JPH03168730A - 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 so that the reflecting mirror can freely be extracted, moving a finder objective linearly at the time of varying power associatively with the movement of a photography system moving lens group, and arranging a light measuring means and a distance measuring means to part of the finder system. CONSTITUTION:The finder objective 8 is arranged in the optical path of reflection of a reflecting mirror 7 and moved linearly 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 the light measuring means through a visual field mask 17 serving as the light measuring means to measure the light and distance at the same time. The visual field mask 17 is composed of a thin film type light measuring sensor and serves as the light measuring means. Consequently, the device is reduced in size on the whole and a finder image which has 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 photographing system, the finder magnification can be changed and the light metering means, distance measuring means, etc. can be changed in the finder system. This relates to a photographing system having a TTL finder system of a simple configuration suitable for photographing systems such as electronic still cameras and video cameras, which can perform photometry and distance measurement at the same time by appropriately disposing it in a part of the camera. be.

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

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.

By adopting such a configuration, #! As the magnification of the shadow system changes, the finder magnification of the finder system is also changed at the same time, so that the subject image corresponding to the change in the shooting range can be observed without finder balax.

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. This is a so-called two-group zoom lens that is composed of two lens groups, the first lens group with positive refractive power and the second lens group with positive refractive power, and changes magnification by moving both lens groups. 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 allows a predetermined variable power ratio to be easily obtained while preventing increases in the overall length of the lens and the diameter of the front lens, and also prevents the overall size of the device from increasing in size by using photometering means and distance measuring means. TTL allows for easy setting, the viewfinder magnification changes as the shooting system changes, and the viewfinder image can be observed without finder parallax.
The purpose is to provide a photographing system with a finder system.

(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 provided 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 g-view 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. and guiding the other of the luminous flux split by the half mirror to the distance measuring means via a field mask that also serves as a photometering means,
It is characterized by being able to perform photometry and distance measurement at the same time.

In particular, the present invention uses a thin-film type photometric sensor made of amorphous silicon or the like as a field mask, which also serves as a photometric means, so that photometry can be performed with any photometric distribution in the photographing range outside the range-finding field of view.

The present invention also provides a method for non-linearly moving at least one movable lens group in front of the aperture when changing the magnification of the photographing system, and moving at least one movable lens group in the rear of the aperture in a non-linear manner. 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 made of, for example, an optical low-pass filter or an infrared cut filter. Reference numeral 6 denotes an image sensor, which is composed of, for example, a CCD.

In this embodiment, an S shadow 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 into and removed from the photographing optical path, and is provided in front of the mirror 3. The reflecting mirror 7 is located at the position indicated by the solid line during finder 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 the light to a 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 reflector 7 only needs to guide the amount of observable light to the finder system, in this embodiment the size of the reflector 7 is made smaller than the diameter of the effective light beam for photography in order to prevent the photographic lens 20 from becoming larger. .

Reference numeral 8 denotes a finder objective lens, which is moved linearly on the optical axis toward the reflection m7 side 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 that divides the light beam that has passed through the finder objective lens 8 into two parts, one of which is guided to the observation side and the other to the photometry means and the distance measurement means.

Reference numeral 10 denotes a first field lens, which has an optical function to form an image of the pupil of the finder, that is, the image of the reflecting mirror 7, in the vicinity of an erector lens 12, which will be described later.

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 plane 11 into an erect normal image, and forms the image on a secondary imaging plane 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 12. 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.

17 is a field mask having an opening in the center for distance measurement;
8 is the third field lens, 19a and 19b are a pair of 2
The secondary imaging lenses 20a and 20b are a pair of focus detection sensors.

In this embodiment, each element 17 to 20a, 20b is disclosed in, for example, Japanese Patent Application Laid-Open No. 62-173412 or Japanese Patent Application Laid-Open No. 62-20650.
This constitutes a known focus detection system proposed in Publication No. 8. The field mask 17 blocks light beams outside the distance measurement field of view to prevent harmful light beams from entering the focus detection sensors 20a, 20b.

Further, the field mask 17 is composed of a thin film type photometric sensor made of, for example, amorphous silicon, and also serves as photometric means. Furthermore, the camera is configured so that photometry can be performed in a predetermined distribution within the photographing range other than the distance measurement field of view. For example, so-called average photometry, which allows photometry to be performed over the entire screen, can be performed.

