A method and an image sensor circuit (2) for providing a bit stream pulse modulated signal at a controlled bit rate. The image sensor circuit (2) has a two-dimensional array of pixel signal pulse frequency modulators (22) each having a photodiode (32) for converting incident light into a varying signal voltage and a frequency-to-digital converter which generates a pulse frequency modulated signal from the varying signal voltage. The circuit 2 also has a sampling unit (24) which samples the pulse frequency modulated signal to generate the bit stream pulse modulated signal at said controlled bit rate. An arithmetic unit (26) is coupled to an output of the sampling unit (24) for performing stochastic processing on the bit stream pulse modulated signal.
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