During a recent project for a client, I had to prepare a fluorescent bead slide for imaging. Beads require dilution, and a vortex mixer is recommended in order to provide ample separation of the individual beads. Not having one on hand, I figured there must be a way to achieve similar results, and found this used by a homebrewer for yeast prep. It was close for my needs, but I didn’t want to use wood due to the fabrication time and difficulty of install / removal. So I measured the screw hole spacing on the sander pad, and sketched one up in Fusion. A PLA print was made, and the result has been great for simple use.
One additional trick I use for mods like this, is a router speed control, available form Harbor freight or Amazon. It allows the motor speed to be adjusted. The little Ryobi is super fast, so I ended up suing the speed control on it’s lowest setting. These controls work well for most motors – some using “soft start” motors may not work, but it did great in this case!
If you would like to print your own (assuming the hole spacing is compatible), the STL file and STEP for modification are available on my Github page here.
Not sure the money pans out considering how much time it would take to build, but if one wanted to learn mechanical control, this would be a good way to dive in!
I can’t believe I missed this excellent post from Sam Lord @ Everyday Scientist on how to insert an emission filter on your ocular lightpath. Having been hit by some untold number scopes wherein I either was observing, and switched to a no-emission-filter spot on the dichroic turret, or where I was observing and for one reason or another (software reset?!?!) the excitation shutter opened inadvertently, I can say with certainty that if you work on scopes long enough, this WILL HAPPEN, and it’s not good.
Of interest is the FDA’s ophthalmic instrument guidance docs for retinal radiation (sec H 2.c). From my perspective, it’s surprisingly vague.
Because prolonged intense light exposure can damage the retina, the use of the device for ocular examination should not be unnecessarily prolonged, and the brightness setting should not exceed what is needed to provide clear visualization of the target structures. This device should be used with filters that eliminate UV radiation (< 400 nm) and, whenever possible, filters that eliminate short-wavelength blue light (<420 nm).
“The retinal exposure dose for a photochemical hazard is a product of the radiance and the exposure time. If the value of radiance were reduced in half, twice the time would be needed to reach the maximum exposure limit.
Bottom line, if you have a scope which is equipped with an emission filter wheel, this is something you should address.
Last month a friend gave me two old pairs of field glasses. One set was US Navy issue, which has the old-school build quality of a tank, and produces a bright, sharp image. The second pair was cheap and damaged. I’ve considered what to do with it for a while, and finally decided to tear it apart, and use the optical elements inside for educational, research and entertainment purposes. To that end I needed an adjustable optical platform, and while I have plans to make an optical table, for now I wanted to make a simple stack. Here’s how I did it.
Base with two optical elements attached
The base – I had an old aluminum base plate used on Sutter’s “LS” lamp series. We sometimes discard these bases during installs, so I managed to save this base from the scrap heap. I also snagged one of the support rods. This gave me a post with which to mount optics.
Next I needed something to hold the optics in place. I considered using band clamps, or other methods, but settled on making custom-cut holes that could accept the elements. If you want to do a similar project, you could use drill bits, a scroll saw, or even files to shape out the holes. I was itching to use my DIY CNC machine for something useful, so I employed it to cut the holes for me. I made a set of square blanks, and drilled a single alignment hole in each square. By using this hole as a center, I was able to make each different lens holder have a coaxial alignment, so that the lenses would stack up correctly.
Finished hole cut – note the alignment hole in the upper left side.
I’ve cut MDF (always wear a respirator when cutting MDF!) before, but have never had a good end mill for the job, so I finally made one by cutting one of my routing bits in half and sharpening the endpoints. The new bit chewed through the MDF with ease. To be extra careful I stepped my cuts at 0.050″ per route at a speed of 2ipm. This is a gentle/slow setup, but I wanted to make sure the parts came out well, and I didn’t want to push the machine for no reason. Finally, because I was cutting down nearly through the material, I set things up to leave a 0.010″ thick layer at the base of each cut. This way when the operation was done, I could simply push out the disk, and not risk cutting up my table on the machine. This process worked really well. Below is a video showing how easy it is to pop out the last layer.
With the holes all cut, I enlarged the alignment holes in each plate so that the plates would slip over the vertical rod I had. They fit snugly and allowed me to adjust the focus of each element as needed.
After spending a few minutes playing with the system I was able to set up optic trains providing magnification ranges from 10x to about 40x. The higher mag configurations didn’t look great, but here are some images I acquired using my iphone through the setup.
example configuration of lens elements
This was a fun project that only took about two hours to complete. Once I settle on an optimal configuration for these elements, I’ll post on it!
