JPS5957227A - Reverse-galilean finder capable of focusing - Google Patents

Abstract

PURPOSE:To execute focusing by providing a mirror for bending a luminous flux, and making a luminous flux image passing through a semi-transparent part of a luminous flux dividing device 1 conform with a luminous flux image passing through its outside. CONSTITUTION:Lenses 301, 302, 303 and 304 are a lens system to an afocal part of a zoom lens, and a luminous flux dividing device I 305 divides and reflects the greater part of an incident luminous flux at a right angle with the optical axis direction, and forms an image on a focal face 307 by a lens 306. A luminous flux which is divided and made to pass through in the optical axis direction by the luminous flux dividing device I 305 enters into a finder system. A luminous flux dividing device II 308 is used for focusing, a concave lens 309 forms an objective lens of the finder, and constitutes a reverse-Galilean finder system together with a convex lens 310 which becomes a rear eyepiece, and 312 becomes a position of the pupil. As for the lenses 301-304, the lens diameter is made large so that a luminous flux which is brighter than F- number required for photographing passes through, and passes through the transparent part of the luminous flux dividing device I 305, and the luminous flux is bent so as to fall at right angles with the optical axis by reflectors 311a, 311b, and is made to conform with an image of the luminous flux passing through the oblique line part of the luminous flux dividing device I 305, by which focusing can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inverted Galilean type finder capable of focusing a photographing device using a zoom lens as a photographing optical system.

Conventionally, a TTL finder as shown in FIG. 1 has often been used as a finder thread for a camera 2 using a zoom lens, such as an 8-Yu camera or a VTR camera. In the figure 1
01, 102, 103, 104.

10ti is a lens forming a zoom lens system, 1o7
This is the imaging position of the younger sister zoom lens. 105 is a beam splitter that splits the beam into the finder thread; 108 is an imaging lens; 109 is a mirror;
111 is the focus plane 110 where the image is formed by
112 with a “relay lens” to make the image of
The conjugate position of the focal plane "0" by the four-way lens 111 is the conjugate position, 113 is the tangent 1t) J lens, and 114 is the pupil position of the finder system. In the figure, the finder system is
'tJ Lens 108, Mi > -109, Focus plane 11
0. Liv −L/ 7 X 111 , conjugate image position [
112 and an eyepiece lens 113, and as is clear from the figure, it has a sloppy construction and has the drawback that the overall length of the finder system is long.

On the other hand, a reverse Galilean finder conventionally used in lens-shutter cameras and the like has an extremely simple configuration as shown in FIG. In Figure 2, 201f
In the i-taking lens system, 202 is the imaging position. Still 203
is the objective lens of the finder system, 204 is the eyepiece lens of the finder thread, and 205i is the pupil position of the finder system. As is clear from FIG. 2, this type of inverted Galilean type finder has the disadvantage that variation occurs between the photographing lens system and the finder system.

The present invention eliminates the drawbacks of the finder system shown in FIGS. 1 and 2, has a simple configuration, has no variation, and has a short overall length of the finder system. The object of the present invention is to provide a finder that can be A beam splitter 1 is provided in the section to split the beam from the axial object in a direction perpendicular to the optical axis up to the afocal section of the zoom lens, and the beam splitter 1 bends a part of the incident beam. Then, a lens system after the afocal part of the zoom lens is provided in the light flux as a photographic thread,
At least one concave lens is provided in the beam passing through the beam splitter 1 in the same direction as the optical axis up to the afocal portion of the zoom lens, and the lens thread up to the 77 ocular portion of the zoom lens and the concave lens are provided. A synthetic lens system with the above is used as an objective lens, at least one convex lens is provided behind the concave lens, and the convex lens is used as an eyepiece, and up to the afocal part of the zoom lens, a light beam with an F number brighter than the F number required for photography is produced. The diameter of the lens is made large so that the light beam with an F number brighter than the F number required for photography is directed outside the semi-transparent part of the light beam splitter 1, and the light beam splitter 1 and the concave lens 7 A mirror is provided between the light beam splitter 1, the concave lens, and the mirror that bends the light beam passing outside the semi-transparent part so as to be perpendicular to the optical axis up to the afocal part of the zoom lens. A beam splitter 2 is provided which bends a part of the beam from the mirror in the same direction as the optical axis up to the 77 ocular portion of the zoom lens, and an image and a half of the beam passing through the semi-transparent part of the beam splitter 1 are provided. This is achieved by an inverted Galilean type finder capable of focusing, which is characterized in that it is possible to see the coincidence of the light beam passing outside the transparent part with the image.

The present invention will be described in detail below using drawing F1.

3(a) and 3(b) are cross-sectional views of the same embodiment row taken in a direction perpendicular to each other.

In FIG. 3, lenses 301, 302, 303
.

This is a lens system up to the afocal part of the 304-ha zoom lens, and is a light beam splitter 1 manufactured by 305 Company. Luminous flux splitter ■30
5 splits and reflects most of the incident light beam perpendicular to the optical axis direction, and forms an image on a focal plane 307 by a lens 306, which is the original rod thread after 7 focal lengths of the zoom lens.

On the other hand, in the finder system, there is a part of the light beam split and passed in the same direction as the optical axis by the line light beam splitter 1305.

A beam splitter A 308 following the beam splitter 1305 is a beam splitter used for lens focusing, and is connected to the next concave lens 309i.
Lens thread to the afocal part of the 1L zoom lens (
It is combined with the lenses 301, 302, 303, and 3043 to form the objective lens of the finder. Behind this concave lens 309 is a convex lens 310 that becomes an eyepiece a.
312 constitutes a reverse Galilean off-finder thread together with the objective lens, and 312 is the pupil position of this finder system.

