JPH05281591A - Diaphragm device for photographic lens - Google Patents

Abstract

PURPOSE:To prevent a ghost image based on reflection between two ND filters, from being imaged into the image plane in a photographic lens diaphragm device with the ND filters fitted individually to two diaphragm blades in such a way as to partially cover the diaphragm diameter forming cutouts. CONSTITUTION:In this photographic lens diaphragm device, ND filters 4, 10 are individually fitted to two diaphragm blades 2, 8 in such a way as to partially cover diaphragm diameter forming cutouts 3, 9. These ND filters 4, 10 are disposed being provided with an angle alpha so as not to be parallel. The ray of light 19 transmitted through the ND filter 4, reflected by the ND filter 10, further reflected by the ND filter 4 and then transmitted through the ND filter is deflected outside of the light receiving face 21 of an image pickup element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel photographic lens diaphragm device. Specifically, in a diaphragm device for a photographing lens in which at least two diaphragm blades are separately attached with ND filters so as to cover a part of the notches for forming the diaphragm diameter, a ghost caused by reflection between two ND filters. The idea is to prevent the image from appearing on the screen.

[0002]

2. Description of the Related Art CCDs in recent video cameras
Due to the extremely high sensitivity of image sensors such as image sensors,
In order to prevent the aperture from becoming an extremely small aperture when the subject is bright, at least two aperture blades each have an ND filter attached so as to cover a part of the aperture diameter forming notch, and an aperture device for a photographing lens. There is.

[0003]

However, two NDs are used.
When a filter is used, the generation of a ghost image due to the reflection between the two ND filters becomes a problem.

This will be described with reference to FIGS.

Reference numerals a1 to a6 are lenses, and b is a light receiving surface of the image pickup device. The diaphragm blades c and d are arranged between the lenses a4 and a5, and the diaphragm blades c and d are respectively arranged.
ND filters e and f are separately attached.

When the ND filters e and f are arranged in parallel with each other, two ND filters e and f are arranged.
Is directly transmitted through the lens a5 and is incident on the lens a5 as the optical axis xx, and the ray h incident on the lens a5 after being mutually reflected by the two ND filters e and f is the optical axis x-x.
Since x and the angle θ1 formed are similar (see FIG. 8),
As shown in FIG. 9, when a strong light source j is imaged in the screen i, there is a problem that an irregularly distorted ghost image k appears in the vicinity thereof.

[0007]

Therefore, in order to solve the above-mentioned problems, the diaphragm device for a taking lens of the present invention uses two N lenses.
The D filters are arranged at an angle so as not to be parallel.

[0008]

Therefore, in the diaphragm apparatus for a photographing lens of the present invention, the angle formed by the optical axis of the light beam that passes through the two ND filters and is incident on the rear lens is mutually reflected by the two ND filters. After that, the angle of the ray incident on the rear lens will be greatly different from the angle formed by the optical axis, so the ghost images based on the rays reflected mutually by the two ND filters can be diverted out of the screen. The ghost image due to the reflection between the ND filters of No. 1 does not appear on the screen.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the diaphragm device of the taking lens of the present invention will be described below with reference to the embodiments shown in the accompanying drawings.

1 to 5 show a first embodiment 1 of a diaphragm device for a taking lens according to the present invention.

A diaphragm blade 2 has a notch 3 for forming a diaphragm diameter formed at its lower edge, and an ND filter 4 is attached so as to cover the upper end of the notch 3 for forming a diaphragm diameter. Guide slits 5a and 5b extending in the vertical direction are separately formed at positions near the right edge of the diaphragm blade 2. Further, a guided slit 6 extending in the vertical direction is also formed at a position near the left edge.

Further, a long elongated connection hole 7 is formed at the right and left of the guided slit 5a formed on the right side of the diaphragm blade 2.

The guide pins provided on the housing (not shown) having the light passage holes are guided slits 5a, 5b.
And 6 are slidably engaged with each other, whereby the diaphragm blades 2 are slidably supported in the housing in the vertical direction.

Reference numeral 8 is also a diaphragm blade, and a notch 9 for forming a diaphragm diameter is formed on an upper edge thereof, and an ND filter 10 is attached so as to cover a lower end portion of the notch 9 for forming a diaphragm diameter. Guide slits 11a and 11b that extend in the up-down direction are separately formed at positions near the left edge of the diaphragm blade 8. Further, a guided slit 12 extending vertically is also formed at a position near the right edge.

