JP3209864B2 - Autofocus camera with movable film surface - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera having an interchangeable photographic lens, and more particularly, to a back focus control type auto focus camera in which the weight of an optical axis unit as a movable part is reduced.

[0002]

2. Description of the Related Art Generally, when a single-lens reflex camera is made into an AF system, a method of automating an operation of focusing a subject by adjusting a distance ring of a lens is adopted. As a driving method, there are a method using a motor in a body and a method using a motor in a lens, and these methods have been put to practical use. All of them are AF-only lenses, and it has not been possible to convert conventional lenses to AF.

[0003] In order to enable AF operation with a conventional MF lens based on a lens mount that can be mounted and exchanged with a conventional lens, the main body is divided into front and rear portions, and a so-called “position control of a rear film surface” is performed. The present inventors have already proposed a back focus control method. In this back focus control, the rear unit, which is a movable unit, has a photographing function including a film chamber and includes many of the functions of the camera, and therefore has a considerable weight and volume. On the other hand, A
In order to perform F, the movable portion must be controlled at high speed and precisely. In order to control the movable part at high speed and precisely, it is necessary to reduce the volume and the weight.

[0004]

Accordingly, the present inventors have made the following considerations in order to reduce the volume and weight of the movable part, and have reached the present invention. The interchangeable lens type auto focus cameras that have been used by various companies are AF
As a special case, the lens system itself has been changed, and a new system has been developed and commercialized using a method convenient for AF operation. Therefore, when using an autofocus camera with interchangeable lenses, the user has to pay a new expense of having to prepare an expensive AF lens system. On the other hand, it is also true that AF-only lenses have been advanced to obtain ideal AF operations from a new viewpoint.

In the focusing operation of the lens, the moving distance of the lens has been reduced and the lens has been reduced in weight in order to increase the accuracy and the speed as much as possible. as a result,
Each lens was designed to meet its requirements, and each lens was able to achieve its performance. Cameras made in such a background are the mainstream of current AF cameras. On the other hand, the present inventor has worked on the problem of whether an autofocus camera that can use the conventional manual lens system as it is can be used from the viewpoint of the user's benefit separately from the mainstream of the AF camera. Has proposed a new back focus control method that allows focus adjustment on the camera body side.

This system uses an ABF (Automatic Back) to distinguish it from the conventional autofocus.
Focusing) System. In connection with this camera, many proposals have been made for a configuration for realizing a new function that cannot be predicted by a conventional camera. However, in commercialization, although there is a great merit that auto focus can be performed using a conventional manual lens, this method is equivalent to a so-called lens whole group movement adjustment method in which the distance ring of the lens is fixed, It was a big problem how many mm the movable range of the camera body flange back was. By the way, Table 1 lists representative lenses of various types of lenses that have been marketed so far, and summarizes the shortest photographing distance and the extension amount of these lenses. (Hereinafter referred to as margins.)

[Table 1]

Table 1 shows 18 types of lenses ranging from a wide-angle lens having a focal length of 15 mm to a super-telephoto lens having a focal length of 300 mm. For example, the shortest photographing distance of a wide-angle lens of N0.1 is 160 mm and that of N0.20 is That of the super telephoto lens is 3500 mm, and the maximum extension amounts of those lenses are 2.8 mm and 30.85 mm, respectively. Ideally, the maximum movable distance of the camera body back is set so as to cover the entire photographable range of a commercially available lens system. However, the amount of extension is not possible due to the size of the camera body.

Therefore, in determining the camera body back adjustment distance, one model of an autofocus camera adopting the present invention takes into consideration the size of the camera and the like, and has a maximum extension amount of various commercially available interchangeable lenses. At about the middle, and commonly used focal length 85m
The inventor of the present invention has found a compromise that it is only necessary to cover each of the shortest shooting distances up to the m lens. If the distance ring of the lens is set to the ∞ position, the focal length is 85 mm
For the various lenses up to, the A
As a result of obtaining the movable range in which the F response can be obtained, the movable control distance is 1
The conclusion was 0 mm. However, it is not that other lenses with a focal length longer than this cannot perform AF shooting up to the intrinsic shortest shooting distance, but manually turn the distance ring to the finite side according to the distance of the subject to be shot, and respond to back focus. The AF operation can be performed by being within the possible range.

The object of the present invention is based on the above considerations. In order to further reduce the volume and weight of a movable part, a film chamber and a film feeding mechanism are provided on a fixed side serving as an external part of a camera. While the movable range in the optical axis direction is within the range of the above-mentioned compromise, the film opening before focusing is formed so that the film at both ends of the film opening can be sagged even if the film opening is brought to any position in the movable range. By positioning the position, the moving parts can be moved at the time of auto focus, so that the load such as film tension due to the separate installation of the film chamber etc. does not occur, and higher speed back focus control is possible And expand the functions of more conventional lenses (AF can be used for manual lenses and short-distance shooting is possible from the shortest shooting distance of the lens) Is to provide a film plane movement autofocus camera macro function) can be achieved for.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, a film surface moving type autofocus camera according to the present invention mainly comprises a camera external part having a lens mount for a photographing lens and a back cover for taking in and out of the film. And a finder mechanism, a distance measuring mechanism, an exposure mechanism, and a film opening disposed at the center of the optical axis of the photographing lens, and can be moved by a predetermined distance in the optical axis direction with respect to the camera exterior fixing section. An autofocus camera including a flexible optical axis unit, a film winding side and a rewinding side film chamber disposed on the left and right of the film opening, and a film feeding mechanism for feeding the film. And the optical axis unit is accommodated in the film opening and the film chamber when the optical axis unit is moved to any position in the entire movable range. Between the cartridge and the spool, which
For focusing by Rumi similar Whereas the cartridge and the spool so as to be formed in advance to position the film opening portion of the optical axis unit in a predetermined position, moving the optical axis unit in the optical axis direction thereafter It is configured as follows.
The predetermined position of the film opening in the present invention is a film winding position, and after the shutter operation is completed, the optical axis unit is moved to the predetermined position to wind the film. Further, the film winding position in the present invention can be set to the maximum moving distance of the movable range of the optical axis unit.

