Optical: systems and elements – Single channel simultaneously to or from plural channels – By surface composed of lenticular elements
Patent
1995-12-07
1997-07-22
Epps, Georgia Y.
Optical: systems and elements
Single channel simultaneously to or from plural channels
By surface composed of lenticular elements
359621, 359626, G02B 2710
Patent
active
056508760
DESCRIPTION:
BRIEF SUMMARY
This invention relates to lens systems.
For 3-D integral imaging, in order to capture parallax information, a large aperture objective is called for. Such, however, is difficult to implement, especially if it is to be well corrected, for example for photographic use.
The present invention provides lens systems that do not require a large aperture monolithic objective.
The invention comprises a lens system comprising an input lens array, an optical transmission microlens screen and an output lens array, in which the lenses of the input array correspond to the lenses of the output array, and the input array lenses have focal lengths greater than those of the output array lenses.
The larger aperture of a monolithic objective is in this way synthesised from a plurality of smaller lenses.
The input and output lens arrays may be equidistant from the microlens screen.
The microlens screen may comprise an auto-collimating screen. The apertures of the corresponding lenses of the input and output lens array may be equal. The system may have a main axis, and each lens of the output lens array may have an output lens principal axis, and each lens of the input lens array have an input lens principal axis and the principal axis of each lens of the output lens array is displaced from the principal axis of the corresponding lens in the input lens array towards the said main axis by an amount which is proportional to the distance of the said corresponding lenses of the input and output lens arrays from the main axis of the system.
An optical instrument including such a lens system may define an image region between a back focal distance (from the output array) for a near object point (BFD.sub.n) and a back focal distance for an object plane at infinity (BFD.sub..infin.), in which: main axis of the system is given by ##EQU1##
Having chosen this point of superposition for the rear point in the image, the distance BFD.sub..infin. to the point of superposition for a point at infinity is given by ##EQU2## where f.sub.1 is the focal length of the input lenses, and the focal length f.sub.2 of the lenses of the output lens array is given by ##EQU3## where V is the array to screen distance.
In another embodiment, the microlens screen may comprise a double integral microlens array comprising arrays of different pitch producing a long integral focusing effect, and the system may then be so arranged that the microlens array forms a reduced image of the apertures of the input lens array on to the equally reduced apertures of the output lens array whereby to produce a scaled aerial pseudoscopic image.
The lenses of the arrays may be square, hexagonal or circular.
Embodiments of lens systems and optical instruments including them will now be described with reference to the accompanying drawings, in which:
FIG. 1 is a diagrammatic axial section through one embodiment;
FIG. 2 is a ray diagram for the system of FIG. 1;
FIG. 3 is a face-on view of the output lens array of the system of FIG. 1;
FIG. 4 is a face-on view like FIG. 3 of another embodiment of output lens array;
FIG. 5 is a view like FIG. 4 of yet another embodiment of output lens array;
FIG. 6 is a diagrammatic axial section through another embodiment;
and FIG. 7 is a face-on view of the input lens array of the embodiment of FIG. 6.
The drawings illustrate lens systems comprising an input lens array 11, an optical transmission microlens screen 12 and an output lens array 13, in which the lenses 11a of the input array 11 correspond to the lenses 13a of the output array 13.
In each embodiment, the input and output lens arrays 11,13 are equidistant from the microlens screen 12 and the input array lenses 11a have focal lengths greater than those of the output array lenses 13a.
The microlens screen 12 of the embodiments illustrated in FIGS. 1 to 5 comprises an auto-collimating screen or double integral microlens array, which is to say an afocal arrangement in which the microlenses on each side are aligned, as seen in the enlarged details in FIG. 1. The left-hand detail shows, enlarged
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Davies Neil
McCormick Malcolm
De Montfort University
Epps Georgia Y.
Mack Ricky
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