Hardly any competition for Chirp’s ultrasonic ToF sensor chips
Both chips share a common 3.5×3.5mm package and the same ASIC for signal processing, but the piezoelectric micro-machined ultrasonic transducers (PMUT), the MEMS parts of the sensors are built differently, tuned for the different ranges, learned eeNews Europe.
“In fact, we have been sampling the CH101 for two years now and we realized we had never made a product announcement for it”, told us David Horsley, Chirp Microsystems’ CTO. “Chirp Microsystems was founded in 2013, the CH-101 is a 2nd generation design while the CH-201 is our third generation design. Our 4th generation of chips is being tested today, and with each design so far, we’ve improved our transmitter and receiver performance by 4X”, Horsley told eeNews Europe during an interview.
The ASIC drives the MEMS array of silicon membranes to emit ultrasonic waves, which bounce off obstacles in their path and are detected back by the same membranes running in a microphone mode. The time interval (time-of-flight) between signal output and detection is what can be converted into a 2D depth map across a 180º field-of-view. According to Chirp Microsystems, the chips are the first commercially available MEMS-based ultrasonic ToF sensors and beat all other ToF solutions on small size and low power consumption.
The “Sonars on a chip” as Horsley describe them draw 100x less power and are a thousand times smaller than the best ultrasonic range finders used in today’s automotive applications. They are not only small enough and low power enough to be implemented in smartphones and other wearable electronic applications, unlike infrared-based optical ToF sensor they do not require a direct optical paths, allowing engineers to design bezel-free smartphones with accurate gesture sensing.
But that’s not all what there is on the company’s roadmap.
“On our roadmap, there is certainly a lot more we can do, for example achieving a longer range, we also have some requests for packaging transceivers with a higher sound pressure together with additional protections. We’ll work on different package variants. Those chips could be thinner, we could make them with top and bottom sound ports”, added Horsley.
“We are pioneers in this area, and we are not close to the optimum yet, we still have a lot of design space to improve the specs. We don’t feel like we have reached the devices’ physical limitations, we are not at those limits yet and we don’t have to make the devices bigger like it would be the case for mature MEMS microphones or accelerometers seeking better performance”.
What about leveraging beam forming to increase resolution in particular areas of interest or to create 3D depth maps? We asked.
“Way back in history, we made monolithic linear arrays that had ten transducers in a row. You could do beam forming and identify both range and position, but we didn’t commercialize it. We didn’t want to bite too much at a time, we decided to focus on solving manufacturing and packaging issues first” revealed the CTO.
“Currently we orient customers to use the CH-101 or CH-201 and synchronize these parts. We have customers using multiple chips together and they can use a hardware trigger. Our chips include an interrupt pin and a GIO pin. In a hardware trigger mode, you can use that pin to connect several transducers on the same I2C bus so they operate in a coordinated fashion. For Virtual Reality applications, multiple pulses from different chips can be triangulated to detect the user’s hand in 3D space”, explained Horsley.
With these product announcements, the startup has yet to break even financially: it is close to announcing a financing round, hinted the CEO. Horsley expects mass production to start early 2018 for the CH-101, the CH-201 should follow in the second half of 2018.
“We’ll see customers who currently use conventional ultrasonic sensors for monitoring drone height from the ground, move to our lighter and more power efficient solution. Customers in robotics who are currently using IR ToF sensors despite their limitations, are evaluating our parts.
Unlike IR sensors which do not work in direct sunlight, the ultrasonic ToF sensors can detect objects of any color, they can detect glass or optically transparent sliding doors, which you can’t see with IR, likes to point out the CTO.
Chirp Microsystems’ ToF sensor, for volume control.
Another promising field of application is virtual reality. “In VR, people don’t have a good solution, they use computer vision to track the game controller, which requires too much power. One of our partners will introduce a VR product in January”, Horsley said.
“What’s really nice is that our solution is extremely low power. In some applications you could be sensing distance at just 8µA when operating at one sample per second, then you could change the sampling rate upon detection of a person and still draw less than 0.5mW. In comparison, an optical IR ToF sensor draws tens of milliwatts”.
The chips provide precise, low-latency range measurements at sample rates up to 100 samples per second with position noise below 1mm. They are currently sampling to qualified customers.
Chirp Microsystems – www.chirpmicro.com
Related article:
Chirp launches ultrasonic ToF sensors
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