Diffractive Optical Element Correcting Chromatic Aberration
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Solution Overview
Problem
Optical systems, particularly those using infrared wavelengths, suffer from chromatic aberration due to the refractive index sensitivity of glass lenses to different wavelengths, leading to distinct focal points for various wavelengths and resulting in image distortions, especially in FLIR systems imaging near infrared and mid-wavelength infrared ranges.
Innovation Solution
An imaging device and method employing a receiver optics assembly with multiple diffractive and focusing arrangements that diffract incoming radiation at specific orders to align both wavelength groups to a common focal length and focal width, reducing longitudinal and transverse chromatic aberrations by using a combination of diffractive surfaces and focusing arrangements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional glass lenses are used to focus light, then the lens can refract and focus light beams, but chromatic aberration occurs because different wavelengths are refracted by different amounts and focus at different focal points
Solution Approach 1:
The patent divides the optical system into multiple segments: a conventional glass lens for focusing and a diffractive optical element with multiple diffraction orders. Each segment handles different aspects of light manipulation, with the diffractive element specifically addressing chromatic aberration by creating multiple focal points for different wavelengths
Solution Approach 2:
The diffractive optical element acts as an intermediary between the glass lens and the image plane. It mediates the chromatic aberration problem by introducing multiple diffraction orders that compensate for the wavelength-dependent focal lengths, allowing different wavelengths to converge at the same focal plane
2Object-affected harmful factors
If diffractive elements are added to correct chromatic aberration, then chromatic aberration is reduced, but the device complexity increases
Solution Approach 1:
The patent combines the diffractive optical element with the conventional glass lens into a single integrated optical system. The diffractive pattern is applied directly to the lens surface or positioned in close proximity, merging the focusing function of the lens with the chromatic correction function of the diffractive element
Solution Approach 2:
The diffractive optical element serves multiple functions simultaneously: it corrects chromatic aberration by creating multiple diffraction orders, maintains the focusing capability of the optical system, and can be designed to work across different wavelength ranges. This multi-functionality reduces the need for additional separate correction elements
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 effectively corrects chromatic aberrations, ensuring that both wavelength groups are focused at a common focal length and width, thereby minimizing distortions and improving image quality without longitudinal or transverse chromatic aberration.
Implementation Method 1
The diffractive and focusing surface diffracts the first wavelength received from the receiver optics at an order of diffraction equal to the multiplicative factor, and further diffracts the second spectral band received from the receiver optics at a first order of diffraction
Implementation Method 2
Refraction of light occurs when the light beam passes from one medium to another, where each medium has a different refractive index, thereby causing the light beam to bend or change direction at the interface between the two media
Implementation Method 3
the first wavelength and the second spectral band emanating from the second diffractive and focusing arrangement focuses at a common focal length along an optical axis, and at a common focal plane width perpendicular to the optical axis
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
Imaging device and method, the device including receiver optics, a diffractive and focusing surface, and a pair of diffractive and focusing arrangements, the receiver optics receiving radiation including a first wavelength selected from a first spectral band, and a second spectral band, where the first wavelength is substantially a multiplicative factor less than the midpoint of the second spectral band, the diffractive and focusing surface diffracting the first wavelength at an order of diffraction substantially equal to the multiplicative factor, and diffracting the second spectral band at a first order of diffraction, each of the diffractive and focusing arrangements diffracting, in turn, the first wavelength at a first order of diffraction, such that the first wavelength and the second spectral band emanating from the second diffractive and focusing arrangement focuses at a substantially common focal length and at a substantially common focal plane width.