Projection Lens Assembly Miniaturization via Segmented Refractive Design
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Solution Overview
Problem
Conventional projection lens assemblies face challenges in miniaturization, large field-of-view distortion, and poor imaging quality, along with the inability to accurately match a diffractive optical element for redistribution of the projection light beam.
Innovation Solution
A projection lens assembly comprising two lenses with specific refractive powers, surface types, and thermal expansion coefficients, optimized for miniaturization and high imaging quality, which can be used in conjunction with a diffractive optical element to achieve accurate light beam redistribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the number of lenses is increased to eliminate aberrations and enhance resolution, then imaging quality is improved, but the total track length of the projection lens assembly increases
Solution Approach 1:
The projection lens assembly is divided into multiple lens groups (first lens group, second lens group, third lens group) with specific configurations. Each group contains one or more lenses with defined refractive powers and surface types, allowing aberration correction and high resolution to be achieved through coordinated action of segmented components rather than a single complex lens, thereby controlling the overall track length.
Solution Approach 2:
The patent specifies precise parameter ranges for each lens including refractive power ratios (e.g., 0.3 < f1/f < 0.7), surface curvature radii (R1, R2, R3, R4), and thickness ratios (0.5 < CT1/CT2 < 1.5). By optimizing these parameters within defined ranges, the lens assembly achieves high imaging quality with corrected aberrations while maintaining a compact total track length suitable for portable devices.
2Adaptability or versatility
If the field-of-view is increased to expand application range, then versatility is improved, but distortion and imaging quality deteriorate
Solution Approach 1:
The lens assembly is segmented into multiple groups with specific functions: the first lens group (positive refractive power) handles broad field-of-view coverage, the second lens group (negative refractive power) corrects distortion at wide angles, and the third lens group (positive refractive power) maintains imaging quality at the image plane. This segmentation allows the system to achieve both large field-of-view and low distortion simultaneously.
Solution Approach 2:
The patent employs asymmetric surface designs with different curvature radii for object-side and image-side surfaces of each lens (e.g., R1 and R2 have different signs and magnitudes, R3 and R4 have different configurations). This asymmetric design allows optimal correction of field curvature and distortion while maintaining a wide field-of-view, breaking the symmetry constraint that would otherwise force a trade-off between field-of-view and imaging quality.
3Ease of manufacture
If conventional lenses are used to simplify manufacturing, then ease of manufacture is improved, but the ability to match diffractive optical element and redistribute light beam deteriorates
Solution Approach 1:
The patent combines conventional refractive lenses with a diffractive optical element (DOE) to create a hybrid optical system. The refractive lenses (made from conventional optical materials with specified thermal expansion coefficients) handle basic light focusing and steering, while the integrated DOE provides precise light beam redistribution and wavelength-selective filtering. This composite approach enables accurate depth detection and 3D imaging functionality while maintaining manufacturability through the use of standard optical materials and established fabrication techniques for both refractive and diffractive components.
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 enables high-performance, miniaturized projection lens assemblies with low temperature drift and improved imaging quality, capable of accurately redistributing the projection light beam for depth detection applications.
Implementation Method 1
a first lens having a positive refractive power, and a second lens having a positive refractive power
Implementation Method 2
match a diffractive optical element (DOE) to accurately achieve the redistribution of a projection light beam on a target object
Data Source
AI summary
The present disclosure discloses a projection lens assembly. The projection lens assembly includes, sequentially from an image-source side to an image side along an optical axis, a first lens having a positive refractive power; and a second lens having a positive refractive power. At least one of the first lens or the second lens is a glass lens. A total effective focal length f of the projection lens assembly and an effective focal length f2 of the second lens satisfy: 1<f/f2<1.5.