Optical Navigation Device Illumination Optics Crosstalk Reduction
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Solution Overview
Problem
Optical mice face challenges in distinguishing surface features due to noise and crosstalk caused by light scattering from imperfections and dust on the illumination optics' output facets, as well as reflective properties of glass surfaces, which interfere with accurate tracking operations.
Innovation Solution
The optical navigation device relocates the illumination optics so that images of the output surfaces are outside the field of view of the image sensor, using adjustments in azimuth and zenith angles or optical path distances to minimize crosstalk, and optionally employs additional illumination elements to further reduce crosstalk and improve tracking accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the illumination optics are positioned to illuminate the tracking surface, then the tracking surface is properly illuminated for image capture, but images of the output surfaces are formed within the field of view of the image sensor causing crosstalk noise
Solution Approach 1:
The patent extracts the harmful element (images of output surfaces) from the field of view of the image sensor by repositioning the illumination optics. The output surfaces are positioned such that their reflected images fall outside the detection area, effectively removing the source of crosstalk noise while maintaining illumination functionality.
Solution Approach 2:
The patent resolves the contradiction by changing the spatial arrangement in multiple dimensions. The illumination optics are positioned at specific azimuth and zenith angles, and the output surfaces are located at distances that project images outside the field of view in the lateral dimension, while maintaining proper illumination in the optical path.
2Measurement precision
If the image sensor captures a wide field of view to detect surface features, then navigation accuracy is improved, but crosstalk from scattered light within the field of view increases
Solution Approach 1:
The patent removes the crosstalk source (output surface images) from the field of view, allowing the image sensor to maintain a wide field of view for detecting surface features without the contaminating effect of scattered light images within the detection area.
3Object-affected harmful factors
If the illumination optics are repositioned to exclude output surface images from the field of view, then crosstalk noise is reduced, but the complexity of optical alignment increases
Solution Approach 1:
The patent manages the alignment complexity by establishing specific parameter ranges for the position of output surfaces (azimuth angles, zenith angles, and distances) that ensure images fall outside the field of view. These parameter specifications provide a systematic approach to alignment rather than requiring complex adaptive mechanisms.
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 solution effectively reduces or eliminates crosstalk from the output surfaces, enhancing the ability to distinguish features on the tracking surface and improving navigation accuracy by keeping the images of the output surfaces outside the field of view of the image sensor.
Implementation Method 1
Many types of glass tracking materials have both primary (i.e., front) and secondary (i.e., back) surfaces 27 and 28 that reflect light from the light source 12 toward the image sensor 18.
Implementation Method 2
The illumination optics 14 direct light from the light source 12 toward the tracking surface 27.
Data Source
AI summary
An optical navigation device includes an image sensor, a light source, and illumination optics. The image sensor generates images of a tracking surface. The image sensor has a field of view via imaging optics interposed between the image sensor and the tracking surface. The light source generates light to illuminate a portion of the tracking surface. The illumination optics are interposed between the light source and the tracking surface to direct the light from the light source toward the tracking surface. The illumination optics include an output surface with a primary region illuminated above a threshold intensity. The illumination optics are located relative to the tracking surface so that an image of the output surface excludes the primary region from the field of view of the image sensor.