An open hardware fast high resolution LASER suited for Printed Circuit Board (PCB) manufacturing or 3D printing. The laser head uses a rotating prism instead of the industry standard rotating mirror circumventing patent US9079355 valid up to 2033 and many more; e.g. US10209226B2.
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. The current electronics provide the possibility to cut a PCB with a spindle.
Specifications were determined from the proof of concept model 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)
Firestarter cape (laser driver, 3x TMC2130 stepper drivers, PWM spindle and fan control)
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. The idea is that through holes are made with a spindle. There is a project on Hackaday where a PCB is cut with an EDM.
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.
Recently, I was reading Hacker news and realized I hadn't created prior art in the field of photo-acoustic imaging. The photoacoustic effect or optoacoustic effect is the formation of sound waves following light absorption in a material sample.
Basically the schema is as follows; you scan with a laser beam over tissue or gas and then detect the produced sound waves. From it you can determine the material properties.
The effect was discovered by Graham Bell in 1880. A general patent by Hitachi can be found here US5781294A. The claim is quite nice and general but the patent expired in 2012.
Olympus corp filed a patent for using this effect with a galvo scanner. The patent is valid up to 2035 and its number is US10209226B2.
Let's have a look at claim one;
"... the scanning unit includes a movable mirror which changes an angle of incidence of the excitation light incident on the objective lens, and ... "
Prior art is constructed as follows;
"... the scanning unit includes a scanning prism which changes an angle of incidence of the excitation light incident on the objective lens, and ... "
A more complicated patent example from 2018 with two beams by Yokogawa electric corporation can be found here US20180140199A1 .
As we can see the patent propose the use of two frequency shifted beams from the same light source which are then coupled into a single point by a variable focus lens. However, what is also clear is that this lens is positioned after the light scanning unit. I claim that the lens is positioned before the light scanning unit in a prism scanner. This was not obvious to the claimant as it obviously thought of the light scanning unit being a galvo scanner or a rotating mirror.
I claim the reverse effect. So here an ultrasound wave is produced and the result is detected via an interferometer which uses a scanning prism. The idea is similar to the optical coherance tomography setup I discussed earlier. A patent by Hitachi can be found here US20130160552A1 but it expired as they seem to have stopped paying the fee.
A Dutch research group from the TU Twente used the effect to detect breast cancer. The optical effect is non-invasive but does not have a deep penetration depth. I claim the same but then for a scanning prism and also other forms of skin cancer, skin deseases, cancer etc.
This was an experimental project so I don't believe you can buy one commercially. Cordin does sell them and they have mirrors rotating at 5000 RPS which is like 300.000 RPM. This is quite nice as it serves as an example of how fast prisms could rotate. These cameras with rotating mirrors are used in research and have been used to detect nuclear explosions etc.
I thought it was nice to give some update on the progress. Most of the work I did was in the software domain.
beaglebone now works with cape universal and not with a predefined cape pins can be changed on the fly without booting linux.
if the machine turned on the laser turned on as well, the startup procedure has been changed so the laser doesn't turn on by accident
in the proof of concept experiment, the laser module was turned off after each lane and turned on before a new lane. With the new software you can continue to expose without turning of and on the scan head.
the c++ library for the TMC2130 stepper has been wrapped in python
I have added the possibility to expose with a single facet. In my earlier post, I outlined this can be done via the facet times. I have however chosen to do this by an internal counter which simple counts the facets and assumes a facet is never lost.
variables are now centralized in one location. They used to be sprinkled all over the place. You don't need to recompile the assembly to change the variables of the scanner
The assembly code of the scanner and the python code have been refactored. I would say the code is much more readable now
The spinup state changed. The laser is spin up and then it is tested whether it passes a threshold check. The laser turn on time is however much smaller than this threshold. This used to be the same.
I have also build a second laser module and fixed the z-endstop in my test setup.
