1. Field of the Invention
The present invention relates to an optical element and a picture taking system including the optical element that is particularly suitable for a video camera, a still video camera, and a copying machine.
2. Description of the Related Art
FIG. 10 schematically illustrates a main part of an optical system disclosed in Japanese Patent Laid-Open No. 8-292371.
Referring to FIG. 10, there is provided an optical element 10 including a transparent body formed of glass or plastic, having a plurality of curved reflecting surfaces provided on the surface thereof.
On the surface of the optical element 10, there are formed, in the order of passage of light from an object, a concave refracting surface (incident surface) R2 having a negative refractive power, four reflecting surfaces of concave mirror R3, reflecting mirrors R4 and R5, a concave mirror R6, and a convex refracting surface (emergent surface) R7 having a positive refractive power. In FIG. 10, there are shown a diaphragm (entrance pupil) R1 disposed on the object side of the optical element 10, an optical correcting plate 3, such as a quartz low-pass filter, an infrared filter, or the like, a final image forming surface R10 on which an image pick-up surface (light receiving surface) of an image pick-up element (image pick-up medium) such as a CCD is located, and a reference axis 5 of the optical system.
Both the refracting surfaces R2 and R7 are rotary symmetrical spherical surfaces, and all the reflecting surfaces R3 to R6 are aspheric surfaces symmetrical with respect to only a YZ plane.
An image forming operation of the optical element 10 will now be described. Of the light flux 1 from an object, the amount of incident light is regulated by the diaphragm R1, and then enters the incident surface R2 of the optical element 10, is reflected by the surfaces R3 and R4, temporarily forms an image near the surface R4, is reflected from the surfaces R5 and R6, and is emitted from the emergent surface R7 to form an image again on the final image forming surface R10 via the optical correcting plate 3. As described above, the light from the object temporarily forms an image near the surface R4, while the light of the entrance pupil R1 temporarily forms an image between the surfaces R5 and R6.
The direction of the reference axis entering the optical element 10 and that emitting therefrom are parallel to and the same as each other. In addition, all of the reference axes including the incident reference axis and emergent reference axis are given in FIG. 10 (on the YZ plane).
The optical element 10 serves as a lens unit having a desired optical performance and a positive refractive power overall by virtue of the refractive power (xcfx86=1/f; xcfx86: power, f: focal length) of the incident and emergent surfaces R2 and R7, and the refractive powers of the concave reflecting mirrors R3 and R6.
In addition, the optical element 10 collects light fluxes from the object existing in one direction (left side on the plane of the drawing), and forms the image thereof on the final image forming surface R10.
It is convenient that pictures of an object located in another direction, for example, in a direction perpendicular to the plane of the drawing (the X direction) can be taken as in the state of FIG. 10 without rotating the optical element 10 around an axis of rotation in the Y direction.
In addition, it is also convenient that pictures of objects located in the same direction can be easily taken by substantially one optical element with different magnification.
It is an object of the present invention to provide a convenient optical element and a picture taking system having the convenient optical element.
According to an aspect of the present invention, there is provided an optical element including a plurality of curved reflecting portions, the reflecting portions reflecting light entered into the optical element, thereby transmitting the light inside the optical element, wherein the reflecting portions include a plurality of reflecting portion groups, and the reflecting portion groups form optical paths that are different from each other.
According to another aspect of the present invention, there is provided an optical element including a plurality of curved reflecting portions, the reflecting portions reflecting light entered into the optical element from a light incident portion, thereby transmitting the light inside the optical element, wherein the reflecting portions include a plurality of reflecting portion groups, and the reflecting portion groups have different optical characteristics.
In each of the above optical elements, the reflecting portions may be provided on 2n(n=integers of 2 or more) side surfaces (inner surfaces when body is hollow) of at least one of a solid body and a hollow body having the shape of a 2n-sided prism (n=integers of 2 or more), respectively, and the reflecting portion groups may be constructed by the reflecting portions provided on each pair of opposite side surfaces (inner surfaces when the body is hollow).
In addition, in each of the above optical elements, each of the reflecting portion groups may include a light incident portion and a light emergent portion; the reflecting portion groups may include a common reflecting portion and light incident portion, and the common reflecting portion and light incident portion may be rotatable together; and the reflecting portion groups may include a common final reflecting portion and light emergent portion, and the common final reflecting portion and light emergent portion may be rotatable together.
Furthermore, in each of the above optical elements, at least one of the light incident portion and the light emergent portion may include a curved surface that forms a spherical lens or an aspheric lens.
Still furthermore, in each of the above optical elements, each of the reflecting portions may include a rotary asymmetrical aspheric reflecting surface.
According to the present invention, there is provided a picture taking optical system including any one of the above optical elements, and a picture taking apparatus including the picture taking optical system and at least one of an image pick-up element and an image pick-up medium.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.