Abstract: An image sensor may include adaptive filtering circuitry that is used to correct for row noise. In one example, the image sensor may include a single reference pixel or a column of reference pixels that are shielded from incident light. The adaptive filtering circuitry may estimate row noise based on data from the reference pixel(s). Row noise correction circuitry may then subtract the estimated row noise from imaging pixel outputs to correct for row noise. If the row noise is dominated by supply noise, the reference pixels may be omitted entirely and the adaptive filtering circuitry may estimate row noise based only on the power supply voltage. The adaptive filtering circuitry may undergo a training phase to optimize coefficients for the adaptive filtering circuitry.

Abstract: An image sensor may include an array of imaging pixels arranged in rows and columns. Each column of imaging pixels may be coupled to a respective column output line that is used to read out samples from the imaging pixels. Each column output line may be coupled to a respective switched capacitor low-pass filter that is used to filter out high-frequency noise during readout. The switched capacitor includes a capacitor, a first transistor that is coupled between the capacitor and the column output line, and a second transistor that is coupled between the capacitor and an additional capacitor. The first and second transistors are repeatedly, alternatingly asserted at a frequency that is selected based on a target cutoff frequency for the low-pass filter.

Abstract: An image sensor may use a physical unclonable function (PUF) to generate a unique identifier that may be used for security. Physical unclonable functions utilize variations that occur during manufacturing to generate a unique identifier that may be used to generate a secure encryption key. In an image sensor, analog-to-digital converters may provide the foundation for the physical unclonable function. An image sensor may include an array of imaging pixels having rows and columns, a plurality of analog-to-digital converters, and processing circuitry that is configured to generate a unique identifier based on outputs from the plurality of analog-to-digital converters. The processing circuitry may concatenate one or more bits from test outputs from the analog-to-digital converters to generate the unique identifier.

Abstract: An image sensor may use a physical unclonable function (PUF) to generate a unique identifier that may be used for security. Physical unclonable functions utilize variations that occur during manufacturing to generate a unique identifier that may be used to generate a secure encryption key. In an image sensor, analog-to-digital converters may provide the foundation for the physical unclonable function. An image sensor may include an array of imaging pixels having rows and columns, a plurality of analog-to-digital converters, and processing circuitry that is configured to generate a unique identifier based on outputs from the plurality of analog-to-digital converters. The processing circuitry may concatenate one or more bits from test outputs from the analog-to-digital converters to generate the unique identifier.

Abstract: An image sensor may include adaptive filtering circuitry that is used to correct for row noise. In one example, the image sensor may include a single reference pixel or a column of reference pixels that are shielded from incident light. The adaptive filtering circuitry may estimate row noise based on data from the reference pixel(s). Row noise correction circuitry may then subtract the estimated row noise from imaging pixel outputs to correct for row noise. If the row noise is dominated by supply noise, the reference pixels may be omitted entirely and the adaptive filtering circuitry may estimate row noise based only on the power supply voltage. The adaptive filtering circuitry may undergo a training phase to optimize coefficients for the adaptive filtering circuitry.

Abstract: An image sensor may include an array of image pixels arranged in rows and columns. A first portion of the array may include active pixels that are read out using first analog-to-digital converter (ADC) circuits. A second portion of the array may include dark reference pixels that are read out using second analog-to-digital converter (ADC) circuits. The first ADC circuits may have a first sampling rate, a first resolution, and a first size. The second ADC circuits may have an oversampling rate that is greater than the first sampling rate, a second resolution that is greater than the first resolution, and a second size that is bigger than the first size. Configured in this way, the second ADC circuits may perform averaging of a row noise via direct time-domain oversampling, which can help dramatically reduce the number of dark reference pixel columns in the array.