Teardown of Intel RealSense Gesture Camera Reveals Projector Details

[Chipworks] has just released the details on their latest teardown on an Intel RealSense gesture camera that was built into a Lenovo laptop. Teardowns are always interesting (and we suspect that [Chipworks] can’t eat breakfast without tearing it down), but this one reveals some fascinating details on how you build a projector into a module that fits into a laptop bezel. While most structured light projectors use a single, static pattern projected through a mask, this one uses a real projection mechanism to send different patterns that help the device detect gestures faster, all in a mechanism that is thinner than a poker chip.

mechanism1It does this by using an impressive miniaturized projector made of three tiny components: an IR laser, a line lens and a resonant micromirror. The line lens takes the point of light from the IR laser and turns it into a flat horizontal line. This is then bounced off the resonant micromirror, which is twisted by an electrical signal. This micromirror is moved by a torsional drive system, where an electrostatic signal twists the mirror, which is manufactured in a single piece. The system is described in more detail in this PDF of a presentation by the makers, ST Micro. This combination of lens and rapidly moving mirrors creates a pattern of light that is projected, and the reflection is detected by the IR camera on the other side of the module, which is used to create a 3D model that can be used to detect gestures, faces, and other objects. It’s a neat insight into how you can miniaturize things by approaching them in a different way.

Shedding Light on the Mechanics of Film Projection

Do you know how a film projector works? We thought we did, but [Bill Hammack] made us think twice. We have covered the Engineer Guy’s  incredibly informative videos many times in the past, and for good reason. He not only has a knack for clear explanation, the dulcet tones of his delivery are hypnotically soothing. In [Bill]’s latest video, he tears down a 1979 Bell & Howell 16mm projector to probe its inner workings.

Movies operate on the persistence of vision (POV) principle, which basically states that the human brain creates the illusion of motion from still images. If you’ve ever drawn circles and figure eights in the nighttime air with a sparkler or perused a flip book, then you’ve experimented with POV.

A film projector is no different in theory. Still images on a strip of celluloid are passed between a lamp and a lens, which project the images on to a screen. A device called a shuttle advances the film by engaging its teeth into the holes on the edge of the film and moving downward, pulling the film with it. The shuttle then disengages its teeth and moves up and forward, starting the process again.

shuttersFilm is projected at a rate of 24 frames per second, which is sufficient to create the POV illusion. A projector’s shutter inserts itself between the lamp and the lens, blocking the light to prevent projection of the film’s physical movement. But these short periods of darkness, or flicker, present a problem. Originally, shutters were made in the shape of a semi-circle, so they block the light half of the time. Someone figured out that increasing the flicker rate to 60-70 times per second would have the effect of constant brightness. And so the modern shutter has three blades: one blocks projection of the film’s movement, and the other two simply increase flicker.

[Bill] explains how the projector reads the optical soundtrack. He also delves into the mechanisms that allow continuous sound playback alongside intermittent projection of the image frames. You’ll never look at a projector the same way again.

Want to know more about optical soundtracks? Check out this Retrotechtacular that explores the subject in detail.

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Police LiDAR Tear Down

Most police departments made a big switch from RADAR to LiDAR after consumers starting buying RADAR detectors. A lot of those LiDAR units are now out there on the surplus market. If you don’t have $500 or so to buy a LiDAR gun just to see what makes it tick, you are in luck. [Alexei Polkhanov] spent an hour tearing down a  UltraLyte LTI 20-20 LR 100 so you don’t have to.

An hour seems like a lot for a tear down video, but [Alexei] speeds up through the boring parts, and spends a lot of time talking about the optics and how the device works (with a lot of hand drawn diagrams). He also puts it back together and connects  a scope to show the electronic operation of the device.

He mentions the display and control board uses a serial interface to talk to the controller board. There is also an unpopulated header on the main board that is clearly a serial port, probably for reprogramming the onboard microcontroller. With a little reverse engineering work, this LiDAR gun ought to be highly hackable.

In addition to the display and control board, the unit contains a high voltage supply for the laser and the photodiode. Making a power supply to drive the laser that is clean enough not to disturb the sensor is one of the design drivers and it shows. The power supply is a large and complex board by comparison to the other boards in the system.

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Muse EEG Headset Teardown

[Lady Ada] over at Adafruit just did a delightful tear down of the Muse EEG headset.

The Muse headset is a rather expensive consumer-grade EEG headset that promises better meditation with the ability to track your brainwaves in order to go into a deeper trance. We’re not much for meditating here at Hackaday, but the EEG sensors really do work. It’s pretty cool to see the insides of this without forking out $300 ourselves for one we might break.

