Zeroing Scopes LOS Adjustments

[Bart B.]

Do all the common methods end up putting the LOS axis on their optical axis that's a line in the center of the main outer tube between the centers of its objective and eyepiece lenses, which, when in the mount rings, it'll also be on the ring axis?

Scope axis is line 15 in
https://patents.google.com/patent/US4643542A/en

Enlarged here
https://patentimages.storage.googlea...ngs-page-2.png

[std7mag]

So in other words Leupold has the patent on a type of focus arrangement on a scope.
I don't know if other manufacturers use the same type of arrangement.
If they do, they have to get permission from Leupold (possibly pay royalties) to use said method.

Kinda like the gun rag writer that put a patent on composite stocks with and expanding epoxy filler.

[Bart B.]

The patent applies only to the mechanics involved to hold and move the lenses. Only if another company wanted to use exactly, or very close to, the same mechanics would they need to get permission and pay royalties. And possibly the same for focal lengths of each lens. The same optical-mechanical formulas used to calculate lens properties for design objectives are used by all companies. Also applies to binoculars, telescopes, microscopes and cameras.

This Unertl patent has a different set of mechanics but the same basic lens group positions. Objective in front, erector in the middle, ocular in back.

https://patents.google.com/patent/US4247161A/en

Film and slide projectors work the same as scope sights but reversed; focusing the film image on a distant screen. Film image is reversed like a scope's first image plane so the projector doesn't need an erector lens.

Most interesting is another thing in the shooting sports where two axes need to be aligned. The way they're measured work perfectly well with scopes. Corrected the same, too. Bullet runout from case axis.

[Unclenick]

The patent is expired. Nobody needs permission now.

I think, to address the original question, the answer is, broadly speaking, yes. If you don't keep the axes coincident, edge distortion will move toward the center of the virtual image.

I should explain virtual image. The way a telescope of any kind works, you focus the eyepiece on the plane that the main objective is focussed on. If you, for example, put a sheet of paper in the focal plane of a main objective lens, standing to the side (so you aren't in the way of the image) you will see a sharp image projected onto the paper by the main objective lens. If you remove the sheet of paper, there is still a virtual image on the same focal plane, but you just can't see it when air is all there is on that focal plane because air is transparent rather than reflective, as the paper is. Now imagine the paper is back in place and the eyepiece focussed on it from behind. Then, when the paper is removed, the eyepiece will be focussed on the virtual image and will see a clear, sharp image put there by the main objective lens.

So, now, looking through the eyepiece, suppose you started to tilt the main objective. The focal plane would move along an arc equal to the focal length in radius, and you would be looking at the image at an angle through the main objective. This will distort it some and tend to make brightness uneven if this is a simple convex lens. If it is a flat field lens, like a photographic enlarger lens, designed to project a flat, undistorted image of a flat object or a very distant field of view onto a flat surface, then tilting the main objective will also cause you to have to refocus the eyepiece. None of that is desirable in a telescoping sight. So, I imagine, coaxiality is maintained.

[Bart B.]

Originally Posted by Unclenick

The patent is expired. Nobody needs permission now.

I think, to address the original question, the answer is, broadly speaking, yes.

Yes, expired Patent's designs can be used.

Why does the two V block and mirror methods both align all scope lenses on the optical axis near identical but putting adjustments midpoint in their range doesn't? Every scope I've set adjustments midpoint mechanically put the erector tube angled off center and when spun in V's, the reticle spun around the image. A couple were visibly off center viewed through the front.

Most, if not all, scope's reticle stops moving across the field of view before reaching mechanical limits going right and up. Evidence to me the erector tube stopped against the outer tube before the adjustment mechanical limit was reached.

[reynolds357]

Originally Posted by Bart B.

Yes, expired Patent's designs can be used.

Why does the two V block and mirror methods both align all scope lenses on the optical axis near identical but putting adjustments midpoint in their range doesn't? Every scope I've set adjustments midpoint mechanically put the erector tube angled off center and when spun in V's, the reticle spun around the image.

Most, if not all, scope's reticle stops moving across the field of view before reaching mechanical limits going right and up. Evidence to me the erector tube stopped against the outer tube before the adjustment mechanical limit was reached.

Your last paragraph is the answer to the question asked in the second paragraph.

[Bart B.]

Good stuff from Unclenick...

I should explain virtual image. The way a telescope of any kind works, you focus the eyepiece on the plane that the main objective is focussed on. If you, for example, put a sheet of paper in the focal plane of a main objective lens, standing to the side (so you aren't in the way of the image) you will see a sharp image projected onto the paper by the main objective lens. If you remove the sheet of paper, there is still a virtual image on the same focal plane, but you just can't see it when air is all there is on that focal plane because air is transparent rather than reflective, as the paper is. Now imagine the paper is back in place and the eyepiece focussed on it from behind. Then, when the paper is removed, the eyepiece will be focussed on the virtual image and will see a clear, sharp image put there by the main objective lens.

Yes indeed. First and second focal planes in scopes are virtual images. Erector lenses focus the first one into the second then the eyepiece lens focuses it for your eye. All telescopes have 3 lens groups so the viewed image is right side up.

The formula to calculate scope magnification is objective lens (system) focal length divided by eyepiece focal length. Most rifle scope's eyepiece focal lengths are about 2 inches, objectives 4 to 8. A 20 power scope needs an objective lens focal length of about 40 inches. The scope's objective and erector lense's spacing and focal length combine to do that optically to achieve that 40 inches in a 14 inch long scope sight. Erector lens spacing and positions are changed to change power in zoom scopes as well as range focus. Binoculars typically have two lens groups on each side and use prisms to invert their objective lens' virtual images.

I don't care how much clearance there is from the rifle scope's inside tube's parts to the outside tube's parts. The centering job is to get both tube's center axis aligned so the line of sight aligns to both.

[reynolds357]

Originally Posted by Bart B.

Good stuff from Unclenick...
Yes indeed. First and second focal planes in scopes are virtual images. Erector lenses focus the first one into the second then the eyepiece lens focuses it for your eye. All telescopes have 3 lens groups so the viewed image is right side up.

The formula to calculate scope magnification is objective lens (system) focal length divided by eyepiece focal length. Most rifle scope's eyepiece focal lengths are about 2 inches, objectives 4 to 8. A 20 power scope needs an objective lens focal length of about 40 inches. The scope's objective and erector lense's spacing and focal length combine to do that optically to achieve that 40 inches in a 14 inch long scope sight. Erector lens spacing and positions are changed to change power in zoom scopes as well as range focus. Binoculars typically have two lens groups on each side and use prisms to invert their objective lens' virtual images.

I don't care how much clearance there is from the rifle scope's inside tube's parts to the outside tube's parts. The centering job is to get both tube's center axis aligned so the line of sight aligns to both.

I remember my first refracting telescope viewed objects upside down. Way back in the day.