Compressive Imaging Using Photonic Time-Stretch and Spectral Encoding
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Solution Overview
Problem
Current ultrahigh-speed continuous imaging systems are limited in speed, resolution, and image quality due to the measurement rate of electronic digitizers, and they collect more data than necessary, making them inefficient for high-speed applications.
Innovation Solution
A compressive imaging system using broadband pulsed light with chirped processing and electro-optic modulation to encode unique pseudorandom binary patterns onto the spectra of laser pulses, allowing for ultrafast structured illumination and reconstruction of images from fewer measurements than conventional Nyquist sampling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional CCD arrays or photonic time-stretch systems read out pixel information serially with a single ADC, then the system can be implemented with existing hardware, but the number of pixels acquired per second is fixed at the sampling rate of the ADC, limiting imaging speed
Solution Approach 1:
The patent replaces the electronic ADC-based readout system with an optical processing system that uses photonic time-stretch to parallelize the measurement process. Instead of serially converting pixels to digital values, the system optically stretches the temporal waveform of the pixel data and measures it simultaneously, eliminating the ADC sampling rate bottleneck and enabling imaging speeds far exceeding electronic digitizer capabilities.
Solution Approach 2:
The patent transforms the one-dimensional temporal sampling problem into a two-dimensional measurement space by using photonic time-stretch to map temporal information into the spectral domain. This allows the system to measure multiple pixels simultaneously by encoding them in the frequency domain, effectively adding a spectral dimension to the measurement process and overcoming the single ADC rate limitation.
2Loss of information
If ultrahigh-speed imaging systems collect data at the ADC sampling rate, then complete pixel information is captured, but far more data is collected than necessary, making the system inefficient
Solution Approach 1:
The patent extracts only the essential information needed for image reconstruction by using compressive sensing techniques. Instead of capturing all pixel data at full ADC sampling rate, the system measures a compressed subset of the signal in the spectral domain, extracting the minimum necessary information to reconstruct images while discarding redundant data, thereby improving acquisition efficiency without losing critical image information.
Solution Approach 2:
The patent changes the measurement parameters from temporal sampling at ADC rate to spectral frequency measurements. By transforming the measurement domain from time to frequency, the system can capture image-relevant information more efficiently, as natural images are compressible and contain redundant information that can be recovered from fewer spectral measurements through compressive sensing reconstruction.
3Speed
If photonic time-stretch systems are used for ultrahigh-speed imaging, then imaging speed is improved, but the system remains fundamentally limited by the measurement rate of electronic digitizers
Solution Approach 1:
The patent replaces the electronic ADC measurement bottleneck with an all-optical measurement approach. By using photonic time-stretch to encode spatial pixel information into temporal waveforms and then measuring the spectral content optically, the system eliminates the fundamental ADC sampling rate limitation, achieving imaging speeds that are not constrained by electronic digitizer performance.
Solution Approach 2:
The patent employs periodic pulsed laser illumination to encode the image signal into a time-stretched waveform that can be spectrally analyzed. The periodic nature of the pulsed illumination creates a repeating temporal pattern that, when stretched and measured in the frequency domain, allows for high-speed image acquisition without being limited by ADC sampling rates, as the measurement is performed optically rather than electronically.
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
The system achieves higher image acquisition rates with better signal-to-noise ratio and reduced hardware requirements, enabling efficient imaging of high-speed phenomena with improved resolution and compression ratios.
Implementation Method 1
a broadband pulsed light source configured to provide a plurality of illumination pulses
Implementation Method 2
a first dispersion component optically coupled with the broadband pulsed light source to receive the plurality of illumination pulses therefrom to provide a corresponding plurality of dispersed pulses, each having optical dispersion imparted thereto by the first dispersion component
Implementation Method 3
an optical modulator arranged to modulate each pulse of the plurality of dispersed pulses to provide the preselected spectra such that each pulse is distinguishable from all other pulses of the plurality of light pulses
Implementation Method 4
a second dispersion component arranged to receive each of the plurality of dispersed pulses after being modulated, the second dispersion component acting to substantially cancel dispersion imposed by the first dispersion component to provide a plurality of undispersed illumination pulses having mutually distinguishable spectra
Implementation Method 5
a detection system configured to detect at least a portion of the illumination light after being at least one of reflected from, scattered from, or transmitted through the object of interest or to detect fluorescent light from the object of interest
Data Source
AI summary
A compressive imaging system includes an illumination system arranged to illuminate an object of interest with illumination light, and a detection system configured to detect at least a portion of the illumination light after being at least one of reflected from, scattered from, or transmitted through the object of interest or to detect fluorescent light from the object of interest and to provide an imaging signal. The compressive imaging system further includes an image processing system configured to communicate with the detection system to receive the imaging signal. The illumination light from the illumination system comprises a plurality of light pulses such that each light pulse has a preselected spectrum that is distinguishable from spectra of all other pulses. The image processing system is configured to form an image of the object of interest using information concerning the preselected spectra of the plurality of light pulses.