Eight-Lens Photographing Optics for Compact Wide-Angle Image Quality
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Solution Overview
Problem
Conventional optical systems struggle to balance high image quality, low sensitivity, proper aperture size, miniaturization, and desirable field of view due to the scaling down of image sensor pixel size and increasing functionality requirements.
Innovation Solution
A photographing optical system comprising eight lens elements, each with specific refractive powers and surface configurations, including critical and inflection points, to correct aberrations and reduce size while maintaining image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pixel size of image sensor is scaled down to improve resolution, then image quality is improved, but sensitivity deteriorates and aperture size must be reduced
Solution Approach 1:
The optical system is divided into eight lens elements with different refractive powers and surface configurations. Each lens element is optimized to perform specific functions: positive refractive power elements for light convergence, negative refractive power elements for aberration correction, and elements with critical points for off-axis aberration control. This segmentation allows the system to maintain high image quality with small pixel sizes while compensating for reduced sensitivity through optimized light distribution.
Solution Approach 2:
Different lens elements have locally optimized properties: the first lens element has positive refractive power for light gathering, the second and fourth elements have negative refractive power for aberration correction, the fifth element has positive refractive power for focus control, and the seventh element has a convex object-side surface for off-axis light management. This local optimization of each lens element's properties enables the system to achieve high image quality and maintain sensitivity despite small aperture requirements.
2Volume of moving object
If the optical system is miniaturized to reduce device size, then device compactness is improved, but image quality and field of view deteriorate
Solution Approach 1:
The lens elements utilize curved surfaces with specific configurations: the object-side surface of the seventh lens element is convex in the paraxial region, and the image-side surface of the eighth lens element is concave in the paraxial region. These curvature configurations enable effective aberration correction within a compact form factor, maintaining image quality while minimizing system size. The aspheric surfaces allow for more efficient light path control compared to simple spherical surfaces.
Solution Approach 2:
The patent specifies precise parameter ranges for the lens elements including focal lengths (f1, f5, f7, f8), Abbe numbers (V2), and central thicknesses (CT2, CT3, CT5, CT7) that satisfy specific mathematical relationships. By optimizing these parameters within defined ranges, the system achieves miniaturization while maintaining image quality. The parameter optimization allows the optical system to fit within smaller form factors without sacrificing performance.
3Reliability
If the aperture size is reduced to improve depth of field, then depth of field is improved, but light gathering ability and image quality deteriorate
Solution Approach 1:
The patent converts the limitation of small aperture into a benefit by strategically placing critical points on lens surfaces in off-axis regions. The seventh lens element's convex object-side surface and the eighth lens element's concave image-side surface are configured to create critical points that redirect off-axis light effectively. This transformation allows the system to achieve desirable depth of field with small aperture while maintaining light gathering ability through optimized light path management.
Solution Approach 2:
The optical system uses a composite arrangement of eight lens elements with different material properties (indicated by different Abbe numbers and refractive powers). This composite structure enables the system to maintain high light gathering ability despite reduced aperture size by distributing optical functions across multiple elements with complementary properties, effectively compensating for the reduced light input.
4Measurement precision
If multiple lens elements are added to correct aberrations and improve image quality, then image quality is improved, but device complexity and size increase
Solution Approach 1:
Each lens element in the eight-element system is designed to perform multiple functions simultaneously. For example, the first lens element with positive refractive power contributes to both light gathering and initial aberration correction. The seventh lens element with convex object-side surface addresses both off-axis aberrations and light path optimization. This multi-functionality reduces the need for additional specialized elements, maintaining image quality while controlling system complexity.
Solution Approach 2:
The use of aspheric surfaces with critical points on lens elements provides enhanced aberration correction capability compared to simple spherical surfaces. The convex object-side surface of the seventh element and the concave image-side surface of the eighth element create critical points that efficiently correct off-axis aberrations. This advanced surface geometry allows fewer elements to achieve the same correction level that would require more simple spherical elements, thereby reducing overall system complexity.
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 achieves a balance among high image quality, low sensitivity, appropriate aperture size, miniaturization, and wide field of view by optimizing lens element configurations and materials, enhancing peripheral illuminance and correcting aberrations.
Implementation Method 1
The first lens element has positive refractive power. The fifth lens element has positive refractive power. The object-side surface of the seventh lens element is convex in a paraxial region thereof. The image-side surface of the eighth lens element is concave in a paraxial region thereof.
Data Source
AI summary
A photographing optical system includes eight lens elements which are, in order from an object side to an image side: a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element, a sixth lens element, a seventh lens element and an eighth lens element. The eight lens elements each have an object-side surface facing toward the object side and an image-side surface facing toward the image side. The first lens element has positive refractive power. The fifth lens element has positive refractive power. The object-side surface of the seventh lens element is convex in a paraxial region thereof. The image-side surface of the eighth lens element is concave in a paraxial region thereof. At least one lens surface of at least one lens element of the photographing optical system has at least one critical point in an off-axis region thereof.