Chien-Yue Chen

Novel Wearable and Wireless Ring-Type Pulse Oximeter with Multi-Detectors

The pulse oximeter is a popular instrument to monitor the arterial oxygen saturation (SPO2). Although a fingertip-type pulse oximeter is the mainstream one on the market at present, it is still inconvenient for long-term monitoring, in particular, with respect to motion. Therefore, the development of a wearable pulse oximeter, such as a finger base-type pulse oximeter, can effectively solve the above issue. However, the tissue structure of the finger base is complex, and there is lack of detailed information on the effect of the light source and detector placement on measuring SPO2. In this study, the practicability of a ring-type pulse oximeter with a multi-detector was investigated by optical human tissue simulation. The optimal design of a ring-type pulse oximeter that can provide the best efficiency of measuring SPO2 was discussed. The efficiency of ring-type pulse oximeters with a single detector and a multi-detector was also discussed. Finally, a wearable and wireless ring-type pulse oximeter was also implemented to validate the simulation results and was compared with the commercial fingertip-type pulse oximeter.

Novel Noninvasive Approach for Detecting Arteriovenous Fistula Stenosis

Hemodialysis is the most common treatment for patients with end-stage renal disease. For hemodialysis, consistently functional vascular access must be surgically created with an anastomosis of artery and vein, referred to as an arteriovenous fistula (AVF). However, AVF dysfunction may occur over time. Angiography and Doppler ultrasound are usually used to detect the flow or the diameter of the AVF. But they require well-trained operators and are expensive, and even angiography is invasive. In this study, a noninvasive approach based on stethoscope auscultation for monitoring AVF stenosis was proposed. Here, a wireless blood flow sound recorder was designed to record blood flow sounds wirelessly. In order to effectively extract the varying feature of blood flow sounds for AVF stenosis, the 2-D feature pattern built from S-transform was also proposed as the feature in the AVF stenosis detecting algorithm. Different from other frequency-related coefficients, the feature pattern can contain the information of blood flow sounds in time and frequency domains simultaneously. Preliminary findings showed that the proposed approach can provide high-quality estimation of AVF stenosis (positive predictive value = 87.84% and sensitivity = 89.24%).

A high-brightness diffractive stereoscopic display technology

In this research, the diffractive blazed grating was proposed to produce the stereoscopic effects that were traditionally generated by barrier grating through parallax barrier method. Three wavelengths, 596 nm, 554 nm and 450 nm, were chosen as the main light waves for three sub-pixels, RGB. Because the diffractive optical element was directly attached to the color filter of a MPEG-4 player (Motion Picture Experts Group Four Player, MPEG-4 player) panel, the stereoscopic image remained high brightness. Since lithography would be the most possible manufacturing method, multilevel approximation was to proceeded during simulation. From the simulated results of optical simulation software, LightTools, the RGB lights moved parallelly and consequently avoiding cross-talk.

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.

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.

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.