Display device and display device control method

1. A display device, comprising:

a display module, comprising a light source that emits an input light; and

a privacy module, disposed on the display module and for receiving the input light, the privacy module comprising a first polarizing element for absorbing light in a predetermined direction,

wherein the input light passes through the first polarizing element to output an output light from an output surface of the first polarizing element,

wherein the output surface comprises a first edge, a second edge, a third edge, and a fourth edge, the second edge is connected to the first edge, the third edge is connected to the second edge, the fourth edge is connected to the first edge and the third edge, the third edge is opposite to the first edge, the fourth edge is opposite to the second edge,

where the first edge and the third edge are parallel to a first direction, wherein the first direction is perpendicular to an optical axis of the display device, the second edge and the fourth edge are parallel to a second direction, the second direction is perpendicular to the optical axis of the display device and is perpendicular to the first direction, and

wherein the output light from the first edge has a first polarized direction that is parallel to the first direction, the output light from the second edge has a second polarized direction that is parallel to the second direction, the output light from the third edge has a third polarized direction that is parallel to the first direction, and the output light from the fourth edge has a fourth polarized direction that is parallel to the second direction.

2. The display device as claimed in claim 1 , wherein the predetermined direction is not parallel to the optical axis of the display device.

3. The display device as claimed in claim 2 , wherein the first polarizing element comprises a light absorbing dye.

4. The display device as claimed in claim 3 , wherein the light absorbing dye comprises a dichroic dye.

5. The display device as claimed in claim 3 , wherein the light absorbing dye includes a longitudinal axis that is parallel to the optical axis.

6. The display device as claimed in claim 3 , wherein the first polarizing element further comprises a liquid crystal for aligning the light absorbing dye.

7. The display device as claimed in claim 2 , wherein the input light comprises a vertical input light parallel to the optical axis, and an inclined input light not parallel to the optical axis, and

wherein the vertical input light is not polarized by the first polarizing element, and the inclined input light is polarized by the first polarizing element.

8. The display device as claimed in claim 2 , wherein the privacy module further comprises a second polarizing element with an absorption axis perpendicular to the optical axis.

9. The display device as claimed in claim 8 , wherein the privacy module further comprises a light modulator disposed between the first polarizing element and the second polarizing element, wherein a polarization direction of a light is changed after passing through the light modulator by changing a voltage applied to the light modulator.

10. The display device as claimed in claim 9 , wherein the first polarizing element is disposed between the light source and the light modulator.

11. The display device as claimed in claim 1 , wherein the privacy module further comprises:

a second polarizing element, having an absorption axis that is parallel to the first direction,

a light modulator, disposed between the first polarizing element and the second polarizing element,

wherein when the light modulator is disabled, a light output from a first observation position that is corresponding to the first edge of the first polarizing element is invisible, and a light output from a second observation position that is corresponding to the second edge of the first polarizing element is visible.

12. The display device as claimed in claim 11 , wherein when the light modulator is enabled, the light output from the first observation position is visible, and the light output from the second observation position is invisible.