A time delay integration image sensor may include a number of charge coupled devices (CCDs) that transfer charge in synchronization with the movement of an object being imaged. To increase the dynamic range of the image sensor, the image sensor may include circuitry configured to non-destructively sample the charge as it is transferred through the charge coupled devices. Floating gates may be included in the image sensor and may have a voltage that is proportional to the charge accumulated under the floating gates. Each floating gate may be coupled to a respective readout circuit in an additional substrate by a metal interconnect layer.