Let's say that you have a Peak microscope that is designed for 20x to 300x magnification.
How does helicoid focusing mechanism provide accuracy? Can someone explain this to me as I've never heard this before. I thought most focusing mechanisms were one form of rack/pinion or another.
Helicoid focusing mechanism...how accurate is it?
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benjamind2014
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steveminchington
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A helicoid is essentially a large screw thread. It is how older manual camera lenses focus. The accuracy of focus would depend on how fine the thread is or how many 'starts' the thread has. Some helicoids have several concentric helixes and can move a long distance in one turn.
Most microscopes use a rack and pinion to focus, which by itself is quite coarse, but fine focus down to 1 micron is achieved by using a system of gears to reduce the movement of the rack.
Most microscopes use a rack and pinion to focus, which by itself is quite coarse, but fine focus down to 1 micron is achieved by using a system of gears to reduce the movement of the rack.
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enricosavazzi
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I never heard about Peak microscopes, so I will only make general comments.
Let's assume that the helicoid has only one helical thread (just like an ordinary screw), one extending barrel, and a thread pitch of 0.5 mm (which is on the low side of what is normally feasible to machine).
This means in practice that the distance between subject and optics changes by 0.5 mm, or 500 micron, per turn of the focusing ring of the helicoid.
Compare this to the fine focus knob of most good microscopes, which changes this distance by 100 or 200 micron per turn.
Add to this the fact that a focusing ring coaxial with the optics is ergonomically not optimally placed to allow a precise operation, while the fine focus knob in most microscopes is. If there is no coarse focus and only the one helicoid, factor this into the inconvenience of operation.
Edit: after googling "Peak microscope" I found their site. They are portable inspection microscopes, so the are not meant as an alternative to lab microscopes, hence the completely different level of performance compared to the latter.
Let's assume that the helicoid has only one helical thread (just like an ordinary screw), one extending barrel, and a thread pitch of 0.5 mm (which is on the low side of what is normally feasible to machine).
This means in practice that the distance between subject and optics changes by 0.5 mm, or 500 micron, per turn of the focusing ring of the helicoid.
Compare this to the fine focus knob of most good microscopes, which changes this distance by 100 or 200 micron per turn.
Add to this the fact that a focusing ring coaxial with the optics is ergonomically not optimally placed to allow a precise operation, while the fine focus knob in most microscopes is. If there is no coarse focus and only the one helicoid, factor this into the inconvenience of operation.
Edit: after googling "Peak microscope" I found their site. They are portable inspection microscopes, so the are not meant as an alternative to lab microscopes, hence the completely different level of performance compared to the latter.
--ES