Non-diffractive Phase Mask for Multi-range Imaging Contrast
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Solution Overview
Problem
Multifocal and bifocal lenses suffer from inefficient light energy distribution, resulting in reduced image contrast due to unfocused light creating halos around in-focus images, particularly in dual-range imaging applications where high contrast is required for specific regions but not for others.
Innovation Solution
An optical imaging system incorporating a phase mask with non-diffractive, narrowly bounded phase variation and a single focus lens, optimized for incoherent light, which alters the wavefront to achieve high contrast and resolution in discrete regions of interest without the need for multiple foci or diffraction into multiple orders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multifocal or bifocal lenses are used to provide multiple focal ranges, then the ability to image at different distances is improved, but image contrast is reduced due to unfocused light creating halos around in-focus images
Solution Approach 1:
The patent extracts and eliminates the diffractive element that causes multiple focal orders from the optical system. By using a non-diffractive phase mask instead, the system achieves multi-range imaging capability while preventing the generation of halo effects that reduce image contrast, thus separating the beneficial focusing function from the harmful diffractive effects.
Solution Approach 2:
The patent changes the phase mask parameters from diffractive (with sharp edges and high spatial frequency) to non-diffractive (with smooth transitions and lower spatial frequency). This parameter change allows the system to maintain multiple focal ranges while reducing optical aberrations and eliminating halo effects, thereby improving image contrast.
2Adaptability or versatility
If diffractive phase masks are used to create multiple focal orders, then multi-range imaging is enabled, but manufacturing complexity increases due to requirement for small features
Solution Approach 1:
The patent fundamentally changes the parameter of phase mask spatial frequency, transitioning from high spatial frequency diffractive patterns to low spatial frequency smooth phase variations. This parameter change results in larger feature sizes that are much easier to manufacture using conventional lithography techniques, while still achieving the desired multi-range imaging function.
Solution Approach 2:
The patent replaces the traditional diffractive optical element (which relies on sub-wavelength features) with a non-diffractive phase mask that uses macroscopic smooth phase variations. This substitution eliminates the need for complex nanofabrication processes and enables manufacturing with standard optical fabrication techniques.
3Adaptability or versatility
If bifocal lenses are used to correct presbyopia, then near and distant vision is provided, but lens thickness increases
Solution Approach 1:
The patent removes the thick diffractive optical elements from the lens structure and replaces them with a thin non-diffractive phase mask. This extraction of the focusing function from the bulk lens material allows for thinner overall lens construction while maintaining the ability to correct presbyopia through phase modulation.
Solution Approach 2:
The patent introduces a separate non-diffractive phase mask as an intermediary element that performs the presbyopia correction function. This phase mask acts as a mediator between the incident light and the retina, providing multiple focal ranges without requiring the main lens to be thick or complex, thus achieving thin-lens presbyopia correction.
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 system provides high contrast and resolution for near and far regions while maintaining lower contrast in intermediate ranges, effectively addressing the inefficiencies of traditional multifocal lenses by using a phase mask that modifies the Modulated Transfer Function to enhance image quality without the need for digital post-processing.
Implementation Method 1
The phase mask section has a generally non-diffractive, narrowly bounded, phase variation, tailored so as to provide a characteristic profile of a through-object Modulated Transfer Function (MTF) of the imaging system
Implementation Method 2
a single focus lens section, and a light detecting surface. The latter can be implemented by, for example, a pixel detector array (PDA)
Data Source
AI summary
An imaging system is presented for use in multi-range imaging of an object scene by incoherent light. The imaging system comprises aligned a phase mask section, a single focus lens section, and a pixel detector array (PDA). The phase mask section has a generally non-diffractive, narrowly bounded, phase variation corresponding to a profile of a through-object Modulated Transfer Function (MTF) of the imaging system, where the profile has, at an at least one non-zero spatial frequency, at least two regions of growth leading to the MTF higher than 10%.