Sony FCB camera block
1. Basic principles of dTOF
dTOF (Direct time-of-flight) is a technique that calculates the distance to a target by emitting pulsed light and measuring its round-trip Time difference. The core principle is to use the constant speed of light to calculate the distance between the target object and the sensor by accurately measuring the time of the light pulse from transmission to return. The specific formula is:
Distance = speed of light x time of flight / 2
The key to dTOF technology is the ability to measure the time of flight of photons directly, rather than through phase differences or other indirect methods.
2. Core components of dTOF
dTOF technology consists of the following core components:
2.1 Transmitting end
VCSEL (Vertical cavity Surface emitting Laser) : VCSEL is a commonly used emission light source in dTOF systems, which has the characteristics of high efficiency, compact, low power consumption and fast modulation. It can emit pulsed light with high energy density, which is suitable for short-distance and high-precision ranging.
Optical components: Includes a collimating lens and a diffracted optical element (DOE) for collimating and distributing the laser beam to the target area.
2.2 Receiving End
SPAD (Single photon Avalanche Diode) : The SPAD is the core receiving sensor of the dTOF system, capable of generating a response to a single photon and triggering an avalanche effect to output a current signal. The high sensitivity of SPAD enables it to operate in low light environments and provides high precision time measurement.
SiPM (Silicon photonic Photomultiplier tube) : In some applications, SiPM is also used as a receiving sensor, which contains multiple SPAD pixels inside, capable of providing higher signal strength.
2.3 Time Digital Converter (TDC)
TDC is a circuit that converts the time of flight of a light pulse into a digital signal. It records the time interval between the transmitted pulse and the received pulse, and generates a time distribution histogram through time-dependent single photon counting (TCSPC) technology to determine the target distance.
2.4 Narrow-band filter
To reduce interference from ambient light, dTOF systems are typically equipped with narrowband filters that allow only specific wavelengths of light, such as 940nm, to pass through, thereby improving the signal-to-noise ratio.
2.5 Laser drive circuit
The laser drive circuit is responsible for controlling the emission of the VCSEL, providing high-power pulse signals to ensure the intensity and stability of the emitted light.
3. Advantages of dTOF
High precision ranging: By directly measuring photon time of flight, dTOF is able to achieve high precision distance measurement.
Low power consumption: The efficient nature of VCSEL and SPAD allows dTOF systems to operate at low power consumption.
Strong anti-interference ability: narrow band filter and high sensitivity of SPAD make it perform well in complex environments.
Because of its high precision and low power consumption, dTOF technology is widely used in consumer electronics, 3D imaging, automatic driving, robot navigation, drone navigation and other fields.
In the field of 3D imaging, dToF technology can capture high-precision depth images, providing strong support for object recognition and scene reconstruction. In the field of autonomous driving, dToF technology can realize high-precision distance measurement and obstacle detection, which provides an important guarantee for the safe driving of vehicles.