A Maker Loupe

While visiting family on the east coast, my mom gave me an old pair of partially functional binocular's that she had in a drawer. These became my next test.

First I had to carefully take apart the binoculars to free the right and left sides:

After removing the set screws on the eye pieces (as well as the rubber cushions) and the plastic ring that holds the objective lens in, I was able to inspect the lens assembly.

These binoculars do not seem to use the Galilean telescope layout like the last set that I worked with. Between the objective and eye piece there is a set of prisms that flip the image seen in the eye piece (without these prisms the image is upside down).

Playing around with the distance between the eye piece and objective lenses I found that, like before, I could get a magnified image of objects about 20-30 inches away.

Next step was to figure a way to mount the two sides that would allow me to adjust the distance they were apart as well as allowing them to turn inward to converge the right and left images together. For now, I wanted to use original tubes from the binoculars.

First I needed to re- thread the holes used to attach the original bridge between the two sides.

I tapped the holes for M5 screws.

Then I bent a shaped 2 pieces of flat aluminum stock, drilled holes to fit the M5 screws on one end and drilled at tapped (for M4 screws) holes on the other end.

Using a piece of scrap aluminum angle I drilled two holes (really 3 but 2 were next to each other to make one hole longer to allow for adjustment).

After replacing the lenses into the original tubes I adjusted the spacing and angles and got them to focus quiet well at about 20 inches.

So far a very successful prototype, even though they aren't hands free yet. Next I'll need to work on a head mount and then on to some fine tuning and some practical tests. If all goes well I can then go on to work up a 3D model of a more complete design.

still working filling this all in

Vocabulary - for Optics, Lenses, etc.

• Depth of Field
• Depth of Focus
• Magnification
• Focal Distance/Length
• Field of View

Part Suppliers:

• Surplus Shed (so far least expensive and most reliable)
• Edmund Scientific Optics
• Ebay (of course - but you need to know what you are looking for)

Optical Principles:

Reference Articles:

Presently, I am primarily looking at a Galilean design, which involves using a double concave lens (for the eyepiece) and a plano-convex lens for the objective lens (end closer to the object we are looking at).

This is the configuration that many of the surgical and dental loupe's use. It also seems to be the arrangement used in some types of binoculars (and "opera glasses").

Just for something to start with, I ordered a double concave and a double convex lens from SurplusShed.

• Double Concave (18.2mm diameter, -12mm focal length)
• Double Convex (25mm diameter, 25mm focal length)

Very Basic Galilean Telescope Design

The Galilean Telescope utilizes a convex objective lens coupled with a double concave lens. This arrangement allows for a shorter length telescope with greater magnification and a image that is not inverted.

Testing the lenses that I ordered

I designed and 3D-printed lens holders, that could mount to aluminum T-Slot extrusion (to keep them steady and aligned). This combination of lenses did not perform as I'd hoped (focus was poor, field and depth of view were very limited).

Along with the lenses I ordered, I decided to experiment with things I had on hand - in this case a set of pocket binoculars. They were unable to focus on objects less than about 5 feet away. While using the focus lever I noticed that when I focused on closer objects the eye piece moved back (away from the object lens - the lens facing the object).

So, I decided to see if I could move the eye pieces even further away to focus on closer objects. To maintain alignment of the lenses I designed and 3D-printed an extension to fit the eye pieces of the binoculars.

It worked, nearly perfectly. I was able to focus clearly on objects about 2 feet away, with magnification. The only issue is that the the right and left images do not converge, since the binocular body directs the view directly in front and almost parallel.

I can see that I'm on the right track, thankfully. Now I just need to be able to adjust the angles of the lenses to converge at the correct distance.