3D Imaging via Differential Atmospheric Absorption
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Solution Overview
Problem
High-cost designs with high-bandwidth detectors are required for precise time-of-flight measurements in LADAR systems, making them expensive and limiting their widespread adoption for 3-D imaging applications.
Innovation Solution
The use of low-bandwidth camera focal plane arrays and differential atmospheric absorption analysis, where two closely spaced laser wavelengths are employed to estimate range by measuring the ratio of intensities affected by atmospheric absorption, allowing for low-cost 3-D imaging systems that leverage natural range-dependent processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-bandwidth detectors are used for precise time-of-flight measurements, then measurement precision is improved, but device cost increases
Solution Approach 1:
The patent replaces the traditional time-of-flight measurement mechanism (requiring high-bandwidth detectors and precision electronics) with a differential absorption measurement mechanism. Instead of measuring time directly, the system measures the ratio of absorbed light at two different wavelengths, substituting a simpler optical measurement for a complex temporal measurement.
Solution Approach 2:
The patent changes the measurement parameter from time domain (time-of-flight) to spectral domain (wavelength-dependent absorption). By measuring absorption differences at two closely-spaced wavelengths, the system determines range without requiring high-bandwidth detectors, thus reducing system cost while maintaining measurement capability.
2Measurement precision
If high-bandwidth detectors and supporting electronics are used, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent substitutes the complex high-bandwidth detection system with a simpler dual-wavelength absorption measurement system. The complexity of precision timing electronics is replaced by simpler optical filters and standard detectors that measure intensity ratios rather than temporal arrivals.
Solution Approach 2:
The system uses periodic modulation of the two laser wavelengths to encode range information in the intensity ratio rather than in time. This transforms a temporal measurement problem into a spectral measurement problem, avoiding the need for high-bandwidth components.
3Measurement precision
If short laser pulses are used for high accuracy measurements, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent changes the critical parameter for range measurement from pulse duration (temporal parameter) to wavelength difference (spectral parameter). Instead of requiring short pulses for accuracy, the system uses closely-spaced wavelengths where differential absorption provides the range information, eliminating the need for complex pulse generation.
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 cost-effective 3-D imaging by using low-cost camera FPAs and differential absorption methods, providing accurate range determination without the need for high-speed detectors, suitable for applications like autonomous vehicle navigation and gaming.
Implementation Method 1
differential atmospheric absorption analysis, where two closely spaced laser wavelengths are employed to estimate range by measuring the ratio of intensities affected by atmospheric absorption
Implementation Method 2
Range to target is commonly determined by measuring a time between laser emission from a system, and from system measurement of laser light scattered from a target
Implementation Method 3
one wavelength is resonant with an atmospheric absorption line defined between the first laser and the scene and such that the other wavelength is just off the absorption line
Data Source
AI summary
Systems and methods for three-dimensional (3-D) imaging enabled by natural range-dependent processes. Multiple lasers are configured to independently flash illuminate a target object to 3- D image a resultant “scene” onto a focal plane array (FPA). The first laser produces a wavelength non-resonant with an atmospheric absorption line along the illumination path. The second laser produces a wavelength resonant with the atmospheric absorption line, and closely spaced with the non-resonant wavelength. A ratio of the respective intensities recorded at the FPA for the two wavelengths calculates a range to the target object.