xiphmont

The end result of more playing around with the plastic LED collimaters: they're not going to work well. Dang.

The microscope wants a small diameter parallel light beam, and the plastic collimaters just won't do that. Even the tight spots overfocus and overmagnify, and there's no real room for adjustment.

Noq2's approach works because of:

a) brute force: 60W of LED light is the equivalent of around 350W of halogen light

b) a large die LED (7mm diameter!): that's more like a small COB

In his case it's a 'close enough' approximation to infinity focus because of the huge die and tons of output. There's enough nearly parallel light in there along with all the rest to make it work. Most of the light that makes it into the optical path (which is likely only 5-10%, the beamsplitter doesn't combine much) is just lighting up the inside of the microscope body, but the light that does make it all the way through is diffuse and even and nice. Brute force works!

Me, I want as much of the light to be usable as I can get.

So I'm probably back to using lenses. The stock Olympus setup uses two air-gapped elements with a total focal distance of 11-12mm placed on either side of a halogen bulb. The bulb filament intentionally sits just in front of the focal point to defocus the image slightly. (EDIT: Actually, I'm wrong here; it's just past the focal point in order to produce a focused image of the bulb filament at the point of the iris in the microscope body).

Olympus uses some really nice glass. The first condenser element is a partial shortpass to filter out some of the infrared. The second weaker element nearly touches the first and finishes the collimation job. Two 45 degree front-surface (!) mirrors direct the light into the beam combiner body.

The biggest constraint on the collimater design is the diameter of the optical path through the scope, which is a little under 15mm at multiple points. Opposing that, we want to collect as much light as possible from the LED into the condenser, which means putting the lenses as close to the emitter as possible, and so choosing the shortest practical focal length. Focal length trades off against beam width; the shorter the focal length, the more the 'image' of the LED die is magnified and the wider the final collimated light beam.

The original Olympus optical design expands the image of the halogen bulb filament into a beam of approximately 15mm diameter, matching the optical path. The Cree XP-L LEDs I'm using have a die almost the same major dimension as the bulb filament.

A more powerful LED with a bigger die probably isn't useful if we're going to use a single-stage collimator. And an XP-L is easily the highest-flux LED I can get with a die this small.

The XHP70.2 might put out 5x as much light, but if that's over 5x as much area, it's not a net gain given the constraints (I'm going to test it anyway, but I don't have high hopes). The big die of the XHP70.2 isn't a problem for noq2 because he's not using any optics that magnify its apparent size. He could usefully apply a 15mm COB.

This also means we're not going to improve on the original Olympus lens choices without going to a more complex beam reduction design that probably won't fit. (EDIT: Actually, I can probably fit a Keplerian design in there)

I'm going to try it Olympus's way. Given how dang nice those lenses are, I'm totally yoinking them. And since I'm messing so much with the physical layout, I want some adjustment ability. Which means at this point-- I'm most of the way back to my original design. Oh well. At least much of it is actually built and this has become an iterative process. A little at a time rather than one fell swooooooop.

So... The next step is making some new lens tubes.

And mounting the Olympus lenses in them (using nice, reversible, not messy O-rings).

This gives me the lenses at the proper separation in a durable, flexible package. Now I have to make a tube mount that fits inside the lighting enclosure.

Electronics assembly!

But does it, for the lack of a better word, chooch?

Yes, it chooches.

Adding the pot to test the adjustment, it turns out my BuckBlock is sourcing more than 500uA-- it's actually closer to 625uA. Also, it's firing up at ~1.5v rather than ~ 1.75v. That means I want a 2.2k low-end resistor and a lower pot resistance. So I modded another 10k linear pot into a 13k exp-ish pot, and continued assembly.

Everything goes together as intended and looks nice.

But there's a snag; I knew there was a good chance the optics wouldn't play as well with the SZH as I hoped, and in fact, the focus behavior isn't working well once on the scope. The illuminator works, and alignment is spot-on, but it's focusing an image of the lens at working depth, which is suboptimal. Also due to the suboptimal focus, lots of light is getting wasted inside the scope as it scatters out of the parallel-light/infinity focus portion of the optical path.

I'm going to have to play more with it.

