MULTISPECTRAL IMAGING TECHNOLOGY


Cameras have traditionally come in two flavors: monochrome and color.  Now, Spectral Devices Inc. offers a lineup of standard and custom multispectral cameras that provide new imaging capabilities without adding size or weight. Spectral Devices Inc. has developed multispectral optical imaging sensors that enable the detection of up to 4 distinct colors simultaneously. (Spectral Devices Inc. can offer cameras with up to 16 colors or bands. Please contact us.) This is in contrast to the non-selective color sensitivity of monochrome sensors and the fixed 3-color detection capabilities of color imaging sensors available in most cameras on the market today. Color cameras support the detection of red, green, and blue using a color filter array (CFA) with broad, overlapping transmission characteristics. The CFA is manufactured with an RGGB pattern of dyes or pigments (Figure 1) that are not easily tuned and suffer from overlapping transmission spectra in the near-infrared. In contrast, Spectral Devices Inc. sensors utilize a multispectral filter array (MFA) that incorporates proprietary pixelated bandpass filters whose transmission characteristics can be precisely tuned during manufacturing. The MFA works by breaking down the image sensor into cells, where each cell contains between 2 and 16 microscale optical bandpass filters (e.g. B1, B2, B3, and B4; Figure 1) to separate colors in the image by wavelength. The cells are distributed in a 2-dimensional array to form the MFA, which is aligned and integrated onto the image sensor.

Figure 1. Monochrome, color, and multispectral sensor configurations


Figure 1. sensor configurations

Figure 1. sensor configurations

Figure 1. sensor configurations

The vast majority of multispectral imaging applications utilize unique combinations of optical filter bands. Generally, no two applications use the same combination of bands and applications differ in their spectral bandwidth requirements. Therefore, the use of a generic MFA that has many bands that are distributed evenly across the optical spectrum are poorly suited to most multispectral imaging applications. Many-band generic MFAs result in reduced image resolution due to the loss in usable sensor area that is devoted to bands that are unused. Furthermore, spectral features of targets may be very broad (e.g in near-infrared) so that detection with one or two bands is all that is needed. In these cases, most of the bands on 16-band or 25-band generic MFAs would provide highly-correlated, redundant measurements that result in degraded spatial resolution. For many multispectral imaging applications between two to four spectral bands are often all that is required. Spectral Devices Inc. has invested heavily in developing unique MFAs that satisfy the broadest range of bands and bandwidths with emphasis on 4-band MFAs that provide high performance multispectral imaging optimized for specific applications.

Spectral Devices Inc. has developed MFAs with a wide range of spectral transmission characteristics (Table 1; Figure 2). For example, filters can have pass bands in the visible and/or near-infrared range, and pass bands can be narrow (~5 nm), medium (~30 nm), or wide (~70 nm). Spectral Devices Inc. has developed proprietary and patent-pending manufacturing methods that substantially reduce the cost of standard multispectral cameras and allow customers to choose unique sets of bands to match their unique multispectral imaging application. Spectral Devices offers multispectral cameras with color and monochrome (panchromatic) sensitivity, color and near-infrared sensitivity, and bands tuned to enable precision agriculture and biomedical research applications. For customers requiring a custom multispectral camera with bands tuned to match a specific application requirement, Spectral Devices Inc. manufactures customized multispectral camera solutions at highly competitive prices.

Table 1. Table of custom multispectral filter array (MFA) types offered by Spectral Devices Inc

Table of MFA filter types


Figure 2. Spectral Devices Inc monochrome, color and multispectral camera quantum efficiency and filter transmission properties

Monochrome sensor color sensor color sensor color sensor color sensor
Monochrome
Color
RGB-Mono
RGB-NIR
Agriculture
color sensor color sensor color sensor color sensor color sensor
Biomedical
Custom (F1)
Custom (F3)
Custom (F4)
Custom (F5)
color sensor color sensor color sensor color sensor color sensor
Custom (Visible Narrow)
Custom (Wide Band)
Custom (UV)
Custom (Long Pass)
Custom (F6)