Laser Pre-pulse Driver for Optoelectronic Sensor Timing
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Solution Overview
Problem
Optoelectronic sensors face challenges in achieving precise time measurements due to delays in laser light emission, which affects resolution and accuracy, especially at high precision levels, and results in unnecessary light emission that reduces measurement accuracy and poses eye protection concerns.
Innovation Solution
The laser is energized with a pre-pulse shortly before the actual pulse to drive it close to the lasing threshold, eliminating delays and reducing unnecessary light emission, allowing for precise timing and longer device lifespan without the need for a monitoring diode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the laser is biased above the lasing threshold to eliminate emission delay, then the response time is improved, but permanent light emission reduces measurement accuracy and poses eye safety concerns
Solution Approach 1:
The patent applies preliminary action by energizing the laser with a pre-pulse shortly before the actual measurement pulse. This pre-pulse drives the laser into the vicinity of the lasing threshold in advance, so that when the actual pulse arrives, the laser can respond immediately without the run-up delay that would otherwise occur. The key insight is that the laser is prepared in advance but only emits significant light during the actual measurement window, not continuously as with DC biasing.
Solution Approach 2:
The patent uses periodic action by replacing continuous DC biasing with pulsed energization. The laser is energized only during specific time intervals - a brief pre-pulse period followed by the actual measurement pulse - rather than maintaining constant current flow. This periodic approach eliminates the permanent streak light while maintaining the ability to respond quickly when needed.
2Reliability
If DC bias current is used to maintain laser above threshold, then emission delay is eliminated, but average optical power increases reducing eye safety margin
Solution Approach 1:
The patent replaces continuous DC biasing with periodic pulsed energization. The laser receives current only during brief intervals - a pre-pulse and the actual measurement pulse - rather than continuously. This dramatically reduces the average optical power while maintaining the reliability of timing precision, because the laser is prepared in advance with the pre-pulse and then operates at full capability during the measurement pulse.
Solution Approach 2:
The pre-pulse serves as preliminary action that prepares the laser in advance of the actual measurement. By driving the laser into the vicinity of the lasing threshold before the measurement pulse arrives, the system ensures reliable timing precision without needing to maintain high average power through continuous biasing. The laser is ready to respond immediately when the measurement pulse occurs.
3Stability of the object's composition
If monitor diode and regulating circuit are used to maintain constant optical power, then laser stability is improved, but device complexity increases
Solution Approach 1:
The patent extracts and eliminates the monitor diode and regulating circuit from the system. Instead of using these additional components to maintain constant optical power, the invention achieves stability through the timing and control of the pulsed energization scheme itself. The pre-pulse duration and amplitude are controlled to reliably bring the laser to the threshold region, and the subsequent measurement pulse delivers the required energy, eliminating the need for continuous optical monitoring and regulation hardware.
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 enables time precision below one nanosecond, reduces unwanted light emission, and extends the laser's working life, improving measurement accuracy and compliance with eye protection regulations.
Implementation Method 1
a light sensor (12) having a laser light source (14) and a driver circuit (16) for the laser light source (14) which generates light pulses (18)
Implementation Method 2
The laser is energized with a pre-pulse shortly before the actual pulse to drive it close to the lasing threshold, eliminating delays
Implementation Method 3
a short light pulse is transmitted in a pulse transit time method and the time up to the reception or remission or reflexion of the light pulse is measured
Data Source
AI summary
An optoelectronic sensor (10) having a light transmitter (12) for the transmitting of laser pulses (18) into a monitored region (24) by means of a laser light source (14) and having a driver circuit (16, 30) for the laser light source (14) is described which is designed to set the light transmitter (12) into a working state in which the laser light source (14) transmits a laser pulse (18) or into a preparatory state. The driver circuit (16, 30) is further designed to set the light transmitter (12) into the preparatory state in each case prior to the transmission of a laser pulse (18).