a day ago •
I made a video of the optical design, simulations are done with pyOptools and rayopt.
6 days ago •
I started with improving the optical layout of the Hexastorm. Luckily, there is a company from Colombia, cihologramas.com, who made an open-source optical package for optics and also
provided some instructions on how to integrate this into FreeCAD. You can seen the result below.
I will explain the whole simulation in a different video.
They report a resolution of 25400 dpi, which is 25.4 (mm)/ 25400 = 1 micron.
Production speed is 55 cm^2 per hour, i.e. a square sided 7.41 cm.
These are 74100 lanes with a length of 7.41 cm, which is 1.54 m/s .
Most likely, they use a galvo scanner. It might be done much faster with a prism as well, but I would have to recheck the whole design. I will outline in the next video, how you can make a design, in the first place.
Here is one of their holograms;
05/29/2021 at 11:40 •
I found a technique, i did not consider earlier.
I think prisms are suited for this domain. An optical wave is split in two. One part is used to illuminate a sample from the bottom with a plane wave. The other part illuminates the sample at a specific point. The waves interfere and the reflected light is measured by a camera. A prism could be used to to scan this spot. It would require a very fast camera but these do exist.
It can be used in reverse as well for triggering reactions like polymerization. This requires something like a digital micromirror device, these are typically slower. So that might not be a good fit with current technology.
There is a very nice old video on holography on YouTube
05/21/2021 at 16:44 •
I created a new video, where you can see the exposure and the result.
This makes it much easier to see where the project is at. It is really easy to add measurement, see this excellent video.
My current aim is at bringing the module to production. I also plan to add confocal. A unique property of laser scanning is that it can read and write at the same time. This is a real advantage compared to other projection techniques like LCD.
05/14/2021 at 16:23 •
Just a quick update; I am now finally able to make exposures with the new nmigen gateware.
There are a lot of improvements in the new tool chain with respect to ldgraphy on the beaglebone.
- Slicing can be done on the Raspberry.
- Motion can be done with acceleration/jerk profiles
- Steps per scanline can be altered and is not fixed
- Whole code base is one language; Python
- It is much easier to align the optics;
the design of the laser head is improved and
there are algorithms to fix the alignment and calculate; spotsize and cross scan error
I will make a video for the complete process soon.
04/17/2021 at 11:56 •
I like to keep a record of related ideas I cross over on the web and the involvement of the Netherlands in laser scanning with prisms.
Various hackers have been active in the field of laser scanning microscopes. There is a project
on Hackaday (BlueBeam). A Swiss hacker space, Gaudilabs build one.
Most are based on components of DVD drives (link to a tear down).
Loetlabor also did an exceptional write down of DVD-based laser scanning microscopy.
They even used a FPGA core to control the laser.
Scanning this literature, I found the following figure;
It shows how the focus is obtained using a four channel photo-diode. One targeted at 850 can be found here Vishay K857PE. It could be nice to integrate this concept in the laser head. Possible areas would the current place of the photo-diode. Another option would be to place a beam splitter on the point where the laser is colimated, i.e. after the first aspherical lens and before the first cylinder lens.
All this thinking about imaging, made me think of another point of improvement.
Using the camera of an optical mice to record or track the laser beam.
Optical Mice, have camera's which are 30x30 pixels, e.g. ADNS-9500 S9500. The price is in the order of 3 dollars. The camera's might be large enough to image the spot formed by the laser.
At the moment, I use a CMOS camera from Arducam (OV9281) . These are great but much more expensive (in the order of a 100 dollars). Circuit boards are available for this chip.
Another point of improvement, possible with this chip might be to use it to track the position of the laser head. A second laser, infrared, would shine on the substrate. This substrate could be the platform used for printing or the underside of the top of the box that is used to enclose the printer.
Via speckle the position of the laser head can be actively tracked.
Finally, MIT made a nice video of the LaserFactory One. I really like the video. It shows, how extrusion and lasers might be combined one day. Note, MIT doesn't use laser scanning and moves the bundle using a gantry.
