Sensor dark pixel offset estimation

Abstract

Examples of systems and methods to provide estimates of dark current for pixels of a photosensor as a function of the temperature of the sensor and the gain applied to the photosensor are described. In various implementations, the dark current estimated for each pixel can depend at least partly on a global scale factor and a global bias that depend on temperature and gain and a temperature-independent and gain-independent offset value for each pixel. The scale, bias, and offsets may be determined from multiple dark field images taken by the sensor over a range of operating temperatures. In some cases, the scale and bias can be determined using a subset of less than all the image pixels. Scale and bias derived for a particular sensor can be used in the calibration of different sensors.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit under 35 U.S.C. §119(e) of U.S. Patent Application No. 61 / 625,322, filed Apr. 17, 2012, entitled “Sensor Dark Pixel Offset Estimation;” the entire disclosure of which is hereby incorporated by reference herein so as to form part of this specification.BACKGROUND[0002]1. Field[0003]The present disclosure relates generally to calibrating sensors such as, for example, photosensors, which have pixel-dependent noise or bias.[0004]2. Description of Related Art[0005]Photosensors can be used to detect the amount of light incident on the image sensor. Photosensors include, for example, devices such as charge-coupled devices (CCDs) in which each pixel includes a photoactive capacitor, and active pixel image sensors in which each pixel includes a light sensor and an active amplifier. The amplifier can provide a programmable or switchable gain for each pixel. Active pixel image sensors produced by complementary meta...

AI Technical Summary

Benefits of technology

The patent describes a method and system for calibrating a plurality of pixels on a sensor to correct for dark current. The method involves accessing a scale factor and a bias factor for each pixel, which are determined based on the temperature and gain of the photosensor. The method also involves accessing a pixel value representing the response of each pixel to light, and an offset value for each pixel. By performing the calibration using global and local factors, the method can provide more efficient and accurate calibration for large format sensor arrays compared to individual correction methods for each pixel. The technical effect of the invention is to improve the accuracy of sensor readings and reduce the impact of dark current on sensor performance.

Problems solved by technology

When an image is taken with a photosensor, dark current can act as a source of noise in the resulting image.

Images