Powerful & Accurate ToF Sensors Optimised For Complex Imaging Applications

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STMicroelectronics offers a wide range of Time-of-Flight sensors with its FlightSense solution meeting various requirements of ranging and detection for unlimited markets and applications.

The company recently held an online media session where ST’s perspectives and future goals were shared by Jerry Chang, Technical Marketing Manager, Imaging Division, Greater China & South Asia and Vincent Lin, Technical Marketing Manager, Imaging Division, Greater China & South Asia. The session was attended by EFY.


FlightSense or Time-of-Flight by STMicroelectronics is based on the module emitter, which is a laser emitter that transmits light or photons, bounces back after colliding with the target and is received by the receiver.

The principle is quite straightforward. The technology is based on the speed of light multiplied by the time of travel of the photon upon 2. And then you will get the distance. It is a very important and fundamental design guideline that is used for measuring distance. What you get is the exact/accurate distance, independent from colours, sizes or reflectance of the objects. When you range objects that are black, white or other colours, you get the same ranging accuracy. It is fast and low power. You may want to know how to use the very specific 940nm illumination (8’50) light source.

The SoC sensor acts as the receiver. A processor and an emitter are also present. They are all combined into one single module.

To ensure safety, the product meets class 1 safety levels. Class 1 represents that human beings can look at the laser straight with bare eyes. So it is the strictest standard available in the industry.

“It is very important for our products with VCSEL. We want to go to applications that are close to you and me, and our friends and families. So safety is another important element we care about,” said Jerry Chang, Technical Marketing Manager, Imaging Division, Greater China & South Asia.

Key Features

High Performance Distance Measurement: Provides accurate distance ranging and measurement.
Easy and Quick Integration: Small footprint and can be hidden behind black cover glass.
Low Power Consumption: Can be integrated into battery-powered devices.
Extra-long distance measurement
Multi-Target Detection
Dynamic Smudge Correction

Main Applications

⦁ Obstacle detection
⦁ Content analysis
⦁ Gesture control
⦁ Light control
⦁ Load management
⦁ Occupancy detection
⦁ Power saving
⦁ SLAM
⦁ Volume control

…and many more.

Product Portfolio

ST has a range of products with different ranging distances, which enables large target detection areas.

“FoV or field of view represents the target you are aiming at when talking about ranging. The area of coverage actually expands as distance increases. For instance, VL6180V1 has 60 centimetres ranging and a 29 centimetres diagonal. For VL53L1CB, you will see a much larger coverage, which is 384 centimetres. The design is to help our customers to apply different applications and ranging targets for particular purposes,” explained Jerry Chang.

Some notable products are:

  1. VL53L3CX: It is a high-performance proximity sensor that combines short-distance linearity and ranging.

Highlights

⦁ FoV ranging (max.): 500 centimetres (5 metres) and 25 degrees single zone.
⦁ Excellent short-distance linearity
⦁ Immune to cover glass cross-talk beyond 80 cm.
⦁ Automatic fingerprint smudge compensation

Applications

⦁ AR/VR
⦁ Tablets
⦁ Service robots
⦁ Industrial

2. VL53L1CB: It is a ToF sensor with a lens for long-distance ranging and FoV programming.

Highlights

⦁ FoV ranging (max.): 800 centimetres (8 metres) and less than/equal to 27 degrees single or multi-zone.
⦁ Integrated lens for long-distance ranging
⦁ Better ambient light immunity
⦁ Immunity to cover glass cross-talk beyond 80 cm.
⦁ SPAD array zone selection for FoV reduction
⦁ Automatic fingerprint smudge compensation

Applications

⦁ Laptop
⦁ Vacuum Cleaners
⦁ Service Robots
⦁ Logistics

3. VL53L5CX: It is a brand new ToF sensor for medium to long-distance ranging, with multi-target measurement and FoV programming. There are all new elements and new formats in hardware, software and optical design for it.

Highlights

⦁ FoV ranging (max): 61 degrees of all 64 zones at 15fps or 16 zones at 60fps.
⦁ Transfers ranging data to the system host over an I2C or an SPI bus.
⦁ Multi-object detection
⦁ Immunity to cover glass crosstalk beyond 80 centimetres.
⦁ Automatic fingerprint smudge compensation

Applications

⦁ Laser autofocus
⦁ Presence detection
⦁ Gesture detection

….and more imaging applications.

“As for the power consumption of VL53L5CX versus VL53L1CX, VL53L5CX is a much more complicated device for more sophisticated use cases. So when we try to deliver the gesture application, we require very frequent ranging and very accurate reading, so it may consume more power. But if you are doing a very basic simple one reading system on and off detection targeted basic application, it doesn’t consume a lot of power. So it will depend on use cases and how the designer uses the part,” said Vincent Lin, Technical Marketing Manager, Imaging Division, Greater China & South Asia.

