Digital Lock-In Detection for Optical Tomography Noise Reduction

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Solution Overview

Problem

Analog detection systems in optical tomography suffer from signal drift, output offsets, gain errors, limited dynamic range, and sensitivity to temperature and age, leading to measurement uncertainty and noise elevation, which restricts the detection sensitivity and dynamic range of optical tomography systems.

Innovation Solution

The implementation of digital lock-in detection using a phase-independent quadrature technique and a digital signal processor, along with a low-pass anti-aliasing filter and an analog-to-digital converter, to perform digital processing and filtering, reducing noise and enhancing detection sensitivity and dynamic range.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If analog detection systems are used in optical tomography, then the system can perform signal conditioning and filtering, but the detection sensitivity and dynamic range are limited due to noise elevation and measurement uncertainty

Engineering Contradiction:

Improvedetection sensitivityVSAvoidnoise and measurement uncertainty

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the analog detection system with a digital detection system. Specifically, analog-to-digital converters are used to convert optical signals to digital signals, and digital signal processing techniques are applied instead of analog signal conditioning. This substitution eliminates the harmful effects of analog component tolerances, temperature sensitivity, and drift, thereby reducing noise and measurement uncertainty while improving detection sensitivity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the operational parameters of the detection system by using digital rather than analog processing. Digital signal processing allows for precise control of filtering parameters, gain settings, and noise reduction algorithms, enabling optimization of detection sensitivity and dynamic range without the limitations of analog component variations.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If analog detection systems are used in optical tomography, then the system can process optical signals, but the dynamic range is limited due to analog processing constraints

Engineering Contradiction:

Improvedynamic rangeVSAvoidanalog processing constraints

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent replaces analog signal processing circuits with digital signal processing algorithms. This substitution removes the constraints of analog component linearity, dynamic range limitations, and signal degradation, allowing the system to handle a wider range of signal intensities with higher fidelity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If analog phase-sensitive lock-in methods are employed, then the optical signal can be extracted from noise, but signal drift and output offsets occur

Engineering Contradiction:

Improvesignal extraction accuracyVSAvoidsignal drift and output offsets

Core Design Contradiction:

Measurement precisionVSStability of the object's composition

Solution Approach 1:

The patent replaces analog phase-sensitive lock-in methods with digital lock-in detection algorithms. The digital implementation eliminates drift and offset issues inherent in analog circuits by using stable digital reference signals and computational processing. The digital system can accurately extract optical signals from noise without the signal degradation caused by analog component instability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Measurement precision

If digital detection is implemented, then noise is reduced and detection sensitivity is improved, but the system complexity increases

Engineering Contradiction:

Improvedetection sensitivityVSAvoiddigital processing requirements

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces complex analog processing circuits with digital signal processing algorithms that can be implemented in software or firmware. This substitution reduces hardware complexity while maintaining or improving detection sensitivity, as digital processing can be optimized through algorithmic approaches rather than requiring precise analog component matching.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS7463362B2Digital signal processor-based detection system, method, and apparatus for optical tomography

Publication Date: 2008.12.09 THE TRUSTEES OF COLUMBIA UNIV IN THE CITY OF NEW YORK

AI summary

The present invention provides systems, methods and apparatuses that perform digital detection for use in optical tomography. Methods and systems are provided in which digital lock-in detection is performed using an algorithm that employs a phase-independent quadrature technique. Methods and systems are provided in which a unique manipulation of an ordinary averaging filter optimized for sources discrimination and the consequent sampling constraints is presented as a novel filtering scheme for the lock-in detection. Systems and apparatuses are provided which include a digital signal processor which performs digital lock-in detection and an integrated complex programmable logic device for timing control. Apparatuses are provided which include an instrument having an integrated digital signal processor for performing digital processing and detection for use in optical tomography.