An imaging device comprising: a bifocal main lens (12, 112, 212) having two different focal lengths (f1, f2) for two regions (12a, 12b, 112a, 112b, 212a, 212b) of the bifocal main lens; an image sensor (16, 116) having a plurality of pixels configured of two-dimensionally arranged photoelectric converting elements; a bifocal microlens array (14, 14', 114, 214, 314, 414) disposed on an incident plane side of the image sensor, the bifocal microlens array including two microlens groups (14a, 14b, 14'a, 14'b, 14'c, 114a, 114b, 214a, 214b, 314a, 314b, 414a, 414b) having two different focal lengths (f1', f2'), and the microlens array being placed such that the images formed by the bifocal main lens from objects placed at four predefined object planes are re-imaged by the microlens array; and image obtaining means (21, 22, 24, 25, 26, 32, 40, 44, 48, 52, 54) which obtains images from the image sensor, characterized in that: the bifocal main lens has two focal points; the bifocal microlens array has two focal points; and the image obtaining means is adapted to obtain from the image sensor four images respectively of a plurality of focal lengths obtained by combining the bifocal main lens and the bifocal microlens array, and includes a sensor control unit which is adapted to read signals from the pixels of the image sensor for each pixel corresponding to each focal length obtained by combining the bifocal main lens (12, 112, 212) and the bifocal microlens array, wherein two upper images obtained by receiving beams passing through the region of the bifocal main lens having the first focal length and two lower images obtained by receiving beams passing through the region of the bifocal main lens having the second focal length are formed at the image sensor (16, 116) by the two microlens groups (14a, 14b) according to the positions of the microlenses of the microlens groups, and the two upper and two lower images are rearranged to obtain four output images in four focal planes defined by said combining. a bifocal main lens (12, 112, 212) having two different focal lengths (f1, f2) for two regions (12a, 12b, 112a, 112b, 212a, 212b) of the bifocal main lens; an image sensor (16, 116) having a plurality of pixels configured of two-dimensionally arranged photoelectric converting elements; a bifocal microlens array (14, 14', 114, 214, 314, 414) disposed on an incident plane side of the image sensor, the bifocal microlens array including two microlens groups (14a, 14b, 14'a, 14'b, 14'c, 114a, 114b, 214a, 214b, 314a, 314b, 414a, 414b) having two different focal lengths (f1', f2'), and the microlens array being placed such that the images formed by the bifocal main lens from objects placed at four predefined object planes are re-imaged by the microlens array; and image obtaining means (21, 22, 24, 25, 26, 32, 40, 44, 48, 52, 54) which obtains images from the image sensor, characterized in that: the bifocal main lens has two focal points; the bifocal microlens array has two focal points; and the image obtaining means is adapted to obtain from the image sensor four images respectively of a plurality of focal lengths obtained by combining the bifocal main lens and the bifocal microlens array, and includes a sensor control unit which is adapted to read signals from the pixels of the image sensor for each pixel corresponding to each focal length obtained by combining the bifocal main lens (12, 112, 212) and the bifocal microlens array, wherein two upper images obtained by receiving beams passing through the region of the bifocal main lens having the first focal length and two lower images obtained by receiving beams passing through the region of the bifocal main lens having the second focal length are formed at the image sensor (16, 116) by the two microlens groups (14a, 14b) according to the positions of the microlenses of the microlens groups, and the two upper and two lower images are rearranged to obtain four output images in four focal planes defined by said combining. the bifocal main lens has two focal points; the bifocal microlens array has two focal points; and the image obtaining means is adapted to obtain from the image sensor four images respectively of a plurality of focal lengths obtained by combining the bifocal main lens and the bifocal microlens array, and includes a sensor control unit which is adapted to read signals from the pixels of the image sensor for each pixel corresponding to each focal length obtained by combining the bifocal main lens (12, 112, 212) and the bifocal microlens array, wherein two upper images obtained by receiving beams passing through the region of the bifocal main lens having the first focal length and two lower images obtained by receiving beams passing through the region of the bifocal main lens having the second focal length are formed at the image sensor (16, 116) by the two microlens groups (14a, 14b) according to the positions of the microlenses of the microlens groups, and the two upper and two lower images are rearranged to obtain four output images in four focal planes defined by said combining.