JPH03168729A - Photography system with ttl finder system - Google Patents

Abstract

PURPOSE:To simplify the association mechanism between the photography system and finder system and to vary the power of the finder system as well as the photography system by arranging a reflecting mirror which reflects the luminous flux from a subject to the finder system so that the reflecting mirror can freely be extracted, and moving a finder objective linearly associatively with the movement of the moving lens group of the photography system at the time of varying power. CONSTITUTION:The finder objective 8 is arranged in the optical path of reflection of the reflecting mirror 7, the finder objective 8 is moved on the optical axis associatively with the power variation of the photography system to vary the finder power, and the other piece of luminous flux split by a half-mirror 9 is guided to a light measuring means 18 or distance measuring means. When the power of the finder system is varied, the 2nd lens group 2 of a photographic lens 20 is moved nonlinearly on the optical axis and the finder objective 8 is moved linearly on the optical axis to prevent a primary image formation plane 11 from shifting in position owing to the power variation. Consequently, the photographic lens system is reduced in size on the whole and a finder image having no finder parallax can be observed.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a photographing system having a TTL finder system,
In particular, by moving the finder objective lens, which forms part of the finder system, in conjunction with the movement of the movable lens group that accompanies changing the magnification of the shooting system, the viewfinder magnification can be changed and the photometry means, distance measurement means, etc. can be adjusted appropriately. The present invention relates to a photographing system having a TTL finder system with a simple configuration suitable for a photographing system such as an electronic still camera or a video camera.

(Prior technology) Traditionally, TT has been used in photo cameras, video cameras, etc.
Photography systems with an L finder are often used because they do not have finder balax.

Among these, in most cases where a zoom lens is used as a photographing system, a diaphragm is placed behind the variable magnification section, and a fixed or removable reflector is placed near the diaphragm. A configuration is used in which the light beam that has passed through a part of the photographing system is reflected and guided to the finder system.

With such a configuration, the viewfinder magnification of the finder system is simultaneously changed as the photographing system changes magnification, so that a subject image corresponding to a change in the photographing range can be observed without finder parallax.

A photometric device and a distance measuring device are arranged in a part of the finder system to perform photometry and distance measurement.

(Problems to be Solved by the Invention) Generally, when a zoom lens is used as a photographing system and an attempt is made to achieve a high zoom ratio, the overall length of the lens becomes long and the diameter of the front lens also becomes large. For example, from the object side,
A so-called 4-group zoom lens or negative refractor consists of a lens group, a second lens group for zooming, a third lens group for correcting the image plane that changes with zooming, an aperture, and a fixed fourth lens group. It is made up of two lens groups, the first lens group with positive refractive power and the second lens group with positive refractive power, and both lens groups are moved to change the magnification, achieving high variable power in so-called two-group zoom lenses. If you try to do so, the overall length of the lens becomes longer, and the diameter of the front lens also increases, making the entire photographic lens system larger.

Furthermore, if the finder system of such a photographic lens system is constructed using the TTL method to avoid finder balax, and also includes a light metering means and a distance measuring means as part of the viewfinder system, the entire lens system becomes even larger. There was a problem with the

The present invention employs a zoom-type lens configuration that can easily obtain a predetermined variable power ratio while preventing increases in the overall lens length and front lens diameter, and allows easy attachment of photometry and distance measurement means. The finder magnification changes as the magnification of the system changes,
Moreover, it is an object of the present invention to provide a photographing system having a TTL finder system capable of observing a finder image without finder balax.

(Means for Solving the Problems) A photographing system having a TTL finder system according to the present invention changes magnification by moving at least one lens group placed before and after the aperture. Alternatively, a removable reflector is installed in the rear optical path, and after the reflector reflects the light beam from the subject, one of the light beams divided by a half mirror is guided to the eyepiece to observe the subject image. In a photographing system having a TTL finder system, a finder objective lens is placed in the optical path reflected by the reflecting mirror, and the finder objective lens is moved along the optical axis in conjunction with the zooming of the photographing system to adjust the finder magnification. It is characterized in that the other of the luminous fluxes split by the half mirror is guided to a photometer or a distance-measuring means.

Particularly, in the present invention, when changing the magnification of the photographing system, at least one movable lens group in front of the diaphragm is moved non-linearly, and at least one lens group among the movable lens groups behind the diaphragm is moved non-linearly. The present invention is characterized in that the finder objective lens is moved linearly.

