Undistorted Light Speckle Imaging via Angular Field Limiting
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Solution Overview
Problem
Existing imaging apparatuses for light speckles face challenges in maintaining undistorted patterns over large areas, particularly on surfaces with three-dimensional variations, leading to instability and errors in signal processing, especially on glossy surfaces and limiting the observation range and relative moving distance.
Innovation Solution
A large area undistorted imaging apparatus comprising a light-emitting device, a light-limiting module with a plurality of light-limiting members arranged in a one- or two-dimensional array, and a sensor, which limits the incident angular field of view to produce an array of undistorted light speckles and reconstructs them into a large-area pattern, maintaining pattern recognition capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional optical pickup head is used with standard sensor pixel size, then the device structure is simple, but the laser speckle sizes are too small (hundreds of nanometers to several micrometers) compared to the sensor pixel size (30 micrometers), causing tens of light speckles to be averaged in one pixel, making signal variation not obvious and effective information acquisition difficult
Solution Approach 1:
The patent divides the optical system into multiple imaging lenses (first imaging lens and second imaging lens) with different focal lengths, each forming speckle patterns at different magnifications. This segmentation allows the system to capture speckle patterns that are appropriately sized for sensor detection without requiring a single complex optical element
Solution Approach 2:
The patent introduces a temporal dimension by alternately using two imaging lenses with different focal lengths to form speckle patterns. This time-sequential approach allows the system to capture speckle patterns at two different magnification levels, effectively adding a dimensional aspect to the optical path that enables better signal detection
2Area of stationary object
If the observation range and relative moving distance are increased, then the imaging area on the surface is enlarged, but the laser speckles become distorted due to changes in light path phase differences
Solution Approach 1:
The patent divides the imaging area into multiple regions, each imaged by a dedicated light-limiting member with a specific field of view. This segmentation allows each sub-region to be imaged with optimized parameters, maintaining speckle pattern stability within each region while collectively covering a large area
Solution Approach 2:
The patent uses multiple light-limiting members that each capture only a portion of the total light field, with their fields of view overlapping or adjacent to each other. This partial action approach allows the system to build up a complete large-area image from multiple stable, undistorted speckle patterns, each captured under optimized conditions
3Stability of the object's composition
If a light-limiting device is used to limit the incident angular field of view, then the speckle distortion is reduced, but the imaging area on the surface is confined to a small region
Solution Approach 1:
The patent combines multiple light-limiting members, each with a limited field of view, into a unified imaging system. By merging the outputs of these individual members, the system achieves both the undistortion benefit of limited angular fields of view and the extended coverage of a large total imaging area
Solution Approach 2:
The patent arranges light-limiting members in a spatial array configuration, effectively transforming the single-dimension angular limitation into a multi-dimensional solution. Each member maintains its angular limitation for undistorted imaging, while the array arrangement extends the total imaging area across the surface
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 solution enables the acquisition of undistorted light speckle patterns over large areas, enhancing precision in pattern recognition and allowing for greater relative movement distances without distortion, suitable for applications like computer mice, fingerprint identification, and precise positioning systems.
Implementation Method 1
When the light-emitting device emits light to an object surface, scattered light is produced
Implementation Method 2
The scattered light is limited through the light-limiting module, and then a plurality of rays of diffraction light is produced
Implementation Method 3
The plurality of rays of scattered light interferes with each other, produces an array of plural undistorted light speckles
Data Source
AI summary
The present invention relates to a large area undistorted imaging apparatus for light speckles and a method thereof. The large area undistorted imaging apparatus for light speckles comprises a light-emitting device, a light-limiting module, and a sensor. The light-limiting module is adapted in front of the sensor, and includes a plurality of light-limiting members. The light-limiting members are arranged in a one- or two-dimensional array. When the light-emitting device emits light to an object surface, one or more rays of scattered light are produced. By means of the light-limiting module, said one or more rays of scattered light are limited, and a plurality of rays of diffraction light is produced. The plurality of rays of diffraction light within a certain angular field of view produced by a light-limiting member interferes with each other and produces a plurality of undistorted light speckles, and forms an array of light-speckle images on the sensor. Finally, according to the array of light-speckle images, a large-area and undistorted light-speckle pattern is given. Because the light-speckle pattern is undistorted and records the three-dimensional characteristics of the object surface, the undistorted imaging apparatus can be applied to computer mice, finger guiders, smart cards, three-dimensional fingerprint identification apparatuses, a machine tool or precise manipulator positioning systems.