Re: Single or multi hole off-axis filters?

From: Brian Tung (brian_at_isi.edu)
Date: 06/10/04 

Date: Thu, 10 Jun 2004 00:21:44 +0000 (UTC)

Jon Isaacs wrote:
> So how accurately do the holes have to be cut to provide that alignment?

Each hole creates two images, each image separated by 90 degrees from the
hole, in a manner of speaking. So if the holes in a two-hole mask are
separated by 150 degrees instead of 180 degrees, you end up with two
pairs of images, each separated by 30 degrees.

Since the out-of-focus images are bloated, the alignment has to be off
quite a bit before you see four distinct images with a two-hole mask.

Brian Tung <brian@isi.edu>
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