A single sensor based multispectral imaging camera using a narrow spectral band color mosaic integrated on the monochrome CMOS image sensor

Xin He,Dan Smith,Efstratios Skafidas,Fatima Eftekhari,Ampalavanapillai Nirmalathas,Md Hemayet Uddin,Arman Ahnood,Yajing Liu,Kumar Ganesan,Ranjith Rajasekharan Unnithan,Paul Beckett

doi:10.1063/1.5140215

Abstract

A multispectral image camera captures image data within specific wavelength ranges in narrow wavelength bands across the electromagnetic spectrum. Images from a multispectral camera can extract a additional information that the human eye or a normal camera fails to capture and thus may have important applications in precision agriculture, forestry, medicine, and object identification. Conventional multispectral cameras are made up of multiple image sensors each fitted with a narrow passband wavelength filter and optics, which makes them heavy, bulky, power hungry, and very expensive. The multiple optics also create an image co-registration problem. Here, we demonstrate a single sensor based three band multispectral camera using a narrow spectral band red–green–blue color mosaic in a Bayer pattern integrated on a monochrome CMOS sensor. The narrow band color mosaic is made of a hybrid combination of plasmonic color filters and a heterostructured dielectric multilayer. The demonstrated camera technology has reduced cost, weight, size, and power by almost n times (where n is the number of bands) compared to a conventional multispectral camera.

Highlights

In a conventional CMOS based image sensor, color imaging relies on the integration of filters on top of the photodetector array.1–5 These filters typically cover the three primary colors, red–green–blue (RGB), predominately in a Bayer pattern.6–9 As the human eye is more sensitive to green light than either red or blue, the widely used Bayer filter mosaic is formed from alternating rows of red–green and green–blue filters with twice as many green as red or blue filters
We demonstrate a single sensor based three band multispectral camera using a narrow spectral band red–green–blue color mosaic in a Bayer pattern integrated on a monochrome CMOS sensor
We demonstrate a single sensor-based multispectral camera using a hybrid narrow spectral band RGB color mosaic fabricated on a quartz substrate and integrated on a monochrome CMOS image sensor

Summary

Introduction

In a conventional CMOS based image sensor, color imaging relies on the integration of filters on top of the photodetector array. These filters typically cover the three primary colors (bands), red–green–blue (RGB), predominately in a Bayer pattern. As the human eye is more sensitive to green light than either red or blue, the widely used Bayer filter mosaic is formed from alternating rows of red–green and green–blue filters with twice as many green as red or blue filters. In a conventional CMOS based image sensor, color imaging relies on the integration of filters on top of the photodetector array.. In a conventional CMOS based image sensor, color imaging relies on the integration of filters on top of the photodetector array.1–5 These filters typically cover the three primary colors (bands), red–green–blue (RGB), predominately in a Bayer pattern.. Three different materials are used for producing the primary colors with wide spectral bands (spectral width of around 90–100 nm) for all wavelengths.6,9 Multispectral cameras extend this concept to capture images with multiple color bands and with narrow passbands (i.e., narrow spectral widths).. Conventional multispectral cameras are made up of multiple CMOS sensors each externally fitted with a narrow passband wavelength filter. The spectral width measured at the FWHM (Full Width at Half Maximum) of a multispectral imaging camera varies between 10 nm and 90 nm. Figure 1S and Table 1S (see the supplementary material) show a comparison between a conventional multispectral camera with six bands and a single sensor based multispectral camera

Methods

Results

Conclusion