Key Engineering Materials Vols. 364-366

Abstract: Operation of two-dimensional Power Spectral Density (2-D PSD) of large optics wavefront is briefly described and PSD collapse is introduced to evaluate the intermediate frequency error property of wavefront. As PSD collapse is Radon transform projection of 2-D Power Spectral Density at any angle, all valid data of wavefront of optics are used in calculation of the PSD collapse and the features of 1-D PSD were inherited in PSD collapse. Although PSD collapse is as same as 1-D PSD in unit and behavior style, it is better for evaluating intermediate frequency error property of optics wavefront than 1-D PSD or 2-D PSD. As PSD collapse calculation uses all valid data of evaluated optics wave front and can be directly perceived through its profile, the PSD collapse may possibly be the standard evaluating method of PSD.

Abstract: A high-accuracy full field 3-D surface profilometer using digital structured fringe projection is presented in the article. In the proposed method, a depth-focus response curve can be established by performing a confocal scanning along the optical axis of the measurement system when a digital fringe is controlled and projected by a digital micromirror device (DMD). To avoid specular light diffusive problems, the developed method projects spatially encoded digital fringe patterns with modulated light intensity onto a shinny lens surface, in order to achieve full field and high accuracy measurement. Some of spherical microlenses have been measured to attest the feasibility of the developed approach. The depth measurement resolution can reach up to 0.1μm and the averaged measurement error was verified to be a submicro scale.

Abstract: A novel algorithm and experiment using phase retrieval to test aspheric mirror without auxiliary optical elements has been developed. To test aspheric mirror without auxiliary optical elements, a new algorithm has been invented to overcome the calculation difficulty due to the significant departure of aspheric surface from a sphere. In this algorithm, the aspheric surface is fitted into several annular ellipse sub-apertures, and each sub-aperture aberration can be retrieved the same as ball mirror testing. The whole aspheric surface can be retrieved by stitching all the subapertures together. An experiment has been carried out to test the validity of this algorithm.

Abstract: The aspheric VCD lens is hard to fabricate by injection moulding due to its small volume and high precision requirement. The processing conditions have critical effects on the quality of the moulded lenses. An optic lens needs precisely controlled surface contours, so determination of the processing conditions for lens moulding becomes very complicated. This study’s purpose is to investigate experimentally some effects of the moulding conditions on the form errors of injection moulded lens. An aspheric VCD lens was moulded using polymethyl methacrylate. Different combinations of moulding conditions were used focusing on moulding process parameters of the ram speed, the mould temperature, the melt temperature and the packing pressure, The predicted model of form errors was formulated by orthogonal and regression analysis. Finally, the predicted model is proven to be valid based on the residual diagnostic plots.

Abstract: This study develops a highly-efficient light-guide plate for edge lighting backlight module that has no optical films. The light guide plate is designed to control the angle of the incident rays to the top surface from light source, to get the highest uniformity of intensity for thin edge lighting backlight system applications. The micro-prisms of pyramidal shape on the top surface can highly-efficient collimate with the light rays. Another micro-prism of v-cut shape on the bottom surface can reflect the incident light into the front direction and mixing the rays in the lightguide plate with the high uniformity. A novel design concept of the v-cut is the regular density varies of the cut in the LGP. The modeling simulation program, employing a Monte Carlo method based on TracePro software, has optimized the shape of the pyramidal micro-prisms on the top surface and the density distribution condition of the v-cut micro-prisms on the bottom surface, also the multiple scattering characteristics. The two types of the micro-prisms at the top and bottom surface can be highly recommended for the uniformity of the brightness via the optimal design process. Future work is warranted on improving the optical efficiency by using light-emitting diodes as a light source. The backlight module will allow us to increase the optical efficiency and to lower the total cost in portable LCD applications. The study confirms that a uniformity of brightness can be achieved without using any optical films, resulting in a high uniformity of 84%.

Abstract: A novel dual-cone-shaped side-emitting lens cap for High Brightness Light Emitting Diodes (HB-LEDs) is proposed for improving brightness and high uniformity of the direct LED backlight Units (BLUs) for large-sized LCD-TVs. Combining the designed lens cap with red, green and blue (RGB) chips on a Metal Core Printed Circuit Board (MCPCB), the LED module with the proposed cap is able to provide a compact white light source with unique features such as instant color variability and lower power usage, etc. The dual-cone-shaped of the proposed lens cap is designed to emit most of the light rays to the sides, only a small portion of light upward along the optical axis of the lens, providing a uniform luminance distribution and the high brightness on the backlight. In addition, a small reflective surface in semi-circular shape is designed and placed upon the proposed LED module about 10mm, the surfaces of which are attached with reflective films to increase the level of light mixing in the larger, global reflector optical box. With the structure of the LED module well designed, the LED backlight Module would be designed for the large-sized LCDTV using the fewer number of LEDs to lead to lower power consumption. The results indeed identify the attributes of the BLU, which make it possible to achieve excellent backlight performance using a direct illumination approach from the light source of “Dual-Cone-Shaped Side- Emitting Lens Cap of LEDs.”

Abstract: NURBS surface representation, combined with Differential Evolution (DE), enables us to perform automated non-imaging reflector design. The overall result is a simple automated nonimaging reflector design technique and only a little data such as desired illuminance distribution and searching limits are needed. Merit functions specific to non-imaging reflector design are presented. Using different merit functions, the generated illuminance distribution can be uniform as well as concentrated. DE is performed to obtain the reflector that generates the desired illuminance distribution. The photometric distributions are calculated through Monte-Carlo ray tracing and the illuminance value is used to calculate the merit function value. The validity of the proposed approach is demonstrated by optimization examples. Almost the same uniform illuminance distribution can be obtained using the algorithm proposed in this paper as that obtained by edge-raymethod. A concentrated illuminance distribution can also be generated using the algorithm proposed.

Abstract: Laser light source is a potential illumination light source for non-emissive display applications, especially for liquid crystal projection displays, due to its requirement of low etendue source and highly polarized light. In order to make a conversion from a circular Gaussian beam profile to a rectangular uniform distribution, a microlens array has been proposed as a homogenizer. The analytical and experimental results show that the microlens array with a pitch of 100um under laser beam illumination works as a diffractive element, and a promising uniformity can be obtained with a stack of two microlens array.

Abstract: A wide angle light-deflected lens combining collimation and total internal reflection (TIR) optical mechanics for LED package is proposed. Utilizing angle-dividing method the angle of emitting distribution of LED chip was cut into several angular zones and then a light-collimating curve surface with corresponding declined plane performing TIR for the collimated incident ray was designed. Thereby, the light-deflected lens, consisting of multi pairs of collimating curve surfaces and declined planes, can achieve wide-angle deflection of light emitting from LED chip. The design rule and experiment results of the lens with optimization optical design are demonstrated and discussed in this paper.

Abstract: Side-emitting LED (Light emitting diode) modulation lens is proposed here for generating planar lighting source that can be applied in many fields like LCD backlight or general lighting. The light emitted form the LED light source will be modulated by the proposed lens by the mechanism of multi-refraction. The optical simulation tool ASAP was used during the design procedure. Optimal lens dimension was designed to module 70 percent of the emitting energy to the angle range from 70 degree to 110 degree, the angle was calculated from the normal direction of the LED horizontal plane to the direction of the emitting light. The lens prototype was also fabricated and the optical performance was measured to verify the simulation results. Finally, the comparison between the optical simulation and the experiment performances is also disclosed.