Mirror Objective Imaging Aperture for Miniature Laser Projectors
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Solution Overview
Problem
Miniature laser projectors face challenges in achieving high image quality and brightness due to the mismatch between the etendue of the laser beam and the projection system, leading to distorted and low-resolution images, with existing solutions requiring complex optics that are not suitable for compact designs.
Innovation Solution
A projector design incorporating a mirror objective with at least two mirror elements to image the deflection unit's aperture onto the projection surface, allowing for a beam waist placement that prevents light loss and maintains image quality, with a focus on cost-effective and compact construction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the laser bundle is focused onto the aperture of the deflection unit to maximize image brightness, then brightness is improved, but the spot size on the projection surface becomes significantly larger than the nominal pixel size, greatly impairing resolution
Solution Approach 1:
An imaging device is introduced as an intermediary component between the deflection unit and the projection surface. This imaging device includes an objective lens and a field lens that work together to transform the laser bundle, enabling the beam waist to be positioned at the projection surface while maintaining both brightness and resolution. The imaging device mediates the contradiction by providing optical transformation that decouples the focus position from the beam waist position.
Solution Approach 2:
The patent applies parameter changes by adjusting the optical parameters of the imaging system, specifically the focal lengths of the objective lens and field lens. By optimizing these parameters, the system achieves the desired balance between brightness and resolution. The objective lens has a focal length f1 and the field lens has a focal length f2, where their ratio and absolute values are optimized to achieve the correct beam waist positioning and spot size control.
2Manufacturing precision
If the beam waist is placed onto the projection surface to minimize spot size, then resolution is improved, but light losses occur because the extent of the laser bundle on the scanner mirror becomes larger than the area thereof
Solution Approach 1:
The imaging device acts as an intermediary that enables the beam waist to be positioned at the projection surface while preventing light loss at the deflection unit. The objective lens and field lens configuration allows the laser bundle to be properly sized at the scanner mirror aperture, preventing excessive beam extent and associated light losses while maintaining a small spot size at the projection surface.
3Loss of energy
If the beam waist is placed between the deflection unit and the projection surface as a compromise, then some light loss is avoided, but the image is distorted and has a pincushion form
Solution Approach 1:
The imaging device with its specifically designed objective lens and field lens serves as an intermediary that eliminates image distortion while preventing light loss. The optical configuration transforms the laser bundle in a way that maintains a uniform beam profile throughout the optical path, preventing the pincushion distortion that occurs when the beam waist is placed elsewhere in the optical path.
4Manufacturing precision
If an objective with a large number of individual lenses is used to correct distortion and avoid chromatic aberrations, then image quality is improved, but the device complexity increases, making it unsuitable for miniature projectors
Solution Approach 1:
The patent merges the functions of multiple optical elements into a more compact configuration. Instead of using a large number of individual lenses to correct distortion and chromatic aberrations, the invention employs a specific combination of an objective lens and a field lens that achieves the same optical corrections in a more compact arrangement, suitable for miniature projectors.
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 achieves a distortion-free image with improved resolution and brightness, maintaining a large depth of field without the need for refocusing, suitable for miniature projectors with realistic projection distances.
Implementation Method 1
an imaging device for imaging an aperture of the deflection unit onto the projection surface
Data Source
AI summary
A projector for projecting an image includes: a light source for generating a light bundle; a pivotable deflection unit for deflecting the light bundle generated by the light source onto a projection surface; and an imaging device for imaging an aperture of the deflection unit onto the projection surface. The imaging device includes a mirror objective having at least two mirror elements. A method for projecting an image is also provided.