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An apparatus invented by Porta for obtaining pictures of objects. It consists essentially of a box with a small opening closed by a convex lens. The rays from the object, striking upon the lens, are brought to a focus on a plate of ground glass, either directly or after reflection from a mirror. Here the image can either be traced by hand, or, if a sensitive plate is introduced, photographed.

n. [Latin] An apparatus in which the images of external objects, received through a double convex glass, are thrown upon a white surface placed on the focus of the glass within a darkened chamber.

An optical machine used in a darkened chamber, so that the light coming only through a double convex glass, objects opposite are represented inverted.