What optical device did Leonardo da Vinci use in experiments with projected images?

Leonardo da Vinci used the camera obscura as an optical device for studying projected images.

A camera obscura is a darkened chamber or box with a small opening. Light from a scene passes through the opening and forms an inverted image on the opposite surface. Leonardo described and investigated this effect in his notebooks, comparing it with the way the eye receives images.

The device is not a camera in the modern photographic sense. It records no image permanently unless an artist traces the projection or another recording method is added. It also does not require a lens, although later camera obscura designs commonly used lenses to brighten and sharpen the image.

Leonardo’s observations linked practical optics with the study of vision and perspective. He recognized that the image formed inside the device follows principles similar to those involved in human sight, making the camera obscura important to both Renaissance art and the history of optical science.