prism laser scanner

bringing additive manufacturing to the next level

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An open hardware fast high resolution LASER suited for Printed Circuit Board (PCB) manufacturing or 3D printing. The laser head can be used to write to a substrate. I am working on reading from a substrate.

The goal of this project is to develop a laser head for 3D printing or PCB manufacturing which uses a rotating prism and is easy to assemble.
Cyanotype paper is currently used as it can be developed with water.


Specifications are determined by exposure onto a camera without lens and OpenCV. More technical details are available in the whitepaper or the business case pitch.

  • wavelength: 405 nm
  • rotation frequency:  up to 21000 RPM, current 2400 RPM
  • line speed: up to 34 meters per second @ 21000 RPM
  • spot size FWHM: circular, 25 micrometers diameter
  • cross scanner error: 40 micrometers  (error orthogonal to scan line)
  • stabilization accuracy scanning direction:  2.2 micrometers (disabling/enabling scan head)
  • jitter: 35 microns (error parallel to scan line)
  • duty cycle: 47%
  • laser driver frequency: 2.6 MHz
  • maximum scan line length: 24 mm
  • typical scan line length: 8 mm
  • optical power: 500 mW
  • facets: prism has 4 facets
  • prism dimensions: 30x30x2 mm


  • FPGA ICE40UP5K-SG48 with Icestorm toolchain
  • Firestarter cape  (laser driver, 3x TMC2130 stepper drivers, PWM spindle and fan control)
  • Raspberry 4


An image can be exported from Kicad to SVG and converted to instruction for the laserhead. An exposure result on a printed circuit board with close up is shown below.

Resolution below 100 microns can be achhieved. Stitching is between lanes is quite good on cyanotype paper but still a bit uneven on PCB. Exposure below is done without cylinder lenses.

An exposure goes as follows (for the result see above).

Special thanks go to Henner Zeller for his work on LDGraphy. The electronics and software in this project helped me a lot with constructing the laser scanner, see video.
The initial idea of using a prism for laser scanning originates from Dr. Jacobus Jamar. The first system used a plurality of laser bundles in a thicker prism under an angle.  TNO, a research institute of the Netherlands, still pursues this idea, in an entity known as Amsystems.
The current gateware relies on Amaranth HDL and some components from Luna. This is the work of white-quark and ktemkin.

Amaranth HDL gateware for Hexastorm
Optical design

PCB design

Hardware designs
CAD files

Literature Research
White paper @ Reprap

Other Links
Official website


blender file used in render

7-Zip - 30.82 MB - 06/29/2023 at 19:07


Cross scan error measurements for seven prisms.

Zip Archive - 95.89 kB - 04/04/2023 at 13:57



Technical deck presented to selected audience. Deck does not cover LIFT, laser microscope and latest improvements on tech.

Adobe Portable Document Format - 9.11 MB - 12/10/2021 at 08:28



New pitch deck of 16-9-2021, also available as video on Youtube.

Adobe Portable Document Format - 2.03 MB - 09/16/2021 at 17:50


calibration data of current scanhead

Zip Archive - 278.28 kB - 01/25/2019 at 18:50


View all 6 files

  • 1 × prism, 30x30x2 mm edges parallel to < 1 arc minute 40pcs @ 20 euro per piece @ ebetteroptics
  • 1 × Raspberry Pi 3B / 4 with 16GB sd card at least 35 euro's + 9 euro
  • 1 × Brass Laser Module Housing for 5.6mm TO-18 LD 5 euro
  • 1 × BDR-S06J 405nm / Nichia S06J 405nm 22 euro (eBay)
  • 1 × 10x10x1 first surface PMMA mirror 2.5 euro per 20 aliexpress (alternative edmund optics #45-517 18 euro per 10 including shipping)

View all 12 components

  • when mirrors do not follow law of reflection

    Hexastorm09/15/2023 at 10:24 0 comments

    Laser scanning via mirrors is of relevance to prism scanning, being an alternative. For mirrors it is assumed angle in is angle out (law of reflection). Still, this is not always valid. The following article on arxiv goes into depth on the latteral shift and angular shift known as goos hanchen effect and imbert federov effect. It is seems to be simple consequence of Fresnel equations.