(Embodiment) FIG. 1 is a schematic diagram of a main part of an embodiment of a photographing system having a TTL finder system of the present invention.

In the figure, reference numeral 20 denotes a photographic lens having a positive refractive power and having a variable magnification function. The photographing lens 20 includes a first lens group 1 having a focusing function, a second lens group 2 with a negative refractive power that moves non-linearly on the optical axis toward the image plane during zooming, and an aperture stop.
Furthermore, during zooming, the third lens group 4 has a positive refractive power and moves linearly on the optical axis in the opposite direction to the second lens group 2.

The diaphragm 3 is arranged between the second lens group 2 and the third lens group 4 so as to be fixed with respect to an image sensor 6, which will be described later. Reference numeral 5 denotes a parallel plane plate, which is composed of, for example, an optical low-pass filter or an infrared filter. Reference numeral 6 denotes an image sensor, which is composed of, for example, a CCD.

In this embodiment, a photographing lens 20, an aperture 3, a parallel plane plate 5,
Each element of the image sensor 6 constitutes a variable magnification imaging system.

Reference numeral 7 denotes a movable reflecting mirror that can be freely inserted and removed in the photographing optical path, and is provided in front of the aperture 3. The reflection m7 is located at the position indicated by the solid line during viewfinder observation, and reflects the luminous flux from the subject that has passed through the first lens group 1 and the second lens group 2, and guides it to the finder system, which will be described later. Furthermore, during photographing, it is evacuated to a position outside the photographing optical path indicated by the dotted line.

Since the reflection fi7 only needs to guide the amount of observable light to the finder system, in this embodiment, in order to prevent the photographing lens 20 from becoming larger, the size of the reflecting mirror 7 is made smaller than the diameter of the effective light beam for photographing.

Reference numeral 8 denotes a finder objective lens, which is moved linearly on the optical axis toward the reflecting mirror 7 in conjunction with the movement of the variable magnification lens group 2.4 when changing the magnification of the photographing system.

Reference numeral 9 denotes a fixed half mirror, which divides the light beam passing through the finder objective lens 8 into two parts, one on the observation side and the other on the photometry means 1.
8 (distance measuring means).

10 is the first field lens, which is the 0 of the finder.
9, that is, an erector lens 12 whose image on the reflecting mirror 7 will be described later.
It has an optical function to form an image in the vicinity of .

Reference numeral 11 denotes a primary imaging plane, on which an inverted first object image is formed by the finder objective lens 8. Reference numeral 12 denotes an erector lens, which corrects the inverted first object image formed on the primary imaging surface 11 into an erect normal image, and forms the image on a secondary imaging surface 14, which will be described later. 13 is a second field lens, which has the function of relaying the exit pupil image formed near the erector lens 12, that is, the image of the reflecting mirror 7, to the vicinity of the eye point 16, and uniformizes the viewfinder field of view. The brightness is set so that the viewfinder image can be observed.

Reference numeral 14 denotes a secondary image forming surface, on which a second object image in the form of an erect image is formed by the erector lens l2. 15 is an eyepiece lens, and 16 is an eye point for observation.

In this embodiment, the first lens group 1, the second lens group 2, the reflector 7, the finder objective lens 8, the half mirror 9, the first
The field lens 10, the erector lens 12, the second field lens 13, and the eyepiece lens 15 constitute a finder system.

In this embodiment, during photographing, the reflecting mirror 7 is retracted out of the photographing optical path as shown by the dotted line in the figure. As a result, a light beam from an object (not shown) that has passed through the photographic lens 20 passes through the parallel plane plate 5 and forms an image on the image sensor 6 .

Also, when changing the magnification from the wide-angle end to the telephoto end, the second lens group 2
is moved non-linearly on the optical axis from the object side to the image side, and the third lens group 4 is moved linearly on the optical axis from the image side to the object side.

Next, when observing the finder image, the reflecting mirror 7, which had been retracted outside the photographing optical path, is inserted into the photographing optical path as shown by the solid line. As a result, the first lens group 1 of the photographing lens 20,
A part of the luminous flux from the subject that has passed through the second lens group 2 is reflected by a reflecting mirror 7 toward the camera, passes through a finder objective lens 8, and is reflected by a half mirror 9 toward the viewing side.

The light beam reflected by the half mirror 9 passes through the field lens 10 to form an inverted first object image on the primary imaging plane 11. and the first image formed on the primary imaging plane 11
A light beam based on the object image is passed through the erector lens 12 and the second field lens 13, thereby re-forming the second object image as an erect image on the secondary imaging plane 14. A second object image formed on the secondary imaging plane 14 is observed from the eyepoint 16 through the eyepiece 15.

