How Lasers Actually Work

Lasers are optical amplifiers, optical oscillators, and in a way, the most sophisticated light source ever invented. Not only are lasers extremely useful, but they are also champions of magnitude: While different laser types cover the electromagnetic spectrum from radiation (<10 nm) over the visible spectrum to far infrared light (699 μm), their individual output band can be as narrow as a few µHz. Their high temporal and spatial coherence lets them cover hundreds of meters in a tight beam of lowest divergence as a perfectly sinusoidal, electromagnetic wave. Some lasers reach peak power outputs of several exawatts, while their beams can be focused down to the smallest spot sizes in the hundreds and even tens of nanometers. Laser is the acronym for Light Amplification by Stimulated Emission Of Radiation, which suggests that it makes use of a phenomenon called stimulated emission, but well, how exactly do they do that? It’s time to look the laser in the eye (Disclaimer: don’t!).

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Mouse Brains Plus Line Laser Equals Rangefinder

[Neumi] wrote in with a sweet robotics hack. It’s a 2D laser distance sensor (YouTube) made with a cheap line laser and an optical mouse’s flow-sensor chip used as a low-resolution camera. In one sense, it’s a standard laser-distance-sensor project. But it is clever for a whole bunch of reasons.

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For one, using a mouse sensor as a low-res camera is awesome. It’s designed to read from a standard red LED, so the sensitivity is in just the right ballpark for use with a line laser. It returns a 30×30 pixel greyscale image, which is just about the right amount of data for a low-end microcontroller to handle and keep up with the framerate without resorting to coding tricks.

It’s also no coincidence that these sensors are available with lenses built in, for relatively cheap, on eBay. Apparently the quadcopter gurus use them as if they were mice to visually track their quad’s motion. Hacker spillover!

Detecting the laser line as it reflects off of whatever objects are lying on [Neumi]’s floor could also possibly prove difficult, and might produce false readings in the presence of background illumination. So [Neumi] takes two readings with the camera — one with the laser on and one with it off — and differences them. Done fast enough, this should reduce any non-laser sources down to the sensor’s noise floor. Finally, there’s some thresholding and averaging going on behind the scenes that help make everything work out right. The code is up on GitHub.

Not a bad build for a 2D laser distance system on a budget. If you want to shell out a bit more money, and are into a seriously involved build, this is probably the slickest we’ve seen in a long time. And if you’re thinking that you’ve heard of [Neumi] before, you’re right: we featured this 405mm laser PCB exposer / burner CNC machine just a few months ago.

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Low Cost Optics Bench Project – Now with Lasercut Optics

[PWalsh] has a clever idea for learning and experimenting with basic optics: instead of using actual lenses, he’s using clear pieces of laser-cut acrylic cut into lens profiles instead. They are much easier to make, mount, adjust, and handle while still bending light in the same basic ways. It allows for simple hands-on experimentation with plenty of visual feedback – perfect for beginners.

Optical Group

This idea is part of [PWalsh]’s low-cost optics bench project, which uses laser-cut plastic to create adjustable optics bench components. We’ve covered this project before, but [PWalsh] expanded the idea with the concept of these simple laser-cut optics for basic experimentation; an addition that requires no additional tools and only a small amount of material. Features and value added for nearly zero cost is something we always love to see!

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How to Fail at Laser Cutting

Laser cutters are CNC power tools, which means an operator uploads a job digitally and then pushes START to let the machine do all the work while they lie back in a hammock sipping a margarita, occasionally leaping out in a panic because the sound coming from the machine changed slightly.

Like other power tools, laser cutters are built around doing one thing very well, but they require an operator’s full attention and support. The operator needs to handle all the other things that are go on before, during, and after the job. It’s not too hard to get adequate results, but to get truly professional and repeatable ones takes work and experience and an attention to detail.

People often focus on success stories, but learning from failures is much more educational. In the spirit of exploring that idea, here are my favorite ways to fail at laser cutting and engraving. Not all of these are my own personal experience, but they are all someone’s personal experience.

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What Came First? The Chicken or the LASER?

If you’ve had a child in the last few decades, you’ve had a choice to make: if you want to know the sex of the baby ahead of time. With ultrasound you can find out or–popular these days–you can have the result sealed and have a baker create a reveal cake. Apparently, researchers at the Dresden University of Technology and the University of Leipzig wanted to do the same trick with unborn chickens.

You might wonder why anyone cares (we did). Apparently, chickens that are bred for egg laying don’t produce roosters suitable for food use. This leads to about half of the chicks being “culled” (a less ugly euphemism than gassed or shredded) and used in–among other things–animal feed. Worldwide, billions of chicks are culled each year and that’s not counting other similar situations like male turkeys and female ducks.

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Curiously Delightful Things Done with Lasers and Projectors

Seb Lee-Delisle has built a career around large installations that use powerful lasers and high-end projects to make people happy. It’s a dream job that came to fruition through his multi-discipline skill set, his charismatic energy, and a mindset that drives him to see how he can push the boundaries of what is possible through live interaction.

His talk at the Hackaday | Belgrade conference is about his Laser Light Synth project, but we’re glad he also takes a detour into some of the other installations he’s built. The synth itself involves some very interesting iterative design to end up with a capacitive touch audio keyboard that is lit with addressable LEDs. It controls a laser that projects shapes and images to go along with the music, which sounds great no matter who is at the keyboard thanks to some very creative coding. As the talk unfolds we also hear about his PixelPyros which is essentially a crowd-controlled laser fireworks show.

See his talk below and join us after the break for a few extra details.

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UV Photographic Printer Lets You Use Strange Chemistries

There is a family of old photographic chemistries based on iron compounds which, like the blueprint, are exposed using UV light. Ironically, the digital camera revolution which has made everything else in our photographic lives much easier, has made it harder to experiment around with these alternative methods. [David Brown] is making a UV photographic printer to change that.

[David]’s application has a lot in common with PCB printers that use a UV-sensitive resist, only [David] needs greyscale, and it might also be nice if it could work with wet paper. This makes it a more challenging project than you might think, but we like the cut of [David]’s jib.

Like some of the other UV exposer projects, [David]’s uses a rotating mirror to scan across the to-be photograph’s surface. Unlike the other ones that we’ve seen, the exposer hangs from two linear rails. Other printers move the paper underneath a stationary scanning head, which seems a mechanically simpler arrangement. We’re excited to see how this goes.

There’s a lot of interest in UV PCB printers right now. We’ve seen one made from junked CD-ROM drives on one end of the spectrum to one made by retrofitting a delta robot on the other. And don’t disregard the work done by folks interested in UV-curing 3D printers, either.