Calibrated image-sensor-based ambient light sensor

摘要

An electronic device may be provided with an image sensor for capturing digital images. The image sensor may be used as part of image-sensor-based ambient light sensing circuitry for producing ambient light sensor readings. The image-sensor-based ambient light sensing circuitry may include a reference array. The reference array may be formed from an array of light sensor elements that are matched to elements in the image sensor but that are covered with a light blocking material. Control circuitry can measure current flow into the reference array and the image sensor array and can use current measurements from these arrays in producing a calibrated ambient light sensor reading. The control circuitry may make current measurements by measuring a decay time associated with the voltage of a discharging capacitor. A comparator, pulse generator, and switch may be used in periodically recharging the capacitor. The capacitor may be adjusted to ensure accurate readings.

主权项

1. Image-sensor-based ambient light sensing circuitry, comprising:
an image sensor array; an optically-black reference sensor array; and control circuitry that produces an ambient light sensor reading based on data from the image sensor array and the reference sensor array, wherein the control circuitry is configured to measure current flow into the image sensor array and the reference light sensor array and is configured to produce the ambient light sensor reading based at least partly on how much current flows into the reference sensor array and how much current flows into the image sensor array.