Laser Drive Capacitor Layout for Faster ToF Light Pulses
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Solution Overview
Problem
Measurement devices using the Time of Flight method for three-dimensional shape measurement require a shorter rise time of light emission from a laser unit to achieve higher accuracy, which is hindered by the inductance of the driving circuit, leading to longer rise times and reduced measurement precision.
Innovation Solution
A light-emitting device with a laser unit driven by a combination of capacitive elements, where a low-ESL capacitor and a non-low-ESL capacitor are used to supply the driving current, with the low-ESL capacitor having a shorter electric current path, reducing the equivalent series inductance and enhancing the rise time of the driving signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional capacitive element with longer electric current path is used, then the capacity is sufficient, but the equivalent series inductance increases and the rise time of light emission becomes longer
Solution Approach 1:
The patent divides the capacitive element into multiple segments (first capacitive element and second capacitive element) with different capacities and equivalent series inductances. The first capacitive element has smaller capacity and smaller equivalent series inductance, while the second capacitive element has larger capacity and larger equivalent series inductance. This segmentation allows the system to simultaneously achieve fast rise time (through the first element) and sufficient energy storage (through the second element), resolving the contradiction between speed and reliability in the ToF measurement system.
2Quantity of substance
If the length of electric current path is increased, then the capacity of capacitive element increases, but the inductance of electric current path increases causing slower signal rising
Solution Approach 1:
The patent applies local quality by assigning different characteristics to different capacitive elements based on their specific roles. The first capacitive element is designed with smaller equivalent series inductance and shorter electric current path to provide fast signal rising, while the second capacitive element is designed with larger capacity to provide sufficient energy storage. Each element's local characteristics are optimized for its specific function, resolving the contradiction between quantity and 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
This configuration significantly reduces the rise time of the driving electric current pulse, improving the accuracy of three-dimensional shape measurement by minimizing the inductance of the electric current path and allowing for faster light emission, thus enhancing the measurement precision.
Implementation Method 1
a first capacitive element and a second capacitive element that supply a driving electric current to the laser unit
Implementation Method 2
Measurement of a three-dimensional shape of an object to be measured according to a Time of Flight (ToF) method using a flight time of light requires reduced inductance of an electric current path
Data Source
AI summary
A light-emitting device includes a laser unit; and a first capacitive element and a second capacitive element that supply a driving electric current to the laser unit; wherein the first capacitive element has a smaller capacity and smaller equivalent series inductance than the second capacitive element, and a length of a first electric current path along which the driving electric current output from the first capacitive element returns to the first capacitive element is shorter than a length of a second electric current path along which the driving electric current output from the second capacitive element returns to the second capacitive element.