JPS63144319A - Optical system with deformed stop and mold lens - Google Patents

Abstract

PURPOSE:To remove the adverse optical influence of the gate of a mold lens by arranging the gate of the mold lens in a direction where passing luminous flux is narrow in width. CONSTITUTION:Respective plastic lenses L2-L4 have parts for injecting resin materials into metallic molds in a molding process, i.e. gates G2-G4 on the lens outer peripheral surfaces, and the gates are arranged overlapping with one another in the optical axis direction of the lens system. A deformed stop S is formed by supporting a couple of shutter plates S1 and S2 pivotally by a hinge H, its opening shape is nearly diamond, and the flatness of the diamond shape increases nearby the intermediate stop diameter part between an open aperture part and a minimum aperture diameter part. This optical system is assembled so that the short diagonal of the diamond shape is directed to the gates of the plastic lenses. Consequently, an area where a defect is easily generated from nearby the gate of a mold lens to the optical axis is outside the effective optical path, and the performance of the whole lens system is prevented from decreasing.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical system having a irregularly shaped diaphragm and a molded lens, and is used, for example, as a photographing optical system of a lens shutter camera.

(Prior Art) Conventionally, in a photographing optical system for a camera that has a circular aperture and a fillo surface, that is, a rectangular convergence effective surface, a circular light beam passing through the circular aperture is directed from the imaging effective surface. Taking into account the fact that a portion of the light beam protrudes from the lens, it has been proposed to place a gate of the molded lens at a position through which the light beams that protrude from the effective imaging surface pass, thereby preventing the negative optical effects of the gate (Utility Model Application No. 59 (Refer to Publication No.-164014).

(Problem to be solved by the invention) In a molded lens such as a plastic lens, there is a part where the mold material is poured into the mold, a so-called gate, on the outer periphery of the lens, and internal distortion occurs from the vicinity of this gate to the optical axis. There is a possibility of occurrence of double refraction and birefringence, and light passing through this region is considered to have large aberrations. 1. On the other hand, the aperture shape of a shutter that also serves as an aperture in a lens-shutter camera is often not substantially circular but rectangular when stopped down. Furthermore, there are many rectangular receiver shapes with different diagonal lengths, such that the transmitted light beam is narrow in the direction of the short diagonal length, and the transmitted light beam is wide in the direction of the long diagonal length.

Therefore, it is considered possible to prevent the performance of the photographing optical system from deteriorating by arranging the gate of the plastic lens in a narrow direction in the transmitted light beam by utilizing the aperture shape of an irregularly shaped aperture such as a shutter that also serves as an aperture.

The present invention has been made based on such knowledge, and its purpose is to provide an irregularly shaped diaphragm and a mold that can eliminate the adverse optical effects caused by the gate of a molded lens by utilizing the shape of the irregularly shaped diaphragm. An object of the present invention is to provide an optical system having a lens.

(Means for Solving the Problems) An optical system having an irregularly shaped diaphragm and a molded lens according to the present invention is an optical system including an irregularly shaped diaphragm through which a light beam passing through is different from a circular shape, and a molded lens having a gate. The gate of the molded lens is arranged in a direction in which the width of the light beam passing through the irregularly shaped diaphragm is narrow.

(Function) As mentioned above, in the present invention, since the light flux passing through the irregularly shaped diaphragm is different from the circular shape, the light flux passing through this irregularly shaped diaphragm has a wide direction and a narrow direction in the light flux. There is a possibility that internal distortion or birefringence may occur in a molded lens from the vicinity of the gate to the optical axis, but in the present invention, the gate of the molded lens is placed in the direction in which the width of the light beam passing through the irregularly shaped diaphragm is narrow. Since the area where internal distortion or birefringence may occur is outside the effective optical path,
Therefore, deterioration in the performance of the optical system can be suppressed.

(Example) Examples of the present invention will be described below.

FIG. 1 is a perspective view showing a schematic configuration of an embodiment of the present invention. This embodiment is an example in which the present invention is applied to a photographing optical system of a lens shutter camera, and as a special diaphragm (S),
It uses a shutter that also functions as an aperture. Runs (
Ll) is a glass lens, and the second lens (L2) to the fourth lens (L4) are plastic lenses. Each plastic lens has portions, so-called gates (G2) to (G4), on the outer peripheral surface of the lens, through which a resin material is poured into a mold during the molding process. Each gate (G2) ~ (G4
) are arranged so as to overlap in the optical axis direction of the lens system.

