An imaging system, comprising:
- An infrared light source;
- and
- an image sensor comprising a plurality of pixel cells, wherein the light source is configured to operate in combination with the image sensor, each pixel cell comprising:
- a pixel set with a plurality of pixels, with each pixel comprising a photodiode and a transfer gate coupled to the photodiode, and with each pixel being sensitive to a near-infrared wavelength range including 940 nm and to at least part of a visible wavelength range;
- and
- a readout circuit comprising:
- a floating diffusion with an adjustable capacitance coupled to all of the transfer gates;
- a column output line;
- a sample-and-hold stage (SHS) coupled to the floating diffusion, the sample-and-hold-stage comprising a first storage stage and a second storage stage arranged in series or in parallel, each of the first and second storage stages comprising a switch and a capacitor that is coupled between the switch and a fixed potential;
- a first switch coupling the sample-and-hold-stage to the column output line;
- and
- a second switch coupling the floating diffusion to the column output line or to a further column output line, wherein the readout circuit is configured to:
- in a global shutter mode of operation,
- control the plurality of pixels such that corresponding charges generated by the photodiode of each of the plurality of pixels in response to incident radiation are simultaneously transferred to the floating diffusion in accordance with transfer control signals simultaneously transmitted to the transfer gates;
- generate a global shutter output signal depending on the corresponding charges from the photodiode of each of the plurality of pixels;
- and
- transfer the global shutter output signal to the column output line in accordance with a global shutter control signal transmitted to the first switch;
- in a rolling shutter mode of operation,
- control the plurality of pixels such that corresponding charges generated by the photodiode of each of the plurality of pixels in response to incident radiation are sequentially transferred to the floating diffusion in accordance with transfer control signals sequentially transmitted to the transfer gates;
- generate individual rolling shutter output signals, with each rolling shutter output signal depending on the corresponding charges from the photodiode of one of the plurality of pixels;
- transfer the individual rolling shutter output signal to the column output line or to the further column output line in accordance with a rolling shutter control signal transmitted to the second switch;
- and
- adjust the capacitance of the floating diffusion such that the capacitance of the floating diffusion in the global shutter mode is larger than the capacitance of the floating diffusion in the rolling shutter mode:
- wherein the image sensor is operated:
- in the global shutter mode for charges generated by the photodiode of each of the plurality of pixels based on incident radiation in a near-infrared wavelength range, wherein the infrared light source is employed for projecting a pattern onto an object or a scene;
- and
- in the rolling shutter mode for charges generated by the photodiode of each of the plurality of pixels based on incident radiation in the visible wavelength range;
- wherein the capacitance of the floating diffusion in the global shutter mode is larger than the capacitance of the floating diffusion in the rolling shutter mode by a factor that is equal to the number of pixels in the pixel cell.