Proximity detector and method of sectorially detecting a target used as ignition device for an explosive charge

The device (8) uses an optical system with axial symmetry about the axis XX'. It is intended, in combination with suitably placed sensors, to detect the presence of a target in a given solid angle. In a diagram showing a longitudinal cross-section of the device in a plane P containing the axis XX', a window consisting of a front point A and a rear point B allows the passage of radiations coming along an axis DELTA intersecting the axis XX' at a point O and making an angle theta less than 90 DEG with it. The aperture angle 2 tau of the window is represented by the angle between two straight lines O'A and O''B each making an angle tau with the axis DELTA . The device comprises two mirrors M1, M2 and a converging lens (12). The mirror M1 is represented in the plane P by a cross-section in the shape of an arc of a parabola PM1 with its focus at a point F situated in front of the point O and with an axis of symmetry DELTA 1 parallel to DELTA and passing through F. The mirror M2 is represented in the plane P by a cross-section in the shape of an arc of a parabola PM2 having an axis of symmetry delta making a small angle alpha with XX' and having a focus at the point F. The lens (12) has its optical centre on the axis XX' substantially at the point where the parabola PM1 intersects the axis XX'.