VCSEL Driving Circuit Stabilizes Laser Mode
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Time of flight measurement technologies, such as LIDAR, face challenges in achieving high beam quality and stable laser modes for reliable distance detection, particularly with Vertical Cavity Surface Emitting Lasers (VCSELs) and Vertical Extended Cavity Surface Emitting Lasers (VECSELs), due to issues like pulse length, duty cycle, and jitter, which affect the precision and reliability of distance measurements.
Innovation Solution
A driving circuit is used to provide electrical energy to VCSELs or VECSELs, enabling laser pulses with a pulse length of less than 100 ns and a duty cycle of less than 5%, with additional pre-current energy applied to stabilize the laser operation and minimize delay, ensuring the lasers emit under defined optical conditions, thereby maintaining a stable fundamental mode and improving beam quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If VCSELs operate with short pulse lengths (<100 ns) and low duty cycles (<5%), then time of flight measurement precision is improved, but laser mode stability deteriorates
Solution Approach 1:
The patent applies preliminary action by providing a pre-current to the VCSEL before each laser pulse. This pre-current prepares the laser in advance by establishing a stable carrier density and temperature condition, ensuring the laser operates in a stable fundamental mode during the subsequent short pulse emission, thereby resolving the contradiction between short pulse duration and mode stability.
2Measurement precision
If VCSELs emit laser pulses with short duration (<100 ns), then distance detection resolution is improved, but beam quality deteriorates
Solution Approach 1:
The pre-current applied before each pulse prepares the VCSEL active region in advance, ensuring optimal carrier distribution and temperature conditions. This preliminary preparation enables the laser to generate high-quality fundamental mode beams even during extremely short pulse durations, thus maintaining both distance detection resolution and beam quality.
3Stability of the object's composition
If additional energy is provided to VCSELs before laser pulses, then laser pulse stability is improved, but energy consumption increases
Solution Approach 1:
The patent applies partial action by providing a pre-current that is below the threshold for continuous wave lasing. This pre-current is sufficient to prepare the laser for stable pulsed operation but consumes less energy than continuous wave operation would require. The pre-current is applied only for the necessary duration before each pulse, optimizing the balance between pulse stability and energy consumption.
4Temperature
If VCSELs operate at low duty cycles (<5%), then heat management is improved, but laser mode stability deteriorates
Solution Approach 1:
The pre-current applied before each pulse at low duty cycle operation serves to rapidly establish the necessary temperature and carrier conditions for stable fundamental mode emission. Since the duty cycle is low, the laser has time to cool between pulses, and the pre-current efficiently prepares the laser for each subsequent pulse without requiring continuous high power operation, thus maintaining both heat management and mode stability.
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 beam quality and stability of laser pulses, allowing for reliable detection of reflected light and improved time of flight measurements by minimizing delays and jitter, thus enabling precise distance detection.
Implementation Method 1
The driving circuit is adapted to provide electrical energy to the Vertical Cavity Surface Emitting Laser or Vertical Extended Cavity Surface Emitting Laser such that the Vertical Cavity Surface Emitting Laser or Vertical Extended Cavity Surface Emitting Laser emits laser pulses
Implementation Method 2
The measurements are based on preinstalling a thermal lens through a current bias, and subsequently, modulating a pulse onto the bias
Implementation Method 3
The vertical cavity surface emitting laser is arranged to operate in a stable fundamental mode during that part of the laser pulses
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention describes a laser sensor module comprising at least one Vertical Cavity Surface Emitting Laser (100) and at least one driving circuit (120). The driving circuit (120) is adapted to provide electrical energy to the Vertical Cavity Surface Emitting Laser (100) such that the Vertical Cavity Surface Emitting Laser (100) emits laser pulses (345) with a pulse length (356) of less than 100 ns and a duty cycle of less than 5 % in comparison to a continuous laser emission. The driving circuit (120) is further adapted to provide additional energy to the Vertical Cavity Surface Emitting Laser (100) at least 100 ns prior to at least a part of the laser pulses (345) such that the part of the laser pulses (345) are emitted under defined optical conditions. The invention further describes a distance detection device comprising the laser sensor module and a method of driving the laser sensor module. The additional energy is preferably provided by means of a current pre-pulse (335) which is applied to the V(E)CSEL prior to preferably each laser pulse (345). The current pre-pulse is preferably arranged such that no laser light is emitted by means of the V(E)CSEL. The V(E)CSEL are enabled to emit the laser pulses (345) under defined optical conditions such that the time of emission and the pulse shape of the laser pulses (345) is well defined. Well defined time of emission and the pulse shape of the laser pulses (345) enable a reliable detection of reflected laser light (117) which corresponds to the emission of the respective laser pulse (345).