Compact Macro Optical System with Exit Pupil Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing macro lenses face challenges in achieving a larger aperture and higher imaging magnification while maintaining a small overall size, as evidenced by the limitations in optical systems disclosed in JP 2021-39304 A and JP 2020-60661 A.
Innovation Solution
An optical system with multiple lens groups that change intervals between adjacent lens groups during focusing, adhering to specific conditional expressions to maintain a small size and high performance, including an aperture stop, and employing focusing methods like inner focus and floating focus to minimize aberration variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the weight and movement amount of the focus group are increased to achieve a large aperture ratio (F 2.0), then the aperture is improved, but the size of the macro lens increases and focus speed deteriorates
Solution Approach 1:
The optical system divides the lens into multiple lens groups (first through fifth lens groups) with different functions. The focus group is segmented as a separate movable unit containing specific lens groups (second and fourth lens groups in the embodiment), allowing independent movement for focusing while keeping other lens groups stationary. This segmentation enables the focus group to be optimized for minimal movement mass without compromising overall aperture performance.
Solution Approach 2:
The patent implements dynamic focusing by moving specific lens groups (focus group) along the optical axis while keeping other lens groups stationary. The conditional expressions define the dynamic range of movement for the exit pupil position during focusing, ensuring that the focus group moves only the necessary amount to achieve high imaging magnification without excessive movement that would increase size and weight.
2Area of stationary object
If strong positive refractive power is provided in the third lens group to reduce the diameter of the fourth lens group, then the lens diameter is reduced, but the number of lenses must be increased to correct aberrations, making the optical system larger
Solution Approach 1:
The patent assigns specific refractive power characteristics to different lens groups based on their local functions. The third lens group is given strong positive refractive power specifically to reduce the diameter of subsequent lens groups, while the fourth lens group (negative refractive power) and fifth lens group (positive refractive power) are optimized for aberration correction. This local optimization of refractive power distribution allows diameter reduction without proportionally increasing the total number of lenses.
Solution Approach 2:
The patent carefully controls the refractive power parameters of each lens group within specific ranges. The third lens group's strong positive refractive power is balanced by adjusting the refractive power of the fourth and fifth lens groups, allowing diameter reduction while maintaining aberration correction performance through parameter optimization rather than simply adding more lenses.
3Adaptability or versatility
If the exit pupil position varies significantly during focusing, then the focusing range is improved, but the number of lenses required for aberration correction increases, enlarging the optical system
Solution Approach 1:
The patent pre-determines the exit pupil position at key focusing states (infinite distance, first short distance with magnification β1, and second short distance with magnification β2) and establishes conditional expressions that limit the variation within specific ranges. This preliminary positioning strategy ensures that the exit pupil remains within acceptable bounds throughout the focusing range, reducing the need for additional lenses to correct aberrations caused by excessive exit pupil movement.
Solution Approach 2:
The patent replaces complex mechanical aberration correction mechanisms (additional lenses and groups) with an optimized optical design that inherently controls exit pupil position variation. By carefully designing the refractive power distribution and movement characteristics of the lens groups, the system achieves acceptable aberration control through optical geometry rather than mechanical addition of corrective elements.
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 an optical system with a larger aperture and higher imaging magnification while keeping the overall size small, facilitating high-speed autofocus and reducing the number of lenses required for aberration correction.
Implementation Method 1
an optical system including a plurality of lens groups in which an interval between adjacent lens groups changes when focusing
Implementation Method 2
and an aperture stop
Data Source
AI summary
The optical system includes a plurality of lens groups in which an interval between adjacent lens groups changes when focusing, and an aperture stop, and when intervals between an exit pupil of an on-axis ray by the aperture stop and an image plane in an infinite-distance object focusing state, a first short-distance object focusing state in which an imaging magnification is β1, and a second short-distance object focusing state in which an imaging magnification is β2 are Pinf, P1, and P2, respectively, the optical system satisfies predetermined conditions. An imaging apparatus includes the optical system and an image sensor.