The irregular diaphragm (S) includes a pair of shutter plates (S 1 ),
(S2) is pivotally supported by a hinge (H), and by rotating each shutter plate (Sl) and (S2) in a direction away from each other, an opening through which light passes is formed. The opening is closed by rotating the shutter plate <31), (S2) in the opposite direction to the above direction. The shutter speed is determined by the time during which the aperture is formed, and the aperture value is determined by the size of the aperture. The aperture shape of the irregular diaphragm (S) is approximately rhombic, and the degree of flatness of the rhombus increases near the intermediate aperture diameter between the open aperture and the minimum aperture diameter. The shorter diagonal direction of the rhombus is the shutter A axis, the longer diagonal direction is the shutter B axis, and the plastic lenses (L2) to (L4
), the axis connecting the optical axis and the center of the gates (G2) to (G4) in The angular difference with the gate axis is set within ±20°, for example.

Fig. 2 is a sectional view of the optical system shown in Fig. 1 in the jack-A axis direction, and Fig. 3 is a sectional view of the same shutter B in the axial direction, showing the relationship between the irregular diaphragm (S) and the off-axis light beam. It shows a relationship. In the figure, (F) is the imaging plane. The width of the off-axis light beam passing through each plastic lens (L2) to (L4) is limited by the aperture width of the irregularly shaped diaphragm (S), and in the shutter B axis direction, the width of the light beam passing through it is wide, as shown in Figure 3. , the light beam passes through the peripheral parts of the lenses (L2) to (L4).

On the other hand, in the shutter A-axis direction, as shown in FIG. 2, the passing light beam is narrow, and the light beams near the optical axes of the lenses (L2) to (L4) pass through the irregularly shaped diaphragm (S). Therefore, by arranging the gates (G2) to (G4) in the direction of the narrow shutter A axis in the light beam, the gates (G2) to (G4) can be
4) can be suppressed as much as possible from adverse effects on lens performance. Furthermore, the closer the lens is to the irregularly shaped diaphragm (S), the more the light flux near the optical axis passes through the irregularly shaped diaphragm (S). therefore,
The effect of suppressing lens performance deterioration is greatest in the lens (L4), but the lens (L
Also in 2) and (L3), it is better to provide the gates (G2>, (G3) in the shutter A-axis direction than in the shutter B-axis direction to suppress deterioration in lens performance.

Note that the molded lens may be a plastic lens using a synthetic resin material, or may be one using a glass material.

(Effects of the Invention) As described above, in the present invention, since the gate of the molded lens is arranged in the direction where the width of the light beam passing through the irregularly shaped diaphragm is narrow by 3 m,
The region where defects are likely to occur from the vicinity of the gate of the molded lens to the optical axis is outside the effective optical path, and therefore has the effect of preventing performance deterioration of the lens system as a whole.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a schematic configuration of an embodiment of the present invention, FIG. 2 is a cross-sectional view along the shutter A1u11 direction of the same as above, and FIG. 3 is a cross-sectional view of the shutter B along the axial direction of the same. (L2) to (L4) are plastic lenses, (G2) to
(G4) is a gate, and (S) is an aperture.

Claims (4)

[Claims] (1) An optical system that includes an irregularly shaped aperture whose light flux passes through the irregularly shaped aperture, and a molded lens having a gate, where the gate of the molded lens is arranged in a direction in which the width of the light flux that passes through the irregularly shaped aperture is narrower. An optical system with an irregularly shaped aperture and a molded lens. (2) An optical system having an irregularly shaped diaphragm and a molded lens according to claim 1, wherein the molded lens having a gate is arranged near the irregularly shaped diaphragm. (3) A modified diaphragm according to claim 2, wherein a plurality of molded lenses having gates are provided, and the gates of each molded lens are arranged to overlap in the optical axis direction. Optical system with molded lenses. (4) An optical system having an irregularly shaped diaphragm and a molded lens according to any one of claims 1 to 3, wherein the irregularly shaped diaphragm is a shutter that also serves as a diaphragm.