Earlier this year, when I was building mods for my Olympus SZH microscope, I planned a coaxial illuminator using LEDs. The design got... a little out of hand...

...and I put it aside.

Last week I stumbled upon noq2's blog, where he documented his LED mod for the same microscope. It's the polar opposite to what I was doing. His is simple, brute force, and gets the job done. Go have a read, it's nicely done (and his animated gifs of the SZH internals are great). And did I mention it's actually finished and working? :-)

This inspired me to reconsider what I was doing.

I mean, I know what I was thinking: a design worthy of the rest of the absurdly overbuilt Olympus. I mean, just look at the original collimator! They use front-surface mirrors in the light source!

Also I didn't want to sacrifice any original Olympus parts. Complete SZH coaxial illuminators still sell for over a grand. But that's mostly because they're usually missing accessories needed to operate them (the bulb holder and transformer) which I didn't need. Last summer I picked up a bare illuminator block for $90. That's cheap enough I'm willing to mod it permenently.

Then I saw noq2's build. It was brilliant. And even better, I can have everything I originally wanted with a dead-simple addition.

The whole 'tactical flashlight' craze has spawned a smorgasboard of cheap, canned collimation optics for LEDs. They're even better than lenses as they sit all around the emitter instead of a distance in front, so they catch more light. Most are 90%+ efficient.

So I'm taking what noq2 did and slapping a $2 spot-collimator on front. No muss, no fuss. Well, I have to fuss a bit, so I'll put the driver electronics inside the housing, and add an intensity adjustment too. Still not *much* fuss.

...beginning with hacking off a big ol' chunk of heatsink using a dull beaver...

and cleaning it up a bit on a sharper beaver.

Trim to fit the existing enclosure, with an eye toward reusing the existing mounting holes on the enclosure's rear boss. Also drill and tap holes for LED mounting, power jack, and a notch for a BuckBlock controller, and we end up with something like:

I want an intensity adjustment knob, so I stole the boss off the prototype I machined earlier this year. Along with bolts, a really nice 11-position-with-detents potentiometer, and the aforementioned LED optics (but not including wires) we finally end up with this exploded build:

Next up will be a little paint, a schematic, and build/test.

Finally, assembly... and confirmation of non-embarrassing results.

( Read more... )

*THUNK*

That's more like it.

And a Micromill ain't no toy.

Sadly, no Chinese manufacturer to date has cloned an SZH, but there are clones of other Olympus focus blocks.

None of these will fit as-is of course, the SZH is weird. But several look to be moddable with a little effort. So I chose a clone of a nicer Olympus coarse/fine assembly.

And now, a review of the FYSCOPE STEREO ZOOM MICROSCOPE COARSE AND FINE FOCUS ARM A4 76mm Size! ( Read more... )

I actually like my AmScope. It's not exactly precision-manufacture and god only knows what glass it uses, but it's durably made, fairly ergonomic, and works well for the price. Only one regret: The camera port is damned near useless.

For some reason, Chinese stereo scopes mostly appear to be clones of old, low- and mid-range Olympus designs. That planted the Olympus bee in my bonnet.

You've probably heard that Nikon is a world-class optics manufacturer that just happens to make cameras. Well, Olympus is a world-class optics manufacturer that just happens to make microscopes.

Looking for no-holds-barred top shelf stereo optics, the current top of the Olympus stereo line is the SZX12. Which is awesome and even broken surplus parts are so far out of budget it's not funny. Mostly the same for the SZX10, its slightly less featureful little brother.

But it turns out the very top of the discontinued predecessor line, the SZH10, is similar enough that it takes many of the same accessories and was every bit as good a scope. And the SZH10 was just a minor feature tweak of the earlier SZH.

And the SZH line is so gloriously 1980s. I mean, just look at this ad. It's not a stereo zoom. No, it's a *super* stereo zoom. And raytracing is involved somehow. And lightning. This here 'scope is obviously real wrath-of-god stuff.

Anyway, the rest is serendipity: There just happened to be enough cheap-ish parts on eBay to hopefully piece together a complete SZH with no major flaws.

Parts have arrived, so here we go...

It tries so hard to look like an Olympus SZ series, but no.... not quite.

It's not actually terrible, it's fairly decent. But it's not the real thing either.