Systems and methods for modulated image capture

A method for measuring an amount of first conductivity-type mobile charges associated with a flux of photons received by a pixel element, the pixel element comprising

• a semiconductor substrate,
• a first primary charge-collection node,
• a second primary charge-collection node, a first modulating node,
• a second modulating node and a circuitry comprising a first switch and a second switch, the method comprising:
• (i) depleting a volume inside of the semiconductor substrate by setting a bias voltage (Vbs) to a value that depletes the volume of the semiconductor substrate by at least 50%;
• (ii) providing a first reset voltage (Vr_a);
• (iii) providing a second reset voltage (Vr_b);
• (iv) resetting the first primary charge-collection node by:
• connecting the first primary charge-collection node to the first reset voltage (Vr_a) by turning the first switch ON;
• and
• disconnecting the first primary charge-collection node from the first reset voltage (Vr_a) by turning the first switch OFF;
• (v) resetting a second primary charge-collection node by:
• connecting the second primary charge-collection node to the second reset voltage (Vr_b) by turning a second switch ON;
• and
• disconnecting the second primary charge-collection node from the second reset voltage (Vr_b) by turning the second switch OFF;
• (vi) accumulating the first conductivity-type mobile charges to the first and second primary charge-collection nodes during a cycle of:
• decreasing a first charge-collection volume by setting a first modulating voltage (Vm_a) to a value that increases a first reverse bias voltage between the first primary charge-collection node and the first modulating node, and increasing a second charge-collection volume by setting a second modulating voltage (Vm_b) to a value that decreases a second reverse bias voltage between the second primary charge-collection node and the second modulating node;
• waiting for a first period of time;
• after the first period of time, increasing the first charge-collection volume by setting the first modulating voltage (Vm_a) to a value that decreases the first reverse bias voltage between the first primary charge-collection node and the first modulating node, and decreasing the second charge-collection volume by setting the second modulating voltage (Vm_b) to a value that increases the second reverse bias voltage between the second primary charge-collection node and the second modulating node;
• and
• waiting for a second period of time;
• and
• (vii) measuring the amount of the first conductivity-type mobile charges accumulated during the cycle of the step (vi) by determining voltage levels (Vc_a, Vc_b) of the first primary charge-collection node and the second primary charge-collection node.

A method for measuring an amount of first conductivity-type mobile charges associated with a flux of photons received by a pixel element, the pixel element comprising

• a semiconductor substrate,
• a first primary charge-collection node,
• a secondary charge-collection node,
• a first modulating node,
• a peripheral node and
• a circuitry comprising a first switch,
• the method comprising:
• (a) depleting a volume inside of the semiconductor substrate by setting a bias voltage (Vbs) to a value that depletes the volume of the semiconductor substrate by at least 50%;
• (b) providing a first reset voltage (Vr);
• (c) providing a third voltage (Vx);
• (d) resetting the first primary charge-collection node by:
• connecting the first primary charge-collection node to the first reset voltage (Vr) by turning the first switch ON;
• and
• disconnecting the first primary charge-collection node from the first reset voltage (Vr) by turning the first switch OFF;
• (e) accumulating the first conductivity-type mobile charges to the first primary charge collection node and the secondary charge-collection node during a cycle of:
• decreasing a first charge-collection volume by setting a first modulating voltage (Vm) to a value that increases a first reverse bias voltage between the first primary charge-collection node and the first modulating node, and increasing a second charge-collection volume by setting the third voltage (Vx) to a value that increases a third reverse bias voltage between the secondary charge-collection node and the peripheral node;
• waiting for a third period of time;
• after the third period of time, increasing the first charge-collection volume by setting the first modulating voltage (Vm, Vm) to a value that decreases the first reverse bias voltage between the first primary charge-collection node and the first modulating node, and decreasing the second charge-collection volume by setting the third voltage (Vx) to a value that decreases the third reverse bias voltage between the secondary charge-collection node and the peripheral node;
• and
• waiting for a fourth period of time;
• and
• (f) measuring the amount of the first conductivity-type mobile charges accumulated during the cycle of the step (e) by determining a voltage level (Vc) of the first primary charge-collection node.