Patent ID: 7804537

Claim:
An image sensor comprising: an array of pixels, each pixel comprising a photodiode, a first output circuit for deriving a linear output signal by applying a reset signal to said photodiode and reading a voltage on said photodiode after an integration time, said first output circuit comprising a reset switch for applying the reset voltage to said photodiode, said reset switch comprising a reset transistor including a conducting terminal connected to said photodiode, and a readout switch for turning on the conducting terminal of said reset transistor after expiration of the integration time, said readout switch comprising a readout transistor including a conducting terminal connected to the conducting terminal of said reset transistor and to said photodiode, and including a control terminal, a second output circuit for deriving a logarithmic output signal by reading a near instantaneous illumination-dependent voltage on said photodiode that is a logarithmic function of the illumination, said second output circuit comprising an amplifier including an output and at least one input connected to the conducting terminal of said reset transistor, to the conducting terminal of said readout transistor and to said photodiode, and a log select switch for connecting said amplifier to said photodiode, said log select switch comprising a log select transistor including a pair of conducting terminals connected between the output of said amplifier and the control terminal of said readout transistor, and including a control terminal to receive a log select signal, and said first and second output circuits sequentially providing the linear and logarithmic output signals; and an output selection circuit coupled to said array of pixels for selecting between the linear output signal and the logarithmic output signal as an output signal.