Mobile terminal including frames and optical tracking sensor

1. A mobile terminal comprising:

a first frame;

a second frame configured to be movable along a first direction or a second direction with respect to the first frame, the second direction being opposite the first direction;

an optical tracking sensor (OTS) mounted to the first frame to face a first surface of the second frame, the OTS being configured to acquire optical pattern information corresponding to an opposing surface;

a driver configured to provide a driving force to move the second frame along the first direction; and

a controller configured to calculate a movement distance of the second frame based on the optical pattern information acquired by the OTS and to control the driver based on the calculated movement distance,

wherein a marker is located at the first surface of the second frame at a position facing the OTS,

wherein the second frame is further configured to move along the first direction to change from a first state, in which the second frame has a maximum overlapping area with the first frame, to a second state, in which the second frame has a minimum overlapping area with the first frame, and

wherein the controller is further configured to adjust a speed of the driver.

2. The mobile terminal of claim 1 , wherein the OTS is further configured to acquire a plurality of pieces of optical pattern information corresponding to the opposing surface at predetermined time intervals, the plurality of pieces of optical pattern information varying as the second frame moves, and

wherein the controller is further configured to calculate the movement distance of the second frame based on changes in the plurality of pieces of optical pattern information.

3. The mobile terminal of claim 1 , wherein the marker comprises at least one of a first marker overlapping the OTS when the second frame is in the first state, or a second marker overlapping the OTS when the second frame is in the second state, and

wherein the controller is further configured to stop operation of the driver based on the OTS sensing the first marker or the second marker.

4. The mobile terminal of claim 3 , wherein the controller is further configured to initialize the movement distance of the second frame based on the OTS sensing the first marker or the second marker.

5. The mobile terminal of claim 3 , wherein the marker further comprises a third marker located between the first marker and the second marker, and

wherein the controller is further configured to increase or decrease the speed of the driver based on the OTS sensing the third marker.

6. The mobile terminal of claim 1 , wherein the driver comprises a first driver and a second driver spaced apart from the first driver with respect to a third direction perpendicular to the first direction, and

wherein the controller is further configured to perform control such that the first driver and the second driver have a same speed.

7. The mobile terminal of claim 6 , wherein the first surface of the second frame comprises a first portion having an opposing surface capable of being sensed by the OTS when the second frame moves, and a second portion adjacent to the first portion with respect to the third direction,

wherein the marker comprises a fourth marker located at the second portion, and

wherein the controller is further configured to, based on the OTS sensing the fourth marker, adjust a speed of one of the first driver or the second driver so that the fourth marker is not sensed at a later time.

8. The mobile terminal of claim 1 , wherein the marker is darker in color than the first surface of the second frame.

9. The mobile terminal of claim 1 , wherein the marker has a recess at the first surface of the second frame.

10. The mobile terminal of claim 1 , wherein the OTS comprises:

a beam transmitter configured to emit a beam towards the first surface of the second frame; and

a beam receiver configured to sense a beam reflected from the first surface of the second frame and to acquire the optical pattern information.

11. The mobile terminal of claim 1 , further comprising:

a flexible display comprising a fixed portion coupled to a front surface of the first frame, and a variable portion extending along the first direction and rollable toward a rear surface of the second frame,

wherein the variable portion of the flexible display comprises a region located at a front surface of the second frame, the region varying in area depending on a relative position of the first frame and the second frame, and

wherein the controller is further configured to output an image at the flexible display according to the calculated movement distance of the second frame.