Further, a long elongated connection hole 13 is formed in the left and right at a position just above the guided slit 11a formed on the left side of the diaphragm blade 8.

A guide pin provided on the casing (not shown) is slidably engaged with each of the guided slits 11a, 11b and 12 so that the diaphragm blade 8 slides vertically on the casing. It is movably supported.

Reference numeral 14 is a drive motor, which is attached to the upper portion of the casing (not shown). Reference numeral 15 is an operation arm that is long in the substantially left-right direction, the central portion of which is fixed to the rotary shaft 14a of the drive motor 14, and connecting pins 16a and 16b are provided at both left and right ends thereof so as to project therefrom.

The connecting pin 16a on the right side of the operating arm 15 is slidably engaged with the connecting elongated hole 7 of the diaphragm blade 2, and the connecting pin 16b on the left side is slidably engaged with the connecting elongated hole 13 of the diaphragm blade 8. To be done.

Therefore, when the drive motor 14 is driven and the operation arm 15 is rotated, the connecting pins 16a and 16b thereof are connected.
, And the diaphragm blades 2 and 8 connected thereto move in the vertical direction and in the opposite direction. As a result, the aperture diameter limited by the aperture diameter forming notches 3 and 9 of the two aperture blades 2 and 8 changes.

The ND filter 10 has a lens optical axis x
The ND filter 4 arranged in a posture substantially perpendicular to -x and located on the front side of the ND filter 10 is the ND filter 1.
It is arranged in a state of being inclined at an angle α with respect to 0.

Therefore, the light beam 18 passing through the two ND filters 4 and 10 as they are and incident on the rear lens 17 makes an angle θa with respect to the optical axis xx and the ND filter 4 after passing through the ND filter 4. Reflected on the front of 10 and further ND
An angle difference (2α) occurs between an angle θb (= θa + 2α) formed by the light ray 19 which is reflected by the rear surface of the filter 4 and then passes through the ND filter 10 and enters the lens 17 with respect to the optical axis xx. Therefore, the light ray 19 forming the ghost image is diverted to the outside of the screen. That is, the actual image 20 formed by the light ray 18 is incident on the light receiving surface 21 of the image pickup element, but the ghost image 22 formed by the light ray 19 is deviated from the light receiving surface 21.

The ND filter 1 of the ND filter 4
The inclination angle α with respect to 0 is preferably in the range of 0.5 degrees to 15 degrees.

This will be described with reference to FIG.

In FIG. 5, reference numeral 23 denotes an optical system behind the diaphragm device 1, and 24 denotes a light receiving surface of the image pickup device.

When a bright image such as a ghost image, for example, a light source image 25 is formed at a position of a distance Y from the center of the light receiving surface 24, the light ray 26 incident on the principal point H on the front side of the optical system 23 is When the angle formed with respect to the optical axis xx is θa, the focal length of the optical system 23 is f, and the lateral magnification of the optical system 23 is m, the relationship of “Y = f (1-m) tan θa” is established.

In a lens used for a video camera, empirically, m is in the range of "-1 <m <0", and f is "2.5" with respect to the short side dimension V of the light receiving surface 24. <F <7
V ”range.

Therefore, for example, the image 25 of the light source shows the light receiving surface 2
In order to make the ghost image 27 go out of the light receiving surface 24 when it is below the position of “V / 4” with respect to the vertical center of 4, the light beam 26 from the light source is directed to the front side of the optical system 23. The inclination angle θa incident on the point H is calculated from “Y = V / 4” by

[0028]

[Equation 1]

Then, θb in FIG. 3 is changed to “θb> 2 · θa”.
In order to be satisfied, it is necessary that “α> 0.5 °”.

When "α> 15 °", the diaphragm device 1
The ND filter 4 or 10 (N
(If the D filter 10 is tilted) will collide, and if it is attempted to avoid this, there is a problem that downsizing becomes difficult.

FIG. 6 shows another embodiment 1A of the diaphragm device for a photographing lens of the present invention.

Reference numeral 28 denotes a diaphragm blade, and a notch 29 for forming a diaphragm diameter is formed at a lower edge of the diaphragm blade, and an ND filter 30 is attached so as to cover an upper end portion of the notch 29 for forming a diaphragm diameter.