    Aberration is small but you would have to account for distance to substrate  and also compound both effect. Details in article

  • 3D printing of ultra-high viscosity resin by a linear scan-based vat photopolymerization system

    Hexastorm09/07/2023 at 16:33 2 comments

    Last july, an article was published in Nature for a new high viscosity vat printing method,
    This method is depicted below, the figure is copied from the article.

    figure 1It uses four rollers to apply a new layer to 3d print a part. The article comes with some cool videos and equations describing the mechanism.

    The method, and this is not mentioned in Nature is not entirely new, see patent EP2272653A1. The only difference i can see from a legal perspective is recoater number 2. I also remember it is not a true vat method. Resin went to a waste box, see number 23.  I think the Admatec machine is a spinoff from this concept. It also uses a a rotating foil, coated with a blade and the remainder is put into a left over box.

    Furthermore, in my white paper on reprap,  i claim the usage of a foil with my Prism scanner.  I made two drawings to protect up and down projection.

    I think the authors of the nature article should consider the following  two patents;
         US8777602B2 (recoater patent)

    Loophole might be not using recoater. 

         US9939633B2  (scanlab, EOS subsidiary patent, reflecting lens)

    Their reflecting lens seems very similar to scanlab. The authors mention the 3SP patent, so I did not include it.

  • Flipping a PCB motor using a ferrite sheet

    Hexastorm08/30/2023 at 14:04 2 comments

    I use a sliding bearing. This keeps costs low and ensures the prism is kept in a given plane. A challenge is that the prism falls if this sliding bearing is flipped 180 degrees.  This is fixed by adding a ferrite sheet on the back of my PCB.

    Materials used flexible ferrite sheet MHLL5040-200 Laird, Magnets MKSA-8x5-ZW-N45 i.e. 8x5 mm, neodium 45 with a black epoxy coating.
    I think that ferrite instead of neodium is possible if the whole contraption was made better.  Ferrite is typically 2-7 times less strong. If the distance would be decreased a bit, which is still possible, ferrite should work.

  • Brief update

    Hexastorm08/10/2023 at 16:08 0 comments

    Two changes;

       -  Layout changed and is now more in line with look and feel of Hackaday.
          Website is generated using Quarto

      -  Decided to further perfect engine, moved from 4 to 8 magnets.  The magnets have a black coating
         which aligns better with the overal design Hexastorm.

  • Laser prism scanning with Bessel like beams

    Hexastorm07/14/2023 at 13:21 0 comments

    I made a presentation on how laser prism scanning might use Bessel like beams. I outline how they are created and how they might be used in combination with laser prism scanning. This due to recent interest to startups like Inphocal.

  • Rendering laserscanner

    Hexastorm06/28/2023 at 21:13 0 comments

    Rendering the laserscanner in Blender.

    File is here

  • Structured Light

    Hexastorm06/23/2023 at 23:20 0 comments

    Claim 1:

    -  I claim the use of two lenses which in combination focus light into a structured optical beam. Between these lenses there is a prism which   can rotate so that a scanline can be formed. The first lens focuses the light parallel to the scanline and the second lens focuses the light   orthogonal to the scanline.

    Claim 2:

    - The optical system of claim one, wherein the focal length of both lenses are different such that they circularize the light source. 

    Claim 3:

      - The optical system of claim one, wherein each of these lenses is similar to an axicon.  The difference with a normal axicon, is that each individual axicon focuses the light in one dimension and not two as a normal axicon. The light is just propagated and not diverted along the other axis. Only the combination focuses the light along two axes, one orthogonal and one parallel to the scanline.

    Claim 4:

      - The optical system as outlined in any of these above claims and in an applications outlined on (  or

    Claim 5:

    An optical systems similar to claim one, which is used in an optical tweezer or laser microscope.

    I adapted this blog as it contained inconsistencies;

      CERN provided more information here


    In the laser prism scanner, so far Gaussian beams are used.  An alternative would be to use a Bessel beam. An advantage of a Bessel beam is that they have a longer depth of field as compared to a Gaussian beams for a given focus size. A true Bessel beam is non diffracting.
    True Bessel-beams are not possible as they require infinite energy.  Bessel beams can be approximated and then called structured light.
    These structured light beams are less diffractive than Gaussian beams.

