Ophthalmic Lens Micro-etching Detection with Incoherent Light
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Solution Overview
Problem
Existing optical instruments for identifying and localizing micro-engravings on ophthalmic lenses suffer from blurry images and significant light flux loss due to the use of spatially coherent light and small objective apertures, which limits their effectiveness in accurately detecting and visualizing these micro-features.
Innovation Solution
The optical instrument employs a backscatterer instead of a reflector, using a point light source with a wavelength between 700 and 1000 nm and a diameter smaller than one fiftieth of the collimating member's focal length, resulting in a spatially incoherent light beam that is not affected by micro-engravings, allowing for a larger objective aperture and improved contrasted imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a spatially coherent light beam is used to illuminate the ophthalmic lens, then micro-engravings can be visualized through phase-contrast technique, but the images become blurry and light flux is significantly lost
Solution Approach 1:
The patent changes the coherence parameter of the light beam from spatially coherent to spatially incoherent. This is achieved by using a light source with a large diameter (greater than one fiftieth of the focal length) that creates an incoherent beam after the collimating member, thereby eliminating the blurring and light flux loss associated with coherent light while maintaining micro-engraving visibility through phase-contrast technique
2Stability of the object's composition
If a small objective aperture is used in the image-capturing unit, then spatial coherence is maintained, but light flux loss increases and imaging quality deteriorates
Solution Approach 1:
The patent changes the coherence parameter of the light beam from spatially coherent to spatially incoherent by using a light source with a large diameter (greater than one fiftieth of the focal length). This parameter change allows the use of a larger objective aperture without compromising spatial coherence, thereby reducing light flux loss and improving imaging quality
3Device complexity
If a reflector is used to send back light, then the optical path is simplified, but the light beam remains spatially coherent causing micro-engraving interference
Solution Approach 1:
The patent introduces a diffuser as an intermediary element between the collimating member and the ophthalmic lens. This diffuser converts the spatially coherent light beam into a spatially incoherent beam, thereby eliminating micro-engraving interference while maintaining a relatively simple optical path. The diffuser acts as a mediator that modifies the light's coherence properties without significantly complicating the overall system
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 configuration enables clear, contrasted imaging of micro-engravings with reduced light flux loss, enhancing the accuracy and visibility of micro-engravings on ophthalmic lenses, facilitating precise identification and localization.
Implementation Method 1
said point light source has a wavelength λ comprised between 700 and 1000 nm
Implementation Method 2
a collimating member, said point light source being placed at a first focal point of this collimating member so that light issued from the point light source becomes, after having passed through the collimating member, a beam of collimated light
Implementation Method 3
said member for sending back light is a backscatterer; said objective of said image-capturing unit is focused in order to deliver to the image-exploiting unit images of the backscatterer
Data Source
AI summary
An optical instrument includes: a collimation element (30) having a focal distance; a point light source (25-27) with a wavelength of between 700 and 1000 nm and a diameter less than or equal to a fiftieth of the focal distance, placed at a first focus of the collimation element, so that the light becomes a beam (20) of collimated light; a backscatterer (12); a support for receiving an ophthalmic lens (14), with the collimation element, support and backscatterer being placed so that the beam of collimated light encounters the lens location (15) where micro-etching is present; an image analyzing element (32) and an image capture element (31) linked to the analyzing element and including an objective lens (35) placed at a second focus of the collimation element, which objective lens is developed to provide the analyzing element with images of the backscatterer in order to identify and locate the micro-etching.