Zoom Lens Optical Path Folding for Compact High Zoom Ratio
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Solution Overview
Problem
Existing zoom lenses face challenges in achieving a high zoom ratio while maintaining image quality and durability, with previous designs either being too large, costly, or suffering from low transmittance due to the use of high-refractive index materials that are not practically available.
Innovation Solution
A zoom lens configuration with six lens groups, including a first and sixth lens group fixed during zooming, and the second, fourth, and fifth lens groups moving along the optical axis, utilizing an optical-path bending member to fold the optical axis approximately 90 degrees, and incorporating aspheric surfaces to reduce aberrations and maintain image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a right-angle prism with high-refractive index material is used to bend the optical path, then the optical system length is shortened, but the transmittance on the short wavelength side lowers and the cost increases
Solution Approach 1:
The patent changes the refractive index parameter of the optical-path bending member from conventional high values (>1.8) to a lower range (1.6-1.75), which maintains the optical path folding function while improving transmittance characteristics and reducing material cost
Solution Approach 2:
The patent uses a composite lens structure combining materials with different refractive indices and dispersion properties, including the optical-path bending member made of specific glass materials that balance refraction and transmittance requirements
2Length of moving object
If a right-angle prism with high-refractive index material is used to bend the optical path, then the optical system length is shortened, but a reflecting coat becomes necessary which increases cost
Solution Approach 1:
By adjusting the refractive index parameter to an optimal range (1.6-1.75), the patent achieves sufficient total internal reflection without requiring additional reflecting coats, thereby simplifying manufacturing and reducing cost
3Productivity
If the first lens group is made large to achieve high zoom ratio and bright F value, then the zooming performance is improved, but the overall size of the zoom lens increases
Solution Approach 1:
The patent introduces an optical-path folding structure that bends the optical axis by approximately 90 degrees, changing the spatial arrangement from a straight-line configuration to a folded path, thereby achieving high zoom ratio in a compact form factor
Solution Approach 2:
The optical-path bending member serves multiple functions: it folds the optical path to shorten system length, acts as a lens element contributing to zooming, and helps control aberrations, thereby achieving high zoom ratio without proportionally increasing 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
The solution achieves a high zoom ratio with small size and low cost, ensuring high image performance and correcting various aberrations, while maintaining a compact configuration and reducing the need for high-refractive index materials.
Implementation Method 1
a right-angle prism is placed in the first lens group for bending the optical path approximately 90° at midpoint
Implementation Method 2
a refractive optical system, thereby shortening the length of the optical system
Data Source
AI summary
A zoom lens for capturing images that enhances the image aberration correction rate to achieve high resolution and zooming ratio. The zoom lens includes, in sequence from an object side to an image side, a first lens group with positive refraction power, a second lens group with negative refraction power, a third lens group with positive refraction power, a fourth lens group with positive refraction power, a fifth lens group with positive refraction power and a sixth lens group with positive refraction power. The positions of first and sixth lens groups are fixed during photographing. When the zoom lens is made to zoom from a wide-angle end to a telephoto end thereof, the second lens group moves toward the image side while the fourth and fifth lens groups move toward the object side. In addition, the zoom lens has a reflection element so as to fold the image light entering thereof.