    A Gaussian beam is created by focusing light into a point.  Structured light is created by focusing light along a line. This is denoted by Bessel beam in the figure below.

    Bessel beams: a potential strategy for laser-induced breakdown spectroscopy  - Journal of Analytical Atomic Spectrometry (RSC Publishing)  DOI:10.1039/D1JA00270H

    Recently, companies such as ASML, Europe's most valuable tech firm according to BBC,  started to support laserscan startups such as Inphocal which use structured light.  Inphocal is based on intellectual property from Cern (WO2019211391A1) Inphocal received funding from HighTechXL, NWO, DeeptechXL and the European Union.

    CERNs contributions to Kicad are highly appreciated. WO2019211391A1 feels incomplete. In short it outlines an improved version of the axicon. This new lens produces a beam which better approximates a Bessel beam and diffracts less. I can understand this due to the greater design freedom as the shape seems mathematically more general to me, but still I would be interested to see the actual differences backed up by optical simulations.  The authors from CERN do not provide this. CERN furthermore does not really goes into the difficulties which arise by scanning a laser bundle.  I can imagine Inphocal uses a galvo scanner from scanlabs and does not have a challenge with cross scan errors.  Galvo scanner are slower than polygon scanners.

    In specific, the authors do not outline how the movement orthogonal to the scanline can be mitigated if a Bessel beam is scanned by a prism. Given my experience with cylindrical lenses and Gaussian beams. I propose a similar solution for Bessel beams.

    For Gaussian beams,  my solution is outlined below;

    Light diverges from a laser diode and is collimated by an aspherical lens. The first cylindrical lens focuses...

    Read more »

  • Realistic laser laser scanner in blender

    Hexastorm06/17/2023 at 21:51 0 comments

    The laser prism scanner can be simulated in blender, I am working on the cylinder lenses.

    In the following image you see a 1 mm laser spot displaced by prism and reflected by a mirror to a photo diode.


    The laser ray is visualized by adding an atmosphere to the volume

    In the last figure a laser deflected by a tilted prism is shown. It impinges on a white sheet.

  • Laser Prism Scanner Summary

    Hexastorm04/12/2023 at 12:51 0 comments

    I made a summary video of my laser prism scanner work.
    This should save you time if you are interested in the topic.

    0:00 - Intro 
    1:35 - Process 
    2:58 - Applications 
    5:00 - Optics: prism more accurate than mirrors 
    5:59 - Optics: displacements caused by prisms 
    7:44 - Optics: rotating polygon mirrors vs rotating prisms 
    10:45 - Optics: position photodiode 
    11:59 - Optics: advanced prism designs
    13:16 - Aberrations: how measurements are made
    14:23 - Aberrations: cross scan error versus jitter
    16:08 - Aberrations: mounting
    16:56 - Aberrations: solutions to mounting
    18:44 - Aberrations: prism imperfections
    20:09 - Aberrations: solutions to scan errors
    21:18 - Aberrations: vibrations
    22:34 - Aberrations: prism mounting using Ricoh motor
    24:04 - Aberrations: new mounting solution
    26:04 - Aberrations: new mounting solution (Freecad view)
    26:57 - Aberrations: measurement cross scan errors
    29:07 - Validation, result of exposures
    29:59 - Positive feedback
    31:20 - Negative feedback
    33:48 - Outlook
    35:08 - Origins laser prism scanning
    37:08 - Challenges with thick laser prism scanners

  • A reply to "The state of open-source in 3D printing in 2023"

    Hexastorm04/04/2023 at 08:18 0 comments

    In the blog state of open source, Prusa complains about cheap 1:1 clones who do not honor the open source ethos and as remedy suggests altering the license.

