Offset Parabolic Mirror Optical Unit for Compact Sorting
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Solution Overview
Problem
Existing sorting machines for granular materials face challenges in achieving a compact design while maintaining high detection accuracy due to the need for large optical units and distant imaging, which leads to reduced detection efficiency and accuracy.
Innovation Solution
The use of an optical unit with an offset concave mirror and a lens, where the concave mirror's surface shape allows for control of chief rays to be parallel, diverging, or convergent, enabling efficient light gathering with a small lens diameter and reducing the device's size through optical path bending.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the camera is arranged at a position distanced far away from the downward trajectory to capture images from a direct downward view, then the detection coverage area is improved, but the device size increases and detection accuracy decreases
Solution Approach 1:
The patent introduces a reflective surface (mirror or prism) to change the optical path direction, allowing the camera to be positioned closer to the downward trajectory while still capturing images from a near-direct downward view. This dimensional change in light path enables compact device size without sacrificing detection accuracy or coverage area.
Solution Approach 2:
The reflective surface acts as an intermediary element between the camera and the target objects. It redirects light from the downward trajectory to the camera sensor, enabling the camera to be positioned close to the trajectory while maintaining an effective direct downward viewing angle. This intermediary component resolves the contradiction between close positioning and optical performance.
2Measurement precision
If the viewing angle is narrowed to capture images from a direct downward view, then the detection accuracy is improved, but the measurement target area coverage decreases
Solution Approach 1:
By using a reflective surface to redirect light at an angle, the system achieves a narrow viewing angle in the optical path while maintaining wide coverage in the physical space. The mirror/prism redirects light from a wide field of view to a narrow angular range, allowing high detection accuracy without sacrificing area coverage.
Solution Approach 2:
The optical system uses asymmetric light path configuration where the reflective surface creates a non-symmetric transformation between the object space and image space. This allows the system to achieve a narrow angular field of view for high accuracy while the physical geometry maintains broad coverage area through the reflective transformation.
3Length of stationary object
If reflectors are inserted into the optical path to bend the optical axis and downsize the device, then the device size is reduced, but optical aberration and interference are introduced
Solution Approach 1:
The patent extracts and removes the problematic reflective surfaces (mirrors/prisms) from the optical path that cause aberration and interference. Instead, it uses the natural reflection from the downward trajectory objects themselves or employs alternative optical elements that do not introduce aberration, thereby maintaining optical quality while achieving device downsizing through other means.
Solution Approach 2:
The patent converts the potentially harmful effect of light path complexity into a benefit by using the downward trajectory reflection geometry itself as part of the optical system. The reflection from the chute or conveyor surface is utilized constructively to redirect light to the camera without introducing additional aberrating reflective elements, thus achieving compact design while maintaining optical quality.
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 allows for a compact and cost-effective sorting machine with improved detection accuracy and reduced size, avoiding optical aberrations and interference from a wide field of view.
Implementation Method 1
a lens (3) is arranged to face an offset concaved mirror (2)... beams propagated from any object points on the object surface are reflected by the offset concaved mirror (2)
Implementation Method 2
a lens (3) is arranged to face an offset concaved mirror (2)... the optical path from each object point to the lens (3) is conformable to a telecentric optical path
Data Source
AI summary
By using an offset parabolic concave mirror as a concave mirror, and arranging a lens having an entrance pupil at the geometric focal point of the offset parabolic concave mirror, a group of rays incident parallel to the optical axis of the offset parabolic concave mirror become chief rays which are telecentric with respect to an object plane orthogonal to the optical axis of the offset parabolic concave mirror, and diverging light from each object point on the object plane can be detected on a quadric image plane formed by the lens at the focal point of the offset parabolic concave mirror without blind spots. An image of the target object is detected after the beams reflected by the offset parabolic concave mirror are bent by the reflecting mirrors and made incident on the lens to reduce the size and cost of the device.