As technology continues to advance in the surveillance industry, manufacturers have found a new way to improve nighttime security offerings. Night vision feeds have traditionally used green- and gray scale images to help monitors and authorities make out what is happening in the video footage. Recently, equipment has been constructed that can utilize color mapping and color space conversion to apply natural colors to nighttime imagery. By understanding how this mechanism works and the benefits it provides, home and business owners can decide whether this technology is a must for their security needs.
Color mapping uses a combination of multiband images and subsequent natural color reference images to create a match that generates a nighttime image with colors that correspond to what would be seen in a daytime image. By applying natural colors to a multiband night-time image, color mapping allows the dark pictures to be presented as they would be if they had been taken in natural daylight.
How it works
According to Maarten Hogervorst and Alexander Toet's article, "Method for applying daytime colors to nighttime imagery in realtime," there are two main steps in this process. First, two or three bands of a multiband nighttime image are transferred onto the RGB (red, green, blue) channels of a false color image. The resulting picture is a false color RGB night-vision image. Next, the image is transformed into a color space that is perceptually de-correlated. During this process in the color space, the first order statistics of the target scene (natural color image) are transferred back onto the source scene (multiband nighttime image). This converse transformation back to the original RGB space allows the nighttime image to take on a daytime color appearance.
The similarity between the nighttime image and its enhanced natural daylight counterpart is dependent on the strength of the correlation between the daylight colors and sensor values. If a high correlation occurs, the result is a better variation of the natural colors that will be predicted. When the correlation is low, the image may not have the same recognizable daylight colors, as the multiband sensor is sensitive to certain wavelengths that are more suitable for producing natural coloring.
According to Apple Computers, color mapping embodies the process of using highlight colors with transparency values to the colors used in an overlay, which can be simple or advanced. Simple overlays use one overlay color to generate the image while advanced varieties use up to four overlay colors to generate a more detailed image.
One of the greatest benefits of color mapping technology for surveillance is that it may improve the contrast between images in the scene, which allows for enhanced object detection and scene recognition. Unlike in monochrome night vision technologies, color can now be used to discriminate between different objects, people and landscape features in the image.
As relevant color schemes are customizable to the application and environment being monitored, it is easy to deploy the technology in real time and aid human observers in interpreting the imagery more effectively. When the nighttime imagery is displayed in natural looking colors that human observers are familiar with, they will be better able to interpret the imagery because there are no additional layers to work through. When there is nothing surprising about the footage, it is easier to pick up on the details and clues that are relevant to the investigation.
This reduces the long reaction times typically associated with monitoring nighttime surveillance and can also improve situational awareness for enhanced perception capabilities. Hogervorst and Toet explain that this occurs because artificial colors do not correspond in the same intuitive way that natural illumination can. When the colors are unnatural and unfamiliar, the individual's recognition process may become disrupted.
Unlike other nighttime imagery options, color mapping also removes the expenses and color constancy issues that are common in other surveillance conversion methods. Applying natural daylight colors to multiband nightvision imagery allows the scene to remain stable and consistent when variations occur. Color mapping is both easy and fast, and can be useful across surveillance, security and reconnaissance applications.