As always let's create some more prior art;
Blackbelt has a patent called for an infinite conveyor belt printer see https://patents.google.com/patent/NL2018728B1. This was scrutinized by Hackaday. The patent so far only seems valid in the Netherlands and the conveyor belt has to be planar with the horizon, see words ".. parallel met de horizontaal is gelegen..." at the end of claim 1. As such, I claim a machine in which the belt is not planar to the horizon but under a tilt angle. I claim an infinite conveyor belt printer in which both a laser head and extruder is mounted. Possibly the extruder deposits a polymer which is polymerized by the laser. This polymer can be viscous so it stays on its place.
I also claim the use of a prism scanner in data gloves. This can be used to write or read from a substrate from a glove. I earlier claimed the Hexastorm was connected to a robotic arm like the Dexter. In industry 4.0, workers are equipped with data gloves to check wether they are operating within requirement. In the proglove as shown here https://www.proglove.com/ a camera is added to the hands of an operator. I can imagine a prism scanner is placed in this data glove. This prism scanner could record information or write information on substrates. It could detect biological markers, or QR codes. It could detect cells or give a marking to a product. It could be used to determine the final position of a product which has to be precisely placed.
Good news! I received the NBC31111. The facet times look to be good and the motor is quiet again. In other words; the laser module is working once more. I have quite a busy weekend ahead, but will try to make a new exposure on Monday.
The facet times are;
Note that i ignore the first 100 lines as the prism doesn't seem to be stable enough.
output from script: ---------------------------------
Earlier, I reported that the facet times recorded by the diode can be used to determine the facet number. In the above, you can see that one facet has facet times smaller than 12400.
If the jitter allow per period is set very small, no difference can be perceived in facet times. For the proof of concept module, I used a jitter allow of 1/3200. All the facet times are then very similar and jitter is quite minimal. With a jitter allow of 1/100, I can determine the facet and use an interpolation table to reduce the jitter. I am not sure which strategy works best, but I do claim I possibly use one of these methods. I also claim I use information by an acceleration sensor to determine whether my prism is rotating smoothly or an earthquake is interrupting operation. I also claim I use this information to correct the data sent to the prism scanner by calculating a more accurate position.
Earlier I discussed that the prism ideally is balanced and how this could be done. The acceleration and position of the prism needs to be measured during rotation. The first step is determining the position of the prism, i.e. rotor. Two options were considered; detecting a marker with laser or detecting a marker with a camera. I went for a camera as it seemed more robust. Also, the position of the weights needed for balancing can be visualized with the camera. In specific, the UI3060-m-GL, specs are; USB 3.0, CMOS, 166.0 fps, 1936 x 1216, 2.35 MPix, 1/1.2", Sony, Global Shutter. I used a shutter time of 0.019 milliseconds and a ring light illumination. Having a camera with a global shutter is key, rolling shutter cameras I tried didn't work.. Initially, I thought the ring light would be useful as strobe light but the camera has so short exposure times it just needs additional light. I am planning on building a dedicated setup, see github, but used the current laser module for the test. The setup is as follows;
Camera exposes from the top using a lens with a focal length of 12 mm, ring light is given 24 volt via power supply.
As you can see I used the mirror and not the prism. The mirror is already balanced and can go up to 21000 RPM making it better for exposure tests. At 0 revolutions per minute the mirror looks as follows with auto exposure settings;
I did not modify the mirror. In the ring you can see two markings. This is the weight used to balance the prism. The outer black dot, outside the ring, seems to be made with a marker. This seems to be used to determine the position of the rotor. At 21000 revolutions per minute the mirror looks as follows with 0.019 ms exposure time; You can see a reflection of the ring light as the illumination is not really proper. In the final setup, I should use a better diffuser so you don't see the positions of each led.
made a pitch which is more suited for business case minded people
still waiting for the delivery of new NBC3111 mirror motors as I have broken mine. The new setup "works" but is not practical without these mirror motors. The prism makes much more noise and can converge into two modes. As a result, the prism has to be restarted 50 percent of the time. The noise reduces at lower speed but the two modes remain. This was not the case with the NBC3111 which had a flawless operation at higher speeds. I have therefore decided to focus on balancing the prisms for now and waiting for the NBC3111. The new motors should arrive somewhere next week. The current plan for the prism balancing setup is that I will use a MMA8452Q to read out the acceleration. The position of the prism is monitored using a marker and a stroboscopic camera.
