Indirect Time-of-Flight Ranging Device with Differential Readout Circuit
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Solution Overview
Problem
Common time-of-flight ranging devices face challenges in effectively mitigating the impact of strong and variable background light during indirect ranging, leading to insufficient dynamic range and inaccurate distance measurements.
Innovation Solution
The proposed time-of-flight ranging device employs a light emitting module, multiple sensing pixels, and a differential readout circuit to differentiate between reflected light pulses and background light, generating digital data that allows for accurate distance calculations by subtracting background noise, thereby enhancing dynamic range and precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional background light sensing is performed by the common time-of-flight ranging device, then background information can be obtained for reducing the impact of background light, but the time interval between background light sensing and ranging sensing is too long, causing the obtained background information to be ineffective
Solution Approach 1:
The patent performs background light sensing in advance within the same frame period before the actual ranging measurement. By completing the background light sensing operation beforehand and storing the background information in a register, the system ensures that the background data is fresh and applicable when the ranging measurement is performed, eliminating the effectiveness loss caused by long time intervals.
2Measurement precision
If the common time-of-flight ranging device performs additional background light sensing, then background information can be obtained, but the device complexity increases due to multiple sensing operations
Solution Approach 1:
The patent merges the background light sensing operation with the ranging measurement operation by performing both within the same frame period. The sensing pixel is configured to perform background light sensing in a first cycle and ranging measurement in a second cycle, with both operations sharing the same hardware resources and being coordinated through a unified control mechanism, thereby reducing overall system complexity.
Solution Approach 2:
The sensing pixel is designed to perform multiple functions: it can perform background light sensing in one cycle and ranging measurement in another cycle within the same frame period. This multi-functionality allows a single hardware component to handle both operations, reducing the need for separate dedicated hardware and simplifying the overall device architecture.
3Adaptability or versatility
If the common time-of-flight ranging device operates under strong background light conditions, then ranging can still be performed, but the dynamic range is insufficient leading to inaccurate measurements
Solution Approach 1:
The patent extracts the background light component from the total light signal received by the sensing pixel. By performing background light sensing separately and storing the background information, the system can subtract this extracted background component from the total signal during ranging measurement, thereby isolating the reflected light signal from the target and improving measurement accuracy under strong background light conditions.
Solution Approach 2:
The patent applies preliminary anti-action by measuring the background light level in advance within the same frame period and using this information to compensate for the background light impact during the subsequent ranging measurement. This preliminary measurement allows the system to pre-calculate the compensation value that will be applied to eliminate background light interference, thereby maintaining measurement precision in challenging lighting conditions.
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 solution enables the device to accurately measure distances by effectively removing background noise and improving dynamic range, allowing for more precise indirect time-of-flight ranging even in conditions with strong background light.
Implementation Method 1
The light emitting module is configured to emit a light pulse to a sensing target, so that the sensing target reflects a reflected light pulse
Implementation Method 2
The first sensing pixel is configured to respectively perform sensing in a first cycle in a first frame period and a second cycle in a second frame period to respectively generate a first sensing signal and a second sensing signal
Data Source
AI summary
A time-of-flight ranging device suitable for indirect time-of-flight ranging is provided. The time-of-flight ranging device includes a light emitting module, a first sensing pixel, a second sensing pixel, a differential readout circuit, and a processing circuit. The light emitting module emits a light pulse to a sensing target, so that the sensing target reflects a reflected light pulse. The first sensing pixel generates a first sensing signal and a second sensing signal. The second sensing pixel generates a third sensing signal and a fourth sensing signal. The differential readout circuit generates first digital data according to the first sensing signal and the third sensing signal and generates second digital data according to the second sensing signal and the fourth sensing signal. The processing circuit calculates a distance between the time-of-flight ranging device and the sensing target according to the first digital data and the second digital data.