An 80 × 60 Flash LiDAR Sensor With In-Pixel Delta-Intensity Quaternary Search Histogramming TDC

This article presents a flash light detection and ranging (LiDAR) sensor featuring an in-pixel histogramming time-to-digital converter (hTDC) based on a delta-intensity quaternary search (DIQS) technique. The proposed 12-b DIQS hTDC is a two-step converter consisting of a 6-b coarse hTDC and a 7-b f...

Full description

Saved in:
Bibliographic Details
Published in:IEEE journal of solid-state circuits 2022-11, Vol.57 (11), p.3200-3211
Main Authors: Park, Seonghyeok, Kim, Bumjun, Han, Su-Hyun, Cho, Jun-Hee, Chun, Jung-Hoon, Choi, Jaehyuk, Kim, Seong-Jin
Format: Article
Language:English
Subjects:
3-D imager
CMOS depth sensor
CMOS image sensors
delta intensity
histogramming
Image acquisition
Laser radar
Lidar
light detection and ranging (LiDAR)
Luminous intensity
Pixels
quaternary search
Redundancy
Search methods
Sensors
single-photon avalanche diode
Single-photon avalanche diodes
Subframes
time-of-flight (ToF)
time-to-digital converter (TDC)
Citations: Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:This article presents a flash light detection and ranging (LiDAR) sensor featuring an in-pixel histogramming time-to-digital converter (hTDC) based on a delta-intensity quaternary search (DIQS) technique. The proposed 12-b DIQS hTDC is a two-step converter consisting of a 6-b coarse hTDC and a 7-b fine hTDC with 1-b redundancy. The DIQS hTDC synthesizes depth maps with three subframes from the coarse mode and a single subframe from the fine mode, achieving 100-ps resolution without a clock frequency of a few gigahertz. The DIQS repeats dividing the time range of a current step into four periods and finding the location where a target object is placed by comparing the number of events in each period, which is similar to the binary search method but doubles its operating speed. Two time-of-flight (ToF) bits are consecutively determined in every coarse step, and seven ToF bits are estimated by the indirect ToF technique with photon counts. An up-down counter is employed to reduce the memory size by half and enable the delta-intensity technique that can extend the dynamic range by suppressing the uniform background light. The prototype LiDAR with an 80\times60 pixel array was fabricated in a 110-nm CMOS image sensor (CIS) process and fully characterized. The maximum detectable range is measured to 45 m with a success rate of 100% at night and 60% under 70-klux background light. The depth accuracy and precision are 2.5 and 1.5 cm from 3 to 4.5 m indoor, respectively, and the precision is maintained to 1.8 cm for the target located at a 1.5-m distance under 60-klux background light. Inherent time-gating and differential signaling of the DIQS hTDC effectively suppress common-mode noise, accomplishing real-time acquisition of depth images with 30 frames/s in a 9-m range at 30-klux background light.
ISSN:0018-9200
1558-173X
DOI:10.1109/JSSC.2022.3202247