A Hybrid ToF Image Sensor for Long-Range 3D Depth Measurement Under High Ambient Light Conditions

A 134×132 4-Tap CMOS Indirect Time-of-Flight Range Imager Using In-Pixel Memory Array With 10 Kfps High-Speed Mode and High Precision Mode

“…In contrast, the short pulse (SP) modulation prepared by 4-tap 1-drain iToF pixel has been reported to have better ambient light tolerance due to the concentrated light energy from the emitter [15], [16]. In addition, the range-shifted technique can be adopted to increase the number of timewindows (TWs) for long-range detection [11], [17].…”

“…In an iToF system, it has been demonstrated that the signalto-noise ratio (SNR), modulation frequency, and demodulation contrast (DC) are inversely proportional to the depth noise [9]. Therefore, designs with higher full-well capacity (FWC) are often preferred to achieve higher system SNR and ambient light tolerance [10], [11]. In addition, a smaller pixel pitch is also desired to improve DC when increasing the modulation frequency.…”

Calibration of the reflectivity-related error of the indirect time-of-flight imaging systems

“…Variance in the system 𝜎 is considered an invariant constant, and A is the amplitude calculated in equation (5). So when the reflectivity is lower, as the received amplitude decreases, the measurement phase variance will increase, leading to greater fluctuations in wiggling errors.…”

“…Nowadays, the main methods for three-dimensional imaging include the stereovision method, 1 structured light method, 2 time-of-flight method, 3 and so on. The time-of-flight imaging system is divided into direct time-of-flight(dToF) 4 and indirect time-of-flight(iToF) 5 according to different methods of calculating time-of-flight. Due to the advantages of high real-time, high integration, and low cost, the indirect time-of-flight imaging system is widely used in many fields such as 3D imaging, automatic driving, agricultural medical treatment, and robot navigation .…”

A Time-of-Flight Image Sensor Using 8-Tap P-N Junction Demodulator Pixels

“…Because of the circuit complexity required for per-pixel processing in real time, long-range dToF image sensors for operation under direct sunlight while having a high range-image resolution will remain an issue. In contrast, another type of ToF image sensors, the indirect ToF (iToF) image sensors, have a distinct merit of high depth-image resolution because of their simple pixel configurations and simple processing for ToF measurements [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. There are two types of light modulation Sensors 2023, 23, 3987 2 of 18 and in-pixel demodulation methods in iToF: the continuous wave (CW) modulation and the pulse or short pulse (SP) modulation.…”