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open hardware fast high resolution LASER

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

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

Electronics

  • FPGA Ice40HX4K with Icestorm toolchain
  • Firestarter cape  (laser driver, 3x TMC2130 stepper drivers, PWM spindle and fan control)
  • Raspberry 4

Status

An image can be uploaded to the scanner and exposed on a substrate. An exposure result on cyanotype paper is shown below.
Resolution looks to be around 100 microns. Stitching still needs to be fixed, results in white lanes.
I am currently trying to bring the product to production. I also will try to read information from the substrate ( this is actually quite easy).

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

Acknowledgement
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 prism for laser scanning originates from Dr. Jacobus Jamar. This system uses 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 Nmigen and some components from Luna. This is the work of white-quark and ktemkin.

Software
Hexastorm fork of LDGraphy
Optical design
old FPGA code

Electronics
PCB design

Hardware designs
CAD files
Cartesian frame was donated by FELIXprinters.

Literature Research
White paper @ Reprap

Other Links
Official website

analysts_presentation.pdf

Pitch intended for analysts who want to get a brief overview of the key markets prism scanning will disrupt.

Adobe Portable Document Format - 781.75 kB - 09/24/2019 at 08:39

Preview
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pcb_scanheadfixed.pdf

schema of the pcb for the scanhead

Adobe Portable Document Format - 45.07 kB - 09/23/2019 at 13:51

Preview
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bomlist.ods

bill of materials for the photodiode detector

spreadsheet - 13.26 kB - 09/23/2019 at 13:33

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scanheadpcb_bom.ods

bill of materials for the scanhead pcb

spreadsheet - 13.04 kB - 09/23/2019 at 13:33

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firestarterbase_bom.ods

bill of materials for the cape of the beaglebone

spreadsheet - 14.97 kB - 09/23/2019 at 13:32

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View all 8 files

  • 1 × prism, 30x30x2 mm edges parallel to < 1 arc minute 40pcs @ 12 USD per piece @ ebetteroptics
  • 1 × Raspberry pi 3B / 4 at least 35 USD
  • 1 × BPW34-B (photodiode) 7 USD (works also without a blue enhanced photodiode)
  • 1 × Laser diode housing chrome with copper 4.9 USD
  • 1 × BDR-S06J 405nm, 500-600mW Blue-violet Cut-pin Laser Diode 30 USD (ODIC Force)

View all 12 components

  • Image of deep state Hexastorm released

    Hexastorm07/19/2021 at 08:34 0 comments

    The team sponsored and owned by the Dutch State has released an image of the engine dubbed "deep state" Hexastorm.

    The engine is shown below;

    A maxon motor drives an octagon prism.  The festo tubes are to put air in the air bearing.
    The copper element is for water cooling of the laser tubes.  The above image is from 2017. The engine apparently hasn't changed since then. You can see they use a Spartan 6 FPGA chip. 

    As cool as the image is, they still have the following challenges;
      - build a robot to mount the aspherical lenses ( they now have a crazy screw system)
     -  get circular spots
        They assume special asperical lenses can be made which circularize laser beams.
        I doubt it and even if it's possible this
        would be so useful it is a business case in its own right. I would immediately buy these lenses.
        Formlabs, Envisiontec (Desktop Metal) would probably buy these as well..
     - they have to show their engine has a competitive advantage with respect to Hexastorm.
       I am quite sure a lot of people will prefer not to deal with patent holders.
     - achieve uniform exposure with all lasers and facets
       This engine is for sure not able to do that. I tested it.

    Hexastorm has the following fundamental advantages;
      - their engine needs to be tilted, mine does not
      - my engine is simpler as it uses a single laser bundle.
        The original engine violates the KISS principle / Occam's razor.
      - my engine is more cost effective, the price of the actuating unit with prism should be less than
        35 euro's per laser. 


    Anyhow, great they put the image out there. I even saw, one of the original inventors Jacobus Jamar is back on the team.  
    I thought it was nice to share with the folks from Hackaday. As you now start to understand, how I "hacked" and "open sourced"  a "deep state" technology.




  • Dutch State increases funding for deep state Hexastorm

    Hexastorm07/15/2021 at 15:00 0 comments

    NWO grants around 250K euro's funding to AMSystems in Takeoff 2 financing. As said,
    AMSystems works on an earlier version of Hexastorm which uses a plurality of lasers per prism.
    The idea is that these systems have increased throughput.
    There are multiple issues with this technology. As you can see in the image below.

    The laser spots are not uniform.  This can be seen directly.   They have not the same power and are "elliptical".
    The copper elements is used for water cooling. The screws are used for "aligning" the laser.  Back in 2017, they planned to fix alignment with a robot.  They actually build a robot but I guess they will build a new one.


    I have recently ordered 40 pieces of prisms and plan to start selling mounted prism on mirror motors online soon.
    This allows makers around the world to build their own "deep tech" and "deep state" open hardware laser scanner,

  • Rotor history

    Hexastorm07/06/2021 at 10:04 0 comments

    After my last post, @Gravis wondered if it would be any help to have a motor driver that compensated for being slightly out of balance?

    In short I think so yes.