311a1 and 311b shown in FIG. 3(b) are reflecting mirrors, and only the shaded part of the 2° beam splitter 1305 used for focusing together with the beam splitter It 308 is a semi-transparent part, and the outside is a semi-transparent part. Transparent, luminous flux splitter■
The light beam passing through the transparent part 305 is reflected by the mirror 311a.

31 lb and the beam splitter 11308 are used exclusively for the finder system.

For lenses 301, 302, 303, and 304 up to the afocal part, %2, the diameter of the lens should be increased so that light beams with an F number brighter than the F number, which is essential for zoom lens photography, can pass through. The beam of light with an F number brighter than the normal F number passes through the transparent part of the beam splitter 1305.

Also, between the light beam splitter 1305 and the concave lens 309, the light beam passing through the transparent part of the light beam splitter 1305 is reflected by a mirror 311a.
, 311b so as to intersect one angle with the optical axis up to the afocal portion of the zoom lens, and the beam splitter 1305, the concave lens 309, and the reflecting mirror 311
The above-mentioned reflection &! A portion of the light beams from 311a and 311b is recessed in the same direction as the optical axis up to the afocal portion of the zoom lens, and an image of the light beam passing through the oblique part of the light beam splitter 1305 and a transparent portion of the light beam splitter 1305 are formed. Focusing is achieved by matching the light beam passing through the image with the image.

Among the luminous flux from a certain axial object, the luminous flux near the optical axis and the luminous flux passing through the bright part of the luminous flux splitter 1305 are both located at the pupil position 31.
Coming to 2. Luminous flux division @l 3 (At 15, the on-axis beam is in focus and afocal, so the two beams of mJ 6 pins have the same corner plate and are subjected to finder it h -m.

On the other hand, assume that the distance scale of the zoom lens is C1, and that the on-axis object has a finite distance TK. Now lens 301,
3(+2, 3(+3, 304 and concave +/7z 30
9, the combined focal length of the lens 301 is f, the distance from the axis of the maximum luminous flux of an axial object incident on the lens 301 is H, and when that luminous flux passes through the transparent part of the luminous flux splitter 13o5, e = i+
It has an incident angle of 7 T, and the lens 301,
302, :(A composite yarn of 03, 304 and concave V7 lens 309 has an image height of Y=fθ. Since the image height is at a light flux position of 0 near the optical axis, the two IMhY=fθ are separated. Also, the reflecting mirror Luminous flux ti2 passing through 311a and reflection fi311b
The images are separated by Y=2fθ.

Here, when the distance scale of the zoom lens is set to T, the light beam from the axial object becomes 7 focal points at the beam splitter 13050 portion, and the above-mentioned plurality of images coincide.

As explained above, it was possible to obtain a reverse Galilean off-finder that is parallax-free and capable of focusing with a short overall length using a simple configuration.

Although the six-beam splitter 130Fi is provided with a transparent portion in this embodiment, the portion may be made of air instead of glass.

[Brief explanation of the drawing]

Figure 1 shows the finder optical system of a conventional camera using a zoom lens, Figure 2 shows the inverted Galileo pointer optical system used in a conventional lens-shutter camera, and Figure 3 (al,
(b) is a cross-sectional view of an optical system showing an embodiment of the present invention, taken in a direction perpendicular to each other. 301.302,303,304 A7. - Lens system up to the cull portion 305... Luminous flux splitter l 308... Luminous flux splitter] 309... Concave lens 310... Convex lenses 311a, 311b -.・Reflector 312...Visual field frame representative Yoshi Kuwahara Yoshimi yJ, <-e>

Claims (1)

[Claims] In an optical device that uses a zoom lens as a photographing optical system, which has a part where the light flux from the axis becomes approximately afocal, the light flux from the on-axis object is transferred to the afocal part, and the light flux from the on-axis object is transferred to the afocal part of the zoom lens. A beam splitter 1 is provided to split the beam in the direction of the axis 1α, and the beam splitter 1
By bending a part of the incident light flux, a lens system after the afocal part of the zoom lens is provided in the light flux to serve as a photographing thread, and the light flux splitter l is
At least one concave lens is provided in the light beam passing in the same direction as the optical axis direction up to the focal part, and a composite lens system of the lens thread up to the seven focal parts of the zoom lens and the concave lens is used as an objective lens. , at least one convex lens is provided behind the concave lens, the convex lens is used as an eyepiece, and the lens diameter is made large so that a beam of light with an F number brighter than the F number required for photographing passes up to the afocal portion of the zoom lens. and the F required for shooting.
The light beam with an F number brighter than the F number passes through the outside of the semi-transparent part of the light beam splitter 1, and the light flux passing outside the semi-transparent part is passed through the zoom lens between the light flux splitter 1 and the concave lens. A mirror that applies one force perpendicularly to the optical axis up to the afocal part of the zoom lens is provided, and a part of the light flux from the mirror is transferred between the light beam splitter 1, the concave lens, and the mirror to the afocal part of the zoom lens. A beam splitter 2 is provided that bends the optical axis in the same direction as the optical axis up to the part, and it is possible to see a match between the image of the beam passing through the semi-transparent part of the beam splitter 1 and the image of the beam passing outside the semi-transparent part. A reverse Galilean type finder that allows focusing.