In reference to terminology originating with cathode-ray tubes (CRTs), the refresh rate, also known as vertical refresh rate, vertical scan rate or vertical frequency, is the number of times per second that a raster-based display device displays a new image. This can be independent from frame rate, which describes how many images are stored or generated every second by the device driving the display. On CRT displays, higher refresh rates produce less flickering, thereby reducing eye strain. In other technologies, such as liquid-crystal displays, the refresh rate affects only how often the image can potentially be updated.