NIR cutoff filter for true color imaging sensors
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Ralf Biertümpfel
Dr. Ralf Biertümpfel studied Mechanical and Aerospace Engineering at the Technical University of Darmstadt (Germany) and Cornell University (USA). After his diploma and his Master of Engineering in 1996, he worked on a research project in the field of heat transfer and thermodynamics and finally earned his doctorate at the Technical University of Darmstadt in 2001. Since 2001, he works at SCHOTT AG in the fields of hot forming of glass and precision optics. At present, he is the application manager for optical filters.
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Steffen Reichel
Steffen Reichel studied Electrical Engineering at the University of Kaiserslautern and spend 7 months at the Michigan State University, Michigan, USA. After his diploma degree in 1996, he worked as a researcher at the University of Kaiserslautern working on his doctorate (Dr.-Ing.) in the field of optical communications (fiber optics, erbium-doped fiber amplifiers). In 1999, he joined Lucent Technologies working on fiber optical communications, erbium-doped, and Raman amplifiers. Since 2001, he works for SCHOTT on several fields of optics from imaging optics, fiber optics, waveguide optics, laser optics, illumination optics, and optical filters. He is a Senior Member of the IEEE and Member of the SPIE, and since 2013, he is a professor (honorary) for ‘Optics & Photonics’ at the University of Applied Science, Darmstadt, Germany. In addition, he is co-author in three books, has about 60 publications, and has 20 granted or applied patents.
Abstract
The function of a near-infrared (NIR) cutoff filter for imaging sensors is being described. The main purpose of the NIR cut filter is to obtain correct color recognition; therefore, the NIR filter is made of an absorbing filter glass and an interference coating. The absorbing filter glass is needed to minimize multiple reflections inside the lens system, which are the cause for ghost images. An additional interference coating enhances the function of the filter. Coating and filter glass are strongly dependent on each other. This requires high reproducibility and low tolerances of the filter glass and interference coating. In addition, features like inner quality – especially striae – and stability of the refractive index are important. A NIR cut filter may be designed as a flat plate or as a lens. Our analysis provides an estimation about striae level and variation of transmittance and their effect on image quality and color recognition. Furthermore, the use of an absorption filter glass as a lens (shrinking down the overall size) is discussed in terms of the influence on transmission and striae.
About the authors
Dr. Ralf Biertümpfel studied Mechanical and Aerospace Engineering at the Technical University of Darmstadt (Germany) and Cornell University (USA). After his diploma and his Master of Engineering in 1996, he worked on a research project in the field of heat transfer and thermodynamics and finally earned his doctorate at the Technical University of Darmstadt in 2001. Since 2001, he works at SCHOTT AG in the fields of hot forming of glass and precision optics. At present, he is the application manager for optical filters.
Steffen Reichel studied Electrical Engineering at the University of Kaiserslautern and spend 7 months at the Michigan State University, Michigan, USA. After his diploma degree in 1996, he worked as a researcher at the University of Kaiserslautern working on his doctorate (Dr.-Ing.) in the field of optical communications (fiber optics, erbium-doped fiber amplifiers). In 1999, he joined Lucent Technologies working on fiber optical communications, erbium-doped, and Raman amplifiers. Since 2001, he works for SCHOTT on several fields of optics from imaging optics, fiber optics, waveguide optics, laser optics, illumination optics, and optical filters. He is a Senior Member of the IEEE and Member of the SPIE, and since 2013, he is a professor (honorary) for ‘Optics & Photonics’ at the University of Applied Science, Darmstadt, Germany. In addition, he is co-author in three books, has about 60 publications, and has 20 granted or applied patents.
For the support of this work, we would like to acknowledge our colleagues Thea Marcoux, Bianca Schreder, Ralf Reiter, Volker Dietrich, Frank-Thomas Lentes, and Ulf Brauneck. We also thank the reviewer for his valuable comments.
References
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©2013 by THOSS Media & De Gruyter Berlin Boston
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Articles in the same Issue
- Masthead
- Masthead
- Views
- State of photonics-related industry in Japan: Digital economy is creating a deep integration in East Asia
- Transferring diffractive optics from research to commercial applications: Part I – progress in the patent landscape
- Community
- News from the European Optical Society
- Conference Notes
- Conference Calendar
- Topical Issue: Remote Sensing
- Editorial
- Remote sensing
- Tutorial
- Speckle effects in target-in-the-loop laser beam projection systems
- Review Articles
- Laser gated viewing at ISL for vision through smoke, active polarimetry, and 3D imaging in NIR and SWIR wavelength bands
- Infrared detectors for space applications
- Research Article
- Alternative design for extremely large telescopes and options to use the VATT for ELT design demonstration
- Letters
- Holographic wavefront sensor for fast defocus measurement
- Beam combining of quantum cascade lasers for remote sensing
- Review Article
- Design of freeform optics
- Research Article
- NIR cutoff filter for true color imaging sensors
