JPH0422334Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a screen size regulating device for a camera having a zoom lens.

"Prior art and its problems" Camera screen size (exposure area on film) is regulated by JIS, and for full size 35mm film, the height is 24.8mm to 24.0mm.
mm, and the width is 36.8mm to 36.0mm. In all conventional cameras, this screen size is regulated by a fixed aperture;
Even in cameras equipped with zoom lenses, this fixed aperture did not cause any particular problems. This means that even when the exit pupil is closest to the screen,
This is also because the zoom lens system is designed so that it does not affect the screen size.

However, in the zoom lens currently being developed by the applicant, the position of the exit pupil is very close to the film surface at one focal length end, causing the light rays to wrap around the aperture to the outside, resulting in a decrease in the screen size. It was found that there are cases where the value is larger than the JIS standard. The aperture is regulated at the top and bottom by inner rails that contact the film, and at the left and right by the aperture opening on the aperture forming surface that creates a distance between it and the film, so the screen size expands in the horizontal direction. occurs in

FIG. 4 shows the area around the aperture opening in a cross section parallel to the film traveling direction, and the aperture opening R is the aperture forming member (camera body) P
It is worn on. The rear surface of the aperture forming member P forms a film facing surface Q extending left and right from the rear end of the aperture opening R and having a constant distance from the film surface F. Therefore, the left and right sides of the screen size are regulated by the edge C where the aperture opening R and the film facing surface Q intersect. Now, in this aperture regulating device, when the exit pupil E of the lens system is at position L, the light ray that controls the screen size on the film when actually photographing is a, and the exit pupil E changes to position S. Assuming that the same ray at that time is b, when the exit pupil E is at a position S close to the film surface, the actual screen size may deviate from the JIS standard. This tendency, the backward movement of the exit pupil, is due to an increase in the zoom magnification of the lens system.
It is thought that the size of the screen size will increase as the lens system becomes more compact, and conventional screen size regulating devices cannot cope with this problem.

``Purpose of the invention'' This invention is based on the discovery of such problems with the aperture regulating device, and is capable of ensuring a screen size within the standard even in cameras equipped with a zoom lens system in which the exit pupil moves backwards. The purpose is to obtain equipment.

``Summary of the invention'' This invention is a camera equipped with a zoom lens whose exit pupil position changes back and forth as it zooms, and whose exposure screen size on the film changes depending on the exit pupil position. The left and right edges of the aperture opening, which define the size, in the direction perpendicular to the film traveling direction are regulated by left and right movable frames perpendicular to the film traveling direction, and these left and right movable frames are used as zoom lenses. The feature is that, in conjunction with the zooming operation, the screen is moved left and right according to the position of the exit pupil so that the screen size falls within the standard.

``Embodiments of the invention'' The invention will be described below with reference to illustrated embodiments. FIG. 1 shows the main parts of a camera equipped with a zoom lens according to the present invention, and a cam ring 1 is shown as the lens system. This cam ring 1 is rotated via a drive motor 2 and a sector gear 3 to move the front and rear lens groups in the optical axis direction according to the zooming cam grooves 4 and 5, thereby performing zooming. .

A cam surface 6 is formed on the outer periphery of the cam ring 1, and an interlocking arm 9 at the lower end of the drive arm 8 rotatably supported on the cam surface 6 by a fixed support shaft 7.
are in contact. Reference numeral 10 denotes a tension spring that urges this drive arm 8 so that its interlocking arm 9 always engages with the cam surface 6. The cam surface 6 is the cam ring 1
The thickness of the cam ring 1 changes smoothly in the radial direction, and when the cam ring 1 rotates, the drive arm 8 is
Rotates around.

In front of the running plane of the film F, there are left and right movable frames 1 perpendicular to the running direction of the film F.
1 and 12 are supported so as to be movable in the running direction of the film F. These movable frames 11 and 12 have upper and lower inner rails 13 that contact the upper and lower inner surfaces of the film F.
(FIG. 2) and constitute an aperture that determines the screen size. In other words, the upper and lower inner rails 13
determines the top and bottom of the screen size, and the movable frame 11, 1
2 determines the left and right sides of the same screen size. Reference numeral 14 designates well-known outer rails formed above and below the inner rail 13, and this outer rail 14 contacts the pressure plate 15 of the back cover to regulate its position, and is controlled by both rails (pressure plate 15 and inner rail 13). The film moves through the tunnel-shaped space formed by the process.

