TOF Sensor Pulse Segmentation for Accurate Distance Measurement
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Solution Overview
Problem
Existing optical sensors using avalanche photodiodes in Geiger mode face challenges in accurately distinguishing between valid and invalid data, leading to prolonged time requirements for acquiring sufficient valid data for precise distance measurements due to reduced probability of detecting reflected light pulses.
Innovation Solution
An optical sensor system that includes a light-emitting unit, a first light-receiving unit, a first calculation unit, and a distance calculation unit, which calculates the distance based on the ratio of pulses during light-emission and non-light-emission periods to differentiate between reflected light and ambient light, ensuring accurate distance measurement in a shorter time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If avalanche photodiode in Geiger mode is used to detect weak light, then detection sensitivity is improved, but ability to distinguish between valid and invalid data deteriorates
Solution Approach 1:
The patent segments the detection data into two categories: pulses occurring during light-emission periods (potential valid data) and pulses during non-light-emission periods (invalid data). By temporally segmenting the detection window and applying different evaluation criteria to each segment, the system maintains high detection sensitivity while improving data discrimination accuracy.
2Measurement precision
If multiple valid data points are acquired to ensure measurement accuracy, then measurement precision is improved, but measurement time increases
Solution Approach 1:
The patent extracts and counts only the pulses that occur during light-emission periods, excluding pulses from non-light-emission periods. This extraction of relevant valid data from the total detected pulses allows the system to achieve sufficient measurement accuracy with fewer data points, thereby reducing the time required for data acquisition.
3Reliability
If quenching resistance is added to obtain binary pulse output, then signal clarity is improved, but probability of detecting reflected light pulses decreases
Solution Approach 1:
The patent applies preliminary action by generating light pulses before expecting reflected light returns. The light-emission periods are timed to precede the expected arrival of reflected light, creating a predetermined detection window. This allows the system to distinguish valid reflected light pulses from invalid ambient light pulses based on their temporal occurrence, thereby maintaining detection probability while ensuring signal clarity through the quenching resistance.
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
Enables highly accurate distance measurement in a shorter time by effectively distinguishing between valid and invalid data, thereby reducing the time needed to acquire the required number of valid data points.
Implementation Method 1
an avalanche photodiode using the avalanche amplification (avalanche) effect of a photodiode has been used
Implementation Method 2
a light-emitting unit that emits light in accordance with reference pulses
Data Source
AI summary
A TOF sensor includes: a light-emitting element that emits light in accordance with reference pulses; a first light-receiving unit that outputs pulses in response to light incident thereon; a first digital computation unit that calculates the number of third output pulses of the first light-receiving unit in response to reflected light incident thereon; and a distance computation unit that calculates the distance from this device to the object if the number of third output pulses is greater than a first reference value.