Optical Device for Bead Position Measurement
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Solution Overview
Problem
Existing methods for measuring the position of quasi-punctual objects, such as microbeads, require a time-consuming calibration phase and significant computing resources, limiting precision and the number of objects that can be measured simultaneously.
Innovation Solution
An optical device that measures the position of an object along a first axis without the need for a calibration phase, using an imaging system with a transmission mask and a separating arrangement to generate two spots on a detector, whose distance is proportional to the object's position, allowing for high-precision measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a calibration phase is used to determine bead positions by comparing diffraction patterns, then measurement precision is improved, but the time required for measurement increases significantly and computing resources are heavily consumed
Solution Approach 1:
The patent extracts only the essential measurement information by using a simplified optical setup with a transmission mask that creates distinct spot patterns. Instead of capturing and analyzing complete diffraction patterns requiring calibration, the system extracts position information from the relative positions of a limited number of spots (2-6 spots) formed by the mask, eliminating the time-consuming calibration phase while maintaining measurement precision.
Solution Approach 2:
The patent changes the measurement parameter from analyzing complete diffraction pattern characteristics to measuring the relative positions of discrete spots created by the transmission mask. This parameter change allows direct position calculation without calibration, as the spot positions are determined by the mask geometry and light source configuration rather than requiring reference measurements.
2Measurement precision
If a calibration phase with multiple reference images is used, then measurement precision is improved, but device complexity increases due to the need for high precision nano-positioning stages
Solution Approach 1:
The transmission mask and optical system automatically generate the measurement signal (spot patterns) with built-in reference information. The relative positions of the spots inherently encode the bead position without requiring external calibration equipment or complex positioning stages. The system serves itself by using the optical configuration to provide both measurement and reference, eliminating the need for separate calibration hardware.
3Measurement precision
If a large number of pixels are used to image one bead, then measurement precision is improved, but the number of beads that can be analyzed simultaneously decreases
Solution Approach 1:
The patent segments the optical information into a limited number of discrete spots (2-6 spots) formed by the transmission mask, rather than using all pixels to capture a complete image of each bead. This segmentation reduces the data processing requirement per bead while maintaining precision, as only the positions of these few spots need to be tracked. Consequently, more beads can be analyzed simultaneously within the same field of view and processing capacity.
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 optical device achieves high-precision position measurement of objects without the need for calibration, simplifying the measurement process, reducing computational requirements, and enabling the simultaneous measurement of a large number of objects.
Implementation Method 1
an objective for collecting light radiations diffused by the object
Implementation Method 2
The size of the diffraction rings varies with the distance of the bead relative to the focal plane of the microscope
Data Source
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AI summary
The invention relates to an optical device (1) for measuring the position of an object (B) along a first axis (z), the object (B) being subjected to light radiations emitted by a light source (2, 21, 22), the optical device (1) comprising: - an imaging system (5) comprising an objective for collecting light radiations diffused by the object (B), the imaging system (5) having an optical axis (O) extending parallel to the first axis (z), - a transmission mask (8) having at least a first pair of apertures (81, 83) and a second pair of apertures (82, 84), the first pair of apertures and second pair of apertures being spaced from each other along a second axis (x), perpendicular to the first axis (z), the transmission mask dividing the radiation diffused by the object (B) into two first beams passing through the first pair of apertures (81, 83) and two second beams passing through the second pair of apertures (82, 84), while blocking a part of the radiations (R3) emitted by the light source which is not diffused by the object, - a detector (6) adapted for generating an image including a first spot (S1) and a second spot (S2) representative of the first part (R1) and second part (R2) of the radiations impacting the detector plane (61), wherein variation of the position of the object (B) relative to the object plane of the imaging system (5) along the first axis (z) spatial phase shifting of first interference patterns and of the second interference pattern relative to each other.