The movable frames 11 and 12 have interlocking plate portions 11a and 12a in the lateral direction facing each other, and racks 17 and 18 that mesh with a single interlocking gear 16 are formed on the interlocking plate portions 11a and 12a, respectively. There is.
This interlocking mechanism allows the movable frames 11 and 12 to move left and right while maintaining a symmetrical relationship around the optical axis. And movable frame 11
is implanted with a dowel 21 that engages with the interlocking recess 20 of the drive arm 8, and the drive arm 8 is connected to the support shaft 7.
When rotated around , the movable frames 11 and 12 move left and right.

The cam surface 6 of the cam ring 1 has a drive arm 8 attached to the end 6a of the cam ring 1 on the side closest to the optical axis.
When the interlocking arm 9 of the zoom lens system is in contact with the end 6b on the side where the exit pupil of the zoom lens system is located furthest forward and the distance from the optical axis is the farthest, the exit pupil of the zoom lens system It is formed so that the pupil is located at the rearmost position, that is, on the film F side.

Therefore, according to the screen size regulating device described above, when zooming is performed by rotating the cam ring 1,
The drive arm 8 rotates according to the shape of the cam surface 6,
The movable frames 11 and 12 move symmetrically laterally around the optical axis. When the exit pupil of the zoom lens system comes closest to the screen side, the drive arm 8 rotates most clockwise in FIG. Conversely, since the movable frames 11 and 12 are separated when the exit pupil is farthest from the screen side, by appropriately setting the shape of the cam surface 6, the actual screen size can always be kept within an allowable range.

FIG. 3 shows an example of the position of the exit pupil and the positions of the movable frames 11 and 12. Let S be the position of the exit pupil when the lens system is closest to the film F, L be the position of the exit pupil when it is farthest from the film F, and in each case, let cS and cL be the lines that control the actual image area. The exit pupil radius is rS, rL
Then, the real screen area obtained by cS and cL is
In order to make the exit pupil the same even if its position and diameter change, it is sufficient to move the movable frames 11 and 12 to the solid line position (when the exit pupil is at S) and the broken line position (when the exit pupil is at L). It turns out.

The above is based on the premise that the screen sizes are strictly the same, but in reality, there is a tolerance range for the screen size as described above, so the regulations on the positions of the movable frames 11 and 12 are more relaxed. It is.

In Figure 1, in order to make the explanation easier to understand,
Although the shape (unevenness) of the cam surface 6 is illustrated in an exaggerated manner, in reality, it is sufficient to form the cam surface 6 to an extent that allows the movable frames 11 and 12 to move as described above. Furthermore, many lens systems whose focal lengths are changed by rotation of the cam ring 1 are known, and since the present invention does not concern the lens systems themselves, their illustrations are omitted.

"Effects of the invention" As described above, the camera screen size regulating device of the present invention regulates the left and right screen size with the left and right movable frames that move in the film advancing direction, and the left and right movable frames are used for zooming. By moving the exit pupil of the lens left and right depending on the position of the lens, the screen size is kept within the regulations, so even in zoom lens cameras, where the exit pupil approaches the aperture and the screen size would deviate from the standard with a fixed aperture. The screen size of can be set as the standard size.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of the main parts showing an embodiment of the screen size regulating device for a camera having a zoom lens according to the present invention, Fig. 2 is a sectional view taken along the - line in Fig. 1, and Fig. 3 is a view of the exit pupil. FIG. 4 is a plan view showing the relationship between the positions of the movable frame and the position of the movable frame, and FIG. 4 is an optical path diagram for explaining problems related to the screen size. DESCRIPTION OF SYMBOLS 1... Cam ring, 4, 5... Zooming cam groove, 6... Cam surface, 7... Fixed support shaft, 8... Drive arm, 11, 12... Movable frame, 13... Inner rail, 14... ...Outer rail, 15...Pressure plate, F...
film.

Claims (1)

[Scope of Claim for Utility Model Registration] In a camera equipped with a zoom lens whose exit pupil position changes back and forth as it zooms, the size of the exposure screen on the film changes depending on the exit pupil position, The left and right edges of the aperture opening, which determines the size, in the direction perpendicular to the film traveling direction are regulated by left and right movable frames perpendicular to the film traveling direction, and these left and right movable frames are used for the zoom A screen size regulating device for a camera having a zoom lens, characterized in that the screen size regulating device for a camera having a zoom lens is moved horizontally in conjunction with a zooming operation of the lens so that the screen size falls within a standard according to the position of the exit pupil.