Three-Lens Image Optical System Compactness
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Solution Overview
Problem
The challenge is to create a compact and cost-effective image-taking optical system for digital cameras that maintains high optical performance, particularly for solid-state image pickup elements, while minimizing manufacturing errors and avoiding issues with exit pupil position and beam angles.
Innovation Solution
The solution involves a three-lens image-taking optical system with a positive first lens having a convex surface on the object side, a positive second lens with a convex surface on the image side, and a negative third lens with a concave surface on the image side, adhering to specific focal length ratios to optimize compactness and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the size of the image-taking optical system is reduced while keeping the solid-state image pickup element size constant, then the system becomes more compact, but the exit pupil position comes close to the image surface causing poor light converging performance and luminance unevenness
Solution Approach 1:
The optical system is divided into three separate lenses with specific power distributions. The first lens has positive power for light gathering, the second lens has negative power for beam angle control, and the third lens has positive power for final focusing. This segmentation allows independent optimization of each lens function to achieve compactness without sacrificing optical performance.
Solution Approach 2:
The patent applies specific conditional expressions to control the focal lengths of the lenses: 0.711 < f1/f2 and -1.162 < f2/f3. By precisely controlling these parameter ratios, the system achieves the optimal balance between compact size and exit pupil position, ensuring proper light converging performance without requiring a large system volume.
2Volume of moving object
If a three-lens configuration with strong negative power second lens is used, then the system can be compact, but manufacturing error sensitivity to lens axis becomes extremely high making it difficult to maintain periphery performance
Solution Approach 1:
The patent modifies the focal length parameters to satisfy 0.711 < f1/f2 and -1.162 < f2/f3. These parameter adjustments reduce the negative power of the second lens from being excessively strong, thereby reducing sensitivity to manufacturing errors in lens axis alignment while still maintaining the compactness of the three-lens configuration.
3Volume of moving object
If a negative meniscus lens with convex surface on object side is used as the second lens, then the system can be compact, but the beam angle inputted to the second lens on the image surface side becomes too steep causing total reflection
Solution Approach 1:
The patent controls the focal length ratio f2/f3 to be greater than -1.162, which regulates the beam angle transformation through the second lens. This parameter control ensures that the beam angle incident on the image surface side of the second lens does not become too steep, preventing total internal reflection while maintaining compact system size.
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
This configuration achieves a balanced optical performance, reduces manufacturing errors, and maintains high image quality across the image area, making the system suitable for compact digital devices while being cost-effective.
Implementation Method 1
an image-taking optical system to form an image in a solid-state image pickup element comprises an aperture stop, and three lenses
Data Source
AI summary
There is provided an image-taking optical system to form an image in a solid-state image pickup element. The image-taking optical system comprises an aperture stop, a positive first lens having a convex surface on an object side, a positive second lens having a convex surface on an image side, and a negative third lens L3 having a concave surface on the image side provided in this order from the object side. In addition, a conditional expression: 0.71<f1/f2<1.1 (f1: focal length of the first lens, and f2: focal length of the second lens) is satisfied.