Multiple F-Number Lens With Wavelength-Selective Aperture Filter
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Solution Overview
Problem
Existing imaging lenses lack the ability to efficiently accommodate different f-numbers for near-infrared (NIR) and visible light, leading to suboptimal performance in time-of-flight depth sensing and computer vision applications.
Innovation Solution
A wavelength-selective filter positioned at the aperture stop of the imaging lens, with distinct transmission bands for NIR and visible light, allowing for a lower f-number for NIR and a higher f-number for visible light, combined with pixel binning for different resolution modes in the image sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single f-number is used for both NIR and visible light, then the lens structure is simple, but the performance is suboptimal for both TOF depth sensing and computer vision applications
Solution Approach 1:
The patent applies local quality by implementing different f-numbers for different wavelength ranges through a wavelength-selective filter at the aperture stop. The filter has a first region for visible light and a second region for NIR light, allowing the lens to have optimized aperture characteristics for each wavelength range independently, thus achieving local optimization without requiring completely separate lens systems.
2Use of energy by moving object
If a lower f-number is used for NIR light to improve TOF depth sensing, then more NIR light is captured, but visible light imaging becomes overexposed and lower resolution
Solution Approach 1:
The wavelength-selective filter enables different aperture settings (f-numbers) for different wavelength ranges. The first region of the filter corresponds to visible light and the second region corresponds to NIR light, allowing the lens to capture more NIR light (lower f-number for NIR) while maintaining appropriate visible light exposure (higher f-number for visible), thus resolving the contradiction between NIR light capture efficiency and visible light image quality.
3Manufacturing precision
If a higher f-number is used for visible light to improve image resolution, then depth of field increases, but NIR light capture becomes insufficient for effective TOF sensing
Solution Approach 1:
The patent implements local quality by using a wavelength-selective filter that provides different transmission characteristics for visible and NIR light. This allows the lens to maintain a higher f-number for visible light imaging (improving spatial resolution and depth of field) while simultaneously providing a lower effective f-number for NIR light (improving light integration for TOF sensing), thus resolving the contradiction between visible light resolution and NIR light capture.
4Reliability
If separate lens systems are used for NIR and visible light, then each wavelength range can be optimized independently, but system cost, size, and power consumption increase
Solution Approach 1:
The patent applies universality by designing a single imaging lens that can perform both TOF depth sensing and computer vision functions. The wavelength-selective filter at the aperture stop enables the lens to have optimized characteristics for both NIR and visible light wavelengths, allowing one lens to replace what would traditionally require separate lens systems, thus reducing system cost, size, and complexity while maintaining wavelength-specific optimization.
5Use of energy by moving object
If the aperture stop is made large to capture more NIR light, then TOF sensing improves, but ghost images increase and visible light imaging suffers
Solution Approach 1:
The wavelength-selective filter enables different effective aperture sizes for different wavelengths. For NIR light, the filter allows a larger effective aperture (lower f-number) to capture more signal for TOF sensing. For visible light, the filter provides a smaller effective aperture (higher f-number) that reduces ghost images and maintains proper exposure. This local optimization for each wavelength range resolves the contradiction between NIR signal strength and ghost image reduction.
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
Enables efficient TOF depth sensing with lower power illumination and higher spatial resolution for computer vision, reducing system cost, size, and power consumption while minimizing ghost images and sensor saturation.
Implementation Method 1
The filter includes a central region with a first linear dimension, and an outer region surrounding the central region with a second linear dimension greater than the first linear dimension. The central region of the filter is characterized by a first transmission band in an NIR wavelength range and a second transmission band in a visible wavelength range. The outer region of the filter is characterized by a third transmission band in the NIR wavelength range and substantially low transmittance values in the visible wavelength range.
Implementation Method 2
The imaging lens includes one or more lens elements configured to receive and focus the portion of the each of the plurality of NIR light pulses reflected off of the one or more first objects onto an image plane, and to receive and focus visible light reflected off of one or more second objects onto the image plane.
Implementation Method 3
detecting, using the image sensor, a three-dimensional image of the one or more first objects by determining a time of flight for the portion of each of the plurality of NIR light pulses from emission to detection
Implementation Method 4
detecting, using the image sensor, a two-dimensional intensity image of the one or more second objects in the visible wavelength range
Data Source
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AI summary
An imaging lens includes one or more lens elements configured to receive and focus light in a first wavelength range reflected off of one or more first objects onto an image plane, and to receive and focus light in a second wavelength range reflected off of one or more second objects onto the image plane. The imaging lens further includes an aperture stop and a filter positioned at the aperture stop. The filter includes a central region and an outer region surrounding the central region. The central region of the filter is characterized by a first transmission band in the first wavelength range and a second transmission band in the second wavelength range. The outer region of the filter is characterized by a third transmission band in the first wavelength range and substantially low transmittance values in the second wavelength range.