focus in versus focus on

When using (focus) as a verb, we always use (focus on) and we do not use (focus in).
See the definitions/examples from the dictionary:
http://hk.dictionary.yahoo.com/search.html?s=focus
vt.
1. 使聚焦[(+on)]
2. 調節(鏡頭等)的焦距[(+on)]
You can focus your telescope on that distant television tower.
你可以對著那座遠方的電視塔調節望遠鏡的鏡頭。
3. (調節鏡頭的焦距)使(圖像等)清晰
4. 使集中[(+on)]
I can't focus my thoughts today.
今天我的思想集中不起來。
vi.
1. 聚焦
A defect of vision prevented him from focusing accurately.
視力上的缺陷使他不能準確對焦。
2. 調節焦距[(+on)]
3. 集中[(+on)]
The beams of light moved across the sky and focused on the plane.
光束在空中移動,集中對準飛機。

I have tried my best to help you.


2007-10-15 20:21:17 補充：
However, if you use (focus in), it might be accepted as the same meaning as (focus on).

2007-10-18 18:06:21 補充：
幫到你嗎?

focus in is different from focus on.