A display device (100, 200, 400, 500, 600) comprising: an optical sensing array to detect light; a backlight to emit light toward a surface of the display device (100, 200, 400, 500, 600); and an optical thin film layer at the surface of the display device (100, 200, 400, 500, 600), the optical thin film layer being configured to, while a first shear force (308, 328, 348, 368, 404) is being applied at a first point of contact (302, 322, 342, 362, 402) at the surface of the display device (100, 200, 400, 500, 600), reflect light having a first wavelength at a front area (306, 326, 346, 366) ahead of the first point of contact (302, 322, 342, 362, 402) in a direction of the first shear force (308, 328, 348, 368, 404), and reflect light having a second wavelength at a back area (304, 324, 344, 364) behind the first point of contact (302, 322, 342, 362, 402) opposite the front area (306, 326, 346, 366), the first wavelength being different from the second wavelength characterized in that the optical sensing array comprises a plurality of detectors with a same wavelength tuning, wherein the optical sensing array provides a tuned wavelength that is shifted from a nominal wavelength, wherein when the first shear force (308, 328, 348, 368, 404) results in a shift of the nominal wavelength towards longer wavelength in reflected light at the front area (306, 326, 346, 366), the optical sensing array detects an increase in reflected light intensity, and wherein when the first shear force (308, 328, 348, 368, 404) results in a shift of the nominal wavelength towards shorter wavelength in reflected light at the back area (304, 324, 344, 364), the optical sensing array detects a decrease in reflected light intensity. an optical sensing array to detect light; a backlight to emit light toward a surface of the display device (100, 200, 400, 500, 600); and an optical thin film layer at the surface of the display device (100, 200, 400, 500, 600), the optical thin film layer being configured to, while a first shear force (308, 328, 348, 368, 404) is being applied at a first point of contact (302, 322, 342, 362, 402) at the surface of the display device (100, 200, 400, 500, 600), reflect light having a first wavelength at a front area (306, 326, 346, 366) ahead of the first point of contact (302, 322, 342, 362, 402) in a direction of the first shear force (308, 328, 348, 368, 404), and reflect light having a second wavelength at a back area (304, 324, 344, 364) behind the first point of contact (302, 322, 342, 362, 402) opposite the front area (306, 326, 346, 366), the first wavelength being different from the second wavelength characterized in that the optical sensing array comprises a plurality of detectors with a same wavelength tuning, wherein the optical sensing array provides a tuned wavelength that is shifted from a nominal wavelength, wherein when the first shear force (308, 328, 348, 368, 404) results in a shift of the nominal wavelength towards longer wavelength in reflected light at the front area (306, 326, 346, 366), the optical sensing array detects an increase in reflected light intensity, and wherein when the first shear force (308, 328, 348, 368, 404) results in a shift of the nominal wavelength towards shorter wavelength in reflected light at the back area (304, 324, 344, 364), the optical sensing array detects a decrease in reflected light intensity.