Du-Hwan Cha

Fabrication and optical evaluation of aspheric glass lenses for 3 megapixel zoom camera phone module

The purpose of this study is to develop aspheric glass lenses 4mm in diameter by compression molding. The lens is intended for use as an optical design of 3 megapixel and 2.5 magnifications zoom in a camera phone module. Because of the excellent optical performance of glass and aspheric element, which minimize optical aberrations, the adoption of optical designs using of aspheric glass lenses is rapidly increasing with the progress of precision image forming optics. We fabricated the mold using ultra-precision processing of tungsten carbide (WC). The aspheric glass lens was precisely molded and then its characteristics were evaluated. The mechanical and optical properties of the molded lens were investigated and it showed 90–95% transcription ratio and 0:0655λ root-mean-square optical path difference (OPD-rms), which corresponds to a 0.844 Strehl ratio. Based on the optical performance using the Marechal criterion, we supposed that the molded lens is suitable for the optical design. It also means our fabrication process is available.

A Study on Pressing Conditions in the molding of Aspheric Glass Lenses for Phone Camera Module using Design of Experiments

This study investigated the pressing conditions in the molding of aspheric glass lenses for the mega pixel phone camera module using the DOE method. Tungsten carbide (WC; Japan, Everloy Co., 002K),which contained 0.5 w% cobalt (Co), was used to build the mold. The mold surface was ultra-precision ground and polished, and its form accuracy (PV) was 0.85um in aspheric surface. We selected four factors, pressing temperature, force and time of first step, and force of second step, respectively, as the parameters of the pressing process. in order to reduce the number of experiments, we applied fractional factorial design considering the main effects and two-way interactions. The analysis results indicate that the only two main effects, the pressing temperature and the time of pressing step 1, are available for the form accuracy (PV) of the molded lens. The analysis results indicated that the best combination of the factors for lowering the form accuracy(PV) value of molded lens was to have them at their low levels.

Fabrication and Evaluation of Chalcogenide Glass for Molding

In this study, we synthesized the chalcogenide glass() for infrared optics by meltquenching method and verified the effect of cooling condition on the glass properties. The structural and optical properties of the glass were analyzed by XRD, FT-IR and SEM image. The glass synthesized under the cooling temperature of shows transmittance of 58% at , which was decreased as the cooling temperature was decreased. In addition, thermal and hardness also were measured. From the analysis results, we ascertained the feasibility as a molding materials for infrared optics.

Ultraprecision Grinding of Glassy Carbon Core for Mold Press Lens

In this study, glassy carbon was ground for lens core of glass mold press. Ultraprecision grinding process was applied for machining of core surfaces. During the process, brittle crack occurred because of hard-brittleness of glassy carbon. Author investigated optimized grinding conditions from the viewpoint of ductile mode grinding. Geometrical undeformed chip thickness was adopted for critical chip thickness that enables crack free surface. Machined cores are utilized for biaspheric glass lens fabrication and surfaces of lens were compared for verification of ground surface.

Fabrication and Evaluation of Biaspheric Glass Lenses for a 3-megapixel Camera Phone Module

Recently, advanced industrial elds, such as semiconductors, image information and optoelectronics, have been developing and expanding, resulting in an increased demand for lighter optical devices. Aspheric glass lenses have many optical advantages in terms of two aspects: i) the glass has superior optical performances and ii) the aspheric form reduces optical aberrations. This paper reports a complete fabrication process using a glass molding press for and evaluates biaspheric glass lenses for a 3-megapixel camera phone module. The molded lens shows a transcription ratios of around 88.1 % in the incident surface of the lens and 80.5 % in emission surface of the lens. Note that the transcription ratio is the percentage of the form accuracy between the mold and the molded lens.

Study on pressing conditions in the molding of aspheric glass lenses for phone camera module using design of experiments

Recently, the application of aspheric glass lenses is rapidly expanding due to the availability of mass production employing the glass molding press(GMP) process. To date, the GMP process has been regarded as one of the reliable methods in fabrication of aspheric glass lenses. However, it has been found that there are some difficulties during the process to control many parameters (e.g. molding temperature, pressing time and pressing force, etc). Design of experiments (DOE) is one of the solutions to properly control these parameters and a useful tool in the process and analysis of complicated industrial design problems. This study investigated the pressing conditions in the molding of aspheric glass lenses for the mega pixel phone camera module using the DOE method. The fractional factorial design is applied and the form accuracy (PV) of the aspheric surface of the molded lens is employed as a response variable. The analysis results indicate that the only two main effects, the time of pressing step 2 and the force of pressing step 1, are available for the form accuracy (PV) of the molded lens. It is the optimum condition among the designed pressing conditions for lowering the form accuracy (PV) value that all factors are at their low levels. The form accuracies (PV) of the mold and molded lens under the optimum condition are 0.181 um and 0.22 um, respectively.

Optical Properties of Aspheric Glass Lens using DLC Coated Molding Core

In this research, the optimal grinding condition has been obtained by design of experiment (DOE) fur the development of aspheric lens for the 3 Mega Pixel, 2.5x optical zoom camera-phone module. Also, the tungsten carbide (WC) mold was processed by the method of ultra precision grinding under this optimal grinding condition. The influence of diamond-liked carbon (DLC) coating on form accuracy (PV) and surface roughness (Ra) of the mold was evaluated through measurements after DCL coating using ion plating on the ground mold. Also, aspheric glass lenses were molded, some before DLC coating of the mold and some after the DLC coating. The optical characteristics of each sample, molded by the different molds, were compared with each other.