Dual Phase Mask Optical Element for Athermalization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional optical systems face challenges in extending the depth of field (DOF) and athermalization, particularly in infrared imaging, where temperature-induced focal shifts complicate image quality and require complex mechanical or opto-mechanical solutions.
Innovation Solution
An optical element comprising two phase shift masks, one with a positive phase shift and the other with a negative phase shift, made from materials with varying refractive indices, are arranged serially on an optical axis, allowing for athermalization and extended DOF by maintaining a consistent phase shift across temperature and wavelength ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single phase mask is used to extend depth of field, then depth of field is extended, but temperature-induced focal shifts cause image quality degradation
Solution Approach 1:
The optical element is divided into two separate phase masks with opposite polarity (positive and negative), each contributing to the overall phase modulation. This segmentation allows the system to achieve both depth of field extension and thermal compensation through the combined effect of the two masks, resolving the contradiction between DOF extension and temperature sensitivity.
Solution Approach 2:
The second phase mask with negative polarity acts as a counterweight to the first phase mask with positive polarity. The opposite phase shifts cancel out temperature-induced focal shifts while maintaining the depth of field extension effect, effectively using counterbalancing to resolve the temperature sensitivity problem.
2Reliability
If complex mechanical compensation is used to address temperature-induced focal shifts, then image quality is maintained, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical compensation systems with a purely optical solution using two phase masks. The thermal compensation is achieved through optical phase modulation rather than mechanical adjustment, significantly reducing device complexity while maintaining image quality across temperature variations.
Solution Approach 2:
The optical element uses a composite structure combining two different phase mask designs with opposite polarities. This composite approach integrates both depth of field extension and thermal compensation functions into a single optical element, eliminating the need for separate mechanical compensation systems.
3Temperature
If phase masks with varying refractive indices are used, then athermalization is achieved, but manufacturing precision requirements increase
Solution Approach 1:
The patent utilizes changes in refractive index parameters of the optical materials with temperature to achieve athermalization. By selecting materials with appropriate thermal coefficients and designing the phase masks with complementary characteristics, the system compensates for temperature effects while maintaining feasible manufacturing tolerances through careful parameter selection.
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 extends the depth of field and athermalizes the optical system, improving image quality across a wide temperature range and wavelength spectrum, reducing the need for complex mechanical compensation and enhancing performance in both in-focus and out-of-focus conditions.
Implementation Method 1
a first phase shift mask formed on a first optical material and constituted to generate a positive phase shift
Implementation Method 2
a refractive index of at least one of the first and second optical materials varies with the temperature
Implementation Method 3
a second phase shift mask formed on a second optical material and constituted to generate a negative phase shift
Implementation Method 4
a refractive index of at least one of the first and second optical materials varies with the temperature
Implementation Method 5
allowing for athermalization and extended DOF by maintaining a consistent phase shift across temperature and wavelength ranges
Implementation Method 6
maintaining a consistent phase shift across temperature and wavelength ranges
Data Source
AI summary
An optical element is disclosed. The optical element comprises: a first phase shift mask formed on a first optical material and constituted to generate a positive phase shift, and a second phase shift mask formed on a second optical material and constituted to generate a negative phase shift, wherein the phase shift masks are arranged serially on an optical axis, and wherein a refractive index of at least one of the first and second optical materials varies with the temperature at a rate of at least 50×10−6 per degree Kelvin.