I use a camera unit which has a charge coupled device as the imaging part with the signal processing included in a single board unit which costs £15 in 1000 unit orders so its intended for things such as closed circuit security applications and so on, it produces standard video output,several chinese sources .
The CMOS image sensors are more expansive than CCD type sensors as they are more sensitive and can be read like standard memory devices and some have i2c interfaces.Trouble is they are quite expensive.