Depth Scanning Image Sensor Using Segmented Pixel Exposure Timings
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Solution Overview
Problem
Existing 3D imaging technologies, such as those using SPADs, face challenges including limited fill factor, low quantum efficiency, especially in the near-infrared region, and high power consumption, which affect the signal-to-noise ratio and efficiency of depth sensing.
Innovation Solution
A novel depth sensing technique that utilizes a 2D image sensor with pixels driven by individual timings to acquire time-of-flight information, allowing for direct measurement of time-of-flight and derivation of depth information. This technique involves grouping pixels into subgroups and applying different exposure timings to reduce the number of images required for depth reconstruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If SPADs are used for direct TOF measurement, then time-of-flight measurement precision is improved, but fill factor is reduced and power consumption increases
Solution Approach 1:
The pixel array is divided into multiple subgroups, with different exposure timings applied to each subgroup. This segmentation allows the system to capture depth information across multiple time bins using standard photodetectors, achieving TOF measurement capability without requiring specialized SPAD pixels for each time sample.
Solution Approach 2:
The patent employs periodic light pulse emission with multiple exposure windows at different timings. By sequentially exposing pixel subgroups during different time intervals of the periodic light pulse cycle, the system reconstructs depth information through temporal sampling, replacing the need for continuous SPAD-based photon timing.
2Measurement precision
If multiple images are captured for depth reconstruction, then depth mapping resolution is improved, but productivity decreases due to increased processing time
Solution Approach 1:
The pixel array is segmented into multiple subgroups that are exposed at different timings simultaneously. This allows depth information for multiple time bins to be captured in a single light pulse cycle, reducing the number of sequential image captures needed while maintaining depth mapping resolution.
Solution Approach 2:
Exposure timings for different pixel subgroups are pre-configured to correspond to different depth ranges before light pulse emission. This preliminary timing arrangement enables simultaneous capture of depth information across multiple ranges in one shot, eliminating the need for sequential image capture and processing.
3Measurement precision
If exposure timings are optimized for near-infrared detection, then quantum efficiency is improved, but signal-to-noise ratio in other regions deteriorates
Solution Approach 1:
Different pixel subgroups are assigned different exposure timings optimized for detecting light pulses at different depths. This local optimization allows each subgroup to capture photons efficiently within its specific time window, improving overall quantum efficiency across the depth range while maintaining signal-to-noise ratio through temporal separation of measurements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed technique enhances the efficiency of depth sensing by reducing the number of images needed for 3D point mapping, improving the signal-to-noise ratio, and minimizing power consumption, while maintaining effective depth resolution.
Implementation Method 1
The time for the light to reach the camera depends on the distance of the point of reflection on the surface of the object to the camera. Knowledge of this time enables the three-dimensional structure of the object to be inferred.
Implementation Method 2
a photodetector configured to detect the reflected light
Data Source
AI summary
A imaging device according to the present disclosure comprises a pixel array comprising a plurality of pixels; a signal generator for generating an exposure timing scheme defining exposure durations for ones of the pixels grouped in at least one subgroup of the pixels, wherein ones of the exposure durations cover at least portions between a frame start time and a frame end time of predefined frame; a synchronizer for synchronizing a generation of a light pulse with the exposure timing scheme; and means for readout of charges accumulated in grouped ones of the pixels.