Photo-sensing enabled display for touch detection with customized photodiode and light emitting diode component level angular response
An electronic device may have a touch sensitive display with optical touch sensors that are insensitive to the presence of moisture. The optical touch sensors may include light sources and light detectors. Light illuminator and detector angular filters (e.g., masks, baffles) can be employed to limit the illumination and receive angles of emitted and detected light to minimize false object detection. In some examples, light illuminator and detector masks and baffles can be formed during the photodiode component fabrication process. Interference filters may be included over the light sources and/or the light detectors to improve discrimination between a user's finger and water, and may have a greater transmission for light at a first incident angle that is greater than the critical angle of the water/cover interface than at a second incident angle that is less than the critical angle.
1 . An electronic device configured to gather touch input, comprising:
a display having a display cover layer with a surface, wherein the surface has a surface normal; and
an optical touch sensor comprising:
a light source that emits light toward the display cover layer;
a light detector that detects reflections of the light; and
interference filters formed over the light detector, the interference filters comprising:
a first interference filter having a first transmission for light at a first incident angle relative to the surface normal, and
a second interference filter having a second transmission for light at a second incident angle relative to the surface normal, wherein the second incident angle is greater than the first incident angle.
2 . The electronic device defined in claim 1 , wherein the first incident angle is 0 degrees and wherein the second incident angle is greater than 65 degrees.
3 . The electronic device defined in claim 1 , wherein the display cover layer has a first refractive index, wherein water has a second refractive index, wherein an interface between a water droplet and the display cover layer has an associated critical angle based on the first refractive index and the second refractive index, and wherein the first incident angle is less than the critical angle.
4 . The electronic device defined in claim 1 , wherein the light has a wavelength, the first transmission is at the wavelength, the second transmission is at the wavelength, and the wavelength is a near infrared wavelength.
5 . The electronic device defined in claim 1 , further comprising:
additional interference filters that are formed over the light source.
6 . The electronic device defined in claim 5 , wherein the additional interference filters comprise:
a third interference filter having a third transmission for light at a third incident angle relative to the surface normal, and
a fourth interference filter having a fourth transmission for light at a fourth incident angle relative to the surface normal,
wherein the fourth incident angle is greater than the third incident angle, and wherein the fourth transmission is less than the third transmission.
7 . The electronic device defined in claim 6 , wherein the display cover layer has a first refractive index, wherein air has a second refractive index, wherein an interface between air and the display cover layer has an associated critical angle based on the first refractive index and the second refractive index, and wherein the third incident angle is less than the critical angle.
8 . The electronic device defined in claim 5 , wherein each one of the additional interference filters comprises multiple sublayers with alternating index of refraction values.
9 . The electronic device defined in claim 1 , wherein each one of the interference filters comprises multiple sublayers with alternating index of refraction values.
10 . The electronic device defined in claim 1 , wherein each one of the interference filters comprises alternating layers of glass and silver.
11 . The electronic device defined in claim 10 , wherein each one of the interference filters comprises:
a first sublayer formed from glass;
a second sublayer formed from silver;
a third sublayer formed from glass; and
a fourth sublayer formed from silver.
12 . The electronic device defined in claim 11 , wherein the second sublayer has a thickness of less than 100 nanometers, wherein the third sublayer has a thickness of less than 1,000 nanometers, and wherein the fourth sublayer has a thickness of less than 100 nanometers.
13 . The electronic device defined in claim 1 , further comprising:
additional filters, wherein each additional filter is adjacent to a respective interference filter and formed over the light detector.
14 . The electronic device defined in claim 13 , wherein the additional filters block visible light.
15 . The electronic device defined in claim 13 , wherein the additional filters have a same transmission at the first incident angle as at the second incident angle.
16 . The electronic device defined in claim 1 , wherein the optical touch sensor is configured to distinguish between when the surface is contacted by a finger and when the surface is contacted by a water droplet.
17 . An electronic device configured to gather touch input, comprising:
a display having a display cover layer; and
an optical touch sensor comprising:
a light source that emits light toward the display cover layer;
a light detector that detects reflections of the light;
a first interference filter, wherein the first interference filter overlaps the light source; and
a second interference filter, wherein the second interference filter overlaps the light detector.
18 . The electronic device defined in claim 17 , wherein the display cover layer has a surface normal, wherein the first interference filter is configured to pass more light at an on-axis angle that is parallel to the surface normal than at an off-axis angle that is not parallel to the surface normal, and wherein the second interference filter is configured to pass more light at the off-axis angle than at the on-axis angle.
19 . The electronic device defined in claim 17 , wherein each one of the first interference filter and the second interference filter comprises multiple sublayers with alternating index of refraction values.
20 . An electronic device configured to gather touch input, comprising:
a display having a display cover layer; and
an optical touch sensor comprising:
a one light source that emits near-infrared light towards the display cover layer;
a light detector that detects reflections of the near-infrared light;
a first interference filter formed over the light detector, wherein the first interference filter comprises multiple sublayers with alternating index of refraction values, and
a second interference filter formed over the light detector, wherein the second interference filter comprises multiple sublayers with alternative index refraction values,
wherein each of the first interference filter and the second interference filter has different transmission of near-infrared light at different incident angles; and
a visible light blocking filter formed over the light detector.