Compact Spatial Filter with Three-Lens Scattering Control
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Solution Overview
Problem
Conventional spatial filters for laser range finders (LRFs) require significant space, making them unsuitable for compact designs, and internal light scattering saturates detectors, preventing the detection of short-range objects.
Innovation Solution
A compact spatial filter design using three lenses - a detector lens, a re-collimation lens, and a re-focusing lens - that reduces internal light scattering without increasing the LRF's size, combined with an optical band pass filter integrated into the lens surfaces, minimizing detector saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional spatial filter is used to reduce internal light scattering, then detector saturation is reduced, but the LRF housing size increases significantly
Solution Approach 1:
The spatial filter is integrated within the existing optical receiver housing by positioning the lens assembly within the available internal space. The filter shares the housing volume with other optical components, nesting the spatial filtering function within the existing structure rather than adding external volume.
Solution Approach 2:
The patent positions the spatial filter at a specific location within the optical path where it can intercept scattered light without requiring additional housing volume. By utilizing the third dimension (depth) within the existing optical train and positioning components at precise axial locations, the filter reduces scattered light while maintaining compact housing dimensions.
2Measurement precision
If the detector is exposed to high-energy outgoing laser pulses to detect short-range objects, then detection sensitivity improves, but detector saturation occurs due to internal light scattering
Solution Approach 1:
The spatial filter acts as an intermediary element positioned in the optical path between the scattered light sources and the detector. It selectively blocks scattered light while allowing the collimated return signal to pass through to the detector, mediating between the high-energy laser pulses and the detector to prevent saturation while preserving detection capability.
Solution Approach 2:
The spatial filter provides localized light rejection at the specific location where scattered light converges in the optical path. By positioning the filter at the focal point of the detector lens where scattered light is most intense, it selectively removes harmful scattered light while preserving the collimated return signal quality that reaches the detector.
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 compact spatial filter effectively reduces internal light scattering, preserving the field of view and enabling detection of short-range objects without enlarging the LRF housing.
Implementation Method 1
a detector lens to focus collimated, incident light at a first focal point
Implementation Method 2
a re-collimation lens to collimate the light from the pinhole aperture into re-collimated light
Implementation Method 3
a re-focusing lens to focus the re-collimated light at a second focal point
Implementation Method 4
an optical band pass filter integrated into the lens surfaces
Data Source
AI summary
An optical receiver comprises a spatial filter and an optical detector. The spatial filter comprises: a detector lens to focus collimated, incident light at a first focal point, the detector lens having a first focal length; a light barrier surface having a pinhole aperture to allow the light focused by the detector lens to pass through the light barrier surface; a re-collimation lens to collimate the light from the pinhole aperture into re-collimated light; and a re-focusing lens to focus the re-collimated light at a second focal point, the re-focusing lens having a second focal length that is shorter than the first focal length. The optical detector detects the light re-focused by the re-focusing lens.