Driving method for liquid crystal grating, and display apparatus and display method for display apparatus

A driving method for a liquid crystal grating, comprising:

• determining a real-time position of a center of a pupil;
• determining a position of a light-transmitting region, that corresponds to the real-time position, in the liquid crystal grating according to the real-time position, and a pre-established correspondence between positions of the center of the pupil and positions of a light-transmitting region in the liquid crystal grating;
• and
• driving the liquid crystal grating to cause that the liquid crystal grating only transmits light at the position of the light-transmitting region that corresponds to the real-time position;
• wherein the determining a real-time position of a center of a pupil comprises:
• capturing a face image of a user in real time, and determining three dimensional coordinates of the center of the pupil under a camera coordinate system based on the face image;
• wherein the capturing a face image of a user in real time, and determining three dimensional coordinates of the center of the pupil under a camera coordinate system based on the face image comprises:
• obtaining the face image of the user in real time by using an infrared camera;
• extracting a plurality of first edge points of an iris in the face image, performing ellipse fitting on the plurality of first edge points, and using two dimensional coordinates of an ellipse center obtained by fitting under an image coordinate system as two dimensional coordinates of the center of the pupil under the image coordinate system;
• obtaining a plurality of face feature points in the face image, and mapping the plurality of face feature points to the same positions on a pre-established three dimensional face model;
• adjusting a coordinate system of the three dimensional face model to coincide with the camera coordinate system;
• using a mean value or a mode number of depth coordinates of a plurality of second edge points of human eyes in the three dimensional face model under the camera coordinate system as depth coordinates of the center of the pupil under the camera coordinate system;
• and
• transforming the two dimensional coordinates of the center of the pupil under the image coordinate system to be two dimensional coordinates of the center of the pupil in the same dimension under the camera coordinate system, the two dimensional coordinates of the center of the pupil under the camera coordinate system and the depth coordinates of the center of the pupil under the camera coordinate system constituting the three dimensional coordinates of the center of the pupil under the camera coordinate system.