Focusing stand makes cheap USB microscope more useful

There are digital USB microscopes available for very low cost from merchants on eBay.  I bought one with high hopes, but I was disappointed when I tried to use it.  Due to the high degree of magnification, the field of view is extremely small, and the depth of focus almost non-existent.  This meant that the scope needs to be held rigidly for it to be useful.  Using the stand that came with the microscope, it was almost impossible to adjust the focus without moving the scope so that the specimen wasn't even in the field of view any more.  And if you tried to move the scope to aim it, you would inevitably change the focus.  In addition, the stand included with the scope held it at an angle with respect to the table top.  Given the very shallow depth of focus, the microscope needs to be held at right angles to the plane on which the specimen rests.

What I needed was a stand which would do three things:
1. Hold the microscope so that it is perpendicular to the table.
2. Hold the microscope rigidly.
3. Provide a focusing knob, so that the focus can be adjusted accurately without disturbing the specimen.

I wanted a small rack-and-pinion mechanism for the focusing.  I considered several options, including re-purposing parts from an old photo enlarger.  In the end, it was the same vendors on eBay from whom I bought the microscope that provided the missing parts.  I got a macro focusing rail that was very inexpensive and fit the bill perfectly.

With the microscope attached to the focusing rail, all I needed was a rigid stand to hold it in position.  I built a stand out of laser-cut acrylic.  (I made it at TechShop.  www.techshop.ws)  The result is a handy microscope that's easy to use and cost well under fifty bucks.

Step 1: Tools and Materials

The microscope is built from the following major components:

1 - USB microscope.  A good place to start is to search eBay for "USB microscope".  Often they are advertised as having 20x to 200x magnification, with some as high as 800x.  Most have either four or eight LEDs on the front to illuminate the subject.  Beware: the one I got claimed to have 1.3 megapixel resolution, but it was really only 640x480 with post processing software to enlarge the file size.  When I pointed this out to the vendor, he promptly refunded half my money, so the microscope cost me only about twelve bucks!  The price on eBay for these scopes is about $20 to $30 including shipping from Asia.  Yes, you'll have to wait 4 to 6 weeks to build this project!

2 - Macro Focusing Stand.  Search for "macro focus".  They are often described as "two-way" for a single axis.  The one which fits the acrylic stand described here usually has the brand "Fotomate" printed on the unit opposite the adjustment knobs.  Expect to pay about $12 including shipping.


You'll also need the following tools and materials:

- laser cutter
- acrylic sheet, 9" x 12" 
- cement for acrylic plastic
- dispenser for acrylic plastic cement
- clamps to hold assembly during gluing
- long nose pliers
- hot melt glue gun and glue
- small cable clamp, the right size to fit your microscope cord
- 4/40 machine screw. 1/4" long
- #4 flat washer
- 4/40 tap, tap wrench and #43 drill bit (0.089")
- self-adhesive silicone feet

Comments

[braingram]

Looks nice. I wonder if you could motorize the stand, set the focus of the camera at a high zoom and take high resolution 3d scans of tiny things like the new Nikon Shuttlepix does. I can't find the name of the algorithm, but it seems like you're almost there on the hardware side of things.

[nnewlon]

Interesting idea. If you wanted to motorize the focusing, you would probably need to gear the mechanism down further. As it is, fine focusing is a matter of moving the elevation knob a very small amount, on the order of a few degrees or less.

[tholopotami]

Nice design!