针孔望远镜？

[zzz]

zzz, 你的設計, 只能在沒有波動性質的情況下使用.
由於光有波動特性, 越小的針孔, 繞射的問題越嚴重.
但是針孔大的話, 卻會使影響模糊.

已有前人導出一個對於某波長的光線, 某個焦距之下, 最適合的針孔大小, 公式在維基百科找到:


另外, 當針孔大小與它的材料厚度相約(或更小)的時候, 臨邊昏暗的問題會變得更嚴重.

大小是相对的，就是有足球场那么大的孔也不是不可以成像的。分辨率是要看我们需要多大的分辨率，在一定的研究需求下，我们未必非要看清楚月亮上的蚂蚁不可。

[zzz]

Dear Mr. Poon,

Thanks for your response. I think you are talking about a pinhole camera but not a pinhole telescope.

Pinhole camera and pinhole telescope are two different things.

Pinhole camera is a very interesting science project and the physics behind it is very beautiful - infinite depth of view and not very slow speed in DAYTIME use. In fact I had been conducting numerous physics projects with my students constructing pinhole cameras. the reults were stunning and rewarding. The strength of pinhole camera - extreme wide angle ( we were using curved film ) and unlimited depth of view. I was using film at those days and with CCD camera nowadays pinhole camera will be much more easy to construct.

However pinhole telescope is another thing - we need to magnify the image by an eyepiece. It contradicts what a telescope requires - resolution and light grasp. It's correct that by adjusting the length of the tube we zoom the telescope but I can hardly imagine what I would see inside the eyepiece. In the rare case of pointing the scope towards sun we may get sufficient luminosity but, sadly, the resolution problem evolves.

May be that in some very specific application a pinhole telescope ( not a pinhole camera ) is found useful. In general I can't see how a pinhole can satisfactorily perform telescopic works, though it beautifully accomplishes a camera's job.

Best regards
Chan Yuk Lun

其实我说的是拍摄，未必非要用眼睛来直接的“看”，用针孔拍拍摄比如说太阳月亮之类的，当然更远的星系未必比可以拍摄。而这也是在望远，是吧？