Re: Galvo Lasers and Photos in General.
Posted: Wed Mar 21, 2018 7:19 pm
Tweaky:
I should probably have written something about power and photos before. There is a
relationship between speed and power to be considered in doing any photo. Auggie
can only change power for each waypoint, which in a Pokeys is 1ms. So we have
only 1000 chances per second to change power level. If a laser were to do a 500
ms sweep across a raster line, we have a resolution of only 500 pixels really.
So sweep speed is really a tradeoff of resolution and speed. Worse, we have only
100 power levels in a Pokeys in waypoint changes. Thats 95 with tickle levels taken
out. If you slide requested power to 50%, thats only really 45 differing levels. Tonal
scale will then suffer if not using as high as possible a power, but that means to not burn
one has to go faster, and that limits the resolution. Its all quite a fine balancing act to
get good tonal balance.
I see only two ways to fix this to get the most realistic photo possible in an
engraving. First we need more levels of power. Say.. 1000 to choose from. The new
mode stops at each point and uses time, so making 1000 levels isnt hard if one
considers both power and time that power is applied in ms. This means if one uses
50% power, then you still have 500 levels of that 50% so the tonal variation would
still be maximized ( the photo only has 255 levels itself..without using supersampling
of the image data... more on that later if everything else works out. ).
Energy accumulation is another way, multiple scans using different power per pixel
on each scan to create an accumulated power that achives a higher tonal range per pixel
datum. This is almost the same as stopping at each pixel, but a bit harder to calculate
the end energy effect, though the calculation of each pass for energy is trivial as a
calculated sum.
Im finding in my testing that too much laser power is an issue, you go too slow
and you burn, too fast and you lose resolution due to the 1ms limit. If I limit
to 6% power to get a good grey scale, thats only 6 levels in reality, I need
100% power to get 100 levels of grey..but then Id burn. This is all a system of
tradeoffs. Im thinking to maximize performance, a multipass energy summing
calculation for total energy per pixel over X passes would make the most sense for the
highest tonal range in a photo. Or at least thats what the math and testing is telling
me. Testing continues.
Art
I should probably have written something about power and photos before. There is a
relationship between speed and power to be considered in doing any photo. Auggie
can only change power for each waypoint, which in a Pokeys is 1ms. So we have
only 1000 chances per second to change power level. If a laser were to do a 500
ms sweep across a raster line, we have a resolution of only 500 pixels really.
So sweep speed is really a tradeoff of resolution and speed. Worse, we have only
100 power levels in a Pokeys in waypoint changes. Thats 95 with tickle levels taken
out. If you slide requested power to 50%, thats only really 45 differing levels. Tonal
scale will then suffer if not using as high as possible a power, but that means to not burn
one has to go faster, and that limits the resolution. Its all quite a fine balancing act to
get good tonal balance.
I see only two ways to fix this to get the most realistic photo possible in an
engraving. First we need more levels of power. Say.. 1000 to choose from. The new
mode stops at each point and uses time, so making 1000 levels isnt hard if one
considers both power and time that power is applied in ms. This means if one uses
50% power, then you still have 500 levels of that 50% so the tonal variation would
still be maximized ( the photo only has 255 levels itself..without using supersampling
of the image data... more on that later if everything else works out. ).
Energy accumulation is another way, multiple scans using different power per pixel
on each scan to create an accumulated power that achives a higher tonal range per pixel
datum. This is almost the same as stopping at each pixel, but a bit harder to calculate
the end energy effect, though the calculation of each pass for energy is trivial as a
calculated sum.
Im finding in my testing that too much laser power is an issue, you go too slow
and you burn, too fast and you lose resolution due to the 1ms limit. If I limit
to 6% power to get a good grey scale, thats only 6 levels in reality, I need
100% power to get 100 levels of grey..but then Id burn. This is all a system of
tradeoffs. Im thinking to maximize performance, a multipass energy summing
calculation for total energy per pixel over X passes would make the most sense for the
highest tonal range in a photo. Or at least thats what the math and testing is telling
me. Testing continues.
Art
