JPS5816168B2 - Telephoto lens with high magnification viewfinder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention attaches a high-magnification finder to a telephoto lens for photographing, and simultaneously moves the front lens group of the telephoto lens and the objective lens of the finder by the same amount to observe and photograph a subject. Regarding the telephoto lens for photography.

Conventionally, telephoto lenses for camera photography have been designed to have a relatively small F-number in order to reduce weight, so the viewfinder field of the camera becomes darker, making it difficult to observe the subject.

In addition to this, if the aperture of the lens is made smaller when shooting, it becomes increasingly difficult to observe the subject.

To solve this problem, an automatic aperture mechanism is provided that is built into the photographic lens and automatically operates the aperture in conjunction with the opening and closing of the shutter, but this mechanism has a complicated structure and sometimes breaks down. There are drawbacks such as.

The present invention solves the above-mentioned drawbacks by providing a photographing telephoto lens with a bright, high-magnification finder, without using a complicated device such as an automatic aperture mechanism.

Generally, to depict distant objects in detail, the focal length is 3.
A telephoto lens with a rating of 0.00 or higher is considered appropriate.

If a telephoto lens is constructed compactly by reducing the telephoto ratio, it will consist of a positive front group lens and a negative rear group lens, and the focal length of the front group lens will be set to the focal length of the rear group lens. It is normal to make it smaller.

Focus adjustment for the subject is determined by the movement of the front lens group.

Therefore, a positive lens with the same focal length as the front group lens is used as the finder objective lens, and the front group lens of the telephoto lens and the finder objective lens are moved in conjunction with each other according to the distance of the subject. If you do this, the image on the finder frame will be obtained as the image on the camera side.

In this case, since the image on the camera side is viewed as a field image on the finder side, it is necessary to match the angle of view of the objective lens of the finder with the angle of view of the telephoto lens for photographing.

Further, since the image on the finder frame is formed small, by enlarging it with the eyepiece of the finder, it is possible to observe a visual field image that is the same as or more enlarged than the photographic screen.

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

1 is a telephoto lens used for single-lens reflex cameras or rangefinder-linked cameras with interchangeable lenses; positive lens 2 in the front group;
and a negative lens 3 in the rear group.

Now, if the combined focal length of the telephoto lens 1 is set to 300 mm, the optimal focal length of the front lens group 2 is 1.50 mm, which is the optical design of the photographic lens and finder system. − It is determined from

The focal length of the rear lens group 3 is the distance between both lenses of 9Q.
If it is expressed as mm, it is calculated as 480 mm.

The front group lens 2 is attached to a movable lens barrel 4 as shown in FIG. 1, the rear group lens 3 is attached to a fixed lens barrel 5 that is detachably attached to a lens mount 6 of the camera, It is inserted into the lens barrel 5 as shown in the figure, and moved straight back and forth through a guide groove 7 provided on the lens barrel 5 by means of a guide pin 8 screwed into the lens barrel 4.

Reference numeral 9 denotes an objective lens of the finder 10, which has the same focal length as the front group lens 2 of the telephoto lens 1 for photographing, and focuses a distant object erectly on the finder frame 12 via the erecting prism 11. Stand up to the statue.

The objective lens 9 is a movable lens barrel 13 of the finder 10.
The movable lens barrel 13 and the movable lens barrel 4 are integrally constructed at a connecting portion 14 so as to be attached to the lens as shown in the figure, and move in conjunction with the front group lens 2.

Reference numeral 15 denotes a fixed lens barrel of the finder 10, and the movable lens barrel 13 is fitted into the lens barrel 15 provided on the light entrance side to guide it.

The fixed lens barrel 15 is integrated with the fixed lens barrel 5 at a connecting portion 16 in order to attach the finder 10 to the photographic lens 1.

Further, a lens barrel 15 is provided on the light output side of the fixed lens barrel 5 of the finder, and an eyepiece 17 is attached to this 5 to magnify the image on the finder frame 12.

Now, the telephoto lens 1 having the above configuration is mounted on the lens mount 6 of the camera and securely fixed with the screws 18.

The installed state is shown in FIG. 2 as a front view, and FIG. 3 as a two-side view.

A distant object is observed through the finder 10, and the movable lens barrel 13 is moved straight back and forth to display the finder frame 1.
The image is focused on the visual field frame No. 2 and observed under magnification through the eyepiece lens 17 of the finder.

The magnification is the same as or greater than that of the photographic telephoto lens 1, for example, about 8 times, for easy viewing.

At this time, as mentioned above, the angle of view (θ) of the objective lens 9 is set to be the same as the angle of view (θ) of the telephoto lens 1, so as shown in FIG. If the length is 43.3 mm, the focal length of the objective lens 9 of the finder is half, so it will cover 2], 65 mm, which is half the diagonal length.

Therefore, in order to image a distant object on the frame 12 using the objective lens 9 of the finder, the movable lens barrel 13 of the finder
When the camera moves straight forward and backward, the movable lens barrel 4 of the photographic telephoto lens 1, which is integrated with it, also moves straight forward and backward in the guide groove γ by the guide pin 8. The image is formed on a Leica-sized screen.

Therefore, by pressing the shirt button while observing the image in the finder frame 12, photographing is completed.

As detailed above, in the telephoto lens with a high magnification finder according to the present invention, a distant object is observed through the finder, its image is formed on the finder frame-L, and the image is magnified. Therefore, since the image is observed as an aerial image within the frame and at a high magnification, it is possible to clearly grasp the details of the subject regardless of the calibration value of the photographic lens.

When the objective lens is moved straight forward after 111J in order to form an image of a distant object on the frame of the finder, the front lens group of the telephoto lens also moves, so that the image of the object is focused on the camera's film plane. can be calculated correctly.

Therefore, the above-mentioned telephoto lens with a finder is extremely effective when used with a camera that does not have an aperture/I mechanism, and can be widely used for police and surveying purposes.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of a telephoto lens with a high magnification finder according to the present invention, Fig. 2 is a top view of the first part, Fig. 3 is a top view thereof, and Fig. 4 is an image of the telephoto lens and finder objective lens. FIG. 3 is an explanatory diagram showing the angle and the size of the field of view. 1... Telephoto lens for photography, 2, 3...
Front group and rear group lenses, 4... movable telephoto lens barrel, 5... fixed barrel, 6...
Lens mount, 7... Guide groove, 8...
・Guide screw pin, 9...Objective lens of finder, 10...Par finder, 12...Finder frame, 13...Moveable lens barrel of finder, 14 , 16... Connection part, 15...
・Finder (7) Fixed lens barrel, 17...Finder eyepiece.

Claims (1)

[Claims] 1. In a telephoto lens in which a positive front group lens is attached to a movable lens barrel and a negative rear group lens is attached to a fixed lens barrel, a movable lens barrel of a finder configured integrally with the movable lens barrel is equipped with a lens that is the same as the front group lens. A positive objective lens having a focal length and the same angle of view as the telephoto lens is attached, and an eyepiece is attached to the fixed barrel of the finder, which is integrated with the fixed barrel, and both movable barrels are attached. A telescope lens with a high magnification finder, which is fitted into both fixed lens barrels and moves in a straight line in conjunction with each other.