Image Invariant Optical Speckle Capturing Device
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Solution Overview
Problem
Existing optical speckle capturing devices face challenges in accurately capturing two-dimensional speckle patterns due to issues with speckle size, shape variation, and intensity fluctuation, particularly when the surface is smooth, leading to degraded resolution and sensitivity.
Innovation Solution
An image invariant optical speckle capturing device and method that uses a light restrictive aperture to confine the angular field of view, combining factors like speckle size, focal length, and image capturing area to ensure that speckles remain invariant in shape and intensity during relative motion, allowing for precise recognition and positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional optical speckle capturing device is used, then the device structure is simple, but the speckle size is too small and shape varies during relative motion, degrading resolution and sensitivity
Solution Approach 1:
The optical system is segmented into distinct functional modules: a light source module, a light restrictive module with aperture, an imaging lens module, and a sensor module. This segmentation allows each component to be optimized independently for its specific function while maintaining overall system performance.
Solution Approach 2:
A light restrictive module with aperture is introduced as an intermediary element between the scattered light and the sensor. This aperture acts as a mediator that controls the angular field of view and diffracts the light to produce invariant speckles, resolving the contradiction between simple structure and measurement precision.
2Stability of the object's composition
If the aperture is placed at the focal point of the imaging lens, then the height variation has little effect on speckle, but the speckle size is still too small and shape varies during relative motion
Solution Approach 1:
The solution moves from considering only the axial position (one dimension) to controlling the angular field of view (adding angular dimension). By restricting the angular range of scattered light that reaches the sensor, the system achieves speckle invariance during relative motion, resolving the contradiction between stability and size consistency.
Solution Approach 2:
The aperture size and its position relative to the imaging lens are carefully controlled to achieve optimal diffraction effects. By adjusting these parameters, the system produces speckles of appropriate size that remain invariant during relative motion, overcoming the limitations of conventional single-point aperture placement.
3Illumination intensity
If the sensor receives scattered lights from a wide angular field of view, then the light intensity is sufficient, but the speckle intensity fluctuates and shape varies during relative motion
Solution Approach 1:
The light restrictive module extracts only the scattered lights within a specific angular range, filtering out lights from other directions. This selective extraction maintains sufficient light intensity for reliable detection while ensuring that only lights contributing to invariant speckle formation are captured, thus improving reliability.
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 capture of image invariant optical speckles, which are essential for precision optical pattern recognition and positioning, improving the resolution and sensitivity of devices like laser mice and three-dimensional fingerprint identification systems.
Implementation Method 1
the scattered light is further diffracted by the light restrictive module
Implementation Method 2
the scattered lights interfere with each other and produce a number of speckles on the sensor
Data Source
AI summary
An image invariant optical speckle capturing device and method. A highly coherent light is used to illuminate a surface and is scattered by the surface, and is captured from the direction with a ±10° from the angle of specular reflection. A light restrictive module is designed to confine the angular field of view of the sensor, when the speckle capturing device has a relative motion with respect to the surface, the speckle only move on the image but the shape and the intensity are almost keep constant, that is favorable for high accuracy optical pattern recognition and positioning.