The Netherlands is relocating more assets to laser scanning. Recently, AMSystems got featured by TNO,
in it's line up of 25 spinoffs. AMSystems, as far as I know, aims to build a laser scanner with a plurality of laser bundles per prism. They adapted their European patent.
Hexastorm no longer falls under the main claim, as it uses a single bundle, which is really good news.
The Netherlands also supports/is founder of some affiliated startups.
Keiron Technologies, is basically a laser startup which uses laser scanning in combination with laser induced forward transfer. They are affiliated with TNO.
Inphocal is using a Bessel beam in laser scanning. There is also a startup using Bessel beams for communication known as Aircision.
TNO is also setting up a new startup in STED lithography.
All these startups, including AMsystems, are related to HighTechXL. I think it is very possible, one or more will use or are using prism scanning.
I have looked for patents but so far did not find a lot.
04/07/2021 at 16:09 •
It has been a while, the last months I worked on adding motion control to the FPGA.
I ended up starting from scratch. I wanted to move from migen to nmigen and structure the FPGA code better.
A proof of concept is seen in the very rough video below;
Motors are sampled at 1 MHz. The circuit operates at 50 MHz. The system can account for; jerk, acceleration and velocity.
The software consists out of the following elements;
* SPI command interface (receives command and words, copied from Luna)
* Transactionalized FIFO (buffers instruction in sram, copied from luna)
* SPI parser (basically an extension of SPI command interface, with specifics for my
* Dispatcher; picks up commands from the FIFO buffer and dispatches instructions to
* Polynomial integrator: creates pulse train for stepper motors; basically you send the
coefficients for the polynomial and the number of ticks in a segment.
The motor follows the path, coef_0 * t + coef_1 * t^2 + coef_2 * t^3.
The trajectory of a motor is divided in multiple segments where a segment length is typically 10_000 ticks. If is longer, it is repeated. If it is shorter, this is communicated by setting ticks to lower than 10_000. I looked into using bezier curves for motion control. The main advantage is that they are calculated on the circuit straight from actual positions using de Casteljau Algorithm. My FPGA does not have a hardware multiplier, so I didn't implement it.
At the moment, I will focus on adding the possibility for controlling the laser and "finally" do more experiments.
01/23/2021 at 14:16 •
Made a video of the alignment procedure with new updated tool chain. I moved away from the PRU of the Beaglebone to the FPGA and replaced the ueye camera with an arducam. This sounds easy but still took me a year :-).
01/19/2021 at 16:49 •
Recently, I was reading upon the character-by-character reconstruction of the BioNTech/Pfizer SARS-CoV-2 Vaccine .
Most of us, will end up with this in their bloodstream so I thought it was rather interesting. It turns out there was a startup which produced DNA using laser printing . Austen Heinz gives a good presentation of this process below, scroll to time 10.24 min
The startup Cambrian Genomics was founded by Mr. Heinz in 2014. The startup no longer exists and seems to have faced many difficulties. They did manage to raise over 10 million USD. Austen Heinz committed suicide at the age of 31 on May 24, 2015.
His patents are still around, see US 10,822,605 B2 which got awarded in November 2020.
As there are still people funding the patents, there must be people working on it. I looked into the patents for details on the required accuracies. You need optics which provide an accuracy of around 1 micron. This accuracy could be possible with prisms, if you have a reasonable budget. Process uses laser induced forward transfer or laser catapulting.
Quote from patent;
Methods of using emulsion-PCR derived beads by the present assignee have been based on the fact that the bead itself serves as a decent ablation substrate for the approx 1 microJoule nanosecond laser pulse used to induce transfer.
Beads from 1 to 10 micrometers are easily and specifically ejected by focusing light into their plane.
Although ejection optics disclosed by the present assignee can target features as small as 600 nm, it is desirable to generate slightly larger, more disperse 1 micron clusters for use with initial prototyping.
01/06/2021 at 15:51 •
I have made an assembly design of the laser scanner in Freecad using the new assembly 4 workbench.
I am really happy with this workbench. It really helps with the open-hardware concept of the project; without these tools it would not be possible to give other people the ease of use to adapt and add their modifications. Companies like Prusa Research are open source but not open-hardware as they don't provide access to the assembly drawings. They might do that in the future with these new tools.