A frequent request is people who are interested in using a home-built microscope to look at larger objects that aren’t transparent, for example bugs, materials, or electronics. The OpenFlexure Microscope isn’t the ideal solution for this, because it’s heavily optimised for small objects and high magnification. For lower magnification, there is a dissection microscope that should be ideal for that sort of thing. You might also like to check out FlyPi which is an awesome project that’s ideal for looking at fruit flies - and one of the inspirations for the OpenFlexure Microscope.
Thanks for the awesome project. I would like to view Integrated Circuit(IC) Chips using microscope. The internal of an IC would look something like this.
This is definitely a non-transparent object. I see in this post that the OpenFlexure Microscope is not meant for these types of objects. I would like to know what are the options to view non tranparent objects. I need really good magnification that the dissection microscope with just a simple raspberry pi camera wont suite my needs.
As per my understanding, the current openflexure has the light source on the top and objective lens at
the bottom. Is it ok that I take the objective lens with camera and put it on the top (using a stand - like a normal microscopes with eyepice) to view such non transparent objects ? For the light source, I will use ring led light at the same level of the objective. Will this work ? Or did I miss something ?
You certainly could do that, and I suspect it would work OK for low magnification (up to 10x or 20x objectives), but you wouldn’t have a nice focus control (because it’s built into the objective mount, underneath the openflexure stage). The translation stage on the OFM is also optimised for high magnification, so you will find it quite slow for your purposes.
If you want to make a system to inspect ICs, I suspect the nicest option (from the OpenFlexure project) would be to customise the flat top microscope - this has the focusing mechanism separated out, so you could mount the optics module on the focusing stage, above the sample. If you’re working at low magnification, you could then position the sample by hand in X and Y, but use the nice screw adjuster for focus.
If you are using higher magnification (i.e. field of view <500um) you might be able to use the delta stage for this, but modify the mounting for the illumination to hold the optics module instead. This is something we’d like to do in the future, but haven’t managed to do yet.
While checking further for microscope illumination, I found that most of the designs have the light source flowing through the objective. They are not using ring led outside. For example see this metallurgical microscope document.
Any reasons why ring led outside won’t perform well ?
Are there any design in OpenFlexure which uses plane glass or dichroic mirror ? I don’t know for what purpose/advantage dichroic mirror is used instead of glass.
LED ring vs beamsplitter depends on what you’re looking at and how you want to view it. For a scattering object (e.g. a white piece of paper, not shiny) there’s not a huge difference at low magnification. For a reflective/shiny object, there is a big difference - a flat mirror, under ring illumination, should appear black. Any little scattering objects on the mirror should be visible as bright objects on a dark background, so it’s “dark field” imaging. Using a beamsplitter, a mirror should appear white, and any objects on the mirror would be darker than the background (i.e. conventional “bright field” imaging).
The other consideration is the NA of the objective - at higher magnification, the objective is very close to the sample, so there’s not much free space for the light to get from a ring to the sample.
The fluorescence/reflection illuminator would allow you to use a glass plate or beamsplitter to illuminate through the objective - @JohemianKnapsody used this for imaging on silicon wafers. It’s a bit wobbly and calibration is a work in progress, but it does exist…
For what it’s worth I use a high definition RPi camera for checking SMT printed circuit boards. I’ve a Pimoroni Stand and C Mount “microscope” lens which they sell as a bundle for about £50, I use a Banggood white LED ring light with variable intensity which cost £15 including postage. The stand, camera holder and zoom feature allow close focussing.
It’s good enough to see the lead balls in the solder paste. So I suspect it’s good enough to see the die on a “decapped “ IC with a fair amount of detail.
Quite how you create a flexure microscope to do same thing is another issue. I’m happy to provide further details and some pictures should you wish.
FWIW, unless you need the very fine translation stage, the C mount “microscope” lens is probably your best option. I think it’s relatively low magnification, and the OFM is more designed for high-magnification use. The option I described above migth fit a niche where you need a bit more magnification/resolution than the Pimoroni stand offers, but still not so much that the sample has to be on a fine motion stage.
I have seen the magnification obtained from “C” mount microscopes. In my initial analysis they were not enough. I will do some more analysis.
Meanwhile I would like to understand the magnification obtained from this OpenFlexure High Resolution Optics . From this documentation, I understood that a compound microscope has 2 lenses and the magnification is the product of both the lens (objective and eye piece) magnification.
In this OpenFlexure High Resolution Optics, I see only 1 lens i.e objective lens.
- So if we use a 40x objective, does this mean that this microscope will only have 40x zoom ?
- Is the zoom obtained from eye piece of a compound microscope been replaced by the digital zoom that we do on the raspberry pi camera/software ?
- So if we do 10x zoom on raspberry pi, will be equivalent to 400x zoom microscope (like a compound microscope with 40x objective and 10x eyepiece) ?
You are exactly right - a finite-conjugates objective lens projects an image 150mm away with the stated magnification. An eyepiece then effectively magnifies that intermediate image.
Instead of an eyepiece, we just put the sensor at the image plane, so the magnification from sensor → screen replaces it. The sensor is 3mm wide, and you can roughly calculate the equivalent “eyepiece magnification” by figuring out how big the image is on your screen - though that is a number that changes depending on your screen size, which doesn’t make sense to me.
The additional tube length correction lens in the RMS optics module acts to decrease the magnification by roughly a factor of 3, but we’re generally still oversampling the image, so this doesn’t lose much if any useful information.
I tend not to trust “zoom factors” because they are never the full story and somewhat meaningless for digital microscopes. The important quantities are the resolution (i.e. the smallest thing you can see) and field of view (i.e. the width of the area you can image, in units of distance in the sample). If you can figure those out for your application, that will tell you the optics you need.
My rule of thumb is to compare the objective magnifications - that’s usually a fair comparison. The OFM is probably equivalent to a 15-20x eyepiece (and almost every eyepiece I’ve ever used has been 10x), but bear in mind this just means the field of view is slightly smaller on the OFM - the additional magnification doesn’t come with additional resolution.
I’ve asked some friends from the ham radio community for some chips to remove the caps from without having to use boiling acid. Seemingly the ones with ceramic lids can be removed mechanically ( hammer and chisel). It’s also possible to see the die on an old school UV erasable memory chip. Depending on how many I get and how many survive the decapping I’m happy to give them to experimenters.
Hi, for what it’s worth I spent a little time this morning taking pictures of an antique EPROM die using my RPi “microscope “ setup using the HQ camera, a stand, cheap Banggood ring light, and Pimoroni zoom lens. Apologies for the poor photo quality. I used my phone to take screenshots. The magnification was as much as I could achieve with the lens, however it’s clear that the ring light is not going to provide sufficient illumination for a lens physically much closer to the object.
First snap is the setup, the others should be obvious.
Nice - I guess the point at which you want a beamsplitter to illuminate through the objective is the point at which the OFM becomes a sensible solution! I still think hacking the flat top stage so it’s “upright” rather than inverted would be perfect for what you’re doing - but that’s not a trivial project…
Yeah, I posted these pictures to give the original poster an idea of what’s achievable without going down the Open Flex route. I’ve a few other ideas to try before I attempt hacking the design to do what he wants.