Guo-Dung Su

Progressive addition lens design by optimizing NURBS surface

Progressive addition lenses (PAL) are used to compensate presbyopia, which is induced by losing accommodation of elder eyes. These eyes need different optical power provided by eye glasses while watching objects at different distance. A smaller optical power is required in further distance and a larger one in nearer zone. A progressive addition lens can provides different power requirements in one piece of lens. This paper introduces a whole process of PAL production, from design, fabrication, to measurement. The PAL is designed by optimizing NURBS surface. Parameters of merit function are adjusted to design lenses with different specifications. The simulation results confirm that the power distributes as expected and cylinders are controlled under an acceptable level. Besides, sample lenses have been fabricated and measured. We apply precise-machining to produce the molds for plastic injection. Then, the samples are produced by injecting polycorbonate to the molds. Finally, Ultra Accuracy 3D Profilemeter is used to measure the sample PALs. Practical examinations shows that our designs are achievable and feasible in practice use.

Free-form lens for laser level system

We design a free-form lens, which can reshape a Gaussian green laser beam into a top-hat irradiance distribution over the target plane. We measure the laser beam profile of every part of this green laser beam shaping module. The divergence angle of the green laser module is not wide enough for laser level system. We can get a wider divergence angle of the green laser beam system when adding the beam shaper and the cylindrical lens. The divergence angle of the green laser level system is about 120° and the uniformity of the green laser level system is about 91.08%.

Cylindrically symmetric Fresnel lens for high concentration photovoltaics

High concentration photovoltaic (HCPV) utilizes point-focus cost-effective plastic Fresnel lens. And a millimeter-sized Ill-V compound multi-junction solar cell is placed underneath focusing optics which can achieve cell efficiency potential of up to 40.7 %. The advantage of HCPV makes less solar cell area and higher efficiency; however, the acceptance angle of HCPV is about ±1°, which is very small and the mechanical tracking of the sun is necessary. In order to reduce the power consumption and the angle tracking error of tracking systems, a light collector model with larger acceptance angle is designed with ZEMAX®. In this model, the original radially symmetric Fresnel lens of HCPV is replaced by cylindrically symmetric Fresnel lens and a parabolic reflective surface. Light is collected in two dimensions separately. And a couple of lenses and a light pipe are added before the solar cell chip in order to collect more light when sun light deviates from incident angle of 00. An acceptance angle of ±10° is achieved with GCR 400.

Focus tunable mirrors made by ionic polymer-metal composite

In order to meet modern requirement, electronic products are made smaller and thinner. We used deformable mirrors (DMs) in optical systems that can make camera modules thinner and lighter in electronic products. An Ionic-Polymer Metal Composite (IPMC) plays the critical role in our design of deformable mirrors. It has good bending feature and can be driven by low voltage (usually less than 5 volts). Other technologies such as liquid lenses, MEMS deformable mirrors, and liquid crystal lens, all need higher voltage to reach similar optical power of IPMC. After fabrication of IPMC deformable mirrors, we used PDMS on one surface to improve the surface roughness before reflective metal is deposited. Key characteristics of IPMC deformable mirror are demonstrated in the paper. By coating a silver layer on the smoothed IPMC surface, the reflection is up to 90%. From simulation results, the zoom ratio of this module can be expected 1.8 times. Experimentally, the deformable mirror can be changed from flat to 65 diopters (m-1) by only 3 volts. In this paper, we demonstrated a reflective optical zoom module with three mirrors and two deformable mirrors.

High efficient polymer dispersed liquid crystal for ultra-bright projected image

Head-up display (HUD) commonly uses liquid crystal to generate images. However, the intensity of the light decreases a lot because of passing through the polarizers. Therefore, polarizer-free display is a way to enhance the light efficiency. We demonstrate the feasibility of using Polymer Dispersed Liquid Crystal (PDLC), which consists of polymer and liquid crystal, as an optical switch to fabricate a simple see-through projected display device. Due to the unique E-O characteristics of PDLC, it can be a role to define the projected image shape. In our device, we use the ultra-bright collimated LED as a backlight source so that the projected image can also be seen clearly in broad daylight. Besides, PDLC do not need to utilize polarizers. It is achieved to obtain very high light efficiency (~70%). In this paper, we show some results of projected images with various colors (RGB) that can be applied to see-through projected display. From our experiment result, the see-through projected display device by PDLC can achieve high contrast ratio (~1000:1) and response time is about 15~20 ms. The driving voltage is around 20~25 V. Further improvement can be achieved by optimizing the LC material/monomer concentration or others parameters.

