Zoom Lens Diffractive Optical Element Chromatic Aberration Control
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Solution Overview
Problem
Existing zoom lenses with high zoom ratios and small sizes face challenges in minimizing axial chromatic aberration, particularly at the telephoto end, while maintaining high optical performance across the entire zoom range.
Innovation Solution
A zoom lens design incorporating a first lens unit with a positive refractive power and a second lens unit having a negative refractive power, where the second lens unit moves during zooming, and the first lens unit includes a diffractive optical element cemented between two optical elements, with specific conditional expressions governing the focal lengths and movement ratios to control aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the first lens unit is moved greatly toward the object side during zooming to achieve a high zoom ratio, then the zoom ratio is increased, but the total lens length at the telephoto end is increased and the zoom lens is increased in size as a whole
Solution Approach 1:
The patent replaces the conventional mechanical lens movement system with a diffractive optical element that uses diffraction to achieve magnification. The diffractive optical element is configured to diffract light at different angles for different wavelengths, enabling high zoom ratio without requiring large mechanical displacements of lens units, thus maintaining compact total lens length.
Solution Approach 2:
The patent changes the optical parameters by introducing a diffractive optical element with specific diffraction orders and wavelengths. By controlling the diffraction parameters (diffraction order, wavelength, grating period), the system achieves variable magnification without mechanical movement, resolving the contradiction between zoom ratio and lens length.
2Reliability
If the diffractive optical element is applied to the first lens unit to reduce the chromatic aberrations at the telephoto end, then the chromatic aberrations are reduced, but the first lens unit is moved greatly toward the object side during zooming which increases the total lens length
Solution Approach 1:
The patent eliminates the need for mechanical movement of the first lens unit by using a diffractive optical element that achieves both chromatic aberration correction and magnification through optical diffraction. The diffractive element remains stationary while providing wavelength-dependent light manipulation, thus maintaining compact lens length while correcting chromatic aberrations.
Solution Approach 2:
The patent uses a composite optical system combining refractive lens elements with a diffractive optical element. This composite structure leverages the complementary properties of refractive optics (for basic focusing) and diffractive optics (for chromatic aberration correction and magnification control), achieving high performance without increasing lens length.
3Volume of moving object
If the zoom lens is downsized as a whole while increasing the zoom ratio, then the compact size is achieved, but a large amount of axial chromatic aberration is caused in the first lens unit particularly at the telephoto end
Solution Approach 1:
The patent replaces conventional refractive-only optics with a diffractive-optical system that inherently corrects chromatic aberrations through the diffraction phenomenon. The diffractive optical element introduces wavelength-dependent path differences that compensate for chromatic dispersion, enabling compact lens design without sacrificing optical performance.
Solution Approach 2:
The patent converts the typically harmful effect of diffraction (which can cause scattering) into a beneficial mechanism for chromatic aberration correction. By carefully designing the diffractive grating structure, the patent exploits the wavelength-dependent diffraction angles to separate and correct different color components, turning a potential disadvantage into an advantage for achieving both compact size and high optical performance.
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 design achieves a high zoom ratio with reduced chromatic aberrations and high optical performance across the entire zoom range, while maintaining a compact size by optimizing the refractive powers and movements of lens units.
Implementation Method 1
there is known a zoom lens using a diffractive optical element in an optical path in order to reduce occurrence of chromatic aberrations such as axial chromatic aberration and lateral chromatic aberration
Data Source
AI summary
Provided is a zoom lens comprising, in order from an object side to an image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a rear unit including at least one lens unit, in which the second lens unit is configured to move during zooming, an interval between each pair of adjacent lens units is changed during zooming, the rear unit has a positive refractive power over an entire zoom range, and the first lens unit includes a diffraction surface formed at a cemented surface of two optical elements cemented to each other. A focal length of the first lens unit, an amount of movement of the second lens unit during zooming from a wide angle end to a telephoto end and a back focus at the wide angle end are appropriately set.