Projection Lens Thermal Stability via Segmented Glass Design
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Solution Overview
Problem
Existing projection lenses for 3D structured light technology in handheld devices suffer from significant changes in focal length and image distortion due to ambient temperature fluctuations, affecting the accuracy and definition of three-dimensional imaging.
Innovation Solution
A projection lens design comprising three lenses with specific refractive powers and materials, including a first lens with positive refractive power, a second lens with negative refractive power made of glass, and a third lens with positive refractive power, optimized to maintain optical stability and reduce system length, with aspheric surfaces to correct aberrations and improve thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a conventional projection lens is used, then the system length is longer, but the thermal stability and focal length consistency deteriorate
Solution Approach 1:
The projection lens is divided into three separate lens elements (first lens with positive refractive power, second lens with negative refractive power, third lens with positive refractive power). Each lens element can be independently optimized for thermal stability while maintaining compact overall dimensions. This segmentation allows for better control of thermal expansion effects on focal length.
Solution Approach 2:
The patent employs different glass materials with specific refractive indices and Abbe numbers for each lens element. The second lens uses glass with higher refractive index (1.7≤n2≤2.2) and specific Abbe number (40≤v2≤55) to compensate for thermal effects. This composite material approach enables thermal compensation while maintaining compact form factor.
2Reliability
If the focal length changes with temperature, then the projection angle changes, but the measurement precision and contour restoration accuracy deteriorate
Solution Approach 1:
The patent specifies precise parameter ranges for each lens element to maintain optical performance stability across temperature variations. The focal length ratio constraints (0.30≤f1/f≤0.41, -0.20≤f2/f≤0.00, 0.55≤f3/f≤0.85) and refractive index specifications ensure that the overall focal length remains stable, thereby maintaining consistent projection angle and measurement precision.
Solution Approach 2:
The patent replaces mechanical adjustment mechanisms with an optically passive thermal compensation design. Instead of using movable parts to adjust focal length with temperature, the system uses the inherent thermal properties of different glass materials to automatically compensate for focal length changes, ensuring measurement precision without mechanical complexity.
3Adaptability or versatility
If the projected image point becomes larger with temperature changes, then the system adaptability decreases, but the definition and imaging quality deteriorate
Solution Approach 1:
The patent designs the lens system to dynamically adapt to temperature changes while maintaining image quality. The specific arrangement of positive-negative-positive lens elements with controlled focal length ratios allows the system to automatically compensate for thermal expansion effects, keeping the projected image point size consistent across different temperatures and preserving imaging definition.
Solution Approach 2:
Each lens element is designed with specific local optical properties (refractive index, Abbe number, focal length) to address local thermal effects. The second lens with negative power and specific glass properties (1.7≤n2≤2.2, 40≤v2≤55) is positioned to locally compensate for thermal expansion effects on the overall image point size, maintaining imaging definition across temperature ranges.
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 design effectively reduces system length, maintains optical performance across temperature changes, and enhances the precision and definition of three-dimensional imaging in handheld devices.
Implementation Method 1
a first lens L1 having positive refractive power
Implementation Method 2
a second lens L2 having negative refractive power
Implementation Method 3
a third lens L3 having positive refractive power
Implementation Method 4
with aspheric surfaces to correct aberrations
Data Source
AI summary
A projection lens is disclosed. The projection lens includes, in sequence from an object side to an image side: an object surface, a first lens having positive refractive power, a second lens having negative refractive power, and a third lens having positive refractive power, where a focal length of the entire projection lens is f, a total optical length of the projection lens is TTL, a refractive index of the second lens is n2, a refractive index of the third lens is n3, and the following conditions are satisfied: 1.7≤n2≤2.2; 1.7≤n3≤2.2; and 1.25≤f/TTL≤2.20. The projection lens can effectively reduce the system length, and has good performance stability at different temperatures.