Cholesteric Liquid Crystal Optical Element for Infrared Sensor Noise Reduction
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Solution Overview
Problem
Existing sensors face challenges in reducing size and noise while effectively gathering infrared light, particularly in narrow spaces, due to the complexity and size of current configurations, which are prone to external light interference and have low signal-to-noise ratios.
Innovation Solution
A thin optical element using a cholesteric liquid crystal layer with a selectively reflective pattern that rotates the optical axis continuously, allowing only desired wavelength infrared light to be reflected and transmitted, thereby simplifying the device configuration and reducing noise from external light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a plane light source is used to simplify the device configuration, then the device size is reduced, but the amount of light incident into the light-receiving element becomes insufficient and the signal-to-noise ratio decreases
Solution Approach 1:
The patent combines a light-gathering function with a wavelength-selective reflection function into a single optical element. This optical element integrates the capabilities of both a light concentrator and a spectral filter, allowing the plane light source configuration to maintain both simplicity and high signal-to-noise ratio by efficiently gathering infrared light while blocking external light.
Solution Approach 2:
The optical element performs multiple functions simultaneously: it gathers light from a wide area, selectively reflects infrared wavelengths, and blocks external visible light. This multi-functionality allows the simplified plane light source configuration to achieve both compact size and high measurement precision without requiring separate components for each function.
2Measurement precision
If a concave mirror is used to increase light gathering power, then sufficient infrared light can be gathered, but the mirror becomes thick and the sensor size increases making it difficult to install in narrow places
Solution Approach 1:
The patent uses a thin-film optical element with wavelength-selective reflective properties instead of a thick concave mirror. This thin film structure achieves light gathering power through optical interference and selective reflection mechanisms rather than relying on the geometric curvature of a thick mirror, thereby maintaining compact sensor size suitable for narrow installation spaces.
Solution Approach 2:
The patent changes the optical parameters by using a plane light source combined with a wavelength-selective optical element instead of a curved mirror. This parameter change allows the system to achieve sufficient light gathering power through the selective reflection and transmission properties of the optical element rather than through geometric concentration, reducing the overall sensor volume.
3Measurement precision
If filters are provided to reduce noise from external light, then the signal-to-noise ratio improves, but the configuration becomes complicated and the size increases
Solution Approach 1:
The patent merges the wavelength-selective filtering function with the light-gathering function into a single integrated optical element. This eliminates the need for separate filters in the optical path, maintaining high signal-to-noise ratio by blocking external light while preserving the simplicity of the overall sensor configuration.
Solution Approach 2:
The optical element serves multiple purposes: it acts as both a light-gathering component and a spectral filter. By providing wavelength-selective reflection for infrared light and blocking external visible light, it performs both signal enhancement and noise reduction in a single component, avoiding the complexity of multiple separate filtering elements.
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
The solution enables a compact, high-performance sensor with improved signal-to-noise ratio by selectively reflecting infrared light and allowing other wavelengths to pass through, reducing the need for filters and maintaining sufficient light gathering power without a curved surface.
Implementation Method 1
a cholesteric liquid crystal layer that is obtained by immobilizing a cholesteric liquid crystalline phase, in which the cholesteric liquid crystal layer has a liquid crystal alignment pattern in which a direction of an optical axis derived from a liquid crystal compound changes while continuously rotating
Implementation Method 2
a cholesteric liquid crystal layer that is obtained by immobilizing a cholesteric liquid crystalline phase
Data Source
AI summary
An object is to provide an optical element that is thin and can gather and reflect light in a specific wavelength range in a predetermined direction, and a sensor including the above-described optical element. The optical element includes a cholesteric liquid crystal layer, in which the cholesteric liquid crystal layer has a liquid crystal alignment pattern in which a direction of an optical axis derived from a liquid crystal compound changes while continuously rotating in at least one in-plane direction, and in a case where a length over which the direction of the optical axis rotates by 180° in the in-plane direction in which the direction of the optical axis changes while continuously rotating is set as a single period, the cholesteric liquid crystal layer has in-plane regions having different lengths of the single periods in the liquid crystal alignment pattern.