VCSEL Laser Projection Imaging With Microlens Spot Homogenization
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Solution Overview
Problem
Conventional laser projection imaging devices using edge-emitting lasers (EEL) suffer from low beam utilization, complex optical path structures, and speckle noise due to high coherence, which hinder miniaturization and increase costs.
Innovation Solution
Employing vertical-cavity surface-emitting lasers (VCSEL) as light sources, eliminating the need for a spatial light modulator like DMD, and utilizing a microlens array and imaging lens to homogenize and project light beams, resulting in a compact, high-efficiency, and speckle-reduced imaging device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If edge-emitting lasers (EEL) are used as light sources, then laser projection imaging can be achieved, but beam utilization is low and device complexity increases
Solution Approach 1:
The patent changes the emission direction parameter of the laser from edge-emitting (EEL) to vertical-cavity surface-emitting (VCSEL). This parameter change fundamentally improves beam utilization because VCSELs emit light perpendicular to the substrate surface, allowing direct coupling with imaging lenses without requiring complex spatial light modulators like DMD, thereby simplifying the optical path structure while maximizing beam utilization
Solution Approach 2:
The patent extracts and eliminates the DMD (digital micro-mirror device) component from the optical path by using VCSELs instead of EELs. Since VCSELs can be directly imaged through lenses, the complex spatial light modulation function of DMD becomes unnecessary, removing this component and its associated complexity from the system
2Ease of operation
If DMD is used for spatial light modulation, then image projection is achieved, but beam utilization decreases
Solution Approach 1:
The patent removes the DMD component from the system by using VCSELs that can be directly imaged. The VCSEL array itself serves as the light source that can be optically addressed and imaged directly onto the target plane, eliminating the need for DMD and its associated beam losses from reflection and scattering
Solution Approach 2:
The patent uses optical addressing to create a light pattern copy of the desired image directly from the VCSEL array. By optically addressing specific regions of the VCSEL array and imaging them directly, the system creates a direct optical copy of the image without requiring physical manipulation by DMD, thereby maintaining beam utilization
3Power
If EEL with high coherence is used, then laser light is produced, but speckle noise increases
Solution Approach 1:
The patent segments the laser source into multiple independent VCSEL elements arranged in an array. Each VCSEL element acts as an independent coherent source with slightly different phase and wavelength characteristics. When these segmented sources are combined, their individual speckle patterns interfere incoherently, averaging out the speckle noise while maintaining high laser output power
Solution Approach 2:
The patent changes the coherence parameters of the laser system by using multiple VCSELs with different wavelengths and phases. The multi-wavelength and multi-phase characteristics of the VCSEL array reduce temporal and spatial coherence, thereby suppressing speckle noise while maintaining high power output through the combined emission of all array elements
4Loss of energy
If VCSEL array is used, then beam utilization improves, but manufacturing complexity increases
Solution Approach 1:
The patent merges multiple VCSEL elements into a single integrated array structure on one chip. By combining fabrication techniques for individual VCSELs with array integration methods, the system achieves high beam utilization through the VCSEL array while managing manufacturing complexity through standardized processes and monolithic integration
Solution Approach 2:
The VCSEL array structure serves multiple functions simultaneously: it provides high beam utilization through vertical emission, enables direct imaging without DMD, reduces speckle through multi-element incoherent combination, and can be manufactured using standardized semiconductor processes. This multi-functionality reduces overall system complexity despite the advanced nature of the array fabrication
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
Improves beam utilization, reduces device volume, and enhances image quality by minimizing speckle noise while maintaining high brightness and cost-effectiveness.
Implementation Method 1
the light-emitting units include a first light-emitting unit for emitting red laser light, a second light-emitting unit for emitting green laser light, and a third light-emitting unit for emitting blue laser light
Implementation Method 2
the light-emitting module includes a plurality of light-emitting units made of vertical-cavity surface-emitting lasers
Implementation Method 3
a microlens array, located on a light-emitting side of the light source chip, and configured to homogenize light spots of the light-emitting modules
Implementation Method 4
an imaging lens, located on a side of the microlens array facing away from the light source chip along a light beam propagation direction, and configured to receive light beams after passing through the microlens array and project the light beams into an image
Data Source
AI summary
A laser projection imaging device, comprising: a light source chip, comprising a drive circuit and light-emitting modules; wherein: a microlens array, located on a light-emitting side of the light source chip, and configured to homogenize light spots of the light-emitting modules; and an imaging lens, located on a side of the microlens array facing away from the light source chip along a light beam propagation direction, and configured to receive light beams after passing through the microlens array and project the light beams into an image.