ToF camera has five core hardware units, including infrared emission unit, optical lens, imaging sensor, control unit and core algorithm calculation unit.
The infrared emission unit includes Vcsel transmitter and Diffuser. Vcsel emits a pulsed square wave with a wavelength of 940nm. infrared light of this wavelength is invisible light, and at the same time, the amount in the light spectrum is the least, which can avoid the interference of ambient light. Due to the light source emitted by Vcsel, the light will also be modulated into a uniform surface light source by Diffuser, and then emitted.
Optical lens is used to collect the reflected light and image it on the optical sensor. However, unlike ordinary optical lenses, a narrow-band filter is required to ensure that only light with the same wavelength as the emitted optical signal (ie, 940nm) can Enter, the purpose of this is to suppress incoherent light sources to reduce background noise, while preventing the sensor from being overexposed due to external light interference.
The imaging sensor is similar to the photosensitive element of a general camera. It is used to receive the reflected light and perform photoelectric conversion on the sensor. However, due to the principle of ToF, the photosensitive time of the sensor is very short, reaching the nanosecond level, so the single pixel size ratio usually the camera is much bigger.
The control unit is the driver IC of the laser transmitter. It can drive the laser with high-frequency pulses with an upper limit of 100MHz, while eliminating all kinds of interference to ensure that the driving waveform is a perfect square wave. The rising edge and falling edge time are about 0.2ns. , so as to effectively ensure the extraction of high-precision depth accuracy.