Like most EEG headsets, they weren’t really designed to be worn while sleeping. Two bulky pods over the ears hold the battery and charging circuit on one side, and the brains on the other. The neat part about it is a little adjustable metal piece which allows for adjustment on the strap while maintaining all the electrical connections. A flexible circuit houses forehead electrodes which go along the length of the band.

In the past we’ve seen work done on the Lucid Scribe project, using a modified Neurosky Mindwave EEG (at $99 it’s much cheaper to hack). The idea is to be able to monitor your sleep cycles accordingly, and then give audible cues to the dreamer in order to “wake up” inside the dream. Think of the Inception music.

Unfortunately it doesn’t look like the Muse will be any better for lucid dreaming. If you were able to decouple the electrodes from the rest of the headset,  then it might just work.

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Tearing Down The Apple Watch

The Apple Watch has been out for nearly a month now, but so far we haven’t seen a good look at the guts of this little metal bauble of electronic jewelry. Lucky for us that a company in China is hard at work poking around inside the Apple Watch and putting up a few incredible SEM images along the way (Google Translatrix).

This isn’t the first Apple Watch teardown that’s hit the intertubes – iFixit tore one apart with spudgers and tiny screwdrivers and found someone skilled in the ways of tiny parts could probably replace the battery in this watch. Shocking for an Apple product, really. iFixit also took a look at the watch with an x-ray, revealing a little bit of the high-level design of the Apple Watch, the Apple S1 computer on a chip, and how all the sensors inside this wearable work.

A side view of a 6-DOF IMU
A side view of a 6-DOF IMU

This teardown uses an incredible amount of very high-tech equipment to peer inside the Apple Watch. Because of this, it’s probably one of the best examples of showing how these tiny sensors actually work. With some very cool images, a 6-DOF IMU is revealed and the Knowles MEMS microphone is shown to be a relatively simple, if very small part.

Now the Apple S1, the tiny 26.15mm x 28.50mm computer on a chip, serves as the brains of the Apple Watch. It’s breathtakingly thin, only 1.16mm, but still handles all the processing in the device.

Even if you won’t be buying this electronic accessory, you’ve got to respect the amazing amount of engineering that went into this tiny metal bauble of semiconductors and sensors.

Teardown: An Electronic Master Lock

[rohare] has an interesting teardown for us over on the keypicking lock picking forums. It’s a Masterlock combination lock – specifically the Masterlock 1500eXD – and yes, it’s a completely electronic lock with buttons and LEDs. Think that’s the mark of a terrible lock? You might be surprised.

The first impressions of this lock were surprisingly positive. It was heavy, the shackle doesn’t move at all when you pull on it. Even the buttons and LEDs made sense. Once the back of the lock was drilled open, things got even more impressive. This lock might actually be well-built, with a ‘butterfly’ mechanism resembling a legendary padlock, actuated by a small but sufficient motor. Even the electronics are well-designed, with the programming port blocked by the shackle when it’s closed. [rohare] suspects the electronics aren’t made by Masterlock, but they are installed in a very secure enclosure.

The teardown concludes with a fair assessment that could also be interpreted as a challenge: [rohare] couldn’t find any obvious flaws to be exploited, or a simple way to break the lock. He concludes the most probable way of breaking this lock would be, “knowing some trick of logic that bypasses the codes on the electronics”. That sounds like a good enough challenge for us, and we’re eagerly awaiting the first person to digitally unlock this physical lock.

Digital Light Processing, So Many Tiny Mirrors

Did you know there are a million little mirrors flickering back and forth, reflecting light within some modern projectors; like a flip-dot display but at the micro level? In his video, [Ben Krasnow] explains the tiny magic at work in DLP, or digital light processing technology with a scaled up model he constructed of the moving parts.

LCD projectors work much like old slide projectors. Light is shined through a transparent screen containing the image, which is then focused and enlarged through a lens. DLP projectors however achieve the moving image in a slightly different way. A beam of focused light is shined onto a chip equipped with an array of astonishingly small mirrors. When the mirror is flipped in one direction, it reflects the light out through the lens and creates a visible pixel. When the mirror is tilted the opposite direction, no light is reflected and the pixel is dark. All of these tiny moving parts are actuated by means of static electricity, and since a pixel can effectively only either be in an on or off state without any range of value in-between, the pixel must flutter at a rate fast enough to achieve the illusion of intensity, much like pulsing an LED to create a dimming effect.

In addition to slicing open the protective casing of one of these tiny micro-mirrored chips to give us a look at their physical surface under a microscope, [Ben] also built his own functioning matrix from tiles of mirrors and metal washers sandwiched around pieces of string. A wound electromagnet positioned behind each tile tilts the pixel into position when a current is run through the wire — although he didn’t sink the time needed to build out the full array in this manner (and we don’t blame him). If you do have the time and add in a high powered flash-light, this makes for an awesome way to shine messages on your roommate’s wall.

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