Archived posting to the Leica Users Group, 2001/07/24
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Austin writes: > If you want to detect a line that has a > width of 0.009mm, which is the width of the > line in a 53 lp/mm set, which is 106 lines, > you need to sample at slightly more than > 2x that, or < .0045 mm/sensor in order to > detect the line RELIABLY, ie, every time. Exactly 2x is fine. > Your are flawed in thinking that you can > detect a .009mm line with a .009mm wide sensor > RELIABLY. You haven't defined what you mean by "reliably." > Draw a picture for your self, and you will > see that if you make your line pairs which are > 0.009mm per line, straddle the .009mm sensors, > such that 1/2 of a line is over one sensor, > and 1/2 over the other, you may not detect any > lines at all, you will get gray. The gray _is_ the detection of the line; it is gray because the line is only half present in each pixel. This is exactly the expected result, and it corresponds to true detection of the lines. > Please think about this before replying. I've > spend the past 20+ years designing digital > imaging systems...so this is not just an academic > exercise for me. I've spent the same amount of time working with information theory, and I know exactly whereof I speak. Keep in mind that a practical understanding and a theoretical understanding are not necessarily coincident, nor is one necessarily a subset or superset of the other.