Fly-eye integrator for uniform epi-illumination
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Solution Overview
Problem
Conventional image measuring apparatuses using epi-illumination with small-area light sources like LEDs face issues of insufficient numerical aperture (NA) and uneven visual fields, particularly in the zoom low-power to high-power range, due to the limitations of LED light sources having smaller emission areas compared to halogen lamps.
Innovation Solution
The implementation of a fly-eye integrator with specific optical configurations, including an illumination relay lens, satisfies expressions that ensure adequate numerical aperture and even illumination across the zoom range, preventing NA deficiencies and visual field unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a small-area light source like LED is used in epi-illumination, then power consumption is reduced and color temperature is stabilized, but numerical aperture becomes insufficient and visual field becomes uneven
Solution Approach 1:
A fly-eye integrator is introduced as an intermediary optical element between the LED light source and the specimen. This integrator consists of multiple microlenses arranged in a matrix that redistributes the light from the small-area LED source to create uniform illumination across the entire visual field, effectively mediating between the limited light source area and the required illumination coverage
Solution Approach 2:
The fly-eye integrator divides the illumination function into multiple microlenses working in parallel. Each microlense contributes to illuminating a specific region, and their combined effect produces uniform overall illumination. This segmentation allows the system to overcome the limitations of the small LED source area by distributing its light output across multiple functional units
2Measurement precision
If zoom magnification is increased, then measurement precision is improved, but illumination uniformity deteriorates and numerical aperture becomes insufficient
Solution Approach 1:
The illumination system is designed to be dynamically adaptable to different zoom magnifications. The fly-eye integrator maintains effective illumination across the entire zoom range by its optical design that inherently provides uniform light distribution regardless of the magnification level, allowing the system to transition smoothly between low and high power observation
Solution Approach 2:
The system maintains illumination quality across varying zoom magnifications by using the fly-eye integrator's optical parameters that are optimized to provide consistent numerical aperture and uniformity. The integrator's microlense array configuration ensures that illumination parameters remain effective throughout the zoom range
3Reliability
If a halogen lamp is used instead of LED, then illumination area is increased and visual field uniformity is improved, but power consumption increases and color temperature stability decreases
Solution Approach 1:
The fly-eye integrator serves as an intermediary that enables small-area LED sources to achieve the illumination uniformity previously only attainable with large-area halogen lamps. By redistributing the LED's light output through its microlense array, the integrator compensates for the smaller source area without requiring a switch to higher-power halogen illumination
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 effectively prevents NA and visual field issues across the zoom range, enabling efficient and uniform illumination even with small-area light sources like LEDs, thereby enhancing the performance of image measuring apparatuses.
Implementation Method 1
a fly-eye integrator (3) integrated in an epi-illumination optical path of the objective lens (9)
Implementation Method 2
The epi-illumination includes a halogen lamp, a collector lens, and a condenser lens, and the object is illuminated in a telecentric manner through an objective lens
Data Source
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AI summary
A fly eye integrator satisfying the following Expression (1) is used for an illumination system: Φ×φ/f>M×DL×NAL..(1) Wherein Φ is a diameter of a circle inscribed to a fly-eye integrator injection end surface; φ is a diameter of a circuit inscribed to an end surface of each of lens elements constituting the fly-eye integrator; f is a focal distance of each of lens elements constituting the fly-eye integrator; M is a zoom multiplication ratio of the image formation optical system; DL is field-of-view diameter required for the zoom low multiplication unit of the DL image formation optical system; and NAL is a numerical aperture required for the zoom low multiplication side of the image formation optical system. Thus, it is possible to provide an image measuring apparatus which can prevent insufficient NA from the low multiplication to the high multiplication of zoom and irregularities of the field-of-view.