Optical Touch Measurement System Using Concave Mirror and 2D Mask
Solution Overview
Problem
Current positioning systems, such as multi-dimensional encoders and contact sensors, face limitations in achieving high precision and speed for nanometric displacements within a small volume, with resolution degrading as more encoders are used and being affected by factors like intensity fluctuations and thermal instability.
Innovation Solution
A measurement system using a fixed light source, a concave mirror on the mobile element, and a two-dimensional regular optical mask to enhance precision and speed by processing the image cast on a sensor, reducing the number of photons needed and power consumption, allowing detection of displacements as low as 1-5 nanometers with reduced thermal dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple encoders are used to achieve multi-dimensional positioning, then the positioning capability is improved, but the resolution degrades
Solution Approach 1:
The patent combines multiple measurement functions (3D position measurement) into a single optical measurement system with one sensor, eliminating the need for multiple separate encoders. The concave mirror and optical mask work together to encode spatial information from three dimensions into a two-dimensional sensor pattern, achieving multi-dimensional positioning without the resolution degradation that occurs when chaining multiple encoders together.
Solution Approach 2:
The patent transforms three-dimensional spatial information into a two-dimensional sensor pattern through the optical encoding system. The concave mirror focuses light from different 3D positions onto a 2D sensor plane, where the position is encoded in the spatial distribution of light intensity patterns rather than requiring sequential measurement along multiple 1D axes.
2Measurement precision
If a concave mirror and optical mask system is used to achieve high precision nanometric displacement detection, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The optical mask serves as an intermediary element that simplifies the overall system complexity. It encodes the three-dimensional position information into a two-dimensional light intensity pattern that can be directly read by a simple sensor array, eliminating the need for complex mechanical scanning or multiple sensors while maintaining nanometric precision.
Solution Approach 2:
The patent replaces complex mechanical positioning and measurement mechanisms with an optical system. Instead of using multiple mechanical encoders or scanning mechanisms, the system uses light reflection, optical encoding through a mask, and sensor detection to achieve nanometric displacement measurement, thereby reducing mechanical complexity.
3Speed
If intensity-based optical detection is used to detect position, then the measurement speed is improved, but the reliability decreases due to intensity fluctuations
Solution Approach 1:
Instead of measuring light intensity to determine position (which is susceptible to intensity fluctuations), the patent inverts the approach: it uses the spatial distribution and pattern of light intensity on the sensor to encode position information. The position is determined by analyzing the geometric pattern of light spots and their relative positions rather than their absolute intensities, making the measurement immune to intensity variations from power supply, temperature, or light source aging.
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 system achieves high precision and speed in detecting nanometric displacements with reduced power consumption and thermal dissipation, enhancing resolution and reliability while maintaining accuracy and stability.
Implementation Method 1
using a concave mirror, fixed to the mobile element, for reflecting the beam of light in direction to the sensor
Implementation Method 2
arranging on the path of the beam of light a fixed optical mask which comprises a two dimensional regular pattern, detecting and processing the image casted by the optical mask on the sensor
Data Source
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AI summary
The present invention discloses a method for determining the position and/or the displacement of a mobile element with respect to a fixed frame, consisting in using a fixed light source (1) emitting a beam of light, arranging the light source (1) with respect to the mobile element and with respect to the a sensor (2) in a way so as to induce an interaction between the beam of light and the sensor which depends on the position of the mobile element and using processing and computing means for providing a value of the position and/or the displacement of the mobile element in dependence of the output signal of the sensor, characterized in that it consists in using a concave mirror (3), integral in movement with the mobile element, for reflecting the beam of light in direction to the sensor, arranging on the path of the beam of light a fixed optical mask (4) which presents a two dimensional regular pattern interlaced with an absolute code, detecting and processing the image casted by the optical mask on the sensor, computing the displacement value of the said image on the said sensor and using the computed displacement value for computing and providing the position and/or the displacement in at least one direction of the mobile element in dependence of the image's displacement.