fsilva

Just to add to your comment, even so that the energy in each pulse is less than 100 billion times less than the energy from bright sunlight emitted in a second, it is still significant, but the number of laser pulses per second is key to knowing if the (peak) intensity of the laser is dangerous to humans or not, as they accumulate over said second. If you only had one pulse per second at 40 mW you would be looking at 30 mJ of energy per pulse, capable of making a nice plasma in air if focused, or machining metal. However they are probably working at 100s of kHz in order to be able to measure an image fast enough, so the energy per pulse is much lower. Key here is the fact that our eye's lens doesnt transmit 1550nm so well, so the interaction with the eye doesnt involve focused light on the retina, hence the interaction intensity is much lower as the light is spread over most of the surface of the eye. Hence they can use much more power and still be eye safe/class 1 or 2, because whatever light gets to the eyes never gets focused down to a tiny spot in the retina, unlike visible lasers.

Also, sunlight is specified in intensity (power/area), and here we only have laser power, not laser spot size, so it is hard to make a fair comparison. nevertheless, sunlight is roughly ~1kW/m^2, so if the laser had a spot size of 2 mm (required to be this big for diffraction over hundreds of meters of propagation to not reduce its intensity too much) we can calculate the power of sunlight in that area: 3 mW. So the laser would be actually ~10x more intense. (if the laser would be 7.2 mm wide then the intensity would be the same as sunlight) But one is comparing totally different wavelengths, so the laser safety rules are different. Two intros to laser safety for whomever is interested: https://www.rp-photonics.com/laser_safety.html https://spie.org/Documents/Publications/00%20STEP%20Module%2...

About thermal damage - funnily enough there is lots of time in nanoseconds to transmit heat and cause thermal damage. Heat transfer is actually reasonably fast at the submicroscale. As a curiosity see https://www.semrock.com/Data/Sites/1/semrockimages/technote_... for the difference between punching a hole with a femtosecond laser (no time for thermal diffusion to happen) and a nanosecond pulsed laser. The area around the laser just completely melts in the nanosecond case. Nevertheless this was done at much higher energies per pulse than the lidar lasers (thankfully!)

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FWiW you can have 3 or even more frequencies in a laser beam coherent with each other, i.e. where te phase of the waves is locked together. This allows you to interfere the waveforms of the different lasers in time, as their relative phases are locked. This is very hard to do with continuous wave lasers, but rather routine with short pulsed lasers (e.g. femtosecond).

Actually supercontinuum lasers are not a recombination of different (incoherent) lasers but rather a 'processed' output from a single laser. You start with a high peak power laser pulse (e.g. a femtosecond mode locked oscillator) and excite a highly nonlinear process that generates new frequencies (e.g. using a special kind of optical fiber), and at the output you have a continuous broad spectrum. What happens in the fiber is actually similar to sea waves arriving on the beach - a very long and well beahaved wave steepens in the leading edge (which means new frequencies were generated) and eventually breaks/collapses into many small waves of much shorter period. The laser in this article is probably 100x or even more cheaper than a setup like this, but also does not have the full coherence supercontinuum sources have, so it will be used for different things.

A picture of the output of a fully coherent white light laser spanning from the uv to ir: http://www.laserfocusworld.com/articles/2011/09/sub-femtosec...

For more cool physics related to this read about frequency combs, which are (most of the time) frequency stabilized supercontinuum lasers.

For linux users, a very useful app: BasKet Note Pads. It's an organization tool, you write pages with notes, format text in those notes, dragndrop files into the page, and the killer feature: at any time you can capture a part of the screen and it goes directly to that page. (e.g. you can be writing notes about a PDF and capture text/a graph/an image from it, directly, in a second) I can't live without it. Out of curiosity, does anyone know similar apps? (in any OS)

link: http://basket.kde.org/

I'm in Portugal so I can't comment on your experience. In here one can get it at any 'mom&pop' hardware store, which are more common than 'Home Depot' style stores.

There is also lots of information in this page http://members.optusnet.com.au/~eseychell/PCB/etching_CuCl/i...

about an alternative to ferric cloride, acid cupric cloride. It is easier to buy, since all you are doing is mixing 2 parts oxygenated water with 1 part muriatic acid/HCl (@33%), which can be obtained at any hardware store. It shares the same problem with Ferric Cloride: after etching, the resulting solution is hazardous and should be disposed accordingly (€€/$$).

I've done this at home just like the original article but with this other solution and after 3-4 tries got pretty good results. Good enough for some basic SMD circuits.

Portugal as well, Porto

I think that it is also worth noting that there is no free, independent implementation of LabVIEW. Being dependent on a vendor is not ideal, but hey, it's life.

Anyway, there are some tasks that lend themselves much better to imperative constructs. (imho) I wish it had a scripting language embedded. LuaVIEW serves that purpose, but it is not widespread. It is not good to send people my VIs and ask them to install some 3rd party component to be able to run them.

I think you have a good point that most people prefer to use the mouse, and commands that may seem obvious for some people may not be immediate for another. A clickety pointy UI would make it's affordances more immediate for the user, and I bet that they will look into that in the future. (In the lastest version, you can call ubiquity actions with a right click on the text. That's a start)

Given that, I do find ubiquity much more user-friendly and useful than commands in the terminal, for the tasks it was designed to use. For example, you can select a whole page, just alt-space, write 'translate to chinese' and it substitutes the text in place, fast. In your email, you can select an address, write 'map' and insert it in the email almost instantly. You can save many seconds and mindshare with this tool.

I had similar ideas, but I think it is technically challenging to produce such transparent displays so close to the eye (i.e. integrated in eyeglasses, for example). The eye can't focus in objects that close.

One solution could be doing some kind of retinal projection. You could adapt the optics in real time to compensate the eye's focus, and you would have a UI stamped into your normal vision at all times. The real problem is technology because, AFAIK, such systems are currently too big to be used in our day-to-day lives. ( http://en.wikipedia.org/wiki/Virtual_retinal_display )