Optical proximity sensor system
An apparatus includes a display screen, and an optical proximity sensor module disposed behind the display screen. The optical proximity sensor module includes a light emitter operable to produce light having a wavelength for transmission through the display screen toward a target object, and a light sensor operable to sense light reflected by the target object and having the wavelength. The optical proximity sensor module can includes means for reducing a maximum energy density of a light beam produced by the light emitter. The means for reducing the maximum energy density of the light beam is disposed between the light emitter and the display screen so as to intersect the light beam produced by the light emitter. In some cases, there are multiple light emitters collectively operable to provide sufficient optical energy for proximity sensing without producing a visible spot on the display screen. These and other techniques can help reduce or eliminate display screen distortion caused by energy from the light emitters.
1. An apparatus comprising:
a display screen; and
an optical proximity sensor module disposed behind the display screen, the optical proximity sensor module including:
a plurality of light emitters configured to produce infra-red or near infra-red light for transmission through the display screen toward a target object, and further configured to produce an energy density such that a maximum energy density of light incident on a backside of the display screen is reduced while total energy is maintained to facilitate performance for proximity sensing; and
a light sensor operable to sense infra-red or near infra-red light reflected by the target object,
wherein the plurality of light emitters collectively are configured to provide sufficient optical energy for proximity sensing, the light emitters spreading out the optical energy for the proximity sensing, thereby reducing distortion of the display screen.
2. The apparatus of claim 1 wherein the display screen is an OLED display screen.
3. The apparatus of claim 1 wherein the plurality of light emitters includes a plurality of Vertical Cavity Surface Emitting Lasers each of which is operated so as to produce a maximum energy level of 2.0 mW.
4. The apparatus of claim 1 wherein the plurality of light emitters includes a plurality of Vertical Cavity Surface Emitting Lasers each of which is operated so as to produce a maximum energy level of 1.5 mW.
5. A method comprising:
causing each of a plurality of Vertical Cavity Surface Emitting Lasers (VCSELs) in an optical proximity sensor module disposed behind a display screen to produce infra-red or near infra-red light for transmission through the display screen toward a target object, wherein each of the plurality of VCSELs produces a maximum energy level of 2.0 mW;
sensing infra-red or near infra-red light reflected by the target object; and
processing signals corresponding to the sensed infra-red or near infra-red light for proximity sensing.
6. The method of claim 5 wherein each of the plurality of VCSELs produces a maximum energy level of 1.5 mW.
7. The method of claim 5 including applying a driving current in a range of 2-3 mA to each of the plurality of VCSELs.