Telecentric Optical System for Transparent Object Measurement
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Solution Overview
Problem
Existing information acquisition apparatuses face challenges in achieving high contrast and detailed image acquisition of objects, particularly when dealing with transparent objects, due to limitations in optical system design and aberration correction, leading to difficulties in accurately capturing the size and shape of objects.
Innovation Solution
The apparatus incorporates a both-side telecentric optical system with specific lens configurations and conditional expressions to correct aberrations, allowing for oblique illumination and improved image formation, which includes a light source, illuminating optical system, and image pickup element, positioned to form optical images with varying wavelengths to capture detailed object information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional optical system is used for image acquisition, then the apparatus structure is simple, but the image contrast and measurement precision are insufficient for transparent objects
Solution Approach 1:
The optical system is segmented into distinct functional units: an illuminating optical system with a light source for oblique illumination, and an image forming optical system with multiple lens units. The incidence-side lens unit includes a positive lens and negative lens, while the emergence-side lens unit includes a positive lens and negative lens, with an aperture stop positioned between them. This segmentation allows each unit to be optimized for its specific function while maintaining overall system performance.
Solution Approach 2:
Different regions of the optical system are designed with different optical properties to address specific local requirements. The incidence-side lens unit uses a positive lens followed by a negative lens to control light convergence and reduce aberrations at the object side. The emergence-side lens unit uses a positive lens followed by a negative lens to control light divergence and improve image quality at the image side. The aperture stop is strategically positioned to control the cone of light and reduce spherical aberration.
2Illumination intensity
If phase-contrast microscopy or differential interference contrast microscopy is used to improve contrast, then transparent objects can be observed with favorable contrast, but the device complexity and cost increase
Solution Approach 1:
Instead of using complex phase-contrast or differential interference contrast microscopy systems that require specialized optical components like phase plates or polarizers, this invention inverts the approach by using a simplified oblique illumination system combined with a carefully designed image forming optical system. The oblique illumination from the light source, combined with the specific lens configuration and aperture stop positioning, achieves high contrast for transparent objects without requiring the complex additional components of traditional contrast-enhancing microscopy methods.
3Manufacturing precision
If the image forming optical system uses multiple lenses to correct aberrations, then image quality improves, but the apparatus size and manufacturing cost increase
Solution Approach 1:
The optical system employs an asymmetric configuration where the incidence-side lens unit and emergence-side lens unit have different designs optimized for their respective positions. The incidence-side unit uses a positive lens followed by a negative lens with specific focal lengths and spacing, while the emergence-side unit uses a positive lens followed by a negative lens with different parameters. This asymmetric design allows effective aberration correction while minimizing the overall optical path length and apparatus size.
Solution Approach 2:
The aperture stop is positioned preliminarily between the incidence-side lens unit and emergence-side lens unit to pre-control the light cone before it reaches the image-forming lenses. This preliminary action of the aperture stop reduces spherical aberration and controls the angle of incident light, allowing the subsequent lenses to work more efficiently with smaller dimensions while maintaining high image quality and aberration correction.
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 the acquisition of high-contrast optical images with reduced aberrations, allowing for precise determination of object size and shape, even when objects are transparent, while maintaining a compact and cost-effective apparatus design.
Implementation Method 1
the image forming optical system includes in order from an object side, an incidence-side lens unit having a positive refractive power, an aperture section, and an emergence-side lens unit having a positive refractive power
Implementation Method 2
the illuminating section includes a light source and an illuminating optical system
Data Source
AI summary
An information acquisition apparatus includes an illuminating section, an image forming optical system, and an image pickup element. The image forming optical system includes an incidence-side lens unit having a positive refractive power, an aperture section, and an emergence-side lens unit having a positive refractive power. The incidence-side lens unit and the emergence-side lens unit include a plurality of positive lenses and at least one negative lens, and the following conditional expressions (1) to (9) are satisfied:−6<βd<−0.8 (1)−0.5<TL/|ENPL|<3.0 (2)−1.5<TL/|EXPL|<0.5 (3)0.001<|ΔCd|/Sim1/2<0.05 (4)0.04<|ΔdF|/Sim1/2<0.28 (5)3.5<|ΔCF|/|ΔCd|<38.0 (6)0<|ΔSAd|/|ΔCF|<0.27 (7)0<|ΔSAC|/|ΔCF|<0.16 (8)0<|ΔSAF|/|ΔCF|<1.1 (9).