Double active parallax barrier for viewing stereoscopic imges

Double active parallax barrier for viewing stereoscopic images in which both barriers form a single device which is placed in front of each observer and at sufficient distance from the latter so as not to prove uncomfortable, through which each observer, with no need to use special glasses or wear any other device in front of his eyes and being able to move his head freely, will see with his left eye the image that corresponds to this eye and with his right eye the image that correspond to his right eye, the images being generated using any stereoscopic image display system (4) in which each image displayed is polarised linearly and in a perpendicular polarisation direction to that of the other image (I1, I2), characterised by three components (1, 2, 3), the first (1) being a parallax barrier comprising a linear polariser (101) and two transparent electrodes (102, 104) between which is placed liquid crystal material (103) which rotates by 90° the polarisation plane in all the vertical stripes that form the odd bars (1031, 1033, . . . ) of the parallax barrier and maintains the polarisation plane of the vertical stripes that form the even bars (1032, 1034, . . . ) and in which the rotation effect plus the polarisation effect is that of a polarisation barrier PBP in which the even bars (12, 14, . . . ) polarise the light linearly in a perpendicular direction to that of the polarisation direction of the odd bars (11, 13, . . . ), the second component (2) being a parallax barrier comprising liquid crystal material (203) placed between two transparent electrodes (202, 204), such that the odd vertical bars (2031, 2033, . . . ) rotate the polarisation plane by 90° and the even bars (2032, 2034), maintain the polarisation direction with no rotation, the third component (3) being electronic means able to produce the aforementioned polarisation and rotation bars and to electronically move the parallax barriers relative to each other from left to right and to change the width of the bars according to the signal received by a device that detects the position of the observer's head.