Consumer Applications

These low-power and small-footprint devices enable best user experiences with core benefits including immunity to colour and texture, volume control, ability to work with many optical cover materials and high-IP integration.

Typical applications are:
⦁ Home appliances (lighting, mirrors, locks)
⦁ Sanitary systems (faucets, dispensers, bins)
⦁ Educational (tablets, smart glasses)
⦁ Medical
⦁ Parking
⦁ Farming
⦁ Wearables & IoT

FlightSense also focuses on providing high-accuracy and high-speed with respect to projectors – be it for large, mini or portable projectors, for an enhanced user experience.

Core benefits include:
⦁ High-speed distance detection for fast image adjustment.
⦁ High-speed light dimming that ensures user eye safety.
⦁ Multi-points detection enables automatic keystone correction.
⦁ Battery operated, high-performance down to 175μW at 1Hz.

Another mentionable focus of FightSense is on cleaning and servicing robots that offer home assistance, vacuum cleaning and air-purifying.

Core benefits include:
⦁ Low-power
⦁ Obstacle avoidance
⦁ Wall tracking
⦁ Cliff/ceiling detection
⦁ Touchless operation

Industrial Applications

The flexible, multi-usage sensors are suitable for highly-efficient factory automation and content management. These can be achieved through the implementation of FlightSense technology in conveyor belts, rolling machines, bar-code readers, trucks & containers, recycling tanks/trash bins and warehouses.

Core benefits include:
⦁ Long-distance ranging
⦁ Multi-object detection
⦁ Fast-ranging mode of 100Hz (which means 100 ranging per second)
⦁ Low-power
⦁ Volume monitoring and measurement
⦁ Occupancy detection for parking management

COVID-19 Use Cases

In the past few months, COVID-19 has drastically changed our lives. Since the transmission spreads due to contact, people have become apprehensive regarding touch, especially buttons.

Fortunately, several features of the ToF sensor offer a viable solution to this problem such as:
⦁ Distance Ranging – It helps in maintaining social distance and accurate temperature reading from a certain distance.
⦁ Presence detection – For counting the number of people on the premises
⦁ Touchless Interface – No fear of contact while operating a device/machine
⦁ Content management – For maintaining sanitizer liquid levels and monitor any empty stock

Similarities With CIS & LiDAR

Contact Image Sensor (CIS) and ToF are two different product areas. But in many cases, they (CIS + ToF) are often used together such as in notebooks, smart locks and mobile phone cameras.

Likewise, ToF and Light Detection And Ranging (LIDAR) are basically two different solutions. From the application perspective, there may be some overlap there but when talking about long-distance and outdoor motorcycling, this is the area that the ST ToF is not particularly addressing today. So, the sensor is optimal for consumer and industrial rather than automotive.

Ecosystem & Tools

ST’s several imaging products are supported by these tools & others in the company’s optical partnership network.

FlightSense is fully integrated into the STM32 ecosystem, which comprises SM32 NUCLEO boards such as NUCLEO-F401RE and NUCLEO-L476RG. The cover glasses are important too and are available as oval cover glass or square cover glass. These expansion boards also come with breakout-boards that enable easy and easy integration to users. The expansion boards can accept breakout boards via connectors or fly wires.

These breakout boards accept 5V to 2.8V. As the name states, these boards can be separated into two parts, with the smaller part referred to as mini-PCB.

Marketing Expectations

With respect to the ToF FlightSense, ST has worked upon 4 generations of products and work continues with more than 50 OEMs. Having a huge range of development kits, more than 1 billion units were shipped for ToF last year. This number keeps on increasing with more competitive products and services serving more market segments.

“From ST’s perspective, we see that the market for ToF applications continues to grow fast. All our typical part numbers have specific applications and business perspectives. They are all popular. Since the demand for no-touch buttons will not go away as time goes on, more and more demand will come. It could be from elevators, hospitals and smart homes. So the trend for growth is tremendous. Longer ranging and multiple zones also open up new possibilities for new applications,” said Vincent Lin.

Concerning India, ST’s image sensor/ToF sensor presence has been somewhat limited. To overcome that in the coming years, the company’s strategy is to utilise its channel partners and build strong partnerships with distributors in India. This will require technical capability in doing the design and rendering support to understand how well the hardware, software and optical are today.

ST’s future roadmap includes developing 3D ToF, which is under development. L5 is the beginning of the company’s 3D sensor offering and a marketplace for it will be available soon.

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