Better focus info to handle backlash compensation


I have been tracking the latest betas and am at and focusing has worked pretty well with robofocus on the primary of Edge11 SCT. As long as you have the focus direction set properly and you have perhaps 30-60 seconds (time) of backlash compensation - I get good and repeatable focus curves. There is no issue with donuts because I am close to focus anyway.

But the whole experience could be much more informative and save time if changes were made to accommodate systems with long time to unwind backlash - and it wouldn’t really affect other users.

Here are the issues. Let’s say you have 500 steps of backfocus and your focus curve is +/-100 - and your focus is at 1000.

  1. When you start autofocus you are near 1000 already - so the first thing it does is go to 1600 (1000+100+500) which takes a long time. But that’s fine - you have to do it.
  2. Then you come back to 1100 and begin taking the focus curve - moving down to 900
  3. Once you finish at 900 you have done the calculation and you know what the new focus position is - but you don’t say what it is and you don’t ask if it is acceptable. You also don’t ask at that point if you want to repeat. But if you did these things it would save a huge amount of time.
  4. Instead - it goes from 900 to about 1500 to unwind backlash - then comes back to around 1000 and finally displays the new focus value - after moving to it - and at that point asks if you want to re-run it.
  5. In addition - once focus finishes you still have a flashing dialog saying “autofocus is running” and another dialog with gray buttons that says “autofocus is complete.” The net effect is that it is hard to tell autofocus has actually finished because the flashing green progress bar makes it look like things are running.

So my main suggestions are:

  1. As soon as you finish the curve and are at 900 (on the left) - display the new focus value - both numerically and with a vertical line on the screen - and at that point ask if it should be repeated. If so, you only have to unwind backlash once - not twice - which is a huge savings. You also know immediately what the new focus value is.
  2. In addition I would turn off the flashing green progress bar - or do something to make it clear autofocus is complete.

I think the value of these changes would be clear if you used a system with long backlash compensation. Not all systems have such an issue - but it is an important issue for sct focusing - and the above changes would also be valuable for setups with little backlash.

I include a log for reference - but there is nothing specific in it other than examples of autofocus and the timings.

sg_logfile_20151018201844.txt (924.4 KB)

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Tentatively moving to 2.5.X because I would like for the bulk of the AF refactor to be complete before we alter any of the current AF logic.