Just a detail about the sensor chip. Traditionally, the sensor chip has its metalization layer(s) on the same surface as is exposed to the light of your image. The metalization is patterned into wires that interconnect everything to allow reading the image from the sensors.
For technical reasons, metalization is normally one of the, it not THE, last layers to go on a chip, which means it's normally "on top". On a image sensor, having the metalization on top means that some of the image light is blocked by the wiring, which cuts the sensitivity somewhat.
"Backside Illumination" means that they have built the chip so that the sensors are on the BACK, opposite the metalization. This increases the sensitivity since there's no wiring blocking light.
Making chips this way is rather more expensive; in making chips, all deposition and imaging is done on the front side. To put the sensors on the back they bury them at the bottom of the front side, bond the wafer to a carrier and remove most of the backside thickness to expose the buried sensors. There's a nice
process flow diagram here, for those familiar with chip fab processes.