    The most successful companies, e.g. Microsoft and Apple, in the world are closed source.
    Still closed source seems not to work for a number of technologies; operating systems (Linux) and programming languages (Python).
    In the nature of the firm, Coase argues that the main reason to establish a firm is to avoid some of the transaction costs of using the price mechanism.
    Open source lowers the transaction costs for inbound innovation. Information is more readily available to outsiders and less asymmetric. As a result, the technology grows.
    I think open-source is best suited for "highly" complex products with an initial weak product market fit. It works better for software than hardware. As hardware is harder to reproduce. This leaves the question of monetization.
    Open source software is now monetized by cloud providers who earn money by running it in the cloud.
    Examples are Github, Amazon Web Services or DataBricks.
    It is also monetized by software developers who tailor the software for specific business needs.
    They enjoy large benefits by the fact it is open source. As they can simple hop companies and sell the same knowledge again. A problem with proprietary software is that the new firm or client of the developer would also require a license.

    In your blog you also give an example of solar panels. One example for all is solar panels – the original inventions and processes were gradually copied by Chinese companies. After that, with the help of state subsidies and tax breaks, they drove all competition out of the market within a few years. Today, you have virtually no chance of buying a non-Chinese-made solar panel.
    I agree with your assessment that this makes solar panel manufacturing less profitable. It might also be a reason for a government to intervene using tariffs.
    Still, an entrepreneur can still make money. Once the solar panel becomes free, the challenges becomes getting it on your roof. You might also need advice on how to best place your solar panel. It is very hard for the Chinese to compete with a Dutch solar installation company given the fact they are in China.
    They can also not work in the Netherlands due to regulations.  If China makes printers for free, you might need to alter your workforce or firm. I still see a lot of ways of making money.

    Moving back to the Prusa firm. I would not alter your open source approach but better look at how it can provide unique value. Your company actually pursues a mixed strategy. Part is closed and part is open.
    It is impossible to make a firm a completely "open".  I would not focus on changing the relation between Europe and China or the patent system. These things are external to your company and not under your control.
    You can make it easier for external parties to add new tools to your printer.
    You could give these external parties a slice of the profit.  Goal here is to really think outside of the box and look at your relation with the customer.
    As example, there is a Dutch company called Swapfiets, who offers bikes via a subscription service instead of selling them. This has been hugely successful. I would not advice you to offer a subscription service. Still, it shows that the way you interact with the external parties can be a key differentiator.
    If you control the most popular design of the printer, you should still be able to make money simply as you decide which parts end up in the next printer.
    A successful open source approach, requires more thought than simply putting the source code on the web.
    This was done by Lulzbot and not successful.

    Finally, I partly disagree with your view on patents.
    I believe like you and the Economist that the patent system is broken.  From experience, I believe that most patent applications are a failure.
    Still, you should patent given the opportunity. If you have a lot of...

    Read more »

View all 148 project logs

Enjoy this project?



Hexastorm wrote 12/30/2019 at 15:53 point

No it wouldn't work.. you need edges polished, not the top and the bottom.
I am not shipping out prism at the moment as they r not balanced yet (working on this). I am also working on a FPGA toolchain, will post an update on my progress here soon.

  Are you sure? yes | no

Ben Wishoshavich wrote 10/27/2019 at 04:56 point

Can you recommend a specific polygon motor module on alibaba? I don't know if there are any differences and I'd like to order one. THanks!

  Are you sure? yes | no

Hexastorm wrote 10/27/2019 at 13:37 point

Yes, you should buy exactly this motor . It uses the NBC3111 chip. I had problems with other motors. Make sure you buy at least 2, although they are quite hard to break.

  Are you sure? yes | no

Ben Wishoshavich wrote 10/23/2019 at 21:59 point

Dude, this is some pretty awesome work. I'd love to help refine some of the manufacturing and board designs, let me know how I can best help

  Are you sure? yes | no

Hexastorm wrote 10/24/2019 at 17:55 point

Thanks! There are two other people who have shown interest. I need at least 10 people to do a run as I have to buy the prisms in bulk. Turn around time would be significant. Producing the prism takes at least a month.
I am fixing the low hanging fruits at the moment. It is hard to help with these as you don't have a laser head. I am building a new one but there is still only one in the world :-).
Things you could look in to;

- a better alignment system for the laser; this uses four screws and is over dimensioned --> see my free cad design files

- a better alignment system for the cylinder lenses; the screw system is not really comfortable --> see my freecad design files

-  how do i put my state machine on an fpga; I have been looking into as a replacer for the beaglebone.
This task seems rather complicated but I guess this knowledge could be really help full. The statemachine now runs on pru of the beaglebone and is limited at around 2 MHz.

