Event sensor and method for generating a signal stream comprising event data

An event sensor comprising:

• a pixel array;
• a photovoltaic convert er for each pixel of the pixel array;
• an electronic converter for each pixel of the pixel array, said electronic converter connected to said photovoltaic converter;
• a multi-bit digital storage for, and corresponding to, each pixel of the pixel array, said multi-bit digital storage configured to store pixel parameters for each pixel, including a previous pixel value and a pixel-specific change-detection threshold;
• and
• a readout processor connected to said electronic converter and said multi-bit digital storage, said readout processor including a plurality of processing blocks;
• wherein:
• the event sensor is configured to produce a signal stream comprising event data in reaction to light incident on said pixel array;
• said photovoltaic converter and said electronic converter are configured to produce and store a digital current pixel value, which is dependent on an intensity of light incident on said photovoltaic converter;
• said readout processor is configured to generate a pixel event value of said event data based on a pixel subtraction result of subtracting said previous pixel value from said current pixel value;
• wherein the event sensor is configured to support two basic operation modes, one of which is a temporal contrast event mode, which starts with a pixel-parallel conversion of a light-intensity-dependent analog voltage into the digital current pixel value and storing the digital current pixel value in a converter memory of said electronic converter in a synchronous global-shutter fashion, and wherein then the readout processor reads the current pixel values from the pixel array row by row and simultaneously the corresponding pixel parameters of the same row of pixels from memory, the information transfer between the pixel array, the memory and the readout processor being coordinated by a readout controller, wherein each processing block of the plurality of processing blocks is configured to perform the following processing steps to decide whether to output a temporal contrast event from the corresponding pixel:
• receive a current pixel value and corresponding pixel parameters of the same pixel;
• compute a signed difference between the current and the previous pixel values;
• decide if the signed difference exceeds a positive or negative change-detection threshold, which is the pixel-specific change-detection threshold of the corresponding pixel, if yes, request a temporal contrast event output and update the corresponding pixel parameters, including overwriting the previous pixel value with the current pixel value;
• wherein another basic operation mode is logarithmic intensity frame mode, which starts with capturing a frame of current pixel values and storing the frame in the converter memories of in-pixel ADCs in a synchronous global-shutter fashion, and
• wherein the readout processor reads the current pixel values and corresponding parameters row-by-row;
• wherein each processing block performs the following steps to correct inter-pixel gain and offset mismatch in the current pixel value:
• receiving the current pixel value and corresponding parameters of the same pixel;
• converting the current pixel value from Gray code to binary format;
• computing an offset-compensated pixel value by subtracting an offset compensator of the corresponding pixel from the current pixel value;
• computing a final offset-compensated and gain-corrected pixel value by multiplying the offset-compensated pixel value with a gain correction factor of the corresponding pixel.