Besides other things I'm very interested in lasers, the microscopic world, and to make things visible that aren't visible with normal means. I also find it a sport to use things for purposes where they are not designed for (aren't we all ;) ). Combining the above I came up with a solution for an idea I have for ages: making a Laser Scanning Microscope (LSM)! Nothing fancy as a Fluorescent Confocal Laser Scanning Microscope, but a straight forward LSM.

- An LSM works basicly as follows: highly focussed light from a light source hit point by point, row by row (X-Y plane) an object. The light, reflected from the object, wil travel back the same direction it came. A semipermeable mirror reflects this light containing data of the object to an LDR. The intensity of the reflected light is measured. A computer takes care of steering the light spot and also the image making (pic 2). -

At the same time I was wondered if it is possilble to use a DVD laser pick-up to make an LSM. Well, with some alterations, it is!

The reason I was thinking of a DVD pick-up is that it houses a laser and a lens capable of projecting a spot of visible laser light small enough to "see" a bit on a DVD. And those bits are very small (320nm)! Furthermore it houses coils to steere the lens (sideways and up and down) and a detection part. This steering is necessary to be able of following the microscopic narrow tracks on a CD or DVD while spinning (sideways moving of the lens) and follow height differences while spinning (up and douwn movement of the lens). You can imagine that folowing the track must be very precise considdering the turning speed and the bit size! These characteristics are exactly what we need!

I tested the pick-up as is:

  1. hooked the laser on
  2. pulled out the detector
  3. instead of the detector I put in an LDR (Light Dependent Resistor)

It's turns out to be unusable in this form because:

  • a technique in the pick-up to make multiple spots (grating filter, lens fringes)
  • one pick-up is for one axis only
  • the inertia of the whole pick-up.

At this stage the idea was born to use only the part that houses the lens with the steering coils. With one of these parts you can steer the lens in one axis. The other axis will be steered with another lens/coil part (as you can see later on). The result is one lens that can be moved in an X-Y plane! When (laser)light travels trough the lens when it is moving, the light spot wil follow this movement as well. This is more or less the most important part of an LSM.

Some specs:

  • enlargement approx 1300 times (resolution 200 nm)
  • image consists of 65536 pxels (256x256)
  • very cheap (maybe most parts you have already)
  • fun to build

there are some drawbacks to (naturally)

  • it is not quick (approx half an hour for an image to complete)
  • focussing is difficult
  • the image isn't crispy sharp (but I don't care, it's astonishing anyway)
  • addiction hazard :)

In this instructable I shall explane how I did this and what difficulties I encountered during the project. I think this instructable is a whole mouth full but building it is'nt really hard.

Pic 1 and 3 shows the model I work with right now. It was in the beginning of my project development a more chaotic contraption, but it did work fine!

Before you start building, a word of advice (pic 4): since this device's main part is a laser and the whole thing operates by means of concentrating and redirection by lenses and mirrors, of laser light, you have to be extremely carefull and take precautions for yourself an any bystanders not to stare directly into the beam or any reflection of it.

Step 1: Things You Need

Like every technical hobbyist most things you need you will have already in your possession. In the past decades I have taken appart several DVD/CD players and have always saved the parts for later use. You never know!

This is the list:

for the lens part:

  • two lens/coil parts of a laser pick-up (DVD and/or CD)
  • a bit of PCB
  • a piece if UTP cable (approx 15cm)

for the electronic part:

  • An Arduino UNO
  • An LDR
  • 2 x 10uF capacitors
  • 1 x 220 Ohm resistor
  • 1 x 10k resistor
  • 1 x 10k pot
  • 1 x 200 Ohm trim pot
  • 1 breadboard
  • 1 switch
  • 1 3,5 mm jack plug
  • 1 audio amplifier, a cheap computer amp (like the little ones with build-in speaker) wil do.

for the laser part:

  • 1 laser* with a good collimating lens
  • 1 piece of glas, a quarter of a microscope object glas or so to act as a semipermeable mirror
  • the under part of a ballpoint casing to put the LDR in

And preferably a decapitated microscope so you can build the whole thing in a nice housing with an in height adjustable object table. You can also use the adjustable object table of an other microscope for your objects, and position the lens/laser combination in one way or another above it, as I did in the beginning of this project, and that wil work fine, but if you can lay your hand on a scrap microscope you can make things much easyer.

The point is: you really need an in height adjustable object table (otherwise you can get very stressed.). It's even better if the object table can also be adjusted in the X-Y direction.

Keep in mind that to focus with this kind of magnifications, where the focus point lies on around 1 mm distance from the lens, you have to be able to adjust the object table within hundreds of millimeters!

