Finite-difference time-domain 계산 방식을 사용한 모바일 광학계 성능 분석: The performance analysis of a mobile optical system using Finite-difference time-domain method

by Jeong-Soon Kang (MS Candidate)

Wednesday Nov 18, 2015, 1:50 PM → 2:15 PM Asia/Seoul

216-1호Kang (제1과학관)

The development of information and communication technology has brought the advent of smart phone. The performance and function of smart phone camera has grown up enough to replace traditional camera market. For example, the advanced DSLR(digital single-lens reflex) camera technologies such as phase difference auto-focus, image stabilization and high-sensitivity image sensor were integrated into a smart phone camera.
However, some technical problems have not yet been solved. The relationship between the resolution and the pixel size becomes a major problem as the pixel size has shrunk to diffraction limit.
The reduction of pixel size can lower resolution because of the decreased quantum efficiency and the increased cross talk. FDTD(Finite-difference time-domain), beam propagation and ray tracing were used together to analyze this problem. FDTD is a numerical analysis technique used for computing EM(electro-magnetic) wave with accuracy. FDTD can simulate the exact behavior of EM wave in a nano-structure such as CMOS image sensor.
At first, the ray tracing and BSP(Beam Synthesis Propagation) function in Code V was used to calculate the beam spot at the plane right before the micro-lens in an image sensor of 8 Mega pixel(pixel size 1.4μm). Next, the phase information obtained from Code V was transferred into FDTD software to calculate EM wave from the micro-lens to the photodiodes of image sensor. In this manner, the effect of micro-lens on the pixel was investigated. The kind of simulation enables the optimization of the parameters related with micro-lens such as the radius of curvature and the lens shift depending on the field angle. The analysis also includes the calculation about the cross talk between the pixels and the corresponding change of MTF(modulation transfer function) as a function of optimization parameters.

Thesis Advisor: Prof. Young-Gu Ju