"Pocket Scientist":Keychain Compound Microscope From Laser Pointers,290X Mag, Under 5$, +3D Print, D.I.Y

Building a good microscope can be challenging and costly. Some online D.I.Y single-lens microscopes can do 100x magnification by adding digital zoom. However, a single lens microscope typically provides optical magnification of 18-40 times . After that, it is zoomed digitally so to get magnifications in the range of 100X.

But what if we can achieve higher 100-300x "optical" magnification using a dual lens compound microscope in the size of a keyring item? It can be carried in pocket or attached to mobile phones to record picture and videos.

The possible uses of this item are:

Educational Purposes: Enhance science education in schools by allowing students to observe microorganisms, fostering interest in biology and microbiology. You can see dead ants, flies, mosquitoes and insects and you will be surprised to see the detail in their organs: legs, eyes and so on. But try to find something that is already dead or harmful like a mosquito. Do not hurt animals or plants just to see them for fun under the microscope even if they are little.

Biological Studies: Students can examine cellular structures in plants and animals at home, such as cell walls, nuclei, and chloroplasts.

Medical Diagnostics: Diagnosing infections and diseases. Like identifying crystal for kidney stone or skin diseases etc.

Microelectronics: Inspect and repair small electronic components and circuits, ensuring proper functionality in devices like smartphones and computers.

Material Analysis: Inspect the surface quality and structure of materials like metals, plastics, and fabrics for manufacturing and quality control.

Gemology: Verify and evaluate the authenticity, quality, and characteristics of gemstones and minerals, identifying inclusions and flaws.

Entomology: Study small insects and arthropods, observing their morphology and behavior, which is crucial for ecological research and pest control.

Botanical Research: Investigate plant anatomy, such as leaf cells and pollen grains, to understand plant reproduction, growth, and disease resistance.

Forensic Science: Examine evidence such as fibers, hair, and residues at crime scenes, aiding in criminal investigations and solving cases.

Art Restoration: Analyze the surface of paintings, sculptures, and artifacts to determine the techniques used and to plan appropriate restoration methods.

To do this project, we will salvage high-power lenses from old laser pens. Will use a mobile phone's flash to illuminate the objective. The following instructable details the journey, including both successes and numerous challenges.

Please follow the instructions carefully for a good result. Specially the thread movements need to be smooth yet not loose. The 3d files are made with care but little bit of smoothing of the print files may be required based upon various printer types. If there is any issue or query let me know.

• Two lenses taken from two red laser light lens.
• 3d printer to print the models.
• Aluminium foil to reflect light.
• Small aluminium tube to guide the light. 8.5mm dia. max 100mm long.
• Misc. tools: tweezer, divider, pliers, screws, glue, lighter etc.

• I had this old laser pointer. The lens inside has good power, small focal length(around 5mm) and has aberration rectification.
• To get the lenses, unscrew the back of the laser, and pull the black sponge out by tweezer.
• Unscrew the laser shell by a divider or any sharp two pronged tool. be careful not to damage the lens.
• We need two such lenses.

Before making the compound microscope, lets share the tool to make a single lens microscope here as well. This provides upto 18x magnification as per observations.

• First we measure the diameter and thickness of the red laser light lens.
• The diameter of the lens is 4.89mm, thickness is 2.41mm.
• Find the approximate focal length of the lens. To do this, we check the distance of maximum magnification. For this lens, it was found to be around 5mm. This will be very near to its focal length.
• Then we make the holder of the lens. Tinkedcad was used to make the 3D model. The steps are shown in the pictures.
• Use the provided .Stl file , print it.
• Twist a screw driver in the slip to make the gap wider and and push the lens in. But do not touch the lens.
• Remove screwdriver and the lens will remain there.

• The lens magnifies better in one direction by correcting any aberration. In the other direction, it has more aberration and distorts the image borders. So identify the right direction and place accordingly.I have attached a general sketch but your lens may be different so check that.
• You can observe by eyes or have to attach the item behind a phone's primary camera and duct tape it.
• I could see a small square in the notepad as big as 9 lines of the notebook. So the magnification was only 9/.5 =18x.
• This is okay for checking small details like human hair, heads and legs of flies, mosquitoes etc. You can see the single lines of ink and the rust particles of Iron.
• If you use digital zoom of phone then you may reach higher magnification .
• But I want to see even smaller objects with higher optical magnifications.The next steps will help me do that.

See the image above for reference. The website link is also shown in the picture for reference of the thory.

Theory:

• The focal length of the eyepiece 5mm.
• The focal length of the objective is 5mm
• If we provide d0, the object distance at 6 mm from the objective, first image will be at di=1/(1/5-1/6)=30mm
• if di'=15cm or 150mm, then d0'=1/(1/5-1/150)=5.172mm
• Total magnification= (di/d0)*(di'/d0')=145x
• Pipe length=di+d0'=35.17mm

I was not sure how the device will turn up. But I started making the project in Tinkercad step by step and see where it goes. Tinkercad was good for this project.

My first idea was that it should be: A. 3D printed , B. Fine adjustment possible C. Attached nicely to mobile. D. stabilty of output view.

