Optical Emitter Driver Circuit for Fast Uniform TOF Pulses
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Time-of-flight ranging devices face challenges in generating high-intensity, short-duration optical pulses due to parasitic inductances, capacitances, and resistances, leading to slow rise times and non-uniform pulse amplitudes, which can exceed laser safety limits and compromise depth uncertainty in distance measurements.
Innovation Solution
A driver circuit with an inductor, switches, and a current sensor is used to control the optical light emitter, employing pulse-width modulation and different frequency timing signals to regulate current and generate high-frequency, high-intensity optical pulses with uniform amplitude, while maintaining a low supply voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional current driving circuits are used to generate optical pulses, then the circuit structure is simple, but the pulse rise time is slow and amplitude is non-uniform due to parasitic inductances, capacitances, and resistances
Solution Approach 1:
The circuit is segmented into distinct functional blocks: a current source providing baseline current, a switching network with multiple switches (S1, S2, S3) controlled by phase-shifted signals, and a sensor feedback loop. This segmentation allows each component to be optimized independently for fast switching while maintaining overall circuit manageability.
Solution Approach 2:
The patent employs periodic switching actions with specific duty cycles and phase relationships. The switches are activated in sequence with controlled duty cycles to generate sharp current pulses through the inductor, achieving fast rise times through periodic on-off actions rather than continuous control.
2Illumination intensity
If high current pulses are generated to achieve high optical intensity, then the optical pulse intensity is sufficient, but laser safety limits may be exceeded
Solution Approach 1:
The patent uses periodic pulse-width modulation where the optical emitter is driven by controlled current pulses with specific duty cycles. This allows the average power to remain within safety limits while peak intensities during the pulse are sufficient for accurate time-of-flight measurement, thus resolving the contradiction between intensity and safety.
Solution Approach 2:
A sensor detects the actual current flowing through the inductor and provides feedback to the control circuit. This feedback mechanism enables precise regulation of the current pulse amplitude, ensuring that the optical intensity remains within safe limits while achieving sufficient measurement signal strength.
3Measurement precision
If simple current driving is used, then the circuit is easy to implement, but depth uncertainty in distance measurements increases
Solution Approach 1:
The sensor provides real-time feedback on the current through the inductor to the control circuit, enabling closed-loop control of the optical pulse parameters. This feedback ensures uniform pulse amplitudes and precise timing, directly improving depth measurement precision by reducing uncertainty in the optical signal characteristics.
Solution Approach 2:
The patent dynamically adjusts multiple parameters including current amplitude, pulse width, and switching frequency through coordinated control of multiple switches. These parameter changes are optimized to maximize measurement precision by ensuring consistent, high-quality optical pulses with uniform amplitudes and precise timing.
4Illumination intensity
If high supply voltage is used to overcome parasitic effects, then the optical pulse intensity is maintained, but power consumption increases
Solution Approach 1:
The patent uses periodic switching with controlled duty cycles to deliver high current pulses only when needed, rather than maintaining continuous high voltage. This periodic action allows the system to achieve high optical intensity during measurement windows while consuming less average power, resolving the contradiction between intensity and power consumption.
Solution Approach 2:
The feedback loop monitors the actual current and adjusts the switching control to maintain the required optical pulse intensity while optimizing power delivery. This ensures that sufficient voltage is applied only when necessary to overcome parasitic effects and maintain pulse quality, reducing overall power consumption.
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 solution enables the generation of optical pulses with consistent and high power, improving depth uncertainty and adhering to laser safety limits, while reducing the required supply voltage and minimizing parasitic effects.
Implementation Method 1
an inductor having a first of its nodes coupled to a current driver
Implementation Method 2
a second branch for conducting a current through the optical light emitter
Implementation Method 3
Laser diodes, such as VCSELs, are light emitting devices capable of emitting light with an intensity that depends on a level of current driven through them
Data Source
AI summary
The present disclosure relates to a driver circuit for an optical light emitter of a ranging device, the driver circuit comprising: an inductor having a first of its nodes coupled to a current driver; a first branch comprising a first switch coupled between the second node of the inductor and a first supply voltage rail; a second branch for conducting a current through the optical light emitter, the second branch being coupled between the second node of the inductor and the first supply voltage rail; and a current sensor configured to detect the current passing through the inductor and to provide a feedback signal to the current driver.