Diffractive Optical Element and Meniscus Lens for Compact Imaging
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Solution Overview
Problem
Existing optical systems face challenges in achieving a balance between reducing size and weight while maintaining excellent optical performance and minimizing changes in focusing, particularly in inner focus systems with a small number of lenses, where chromatic aberration correction is difficult.
Innovation Solution
The optical system comprises a first lens unit with a diffractive optical element and a negative meniscus lens, a second lens unit with positive power, and a third lens unit with negative power, arranged from object to image side, where the second lens unit moves during focusing, reducing the height variation of the light flux and correcting aberrations through the diffractive optical element's positive power and negative lens's meniscus shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the number of lenses is reduced to downsize and reduce weight of the optical system, then the size and weight are reduced, but it becomes difficult to sufficiently correct aberration in the first lens unit
Solution Approach 1:
The patent introduces a diffractive optical element with positive power into the first lens unit, fundamentally changing the optical parameters and aberration correction capabilities. This allows the first lens unit to achieve sufficient aberration correction despite the reduced number of lenses, resolving the contradiction between downsizing and maintaining optical performance.
Solution Approach 2:
The patent combines a diffractive optical element with a negative meniscus lens in the first lens unit, creating a composite optical structure. This composite design enables both downsizing and effective aberration correction by leveraging the complementary properties of the diffractive element and the meniscus lens.
2Length of moving object
If the positive power of the first lens unit is enhanced to downsize the optical system, then the size is reduced, but optical performance becomes unstable during focusing
Solution Approach 1:
The patent modifies the power distribution among lens units by introducing a diffractive optical element with positive power in the first lens unit and a negative meniscus lens. This parameter change allows for reduced system size while maintaining stable optical performance during focusing by balancing the power distribution.
Solution Approach 2:
The patent applies a negative meniscus lens with a specific meniscus shape in the first lens unit to locally control the light flux height variation. This local quality adjustment stabilizes the optical performance during focusing while allowing the overall system to be compact.
3Manufacturing precision
If a diffractive optical element is disposed in the first lens unit for chromatic aberration correction, then chromatic aberration is corrected, but the height of light flux passing through the focusing group varies largely
Solution Approach 1:
The patent introduces a negative meniscus lens in the first lens unit to locally control and stabilize the light flux height passing through the focusing group. This local quality adjustment compensates for the light flux height variation caused by the diffractive optical element, maintaining both chromatic aberration correction and focusing stability.
Solution Approach 2:
The negative meniscus lens acts as an intermediary element between the diffractive optical element and the focusing group. It mediates the light flux height variation introduced by the diffractive element, allowing chromatic aberration correction while maintaining stable optical performance during focusing.
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 results in a small-sized, lightweight optical system with stable optical performance across focusing distances, effectively correcting spherical, chromatic, and coma aberrations, while allowing for downsizing and weight reduction without increasing the number of lenses.
Implementation Method 1
using a diffractive optical element as a part of an optical system makes it possible to correct chromatic aberration
Implementation Method 2
The first lens unit consists of a diffractive optical element and a negative lens that are arranged in order from the object side to the image side, the negative lens having a meniscus shape in which a concave surface faces the object side
Data Source
AI summary
An optical system includes a first lens unit having positive refractive power, a second lens unit having positive refractive power that is moved during focusing, and a third lens unit having negative refractive power that are arranged in order from an object side to an image side. A distance between adjacent lens units on an optical axis of the optical system is varied during focusing. The first lens unit consists of a diffractive optical element and a negative lens that are arranged in order from the object side to the image side. The negative lens has a meniscus shape in which a concave surface faces the object side.