Wavelength Variable Optical Filter Stray Light Suppression
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Solution Overview
Problem
Existing wavelength variable filters face reliability issues due to stray light from the bonding film, which reduces their effectiveness in selectively extracting light of a predetermined wavelength.
Innovation Solution
A wavelength variable optical filter design featuring a first and second substrate with reflective films and a bonding film that is transparent in a predetermined wavelength range, with the bonding film's thickness set to avoid peaks in transmittance within the filter's wavelength range, ensuring no stray light interference and high reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a bonding film is used to join the pair of substrates, then the substrates can be effectively bonded together, but light of a predetermined wavelength may be incident as stray light from the bonding film onto between the pair of reflective films, reducing the reliability of the wavelength variable filter
Solution Approach 1:
The bonding film is designed with different optical properties for different wavelength ranges. It has high transmittance for wavelengths outside the measurement range and low transmittance for wavelengths within the measurement range, achieving local quality differentiation to prevent stray light while maintaining bonding function
Solution Approach 2:
The thickness of the bonding film is specifically controlled to create interference effects that produce minima in the transmittance spectrum at wavelengths corresponding to the filter's measurement range. By changing the thickness parameter, the optical path length is adjusted to eliminate stray light peaks at critical wavelengths
2Illumination intensity
If the bonding film is made transparent in a predetermined wavelength range, then light transmission is improved, but peaks in transmittance may occur within the filter's wavelength range, causing stray light interference
Solution Approach 1:
The bonding film's transparency, which could potentially cause stray light problems, is converted into a benefit by carefully controlling its thickness to create interference minima at critical wavelengths. The same optical transparency that allows light transmission is used to create destructive interference for stray light at measurement wavelengths
Solution Approach 2:
The bonding film's thickness is pre-calculated and controlled during manufacturing to establish the desired interference pattern before the filter is assembled and used. This preliminary design ensures that transmittance minima occur at wavelengths corresponding to the filter's measurement range, preventing stray light issues from the outset
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 effectively suppresses stray light, enhancing the reliability of the wavelength variable optical filter by ensuring the optical path through the bonding film has no peak transmittance within the measured wavelength range, thereby improving the filter's performance and accuracy.
Implementation Method 1
an optical path extending through the first reflective film, the bonding film, and the second reflective film has transparency with respect to the light in the predetermined wavelength range, the optical path having no peak of transmittance with respect to a wavelength range measured by the wavelength variable filter
Data Source
AI summary
The wavelength variable optical filter includes a first substrate, a second substrate, and a bonding film, the bonding film is in contact with a first reflective film and a second reflective film to thus join the first substrate with the second substrate, the bonding film has transparency with respect to light of a predetermined wavelength range, and an optical path extending through the first reflective film, the bonding film, and the second reflective film has transparency with respect to light of the predetermined wavelength range and has no peak of transmittance with respect to a wavelength range measured by the wavelength variable filter.