Optical Calibration System for Ophthalmic Instruments
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Solution Overview
Problem
Traditional methods for calibrating ophthalmic diagnostic instruments, such as slit beam systems, face challenges in mechanical alignment repeatability and accuracy, leading to errors in eye modeling due to misalignment and the need for multiple physical measurements.
Innovation Solution
An optical system calibration system and method utilizing a projector, imager, and calibration component with diffusely reflecting surfaces, allowing for calibration based on image data from a single set of images, independent of mechanical positioning variability, and enabling precise determination of slit beam profile and optical path parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional mechanical alignment apparatus and techniques are used for calibration, then calibration can be performed with known test plate positions, but mechanical alignment repeatability and accuracy deteriorate due to plate deformation and positioning challenges
Solution Approach 1:
The patent replaces the mechanical alignment system with an optical system. Instead of physically positioning test plates with mechanical fixtures, the invention uses a projector to create a calibration pattern and an imager to capture images of this pattern through the optical system being calibrated. The calibration is then performed computationally based on the captured images, eliminating mechanical positioning errors and deformation issues.
Solution Approach 2:
The invention creates an optical copy of the calibration target through projection rather than using a physical test plate. The projector generates a known calibration pattern that is imaged through the optical system, and this optical copy is then analyzed computationally. This eliminates the need for physical test plates and their associated mechanical alignment problems.
2Measurement precision
If multiple physical alignment measurements and image sets are taken, then comprehensive calibration data can be obtained, but the opportunity for error increases and time consumption increases
Solution Approach 1:
The calibration pattern is pre-projected onto the image sensor plane through the optical system before any measurements are taken. This preliminary projection establishes the reference geometry, and then all calibration measurements are derived from this single setup. This eliminates the need for multiple physical repositioning operations and reduces the total calibration time while maintaining completeness.
Solution Approach 2:
The invention combines multiple calibration measurements into a single imaging operation. Instead of taking multiple separate images with the test plate at different positions, the projector-imager system captures all necessary calibration information in one shot by projecting the calibration pattern through the entire optical path and capturing it on the sensor plane.
3Illumination intensity
If extra optical occluders are positioned along the slit beam path, then illumination intensity can be reduced, but device complexity increases
Solution Approach 1:
The calibration system uses the optical system's own imaging sensor to capture the calibration pattern directly at the sensor plane. This self-contained approach eliminates the need for external optical occluders or additional components to control illumination intensity, as the digital imaging system can handle the intensity range directly.
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 simplifies calibration, improves accuracy and repeatability, reduces time, and is integratable with other diagnostic equipment, providing precise physical and optical parameter measurements for ocular surfaces like the cornea and retina.
Implementation Method 1
an illumination projector (P) having an illumination projection axis lying in a plane
Implementation Method 2
a calibration component (C) comprising at least a first at least partially diffusely reflecting surface disposed along the projection axis
Implementation Method 3
an illumination imager (R) having an imaging axis lying in the plane. The receiver is positioned at a known receiver location coordinate
Data Source
AI summary
An optical system calibration system and method particularly suited for calibrating the optical slit planes in an ophthalmic diagnostic instrument. The system includes an illumination source projector, an illumination image receiver, and a calibration component all having known relative positions, orientations and physical and optical characteristics. The calibration component includes at least two separated, diffusely reflecting surfaces. Images of an exemplary slit illumination pattern projected onto the calibration component and formed on the diffusely reflecting surfaces are detected by the image receiver such as a video camera. Based upon camera image coordinates and triangulation parameters of the projector, the receiver, and the calibration component, the slit image positions on the image detector plane can be calibrated to the axially displaced, diffusely reflecting calibration component surface positions.