Abstract: A method for monitoring respiration by illuminating the body of the subject with a luminous flux, where a lens is used to form on a set of photosensitive elements, an image of at least one region of the space within which a person under surveillance is capable of moving, a light source is used for illuminating the area, fine control and readout circuits are connected to the photosensitive elements, an analog to digital converter is to the control circuit, and a microprocessor is used to compare successive signals from the photosensitive elements and which is used to determine any significant variations in the successive signals which are due to respiration of the person being monitored. An alarm is also included which is triggered in response to an absence of variations on successive signals.

Abstract: The invention relates to a method and to a device for determining the number of people to be found in a determined space, by means of a strip (14) of photodetectors (16) on which an objective lens (10) forms a linear image of a space including objects or people (12). The signals successively produced by the photodetectors (16) are compared by a microprocessor (22) in order to show up movement of people and to deduce the number of people present therefrom.The invention is applicable to performing surveillance of premises and to performing automatic television audience surveys.