Circuits for self-powered image sensors

An image sensor, the image sensor comprising:

• a plurality of pixels, each of the plurality of pixels comprising:
• a photodiode having an anode and a cathode connected to a ground voltage;
• a first transistor having:
• a first input connected to the anode of the photodiode;
• a first output connected to a reset bus;
• and
• a first control configured to receive a discharge signal;
• and
• a comparator having:
• a second input connected to the anode of the photodiode and the first input of the transistor;
• a third input configured to receive a threshold voltage;
• a second output coupled to a pixel output bus;
• and
• a second control configured to receive a select signal and control operation of the comparator based on the selection signal;
• a second transistor having:
• a fourth input coupled to each first output via the reset bus;
• a third output configured to be coupled to an energy storage device;
• and
• a third control configured to receive an energy harvest signal.

A digital camera comprising:

• an energy storage device;
• an image sensor, the image sensor comprising:
• a plurality of pixels, each of the plurality of pixels comprising:
• a photodiode having an anode and a cathode connected to a ground voltage;
• a first transistor having:
• a first input connected to the anode of the photodiode;
• a first output connected to a reset bus;
• and
• a first control configured to receive a discharge signal;
• and
• a second transistor having:
• a second input connected to the anode of the photodiode;
• a second output connected to a pixel output bus;
• and
• a second control configured to receive a select signal;
• and
• a third transistor having:
• a third input coupled to each first output via the reset bus;
• a third output coupled to the energy storage device;
• and
• a third control configured to receive an energy harvest signal;
• and
• a hardware processor that is configured to:
• apply the discharge signal during a first time period;
• inhibit the discharge signal and the select signal during a second time period;
• inhibit the discharge signal during a third time period and apply the select signal during the third time period;
• and
• apply the discharge signal and the energy harvest signal during a fourth time period.