IR Cut Filter Absorber Reflector Design for Red Light Transmission
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Solution Overview
Problem
Conventional IR cut filters either fail to sufficiently block infrared light or inadequately transmit red visible light, leading to images that are either too dark due to insufficient red detection or plagued by ghosting effects from light reflection.
Innovation Solution
An IR cut filter comprising an infrared light absorber and reflector, where the absorber has 50% transmittance in the 620-670 nm range and the reflector has 50% transmittance in the 670-690 nm range, combined to achieve 50% transmittance in the 620-670 nm range and less than 5% transmittance at 700 nm, ensuring adequate red light transmission while blocking infrared light, thereby minimizing ghosting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick infrared absorbing glass is used to block infrared light, then infrared light blocking performance is improved, but red visible light transmittance deteriorates
Solution Approach 1:
The patent divides the infrared light blocking function into two separate components: an infrared light absorber (thick glass plate) and an infrared light reflector (thin film coating). This segmentation allows each component to be optimized independently - the absorber provides strong infrared blocking while the reflector maintains high red visible light transmittance, resolving the contradiction between blocking performance and light transmission.
Solution Approach 2:
The patent combines the infrared light absorber and infrared light reflector into a single integrated filter assembly. The absorber is positioned on the optical axis side and the reflector on the non-optical axis side, creating a composite structure that achieves both infrared blocking and red light transmission simultaneously, overcoming the limitations of using either component alone.
2Reliability
If an IR cut coating is used to block infrared light, then infrared light blocking performance is improved, but ghosting effects increase due to light reflection
Solution Approach 1:
The patent converts the harmful reflection effect of conventional IR cut coatings into a beneficial function. By designing the infrared light reflector with specific optical characteristics (50% transmittance at 670-690 nm), the reflection is controlled to block infrared light while minimizing ghosting effects. The reflector's selective transmittance properties transform the potentially harmful reflection into a useful infrared blocking mechanism without the negative side effects.
3Illumination intensity
If a thin infrared absorbing glass is used to maintain high red light transmittance, then red visible light transmittance is improved, but infrared light blocking performance deteriorates
Solution Approach 1:
The patent segments the infrared blocking function between a thick infrared light absorber (0.5-2.0 mm) and a thin infrared light reflector coating. This segmentation allows the absorber to provide the necessary infrared blocking performance while the reflector adds minimal thickness, achieving both high red light transmittance and effective infrared blocking without requiring the glass to be excessively thin or thick.
Solution Approach 2:
The patent creates a composite optical filter system combining the infrared light absorber (glass plate) and infrared light reflector (thin film coating). This composite structure leverages the complementary properties of both materials - the absorber's bulk absorption capability and the reflector's surface reflection properties - to achieve superior infrared blocking with minimal impact on red visible light transmission.
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 IR cut filter effectively transmits sufficient red visible light while blocking infrared light, resulting in brighter, more accurately colored images with reduced ghosting, and is thinner than conventional filters, maintaining high transmittance in the visible spectrum.
Implementation Method 1
an infrared light absorber that absorbs infrared light
Implementation Method 2
an infrared light reflector that reflects infrared light
Data Source
AI summary
An IR cut filter includes an infrared light absorber to absorb infrared light, and an infrared light reflector to reflect infrared light. The infrared light absorber has a light transmission property of 50% transmittance with respect to a wavelength in a wavelength band of 620 to 670 nm. The infrared light reflector has a light transmission property of 50% transmittance with respect to a wavelength in a wavelength band of 670 to 690 nm. The wavelength with respect to which the infrared light reflector has the 50% transmittance is longer than the wavelength with respect to which the infrared light absorber has the 50% transmittance. A combination of the infrared light absorber and the infrared light reflector provides a light transmission property of 50% transmittance with respect to a wavelength in the 620 to 670 nm wavelength band and less than 5% transmittance with respect to a 700 nm wavelength.