Wide Angle Optical System Retrofocus Design Aberration Control
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Solution Overview
Problem
Designing a compact wide angle optical system for digital cameras that maintains a wide angle of view while minimizing the number of component lenses and correcting aberrations such as chromatic aberration and field curvature, while ensuring telecentricity.
Innovation Solution
A wide angle optical system comprising a first lens group with negative refractive power and a second lens group with positive refractive power, including a cemented doublet, aperture diaphragm, and biconvex lens, arranged in a retrofocus configuration to reduce Petzval sum and chromatic aberration, with specific radius curvature conditions to minimize lens length and correct distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a retrofocus type optical system with multiple component lenses is used to secure a wide angle of view and correct aberrations, then the angle of view is widened and aberrations are corrected, but the total lens length increases and the number of component lenses increases
Solution Approach 1:
The optical system is divided into two functional groups: a first lens group with negative refractive power and a second lens group with positive refractive power. This segmentation allows each group to perform specific functions (expanding angle of view vs. focusing light) efficiently, reducing the need for excessive component lenses while maintaining wide angle capability and proper focal properties.
Solution Approach 2:
The patent applies specific parameter constraints to optimize the optical system: the ratio of focal lengths (f1/f2) is controlled within 0.3-0.7, the ratio of air spaces is constrained, and the Petzval sum is limited to -0.05<f*/Σ(r1/r2)<0.05. These parameter changes enable compact design while correcting aberrations and maintaining wide angle of view.
2Manufacturing precision
If multiple component lenses are used to correct chromatic aberration and field curvature, then aberration correction is improved, but the device complexity and number of components increase
Solution Approach 1:
The patent merges multiple lens elements into cemented doublets within the second lens group. By cementing lenses together, multiple optical functions (refraction, aberration correction) are achieved in fewer discrete components, reducing overall system complexity while maintaining effective aberration correction capability.
Solution Approach 2:
The optical system uses composite lens structures including cemented doublets where lenses of different materials are bonded together. This composite approach enables simultaneous correction of chromatic and spherical aberrations through the combined optical properties of different glass materials, achieving high manufacturing precision with fewer components.
3Stability of the object's composition
If the space between the first lens group and second lens group is broadened to reduce off-axial light beam angles, then the angle between off-axial main light beams is reduced, but the total lens length increases
Solution Approach 1:
The patent controls the air space between lens groups through specific parameter ratios rather than absolute distances. By constraining the ratio of air spaces and the relationship between focal lengths (f1/f2 = 0.3-0.7), the system achieves proper off-axial light beam control in a compact configuration, avoiding excessive total lens length.
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 a compact wide angle optical system with a small number of lenses that effectively corrects various aberrations and maintains telecentricity, achieving a wide angle of view of about 60°.
Implementation Method 1
the first lens group having negative refractive power. The angle between the off axial main light beam can be reduced by the first lens group having negative refractive power
Implementation Method 2
both the chromatic aberration and the field curvature are suppressed by the two set of cemented lenses
Implementation Method 3
the exit pupil is moved away from the imaging plane by the biconvex lens at the extremity of the image side to realize a telecentric optical system
Data Source
AI summary
A wide angle optical system including a first lens group of negative refractive power and a second lens group of positive refractive power arranged in the above-mentioned order from the object side. The second lens group includes a cemented doublet SU21; an aperture diaphragm; a lens SU22; and a biconvex lens L25 arranged in the above-mentioned order from the object side, and largest ones of air spaces on the axis being front and rear spaces of the aperture diaphragm except the back focal length. The wide angle optical system is divided into the first lens group and the second lens group at the second largest air space operating as a boundary.