OPTICAL DEVICE

Abstract

This invention prevents a degradation in image quality resulting from undesirable reflected light and undesirable transmitted light generated near the ridgeline of the edge portion of an optical element including an aperture blade or an ND filter. The aperture edge of the aperture blade cooperates with the aperture edge of another aperture blade to form an almost rhombic aperture. A small saw-toothed and non-periodic uneven portions having various sizes are formed along two, front and rear ridgelines of the aperture edge and along those of the ND filter. When incident light beams strike the aperture edge of the aperture blade or the edge of ND filter, the uneven portions formed at the ridgeline reflect them in various directions.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing the arrangement of a photographing apparatus;

FIG. 2 is a perspective view of an aperture blade according to the first embodiment;

FIG. 3 is a partial enlarged perspective view of the aperture blade;

FIG. 4 is a view for explaining the operation of the aperture blade;

FIG. 5 is a partial enlarged perspective view of an ND filter according to the second embodiment;

FIG. 6 is a partial enlarged perspective view of another ND filter;

FIGS. 7A to 7C are views for explaining a state wherein the ND filter moves with respect to an aperture;

FIG. 8 is a view for explaining the operation of the ND filter;

FIG. 9 is a partial enlarged perspective view of an ND filter according to the third embodiment;

FIG. 10 is a partial enlarged perspective view of a modification of an ND filter;

FIG. 11 is a view showing the arrangement of an aperture device according to the fourth embodiment;

FIGS. 12A to 12C are views showing states wherein aperture blades move with respect to a pupil diameter;

FIGS. 13A and 13B are partial enlarged perspective views of an ND filter according to the fourth embodiment;

FIG. 14 is a view for explaining the operation of an ND filter according to the fifth embodiment;

FIGS. 15A and 15B are views showing the arrangement of cutting blades, respectively, for forming uneven portions;

FIG. 16 is a view for explaining the operation of a conventional aperture blade;

FIG. 17 is a view for explaining the operation of a conventional ND filter;

FIG. 18 is a view for explaining the operation of another conventional ND filter; and

FIGS. 19A to 19C are perspective views of still another conventional ND filters, respectively.

Claims

1. An optical device employed in a photographing optical system which forms an object image on an image sensor, comprising one optical element or plural optical elements, wherein at least one optical element includes an edge portion that forms an aperture or an edge portion that is positioned in said aperture, and non-periodic uneven portions are formed at least along a ridgeline of said edge portion.

2. The optical device according to claim 1, wherein said uneven portions have saw-toothed shape with various sizes.

3. The optical device according to claim 1, wherein an end face of said edge portion of said optical element has a groove with non-periodic shape, and said groove is directed in a direction different from that of said ridgeline.

4. The optical device according to claim 1, wherein an end face of said edge portion of said optical element has a groove with non-periodic shape, and said groove is directed in the same direction as that of said ridgeline.

5. The optical device according to claim 3, wherein said non-periodic shape include saw-toothed shape with various sizes.

6. The optical device according to claim 1, wherein said optical element comprises a plurality of aperture blades, and said aperture blades operate to form said aperture with said edge portion.

7. The optical device according to claim 1, wherein said optical element comprises an optical filter, and said edge portion of said optical filter is positioned in said aperture.

8. The optical device according to claim 1, wherein said optical elements comprise both an optical filter and an aperture blade which forms said aperture with said edge portion, and said edge portion of said optical filter is positioned in said aperture.

9. The optical device according to claim 8, wherein one among said aperture blade and said optical filter is moved independently of the other one of among them.

10. The optical device according to claim 8, wherein said optical filter is moved together with said aperture blade.

11. The optical device according to claim 7, wherein said optical filter comprises an ND filter obtained by forming a light attenuation thin film on at least one surface of a transparent plastic film.

12. The optical device according to claim 7, wherein said optical filter comprises a gradation ND filter in which the farther a light transmitting position is away from said edge portion, the lower a light transmittance at that position of said gradation ND filter becomes continuously.