Electronics > Projects, Designs, and Technical Stuff
DIY Focus Stacking for Macro Photography
mawyatt:
--- Quote from: RoGeorge on July 01, 2020, 11:27:46 pm ---
--- Quote from: mawyatt on July 01, 2020, 10:42:25 pm ---Think we've pretty much pegged the limit performance on focus rails with the THK KR types, with 400 step motors and Trinamic based controllers, that's when the piezo efforts began. This is seriously expensive stuff new, well the THK stuff is also, so eBay becomes a valuable resource :)
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The speaker as a focus stage idea you mentioned before seems a very good alternative. Much easier to control than a piezo actuator, also, since is a mass produced item, a speaker is very cheap.
Another idea that just came when you wrote together the words voice coil actuator and speaker (mass produced), was the actuator from a CD/DVD/BluRay unit. It is mass produced (so it's very cheap), and is capable of very high speed moves on more than one axis. Has all the mechanics in place, very low inertia and high speed photodiodes to implement a very fast PID for stabilisation.
Gave it a search and found a nice paper (https://doi.org/10.1021/acssensors.8b00340) about reverse engineering the optical head of a disc unit (3 different models from gaming consoles). In the supplementary material there is a slide show presentation and some control schematics, too: https://pubs.acs.org/doi/abs/10.1021/acssensors.8b00340
The up down range is quite limited, just a couple of millimeters, probably enough for a chip die or a very small insect.
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Interesting, thanks for showing. I wonder how much load these actuators can handle?
The P601 and P603 PI Piezo Stages can handle moderately heavy loads in Closed Loop, this was the weak link of the speaker VCM. There was no practical way for feedback, so it operated Open Loop and suffered from position errors.
The THK KR rail types are very well designed and use a temp compensating base metal, probably the best available in screw type linear rails. With the Piezo stage operating in closed loop we created a setup at high magnification (800X I recall) and watched the image as a hair dryer on hot setting blew hot air across the piezo stage. It hardly moved, the control voltage was all over the place to keep the loop closed but the stage was rock steady. When this was done to the THK KR20 the image quickly drifted off screen, direct consequence of open loop operation, even with the superb THK KR20!!
The setup we use for high magnifications utilize the piezo stage and the THK KR20 rail. The KR20 is used for coarse camera/lens positioning and the Piezo stage for fine moving the subject. Many times I don't bother powering the THK rail up, just use it as a manual positioner by turning the motor shaft. Since we know the motor steps (400) and the KR pitch (1mm/turn) we can make movements by hand just counting motor cogs steps at 2.5um/step. If we need something between steps, the the KR20 must be powered to get fractional steps. The Trinamic controllers have 256 micro-step increments, so theoretically you could get 1mm/400/256, or 9.765nm increments. Of course this is ridiculous, a reasonable estimate would be 10 to 20 times that.
Best,
c64:
These pictures look awesome. So sharp, look more like 3d models not photos.
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Mechatrommer:
--- Quote from: 2N3055 on July 01, 2020, 10:23:03 pm ---Amazing!
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--- Quote from: c64 on July 02, 2020, 05:46:16 am ---These pictures look awesome. So sharp, look more like 3d models not photos.
Subscribe.
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his collection can be downloaded at nikonimagespace (100MB+) from his thread Some Older Chip Images this will not consist of the techy stuffs discussed here and on the photomacrography forum he linked alone. photo/color doctoring is one discipline in photography also required, used in movies everytime without muggles knowing it. i used to combine photos for HDR effect and then later add punch to the color. you dont get such color in real life... few random example attached... btw i downloaded his collection for my keeping and learning later, the folder name where i've put it tells something about its ranking..
--- Code: ---:\Knowledge\Digital Camera\Masterpiece\mawyatt (eevblog)
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not have a use for FOV bracketing yet, let alone the lens used by OP to get microscopic pictures of the silicons. but one trick to increase FOV is reduce lens aperture as much as you can (pinhole camera), since amount of ambient lighting will be much reduced, you'll need more powerful artificial lightings to help with colors painting where they need to be (photographer's rule to paint with lights). i can see some imperfection in the focus stitching, either its manually edited, or the stitch SW used is not so perfect yet. maybe manual editing and "space re-warping" in photoshop can give better result esp in exhibition or competition grade purpose. ymmv and fwiw..
Hydron:
--- Quote from: mawyatt on July 01, 2020, 10:42:25 pm ---Some folks have 3D printed various adapters, holding fixtures and light fixtures, but I haven't seen anything like a focus rail.