Also, when changing the magnification of the photographing system from the wide-angle end to the telephoto end, the finder objective lens 8 moves light from the primary imaging plane fill to the reflecting mirror 7 side in conjunction with the movement of the second lens group 2 of the photographing system. It moves linearly on the axis.

Further, the light beam that has passed through the half mirror 9 is condensed by a condenser lens 17 and guided to a photometry means 18. At this time, the condenser lens 17
By appropriately setting the light-receiving area of the photometry means 18, photometry of an arbitrary area within the photographing range is performed. In this embodiment, a distance measuring means may be provided instead of the photometric means 1B.

Conventionally, when changing the magnification of a photographic lens having this type of variable magnification function, the second lens group 2 is generally moved linearly, and the third lens group 4 is moved non-linearly accordingly. Met.

However, in this case, when changing the magnification of the finder system, 1
In order to prevent the position of the next imaging plane from changing, the finder objective lens 8 had to be moved non-linearly in conjunction with the movement of the second lens group 2. For this reason, when changing the magnification, the mechanism for interlocking the photographing system and the finder system became complicated on the finder side, and the overall device tended to become larger.

Therefore, in this embodiment, in order to simplify the interlocking mechanism between the photographing system and the finder system, when changing the magnification of the finder system, the second lens group 2 of the photographing lens 20 is moved non-linearly on the optical axis. The finder objective lens 8 is moved linearly on the optical axis to prevent the position of the primary imaging plane 11 from changing due to zooming.

In this embodiment, the diaphragm 3 is disposed between the second lens group 2 and the third lens group 4 and fixed to the image sensor 6, thereby reducing the diameter of the front lens of the first lens group 1. The second
By moving the lens group 2 and the third lens group 4 in opposite directions to change the magnification, the overall length of the lens is shortened.

In addition, a removable reflector 7 is installed in the photographing optical path in front of the diaphragm 3, and the reflector 7 is used to observe the finder image, so that changes in the angle of view due to magnification and focusing by the front lens are possible. It has the advantage of allowing you to always see a bright viewfinder image when checking the alignment, regardless of the aperture value.

As described above, in this embodiment, a reflector 7 is provided in front of the diaphragm 3 to reflect the light flux from the object to the finder system, and is detachably inserted into the optical path of the photographing system. By moving the finder objective lens 8 in conjunction with the movement of the lens 4, the magnification states of the photographing system and the finder system are always made to match. When changing the magnification,
The lens group 2 is moved non-linearly on the optical axis, and the third lens group 4 and the finder objective lens 8 are moved linearly on the optical axis.

In addition, the light beam passing through the half mirror 9 is guided to the photometry means 18, thereby making it possible to keep the photographic lens 20 compact and to change the magnification of the finder system in the same way as the photographic system using a simple interlocking mechanism. The photographing system includes a TTL finder that allows easy photometry and distance measurement.

In this embodiment, the removable reflector m7 is arranged in front of the diaphragm 3, but the same effect as described above can be obtained even if the reflector 7 is arranged behind the diaphragm 3. can.

FIG. 2 is a schematic diagram of the main parts showing the paraxial optical arrangement for zooming of the photographing system and finder system of the embodiment shown in FIG. 1. In this figure, the same elements as those shown in FIG. 1 are given the same reference numerals.

In the figure, when changing the magnification of the finder system, the second lens group 2, which is common to the finder system and the photographing system, is moved non-linearly on the optical axis as shown by the arrow in the figure, and the finder objective lens 8 ( When changing the magnification of the shooting system, the third lens group 4
) is moved linearly on the optical axis.

As described above, in this embodiment, when changing the magnification of the finder system, the viewfinder objective lens 8 is configured to move linearly on the nine axes in conjunction with the movement of the second lens group 2. We aim to simplify the interlocking mechanism between the camera and finder system.

In this example, the finder system was constructed using a secondary imaging system, but an object formed on the primary imaging surface using a Boro prism for erecting an image behind the primary imaging surface. The present invention can also be applied to a finder system of a primary imaging type in which an image is directly observed through an eyepiece.

FIG. 3 is a sectional view of a lens of Numerical Example 1, which will be described later, and FIGS. 4(A) to (D) are various aberration diagrams of Numerical Example 1 of the present invention.

