Incoherence Device for Laser Speckle Reduction

The patent divides the laser beam into multiple separate beams using a beam splitter with multiple reflection surfaces. Each beam travels through a different optical path, and by setting the optical path differences to be larger than the coherence length, the beams become mutually incoherent. This segmentation of the original coherent beam into multiple incoherent beams reduces speckle noise while maintaining high brightness.

The patent introduces a temporal dimension by creating multiple beams with different optical path lengths. The beam splitter design causes light to be reflected and transmitted multiple times, creating beams that emerge at different times and with different path lengths. This dimensional approach ensures that the optical path difference exceeds the coherence length, making the beams incoherent and reducing speckle.

The patent replaces mechanical rotation or electrical actuation with a passive optical system. Instead of mechanically rotating elements or electrically controlling liquid crystal, the invention uses a beam splitter with carefully designed reflection surfaces that passively create multiple incoherent beams through optical path differences. This eliminates the need for motors, actuators, or power supplies, significantly reducing device complexity and enabling miniaturization.

The optical system is designed to automatically generate incoherent beams through the inherent properties of the beam splitter and optical paths. The system does not require external control or actuation; the beam splitting and path differentiation occur automatically based on the optical design, making the system self-sufficient and eliminating complex control mechanisms.

The patent applies different optical properties to different regions of the beam splitter. The first reflection surface has high reflectivity for creating strong reflected beams, while the second reflection surface has lower reflectivity to allow partial transmission. This local variation in optical properties optimizes the intensity distribution of output beams, ensuring symmetrical and efficient light utilization while maintaining compact dimensions.

The patent carefully controls the optical path differences between multiple beams by adjusting the geometry and positioning of reflection surfaces. By setting specific path differences larger than the coherence length, the system achieves incoherence while optimizing light efficiency. The parameters of the beam splitter (reflectivities, angles, positions) are tuned to produce symmetrical intensity distribution and maximize light utilization.