A connecting hole 31 extending substantially vertically is formed at the right end of the diaphragm blade 28, and a supported hole 32 is formed above the connecting hole 31.

Reference numeral 33 denotes another diaphragm blade, and a notch 34 for forming a diaphragm diameter is formed at the upper edge of the blade, and the ND filter 3 is provided.
5 is attached so as to cover the lower end portion of the notch 34 for forming the aperture diameter.

A connecting hole 36 extending substantially vertically is formed at the right end of the diaphragm blade 33, and a supported hole 37 is formed below the connecting hole 36.

Then, two support pins, which are vertically protruded from a casing (not shown) having a light passage hole, are inserted into the supported holes 32 and 37 of the diaphragm blades 28 and 33, respectively. As a result, the diaphragm blades 28 and 33 are rotatably supported by the housing.

Reference numeral 38 denotes a drive motor supported on the right end portion of the casing (not shown), and the base end portion of the operation arm 39 is fixed to the rotation shaft 38a thereof. A connecting pin 39a is projectingly provided on the rotating end of the operation arm 39, and the connecting pin 39a is slidably engaged with the connecting holes 31 and 36 of the diaphragm blades 28 and 33.

When the drive motor 38 is driven, the operating arm 39 rotates and its connecting pin 39a moves substantially left and right, so that the diaphragm blades 28 and 33 are inserted with supporting pins (not shown). Supported holes 32, 37
Is rotated about. Then, the diaphragm blades 28, 33
Since the rotation fulcrums 32 and 37 are located on the opposite sides of the connecting pin 39a, the diaphragm blades 28 and 33 rotate in the opposite directions.

In the diaphragm device 1A as well,
By providing a predetermined inclination angle between the ND filters 30 and 35, the same effect as in the above-described first embodiment can be obtained.

[0040]

As is apparent from the above description, in the diaphragm apparatus of the photographing lens of the present invention, at least two diaphragm blades are provided with ND filters separately so as to cover a part of the notch for forming the diaphragm diameter. A diaphragm device for an attached photographing lens, characterized in that these two ND filters are arranged at an angle so as not to be parallel to each other.

Therefore, in the diaphragm device of the photographing lens of the present invention, the angle formed by the optical axis of the light beam that passes through the two ND filters and enters the rear lens is mutually reflected by the two ND filters. After that, the angle that the light ray that enters the rear lens makes with the optical axis will differ greatly,
The ghost image based on the light rays mutually reflected by the two ND filters can be diverted to the outside of the screen, and the ghost image based on the reflection between the two ND filters does not appear on the screen.

The specific shapes and structures shown in each of the above-mentioned embodiments are merely examples for embodying the present invention, and the technical scope of the present invention is limited by these. Not interpreted.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a first embodiment of a diaphragm device for a photographing lens of the present invention.

FIG. 2 is an explanatory diagram showing an outline of an optical system.

FIG. 3 is an enlarged view showing a main part of FIG.

FIG. 4 is an enlarged view showing a light receiving surface of an image pickup device.

5A and 5B are diagrams for explaining the operation, wherein FIG. 5A is a schematic diagram cut along an optical axis, and FIG. 5B is a diagram schematically showing a light receiving surface of an image sensor.

FIG. 6 is an exploded perspective view showing a second embodiment of the diaphragm device of the taking lens of the present invention.

FIG. 7 is a diagram of an optical system showing a conventional problem.

FIG. 8 is an enlarged view showing a main part of FIG.

FIG. 9 is a screen view showing a conventional problem.

[Explanation of symbols]

 1 Photography Lens Aperture Device 2 Aperture Blade 3 Aperture Diameter Forming Notch 4 ND Filter 8 Aperture Blade 9 Aperture Diameter Forming Notch 10 ND Filter 1A Photographic Lens Aperture Device 28 Aperture Blade 29 Aperture Diameter Forming Notch 30 ND Filter 33 Aperture Blade 34 Notch for forming aperture diameter 35 ND filter

Claims (1)

[Claims] 1. A diaphragm apparatus for a photographing lens, wherein at least two diaphragm blades are separately attached with ND filters so as to cover a part of the notches for forming the diaphragm diameter.
A diaphragm device for a photographing lens, wherein the D filters are arranged at an angle so as not to be parallel.