Mirror, Mirror on the Wall

This week has been relatively quiet. I got some super nice mirrors from Thor Labs, so now I am thinking of ways to mount it in an enclosure. I don't have any aluminum thick enough to take a 1" mirror, but everything is theoretically working physically, so I am going to look back into the state of the linear detector, see what progress has been made on it by the past group, and go from there, because I have all the parts of a working spectrometer, I just need to start thinking about things like radiometric calibration, and correction for the nonlinear response of the mirrors, gratings, stuff, like that.

Progress on the board's brain has been going well. Gordon's schematics are coming together nicely, and an initial prototype should be done fairly soon, so eat your heart out, raspi. On a side note, I noticed that Gordon's commit logs never seem very large, but Git simply can't capture the effort that goes into making such a large schematic (curse you efficient representation!). It will definitely give the spectrometer some serious power when it comes to processing and display.

Also, we will be outlining our progress further at the next RCOS meeting. I believe Nick will also be joining us to detail his progress on the embedded GUI framework to complement our embedded Linux board. He has made some amazing progress, along with excellent documentation, although dashboard refuses to recognize his subversion repo. We have recently run into some irreconcilable differences at the kernel level which require us to get a new dev board, so things have been quite on that front as well. Nevertheless, Nick has made stunning leaps in helping us cultivate a complete system for this board, and we're happy as clams to have him on board.

That's all for this week, once again, we'll be detailing progress next Tuesday at RCOS, so look forward to the live presentation or the recorded video from Ben Vreeland. Thanks for reading.

Big Changes and Important Progress

There have been exciting changes and big news since the last post. I might break it into several posts to cover everything.

First, let us start with the brain. The initial plan was to use a TI ARM microcontroller to control the spectrometer, run the lcd screen, and talk to the computer. Upon further consideration and careful thought, we have been working with a small, ARM-based SoC from Allwinner, the A13. This will allow everything we need plus more: digital and analog GPIO, native LCD driver, plus all the good bits that a full linux distribution would have (sans X server). I'll detail plans for this subsystem as they come along, but the plan is that this control system will be its own device, that will be embedded in the spectrometer, but be a neat board all by its lonesome. On the software side, this opens up entirely new worlds. With the decision to move to a full embedded linux system, we have also opted to use the QT application framework, streamlining the process for making a fluid and intuitive experience using one of the stablest open source projects in the game.

Next, let's talk about progress on the actual spectrometer. So far it's been really promising. After several iterations of machining the spectrometer profile into polycarbonate, I have arrived at a prototype that I'm very comfortable with milling into aluminum. Compared to theoretical design and calculation, it's at least as accurate as a pair of calipers can confirm, using two separate laser sources (532nm and 650nm). Right now my process involves cutting the curvature into the material and then pasting a strip of mirror film onto the curvature to prototype expensive mirrors, which works for proof-of-concept, but won't cut it at the calibration stage. Anyway, the next step of the game is to get optical mirrors to go with the diffraction grating, and start to contact suppliers in China to source components for prototypes in the near future.this breakthrough has been huge from my perspective, and I'll provide pictures of the prototype later in the week. 

That's all for now, be sure to check out the repo for any updates on circuit diagrams, cad diagrams, and code, and comment if you have any questions.