Imaging Device Phase Modulation Element Grating Duty Ratio
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Solution Overview
Problem
Existing imaging devices with grating patterns face challenges in reducing device size and thickness while maintaining image quality, particularly due to decreased modulation degree and increased diffraction issues when trying to enhance focal length and collect light effectively.
Innovation Solution
An imaging device with a phase modulation element featuring a concentric grating pattern and an image sensor, where the spacing between the phase modulation element and the image sensor is adjusted to maintain a duty ratio of 0.5 or less, enhancing the modulation component and reducing diffraction effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the focal length is increased to enlarge the shot image, then the image size is improved, but the distance between the grating pattern and image sensor must be increased, which increases device thickness
Solution Approach 1:
The patent changes the optical parameters by introducing a phase modulation element with concentric grating pattern that modulates light phase rather than relying solely on geometric optics. This allows achieving effective focal length extension without proportionally increasing the physical distance between grating and sensor, thus improving image size while controlling device thickness.
2Measurement precision
If the focal length of cylindrical lens is increased to obtain finer moire fringes, then the moire fringe resolution is improved, but the diffraction influence becomes greater than light collecting action, losing the light collecting function
Solution Approach 1:
The patent replaces the traditional cylindrical lens-based geometric optics system with a phase modulation element using concentric grating pattern. This substitutes direct light collection through refraction with phase modulation followed by moire fringe generation, allowing finer resolution without excessive diffraction losses that plague traditional lens approaches.
Solution Approach 2:
The patent optimizes the spacing between phase modulation element and image sensor to achieve a duty ratio of 0.5 or less, which balances the moire fringe fineness with adequate light collection efficiency. This parameter optimization allows achieving fine resolution without the diffraction-dominated regime that occurs when simply increasing lens focal length.
3Length of stationary object
If a grating pattern is disposed immediately in front of image sensor to reduce device thickness, then the device size is reduced, but the modulation degree decreases due to overlaps from multiple point light sources, decreasing S/N ratio
Solution Approach 1:
The patent introduces a phase modulation element as an intermediary between the grating pattern and image sensor. This intermediary modulates the phase of light passing through the grating pattern, preserving the modulation degree despite the close proximity arrangement. The phase modulation prevents the degradation of S/N ratio that would occur with direct grating-sensor contact.
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 improves image quality by increasing the modulation component and reducing diffraction, allowing for finer moire fringes and better light collection, even with increased focal lengths and larger grating patterns.
Implementation Method 1
a phase modulation element provided in close to the light-receiving surface, which has a grating pattern composed of multiple zones arranged in a concentric form to modulate the phase of light passing through the grating pattern toward the light-receiving surface
Implementation Method 2
on a projection image of the grating pattern with light from a subject, another grating image is superimposed, thereby providing moire fringes
Implementation Method 3
the formation of the grating pattern from a cylindrical lens for the prevention of light shielding, in order to remedy the light amount loss caused by the use of a grating pattern with contrast
Implementation Method 4
when the focal length of the cylindrical lens is increased with respect to the zone width of the cylindrical lens, there is a problem in that the influence of diffraction with the zone width becomes greater than the light collecting action of the lens
Data Source
AI summary
An imaging device includes: an image sensor that outputs, as an image signal, light received at a light-receiving surface; a phase modulation element provided in close to the light-receiving surface, which has a grating pattern composed of multiple zones arranged in a concentric form to modulate the phase of light passing through the grating pattern toward the surface; and an image processing unit that executes image processing for the image signal output from the sensor. The spacing between the phase modulation element and the image sensor is set so that the duty ratio of the full width at half maximum for a bright section to the width for one period of a projection image of the concentric grating pattern is 0.5 or less in the case of light incidence from a point light source disposed at a distance of a subject in the axial direction of a concentric circle of the grating pattern.