Rotatable Prism Cube Illumination for Metrology
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Solution Overview
Problem
The use of beam splitters in metrological machines for optical inspection leads to inadequate illumination due to light diversion and diminishment, particularly when both TTL surface and grid illumination systems are integrated, resulting in insufficient light levels for effective imaging.
Innovation Solution
The implementation of a rotatable cube assembly composed of two right-angle triangular prisms separated by an air gap, utilizing total internal reflection to redirect nearly 100% of TTL grid illumination and 90% of TTL surface illumination onto the work object, allowing for efficient switching between illumination modes using computer-controlled actuation systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a beam splitter is used to inject TTL illumination transverse to the optical axis, then illumination is provided, but light traveling along the optical axis is diverted and diminished
Solution Approach 1:
The beam splitter is divided into multiple segments or zones, each with different optical properties. Some segments are highly reflective while others are highly transmissive, allowing different portions of the light beam to be directed differently based on their intended destination or function.
Solution Approach 2:
Different regions of the beam splitter have different reflective/transmissive characteristics optimized for their specific function. The beam splitter provides locally optimized optical properties rather than uniform properties across the entire surface, allowing simultaneous efficient illumination and minimal light loss.
2Adaptability or versatility
If both TTL surface illumination and TTL grid illumination systems are integrated, then comprehensive illumination is achieved, but light levels become insufficient
Solution Approach 1:
The beam splitter's reflective and transmissive properties are made dynamically controllable, allowing the system to switch between different illumination modes (surface illumination, grid illumination, or both simultaneously) by adjusting the beam splitter's characteristics in real-time based on the required illumination configuration.
Solution Approach 2:
The optical parameters of the beam splitter (reflectivity, transmissivity) are changed dynamically to optimize light distribution. By adjusting these parameters, the system can provide sufficient light levels for both illumination types without requiring excessive total light output.
3Adaptability or versatility
If a 50/50 beam splitter is used to separate light beams, then both surface and grid illumination are provided, but neither system has adequate illumination
Solution Approach 1:
The beam splitter is designed with spatially varying optical properties, where different regions have different reflectivity/transmissivity ratios optimized for their specific illumination path requirements, rather than uniform 50/50 splitting across the entire aperture.
Solution Approach 2:
Instead of splitting light equally (50/50), the beam splitter provides partial or excessive action to one path while providing sufficient action to the other, allowing one illumination system to receive more than half the light while the other receives the remainder, optimizing overall illumination adequacy.
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 ensures nearly 100% of TTL grid illumination and 90% of TTL surface illumination are effectively utilized, addressing the issue of inadequate light levels and enabling high-quality imaging without deactivating existing light sources, while allowing for flexible illumination configurations and multiple light sources.
Implementation Method 1
The cube assembly (12) reflects substantially all of the light (21) from the second source of TTL illumination (9) due to total internal reflection
Implementation Method 2
Turning the cube a mere 12 degrees, past the critical angle, eliminates total internal reflection and allows almost all of the light from the TTL surface illumination system to pass through the cube
Data Source
AI summary
An illumination system using, in place of a more typical beam splitter, two right angle triangular prisms that are aligned to each other along their respective hypotenuses to form a cube, but without any reflective materials being used at their interface, and with the two halves separated by some distance so as to create an open/air gap between the two halves. When the upper/lower cube faces are normal to an optical axis of the illumination system, the cube structure reflects virtually all of the illumination from a transverse illumination source using total internal reflection so that said illumination is reflected out of the cube along the system's optical axis. However, rotating the cube structure past the critical angle eliminates total internal reflection and allows the cube to transmit almost all illumination entering the cube out of the cube parallel to the system's optical axis.