What are the applications of MEMS ultrasonic sensors?

Augmented reality/virtual reality (AR/VR) systems are becoming increasingly widely used in various fields, such as entertainment, education, healthcare and other industrial applications. With these technologies, users can simulate complex tasks or surgical procedures in a virtual space. Sensing technology allows users to obtain a realistic experience in a virtual space through advanced and precise positioning/motion detection. The latest AR/VR systems use time of flight (ToF) technology to measure the distance to an object, and ultrasonic sensors have attracted a lot of attention.

The challenge of making AR/VR more realistic: reducing the size of ultrasonic sensors

As various head-mounted display (HMD) AR/VR headsets began to be available at affordable prices in 2016, the global AR/VR market has grown substantially, and by 2025, the size of the market is likely to exceed $11 billion (source: "2017 Future Prospects of AR/VR Related Markets", Fuji Camry General Research). AR/VR systems used to be mainly used in entertainment applications such as games, but their use in other fields is expected to increase, such as in assembly, manufacturing, transportation, retail, education, and healthcare.

Using the latest model of AR/VR system, users can simulate complex surgical operations in a virtual space. A head-mounted display and hand controller with six degrees of freedom (6-DoF1) make this application possible. In this way, a seamless synthesis between the human movement in the virtual space and the human movement in the real space can be realized. This is thanks to a sensor-based technology called Position Tracking 2, which can use the ToF method to measure the distance to an object.

ToF technology measures the distance to an object based on the time difference between light, infrared or ultrasonic wave from emission to reflection by the object and back to the sensor. Whether it is optical or infrared ToF technology, although they are very accurate, they cannot be used for measurement in the presence of obstacles, nor are they suitable for measuring the distance to glass or other transparent objects. Ultrasonic ToF technology can accurately measure the distance to objects, even if these objects are highly reflective, and this technology will not be affected by the lighting conditions, size and color of the objects. Traditional ultrasonic ToF sensors require complex signal processing and are too large to be embedded in household appliances.

ToF solution using ultra-small MEMS-based sensors

TDK's solution to this challenge is CH-101, which is a new ultra-small ultrasonic ToF sensor whose volume is only one thousandth of the traditional ultrasonic ToF sensor. As the world’s first MEMS-based ultrasonic sensor, CH-101 is sold under the Chirp brand. It is a truly breakthrough product that combines piezoelectric micromachined ultrasonic transducer (PMUT3), high-efficiency DSP (digital signal processing) 4) and low-power CMOS ASIC5 are combined together in a small package with a size of only 3.5 x 3.5 x 1.25 mm.

CH-101 combines PMUT, high-efficiency DSP (digital signal processor), and low-power CMOS ASIC. It uses a small package with a size of only 3.5 x 3.5 x 1.25 mm, and its volume is only one thousandth of a traditional ultrasonic ToF sensor one.

Bats can fly freely in the dark without crashing into objects because they detect the position and relative speed of objects by emitting pulsed ultrasonic waves and receiving echoes from objects. This method is called echolocation, and the same principle is also used for position tracking of ultrasonic sensors.

CH-101 has an embedded PMUT, which can emit ultrasonic pulses and receive echoes from objects within the sensor's field of view. Combined with a variety of different signal processing, the product can be used in a variety of applications, including detecting the distance and location of objects, sensing the presence of objects and avoiding collisions. In addition, it requires very low power consumption, one hundred times lower than the power consumption of traditional ultrasonic sensors, thus providing excellent environmental performance.

The existing optical sensor-based VR system combines an external sensor with a wired headset and a controller. The former emits infrared rays and the latter can respond to infrared rays to locate the user's location. The VR system using CH-101 allows users to experience VR only by using headsets and controllers. The CH-101 ultrasonic sensor can be used in the independent headset Vive Focus Plus all-in-one machine developed by HTC.

The CH-101 ultrasonic sensor supports a maximum sensing range of 100 cm, while the new product CH-201, which will be mass-produced at the end of 2019, supports a maximum sensing range of 500 cm. Due to the use of MEMS technology, the size of sensors has become unprecedentedly compact, and we expect them to achieve a range of applications, including AR/VR headsets, smart homes, drones, robots, smart phones, and wearable devices.

CH-101 is an ultrasonic ToF sensor based on MEMS. Unlike an optical ToF sensor, it can accurately measure the distance to an object, regardless of the size, color, and transparency of the object. In addition, it will not be affected by environmental noise, such as noise and noise in the surrounding environment.

If you want to know more, our website has product specifications MEMS ultrasonic sensors, you can go to ALLICDATA ELECTRONICS LIMITED to get more information