Photodetection Device Ambient Light Separation TOF
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Solution Overview
Problem
Current photodetection systems face challenges in enhancing detection accuracy, particularly in Time OF Flight (TOF) methods, where ambient light interference and limited control signal frequencies restrict the precision of distance measurement.
Innovation Solution
A photodetection device and system incorporating a light-receiving section, multiple switches, counters, and a signal generator that generate pulse signals and control signals to shift pulse periods, allowing for improved counting processing and enhanced signal processing to differentiate between reflected light and ambient light components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional TOF method with single accumulation section is used, then device complexity is low, but detection accuracy is insufficient
Solution Approach 1:
The patent divides the single accumulation section into multiple accumulation sections (first accumulation section and second accumulation section). Each section accumulates electric charge from light-receiving elements during different time periods, enabling separate processing of reflected light signals and ambient light signals. This segmentation allows for improved detection accuracy through differential processing while maintaining manageable device complexity.
Solution Approach 2:
The patent implements periodic switching between different accumulation modes using control signals. The light-receiving element alternates between accumulating charge in the first accumulation section during light emission periods and in the second accumulation section during non-emission periods. This periodic action enables temporal separation of signal accumulation, improving detection accuracy through time-gated measurement while using simple switching circuitry.
2Measurement precision
If control signal frequency is increased to improve measurement precision, then detection accuracy improves, but ambient light interference increases
Solution Approach 1:
The patent extracts and separately accumulates ambient light components in the second accumulation section during non-emission periods. By isolating the ambient light signal from the reflected light signal through temporal separation and dedicated accumulation sections, the system can subsequently subtract the ambient light component from the total signal, thereby improving measurement precision while explicitly accounting for and removing ambient light interference.
Solution Approach 2:
The patent converts the harmful effect of ambient light into a useful measurement component. Instead of simply filtering out ambient light, the system accumulates it separately in the second accumulation section during non-emission periods. This ambient light accumulation is then used to calculate and subtract the ambient light component from the reflected light measurement, transforming the previously harmful interference into a beneficial reference signal that enables more accurate compensation.
3Measurement precision
If multiple accumulation sections are used to separate reflected light and ambient light, then signal-to-noise ratio improves, but device complexity increases
Solution Approach 1:
The patent merges the functions of multiple accumulation sections with a single light-receiving element and shared readout circuitry. The first and second accumulation sections are integrated into the same pixel structure, sharing common components such as the light-receiving element, transfer switches, and readout amplifiers. This merging approach enables separate accumulation of reflected light and ambient light signals while avoiding the complexity of completely independent detector systems, thereby improving signal-to-noise ratio without proportionally increasing device complexity.
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
This configuration enhances the signal-to-noise ratio, reducing measurement errors and improving detection accuracy by effectively separating reflected light components from ambient light, thereby improving the precision of distance measurements.
Implementation Method 1
a light-receiving element, and is configured to generate a pulse signal including a pulse corresponding to a result of light reception by the light-receiving element
Data Source
AI summary
A photodetection device according to the present disclosure includes: a light-receiving section that includes a light-receiving element, and generates a pulse signal including a pulse corresponding to a result of light reception by the light-receiving element; a plurality of switches that is each turned on or off on the basis of a corresponding control signal of a plurality of control signals, and each transmits the pulse signal by being turned on in a pulse period of the corresponding control signal of the plurality of control signals; a plurality of counters that is provided corresponding to the plurality of switches, and each performs counting processing on the basis of the pulse signal supplied through a corresponding switch of the plurality of switches to generate a first count value; and a signal generator that generates the plurality of control signals in a detection period to sequentially shift the respective pulse periods of the plurality of control signals by a unit period having a shorter time length than the pulse period.