How to DIY a Liquid Focal Length Lens

This tutorial will show you how to create your own zoom lens using simple components. This lens will be able to change its shape and therefore focal length, depending on the amount of liquid inside it. It will also have a soft surface that we can press on to distort everything we see through the lens!

A warning: It took me several tries to make a lens that didn’t leak. I hope this tutorial works the first time, but if not, post a question in the comments! Also, the photos in this tutorial were taken over several different tries, so they may not exactly match what you get. Finally, this manual uses laser cutting and acrylic solvent welding, so always take appropriate safety precautions when working with hazardous or unknown substances and tools!

Step 1: background information

Before we get started, let us talk a little about optics first!

Light changes its direction as it passes through different media (a phenomenon called refraction). In lenses, we carefully control the angle at which light travels from one medium (air) to another (glass or plastic that makes up the lens) and back in order to focus or otherwise alter the light. Most camera lenses are made up of a number of separate elements that work together to correct various types of aberrations (optical errors) and create a flat, focused image on the image plane (camera sensor). But if all of the lens elements are fixed in size and shape, how do the camera lenses focus or scale the image? When a camera lens changes zoom or focus, it moves the individual lens elements (or groups of elements) forward and backward in relation to each other within the lens.

Step 2: selection of materials

In this tutorial we are going to create only one lens element, but unlike the elements in a typical camera lens, ours will be able to change shape (which will change its optical properties). This is because one side of our lens will have a transparent silicone membrane that will change shape depending on the amount of liquid inside the lens. The other side of our lens will be flat. Our lens will be able to change shape from a plano-concave lens (one side is flat, one side is concave) to a plano-convex lens (one side is flat, one side is convex) of the lens and everything in between!

Below are the materials and tools required for this project:

Materials:

  • Transparent acrylic with a thickness of 3.175 mm;
  • Syringe and tube;
  • Silicone sealant;
  • Acrylic solvent (alternatively: you can use acrylic adhesive);
  • Transparent silicone sheet;
  • Propylene glycol;
  • Mounting screws and nuts;

Step 3: selection of tools

Instruments:

  • Laser cutter *;
  • Sandpaper (any grain will do);
  • Clamps for holding parts while gluing them together.

* Note: It is not necessary to use a laser cutter for this project and I know it can be difficult to access! However, this description is for a laser cutter because that’s what I used. If you find another way to make a liquid lens, tell us about it in the comments (or better yet, write your instructions!)

Step 4: Design / prepare the file for the laser cutter

Some sizes you might want to check and possibly adjust for your specific build include:

Tube Hole Size: it should be about the same diameter as the tube you are using. We will fill the remaining space with silicone sealant.

Bolt Hole Size: the mounting bolt holes must match the bolts you have. I would not place them close to the edges or the o-ring.

Sealing ring: In this design, the acrylic o-ring is cut from the same piece of acrylic that forms the o-ring groove. To ensure enough clearance for the silicone sheet to pass around the o-ring, I added extra slots inside and outside the o-ring. This means the O-ring and groove are formed by 4 concentric circles in the structure. It may be necessary to cut a few o-rings and adjust their thickness until you find a suitable one but not leaking!

Cutting drawings

Step 5: laser cut acrylic parts

Cut out the parts from a sheet of acrylic using the settings for the specific machine you are using!

Step 6: Solder the bottom half of the lens with solvent

Remove the paper from layers 1-3 and place them on top of the other, making sure their bolt holes match (you can use the bolts themselves for this). In a well-ventilated area, carefully solder or glue the layers with solvent, making sure that the solvent does not come into contact with the open center of layer # 1.

Step 7: Install the tube in the bottom half

Next, we will install a tube that changes the amount of fluid inside the lens.

  • Sand the end of the tube and the inside of the acrylic channel where it will sit using sandpaper so that the silicone has a surface to stick to;
  • Apply a sufficient amount of silicone sealant;
  • Be careful not to smear the end of the tube.

Step 8: continue building with layer # 4

Add layer # 4 over the bottom half and solder with solvent. Make sure there are no gaps around the tube. You may need to use clamps to ensure a good seal. At this point, the tube should be in place.

Step 9: Continue assembly with layer # 5 (O-ring layer)

Layer 5 consists of three parts: the outer part, the O-ring and the innermost part. Glue the outside and inside to layer 4. Leave the O-ring aside for now.

Once the glue is dry, sand well all parts around the O-ring groove and the O-ring itself to avoid sharp edges that could cut the silicone sheet.

Step 10: add a layer of silicone sealant to the bottom of the o-ring groove

One of the first things that this project taught me is that it is very difficult to make things airtight or waterproof. “Life always makes its way,” and so does propylene glycol! Adding drops of silicone to the bottom of the o-ring groove definitely helps keep the propylene glycol in place, inside the lens!

Step 11: Continue assembly with silicone sheet and layer # 6

Honestly I warn you that this is one of the most difficult steps in this tutorial, so take a break before this step …

In this step, we are trying to secure the silicone sheet to the top of the lens and connect everything together with the mounting bolts and nuts. It should look something like this:

  1. Hold the silicone sheet relatively tight over the top of the lens;
  2. Ask a friend to squeeze the O-ring together with layer # 6;
  3. Place clamps around the perimeter to hold everything together;
  4. One by one, replace the clamps – with bolts, making sure the silicone sheet is still pressed against the O-ring.

Step 12: Check for leaks!

If you managed to get through the previous step without tearing the silicone sheet, congratulations! Now check the tightness by blowing into the tube. In the video, air comes out of the lens: when I blow, the silicone sheet swells, but when I stop blowing, air comes out from somewhere. 🙁 I hope your design will keep its shape at this stage!

Step 13: fill it up!

At this point, if your lens is airtight, you can fill it with propylene glycol and use it.

For this:

  1. Fill the syringe with propylene glycol;
  2. Connect the hose to the lens;
  3. Gradually add a little propylene glycol and, at the same time, remove air from the lens;
  4. Do not overfill the lens!

Step 14: try it out

At this point, you should have a working lens with an adjustable focal length! Very cool! What’s next?

Well, there are many projects that could use such lenses. You can use it in front of a projector or camera for unusual effects, or use it like a magnifying glass, or press your fingers against its sticky perfection hour after hour (just look at those nails!). It depends on you. The video above has examples of how I tested / played with my lens.

Please let me know in the comments how you are doing, have you found a way to improve this process, or have you discovered some other way to use this lens.

Step 15: Further Research

Hopefully this lens is just the beginning of new optical projects. This project was largely inspired by some of the projects below:

Hands-on experience with liquid lenses

Adjustable lenses

Lensesmade using CNC / 3D printing.

Approx. translator:All modern devices are in an endless race in search of more and more compactness of their components. Thanks to this, there is an acceleration of scientific and technological progress, and a constant decrease in electronic components, as well as mechanical systems.

Optics also did not stay away from these tendencies. If at the previous stage, flat Fresnel lenses were used to reduce optical systems, then at the present stage science has come close to using lenses with variable properties.

Back in 1995, one of the French physicists proposed using liquid lenses for use in cameras:

And literally in March of this year, the news came out that Xiaomi was going to introduce such lenses in its smartphones of future generations:


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