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dTOF (Direct time-of-flight) is a technology based on optical time-of-flight ranging, which calculates the distance of a target by emitting pulsed light and measuring its round-trip Time difference. Its core components include a vertical cavity surface emitting laser (VCSEL), a single photon avalanche diode (SPAD), and a time digitial converter (TDC), which is capable of directly recording the time of flight of optical signals and generating depth maps.
definition
Time-of-flight (TOF) is a technology that uses light Time of Flight to measure the distance of objects. TOF technology has the characteristics of high precision, long distance measurement ability and fast response.
dTOF (Direct Time-of-Flight)
It is a technique that directly calculates the distance between an object and a sensor by measuring the time difference between the transmission and reflection of a light pulse. It is closely related to and distinguished from TOF (Time-of-Flight) and iTOF (Indirect Time-of-Flight).
iTOF (Indirect Time-of-Flight) ITOF (indirect time-of-flight)
iTOF is another implementation of TOF technology, which calculates the time of flight indirectly by measuring the phase difference between the emitted modulated laser pulse and the received reflection-modulated laser pulse.
TOF is a general term that includes dTOF and iTOF (Indirect Time-of-Flight). Both use the time difference or phase difference of the optical signal to measure the distance, but the principle and hardware architecture are different.
Both are widely used in automatic driving, robot navigation, industrial automation, 3D map production and other fields.
The difference between dTOF and iTOF
1. Working principle
The way dTOF works is that the VCSEL fires a pulsed laser into the scene, the laser pulse hits the object and is reflected back to be received by the SPAD. The TDC records the time when the laser pulse is emitted and received, and by calculating the time difference and multiplying by the speed of light, the distance between the object and the sensor is obtained.
The principle of iTOF works is that the VCSEL emits a modulated laser pulse of a specific frequency, which is reflected back to the object and received by the image sensor. By calculating the phase difference between the transmitted signal and the received signal, the image sensor indirectly obtains the time of flight of the light, and then calculates the distance between the object and the sensor.
2. Advantages
The advantages of dTOF technology are:
High accuracy: Due to the direct measurement of time of flight, dTOF has high ranging accuracy and is suitable for scenarios requiring high precision measurement.
Long distance measurements: The dTOF’s long distance measurements make it suitable for applications that require long distance measurements.
Strong anti-interference ability: dTOF is relatively insensitive to the interference of ambient light, and can maintain stable measurement performance in complex environments.
3. Application scenarios
dTOF is mostly used in long-distance, high-precision scenarios such as liDAR and industrial ranging.
iTOF is commonly seen in short and medium distance interaction scenes such as AR/VR and face recognition of mobile phones and tablets.
Difference between TOF, dTOF and iTOF
TOF dTOF iTOF
The distance measurement principle uses the light time of flight to measure the distance (generally referred to) directly measure the time of flight of the light pulse and indirectly calculate the time of flight by measuring the phase difference
Core components laser, detector, timer, etc. (generally referred to) VCSEL, SPAD, TDC VCSEL, image sensor
Advantages High precision, long distance measurement, fast response (general) High precision, long distance measurement, strong anti-interference ability, low cost, high resolution
The implementation is difficult, requiring high-precision time-measuring circuits and highly sensitive light detectors
Range accuracy and range may be limited
Application Scenarios Automatic driving, robot navigation, industrial automation, etc. (in general) automatic driving, robot navigation, high-end electronics market and other consumer electronic products, smart phones, tablets, etc
To sum up, dTOF, TOF and iTOF have differences in ranging principles, core components, advantages and application scenarios. In the practical application, it is necessary to choose the appropriate technical scheme according to the specific needs.
In summary, dTOF and iTOF respectively represent two technical routes of TOF technology. The former is known for high precision and anti-interference, while the latter has more advantages in cost and resolution. In practical applications, appropriate technical solutions need to be selected according to specific needs.