There is always the possibility to overlooking monochrome cameras while seeking an imaging solution due to the availability of various new cameras with improved low light performance, vivid color, and sharp contrast. However, monochrome cameras have high light sensitivity, generate sharper images with superior resolution, and output smaller file sizes, making them suitable for a number of applications.
Advantages of Monochrome Cameras
Unlike a color image sensor, a monochrome image sensor does not use a color filter array (CFA), which is an optical band pass filter. The lack of CFA allows for more number of photons to reach the sensor’s photosensitive surface, thus rendering it more sensitivity to light or higher quantum efficiency. Moreover, IR cut filters are usually present in color cameras to avoid infrared light from producing color aberrations. The absence of these filters would allow the red, green, and blue pixels to react with different near infrared (NIR) wavelengths, thus producing inaccurate and strange colors.
Conversely, the lack of the CFA and IR cut filter enables every pixel of a monochrome sensor to detect a broader light spectrum, thereby significantly improving the overall performance of the camera in low lighting conditions. Hence, additional enhancements can be observed at higher wavelengths, especially above 650nm, where the NIR region begins. Cameras featuring CFAs have to interpolate the color data that is filtered out by the optical filters using complex demosaicing algorithms. These calculations introduce a margin of error, as the data is interpolated and not quantified.
The added error can be eliminated upon removal of the CFA. This, in turn, helps generate sharper images with a higher effective resolution due to the presence of a measured value in every pixel of a monochrome sensor that is not affected by its neighbors (Figure 1A and 1B). The reduced size of the monochrome image files can also attributed to the absence of the CFA. There is a threefold reduction in the image size owing to the absence of specific color channel information in the monochrome image data. The bit depth would also be increased because of this size reduction without compromising storage savings, camera permitting.
Figure 1. A. Enlargement of a raw RGB image capturing a color chart. The color channels are displayed as seen by the image sensor, with Bayer pattern – without demosaicing. B. Enlargement of a raw monochrome image capturing the same color chart. Gray-levels are consistent for each area and no Bayer pattern is present – demosaicing not required.
Lumenera’s Monochrome Cameras
Lumenera offers a range of scientific and industrial grade monochrome cameras (Figure 2) for applications demanding high spatial resolution and sensitivity. In life sciences, they are employed for observing very faint fluorescence signals in wavelengths longer than 650nm that are released by dyes used for staining the samples under microscopes (Figure 3). In unmanned aerial vehicles, they are used for determining the amount of IR light reflected off the vegetation to identify the hydration needs and health of the plants (Figure 4). Intelligent traffic systems use automated tolling cameras for capturing vehicle license plates, particularly in the overnight hours (Figure 5).
Figure 2. Lumenera has wide variety of camera models that are available in monochrome variants.
Figure 3. Mouse intestine sample image taken with Lumenera’s INFINITY3-1M monochrome microscopy camera.
Figure 4. Aerial view of a vineyard surveyed to monitor vegetation health, captured with Lumenera’s Lt965RM monochrome camera.
Figure 5. Example of monochrome automated tolling cameras capturing vehicle license plates.
Apart from the above three examples, high light sensitivity and detection ability are required in many other applications for highly sophisticated technical processes. Lumenera keeps on striving to provide imaging solutions and technical support for various specialized environments, where high sensitivity and resolution are of utmost importance.
This information has been sourced, reviewed and adapted from materials provided by Lumenera Corporation.
For more information on this source, please visit Lumenera Corporation.