Visibility improvement for a blind spot monitor by compressing the brightness range of images

An outdoor scene, which is the subject of a blind spot monitor, for instance a rear view monitor, occasionally has a very wide brightness range. However, the dynamic range of a liquid crystal display, which is commonly used as an in-vehicle display, is considerably narrower than the dynamic range of the outdoor scene and the camera to capture the image. Therefore, the darker regions in the image would be under the noise level of the display, otherwise the brighter regions in the image would saturate. To solve the problem, we propose a method to compress the overall brightness range of the image keeping the contrast of objects using image processing. This method suppresses the lower spatial frequency component of the captured image according to the brightness of each pixel. As a result, the image of the outdoor scene can be displayed on an in-vehicle display with high visibility, without artifact, even if the scene has very wide dynamic range.