Spectroscopic System Using Tilted Prism and Cholesteric Liquid Crystal Diffraction
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Solution Overview
Problem
Existing spectroscopic systems using cholesteric liquid crystal layers face challenges in reducing size due to the need for detectors on the light incidence side to capture dispersed light.
Innovation Solution
A spectroscopic system incorporating a prism with a tilted second surface and a liquid crystal diffraction element featuring a cholesteric liquid crystal layer with a specific liquid crystal alignment pattern, allowing dispersion target light to be incident, reflected, totally reflected, and emitted from the second surface of the prism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a cholesteric liquid crystal layer is used as a diffraction element to disperse light, then light dispersion capability is improved, but the detector must be disposed on the light incidence side which increases system size
Solution Approach 1:
The patent inverts the conventional optical path by using a tilted prism surface to reflect dispersed light back through the liquid crystal diffraction element. Instead of placing the detector on the incidence side (conventional approach), the light path is reversed so that dispersed light returns through the same element and exits toward the incidence side, allowing detector placement on the opposite side and reducing system size.
Solution Approach 2:
The patent introduces a tilted prism surface at a specific angle (4° or more) to change the spatial dimension of the optical path. This tilting creates a new geometric relationship that enables light to be reflected back through the diffraction element at a different angle, allowing the detector to be positioned on the opposite side rather than on the incidence side.
2Ease of operation
If the tilt angle of the second surface is increased to enable total reflection and back-propagation of light, then light path control is improved, but optical loss increases
Solution Approach 1:
The patent optimizes the tilt angle parameter of the second surface to be 4° or more, which is the minimum angle required to achieve total internal reflection for the specific wavelength range and refractive index configuration. By setting the angle at this threshold value rather than using a larger angle, the patent achieves adequate light path control while minimizing optical loss associated with larger tilt angles.
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 enables the reduction in size of the spectroscopic system by allowing dispersed light to be emitted from the second surface, facilitating the placement of detectors on the opposite side and reducing system size.
Implementation Method 1
the diffraction angle by the cholesteric liquid crystal layer having the liquid crystal alignment pattern depends on the wavelength of incident light. Accordingly, there is a possibility that the cholesteric liquid crystal layer having the liquid crystal alignment pattern can be used as a member that disperses light.
Implementation Method 2
totally reflects the reflected light from a surface of the liquid crystal diffraction element opposite to the prism side
Data Source
AI summary
Provided a spectroscopic system where a reduction in size can be achieved. The spectroscopic system includes an optical element, in which the optical element include a prism and a liquid crystal diffraction element disposed on a first surface of the prism directly or with another layer interposed between the prism and the liquid crystal diffraction element, the prism has a second surface tilted with respect to the first surface, a tilt angle of the second surface is 4° or more, the liquid crystal diffraction element includes a cholesteric liquid crystal layer, the cholesteric liquid crystal layer has a liquid crystal alignment pattern in which an orientation of an optical axis derived from a liquid crystal compound changes while continuously rotating in at least one in-plane direction, in a case where a length over which the orientation of the optical axis in the liquid crystal alignment pattern rotates by 180° is set as a single period, a length of the single period is 0.1 to 1.4 μm, and the spectroscopic system allows dispersion target light to be incident into the liquid crystal diffraction element side, reflects the incident light from the liquid crystal diffraction element, totally reflects the reflected light from a surface of the liquid crystal diffraction element opposite to the prism side, allows the totally reflected light to be incident into the prism, and emits the dispersed light from the second surface.