Apparatus and method for detecting surface shear force on a display device

A method for sensing a shear force at a surface of a display device comprising an optical sensing array to detect light, a backlight to emit light toward a surface of the display device, and a thin optical film layer at the surface of the display device, the method comprising:

• detecting a first point of contact at the surface of the display device;
• reflecting by the thin optical film layer, while a first shear force is being applied at the first point of contact at the surface of the display device, light having a first wavelength at a front area ahead of the first point of contact in a direction of the first shear force;
• reflecting by the thin optical film layer, while the first shear force is being applied, light having a second wavelength at a back area behind the first point of contact opposite the front area, the second wavelength being different from the first wavelength;
• and
• sensing by the optical sensing array the reflected light having the first and second wavelengths.

A display device comprising:

• a backlight to emit light;
• a lower linear polarizer on the backlight;
• an upper linear polarizer on the lower linear polarizer;
• a liquid crystal display between the lower and upper linear polarizers;
• and
• an optical sensing array to detect light reflection asymmetry at the liquid crystal display while a shear force is being applied at a surface of the display device.