Figure 4 (A). (B) shows the wide-angle end and telephoto end of the shooting system, in order.
Figure 4 (C). (D) shows the wide-angle end and telephoto end of the finder system, respectively. In the aberration diagram, d is the d line, g
indicates the g-line, F indicates the F-line, M indicates the meridional image plane, and S indicates the sagittal image plane.

The imaging system of Numerical Example 1 is a zoom lens with a variable magnification ratio of 3 that is used for an image sensor with a screen size of 1/2 inch.A fixed aperture is provided for the image sensor, and a removable reflection lens is provided in front of the aperture. A mirror is placed.

Next, numerical examples of the present invention will be shown. In Numerical Example 1, (A) shows a photographing system, and (B) shows a finder system.

Ri and FRi are the radius of curvature of the i-th lens surface from the object side, Di and FDi are the thickness and air distance of the i-th lens from the object side, and Ni, FNi and νi and Fυi are the radius of curvature of the i-th lens surface from the object side, respectively. These are the refractive index and Abpe number of the glass of the i-th lens.

Numerical Example 1 (A) [1 Shadow lens specifications F-8.16~23.65 FNo=l:2.5~3.1 2ω-52'~19.2' R5- 36.87 0 5■ Variable till-545.72 Dll- Variable RI2-
Aperture 012- variable R22- -22.90 D22 variable R23- R24 (image plane) 023- 6.45 N12-1.51633ν12-64.1 (parallel plane plate) (B) [Finder specifications] FRII- 545.7 FDII- Variable FR12
- (Mirror) FDl2- Variable FR1
7- -24.53 FDI7- Variable FItl8- 14.00 FDI8- 2.50 FN10-1.51633 Fν10-64.1 1st field lens (primary focus plane) F old 9m FD19- 2.00 FR20- Focus plane FD20-30.18 FR23- -22.44 FD23-29.00 FR30- (Eye point) (Effect of the invention) According to the present invention, as described above, the eye point is provided between the variable magnification lens groups in the photographic lens. A reflector that reflects the light from the subject to the finder system is removably placed in front or behind the aperture, and when changing magnification, the finder objective lens moves linearly in conjunction with the movement of the moving lens group in the shooting system. By configuring it so that the lens is compact, the interlocking mechanism between the shooting system and finder system can be simplified, and the viewfinder system can be changed in magnification in the same way as the shooting system, making it a simple TTL finder system. It is possible to achieve a photographing system having the following functions.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the main parts of an embodiment of a photographing system having a TTL finder system according to the present invention, and FIG. 2 is a schematic diagram of the paraxial optical arrangement for zooming of the photographing system and finder system shown in FIG. FIG. 3 is a cross-sectional view of a lens of Numerical Example 1 of the present invention, and FIG. 4 is a diagram of various aberrations of Numerical Example 1 of the present invention. In the aberration diagram (A). (B) shows the wide-angle end and telephoto end of the photographing system, and (C) and (D) show the wide-angle end and telephoto end of the finder system, in order. In the figure, 1 is the first lens group, 2 is the second lens group, 3 is the diaphragm, 4 is the third lens group, 20 is the photographic lens, 5 is a parallel plane plate, 6 is the image sensor, 7 is the reflector, 8 is the finder objective lens, and 9 is the half mirror. 10 is a first field lens, 11 is a primary imaging surface, 12 is an erector lens, 13
1 is a second field lens, 14 is a secondary image forming surface, 15 is an eyepiece lens, 16 is an eye point, 17 is a condenser lens, 1
8 is a photometric means, and Y is an image height.

Claims (2)

[Claims] (1) A removable reflector is provided in the optical path in front of or behind the aperture of an imaging system that changes magnification by moving at least one lens group placed before and after the aperture. In a photographing system that has a TTL finder system that reflects the light beam from the mirror and then guides one of the light beams split by a half mirror to the eyepiece lens to observe the subject image, there is a A finder objective lens is arranged, and the finder objective lens is moved along the optical axis in conjunction with the magnification change of the photographing system to change the finder magnification, and the other of the light beams divided by the half mirror is divided by a photometer or a distance meter. A photographing system having a TTL finder system characterized by guiding light to a means. (2) When changing the magnification of the imaging system, at least one of the movable lens groups in front of the diaphragm is moved non-linearly, and at least one of the movable lens groups behind the diaphragm and the Claim 1 characterized in that the finder objective lens is moved linearly.
Photography system with the TTL finder system described.