Can't use blur

Hi, I am using BlurOptimized as a component on my MainCamera and I want to turn it on at a certain point, but when I do GetComponent () it says "Assets/Scripts/CameraController.cs(21,30): error CS0246: The type or namespace name `BlurOptimized' could not be found. Are you missing a using directive or an assembly reference?". I don't know what to do.