    The prism rotor is a key component of the laser scanner. It might be good to go over the assumptions surrounding the rotor.
    The project start with the assumption that it is not possible to get a laser grid. There are ways around this, e.g. laser with a DMD device. There is also research into nano-lasers; which could possible form a laser led screen. All these technologies have their limitations, due to cooling, diffraction or focusing of the laser. A way around this is moving the laser bundle either by mirrors or prisms.
    Rotating prisms have a lower cross-scan error and require different optics then rotating mirrors.
    The Netherlands is especially interested in lithography due to the regional importance of ASML.
    The original prism can be seen in the image below. There are other images but this is the only image in the "public domain".
    The original prism is relatively large, in the order of 20 cm and rotated using an air bearing.
    It makes a lot of noise.



    After studying the laser market for some time. I realized that if there is market for prism scanner with a plurality of bundles, there must be for a single. The rotor design present in laser printers is thought out extremely well. The current prism dimensions are simply based on these constraints. This probably needs to be changed in the future.
    I could imagine the prisms are made smaller. This partly depends on manufacturing capabilities of the prism and the desired line length.
    The prism could be lifted by an air-bearing or electromagnetic field. It could be kept in glass housing with a lower drag gas like Helium.
    In such a configuration, I imagine that the position of the prism can be optimized during rotation.
    I still need to look into how prisms are rotated by lasers. But I can imagine that a disk which can be rotated by an optical field can simply be attached to the prism.
    Another option would be to add coils or magnets to the prism which would allow it to be rotated without contact.

  • Rotor balancing update and links

    Hexastorm07/01/2021 at 15:49 1 comment

    I balanced a prism using the single-plane 2 run method. 
    Let's look at a plot of the polygon motor with AN44000A chip and an unbalanced 30x30x2 mm square prism. 

    A clear peak is present at 50 Hertz for both the acceleration and infrared spectrum.
    The rotor is pulsed at a frequency of 10 Hertz. It apparently spins five times faster.

    Before adding a weight the following measurements are obtained;
    Adding a weight at the exact opposite location reduces the accelerometer amplitude.
    The rotor tends to jump to different frequencies. The NBC31111 is more stable.  For a frequency of 30 Hz the NBC31111 needs to be pulse at 180 Hz. The AN44000A needs to be pulsed at 5 hertz to achieve 33 Hz.

    Mirror motors have 5 pins; PWM, MOTOR_EN, GND, Voltage and LCK_PIN.
    PWM is speed control. GND is ground. Voltage is the supply voltage, ideally 24V. LCK_pin is
    false if encoder and signal are not in sync. I cannot confirm the function of LCK_pin and MOTOR_EN.
    Changing them or looking at their input does not reveal any activity.
    I will try to expose with the AN44000A. So far I only exposed with NBC31111.

    Finally, Max who bought the first prisms found some interesting links.

    Baraja
    Baraja is building a LIDAR scanner which uses a prism with an uneven number of facets.
    They do not rotate the prism but change the frequency of the laser.
    https://www.baraja.com/

    DIY linear motor
    There is an instructable of someone who build a DIY linear motor. In the first machine with a prism scanner a linear motor was used.
    https://www.instructables.com/DIY-IRONLESS-LINEAR-SERVO-MOTOR/

  • Aramco Patent: oil reservoir applications

    Hexastorm06/25/2021 at 08:38 0 comments

    Saudi Aramco got granted patent US10018817B2 in 2018, Adaptive optics for imaging through highly scattering media in oil reservoir applications, in claim one the following is read "two pairs of lenses with two galvanometric scanners"


    I claim the whole patent but then using a similar system with "two pairs of lenses with two prism scanners" which should allow me to circumvent the patent.
    Competitive advantages; lower cross scan error and increased throughput.

  • Digital Twin

    Hexastorm06/18/2021 at 13:44 2 comments

    I made a video of the optical design, simulations are done with pyOptools and rayopt.

  • holographic imaging

    Hexastorm06/13/2021 at 12:31 2 comments

    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.

    Anyhow, what is even more interesting is that they also seem to user laser writing to a substrate to  create holograms.
    See the video below

    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;


  • digital holographic microscopy

    Hexastorm05/29/2021 at 11:40 0 comments

    I found a technique, i did not consider earlier.

    Digital holographic microscopy (DHM) is digital holography applied to microscopy.

    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

  • New video

    Hexastorm05/21/2021 at 16:44 0 comments

    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.

  • Gateware working with motion and laser

    Hexastorm05/14/2021 at 16:23 0 comments

    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.

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Discussions

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 https://nl.aliexpress.com/item/32824649951.html . 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 https://github.com/m-labs/misoc 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 https://github.com/hstarmans/ldgraphy/blob/master/interpolator/interpolator.py . 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).

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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 :-)

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

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

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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 https://hackaday.io/project/21933-open-hardware-fast-high-resolution-laser/log/167433-how-to-be-transparent

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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 (https://www.alibaba.com/showroom/polygon-motor-ricoh.html) .  The system is a proof of concept; for desktop PCB prototyping 2400 RPM is fine. If you plan to compete with Kleo https://www.youtube.com/watch?v=7R464iHaTQU . 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 https://precisionlaserscanning.com/2016/03/road-runner-70000-rpm-polygon-scanner-solves-the-noise-problem/

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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. 

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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.

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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 (https://www.xcore.com), examples (https://github.com/xcore/) 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! :)

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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.

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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?

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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.

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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 .

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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. 

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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 https://github.com/hexastorm/opticaldesign . 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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