- how do i balance the prism; i have done some preliminary experiments but still works needs to be done. You could also try to figure this out with a regular polygon motor. Add an imbalance and try to analyze this.

- the slicer or interpolater can only be run on a computer, as it overflows the ram of the beaglebone . Remove this problem, optimize the code.

In the mean time, I am cleaning up the code, building a second head and still have to do more experiments.
I am also waiting for news on the hackaday prize. That's also why I have been quiet on the blog.

  Are you sure? yes | no

Ben Wishoshavich wrote 10/24/2019 at 22:57 point

I'm wondering if there isn't a BLDC motor that could be substituted for the polygon motor, hopefully something that is more available. And then I'd need an encoder. I'll take a look at this, although I suspect going greater than 20k rpm requries air bearings and a custom design.

The rectangular prism does seem to be a challenge. I'll let you worry about that. Out of curiosity, do you know how much it'd cost for a custom order?

An FPGA should be able to handle the state machine. I'm working on the FPGA that's in the Hackaday Superconference badge, and it's got an open toolchain. It might be overkill though. The ICE40 may be better(and cheaper). I might be in the minority in that I'm not sure this is a huge priority, as your electronics are pretty cheap. It's probably a pretty significant time sync to rewrite the assembly for the PRUs into a state machine. I'd probably focus on a command and control system to interact with GCODE or something else.

 I could jump into the MCAD, but I only know Solidworks. I suspect someone else might be better suited for that.
At work, we have specifications for balancing motors for EVs. The most relevant standard is ISO1940. Let me know if that's useful for you. Usually a balancing machine is used to detect vibrations while the part is rotated. They're pretty rare and fairly expensive though. They do make some simple ones for balancing quadcopter props you could look into. Usually you have to add or remove material in a specific spot to make it work.

I already have some of the parts you've used. Perhaps it won't be as hard to duplicate some version of this as I expect.(expect for that lens).

  Are you sure? yes | no

Hexastorm wrote 10/25/2019 at 17:13 point

-  i wouldn't substitute the motors; they have been used in this application for years by a large industry. Rotating polygon mirrors are produced in the tens of thousands. Motors can handle up to 21000 RPM.  This is more than what is needed at the moment, 2400 RPM, as the beaglebone can't go faster.
- custom order is around 500-600$ and MOQ is 10. for the prisms
- Henner zeller wrote a GCODE parser for the beaglebone called beagleg; my idea is that this used and you simply flip the machine between gcode mode and laser writing mode
- never heard of this standard good tip
- all parts are easy to obtain including lenses, motor etc; the only challenge is the prism and time. You will need time :-)

  Are you sure? yes | no

rajhlinux wrote 01/01/2021 at 08:17 point

well you can count me in, i'm interested with this project

  Are you sure? yes | no

Robert Mateja wrote 07/31/2019 at 11:48 point

Congratulations on winning Hackaday Prize 2019!  (at least in my opinion)

  Are you sure? yes | no

Hexastorm wrote 08/01/2019 at 09:30 point

Robert, thank you for supporting me! Winning the prize would be amazing.  My current target is to get other people to try out the technology, I am really trying to make it more accessible. I hope I can show an improved prototype of the scan head soon.

  Are you sure? yes | no

Conny G wrote 05/27/2019 at 12:36 point

What material is the prism made from? How is it manufactured?
Can i make it in my "maker lab"?

  Are you sure? yes | no

Hexastorm wrote 05/29/2019 at 11:39 point

Prism has the following properties; 2 mm thick, 30x30 mm square,  faces 60/40 < 5 arc min, chamfers 0.10 – 0.30mm, edges Polished 60/40, top bottom polished 60/40.   You will have to discuss details with manufacturers in China over Alibaba. I made the first in a maker styled lab, a description of the process is in this log

  Are you sure? yes | no

Gravis wrote 02/03/2019 at 19:16 point

I'm also interested in the possibility of using a motor from a hard disk drive instead of a breaking down a polygon motor.  HDD motors are cheap to buy and (as I understand it,) contain an encoder and have screw holes which makes affixing things easier.

