Microscope for Milling Maching

[TorontoBuilder]

the size of the error depends on the distances between the reticle, the object being viewed and the viewer and the shift away the viewer is from the perpendicular.

In perfectly aligned scope in the bore of the mill there should be no theoretical error because the point being viewed is inline with the bore, the reticle and the viewer. But imperfect alignment of the beam splitter that splits the beam to send the view to the eyepiece will induce parallax error as will misaligned cross hairs.

Think of it this way... a hunter looks through his scope, lines up a deer in the crosshairs, and pulls the trigger. He misses what appeared to be a perfect shot in still air because his eye was 2 mm to the right of the center of the scope. You can adjust the scope for the range you are shooting so that there is no parallax error when you move your head out of alignment slightly.

 

[Dabbler]

Parallax can be solved in shooting scopes by using what is called front field optics (or sometimes called front focal plane) - where the cross hairs are in the same focal plane as the image. The disadvantage with this, is in zoom scopes, where the thickness of the cross hairs changes with the magnification.

In optical comparators, this is fixed by putting the reticle on the projected surface, or the final focal plane.

The nice thing about a camera with digital cross hairs, is they are easily adjusted to the true centre of rotation, by translating them across the image digitally.

 

[Chicken lights]

Parallax can be solved in shooting scopes by using what is called front field optics (or sometimes called front focal plane) - where the cross hairs are in the same focal plane as the image. The disadvantage with this, is in zoom scopes, where the thickness of the cross hairs changes with the magnification.

In optical comparators, this is fixed by putting the reticle on the projected surface, or the final focal plane.

The nice thing about a camera with digital cross hairs, is they are easily adjusted to the true centre of rotation, by translating them across the image digitally.

Ahhh, so parallax isn’t needed on FFP scopes as the cross hairs don’t change? Non FFP scopes that do change the parallax is needed to clear up the crispness of the cross hairs?

Speaking for camera use, of course

 

[Dabbler]

The focus in a front focal plane scope is in a different part of the mechanics. Another problem is depth of field.... Not a problem in a machining microscope.

The recicle focus is a result of factory adjustment. the image waaay out there still needs to be focused.

 

[Chicken lights]

The focus in a front focal plane scope is in a different part of the mechanics. Another problem is depth of field.... Not a problem in a machining microscope.

The recicle focus is a result of factory adjustment. the image waaay out there still needs to be focused.

good thing I just like taking pictures with a camera

thanks for helping explain the mechanics

 

[thestelster]

As an example of parallax error:

-find a spot on the wall (screw of a light switch cover.) This is your target
-with your arm outstretched point at it with your finger so that it is just very close to the screw but not touching. Your finger is the cross hair.
-as you're aiming at the target, move your head slightly to the left and to the right. (There should be no visual displacement)
-now bring your finger (cross hair) very close to your eye, and point at your target. Move your head slightly left and right. (There will be a large visual displacement)

Many scopes, especially with large magnification, will have a means to correct for this parallax error. It's usually a knob on the side. In the old days it was a ring on the front objective lens. By adjusting the knob or ring, it moves image of the target to be in the same focal plane as the cross hair.

 

[Chicken lights]

As an example of parallax error:

-find a spot on the wall (screw of a light switch cover.) This is your target
-with your arm outstretched point at it with your finger so that it is just very close to the screw but not touching. Your finger is the cross hair.
-as you're aiming at the target, move your head slightly to the left and to the right. (There should be no visual displacement)
-now bring your finger (cross hair) very close to your eye, and point at your target. Move your head slightly left and right. (There will be a large visual displacement)

Many scopes, especially with large magnification, will have a means to correct for this parallax error. It's usually a knob on the side. In the old days it was a ring on the front objective lens. By adjusting the knob or ring, it moves image of the target to be in the same focal plane as the cross hair.

For cameras, I was told to remove the centre part of the milling attachment, look though the bore of the milling attachment, and try to sight the camera on the same piece of paper to line both up, to get camera shots on decent paper

I will try your camera aiming technique, with both cameras
thanks!

 

[DPittman]

For cameras, I was told to remove the centre part of the milling attachment, look though the bore of the milling attachment, and try to sight the camera on the same piece of paper to line both up, to get camera shots on decent paper

I will try your camera aiming technique, with both cameras
thanks!

Yes that works well but there are electronic bore sighters that are available cheap that will get your milling attachment right on paper to start with a bit more ease.