It is reported that recently, TDK launched a new MEMS based ultrasonic TOF sensor ch-101. Compared with the optical TOF sensor, it can accurately measure the distance from the object, regardless of its size, color and transparency. In addition, it is not affected by ambient noise, such as harmful sound and ambient noise.

MEMS ultrasonic TOF sensor helps to improve AR / VR realism

Subminiature sensor is one thousandth of the traditional sensor

Augmented reality / virtual reality (AR / VR) systems are increasingly used in entertainment, education, medical and other industrial fields. They allow users to simulate complex tasks or surgeries in virtual space. Sensing technology enables users to obtain real experience in virtual space through complex and accurate position / motion detection. Recent AR / VR systems use time of flight (TOF) to measure the distance to objects, and ultrasonic sensors are attracting great attention.

The challenge of improving AR / VR Realism: reducing the size of ultrasonic sensor

Since various HMD AR / VR headphones began to be available at affordable prices in 2016, the global AR / VR market has increased significantly, and its scale may exceed US $11 billion by 2025. Although AR / VR systems were mainly used for entertainment applications such as games in the past, their applications in the fields of assembly, manufacturing, transportation, retail, education and medical treatment are expected to increase.

MEMS ultrasonic TOF sensor helps to improve AR / VR realism

The latest AR / VR system model allows users to simulate complex surgery in virtual space, which is made possible by HMD and manual controller with six degrees of freedom (6-DOF 1). This makes the body motion in the virtual space seamlessly integrated with the body motion in the real space, because this is a sensor based technology, which is called location tracking, and measures the distance to the object by using the TOF method, so this integration is possible.

TOF measures the distance to the object according to the time difference between the emission of light, infrared or ultrasonic and the return to the sensor after being reflected by the object. Although the optical or infrared time of flight (TOF) has high accuracy, it can not be used for measurement when there are obstacles, nor is it suitable for measuring the distance to glass or other transparent objects. Ultrasonic time of flight (TOF) can accurately measure the distance to an object. Even if it is highly reflective, it is not affected by lighting conditions, object size or color. However, the traditional ultrasonic TOF sensor needs complex signal processing, and its volume is too large to be embedded in household appliances.

TOF solution based on subminiature MEMS sensor

TDK’s solution to this challenge is ch-101, a new ultra small ultrasonic TOF sensor, whose volume is one thousandth of that of the traditional ultrasonic TOF sensor. The world’s first MEMS based ultrasonic sensor provided by chirp brand is a real breakthrough product. It integrates piezoelectric micromechanical ultrasonic sensor (pmut3), power efficient digital signal processor (digital signal processor 4) and low-power CMOS asic5 in a small package of 3.5 x 3.5 x 1.25 mm.

Existing VR systems based on optical sensors combine external sensors to send infrared, in which wired headphones and controllers respond to infrared to locate the user’s position. Using the virtual reality system of ch-101, users can experience virtual reality with only one headset and one controller.

Bats can fly freely in the dark without hitting objects, because they can detect the position and relative velocity of objects by sending out pulsed ultrasound and receiving the echo generated by objects. This is called echolocation. The same principle is also used for the positioning and tracking of ultrasonic sensors.

The ch-101 has an embedded pmut that emits ultrasonic pulses and receives echoes from objects in the field of view of the sensor. When combined with various signal processing, it can be used in a wide range of applications, including detecting the distance and position of objects, sensing the existence of objects and avoiding collisions. In addition, it requires low power consumption, 100 times lower than the traditional ultrasonic sensor, so as to provide superior environmental performance.

Although the maximum sensing range supported by the ch-101 ultrasonic sensor is 100 cm, the maximum range of the new product ch-201 can reach 500 cm, and mass production is planned to start at the end of 2019. Due to the use of MEMS technology, the sensor has become smaller than ever before. We can expect a wide range of applications, including AR / VR headphones, smart homes, UAVs, robots, smart phones and wearable devices.

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