  Are you sure? yes | no

Hexastorm wrote 02/04/2019 at 08:48 point

HDD seem too slow.  They typically spin at 5400 or 7200 RPM.  At the moment, I can go up to 24000 RPM with polygon motor. For some applications, I would like 50000 RPM or 70.000 RPM, like the roadrunner sold by precision laser scanner. Also the motors are not too expensive, they are like 20 euros. I understand 20 euro's can still be a lot but if you look at total costs; you can better pay attention to other components.

  Are you sure? yes | no

Gravis wrote 02/05/2019 at 06:00 point

Oh, I had no idea you were planning on high speed.  Where can you get the motors in the 20 euros range?

  Are you sure? yes | no

Hexastorm wrote 02/06/2019 at 13:40 point

You can find polygon motors at alibaba ( .  The system is a proof of concept; for desktop PCB prototyping 2400 RPM is fine. If you plan to compete with Kleo . You will need at least 50K RPM.  An option would be to encase the prism and remove the air. This will reduce the drag. You could also fill the encasing with Helium as it has low drag and a high thermal conductivity.  Like the roadrunner the encasing windows would be tilted out of plane to minimize back reflections, see

  Are you sure? yes | no

Gravis wrote 02/03/2019 at 15:57 point

My suggestion for this project is to isolate the scanner from the 3 axis robot part so that the scanner could be made into a tool that can be changed out.  I would also ditch using BB's PRU and instead use a dedicated chip (and maybe a RAM buffer) and connect it via CAN bus.

  Are you sure? yes | no

Hexastorm wrote 02/04/2019 at 08:58 point

I intend to isolate the scanner, and design it for specific machines. I like the idea of having a dedicated chip. In the past I used a FPGA (Xula-LX25) with RAM as  bufffer. I can imagine there are even better options. The problem is that developing a dedicated board costs time, money and a lot of experience. Zeller made a very accessible code for the Beaglebone, so I went with that. You are looking at a proof of concept. It's a technology demonstrator. Anyway if you have recommendations; or some example code; feel free to share. 

  Are you sure? yes | no

Gravis wrote 02/05/2019 at 07:48 point

Considering this is a project where accurate timing is vital, I think an XMOS processor (e.g. XS1-L4A) would be a good fit.  Each 100MIPS processing unit is 100% deterministic with fast GPIOs.  I don't know the rate of data throughput you need but it may be easier to just cache to workload on a local FLASH chip than stream it.

  Are you sure? yes | no

Hexastorm wrote 02/05/2019 at 10:53 point

XS1-L4A is nice... but I rather like something with lot of support and examples... probably first gonna optimize the current code and balance my prism.

  Are you sure? yes | no

Gravis wrote 02/05/2019 at 20:37 point

XMOS stuff actually does have lot of support (, examples ( and even an IDE but I somehow missed the part where you wrote that didn't want to build a custom board.  Sorry about that.  XMOS chips make it easy to glue things together since it's 99% software so it doesn't take too much skill to make a board with them.  Consider enlisting help to make a board as there is a good chance it will alleviate timing related issues.  Good luck! :)

  Are you sure? yes | no

rajhlinux wrote 01/03/2021 at 13:24 point

This is a good idea, but honestly I think the best thing is to focus on getting the precision as perfect as possible. There's no consumer grade PCB maker device that can give traces/spaces resolution down to 0.01mm. It's crazy we are still using tonner transfer and UV exposure. I'm planning to build a CNC gantry made from granite, magnetic actuators and air bearings to get the most accurate, friction free, repeatable long term PCB manufacturing with >0.7 traces and spaces. But yes, would be nice down the road to have the scanner head removed for another tool... but for now precision is priority. Precision & Resolution is the reason why this project brings my interest and everyone here.

  Are you sure? yes | no

Paul wrote 11/05/2017 at 03:49 point

You've certainly done your homework very thoroughly, and I see that in your application with very small optical cone angles (large focal ratio), the optical aberrations and field curvature appear to be tolerable.  That's great.

