투사형 전조등의 광학적 분석 = Ray tracing analysis of the projector head lamp

국문 초록 (Abstract)

투사형 전도등의 특성을 조사하기 위해 광선 추적법으로 광학계를 분석하고 그 결과를 포물경 전도등과 비교하였다. 포물경 전도등의 경우 광학계가 단순한 장점이 있지만 광원의 일부분 만을 반사하며 실제 광원의 크기와 위치를 고려할 때 높은 수차가 불가피 했다. 투사형 전도등은 여러개의 광학부품 사용하는 복잡함과 전체적 길이가 길어지는 단점이 있지만 포물경 전도등 보다 40%이상의 빛을 더 활용하며 전체적인 수차도 상당히 줄일 수 있었다. 그러나 투사형 전도등 광학계의 성능은 비구면 렌즈의 형태에 매우 민감한 것으로 나타났다.

다국어 초록 (Multilingual Abstract)

To investigate characteristics of the projection type headlights for automobiles, we used ray tracing methods and compared the results with those from parabolic type headlights.
The parabolic type headlights are simple but have two limits:
first, they require large apertures. To reflect 50% of a source light, the aperture must be 4 times of focal length and to have more reflected light, apertures must grow geometrically.
second, a parabolic mirror have large aberration when a source is away from a focus, since output of a headlight cannot be divergent, a source should locate far side from a mirror and moreover a light source has a finite size, large aberration is unavoidable.
The projection type headlights have many optical components and longer depth
compared with parabolic types, but their apertures can be made small. Advantage of using a ellipsoidal mirror is to reduce beam divergence by half and displace a focal position to another focal point, so that spherical aberration free and short focal length aspherical lens can be placed in proper position. In our study, we adopt a commercially available aspheric lens and the results were quite good compared with those from parabolic types but not optimal since output experienced total reflection at an aspheric lens. We found to improve performance of headlights, proper design of an aspheric lens was crucial.