reduced image distance的意思|示意

折合像距 ... 焦点 1.[数学] [物理学] (二次曲线焦点; 主焦点) focal point; focus 虚焦点 virtual focus; 主焦点 principal focus; 焦点分散 defocus2.(问题的关键所在或争论的集中点) central issue; centre; point at issue 斗争的焦点 the focus of the struggle; 矛盾的焦点 focal points of contradictions; 问题的焦点 the heart of the matter; 争论的焦点 the points at issue3.[气象学] origin4.[冶金学] (焦斑) focal spot 折合像距,换算像距 reduced image distance 二点外推 two points extrapolation ...