Catadioptric Lens Thickness Reduction via Mirror Integration
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Solution Overview
Problem
Conventional camera modules in mobile terminals face challenges in miniaturization due to the need for increased thickness to achieve bright and high-telescopic performance, and catadioptric optical systems with two reflective mirrors suffer from assembly tolerance issues and external impact-induced performance degradation.
Innovation Solution
An imaging lens design that locates all lenses within a catadioptric lens with two mirror surfaces, where the second mirror surface has a larger transmission area than the first, and a stop surface is placed on the object side of the first lens, reducing thickness and assembly tolerance while enhancing brightness and resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the diameter of incident light is increased to improve brightness, then the brightness Fno increases, but the thickness of the mobile terminal must increase in proportion
Solution Approach 1:
The patent employs a periscope-type optical path where light travels horizontally through the lens module and then reflects at 90 degrees to reach the sensor vertically. This dimensional change allows the incident light diameter to be increased without proportionally increasing the terminal thickness, as the light path extends in the horizontal dimension rather than the vertical dimension.
Solution Approach 2:
The optical system is divided into distinct functional segments: the incident light path through the lens, the reflection path at the prism, and the final path to the sensor. This segmentation allows independent optimization of each segment, enabling the incident light diameter to be increased in the lens portion without directly increasing the overall thickness.
2Speed
If a catadioptric optical system with two reflective mirrors is used to achieve long focal length, then the focal length increases, but the overall length compared to diameter becomes very long
Solution Approach 1:
The patent combines refractive elements (lenses) with reflective elements (prism with mirror surfaces) into a single integrated catadioptric optical system. This merging allows the system to achieve long focal length through the combined optical power of both lens and mirror, while the compact periscope arrangement keeps the overall length-to-diameter ratio manageable.
3Ease of manufacture
If two reflective mirrors are assembled separately to form a catadioptric system, then the system can be constructed, but assembly tolerance degrades optical performance
Solution Approach 1:
The patent integrates the mirror surfaces directly onto the prism structure, forming a single monolithic component rather than assembling separate mirrors. This merging eliminates the alignment tolerances required between separate mirror components and the prism, significantly improving manufacturing precision while maintaining constructibility through standard prism fabrication processes.
4Ease of operation
If two reflective mirrors are spaced apart in a catadioptric system, then the optical path is formed, but external impact distorts the reflective mirror from its original position
Solution Approach 1:
The patent integrates the mirror surfaces as integral parts of the prism structure, eliminating the need for spaced-apart separate mirror components. This integration ensures that the mirrors cannot be displaced by external impacts, as they are rigidly fixed within the prism's structural framework, thereby improving reliability while maintaining the required optical path.
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 suppresses lens thickness increase, reduces assembly tolerance, minimizes external impact-induced performance deterioration, and increases brightness and resolution by optimizing the entrance pupil diameter and lens group configuration.
Implementation Method 1
a second mirror surface which is formed concave toward the object side, and reflects the light incident on the incident surface to a first mirror surface in the object side
Implementation Method 2
the first mirror surface which is formed, at a central portion of the incident surface, convex toward an image side, and reflects the light reflected from the second mirror surface toward the image side
Implementation Method 3
a lens group including a plurality of lenses for transmitting the light emitted from the catadioptric lens to an image surface
Data Source
AI summary
The present disclosure relates to an imaging lens, a camera module and an electronic device including the same. The imaging lens according to an embodiment of the present disclosure includes a catadioptric lens on which light is incident from an object side, and through which light is reflected and emitted from the inside; and a lens group including a plurality of lenses for transmitting the light emitted from the catadioptric lens to an image surface, wherein the catadioptric lens includes: an incident surface on which light is incident from the object side; a second mirror surface which is formed concave toward the object side, and reflects the light incident on the incident surface to a first mirror surface in the object side; the first mirror surface which is formed, at a central portion of the incident surface, convex toward an image side, and reflects the light reflected from the second mirror surface toward the image side; and an exit surface through which the light reflected from the first mirror surface is emitted, wherein all of the lens group is disposed between the first mirror surface and the second mirror surface based on an optical axis. Accordingly, it is possible to increase the brightness of the lens, increase resolution, suppress an increase in thickness, and reduce tolerance due to mirror assembly.