could accurately deliver the image with shading parallax to both eyes. The actual measurement of brightness presents the shading distribution, achieving the condition of binocular retinal illumination, and the angle of visibility appears on the ± 50° region, causing interocular delay so that the viewer generates the stereo perception.

Design of head-mounted-display eyepiece system of liquid crystal on silicon

The research is aimed at designing an optimized head-mounted-display (HMD) system equipped with two 0.26-inch Liquid Crystal on Silicon display elements for imaging. In order to form an image at a distinct-vision distance of 250 mm, the eyepiece system features 17-times magnification, a 15.63-mm focal length and a 15° field of view. Using the resolution of the human eye as the evaluation standard, we analyze the diminution of aberration and the increase of modulation transfer function, giving the HMD system high resolution as the finishing touches.