Optical distance sensing using a target surface having a non-uniform design of regions of different reflectivity

Abstract

An apparatus, e.g. a proximity sensor module (), for optical distance sensing includes a target surface () having a non-uniform design including a high-reflectivity region and a low-reflectivity region for light of a particular wavelength. The position of the target surface () is displaceable within the apparatus. The apparatus includes a light source () operable to emit light at the particular wavelength toward the target surface (), and a photodetector () operable to sense at least some of the light emitted by the light source and subsequently reflected by the target surface (). A processor is operable to correlate an output from the photodetector () with a distance to the target surface (). A wall () may separate the light source () and photodetector () from one another, which can help reduce internal optical crosstalk. The light source () and photodetector () are mounted and electrically coupled to a substrate () that, in turn, can be mounted and electrically coupled to a printed circuit board (PCB) () of a host device. The light source () and photodetector () are surrounded laterally by a spacer or housing wall (). The target surface () may be the backside of a touch interactive display screen () in the host device, e.g., a portable computing device such as a smartphone, tablet, wearable device, personal digital assistant (PDA), or personal computer. Circuitry () can be implemented, for example, as an integrated circuit chip or other processor and may include software and/or a look-up table stored in memory that allows the circuitry () to correlate the measured photodetector signal to a distance. When pressure is provided on the display screen () (e.g., by a person pressing her finger on the screen), the display screen is displaced slightly in the direction of the substrate () on which the light source () and photodetector () are mounted. As a result of the displacement, the intensity of light detected by the photodetector () changes. The signal measured by the photodetector () can be correlated to a distance value. If the distance value is within a specified range (or changes by at least a specified amount), for example, it can trigger some further action in the host device.