Modular snapshot multispectral-panchromatic imager (MSPI) with customized filter arrays

Abstract

As one of the simplest methods to construct snapshot spectral imagers, multispectral filter array (MSFA) has been applied to commercial miniatured spectral imagers. While most of them have fixed configurations of spectral channels, lacking flexibility and replaceability. Moreover, conventional MSFA only comprises filtering channels but lacks the panchromatic channel which is essential in detecting dim and indistinct objects. Here, we propose a modular assembly method for snapshot imager which can simultaneously acquire the object’s multispectral and panchromatic information based on a customized filter array. The multispectral-panchromatic filter array is batch fabricated and integrated with the imaging senor through a modular mode. Five-band spectral images and a broadband intensity image can be efficiently acquired in a single snapshot photographing. The efficacy and accuracy of the imager are experimentally verified in imaging and spectral measurements. Owing to the modular architecture, our proposed assembly method owns the advantages of compactness, simple assembling, rapid replacement, and customized designing, which overcomes the expensiveness and complexity of scientific-level snapshot spectral imaging systems.

Ultrabroadband, High Color Purity Multispectral Color Filter Arrays

“…This is traditionally done by directly changing the physical thickness of the cavity, which may require multiple lithography steps 4,8−11 or special lithography technologies. [6][7][8]13 Therefore, it is challenging to fabricate more than 20 channels due to the increasing number of fabrication steps and the difficulty in integration of a staircase surface. To overcome these challenges, subwavelength structures have been introduced into the cavity layer, allowing peak wavelength tuning by changing the fill ratio, which leads to an effective index change of the cavity layer.…”

“…To achieve the level of integration and compactness of modern digital cameras, it is essential to have high-performance and miniature MSFAs that can be directly integrated or fabricated onto Complementary Metal Oxide Semiconductor (CMOS) sensors, the pixel sizes of which are on the order of a few micrometers. Recent advancements in nanofabrication technologies have demonstrated the feasibility of miniature MSFAs with individual filter sizes under 10 μm, utilizing thin-film stacks − or metallic and dielectric metasurfaces. − However, most designs involve trade-offs between different essential aspects of multispectral imaging, including high transmission, narrow line width (high spectral resolution), color purity (low sidebands), a large working wavelength range, angular and polarization insensitivity, and compatibility with current CMOS fabrication processes. Combining all of these features into MSFAs with dimensions in the tens of micrometers poses a significant challenge.…”

“…They consist of a low-index cavity layer sandwiched between two distributed Bragg mirrors or metallic mirrors to filter incident light based on interference-induced cavity resonances. ,− ,− In MSFA based on Fabry–Pérot structures, the peak wavelength of each color filter can be tuned by changing the optical length of the corresponding cavity layer. This is traditionally done by directly changing the physical thickness of the cavity, which may require multiple lithography steps ,− or special lithography technologies. − , Therefore, it is challenging to fabricate more than 20 channels due to the increasing number of fabrication steps and the difficulty in integration of a staircase surface. To overcome these challenges, subwavelength structures have been introduced into the cavity layer, allowing peak wavelength tuning by changing the fill ratio, which leads to an effective index change of the cavity layer. − However, due to a limited free spectral range (FSR), Fabry-Pérot-based MSFAs are restricted to a narrow working wavelength range to maintain high color purity.…”

Mosaic-pixelated Fabry-Pérot filters for snapshot spectral imagers

“…While multispectral and hyperspectral sensors are available commercially, they remain relatively expensive because they have yet to be widely adopted [4]. Efforts are underway to develop methods to bring down costs, including using batch fabrication [8,9]. The field has other open avenues for improvement, including developing customized etalon arrangements for smaller-scale prototyping with specific desired responses depending on the envisioned applications.…”