The paper says regarding the works of Ren Ng, Lytro founder: A "reason that it took some time for the plenoptic technology to take hold is that the initial plenoptic camera design, as for example implemented by Ng in 2005, generates refocused images whose number of pixels equals the number of micro lenses. That is, even when using a high resolution sensor with 16 mega pixels, say and a micro lens array with 40000 lenses, the refocused images have a resolution of 40000 pixels. For many applications this is not a practicable resolution."
The paper continues: "a new type of plenoptic camera is introduced here, called the multi-focus plenoptic camera (MFPC), whose micro lens array consists of micro lenses with different focal lengths. A MFPC can therefore be regarded as a number of interlaced single focus plenoptic cameras. It is shown that a MFPC extends the depth of field compared to a single focus plenoptic camera and still allows effective lateral resolutions at up to one quarter of the sensor resolution."
