Glass Block Dichroic Beamsplitter with Tilted Coating
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Solution Overview
Problem
Conventional cube dichroic beamsplitters suffer from poor spectral performance at high angles of incidence, leading to compromised beam separation and reduced system efficiency in spectroscopy applications, due to polarization differences and increased angle of incidence on embedded thin-film coatings.
Innovation Solution
A dichroic beamsplitter design featuring a composite prism with internal multilayer thin-film coatings, where light enters and exits at or near normal incidence, reducing the angle of incidence to below 45 degrees, thereby minimizing aberrations and beam shift, and enhancing spectral performance by using a glass block assembly with a specific geometric configuration of prism elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional cube dichroic beamsplitter with embedded thin-film coating is used, then beam separation and system stability are improved, but spectral performance deteriorates at high angles of incidence due to polarization differences
Solution Approach 1:
The patent applies asymmetry by tilting the thin-film coating surface relative to the prism faces. Instead of coating the hypotenuse surface at 45° incidence, the coating is applied to a surface tilted at a different angle (e.g., 30° or other non-standard angles), creating an asymmetric configuration that optimizes spectral performance while maintaining beam separation functionality
Solution Approach 2:
The patent changes the critical parameter of angle of incidence on the thin-film coating from the conventional 45° to a different angle that optimizes spectral performance. This parameter change reduces polarization effects and improves the beamsplitter's spectral characteristics while maintaining its beam separation function
2Measurement precision
If a plate dichroic beamsplitter is used, then spectral performance is improved, but optical aberrations and beam shift increase in imperfectly collimated light
Solution Approach 1:
The patent uses the prism elements as intermediary optical components that guide light to and from the tilted thin-film coating. The prisms serve as mediators between the input/output beams and the coating surface, enabling the system to achieve both good spectral performance and reduced optical aberrations by controlling the angle of incidence on the coating
Solution Approach 2:
The patent creates a composite optical system combining prism elements with a tilted thin-film coating. This composite structure integrates the aberration-correction properties of prisms with the spectral-separation properties of the dichroic coating, achieving both goals simultaneously
3Volume of moving object
If the thin-film coating is applied at 45° incidence, then compactness is improved, but spectral performance deteriorates due to increased angle of incidence and polarization effects
Solution Approach 1:
The patent changes the orientation of the thin-film coating surface relative to the optical axis, tilting it at an angle different from the conventional 45°. This dimensional reorientation of the coating surface allows optimization of spectral performance while maintaining a compact cube-shaped overall structure
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 design improves spectral separation and reduces performance requirements for emission filters, enhancing signal sensitivity and system efficiency by maintaining low aberrations and beam shift, even in imperfectly collimated light conditions.
Implementation Method 1
a multilayer thin-film dichroic beamsplitter coating formed on a fourth surface internal to the composite prism
Implementation Method 2
The beamsplitter reflects light of at least one wavelength band and transmits light of another wavelength band or bands
Implementation Method 3
Light of a first wavelength that is incident at a normal to the first planar surface is reflected at a 90-degree angle into an optical imaging path
Data Source
AI summary
A dichroic beamsplitter has a composite prism that has at least first and second prism elements that are coupled together along facing surfaces, wherein the respective facing surfaces of the first and second prism elements are equidistant from each other. The composite prism has a first flat external surface that lies within a first plane, a second flat external surface that lies within a second plane that is perpendicular to the first plane, a third flat external surface that lies within a third plane that is parallel to the second plane, and a coated surface internal to the composite prism and having a multilayer thin-film dichroic beamsplitter coating, wherein the coated surface lies within a fourth plane that intersects at least one of the first, second, and third planes at an angle that is less than about 25 degrees.