Optical Sensor Time Offset Correction for Distance Measurement Accuracy
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Solution Overview
Problem
Existing methods for measuring distance using optical sensors result in a narrow range of measurable distance and difficulty in accurately determining if an optical delay is within the light emission cycle, leading to inaccurate measurements due to jitter and cycle variations.
Innovation Solution
An optical sensor system comprising a light emitting element, a first photon-count light receiving unit for signal light, a second photon-count light receiving unit for reference light, and a time difference extraction circuit with DLLs and waveform generation units that divide pulses to extract and correct time offsets, ensuring accurate determination of optical delay within the light emission cycle without narrowing the measurable distance range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a delay locked loop circuit is used to measure distance by converting delay amount into digital value, then distance measurement is achieved, but measurement accuracy deteriorates when detection object distance is almost zero due to jitter and cycle variations
Solution Approach 1:
The patent applies preliminary action by measuring the time difference between the first light receiving unit and second light receiving unit before performing distance calculation. The time difference measurement is conducted separately from the distance computation, allowing jitter and cycle variations to be isolated and corrected before final measurement, thereby improving accuracy at zero distance
Solution Approach 2:
The patent implements feedback by using the measured time difference to correct the distance measurement result. The system continuously monitors the time difference between reference light and signal light, and uses this information to adjust and correct the final distance measurement, eliminating errors caused by jitter and cycle variations
2Stability of the object's composition
If averaging is performed with measurement values from multiple cycles, then measurement stability is improved, but measurement accuracy deteriorates due to inclusion of jitter values near maximum
Solution Approach 1:
The patent extracts the time difference measurement from the overall distance measurement process. By separately measuring the time difference between light receiving units and then using this extracted value for distance calculation, the system avoids including jitter values in the averaging process, maintaining both stability and accuracy
3Productivity
If the light emission cycle is shortened to increase measurement speed, then productivity is improved, but the measurable distance range is narrowed
Solution Approach 1:
The patent transitions from measuring distance directly within a single light emission cycle to measuring time difference across multiple cycles. By using the time difference between reference light and signal light received at different units, the system can calculate distances beyond a single cycle duration, expanding the measurable range while maintaining high measurement speed
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 system accurately determines whether an optical delay is within the light emission cycle, maintaining a wide range of measurable distances and correcting for jitter, thereby improving measurement accuracy.
Implementation Method 1
an avalanche photodiode utilizing an avalanche amplification (avalanche) effect of a photodiode has been conventionally used as a light receiving element that detects weak light at high speed
Implementation Method 2
When a reverse bias voltage equal to or more than the breakdown voltage is applied, the avalanche photodiode operates in a Geiger mode. The avalanche photodiode in the Geiger mode causes an avalanche phenomenon even in a case of incidence of a single photon, so that a large output current is obtained
Data Source
AI summary
Whether an optical delay on a space optical path is within a light emission cycle is accurately determined without narrowing a range of a measurable distance in the light emission cycle. A DFF 1 that divides an output pulse of a first DLL (121) by two to provide a first time offset and a DFF 2 that divides an output pulse of a second DLL (122) by two to provide a second time offset are included, and at least following mathematical formulas (1) and (2) are satisfied:O1=m·T½ (1)0<O1<(N−1)·T1 (2)(where, m≥1),when a time corresponding to a difference between the first time offset and the second time offset is O1 and the first cycle is T1.