Speckle Modulator for Laser Illumination Noise Reduction
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Solution Overview
Problem
In imaging systems using coherent light, such as laser illumination, speckle noise appears due to the interference of light scattered from uneven surfaces, hindering image clarity and affecting both electronic imaging and biological retinas.
Innovation Solution
An illuminating device with a speckle modulator that generates repetitive illumination pulse groups, including a vibration device to mechanically change the optical fiber's phase or wavelength, synchronizing the illumination and modulation timing to optimize the speckle reduction effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If coherent light (laser) is used for illumination, then illumination intensity and directionality are improved, but speckle noise appears on the imaging surface
Solution Approach 1:
The patent applies dynamics by mechanically vibrating the optical fiber during illumination. The vibration device causes the optical fiber to vibrate at frequencies between 100 Hz to 10 kHz, which dynamically changes the optical path and modulates the speckle pattern. This dynamic approach allows the system to maintain high illumination intensity from coherent light while reducing speckle noise through temporal averaging of multiple speckle patterns during the exposure period.
Solution Approach 2:
The patent implements periodic action through controlled vibration of the optical fiber. The vibration device generates periodic mechanical vibrations that cause regular modulation of the optical fiber's position and shape. This periodic vibration creates time-varying speckle patterns that are averaged during image acquisition, effectively reducing speckle noise while maintaining the benefits of coherent light illumination.
2Object-affected harmful factors
If optical fiber is vibrated to change speckle pattern, then speckle noise is reduced, but device complexity increases
Solution Approach 1:
The patent replaces complex optical or electronic speckle reduction systems with a simple mechanical vibration device. Instead of using complex optical elements like diffusers or spatial light modulators, the invention uses a straightforward mechanical vibration mechanism attached to the optical fiber. This substitution significantly reduces device complexity while achieving effective speckle noise reduction through mechanical modulation of the optical fiber.
3Productivity
If exposure time is shortened for high frame rate imaging, then productivity is improved, but speckle reduction effect is weakened
Solution Approach 1:
The patent applies preliminary action by pre-vibrating the optical fiber before and during the exposure period. The vibration device is activated prior to image acquisition and continues vibrating throughout the exposure, ensuring that the speckle pattern is already modulating when the sensor captures the image. This preliminary and continuous vibration ensures that even very short exposure times capture averaged speckle patterns, maintaining speckle reduction effectiveness at high frame rates.
Solution Approach 2:
The patent uses dynamics to enable high frame rate imaging with effective speckle reduction. By continuously vibrating the optical fiber during the entire imaging sequence, the system dynamically modulates the speckle pattern at frequencies that ensure adequate averaging even within microsecond exposure times. This dynamic approach allows the system to achieve both high productivity and effective speckle noise reduction.
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
Effectively reduces speckle noise by averaging overlapping speckle patterns, improving image clarity and stability, even at high imaging frame rates or short exposure times, through synchronized pulse width modulation and speckle modulation.
Implementation Method 1
a vibration device configured to vibrate an optical fiber is provided. When the optical fiber is vibrated by the vibration device, a phase change of light due to a mode conversion of laser light occurs inside the optical fiber.
Implementation Method 2
a phase change of light due to a mode conversion of laser light occurs inside the optical fiber
Implementation Method 3
light scattered from the unevenness (concavo-convex), etc. of an observation object interferes, and a fine light-dark pattern is formed on the imaging surface or the retina
Implementation Method 4
laser light emitted from a laser light source enters an entrance end of an optical fiber and is then emitted as illumination light from an exit end of the optical fiber
Data Source
AI summary
An illuminating device includes an illumination light generator configured to generate illumination pulses of coherent light, and a speckle modulator configured to modulate speckle caused by the coherent light. The illumination pulse generator repeatedly generates a single illumination pulse group including a plurality of illumination pulses as a repetitive illumination pulse group.