Laser Projector Background Light Suppression via Focal Aperture
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Solution Overview
Problem
Light projection systems face challenges in minimizing noise from unwanted scattered light and background light while maintaining high dynamic range, especially when operating from near to far distances and when projecting onto black or white objects.
Innovation Solution
The system includes a light source, a beam-steering system, a focusing lens, an aperture to block unwanted light, and an optical detector, with a motorized focusing stage and adjustable aperture to optimize light focus and block background light, using a diode-pumped solid state laser and galvanometers for precise beam steering and a photomultiplier tube for sensitive optical signal detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an aperture is added to block unwanted scattered light, then noise from background light is reduced, but the system complexity increases
Solution Approach 1:
The patent extracts and blocks only the unwanted scattered light and background light components using an aperture positioned at the focal point of the focusing lens, while allowing the desired returned light signal to pass through to the detector. This selectively removes harmful light paths without affecting the useful signal path.
Solution Approach 2:
The aperture acts as an intermediary element between the focusing lens and the optical detector, mediating which light paths are permitted to reach the detector. It serves as a spatial filter that transmits only light from the desired direction while blocking scattered and background light.
2Measurement precision
If the light projector uses high sensitivity detection to capture signals from black objects, then measurement capability for dark objects is improved, but noise from scattered light increases
Solution Approach 1:
The patent converts the harmful scattered light into a beneficial filtering opportunity by positioning the aperture at the focal point of the focusing lens. The aperture uses the natural focal convergence of the returned light to its advantage, blocking scattered light that does not pass through the focal point while allowing the true reflected signal to pass through.
Solution Approach 2:
The aperture creates a localized region of high signal-to-noise ratio at the focal point where the desired light signal concentrates, while surrounding regions contain blocked scattered light. This local quality enhancement allows high sensitivity detection without being overwhelmed by scattered light noise.
3Adaptability or versatility
If the system operates from near to far distances, then the operating range is extended, but the consistency of light focus and signal quality deteriorates
Solution Approach 1:
The patent employs a motorized focusing stage that can dynamically adjust the position of the focusing lens to maintain optimal focus for objects at varying distances. This dynamic adjustment capability allows the system to operate consistently from near to far distances while maintaining reliable light focus and signal quality.
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 configuration enhances the operating range and consistency of light projection by minimizing noise and ensuring high-quality scanned images across varying distances and object reflectance levels, from dark to bright regions.
Implementation Method 1
The light beam strikes the surface of the object following a predetermined trajectory in a repetitive manner
Implementation Method 2
a first focusing lens operable to receive light returned from the object
Data Source
AI summary
A laser projector steers an outgoing beam of light onto an object, passing light returned from the object through a focusing lens onto an aperture rigidly coupled to an optical detector.