Reflective Fresnel Lens Illumination for Microscopy
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Solution Overview
Problem
Existing illumination devices for 3D surface measuring apparatuses using the focus variation principle suffer from low efficiency, non-uniform illumination, and light loss due to refractive Fresnel lenses, leading to measurement inaccuracies and highlights that can cause incorrect measurements.
Innovation Solution
The illumination device employs a reflective Fresnel lens and annular converging lenses formed by adjacent segments to achieve higher numerical aperture, reducing light loss and ensuring uniform illumination across a wide angle range, with SMD light-emitting diodes arranged in the focal points of the converging lenses for enhanced efficiency and homogeneity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a transmitting Fresnel lens is used to focus light, then the illumination aperture can be large, but significant light loss occurs due to refraction, reducing illumination efficiency
Solution Approach 1:
The patent inverts the conventional transmitting Fresnel lens approach by using a reflective Fresnel lens instead. The reflective lens has its prism structure oriented with lens vertices at the light entry side, causing light to reflect off the inclined surfaces rather than refract through them. This reflection mechanism dramatically reduces light loss while maintaining the ability to achieve large illumination aperture through the same Fresnel lens geometry.
2Illumination intensity
If conventional light sources like halogen lamps are used, then sufficient illumination can be achieved, but the devices are expensive, consume high power, generate excessive heat, and have large dimensions
Solution Approach 1:
The patent changes the fundamental parameter of the light source from conventional thermal sources (halogen lamps) to solid-state LED technology. This parameter change enables achieving the same illumination intensity with dramatically reduced power consumption and heat generation. The reflective Fresnel lens further enhances this by efficiently directing the LED light output, ensuring that the lower-power LED source achieves sufficient illumination through improved optical efficiency.
3Volume of moving object
If the illumination device is made compact to reduce interference with the sample, then the operating distance from the objective to the sample may be reduced
Solution Approach 1:
The patent segments the illumination device into modular components: a compact ring light housing containing the LED array, a separate reflective Fresnel lens, and mounting mechanisms. This segmentation allows the illumination elements to be arranged in a compact annular configuration around the objective, minimizing the overall device volume and interference with the sample while maintaining adequate operating distance through optimized spatial arrangement.
4Adaptability or versatility
If light is directed across a large angle range to illuminate both flat and steep areas, then non-uniform illumination and disturbing highlights may occur
Solution Approach 1:
The patent applies local quality by orienting the prism structure of the reflective Fresnel lens with lens vertices at the light entry side. This specific orientation creates localized reflection angles that distribute light more uniformly across the sample surface. The inclined surfaces of the prism structure are angled to redirect light from high-angle illumination into more uniform distribution patterns, reducing highlights on steep areas while maintaining adequate illumination of flat areas.
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 significantly increases light yield, reduces heat generation, and provides more even illumination, minimizing measurement errors and allowing for precise measurement of complex samples with steep edges and reflective surfaces.
Implementation Method 1
At the at least one Fresnel lens, lens vertices of a prism structure are oriented in a reflective arrangement at a light exit side of the Fresnel lens
Implementation Method 2
the light beams emitted by the light-emitting diodes first impinge on the converging lenses and then impinge further on the Fresnel lens as essentially parallel-directed entry light beams
Data Source
AI summary
An illumination device for a microscope or an optical 3D surface measuring apparatus, more particularly according to the principle of focus variation. The illumination device includes LEDs arranged in a planar fashion, and an illumination optical unit for imaging the illumination spectrum onto an object to be examined. The illumination optical unit includes an arrangement of converging lenses and one Fresnel lens, and the light beams emitted by the LEDs firstly impinge on the converging lenses and then impinge in a parallel-directed manner on the Fresnel lens. The Fresnel lens is oriented in reflective arrangement such that lens vertices of a prism structure are arranged at a light exit side of the Fresnel lens, facing away from the converging lenses. The converging lenses are formed by annular segments, and adjacent annular segments adjoin one another in a planar fashion at a segment side surface.