Method and device for fall prevention and detection, specially for the elderly care based on digital image analysis using an intelligent optical sensor. The fall detection is divided into two main steps; finding the person on the floor, and examining the way in which the person ended up on the floor. The first step is further divided into algorithms investigating the percentage share of the body on the floor, the inclination of the body and the apparent length of the person. The second step includes algorithms examining the velocity and acceleration of the person. When the first step indicates that the person is on the floor, data for a time period of a few seconds before and after the indication is analysed in the second step. If this indicates fall, a countdown state is initiated in order to reduce the risk of false alarms, before sending an alarm. The fall prevention is also divided into two main steps; identifying a person entering a bed, and identifying the person leaving the bed to end up standing beside it. The second step is again further divided into algorithms investigating the surface area of on or more objects in an image, the inclination and the apparent length of these objects. When the second step indicates that a person is in an upright condition, a countdown state is initiated in order to allow for the person to return to the bed.