Distance Imaging Correlation Smoothing for Speckle Noise Reduction
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Solution Overview
Problem
Existing ranging technologies using coherent illumination light, such as laser light, suffer from speckle noise in distance images, which can obscure the actual surface shape of a subject, particularly when the surface is smooth, and existing methods require multiple light sources or wavelength modulation, which can be costly or complex.
Innovation Solution
A ranging apparatus and method that uses multiple light sources positioned at different angles to generate multiple evaluation distance images, calculates correlation values between these images, and applies a smoothing process based on these values to reduce speckle noise while preserving surface details, using a light source control unit to switch between normal and evaluation patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If multiple light sources or wavelength modulation is used to reduce speckle noise, then speckle noise reduction is improved, but device complexity and cost increase
Solution Approach 1:
The patent divides the evaluation process into separate evaluation regions within the distance image, calculating correlation values for each region independently. This segmentation allows targeted speckle noise reduction in specific areas without affecting the entire image, reducing the need for complex global processing systems.
Solution Approach 2:
The patent creates multiple evaluation distance images by capturing images at different times with the same light source, effectively copying the measurement process. These copies are then correlated to identify and reduce speckle noise, eliminating the need for multiple physical light sources or wavelength modulation.
2Object-affected harmful factors
If aggressive smoothing is applied to reduce speckle noise, then speckle noise is reduced, but surface detail accuracy deteriorates
Solution Approach 1:
The patent applies different smoothing intensities to different evaluation regions based on their correlation values. Regions with low correlation values (indicating high speckle noise) receive stronger smoothing, while regions with high correlation values (indicating preserved surface details) receive weaker or no smoothing. This local differentiation maintains surface detail accuracy while reducing speckle noise where present.
Solution Approach 2:
The patent dynamically adjusts the smoothing process intensity based on calculated correlation values between evaluation distance images. By changing the smoothing parameter according to the correlation value, the system optimizes the balance between noise reduction and detail preservation for each region, preventing over-smoothing that would lose surface details.
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
Effectively reduces speckle noise in distance images while maintaining the reproducibility of surface details, enhancing image quality by adjusting the smoothing process based on correlation values to minimize speckle noise where it is dominant and preserve surface features.
Implementation Method 1
a first light source that irradiates a subject with a first illumination light; a second light source that irradiates the subject with a second illumination light
Implementation Method 2
a distance sensor that detects a light from the subject and generates a distance image
Implementation Method 3
a correlator that calculates, for each of a plurality of evaluation regions set in the distance image, a correlation value between a first evaluation distance image generated at a time of irradiation with the first evaluation pattern and a second evaluation distance image generated at a time of irradiation with the second evaluation pattern
Implementation Method 4
a smoothing processing unit that generates a corrected distance image by applying a smoothing process of an intensity determined by the correlation value to a normal distance image generated at a time of irradiation with the normal pattern
Data Source
AI summary
A ranging apparatus includes: a first light source that irradiates a subject; a second light source that irradiates the subject; a distance sensor that detects a light from the subject and generates a distance image; a light source control unit that switches between a normal pattern of lighting the first light source and the second light source, a first evaluation pattern of lighting the first light source, and a second evaluation pattern of lighting the second light source; a correlator that calculates a correlation value between a first evaluation distance image generated at a time of irradiation with the first evaluation pattern and a second evaluation distance image generated at a time of irradiation with the second evaluation pattern; and a smoothing processing unit that generates a corrected distance image by applying a smoothing process of an intensity determined by the correlation value to a normal distance image.