Ultra-short-focus Projection Optical System with Aspherical Reflector
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Solution Overview
Problem
Current ultra-short-focus projection lenses cannot simultaneously achieve a short overall length and a high projection ratio while supporting 4K resolution, as they require increased back focal length to accommodate an oscillating mirror for pixel conversion, leading to compromised resolution and projection ratio.
Innovation Solution
An ultra-small-sized 4K-resolution ultra-short-focus projection optical system with a refraction lens assembly and an aspherical reflector, where the focal power is distributed to achieve a projection ratio less than 0.21 and an overall optical length of less than 202 mm, incorporating a 4K oscillating mirror and a DMD chip with a deviated optical axis to maintain high resolution and reduce semi-aperture size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an oscillating mirror is added to convert 1 pixel into 4 pixels to achieve 4K resolution, then resolution is improved, but back focal length increases substantially
Solution Approach 1:
The patent merges the oscillating mirror function directly into the lens assembly structure, integrating it with the refraction lens groups and aspherical reflector. This integration allows the 4K pixel conversion function to be achieved without substantially increasing the back focal length, as the oscillating mirror is incorporated within the existing optical path rather than adding a separate space-consuming component.
Solution Approach 2:
The oscillating mirror is nested within the lens assembly structure, positioned between the refraction lens groups and the aspherical reflector. This nesting approach allows the oscillating mirror to be housed within the existing optical system boundaries, avoiding substantial increases in overall length while still providing the 4K resolution enhancement through periodic vibration.
2Length of stationary object
If the overall length of ultra-short-focus projection lenses is reduced below 250 mm, then compactness is improved, but projection ratio is sacrificed
Solution Approach 1:
The patent employs aspherical reflector surfaces with specifically designed curvature parameters and refraction lens groups with optimized focal lengths to achieve a projection ratio of 0.209 within an overall length of 201.8 mm. By carefully controlling and optimizing these optical parameters, the system maintains high adaptability for ultra-short-focus applications while achieving compact dimensions.
Solution Approach 2:
The patent uses a composite optical system combining refraction lens groups (with specific refractive indices and dispersion properties) and an aspherical reflector. This composite structure allows the system to achieve both compact size and high projection ratio performance by leveraging the complementary strengths of refractive and reflective optical elements.
3Ease of manufacture
If the semi-aperture size of the reflector is reduced to reduce assembling sensitivity, then manufacturing ease is improved, but optical performance may be compromised
Solution Approach 1:
The patent applies aspherical surface profiles to the reflector with locally optimized curvature distributions. This allows the reflector to maintain precise optical performance in critical zones while having a reduced overall semi-aperture size, thereby lowering assembling sensitivity without compromising image quality. The aspherical design concentrates the required optical correction in specific local regions rather than requiring large aperture precision across the entire surface.
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 system maintains high 4K resolution, reduces assembly sensitivity, and allows for batch production, while compensating for conjugate distance variations and correcting field curvatures and distortions across different projection distances, ensuring consistent resolution and a clear image.
Implementation Method 1
an aspherical reflector
Implementation Method 2
a refraction lens assembly
Implementation Method 3
it needs to add an oscillating mirror between a lens and a lighting chip to convert 1 pixel into 4 pixels through a periodic vibration mode of the oscillating mirror
Data Source
AI summary
The present invention discloses an ultra-small-sized 4K-resolution ultra-short-focus projection optical system, which is characterized by including in sequence in a projection direction: a DMD chip, an equivalent prism, a 4K oscillating mirror, a refraction lens assembly and an aspherical reflector. Through reasonable distribution of focal power, the semi-aperture size of the reflector is reduced to be less than 50 mm, and the assembling sensitivity is substantially reduced, so that batch production can be realized.