Laser Target Illumination Device Speckle Reduction
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Solution Overview
Problem
Existing laser target illumination systems suffer from speckle effects due to the coherence of laser radiation and atmospheric turbulence, leading to reduced image quality and making optical tracking challenging, especially with non-ideal target surfaces.
Innovation Solution
A laser target illumination device employing a pulsed laser source with an acousto-optic modulator and a phase plate with varying optical thicknesses, which deflects the beam path to create statistically distributed optical path differences, reducing speckle effects by generating spatial and temporal variations in the phase fronts of the emitted light pulses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If laser radiation is used to illuminate a target, then the target can be illuminated with high intensity and coherence, but speckle effects occur due to coherence and atmospheric turbulence, reducing image quality
Solution Approach 1:
The patent applies dynamics by making the beam path deflectable and movable through the phase plate. The first modulator deflects the laser beam dynamically, and the phase plate with varying optical thicknesses introduces random phase shifts as the beam passes through different regions. This dynamic configuration changes the interference pattern over time, reducing speckle effects while maintaining high illumination intensity.
Solution Approach 2:
The patent changes the optical parameters of the system by introducing a phase plate with spatially varying optical thicknesses. This creates random phase shifts in the beam path, transforming the coherent laser light into light with reduced coherence characteristics. The parameter change in optical path length directly addresses the speckle problem while preserving illumination intensity.
2Manufacturing precision
If a phase plate with varying optical thicknesses is introduced to reduce speckle effects, then image quality improves, but device complexity increases
Solution Approach 1:
The phase plate serves as an intermediary element between the laser source and the target. Rather than modifying the laser source itself or the target, the phase plate mediates the beam path by introducing controlled random phase shifts. This intermediary approach reduces speckle effects without requiring fundamental changes to the overall system architecture.
Solution Approach 2:
The patent replaces complex mechanical moving parts with a static phase plate that has spatially varying optical thicknesses. Instead of physically moving components to change the beam path, the system uses optical phase modulation through the phase plate, achieving speckle reduction with simpler, more reliable components.
3Manufacturing precision
If the beam path is deflected to create statistical optical path differences, then speckle effects are reduced, but the control system becomes more complex
Solution Approach 1:
The patent employs periodic action through the modulator that deflects the beam in a controlled, repeating manner. The beam is periodically swept across different regions of the phase plate, creating time-varying optical path differences. This periodic deflection pattern achieves speckle reduction through temporal averaging while using a relatively simple control mechanism.
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 effectively reduces speckle effects, enabling high-quality image capture and facilitating reliable optical tracking of fast-moving targets with simple and cost-effective implementation.
Implementation Method 1
A first modulator is also introduced into the beam path, the modulator being set up to deflect a direction of the beam path in a first plane. It is envisaged that the first modulator is an acousto-optic modulator.
Implementation Method 2
In addition, a phase plate is present in the beam path, which has a variety of optical thicknesses. The multiplicity of different optical thicknesses of the phase plate can preferably be implemented in that the phase plate has an uneven surface. This results in statistically distributed optical path differences of the light within the beam path.
Implementation Method 3
The lighting device according to the invention comprises a light source, which is a pulsed laser light source. The light source is set up to emit light along a beam path.
Implementation Method 4
due to the coherence of the laser radiation usually used in laser target illumination and the effect of the atmospheric turbulence occurring on the beam path as well as the not ideally flat surface structure of the target, interference-related disturbances can occur
Data Source
Figure 1
Figure 2~3
AI summary
The present invention relates to a lighting device (1), in particular for illuminating a target (3) to be combated, comprising a light source (10), in particular a laser light source, for emitting light along a beam path (4), a first modulator (7) which is inserted into the beam path (4) and is configured to manipulate a direction of the beam path (4) in a first plane (100), a phase plate (9) which is inserted into the beam path (4) and which has a plurality of different optical thicknesses (91, 92, 93), and a control device (8) which is connected to the light source (10) and the first modulator (7) and which is configured to control the first modulator (7) with different frequencies, so that the beam path (4) can be deflected up to a first angle (40) over a control period.