Graduated Optical Filter for Depth Sensing Dynamic Range
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Solution Overview
Problem
Imaging systems face challenges in accurately capturing depth maps due to dynamic range and signal-to-noise ratio limitations, where nearby surfaces appear overexposed and distant surfaces underexposed, making it difficult to resolve patterned features in a single exposure.
Innovation Solution
The implementation of a graduated optical filter or spatial light modulator that attenuates light intensity differently for nearby and distant surfaces, allowing for a single-exposure image with resolvable features on both surfaces by normalizing light intensity, and a processor adjusts the filter or modulator based on image data to reduce overexposure and underexposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single exposure is used to capture both nearby and distant surfaces, then the imaging speed is improved, but the measurement precision deteriorates due to overexposure of nearby surfaces and underexposure of distant surfaces
Solution Approach 1:
The optical filter is designed with spatially varying attenuation properties, where different regions of the filter attenuate light by different amounts. Specifically, the filter has higher attenuation for light paths corresponding to nearby surfaces and lower attenuation for light paths corresponding to distant surfaces. This local differentiation in filter properties enables simultaneous proper exposure of both nearby and distant surfaces in a single capture, resolving the contradiction between imaging speed and depth mapping accuracy.
2Measurement precision
If the dynamic range of light incident on the image sensor is reduced by attenuating nearby surfaces, then the feature discernibility is improved, but the light intensity is reduced
Solution Approach 1:
The optical filter applies spatially differentiated attenuation, where the attenuation strength varies across different spatial regions corresponding to different object distances. Nearby surfaces receive stronger attenuation to reduce overexposure and improve feature discernibility, while distant surfaces receive weaker attenuation to maintain sufficient light intensity. This localized adjustment resolves the contradiction between feature discernibility and light intensity preservation.
3Measurement precision
If multiple exposures are used to capture different depth ranges, then the measurement precision is improved, but the loss of time increases
Solution Approach 1:
The system performs preliminary action by pre-configuring the optical filter with spatially varying attenuation properties before the imaging capture. This pre-established filter configuration enables the system to capture the entire depth range in a single exposure without requiring multiple sequential captures. The preliminary setup of the filter eliminates the time loss associated with multiple exposures while maintaining depth mapping precision across different ranges.
4Device complexity
If uniform light attenuation is applied across all surfaces, then the device complexity is reduced, but the adaptability deteriorates because it cannot handle varying distances
Solution Approach 1:
The optical filter transitions from a uniform structure to one with local quality variations, where different spatial regions have different attenuation properties. This allows the filter to adapt to the varying distances of surfaces in the scene, with higher attenuation for nearby surfaces and lower attenuation for distant surfaces. The introduction of spatially differentiated properties enhances distance range adaptability while maintaining relatively simple filter implementation.
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 approach enables the capture of a single-exposure image with a lower dynamic range, allowing for accurate depth estimation and improved feature discernibility on both nearby and distant surfaces, reducing the need for post-processing and accommodating dynamic environments.
Implementation Method 1
The optical filter may include two or more regions configured to attenuate the patterned light by different amounts. Patterned light incident on surfaces close to the system may be attenuated to a greater extent than patterned light incident on surfaces distant from the system.
Implementation Method 2
The graduated optical filter includes a first region to attenuate an intensity of the first portion of the patterned light by a first amount and a second region to attenuate an intensity of the second portion of the patterned light by a second amount. The first amount is greater than the second amount.
Data Source
AI summary
An example system includes a patterned light projector operable to direct first and second portions of patterned light toward first and second surfaces, respectively, in an environment. The first and second surfaces may be at first and second distances, respectively, from the structured light projector. A graduated optical filter may be situated along an optical path of the patterned light. The graduated optical filter includes first and second regions to attenuate an intensity of the first and second portions of the patterned light, respectively, by first and second amounts, respectively. The first amount is greater than the second amount. The system additionally includes an image sensor operable to generate image data based on at least the first and second portions of the patterned light and a processor configured to determine first and second values indicative of an estimate of the first and second distances, respectively, based on the image data.