Despeckle Element With Optical Steps and Microlenses
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Solution Overview
Problem
Lasers emitting coherent light often produce speckle patterns due to interference, which degrade image quality in applications like laser annealing and projection displays, and existing methods for reducing speckle are either inefficient or require large, complex devices.
Innovation Solution
A despeckle element with a transparent material featuring optical steps and microlenses that split collimated light into beamlets, creating optical path differences greater than the coherence length, combined with a pulsed laser operation to broaden the wavelength bandwidth, effectively reducing speckle by minimizing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional speckle reduction methods are used, then speckle patterns are reduced, but device complexity and size increase
Solution Approach 1:
The despeckle element divides the incident collimated light beam into multiple separate beamlets through a microlens array, with each microlens forming a separate beamlet. This segmentation allows each beamlet to experience different optical path differences through the optical steps, reducing coherence and speckle patterns while maintaining a compact static structure
Solution Approach 2:
The patent introduces optical path difference in the vertical dimension (through steps of different heights) while maintaining spatial separation in the horizontal dimension (through multiple beamlets). This multi-dimensional approach to coherence reduction achieves effective speckle suppression without requiring complex mechanical components
2Reliability
If pulsed laser operation is used to broaden wavelength bandwidth, then coherence is reduced, but temporal structure becomes complex
Solution Approach 1:
The patent employs pulsed operation of the laser source to broaden the wavelength bandwidth and reduce coherence. The periodic pulsing creates temporal separation between photons, effectively reducing coherence length and minimizing interference patterns. This periodic action is combined with the static optical path difference elements to achieve enhanced speckle reduction
3Object-affected harmful factors
If optical path difference greater than coherence length is created, then interference is minimized, but device structure becomes more complex
Solution Approach 1:
The patent merges multiple functions into a single integrated despeckle element: the microlens array, optical steps, and light splitting functionality are combined in one component. This merging achieves optical path differences greater than the coherence length while minimizing interference, all within a compact static structure that avoids complex mechanical assemblies
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 significantly reduces speckle patterns, improving image quality in laser-based applications with a compact, static configuration that maintains high coherence reduction without the need for complex mechanical components.
Implementation Method 1
A height of each step of at least two of the optical steps is configured to produce an optical path difference of the collimated light longer than the coherence length
Implementation Method 2
the remaining one of the first surface and the second surface is configured to pass the collimated light separated into a plurality of beamlets corresponding to the number of microlenses
Implementation Method 3
generating a coherent light beam by a pulsed operation of a laser source with a pulse duration to broaden a wavelength bandwidth of the coherent light beam, where the pulsed operation reduces a coherence of the coherent light beam
Data Source
AI summary
Despeckle elements, laser beam homogenizers and methods for despeckling are provided. The despeckle element includes a transparent material having a first surface including a plural number of optical steps and a second surface having a plural number of microlenses. Each of the number of optical steps is in a one-to-one correspondence with at least one of the microlenses. One of the first surface and the second surface is configured to receive collimated light having a coherence length and a remaining one of the first surface and the second surface is configured to pass the collimated light separated into a plurality of beamlets corresponding to the number of microlenses. A height of each step of at least two of the optical steps is configured to produce an optical path difference of the collimated light longer than the coherence length.