Papers by Keyword: Optical Microstructures

Abstract: A novel optical sheet with double-layer microstructures is proposed to improve the brightness uniformity and optical efficiency in the LED direct-lit backlight module. By means of 2D ray-tracing program design and commercial optical software simulation, we enhance the brightness uniformity from 45.3% with traditional planar diffuser to 82.7% with new optical sheet, and the average brightness is promoted about 10.9% in the same frame of backlight module which internal thickness is only 13mm. Thus, this novel optical sheet with microstructures design is useful for a slim LED direct-lit backlight module.

Abstract: Effects of some alloying additives such as Cr, Co, Ni, Mn, Al on the microstructures, resulting fracture surfaces of bronze base bonds and diamond composites as well as the bonding between the metal bonds and diamond grits were studied. Experimental results revealed that under the hot pressing conditions sufficient alloying couldn’t develop as it does in the cast bronze. The degree of segregation varied with the melting point of the alloying elements. The metal with higher melting point led to a more serious segregation. Addition of strong carbide formation elements like Cr, Co could improve the bonding between the metal bonds and diamond grits and the retension of metal bond for diamond was enhanced in a way. However the addition of Al, Mn and Ni did not bring much improvement on the bonding between the metal bonds and the diamond grits.

Abstract: This paper presents a study of effect of cutting conditions on surface quality in FTS machining of optical microstructures such as micro-lens array. A power spectrum analysis is proposed to characterize the surface quality in FTS machining. It is found that there is a strong relationship between the surface roughness and the power spectrum of the surface profile. This provides an important means for the characterization of surface quality in FTS machining of optical microstructures.

Abstract: In this paper, a framework of surface generation model in the fast tool servo (FTS) machining of optical microstructures will be described. The integrated model is totally composed of a tool path generator (TPG), a surface topography model (STM) and an optimization model (OM). To develop the tool path generator, two parts should be involved. The first part is the tool path generated based on cutting conditions such as the feed rate and spindle speed, the geometry of optical microstructures, and diamond tool geometry. Another part is the synchronized motion generated by the tool actuation of the FTS at a bandwidth higher than the rotational frequency of the spindle. The surface topography model will be generated based on the TPG and used to predict the technological aspects of FTS machining. It takes into the account the kinematic and dynamic characteristics of the cutting process. The former includes the tool path generated by the tool path generator. The later includes the relative vibration between the tool and the workpiece caused by the axial error motion of the spindle as well as the synchronized motion of the FTS system. The optimization model will be undertaken by an iterative algorithm, which will be developed based on the TPG and STM. The OM will be expected to output the verified tool path, the suggested optimum cutting conditions, and the diagrams with predicted cutting performance characteristic and process parameters being investigated. Eventually, the successful development of this surface generation model can contribute for the knowledge of ultra-precision machining with FTS and the further development of the performance of the machining system.

Abstract: The fabrication of high-quality optical microstructural surfaces is based on fast tool servo (FTS) machining. It makes use of auxiliary piezo-electric driven servos to rapidly actuate the diamond tool with a fine resolution and a sufficiently high bandwidth for machining optical microstructures with submicrometer form accuracy and a nanometric surface finish without the need for any subsequent post processing. However, the achievement of a superior mirror finish and form accuracy still depends largely on the experience and skills of the machine operators, acquired through an expensive trial-and-error approach to using new materials, new mircostructural surface designs, or new machine tools. As a result, this paper, a model-based simulation system is presented for the optimization of surface quality in the FTS machining of optical microstructures. Preliminary experimental work and the results are also presented.