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I didn't mean printing parts to use as a focus rail, but to use the printer itself as one! On my printer a full step on the Z axis is 40 microns, and it does 1/16th microstepping so you'll get a bit more resolution from that, albeit not as linear. The X and Y axes are significantly more coarse and are likely to have issues when throwing significant loads around (e.g. my early Canon non-USM 100mm macro lens plus a camera is fairly heavy), but if you attached a sample to the Z axis and moved it up by full step increments then in theory you can move it relative to a camera sitting on the bed pointing up at it. Control is a simple as sending G code commands with the Z move distance (there may be some jiggery pokery forcing it to move without a homing cycle first, but you could get around that by homing first then setting it up for photography).
This is obviously on the less extreme side compared to piezo stages etc, but I might test it in the 1-2x max macro range I can manage with the gear I have at hand.
RoGeorge:
--- Quote from: mawyatt on July 02, 2020, 12:33:10 am ---The P601 and P603 PI Piezo Stages can handle moderately heavy loads in Closed Loop, this was the weak link of the speaker VCM. There was no practical way for feedback, so it operated Open Loop and suffered from position errors.
The THK KR rail types are very well designed and use a temp compensating base metal, probably the best available in screw type linear rails. With the Piezo stage operating in closed loop we created a setup at high magnification (800X I recall) and watched the image as a hair dryer on hot setting blew hot air across the piezo stage. It hardly moved, the control voltage was all over the place to keep the loop closed but the stage was rock steady. When this was done to the THK KR20 the image quickly drifted off screen, direct consequence of open loop operation, even with the superb THK KR20!!
The setup we use for high magnifications utilize the piezo stage and the THK KR20 rail. The KR20 is used for coarse camera/lens positioning and the Piezo stage for fine moving the subject. Many times I don't bother powering the THK rail up, just use it as a manual positioner by turning the motor shaft. Since we know the motor steps (400) and the KR pitch (1mm/turn) we can make movements by hand just counting motor cogs steps at 2.5um/step. If we need something between steps, the the KR20 must be powered to get fractional steps. The Trinamic controllers have 256 micro-step increments, so theoretically you could get 1mm/400/256, or 9.765nm increments. Of course this is ridiculous, a reasonable estimate would be 10 to 20 times that.
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Indeed, load weight for a CD optical head is not much, probably a gram or so at most.
Another type of closed loop actuator, even easier to use and totally free for DIY experiments will be the actuator from an older hard disk. HDD heads already heave the control loop, are trivial to position with nothing but software and an old PC.
I've played a few times with opened HDD running. They can work in open air for a very long time, for many days if not weeks, in a normal living room. The drawback is that the absolute position of the actuator is read from one of the spinning disks, so the disk must spin for the original control loop to keep the actuator in place, therefore it will come with some vibrations from the spinning plates. Maybe synchronizing the camera trigger with the angular position of the spinning disks, or maybe keeping the objective open for infinite exposure time and just flashing some LED lights in sync with the disk RPM might help catching the vibrations always in the same position. I don't know.
However, once locked on a track, the HDD heads are very stable, it was not easy to unlock their position by hand. I didn't measured the force, but I'll guess the actuator could drive an extra load of tens to hundreds of grams. That should be enough for a small stage with a chip die or an insect.
I imagine the HDD to stage adapter like a big loop of fishing wire that is anchored to the arm of the HDD actuator. The fishing wire loop is bigger than the HDD, and leaving the HDD body through small holes in the sides of the HDD frame, so to not keep the HDD plates spinning it open air. Small ball bearings in the corners of the closed loop of the fishing wire might help. Seems too complicated already.
Maybe just a small aluminium stage anchored with 2 screws on the actuator's arm would be enough. Far from ideal, but good for insects and free to try, with only a weekend long, or so, of tinkering. Or, it might not work at all because the PID coefficients might not cope with a much heavier load... ;D
Speaking of insects and macro shots and focus stacking, a trick that I've discovered by serendipity:
To arrange the photo posture of a live insect, and to make it stay still in the given position for a few minutes, put the insect in a refrigerator, 40° F (4° C) for half an hour, or so. :)
This won't hurt the insect. To them, those cold temperatures might easily happen in the wild during a cold night. It will take to an insect a couple of minutes before its temperature will raise enough to start moving, even when put in the direct sunlight for a better photo. That should be enough time for a quick focus stacking shooting session.
Back to that gorgeous photo you posted before, "Iridium- DMap-Obj-1a-Edit.jpg", a stupid question, but please keep in mind that I know nothing about laying a circuit in a die, so here it is:
Are those spheres the soldering balls? Asking because they seem incredibly close to various die structures. Some of them look like they have no dedicated pad area underneath. Isn't there a danger for the melted soldering ball to cover or get too close to the die structures? Then, there are some circular structures in the most left corner, I assume are some microwave coils. Wouldn't those coils be too close to the PCB traces, or to the PCB copper planes that the PCB designer might put underneath the coils area, and thus ruin the coil's Q factor by the Eddy currents induced into the PCB's copper?
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