Combined linear-logarithmic image sensor

摘要

An image sensor has an array of pixels each of which comprises a photodiode (P) in circuit with a semiconductor device (M2) to define a node (pix). The pixel can be operated in linear mode with reset voltage (Vrt) applied via device M4. The pixel can also be operated in logarithmic mode by asserting 'logsel' to enable device M2 to conduct the photocurrent. In logarithmic mode, means are provided for calibrating the pixels to remove fixed pattern noise. The pixels may be operated in linear and log modes sequentially, with the linear output being selected for low light signals and the log output being selected for high light signals. <IMAGE>