JPS6321630A - Diaphragm device for camera - Google Patents

Abstract

PURPOSE:To eliminate the generation of ghost and flare by varying the light transmissivity of filter which is so arranged as to cover an aperture part associatively with the opening/closing operation of the aperture part. CONSTITUTION:The filter 12 varies continuously in light transmissivity about a shaft 8 and is arranged rotatably in front of or behind a diaphragm device so that the aperture part 7 is covered successively with a part which is different in light transmissivity according to the angle of rotation. A motor 9 is driven associatively with the rotation of a diaphragm blade 6 to rotate the filter 12 counterclockwise when driven in such a direction that the blade 6 reduces the aperture part 7. Namely, when the aperture part 7 is reduced in size associatively with the diaphragm operation of the diaphragm device, a filter part 12 having lower light transmissivity is positioned at the aperture part 7.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to an aperture device for a video camera, etc.
In particular, it relates to improvements in preventing hunting in automatic diaphragms.

2. Description of the Related Art Conventionally, hunting has occurred in automatic aperture devices for video cameras, and the amount of light passing through the aperture of the aperture device has periodically changed. The rate of change in the amount of light due to this hunting becomes larger when the aperture is made sufficiently small (when the diameter of the aperture is made small). In order to reduce the degree of light intensity change due to hunting with the ND
A filter device is used.

In the conventional ND filter device, as shown in Fig. 2, a light-shielding small piece 3 is fixed to the tip of one of a plurality of aperture blades 2 that change the size of the aperture 1 depending on the rotation angle. It is configured such that the small piece 3 is always located within the opening 1.

That is, by positioning the light-shielding small piece 3 within the opening 1, part of the light passing through the opening 1 is blocked,
This is intended to reduce the effect of hunting by reducing the actual size of the aperture 1 and increasing the diameter of the aperture 1 required to obtain the same amount of light.

Problems to be Solved by the Invention However, with such a structure, as the aperture is opened, the number of small pieces 3 constituting the ND filter device decreases.
On the contrary, it was a direct cause of ghost flares. This is due to the following reasons.

In other words, when opening the diaphragm, the small piece 3 that makes up the ND filter device moves in the radial direction around the optical axis in a plane perpendicular to the optical axis together with the diaphragm blades. Some of the blocked light rays are reflected by the small piece 3, and the reflected light repeatedly refracts and reflects on the lens surface and finally reaches the imaging surface, causing ghost flare. It has been occurring. The present invention
By preventing the small piece 3 constituting the filter device from blocking a portion of such an optical path, ghost flare, which is a direct cause of ghost flare, can be prevented from occurring.

Means for Solving the Problems The camera aperture device of the present invention solves the above problems, and in conjunction with the opening/closing operation of the aperture of the aperture device main body, the light transmission of a filter arranged to cover the aperture is controlled. It is configured to change the rate.

Function According to the above-described configuration, when the aperture is narrowed down, as the diameter of the aperture aperture approaches zero, the portion of the filter with low light transmittance gradually covers the aperture, and the actual aperture becomes smaller. This works to reduce the diameter, and there is no need to make the diameter of the opening sufficiently small, and as a result, the adverse effects of hunting are reduced, as in the conventional configuration.

In the conventional configuration, a small light-blocking piece is always located within the opening, but in the present invention, the light transmittance of the filter that covers the opening is changed, so ghosts due to reflection by the small light-blocking piece are removed. and flares are to be reduced and eliminated.

Embodiment FIG. 1 is a front view of main parts showing a set of embodiments according to the present invention. In FIG. 1, reference numeral 6 denotes a conventionally known aperture device comprising a plurality of aperture blades 6, and is configured such that the diameter of an opening 7 changes depending on the rotation angle of the aperture blades 6. 12
is a filter configured such that its light transmittance varies steplessly along the circumferential direction, and the portions having different light transmittances depending on the rotation angle sequentially cover the opening 7. It is arranged in front or behind the throttle device so as to be rotatable about a shaft 8.

Reference numeral 9 denotes a motor that rotates the filter 12, and its drive gear 10 is engaged with a gear 11 fixed to the shaft 8 of the filter 12.

Further, the motor 9 is driven in conjunction with the rotation of the aperture blade 6, and when the aperture blade 6 is driven in a direction to make the aperture 7 smaller, it rotates the filter 12 counterclockwise. , the part of the filter with lower light transmittance is the opening 7
It is configured to be located in front of the That is, when the aperture 7 becomes smaller in conjunction with the aperture operation of the aperture device,
A portion of the filter with lower light transmittance is located in the opening.

Effects of the Invention As described above, according to the present invention, a light-shielding small piece is not always located at the aperture of the diaphragm device, so ghosts and flares caused by light reflected from this small piece are eliminated.

[Brief explanation of the drawing]

Fig. 1 is a front view of the main part of the aperture device of the camera of the present invention, Fig.
The figure is a front view of main parts of a conventional camera aperture device. 6... Aperture device, 6... Aperture blade, 7
...Opening, 8...Axis, 9...
・Motor, 12...Filter port

Claims (1)

[Claims] A camera aperture device characterized in that the light transmittance of a filter arranged to cover the aperture is changed in conjunction with the opening/closing operation of an aperture of the aperture device main body.