real image

A real image is one of two classifications of images produced by optics, the other termed a virtual image. A real image is one formed at a particular location such that if you placed a screen at its location (such as a movie screen or a similar screen of the size of the image), a visible image would appear on the screen. The projector at a movie theater is focused to produce a real image at the screen. A camera focuses a real image at the CCD sensor or photographic film within a camera: the sensor (CCD or photographic film) reacts to the illumination, capturing the image. An eye is analogous, focusing a real image on the retina. Locations within the optics where real images form are termed focal planes.

A virtual image, in contrast, is an image that can be viewed from some locations, but the image itself does not have a location in the manner of a real image. If you look through a telescope's eyepiece at something distant, the telescope offers you a virtual image of that object that is closer than the object actually is. Placing a screen at the location of this virtual image does not put the image on the screen. The image merely looks to you to be at that position when you look through the eyepiece. Typical microscopes, binoculars, etc., produce such virtual images.