Illuminance Sensor with Infrared Cut-off Filter and Switching Section
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Solution Overview
Problem
Conventional sensors fail to integrate illuminance and proximity functions effectively, with issues including infrared light reception in illuminance sensors, fixed spectral characteristics, and separate components for illuminance and proximity sensing.
Innovation Solution
A single-unit sensor with a first light receiving element having both visible and infrared light receiving P-N junctions, an infrared cut-off filter, and a switching section to switch spectral characteristics, allowing the sensor to selectively receive visible or infrared light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an infrared transmissive filter is used to remove infrared components for illuminance sensing, then the spectral characteristic near luminous efficacy is achieved, but infrared light cannot be received for proximity sensing
Solution Approach 1:
The light receiving element is divided into two distinct P-N junctions: a first P-N junction for receiving visible light and a second P-N junction for receiving infrared light. This segmentation allows each junction to be optimized for its specific wavelength range, enabling the sensor to achieve both illuminance sensing (with infrared removal) and proximity sensing (with infrared detection) functions simultaneously within a single integrated device.
Solution Approach 2:
The sensor achieves multi-functionality by integrating both visible light receiving and infrared light receiving capabilities in a single device. The first P-N junction processes visible light for illuminance measurement, while the second P-N junction processes infrared light for proximity detection, allowing the sensor to serve dual purposes without requiring separate components.
2Measurement precision
If separate illuminance sensor and proximity sensor are used, then each sensor can have optimized spectral characteristics, but the device size increases
Solution Approach 1:
The patent merges the functions of separate illuminance and proximity sensors into a single integrated sensor device. By combining multiple P-N junctions with different spectral response characteristics within one substrate, the design achieves the spectral optimization of separate sensors while reducing the overall device volume and enabling compact integration in mobile terminals.
Solution Approach 2:
Multiple light receiving elements with different spectral characteristics are nested within a single sensor structure. The first and second P-N junctions are integrated in a nested configuration on the substrate, allowing each junction to maintain its optimized spectral characteristics while occupying minimal space within the unified sensor package.
3Device complexity
If a single light receiving element is used for both illuminance and proximity sensing, then device complexity is reduced, but spectral characteristic control becomes difficult
Solution Approach 1:
Different regions of the sensor substrate are designed with locally optimized properties. The first P-N junction is configured with specific characteristics for visible light response, while the second P-N junction is configured with different characteristics for infrared light response. This local quality differentiation allows each region to excel at its specific function while maintaining overall structural simplicity.
Solution Approach 2:
The sensor employs a composite structure combining multiple P-N junction types with different spectral response properties. By integrating these composite light receiving elements with distinct characteristics on a single substrate, the design achieves precise spectral control for both visible and infrared wavelengths without requiring complex external filtering or multiple separate devices.
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
Enables a single-unit sensor to achieve a spectral characteristic near luminous efficacy for illuminance sensing and detect proximity by eliminating infrared radiation, while inhibiting visible light interference for proximity sensing.
Implementation Method 1
a first light receiving element section which is provided in a substrate and has (i) a first visible light receiving P-N junction having a visible light spectral characteristic and (ii) a first infrared light receiving P-N junction having an infrared light spectral characteristic
Implementation Method 2
an infrared cut-off filter which removes an infrared component from light
Data Source
AI summary
In order to provide a single-unit sensor which serves as both an illuminance sensor and a proximity sensor, the sensor (1) includes a light receiving element section (E1), an infrared cut-off filter (IRcutF), and a switching section (SWS) for switching spectral characteristics of the light receiving element section (E1). The infrared cut-off filter (IRcutF) has an opening, and an infrared light receiving P-N junction (PDir) is provided at a location deeper in a substrate than a visible light receiving P-N junction (PDvis).