Dichroic Prism Assembly for Endoscope Multi-Channel Imaging
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Solution Overview
Problem
Current dichroic prism assemblies for endoscopes face challenges in measuring multiple light components simultaneously due to size constraints, mechanical complexity, and the need for air gaps, which limits their ability to achieve real-time imaging with high resolution and focus for both red and infrared signals.
Innovation Solution
The solution involves an inward splitting of the light path within the dichroic prism assembly, using non-internal reflections and movable wedge-shaped prisms to adjust path lengths, allowing for a compact design with sensors aligned on one side, eliminating the need for external air gaps and enabling simultaneous measurement of multiple wavelengths without time-switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If beam splitters are stacked to measure more light components simultaneously, then the number of measurable channels increases, but the system size and structural complexity increase
Solution Approach 1:
The patent combines multiple beam splitting functions into a single integrated dichroic prism assembly. The first prism P1 simultaneously performs wavelength separation for both the first channel (infrared fluorescence) and second channel (red light), eliminating the need for multiple stacked beam splitters and reducing overall system complexity.
Solution Approach 2:
The dichroic prism assembly is designed as a multi-functional optical component that can separate multiple wavelengths into multiple channels simultaneously. The first prism P1 with its specific coating configuration can direct different wavelength ranges to different sensors, making a single component perform what previously required multiple components.
2Area of moving object
If prisms are rotated 90 degrees to reduce their size, then the physical dimensions of individual prisms decrease, but the total focal length compensation becomes more difficult
Solution Approach 1:
The patent introduces a movable compensator prism P2 that operates along the optical axis (depth dimension) to compensate for focal length changes. This allows the main prism P1 to be optimized in the lateral dimensions (reduced size) while the compensator prism adjusts the optical path length in the axial dimension to maintain proper focus.
Solution Approach 2:
The compensator prism P2 is designed to be movable along the optical axis, allowing dynamic adjustment of the optical path length. This enables the system to compensate for focal length variations caused by wavelength differences or mechanical tolerances, maintaining image quality across different channels.
3Reliability
If air gaps are introduced between stacked prism elements for total internal reflection, then optical functionality is maintained, but mechanical stability and structural integrity deteriorate
Solution Approach 1:
The patent extracts the air gap requirement by using a different optical design approach. Instead of relying on total internal reflection that demands air gaps between stacked prisms, the invention uses a single integrated dichroic prism assembly with reflective coatings, eliminating the need for air gaps and thereby improving mechanical stability.
Solution Approach 2:
The patent replaces the mechanical air gap structure with an optical coating solution. The dichroic coatings on the prism surfaces provide the necessary wavelength-selective reflection without requiring physical separation, substituting a mechanical constraint with an optical property.
4Adaptability or versatility
If time-switching is used to measure infrared and red light sequentially, then a fourth channel can be added, but the frame rate is halved and motion artifacts increase
Solution Approach 1:
The patent enables continuous simultaneous measurement of multiple wavelengths by using parallel optical paths. The dichroic prism assembly separates different wavelengths into different channels that reach different sensors simultaneously, allowing continuous acquisition of all channels at full frame rate without time-multiplexing interruptions.
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 approach reduces the overall size of the prism assembly, enhances mechanical stability, and allows for real-time imaging with high resolution and accurate focus for both infrared and visible wavelengths, achieving frame rates of at least 60 frames per second and 12-bit color imaging without infrared frame insertion artifacts.
Implementation Method 1
an optical coating C1 is placed and between prisms P6 and P7 an optical coating C2 is placed, each optical coating C1 and C2 having a different reflectance and wavelength sensitivity
Implementation Method 2
each of these stacked prism elements relies on total internal reflection, requiring an airgap between each of the assembled prism elements in order to function correctly
Implementation Method 3
The movable wedge-shaped prisms may be used to adjust the optical path length to match the path lengths in the other channels
Data Source
AI summary
An endoscope includes a dichroic prism assembly configured to receive light from an object image through an entrance face. The assembly includes a first prism and a further dichroic prism assembly for splitting light in three light components, the first prism having a cross section with corners designed so that an incoming beam is partially reflected twice inside and exits the first prism through an exit face towards a first sensor. The dichroic prism assembly includes a compensator prism between the first prism and the further dichroic prism assembly. A first path length travelled by the part of the incoming beam reflected twice inside the first prism towards the first sensor is the same as path lengths travelled by a part of the incoming beam entering the further dichroic prism assembly towards each of three sensors, accounting for adjustment for focal plane focus position difference in wavelengths at the sensors.