Integrated Light Source Driver for Precise ToF Pulse Timing
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Solution Overview
Problem
Time-of-flight camera systems require high temporal precision and control to accurately measure distances, which is challenging due to the uncertainty in light emission pulses and the need for high peak optical power while adhering to safety regulations.
Innovation Solution
A light source system with a driver integrated into a semiconductor die, utilizing a capacitor to store energy for generating a high drive current, allowing for rapid and precise control of light emission, including very short duration pulses with high optical power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a separate driver circuit is used to control the light source, then the control flexibility is improved, but the temporal precision and timing accuracy deteriorate due to longer signal paths and higher parasitic inductance
Solution Approach 1:
The driver circuit is integrated directly into the semiconductor die with the light source, merging previously separate components. This integration eliminates long signal paths and reduces parasitic inductance, achieving both control flexibility and high temporal precision simultaneously
2Power
If a large drive current is used to achieve high optical power, then the optical power output is improved, but the temporal precision deteriorates due to slower current rise times and longer pulse durations
Solution Approach 1:
The driver is integrated on the same semiconductor die as the light source, creating a compact layout that minimizes loop area and parasitic inductance. This enables fast current switching with large drive currents, achieving both high optical power and short pulse durations for high temporal precision
Solution Approach 2:
The integration moves the driver and light source from a planar PCB layout to a three-dimensional stacked configuration on the semiconductor die, reducing the current path length and enabling faster switching for high power applications
3Measurement precision
If the driver and light source are placed close together, then the temporal precision is improved, but the electrical resistance and inductance increase due to tighter routing constraints
Solution Approach 1:
The driver and light source are positioned in three-dimensional space on the semiconductor die, utilizing vertical stacking and short interconnects that minimize both resistance and inductance while maintaining close proximity for high temporal precision
4Power
If a high peak optical power is used to improve measurement range, then the measurement range is improved, but safety regulations may be violated due to excessive optical power output
Solution Approach 1:
The system uses pulsed operation with high peak power for short durations, allowing the average power to remain within safety limits while achieving high peak optical power for extended measurement range. The integrated driver enables precise pulse width control
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 achieves improved precision in distance measurement by ensuring accurate timing of light emission and reflection, while also reducing electrical resistance and inductance, and enhancing safety by limiting energy availability during faults.
Implementation Method 1
The driver includes a capacitor to store energy and then discharge to generate the drive current
Implementation Method 2
a light source (such as a laser or LED)... a light source, such as a laser, and a driver arranged to supply a drive current to the light source to turn the light source on to emit light
Data Source
AI summary
The present disclosure relates to a light source system suitable for use in a time of flight camera. The light source system includes a light source, such as a laser, and a driver arranged to supply a drive current to the light source to turn the light source on to emit light. The driver includes or is coupled to a capacitor to store energy and then discharge to generate the drive current. The driver can be integrated into a semiconductor die on which the light source is mounted. Thus, the driver can include within it the source of energy for the drive current and the light source and driver can be very close together. Therefore, the light source may be turned on and off very quickly, such as with a relatively large drive current, such as to output a high optical power, short duration light pulse.