An imaging device comprising: an image sensor comprising: a frame memory configured to record a main pixel signal; a pixel array unit comprising normal imaging pixels and focus detection pixels, and circuitry (111, 112, 113, 114) configured to respectively control an exposure of the focus detection pixels and an exposure of the normal imaging pixels of the pixel array unit; to readout from the focus detection pixels of the pixel array unit a focus pixel signal, to readout from the normal imaging pixels of the pixel array unit the main pixel signal, the focus pixel signal being used in an auto focus operation, and the main pixel signal being used to generate an image, to record the main pixel signal in the frame memory; to output the focus pixel signal from the pixel array unit; and to output the main pixel signal from the frame memory after the exposure of the normal imaging pixels, the readout of the main pixel signal and the recording of the main pixel signal to the frame memory, the focus pixel signal and the main pixel signal being output independently as separate signals; an image processing unit configured to accept, as input, the focus pixel signal and the main pixel signal independently from each other, the image processing unit being configured to conduct a phase difference detection on a basis of the focus pixel signal and provide a result of the phase difference detection to a lens driving controller; and the lens driving controller is configured to receive the result of the phase difference detection from the image processing unit and issue driving instructions used to drive a focus lens during the output of the main pixel signal from the frame memory to the image processing unit, wherein the driving instructions are based on a lens driving amount computed during the auto focus operation on a basis of a position of the focus lens during the exposure of the focus detection pixels and a subject distance measured in the phase difference detection, the exposure of the focus detection pixels and the normal imaging pixels occurring during a same pre-determined shooting interval. a frame memory configured to record a main pixel signal; a pixel array unit comprising normal imaging pixels and focus detection pixels, and circuitry (111, 112, 113, 114) configured to respectively control an exposure of the focus detection pixels and an exposure of the normal imaging pixels of the pixel array unit; to readout from the focus detection pixels of the pixel array unit a focus pixel signal, to readout from the normal imaging pixels of the pixel array unit the main pixel signal, the focus pixel signal being used in an auto focus operation, and the main pixel signal being used to generate an image, to record the main pixel signal in the frame memory; to output the focus pixel signal from the pixel array unit; and to output the main pixel signal from the frame memory after the exposure of the normal imaging pixels, the readout of the main pixel signal and the recording of the main pixel signal to the frame memory, the focus pixel signal and the main pixel signal being output independently as separate signals; to respectively control an exposure of the focus detection pixels and an exposure of the normal imaging pixels of the pixel array unit; to readout from the focus detection pixels of the pixel array unit a focus pixel signal, to readout from the normal imaging pixels of the pixel array unit the main pixel signal, the focus pixel signal being used in an auto focus operation, and the main pixel signal being used to generate an image, to record the main pixel signal in the frame memory; to output the focus pixel signal from the pixel array unit; and to output the main pixel signal from the frame memory after the exposure of the normal imaging pixels, the readout of the main pixel signal and the recording of the main pixel signal to the frame memory, the focus pixel signal and the main pixel signal being output independently as separate signals; an image processing unit configured to accept, as input, the focus pixel signal and the main pixel signal independently from each other, the image processing unit being configured to conduct a phase difference detection on a basis of the focus pixel signal and provide a result of the phase difference detection to a lens driving controller; and the lens driving controller is configured to receive the result of the phase difference detection from the image processing unit and issue driving instructions used to drive a focus lens during the output of the main pixel signal from the frame memory to the image processing unit, wherein the driving instructions are based on a lens driving amount computed during the auto focus operation on a basis of a position of the focus lens during the exposure of the focus detection pixels and a subject distance measured in the phase difference detection, the exposure of the focus detection pixels and the normal imaging pixels occurring during a same pre-determined shooting interval.