Ionic polymer metal composite to achieve optical zoom function in a compact camera

Nowadays, there are many popular electronic devices consist of optical focus zooming systems. It is the trend to minimize optical systems in portable devices. For this purpose, we used deformable mirrors in optical systems that can make them thinner and lighter. The Ionic-Polymer Metal Composite (IPMC) is the critical component in our design of the deformable mirror. It has good bending feature and can be driven at low voltage (less than 5 volts). The IPMC fabrication processes contain three steps: acid clean, initial compositing process and surface electrode plating process. After the IPMC is completed, we coated the PDMS on the surface to improve the surface roughness. Then we deposit silver on one side as a reflective surface to finish our deformable mirror. Some characteristics of the IPMC deformable mirror would be demonstrated in the paper. By coating the PDMS on the IPMC surface, the surface roughness can be reduced to about 20 nm. The reflection of the silver layer is up to 90%. In our design, we make the reflective optical zoom module which consists of three biconic mirrors and two deformable mirrors. When we applied voltages on deformable mirrors, the reflective light is successfully focused after the deformation of elliptic IPMC. The zoom ratio of this module can be expected to 1.8 times. The deformable mirror can be changed from flat to 65 diopters (m-1) by about 3 volts.

CMOS compatible IR sensors by cytochrome c protein

In recent years, due to the progression of the semiconductor industrial, the uncooled Infrared sensor – microbolometer has opened the opportunity for achieving low cost infrared imaging systems for both military and commercial applications. Therefore, various fabrication processes and different materials based microbolometer have been developed sequentially. The cytochrome c (protein) thin film has be reported high temperature coefficient of resistance (TCR), which is related to the performance of microbolometer directly. Hence the superior TCR value will increase the performance of microbolometer. In this paper, we introduced a novel fabrication process using aluminum which is compatible with the Taiwan Semiconductor Manufacture Company (TSMC) D35 2P4M process as the main structure material, which benefits the device to integrate with readout integrated circuit (ROIC).The aluminum split structure is suspended by sacrificial layer utilizing the standard photolithography technology and chemical etching. The height and thickness of the structure are already considered. Besides, cytochrome c solutions were ink-jetted onto the aluminum structure by using the inkjet printer, applying precise control of the Infrared absorbing layer. In measurement, incident Infrared radiation can be detected and later the heat can be transmitted to adjacent pads to readout the signal. This approach applies an inexpensive and simple fabrication process and makes the device suitable for integration. In addition, the performance can be further improved with low noise readout circuits.

Application of heterogeneous microlenses for solid state lighting

In recent years, LEDs were applied to general lighting in large volume, mostly in territory of backlight lighting. Therefore, our research would focus on backlight lighting.In this paper, one method was adopted to obtain freeform surface with non-axial symmetry. Then by the freeform lens constructed by us, we would make the light field intensity more uniform. At the second part of the paper, we would utilize heterogeneous micro lens array (MLA) to approximate the shape of the freeform lens, and adjust the curvature radius and size of the micro lenses, and the arrangement way of the micro lens by the simulation results. Through repeated trials, we could achieve a uniformlight intensity of LEDsusing microlenses and the thickness of direct-lit backlight unit is 2 mm thick.

Transparent image generator by using vertically aligned polymer-stabilized liquid crystal (VA-PSLC) for see-through display applications

We demonstrate the feasibility of using a Vertically-Aligned Polymer-Stabilized Liquid Crystal (VA-PSLC) film, which is also known as LC gel, as a transparent image generator to form a see-through display system. This is achieved, in its simplest form, by projecting a collimated LED light source onto a transparent glass screen, with the image generated by the scattered light from the VA-PSLC. By moving the observer’s head slightly away from the incident light specular reflection direction, a clear image can be observed on the transparent glass screen together with the background objects that are behind the screen. From our experimental results, this see-through display system using VA-PSLC transparent image generator can achieve a fast response time (with rise time of ~10 ms and fall time of ~5ms) and an acceptable contrast ratio (< ~100:1). The driving voltage is about 15~20V. Further improvements can be achieved by further optimizing the LC material/monomer parameters, device fabrication process/conditions and the optical system setup. In this system, polarizers are not required so that very high light efficiency can be obtained.