The light field camera has aroused more attention for its ability to refocus after the fact. However

researches of light field camera are often restricted by the acquisition of raw image and calibration parameters. Based on the Lytro camera

which is the only off-the-shelf light field camera for ordinary consumers

this paper develops systematical methods for acquisition of light field images

correction， and refocusing. By analyzing the operating principle

algorithms and file structure of the Lytro camera

we present a set of complete schemes that accomplish the data extraction from raw light field

decoding

color correction

calibration and correction for microlens array. Furthermore

based on fractional Fourier transform

a refocus method for light field images is proposed. Experiments demonstrate that our systematical scheme is feasible and correct

and the refocus method has satisfactory performance. This paper presents the methods for acquisition and calibration of light field images and then implements the refocusing in frequency domain by using the fractional Fourier transform. Experimental results from two Lytro cameras verify that our proposed method can correctly obtain the image data and camera parameters

and the refocusing algorithm exhibits better performance.