For the computer part:

  • Four sketches, two of them for handeling the data stream coming from the microscope ("Arduino" and "Processing"), and two sketches to help focussing.

And to make live easier:

  • Hot glue
  • UV glue. This is a very handy glue to glue the thin wires on the lens part as you can see later on. I think this is the only glue that can do this job because there is no mechanical stress when applying this glue!

* there are lasers with varying wavelenghts. From long to short wavelenghts there are, among others: infra red, red, green, blue and ultra violet. With ultra violet (in this list the shortest wavelenght) you can theoretical make the sharpest image because you can make the smallest light spot. I have made a few with an UV laser and it did well, but the darker colored objects are harder to capture.

<p>hey, what's the model of LDR?</p>
<p>The LDR came with the official Arduino Uno starter pack.</p>
<p><a href="https://www.arduino.cc/documents/datasheets/HW5P-1.pdf" rel="nofollow">https://www.arduino.cc/documents/datasheets/HW5P-1...</a></p><p>This is the one in the Uno kit.</p>
<p>Thanks, but a HW5P-1 is a photo transistor. I make use of the LDR that comes with the kit.</p>
<p>I don't know the type.</p>
<p>Great Project! Well done!</p><p>I wander if it is possible to use directly the entire pickup since there is the laser and the diode to read it's reflection.</p>
<p>Thank you.</p><p>You're right about that. It's exactly what I thought. But as you may have read in my instructable, I tried that. I doesn't work fine because of the filter inside the pickup for taking care of producing multiple spots on the cd (for better tracking purposes) and that it's for one axis only, so you have to move the whole thing in the other axis as well. And taking the weight in considderation I think the inertia wil spoil the proces. And further more, you're very stuck to one laser. The solution I have used gives you the freedom of using different lasers. Besides that is it not clear how the light sensor in the pichup works. </p><p>All these reasons have made me decide to make it just like I did. But if you are confident to do it otherwise, your really should do that. Maybe it turns out fine.</p>
<p>You're right. But while I was thinking on this solution another guy used a different solution: two speaker</p><p><a href="https://www.instructables.com/id/Scanning-Laser-Microscope-With-Arduino/?ALLSTEPS" rel="nofollow">https://www.instructables.com/id/Scanning-Laser-Mi...</a></p>
<p>Yes I know. Please read my comments there.</p>
<p>Very nice project. Well done.</p>
<p>Thank you!</p>
<p>Great work! Maybe you may take a look at my slightly different Version of a scanning laser microscope: https://www.instructables.com/id/Scanning-Laser-Microscope-With-Arduino/</p>
<p>Thank you!</p><p>Please see my comment on your instructable page.</p>
&quot;I want one!&quot;
<p>Nice to hear. </p>
<p>I get many evil ideas from the Science Channel...</p>
<p>Like what?</p>
<p>A solar death ray, (I want to build one this summer) a chicken cannon, a paint bomb, (Bad college prank) piano of death, flaming saxophone, DIY grass killer just a name a few. Maybe I could cook the chicken with the death ray, drop the piano on the bomb to soften the explosion and add some crisp to the fully sun-burned chicken with the flaming saxophone. I still don't know what to do with the grass killer... &gt;:} I can seek revenge on the neighbors for not keeping their dog off the lawn.</p>
<p>Ditch the diode laser and go with a gas laser or other laser that has a TEM00 beam, diodes are multimode and really dont focus that great. An old argon ion laser would be ideal, the shorter wavelength would also give a much smaller spot size.</p>
<p>I know that. The idea behind this all was that I make an instructable that could be in reach for most technical hobbyists and that it will cost almost nothing to build. </p><p>The lasers you mentioned are most probably not the lasers most hobbyists have, pricewise, in there possession. Probably everyone is in possession of a laser pointer and believe it or not you can do LSM with them. I've done it. On the movie and at the end of the instructable there are some examples I made and indeed the shorter the wave length the better it is as I mentioned in my instructable (by the way these examples has to be seen not bigger than 7 cm across, then the pixels match the screen res.). Further more, the build with a gas laser instead of an diode laser is also more complex because of the size and weight of a gas laser. I think also that when you make use of an argon ion laser there is to much power and will burn holes in your specimen (it happend to me to with so little as 30mW!) because of the slow scan speed and the extremely small laser spot. </p><p>I have a TEM00 HeNe laser I've used to make holograms and maybe I'll give it a try with it one day. </p><p>Anyway thanks for your reply. Greets.</p><p>Ron (Venkes).</p>
awesome.thinking twice, thrice...
<p>There's nothing quite like reading about a guy who builds his own LSM, to give my swollen ego a nice, healthy smackdown. Awesome project!</p>
<p>Thank you! Now my ego grows a little bit.</p>

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