Zoom Lens Optical Path Folding for Compact Camera Design
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Solution Overview
Problem
Existing zoom lenses for image pickup apparatuses face challenges in achieving a compact, high zoom ratio with high resolving power over the entire zoom range while minimizing the size and thickness of the lens system, as they require significant space for lens units to move perpendicular to the optical axis, leading to increased camera width and height.
Innovation Solution
A zoom lens configuration with a specific arrangement of lens units, including a first positive refractive power unit, a second negative refractive power unit, a third positive refractive power unit, and a fifth lens unit with a reflector that bends the optical path, where the second and fourth lens units move during zooming to adjust intervals, and the fifth lens unit does not move, optimizing the optical distance between subunits to satisfy a conditional expression for compactness and high zoom ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a reflection member is placed in the front part of the lens system to reduce depth dimension, then the thickness of the image pickup apparatus is reduced, but large space is necessary in the image side of the reflection member to place multiple lens units that move for zooming in a direction perpendicular to the optical axis, causing the width dimension and height dimension of the camera to increase
Solution Approach 1:
The patent bends the optical path using a reflection member (prism) at a 90-degree angle, changing the spatial arrangement from a linear optical axis to a folded configuration. This allows the lens units to move in the optical axis direction (depth) rather than perpendicular to it, reducing the width and height dimensions while maintaining the zooming function. The optical path folding effectively transfers the zooming movement direction to another dimension.
Solution Approach 2:
Instead of moving lens units perpendicular to the optical axis as in conventional designs, the patent inverts the approach by moving lens units in the optical axis direction (longitudinally) while using a reflection member to bend the optical path. This inversion of the movement direction allows compact arrangement without increasing width and height dimensions.
2Volume of stationary object
If lens units are arranged to achieve high zoom ratio with compact size, then the lens system becomes compact, but it becomes difficult to maintain high resolving power over the entire zoom range
Solution Approach 1:
The patent divides the lens system into five distinct lens units with specific refractive power distributions (positive, negative, positive, positive, and composite). This segmentation allows each unit to be optimized for specific functions: the first unit for wide-angle performance, the second for zooming, the third and fourth for telephoto performance and aberration correction, and the fifth for fine-tuning. This segmented architecture enables high resolving power across the entire zoom range while maintaining compact size.
Solution Approach 2:
Each lens unit is assigned specific local optical properties and movement characteristics. The first lens unit has positive refractive power for wide-angle performance, the second has negative power for zooming, and the third and fourth have positive powers for telephoto performance. The fifth lens unit includes a reflection member with specific orientation. These localized optimizations ensure high resolving power is maintained at different zoom positions without compromising overall compactness.
3Adaptability or versatility
If multiple lens units move for zooming to achieve high zoom ratio, then the zoom ratio increases, but the device complexity and number of moving parts increase
Solution Approach 1:
The second lens unit with negative refractive power serves multiple functions: it enables the zooming action by moving between the first and third lens units, and it also contributes to correcting optical aberrations across the zoom range. The fifth lens unit with the reflection member not only bends the optical path for compactness but also aids in focusing and aberration correction. This multi-functionality reduces the need for additional dedicated components.
Solution Approach 2:
The patent merges the reflection member (prism) with the fifth lens unit, combining optical path bending, focusing, and aberration correction functions into a single integrated unit. This merging reduces the number of separate moving components while achieving high zoom ratio through the coordinated movement of the second and fifth lens units.
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 allows for a compact, high zoom ratio lens system with improved optical performance and reduced size, enabling efficient movement of lens units while maintaining high resolving power across the zoom range without unnecessary increases in refractive power or lens thickness.
Implementation Method 1
a reflector that bends an optical path
Data Source
AI summary
A zoom lens has, in order from an object side to an image side, a positive first lens unit, a negative second lens unit, a positive third lens unit, a positive fourth lens unit, and a fifth lens unit. In the zoom lens, the loci of the lens units moving for zooming are set appropriately, and a reflector for bending an optical path is placed at an appropriate position within the fifth lens unit.