One question: You say that previous scan techniques require a large (and therefore expensive, you argue) f-theta lens, which must have one dimension at least as wide as the scan line.  In your approach, your polygons must be larger than the scan line length, but in *two* dimensions, making the volume of your optical element much larger.  Since either shape would use identical materials and fabrication processes in volume production (i.e. injection molding), one would naively expect the smaller element (the f-theta lens) to be cheaper.   How is this line of reasoning flawed?

  Are you sure? yes | no

Hexastorm wrote 11/05/2017 at 10:51 point

A telecentric f-theta lens requires one dimension at least as wide as the scan line. A non-telecentric f-theta lens does not require that.  In my approach, the polygon must have one dimension longer than the scan line. The second dimension is 2 mm. An f-theta lens consists out of multiple lens elements, e.g. a 3 element f-theta lens. These elements have curved surfaces. The prism consists out of a single element with a flat surface. You can't make the f-theta lens out of plastic, so you would have to injection mold quartz. I am unfamiliar with the prizes for that. Besides most likely a higher price and the fact you have to use multiple elements, you also need to worry about patents. Envisiontec patented the usage of reflective polygons; US 9079355 B2 . Finally, you need a thick reflective polygon as thick polygons can deflect collimated bundles with a large diameter and these can be focused to smaller spots.  A transparent prism uses a focused bundle and therefore typically can be thinner, which keeps the price of the bearing lower.

  Are you sure? yes | no

Paul wrote 11/05/2017 at 15:55 point

You have clearly thought about this a great deal, and have your arguments worked out well.

I wasn't considering that you might be requiring quartz.  I would have guessed even BK7 would be overkill for this application.

I mention injection molding because I look around my offices and see several laser printers.  Each of them contain a laser scanning unit with a rotating (reflective) polygon and a f-theta lens arrangement, with the final element being very large (>200 mm long).  All the optical elements of the ones I have inspected appear to be injection-molded PMMA or similar plastic.  The entire laser scanning unit must cost considerably less than $50, given the prices of the printers (all less than $200, two less than $70).  Granted, these are produced in huge volumes, but they serve as existence proof that these scanning systems with large optical elements are not intrinsically costly.

  Are you sure? yes | no

Hexastorm wrote 11/05/2017 at 16:52 point

PMMA absorbs light at 405 nm. The laser printers at your office use 800 nm and low power lasers. I use 405 nm and high power lasers. So yes; there is concrete proof that PMMA injection molded systems are not intrinsically costly. There is no proof that quartz systems are not intrinsically costly.  It's unclear what the prices of these systems would be .

  Are you sure? yes | no

Paul wrote 11/03/2017 at 13:21 point

A good variation on the usual way.  I build a few instruments based on this and similar methods between 1985-1989.  A couple of important notes:  

1. The scanned field is NOT flat: The optical distance to the target plane *increases* as the polygon rotates away from normal.  Not only is it geometrically longer, some of the increased  path length is in the high-index polygon too, increasing the path length even more.  The result is a curved focal or scan plane.  One of my instruments actually depended on this: a rotating polygon was used to tune the optical path length inside an optical resonator cavity, to adjust a tunable laser that was phase-locked to that cavity. 

2. You get some significant spherical aberration when you focus through a thick window like that, for similar reasons: the light rays at the periphery of the optical cone take a longer path to the target plane than rays going through the middle of the cone, with the result that they focus at a different depth.  For a laser at f/50 (or whatever it is), this probably isn't significant, but in an imaging system at f/2, it seriously degrades focus. 

  Are you sure? yes | no

Hexastorm wrote 11/04/2017 at 22:09 point

Paul, thank you for your reply!
A transparent polygon scanner with a single laser bundle was first patented by Lindberg in 1962.  The scan field is not flat and you can get some significant optical aberrations. A full numerical model is available here . A description of this model is available in the technical presentation. The result shows that in practice the scan field is flat and the optical aberrations are not significant for the current spot size and line length.

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Hexastorm wrote 11/03/2017 at 11:58 point

Well this is the first comment! If Hackers are interested in transparent polygon scanning let me know :P ..

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