Abstract: A threshold detection circuit includes a plurality of capacitors. A plurality of switching circuits is coupled to the capacitors such that a first end of each of the capacitors is coupled to a corresponding photon sensor during detection intervals, and the first end of each capacitor is coupled to a variable initialization value during reset intervals. A threshold number of the capacitors are initialized to a first value and the remaining capacitors are initialized to a second value during reset intervals. A comparator is coupled to a second of the capacitors to generate a detection event in response to the threshold number of photon sensors sensing one or more incident photons during detection intervals.

Abstract: A threshold detection circuit includes a plurality of capacitors. A plurality of switching circuits is coupled to the capacitors such that a first end of each of the capacitors is coupled to a corresponding photon sensor during detection intervals, and the first end of each capacitor is coupled to a variable initialization value during reset intervals. A threshold number of the capacitors are initialized to a first value and the remaining capacitors are initialized to a second value during reset intervals. A comparator is coupled to a second of the capacitors to generate a detection event in response to the threshold number of photon sensors sensing one or more incident photons during detection intervals.

Abstract: An image sensor for detecting light-emitting diode (LED) without flickering includes a pixel array with pixels. Each pixel including subpixels including a first and a second subpixel, dual floating diffusion (DFD) transistor, and a capacitor coupled to the DFD transistor. First subpixel includes a first photosensitive element to acquire a first image charge, and a first transfer gate transistor to selectively transfer the first image charge from the first photosensitive element to a first floating diffusion (FD) node. Second subpixel includes a second photosensitive element to acquire a second image charge, and a second transfer gate transistor to selectively transfer the second image charge from the second photosensitive element to a second FD node. DFD transistor coupled to the first and the second FD nodes. Other embodiments are also described.

Abstract: Apparatuses and methods for image sensors with pixels that reduce or eliminate flicker induced by high intensity illumination are disclosed. An example image sensor may include a photodiode, a transfer gate, an anti-blooming gate, and first and second source follower transistors. The photodiode may capture light and generate charge in response, and the photodiode may have a charge capacity. The transfer gate may selectively transfer charge to a first floating diffusion, and the anti-blooming gate may selectively transfer excess charge to a second floating diffusion when the generated charge is greater than the photodiode charge capacity.

Abstract: Apparatuses and methods for image sensors with pixels that reduce or eliminate flicker induced by high intensity illumination are disclosed. An example image sensor may include a photodiode, a transfer gate, an anti-blooming gate, and first and second source follower transistors. The photodiode may capture light and generate charge in response, and the photodiode may have a charge capacity. The transfer gate may selectively transfer charge to a first floating diffusion, and the anti-blooming gate may selectively transfer excess charge to a second floating diffusion when the generated charge is greater than the photodiode charge capacity.

Abstract: An image sensor for detecting light-emitting diode (LED) without flickering includes a pixel array with pixels. Each pixel including subpixels including a first and a second subpixel, dual floating diffusion (DFD) transistor, and a capacitor coupled to the DFD transistor. First subpixel includes a first photosensitive element to acquire a first image charge, and a first transfer gate transistor to selectively transfer the first image charge from the first photosensitive element to a first floating diffusion (FD) node. Second subpixel includes a second photosensitive element to acquire a second image charge, and a second transfer gate transistor to selectively transfer the second image charge from the second photosensitive element to a second FD node. DFD transistor coupled to the first and the second FD nodes. Other embodiments are also described.

Abstract: An image sensor, readout circuitry for an image sensor, and a method of operating readout circuitry are disclosed. Readout circuitry includes an analog-to-digital-converter (“ADC”) including input stage circuitry with a first selectable input and a second selectable input. The ADC is coupled to sequentially receive a first reset signal, a second reset signal, a high gain image signal, and a low gain image signal, in that order. The input stage circuitry is configured to select the first selectable input when receiving the first reset signal and the low gain image signal and select the second selectable input when receiving the second reset signal and the high gain image signal.

Abstract: An image sensor includes a pixel array including a plurality of pixel cells each including a floating diffusion node, a photosensitive element coupled to selectively transfer image charge to the floating diffusion node, and a feedback coupling capacitor coupled between the floating diffusion node and an output line. A bit line is coupled to selectively readout image data output from each one of a group of the plurality of pixel cells. An integrator is capacitively coupled to the bit line. The integrator is coupled to output an output signal on the output line in response to the image data. The output signal on the output line is capacitively coupled to the floating diffusion node through the feedback coupling capacitor to suppress a potential swing at the floating diffusion node of each one of the group of the plurality of pixel cells in response to the output signal.

Abstract: An image sensor includes a pixel array including a plurality of pixel cells each including a floating diffusion node, a photosensitive element coupled to selectively transfer image charge to the floating diffusion node, and a feedback coupling capacitor coupled between the floating diffusion node and an output line. A bit line is coupled to selectively readout image data output from each one of a group of the plurality of pixel cells. An integrator is capacitively coupled to the bit line. The integrator is coupled to output an output signal on the output line in response to the image data. The output signal on the output line is capacitively coupled to the floating diffusion node through the feedback coupling capacitor to suppress a potential swing at the floating diffusion node of each one of the group of the plurality of pixel cells in response to the output signal.

