You can’t, because in fact your brain really creates images.
Healthy person most commonly sees images based on the light their eyes receive, but based on the quality of information you may interpret it wrongly. Especially light captured by side sight – here brain draws a big part of picture itself.
People with schozophrenia can see and hear non-existing people like we see real people. It can take them a lot of reasoning to verify if person they are seeing in fact real.