A 250 m Direct Time-of-Flight Ranging System Based on a Synthesis of Sub-Ranging Images and a Vertical Avalanche...

Area of Science:

• Optoelectronics
• Image Sensors
• Photonics

Background:

• Conventional light detection and ranging (LiDAR) systems often suffer from insufficient resolution and limited range.
• Indirect CMOS image sensor (CIS) time-of-flight (TOF) technologies typically have a restricted operational distance.

Purpose of the Study:

• To develop a novel direct TOF CIS with extended ranging capabilities and high resolution.
• To overcome the limitations of existing LiDAR and indirect TOF CIS technologies.

Main Methods:

• A 688 × 384 pixels array of vertical avalanche photodiodes (VAPD) was utilized in the CIS.
• Each pixel incorporates a VAPD with a four-transistor circuit and an analog capacitor for avalanche pulse accumulation.
• High-power, near-infrared (NIR) laser pulses (<50 ns, 6 kHz) were employed, with global VAPD gating for sub-photon level signal detection.

Main Results:

• Achieved depth map imaging with 10 cm lateral resolution over a range of 1 m to 250 m.
• Successfully synthesized sub-range images from photon counts to create a comprehensive depth map.
• Demonstrated the capability to count individual avalanche pulses for precise signal extraction.

Conclusions:

• The developed direct TOF CIS offers a significant advancement over conventional LiDAR and indirect TOF systems in terms of resolution and range.
• The in-pixel circuit design enables high-sensitivity detection and accurate depth measurement.
• This technology has the potential to replace existing solutions in applications requiring long-range, high-resolution 3D imaging.