The sensor itself is not fundamentally special. In light-field cameras, the key difference is the microlens array placed in front of a largely standard CMOS/CCD-style sensor.

Those microlenses split incoming light so that rays arriving from different directions are focused onto different sensor pixels. The sensor still only measures light intensity at each pixel; it does not directly detect direction on its own. Directional information is inferred from which pixels under each microlens were hit.

That design also explains why light-field cameras have relatively low final image resolution: many sensor pixels are used to capture angular information for each image sample, so multiple sensor pixels effectively contribute to one output pixel in the rendered image.