• To have fine adjustment, we need a screw mechanism. If we keep pitch of 3 mm suitable for 3D print, we can have 3mm/360 degree. So, the adjustment ration is 8.3 micrometer per degree or turn.
• Then we make a hole for the Lens.
• Gear for the adjustment: We place a gear which we can rotate. we make a threaded hole inside it. the hole has to be bigger the the thread of the lens holder. I had to make few adjustments on the clearance to get it right.

• Add two boxes and cut the sides of the thread to provide guides.
• Now we have a device where if you turn the gear, the green thread will move along the axis.
• Then provide a slit in the thread so that we can place and remove lens easily.
• Copy the item and change the lens cut sizes.

• I want to use the mobile flash to make the specimen really bright. So, I made a hole for an aluminium pipe. The pipe's reflective inner surface will guide the flash of the mobile to the specimen.
• Then I made a slope to reflect the light to objective. An aluminium foil will be used glued in the ramp to reflect the light.
• It shall be reflected in such a way that the object will be illuminated as shown in the picture.

• Needs improvement: The first video recorded in the phone is shown. There are some obvious issues. The image was not clear, the centering was very difficult. The setup of this test required a lot of sanding and fitting effort. The mechanisms were also not smooth because the printer printed the holes 0.4-0.6mm smaller. I gave up on this project for few days at this point.
• Still, a single line of pen ink is appearing very wide and spread out. So the magnification was much more than a single lens magnification. So the theory is at least right. I felt to return to this project again with new ideas and trials.

• Some adjustments were done to the threads and holes by reducing sizes by 0.4-0.8mm in a new model.
• Different orientation was chosen for the prints.
• A holder for the mobile was also added. But it was not right for fixing this item to multiple types of mobiles. So the idea was abandoned.

• A much refined model was 3d printed in trial 3. Mainly a shorter and more manageable length of the scope. It was successful. The making images of the final model are attached.
• The 3d files are attached also for 3d printing.
• The lens near the specimen was attached by the plastic screw taken out from the laser pointer as shown in the 2nd image(left gear).
• The lens near the eyes needs to be large enough. So the plastic screw was not used. a heated knife was used to heat the PLA and make a notch to hold the lens 2nd image(right).
• Then attach the aluminium foil and aluminium tube with super glue.
• The gear top thread may have few threads hanging due to horizontal 3d printing. So it needs to be cut and smoothened with a hot knife as shown. Check till the Gear rotates freely around the threads but not so loose that it moves axially. Then you will not be able to focus easily. (If you print the gear vertically then this problem will be resolved. But another problem will arise of not rotating freely around the threads. Its because of high friction by the layer end protrusions. So its better to have a smooth gear instead.)
• Tip: If you use heat of 60-80 degrees by a Gas lighter then PLA becomes soft to work and be adjusted. I hope you don't need to do it because I have finalized the right geometry after few trial runs.
• Anyways, then add the gear and threaded lens holder and we are ready!
• For a fixed microscope and easier handling, tape the "Ears" of the microscope to the mobile as shown.

• Rotate the bottom gear for focusing. It should be near 5-6mm away from the specimen below. The top gear is only for fine adjustments. You may not need it at all unless you want a really fine image.
• You may need a little bit of practice before you get the hang of it. Do not be frustrated, keep patience.
• Also in this compound microscope the image is inverted. So if you want to see to the left, you will have to move it right.
• The lines of pen ink was 40-50mm in the display. So the magnification seemed to be 40/.3 to 50/.3, or between 133x to 166x.
• It is purely optical zoom and without digital zoom. If the camera is good, then with digital zoom it can provide a lot of magnification.
• You will get many interesting images when you look at heads and limbs of dead ants, spider, plant leafs, onion peels etc.

• A longer tube is designed for higher magnification after we have got the focusing system right.
• However, we need an external A.C LED source for the lighting at that magnification as shown. For 200-300x magnification, the light intensity also needs to be 200-300 times. The A.C LED light is put under a white paper sheet. Then the specimen slide is put above it.
• After that, the mobile phone along with the scope is put on a support as shown.
• As per calculation, it is providing upto 290x magnification but there are minor colour aberrations. So It does not provide a lot of sense to improve it more because it will become illegible I suppose.

This is a tool that helps in fine adjustment once you have got a blurred picture.

To get this project right, I had to run quite a few trials to get it right as you can see in the picture. Also the 3d printing of the thread and the model was quite challenging. There was a point when I almost gave up because the parts would not fit or there were issue in magnifications. But at the end the problems were resolved one by one and the project was successful. So if you like it, leave a "favorite" in the post to support the effort.

Caution:

• The distance between camera lens and the flash should match with the model. else you may need to either modify the model or use separate led for specimen illumination. For 100x magnification,logically you need 100x lighting.
• You can keep this in pocket and use bare eyes to see the view also, but the object needs to be put over a light source instead of camera flash. Also there may be a small bright circle at the center which needs to be ignored and you have focus on the the image in the wider circle. Let me know if any query.
• The microscope cannot replace professional high powered microscope which can give 1000x magnification with way better sharp images than mine. It is only for secondary use for help in microbiology identification only.