Glare Suppression and Ranging via Coherent Reference Beam
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Solution Overview
Problem
Optical imaging systems face challenges in detecting the range of an imaging target due to glare caused by scattering media, which also obscure the target's image, and existing systems using destructive interference are unable to facilitate both glare reduction and ranging.
Innovation Solution
A method involving a glare reduction and ranging optical system that generates coherent light beams, adjusts their power spectral density, and modifies amplitude and phase to minimize DC light power, allowing for effective glare suppression and ranging by detecting the maximum signal level at a specific frequency, enabling accurate determination of the target's range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If destructive optical interference is used to suppress glare, then glare reduction is improved, but ranging capability deteriorates
Solution Approach 1:
The patent segments the optical detection process into two distinct functional paths: one for glare suppression using destructive interference, and another for ranging using time-correlated single photon counting. By separating these functions into different detection channels with independent processing, the system achieves both glare reduction and ranging capability without mutual interference.
Solution Approach 2:
The patent introduces an intermediary mechanism - a modulated reference beam with adjustable time delay - that mediates between the glare suppression function and the ranging function. This reference beam serves dual purposes: it enables destructive interference for glare cancellation while simultaneously providing the time-of-flight information needed for ranging through correlation detection.
2Object-affected harmful factors
If coherent light beams are used for glare suppression, then glare reduction is improved, but system complexity increases
Solution Approach 1:
The patent implements a universal optical reference beam that serves multiple functions simultaneously: it provides the coherent light needed for destructive interference to cancel scattered light, and it also serves as the timing reference for ranging measurements. This multi-functional design eliminates the need for separate reference systems, thereby reducing overall system complexity despite using coherent light.
Solution Approach 2:
The patent employs parameter changes in the reference beam's temporal characteristics - specifically, introducing a controllable time delay that can be adjusted to match the round-trip time to the scattering medium. This parameter adjustment enables the system to adaptively optimize both glare suppression and ranging performance without requiring complex hardware modifications.
3Object-affected harmful factors
If power spectral density is adjusted for coherence, then glare suppression is improved, but signal detection difficulty increases
Solution Approach 1:
The patent maintains continuous emission of the modulated reference beam throughout the measurement process, ensuring uninterrupted coherent interference for glare suppression. The continuous presence of the reference beam allows for real-time cancellation of scattered light while simultaneously enabling continuous accumulation of photons for ranging detection, thereby maintaining both functions without interruption.
Solution Approach 2:
The patent applies periodic modulation to the reference beam at a specific frequency, creating a time-varying interference pattern that encodes both glare suppression and ranging information. This periodic action allows the system to distinguish the desired reflected light signal from the scattered light through frequency-domain analysis, thereby reducing detection difficulty despite the complexity of coherence control.
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 effectively reduces glare and allows for precise imaging and ranging of targets behind scattering media by canceling out scattered light, making the reflected light detectable and enabling accurate distance measurement.
Implementation Method 1
Destructive optical interference can be used to suppress the glare
Implementation Method 2
determining a power spectral density of the first light beam so that the first light beam is substantially coherent with the scattered light
Implementation Method 3
delaying the reference light beam by a first delay, where the first delay is substantially equal to the round-trip delay between a scattering medium and the glare reduction and ranging optical imaging system
Implementation Method 4
modulating the phase of the reference light beam by a first phase delay
Implementation Method 5
modulating the amplitude of the reference light beam by a first amplitude delay
Implementation Method 6
modulating the amplitude of the second reference light beam with a sinusoidal signal having a frequency
Data Source
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AI summary
In one embodiment, a method of operating a glare reduction and ranging optical system having an image sensor with pixels is provided. The method comprises: generating a first light beam with a power spectral density; generating a reference light beam from the first light beam; emitting the first light beam with a power spectral density; collecting scattered light and reflected light respectively reflected from a scattering medium and a target; determining a power spectral density of the first light beam so that the first light beam is substantially coherent with the scattered light; adjusting the power spectral density of the first light beam so that the reference light beam is substantially coherent with the scattered light; on a pixel by pixel basis, modifying the amplitude and phase of the reference light beam to minimize the DC light power at each pixel; storing the modified amplitude and phase that results in a substantially minimum detected DC light power for each pixel; increasing power spectral density of a second reference light beam; modulating the amplitude of the second reference light beam with a sinusoidal signal having a frequency; on a pixel by pixel basis, detecting the substantially maximum signal level at the modulation frequency on a pixel by adjusting a second delay of the reference light beam; and determining range to a target.