Abstract: Electronic devices may be provided with image sensors. Image sensors may be configured to capture images during imaging operations and monitor ambient light levels during non-imaging operations. An image sensor may include image pixels that receive light and dark pixels that are prevented from receiving light. An image sensor may include an ambient light detection circuit. The ambient light detection circuit may include an oscillator, timing and control circuitry, and a counter. The oscillator may be switchably coupled to the image pixels and the dark pixels. The counter may be configured to count up oscillator cycles of the oscillator while the oscillator is coupled to the image pixels and to count down oscillator cycles of the oscillator while the oscillator is coupled to the dark pixels. The counter may provide a count value that depends on a signal from the image pixels and a signal from the dark pixels.

Abstract: Dual conversion gain pixel methods, system, and apparatus are disclosed. Dual conversion gain may be obtained by configuring an active pixel having a storage node, a first connection region, a second connection region, and a capacitor coupled between the storage node and the second connection region to introduce a first conversion gain by connecting the first connection region to a power source and connecting the second connection region to a current bias source and reconfiguring the active pixel to introduce a second conversion gain by connecting the second connection region to the power source and connecting the first connection region to the current bias source.

Abstract: Electronic devices may be provided with image sensors. Image sensors may be configured to capture images during imaging operations and monitor ambient light levels during non-imaging operations. An image sensor may include image pixels that receive light and dark pixels that are prevented from receiving light. An image sensor may include an ambient light detection circuit. The ambient light detection circuit may include an oscillator, timing and control circuitry, and a counter. The oscillator may be switchably coupled to the image pixels and the dark pixels. The counter may be configured to count up oscillator cycles of the oscillator while the oscillator is coupled to the image pixels and to count down oscillator cycles of the oscillator while the oscillator is coupled to the dark pixels. The counter may provide a count value that depends on a signal from the image pixels and a signal from the dark pixels.

Abstract: Embodiments of circuits and methods for suppressing row-wise noise in the analog domain in an image sensing device. In one embodiment, a pixel sampling circuit includes a readout circuit that is connected to a plurality of pixels to receive analog signals from the pixels. The pixel sampling circuit also includes a noise correction circuit that provides a reference signal to remove at least a portion of the noise in the analog signals received from the pixels before the analog signals are converted into digital signals.

Abstract: Dual conversion gain pixel methods, system, and apparatus are disclosed. Dual conversion gain may be obtained by configuring an active pixel having a storage node, a first connection region, a second connection region, and a capacitor coupled between the storage node and the second connection region to introduce a first conversion gain by connecting the first connection region to a power source and connecting the second connection region to a current bias source and reconfiguring the active pixel to introduce a second conversion gain by connecting the second connection region to the power source and connecting the first connection region to the current bias source.

Abstract: An imager architecture that utilizes column sampling circuitry that can support pixel-wise automatic gain selection (AGS). The column sampling circuitry samples the pixel output signals directly (e.g., with unity gain) or after amplification in a column level amplifier while supporting correlated double sampling (CDS) in both situations.

Abstract: Apparatus and methods provide an operational transconductance amplifier (OTA) with one or more self-biased cascode current mirrors. Applicable topologies include a current-mirror OTA and a folded-cascode OTA. In one embodiment, the self-biasing cascode current mirror is an optional aspect of the folded-cascode OTA. The self-biasing can advantageous reduce the number of biasing circuits used, which can save chip area and cost. One embodiment includes an input differential pair of a current-mirror OTA.

Abstract: An imager architecture that utilizes column sampling circuitry that can support pixel-wise automatic gain selection (AGS). The column sampling circuitry samples the pixel output signals directly (e.g., with unity gain) or after amplification in a column level amplifier while supporting correlated double sampling (CDS) in both situations.

Abstract: An imaging method and apparatus which use a pixel array for capturing images and for measuring ambient light conditions.

Abstract: Embodiments of circuits and methods for suppressing row-wise noise in the analog domain in an image sensing device. In one embodiment, a pixel sampling circuit includes a readout circuit that is connected to a plurality of pixels to receive analog signals from the pixels. The pixel sampling circuit also includes a noise correction circuit that provides a reference signal to remove at least a portion of the noise in the analog signals received from the pixels before the analog signals are converted into digital signals.

Abstract: Apparatus and methods provide an operational transconductance amplifier (OTA) with one or more self-biased cascode current mirrors. Applicable topologies include a current-mirror OTA and a folded-cascode OTA. In one embodiment, the self-biasing cascode current mirror is an optional aspect of the folded-cascode OTA. The self-biasing can advantageous reduce the number of biasing circuits used, which can save chip area and cost. One embodiment includes an input differential pair of a current-mirror OTA.