A light field camera is a new imaging apparatus that can record both light intensity information and depth information (that is, complete light field information) of an object, and is widely used due to advantages such as digital refocusing. Currently, a light field camera mainly includes five parts: a main lens 1, a flat imaging array 2, a flat image sensor 3, an image processor 3, a drive 4, and a controller 5, as specifically shown in FIG. 1A.
The main lens 1 of the light field camera is generally a non-wide-angle lens, and the non-wide-angle main lens 1 images a shot object. A plane on which the image is located is an image plane (a plane a shown in FIG. 1A) of the non-wide-angle main lens 1. The image plane of the non-wide-angle main lens 1 is a virtual plane that is located between the non-wide-angle main lens 1 and the flat imaging array 2 and that is perpendicular to an optical axis. The optical axis is an axis parallel to a horizontal plane. An image distance (a distance b shown in FIG. 1A) of the non-wide-angle main lens 1 is a vertical distance between a side, near the flat imaging array 2, of the non-wide-angle main lens 1 and the virtual image plane a of the non-wide-angle main lens 1. An object plane (a plane c shown in FIG. 1A) of the non-wide-angle main lens 1 is a plane, near the side of the light field camera, of the shot object. An object distance (a distance d shown in FIG. 1A) of the non-wide-angle main lens 1 is a vertical distance between a side, near the shot object, of the non-wide-angle main lens 1 and the object plane of the non-wide-angle main lens 1.
A flat microlens array e includes multiple microlenses g, and the flat microlens array e needs to reimage an image generated on the virtual image plane a of the non-wide-angle main lens 1. A plane on which a reimaged image is located is a virtual image plane (a plane h shown in FIG. 1A) of the flat microlens array e. A plane including images generated by all the microlenses g is the virtual image plane h of the flat microlens array e. An image distance (a distance i shown in FIG. 1A) of the flat microlens array e is a vertical distance between a side, near the image processor 3, of the flat microlens array e and the virtual image plane h of the flat microlens array e. An object plane of the flat microlens array e is the virtual image plane a of the non-wide-angle main lens 1. An object distance (a distance j shown in FIG. 1A) of the flat microlens array e is a distance between a side, near the non-wide-angle main lens 1, of the flat microlens array e and the equivalent image plane a of the non-wide-angle main lens 1.
A relationship among the object distance j of the flat microlens array e, the image distance i of the flat microlens array e, and an equivalent focal length l of the flat microlens array e meets a formula 1/l=1/j+1/i. The flat microlens array e needs to reimage the image generated on the virtual image plane a of the non-wide-angle main lens 1. Actually, each microlens g in the flat microlens array e needs to reimage the image generated on the virtual image plane a of the non-wide-angle main lens 1. Therefore, each microlens g in the flat microlens array e also has a corresponding microlens object distance jn, a microlens equivalent image distance in, and a microlens equivalent focal length ln, and jn, in, and ln meet a formula 1/1n=1/jn+1/in, where n is a number of a microlens. In FIG. 1A, numbers of all the microlenses g in the flat microlens array e are sequentially a number 1, a number 2, a number 3, a number 4, a number 5, a number 6, a number 7, and a number 8 from top to bottom.
In an imaging process, after reimaging the image formed on the virtual image plane a of the non-wide-angle main lens 1, the flat microlens array e needs to record the image on a flat image sensor f. In this case, if the virtual image plane h of the flat microlens array e coincides with a plane on which the flat image sensor f is located, or a vertical distance between the virtual image plane h of the flat microlens array e and a plane on which the flat image sensor f is located falls within a preset range, a finally shot image has high quality and is relatively clear. That is, when an image formed by each microlens g in the flat microlens array e is on the flat image sensor f, or when a vertical distance between the virtual image plane h on which the formed image is located and the flat image sensor f falls within a preset range, a finally shot image has high quality and is relatively clear.
Currently, a wide-angle main lens can collect a light ray with a larger incident angle than a non-wide-angle main lens, that is, has a larger visual angle. For example, a wide-angle main lens may have a visual angle of 180° or even 270° and can shoot more objects in space. Therefore, it is extremely important to replace a non-wide-angle main lens used in an existing light field camera with a wide-angle main lens. As shown in FIG. 1B, when a non-wide-angle main lens 1 used in the existing light field camera is replaced with a wide-angle main lens 1′, an object plane of a flat microlens array e is a virtual image plane a′ of the wide-angle main lens 1′, a virtual image plane of the flat microlens array e is h′, and an equivalent focal plane of the flat microlens array e is k′. When the non-wide-angle main lens used in the existing light field camera is replaced with the wide-angle main lens, because all microlenses are the same, the microlenses have a fixed refractive index to a light ray, that is, focal lengths ln of all the microlenses in the flat microlens array e are the same. Because a virtual image plane of the wide-angle main lens is curved, distances between all the microlenses g in the flat microlens array e and the virtual image plane of the wide-angle main lens are different, that is, object distances jn of all the microlenses are different. It may be learned according to the relationship among the object distance of each microlens, the image distance of each microlens, and the focal length of each microlens that are shown in the foregoing formula that, object distances in of all the microlenses in the flat microlens array e are different. Because distances between all the microlenses g in the flat microlens array e and a flat image sensor f are the same, but image distances of all the microlenses g in the flat microlens array e are different, as specifically shown in FIG. 1B, after some microlenses g in the flat microlens array e reimage an image formed on the virtual image plane a′ of the wide-angle lens, a virtual image plane on which the formed image is located is on the flat image sensor f, or a distance between a virtual image plane on which the formed image is located and the image sensor f falls within a preset range, and after the other microlenses g in the flat microlens array e reimage the image formed on the virtual image plane a′ of the wide-angle lens, a vertical distance between a virtual image plane on which the image formed by reimage is located and the image sensor f has exceeded the preset range, thereby resulting in poor quality of a finally shot image and generating an aberration such as blurring or distortion.
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