Circular Colour Chart Plate for Endoscope Calibration
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Solution Overview
Problem
Conventional colour charts are not suitable for calibrating endoscope camera systems with built-in light sources due to issues like automatic gain control, non-uniform illumination, alignment challenges, crosstalk, and incorrect chart selection, which affect colour accuracy and precision.
Innovation Solution
A circular colour chart plate with a specularly reflective surface, radial patches, and a central achromatic bright field manages automatic gain control, reduces saturation, and facilitates alignment, while unsymmetrical markings and a QR code aid in orientation and identification, and a container unit with rotatable holders stabilizes the endoscope arm for precise calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional rectangular colour chart is used for calibration, then the chart provides standard colour patches for calibration, but the non-uniform illumination from the built-in light source causes different illumination at centre and edge patches, leading to calibration errors
Solution Approach 1:
The patent applies a circular colour chart instead of a rectangular one, with colour patches arranged radially from the centre. This circular geometry matches the circular field of view of the endoscope camera and ensures that all patches are equidistant from the centre, receiving uniform illumination from the built-in light source, thereby eliminating illumination-induced calibration errors.
Solution Approach 2:
The patent positions colour patches at specific radial distances from the centre of the circular chart, ensuring that all patches are located in regions of uniform illumination. This local positioning strategy ensures that each patch receives consistent lighting conditions, optimizing the calibration process for endoscope cameras with built-in light sources.
2Measurement precision
If automatic gain control is activated to optimize image brightness, then the image becomes consistently bright, but the gain control causes saturation and clipping of pixel values, leading to incorrect colour reproduction
Solution Approach 1:
The patent includes a central achromatic bright field with high luminance that is specifically designed to prevent saturation of the automatic gain control system. This central field acts as a preliminary countermeasure by providing a reference area that does not trigger excessive gain amplification, thereby preventing saturation and clipping of pixel values across the entire image, including the colour patches.
3Ease of operation
If the endoscope field of view is clipped to a circular shape by the optical system, then the image fits the circular housing, but alignment with a rectangular colour chart becomes difficult, losing the intuitive alignment approach
Solution Approach 1:
The patent uses a circular colour chart that matches the circular field of view of the endoscope camera. This geometric compatibility provides intuitive alignment, as the circular chart naturally fits within the circular field of view, eliminating the alignment difficulties associated with rectangular charts and clipped circular images.
4Measurement precision
If the optical path includes a tube or glass fibre with a lens, then the camera can be connected to the endoscope, but crosstalk inside the tube creates light shadow borders inside patches, artificially increasing calibration error
Solution Approach 1:
The patent positions colour patches radially at specific distances from the centre, ensuring they are located in regions where crosstalk effects are minimized. The radial arrangement and specific positioning ensure that light shadow borders created by crosstalk do not fall inside the patches, thereby maintaining calibration accuracy despite the presence of the optical tube or glass fibre.
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
Ensures accurate and consistent colour calibration by preventing saturation, enhancing alignment, and reducing crosstalk, leading to improved colour reproduction and stability across different endoscope systems.
Implementation Method 1
the circular colour chart plate (1) has a mainly specularly reflective surface facing the camera
Data Source
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Figure 3a~3b
Figure 4a~4b
AI summary
A system and method are described for calibrating an endoscope, considering having the camera and the light source close to each other in an enclosed environment. In one embodiment of the present invention there is a colour chart plate provided, being specularly reflecting, having radially extending colour patches, and a circular central achromatic bright field that can handle the automatic gain control of the camera. The colour chart can be mounted into a container unit having mechanically connected holders to support the endoscope arm.