In this embodiment, the same effect can be obtained even if the field mask 17 is removed and an amorphous silicon sensor is deposited on one side of the third field lens 18.

The third field lens 18 causes the reflecting mirror 7 to form an image in the vicinity of the secondary imaging lenses 19a and 19b, and also forms an image of the ranging field mask 17 with uniform brightness on the focus detection sensors 20a and 20b. ing. A pair of secondary imaging lenses 19a and 19b image the left and right light beams of the pupils of a photographing lens (zoom lens) onto a pair of line-shaped focus detection sensors 20a and 20b, respectively.
Focus detection is performed by a known method by detecting the amount of relative shift between the two images formed at a and 20b.

In this embodiment, when photographing, the reflection l! 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 viewfinder image, the reflection I that was evacuated outside the photographic optical path! 7 into the photographing optical path as shown by the solid line. As a result, the first lens group l of the photographic lens 20
, and a part of the luminous flux from the object that has passed through the second lens group 2 is reflected upward to the camera by a reflecting mirror 7, 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 surface 1l. Then, a light beam based on the first object image formed on the primary imaging surface 11 is passed through the erector lens 12 and the second field lens 13, thereby forming a second object image as an erect image on the secondary imaging surface 14. It is being re-imaged. 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 surface 11 side to the reflection 1i7 side in conjunction with the movement of the second lens group 2 of the photographing system. It moves linearly on the axis.

Further, the luminous flux passing through the half mirror 9 is guided to the distance measuring means and the photometry means of the field mask 17, and at this time, the field mask 17
By appropriately setting the light-receiving area of the camera, photometry of an arbitrary area within the shooting range can be performed simultaneously with distance measurement or separately from distance measurement.

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 provided in the photographing optical path in front of the diaphragm 3, and the viewfinder image is observed using the reflector #X7, 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.

In this way, in this embodiment, the light beam from the subject is reflected in front of the aperture 3 to the finder system. 7 is removably inserted into the optical path of the photographing system, and the finder objective lens 8 is moved in conjunction with the movement of the second lens group 2 and third lens group 4 during zooming, so that the photographing system and the finder system are always connected. Matching magnification status. When changing the magnification,
The second lens group 2 is moved non-linearly on the optical axis, and the third lens group 4 and 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 distance measuring means and the photometering means, thereby keeping the photographing lens 20 compact and allowing the viewfinder system to change the magnification in the same way as the photographing system using a simple interlocking mechanism. In addition, the photographing system is equipped with a TTL finder that allows easy photometry and distance measurement.

In this embodiment, the removable reflecting mirror 7 is arranged in front of the aperture 3, but the same effect as described above can be obtained even if the reflecting mirror 7 is arranged behind the aperture 3. Can be done.

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 f/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 is moved non-linearly as shown by the arrow in the figure. 8 (the third lens group 4 when changing the magnification of the photographing system) is moved linearly on the optical axis.

In this way, in this embodiment, when changing the magnification of the viewfinder system, the viewfinder objective lens 8 is configured to move linearly on the optical axis in conjunction with the movement of the second lens group 2, so that the imaging system 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.

(Effects of the Invention) According to the present invention, as described above, a reflector that reflects the light flux from the subject to the finder system is removably disposed in front of or behind the diaphragm provided between the variable magnification lens groups in the photographic lens. However, when changing the magnification, the finder objective lens is configured to move linearly in conjunction with the movement of the movable lens group of the photographing system, and the photometry means and distance measurement means are arranged in a part of the finder system. To achieve a photographing system having a TTL finder system with a simple configuration, in which the interlocking mechanism between the photographing system and the finder system can be simplified while keeping the photographing lens compact, and the finder system can change the magnification in the same way as the photographing system. Can be done.

[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. 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 photographing lens, 5 is the parallel plane plate, 6 is the image sensor, 7 is the reflector, and 8 1 is a finder objective lens, 9 is a half mirror, 10 is a first field lens, 11 is a primary imaging surface, 12 is an erector lens, 13
is the second field lens, 14 is the secondary imaging plane, l5 is the contact/obstruction plane, 171 is the second field lens, 18 is the third field lens, 19 a. 1 9 b is a secondary imaging lens, and 20 a, 20 b are focus detection sensors.

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 also serves as a photometry means. A photographing system having a TTL finder system, characterized in that light is guided to a distance measuring means via a field mask so that photometry and distance measurement can be performed simultaneously. (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.