Compact Imaging Lens Design with Inverted Refractive Power Groups
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Solution Overview
Problem
Existing digital camera imaging lenses face challenges in achieving a balance between compactness, high performance, and wide-angle capabilities with a half-field angle of 28-36°, large aperture (F-number less than 2.8), and a small number of lenses, while maintaining resolution for 10-20 million pixel imaging elements, without increasing the overall length and cost.
Innovation Solution
The design incorporates a six-lens configuration with a first lens group having positive refractive power and a second lens group with negative refractive power, featuring a wide air space between them, including specific lens types and arrangements to optimize refractive power balance, reduce field curvature, and correct aberrations, allowing for downsizing and high performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a retrofocus type lens is used to move the exit pupil position away from the image face, then peripheral light beam can be entered onto the sensor at an angle close to the perpendicular, but the entire length of the lens increases
Solution Approach 1:
Instead of using a retrofocus type lens with a negative lens group on the object side, the patent inverts the arrangement by placing a positive lens group on the object side and a negative lens group on the image side. This inversion allows the exit pupil to be positioned closer to the image face while still achieving perpendicular incidence of peripheral light beams on the sensor.
Solution Approach 2:
The patent changes the refractive power parameters of the lens groups, using a positive lens group with higher refractive power on the object side and a negative lens group with lower refractive power on the image side. This parameter change allows for a more compact lens length while maintaining the ability to handle peripheral light beams at perpendicular angles.
2Length of stationary object
If a telephoto type lens with negative lens group on image side is used, then the entire length is reduced, but the number of lenses increases and cost rises
Solution Approach 1:
The patent merges the functions of multiple lens groups into a more integrated structure. The positive lens group on the object side combines focusing and peripheral light management functions, while the negative lens group on the image side handles field curvature and chromatic aberration correction. This merging reduces the total number of discrete lens elements compared to conventional telephoto designs.
3Illumination intensity
If a lens with large aperture F-number less than 2.8 is used, then differentiation from general compact camera is achieved, but the lens size and complexity increase
Solution Approach 1:
The patent applies different optical characteristics to different parts of the lens system. The positive lens group on the object side is optimized for handling high-angle peripheral light beams, while the negative lens group on the image side is optimized for correcting aberrations introduced by the large aperture. This local optimization allows for a large aperture without proportionally increasing overall lens 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
This configuration effectively reduces the size and cost of the imaging lens, maintains high performance, and corrects aberrations, making it suitable for digital cameras with wide angles and large apertures, while ensuring a compact and efficient design.
Implementation Method 1
a first lens group having a positive refractive power; and a second lens group having a negative refractive power
Data Source
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Figure 5
AI summary
An imaging lens includes in order from an obj ect side a first lens group including a positive refractive power and a second lens group having a negative refractive power, the first lens group and the second lens group including a widest air space therebetween, the first lens group including in order from the object side a negative first lens having a concave face on the object side, a positive second lens having a convex face on both sides, an aperture stop, a negative third lens having a concave face on the object side, a positive fourth lens having a convex face on an image side and a positive fifth lens having a convex face on the image side, and the second lens group including a negative meniscus sixth lens having a concave face on the object side.