Dual-Current Drive Stabilizes Laser Emission Timing
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Solution Overview
Problem
Conventional distance measurement techniques using semiconductor lasers suffer from measurement errors due to the delay in light emission when a modulation current is supplied, affecting the accuracy of distance calculation.
Innovation Solution
The distance measurement apparatus employs a dual-current drive system, where a bias current and a modulation current are used to stabilize the light source's emission timing, ensuring the light source emits pulses with consistent timing by superimposing the currents, thereby reducing measurement errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a modulation current is supplied to the light source to emit light pulses, then distance measurement can be performed, but measurement errors occur due to delay in light emission timing
Solution Approach 1:
The patent applies preliminary action by pre-biasing the light source with a constant current before emitting light pulses. This preliminary current preparation ensures that the light source is ready to emit immediately when the modulation current is applied, eliminating the delay caused by the light source's inherent response time. The constant current maintains the light source in a state ready for immediate emission, thus resolving the timing delay issue.
Solution Approach 2:
The patent changes the electrical parameters supplied to the light source by using a composite current consisting of a constant bias current component and a modulation current component. This parameter change allows the light source to operate at an optimized bias point that minimizes emission delay while maintaining pulse emission capability for distance measurement.
2Measurement precision
If a modulation current is used to control light emission timing, then distance calculation can be performed, but errors are introduced due to light source emission characteristics
Solution Approach 1:
The patent introduces a constant current as an intermediary element that mediates between the modulation current and the light source. This constant current acts as a stabilizing intermediary that ensures consistent emission timing by maintaining the light source in a predetermined state, thereby reducing measurement errors caused by variations in light source emission characteristics.
Solution Approach 2:
The light source serves itself by maintaining its own optimal operating state through the constant bias current. This self-service mechanism allows the light source to automatically compensate for its inherent emission delays and variations without requiring external correction, improving the reliability of distance 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
This approach enhances the accuracy of distance measurement by aligning the light emission waveform with the desired pulse width, reducing errors related to the light source's emission characteristics.
Implementation Method 1
a light source 14 to emit irradiation light Le in response to a drive current supplied from a drive unit 15
Implementation Method 2
a light-receiving sensor 11 to receive reflection light Lr reflected from an object 2 irradiated with the irradiation light Le
Data Source
AI summary
An distance measurement apparatus includes a light source to emit irradiation light, circuitry to output, to the light source, a first current that changes in accordance of light-emission timing information defining at least turn-on timing of the light source, and a second current that does not change in accordance of the light-emission timing information, a sensor to detect reflection light reflected from an object irradiated with the irradiation light emitted from the light source. The circuitry calculates a distance to the object based on a detection amount of the reflection light detected by the sensor.