I also claim the use of prism in the industry of thermal plate setters. Another patent by Apple has been revealed for scanning mirrors, see display device US2019/0285897A1. I also claim this patent but than for the case of scanning prism.
I wanted to share a quick video of the alignment setup. The prism is running 2.5 times slower than in the proof of concept model. I have also removed the cylinder lenses for now as this simplifies alignment. The focus is on a robust setup for demonstrations and later quality.
As always, lets generate some more prior art;
non-planar 3D printing with prism scanner to avoid situation like the one with US10005126B2
I can envision a liquid or viscous fluid is applied with an extrusion nozzle or inkjet head and is cured with the prism scanner. This could also be a viscous liquid applied with a blade. The patent talks of a correction factor that is calculated on basis of the slope. This is done to alter the extrusion. I claim that an optical measurement is done of the substrate to determine the correction factor (so it is done from life data during the experiment not from already existing cad data!!) I claim that the amount of liquid that is extruded is constant (this is not altered). The prism scanner decides which part of the liquid is solidified. The remainder is possibly sucked up with a squeegee and pump or applicator bar and pump. I can envision a similar process but then one were powder is blown and then sintered with a laser guided with the prism.
I can envision this is done in a hospital setup to a human or in an operation or for inspection of mechanical parts. I also claim the area "food printing". You can for instance cure egg whites with IR radiation to trigger or monitor a Maillard reaction. I claim belt like printing with prism scanner (so you print on a rotating belt, e.g. blackbelt 3D). I also claim that a prism scanner is used to check the indentation in a hardness tester, at the moment a lot of companies use a camera. I claim that a prism scanner is used to check the indentation, for example see the hardness testers by Innovatest Europe.
I made it to the Hackaday Prize 2019 semi-finals! I am really happy with the feedback from the community and the honor to be among these twenty amazing finalists out of these even more amazing applications. I have seen great projects on Hackaday; not only in this contest but in general. The two most related to my project that were featured on this site are; OpenExposer and Ldgraphy.
The best thing is that Hackaday gives me an even bigger excuse to work on the project. I aim to show once more that I have a working prototype and will try to create PCBs. These results can then hopefully be used for the final video. I will also try to make a brief technical presentation. In the 3D printing realms the most important patent I am able to circumvent is US9079355; the scanning mirror patent by Envisiontec which is valid up to 2033. I have mentioned others. Recently, I got informed that Apple Computers filed a patent for a Scanning Mirror Display Devices. It's a virtual reality set, like the Fiber Scanning Display I discussed earlier from Magic Leap. Obviously; I claim everything, including the fancy pictures and sensors, Apple Computer claims but than for "Scanning Prism Display Devices" I call this prior art, see my earlier blog.
Just a quick update; I have mounted the laser head back on the frame. All the electronics work and the machine is good for a few tests. As said, I have removed the cylinder lenses to increase ease of use. Due to a wiring error I blew up the polygon motor with chip NBC3111, I have replaced the polygon motor with motor with the chip Panasonic AN4000A. This motor produces a lot more noise at the same speed. It can effect future measurement, I have ordered new ones but have to wait 2 weeks. The white paper placed on the build plate is to mark the area needed by the scanner. You can see a blue markings for that. A laser head has a greater height tolerance than a 3D printer nozzle, so leveling is not really an issue. The laser is far out of focus here, the head is typically closer to the paper.