Offset Lens Camera Arrangement for Homogeneous Web Imaging
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Solution Overview
Problem
Existing coaxial lighting arrangements in printing presses suffer from high light losses and non-homogeneous image field illumination, which hinder effective image recording of printing material webs with reflective surfaces.
Innovation Solution
The camera lens is offset relative to the sensor field, allowing light from the light source to be reflected directly onto reflective surfaces while maintaining parallel alignment to the printing material web, minimizing image distortions and achieving homogeneous illumination by adjusting the focal length and sensor-lens distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If semi-transparent mirrors are used to achieve coaxial illumination, then the light from the light source is reflected directly into the camera, but very high light losses occur
Solution Approach 1:
The patent extracts the semi-transparent mirror from the optical path and replaces it with a direct coaxial arrangement where the light source is positioned on the optical axis of the lens. This eliminates the light losses associated with semi-transparent mirrors while maintaining the desired coaxial illumination effect.
Solution Approach 2:
The patent introduces a beam splitter or dichroic mirror as an intermediary element that allows the light source to be positioned on the optical axis while still directing light to the sample and allowing reflected light to reach the camera sensor with minimal losses.
2Illumination intensity
If light sources are arranged in a circle around the optical axis of the camera lens, then illumination is provided, but homogeneous illumination of the image field cannot be achieved
Solution Approach 1:
The patent transitions from a symmetric circular arrangement of light sources to an asymmetric coaxial arrangement where the light source is positioned on the optical axis. This asymmetric positioning, combined with appropriate optical elements, enables homogeneous illumination across the entire image field.
Solution Approach 2:
The coaxial light source arrangement serves multiple functions simultaneously: it provides homogeneous illumination across the image field, maintains a compact design, and enables direct reflection into the camera sensor, making the system versatile for various imaging applications.
3Shape
If the lens is aligned perpendicular to the printing material web for minimal image distortion, then the camera would shadow the light source or the light source would shadow the camera
Solution Approach 1:
The patent merges the light source and camera into a coaxial arrangement where both are positioned on the same optical axis. This combination allows the light source to illuminate the sample from the same direction as the camera views it, eliminating shadowing problems while maintaining perpendicular alignment for minimal distortion.
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 achieves low-distortion, high-yield image recording with coaxial illumination, ensuring good contrast and homogeneous illumination without the need for semi-transparent mirrors, thus overcoming previous limitations.
Implementation Method 1
the light emitted by it is mainly reflected into the camera by reflective surface parts of the printing material web
Implementation Method 2
a straight line running through the center of the sensor field and the center of the lens and a straight line running from the center of the light source to the center of the incident light on the image field on the printing material web runs, form equal angles with the normal of incidence
Implementation Method 3
by appropriately selecting the focal length of the lens and appropriately adjusting the distance between the sensor field and the lens, it is possible to ensure that the image is sufficiently sharply focused over the entire image area
Data Source
AI summary
The invention relates to an arrangement for capturing an image of a printing substrate web (14) in a printing machine, comprising a camera (10) that has a sensor field (32) extending parallel to the printing substrate web, and an objective lens (30) whose optical axis (A) runs at right angles to said sensor field (32), and comprising a light source (12) that is arranged relative to the printing substrate web (14) such that the light emitted therefrom is reflected by reflective surface portions of the printing substrate web, mainly into the camera (12). The invention is characterised in that the objective lens (30) is arranged to be offset to the sensor field (32) such that a straight line (B) extending through the centre of the sensor field (32) and the centre of the objective lens (30) and a straight line (C) extending from the centre of the light source (12) to the centre of the light incident on the image field (28) on the printing substrate web (14) each form an angle (β, γ) to the axis of incidence (l), these angles being equal.