The invention proposed by the inventor of the present invention has an unprecedented feature that the body operation is performed in the AF operation, and the distance ring adjustment of the lens is performed separately in the manual operation. It can be said that the camera is capable of freely intervening by the user's will in shooting.
Therefore, it is not always necessary to increase the movable range of the flange back, and the movable range is not limited to 10 mm as described above.
Even if it is m, it is sufficient as a commercial product, and those having a reduced movable range are also on the same concept of the present invention. From the above point of view, when considering only a model that does not greatly increase the movable range, a film cartridge that holds the film in the film opening of the optical axis unit on the optical axis and is disposed on the left and right sides of the film opening. Attach the take-up spool to the camera fixed side, position the film opening so that the film on both sides of the film opening can be slack when the optical axis unit is moved, and move only the optical axis unit parallel to the optical axis It was made.

[0012]

According to the above construction, the movable portion can be limited to only the optical axis unit centered on the optical axis, so that the weight reduction of the movable portion can be realized and the drive mechanism is simplified. Therefore, the size and weight of the optical axis unit and the operating speed and accuracy are improved at the same time as the size and weight of the entire camera.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings. First, the A of each lens when the present invention is applied
The response range of F will be described. FIG. 1 shows the relationship between the position of the lens distance ring and the AF response range when a typical telephoto lens 135 mm is attached to a camera in which the movable range of the flange back is 10 mm, 5 mm, and 3 mm, respectively. In the ABF system, the response range of AF is determined by the movable range of the flange back, and the response range of AF is moved by manually adjusting the distance ring of the lens. In FIG. 1, the vertical axis indicates the set position of the distance ring of the photographing lens, and the horizontal axis indicates the photographing distance of the subject.

This figure is a characteristic diagram of a commercially available manual lens (planar 135 mm / F2 in Table 1). Since the shortest photographing limit distance unique to this lens is 1.5 m, the adjustment range of the distance ring is from ∞ to 1.5.
m. As in the prior art, when shooting manually, focusing can be achieved by setting the distance ring of the lens according to the shooting distance of the subject. This is indicated by a straight line ab (MF line) drawn obliquely, and indicates that the photographing can be manually performed up to 1.5 m from ｍ. Here, an ABF system according to the present invention is introduced, and F
When the movable range of B (flange back) is specifically set to 10 mm, 5 mm, and 3 mm as a parameter, the curve represents the response range of the shortest photographing distance AF that varies depending on the distance ring setting position of each lens. .

As is apparent from this figure, if the lens is set at the position ∞, the distance between the horizontal line at the position ∞ and the point (c ₁ , c ₂ , c ₃ ) where each curve intersects from the position ∞ to the closest AF response range. In this example of the telephoto lens, the close response range is larger than the shortest photographing distance unique to the lens (about 2 m for the curve, about 3.7 m for the curve, and about 6 m for the curve). It can be seen that when the manual operation of slightly adjusting the distance ring is also used in accordance with the above, the responsive range moves to a shorter distance side than the above. However, if the distance ring is set to the finite side, it is naturally impossible to respond at a further distance, and the range shifts to the short distance side and the range becomes narrower. Therefore, in general photography, it is necessary to set the distance ring of the lens to the ∞ position where the AF response range becomes the widest, but in close-up photography, it is possible to shoot as much as possible by adjusting the distance ring according to the distance The area can be set on the short distance side.

[0016] When combined adjustment by distance ring thus, if the movable range of the FB is 10mm ac ₁ d ₁ ba
AF shooting is possible in the range of ( ₁ ), and the shooting range (e ₁ ) from the shortest shooting distance (1.5 m) unique to the lens to the closer side.
d ₁ be ₁ ) is moved, and the photographer's selection range of the photographing distance is widened. Here, when the movable range of the FB is 5 mm, a
In the case of c ₂ d ₂ ba, 3 mm means that the range of ac ₃ d ₃ ba is AF.
Become response range, both can include a minimum object distance, although more gradually range narrower becomes come, shooting range (e ₂
d ₂ be ₂₎ and (e ₃ d ₃ be ₃₎ it can be seen that expanding only than the conventional. When the FB movable range is 10 mm, the shooting range (e ₁ d ₁ be ₁ ) is 5 mm, the shooting range (e ₂ d ₂ be) is 3 mm, and when the shooting range is 3 mm, the shooting range (e ₃₎
d ₃ be ₃ ) is the user's benefit range,
It becomes an AF macro function. In setting the FB movable range as described above, although the specifications are different from each other, there is no change in the camera concept employing the ABF system of the autofocus camera according to the present invention. For this reason, depending on the version of the model, there may be a case where the driving distance of the FB is very small, and the present invention is intended to be adopted for a camera aiming at such miniaturization.

FIG. 2 shows a lens distance ring when a standard lens 50 mm (planar P50 mm / F1.4 in Table 1) is mounted on a camera in which the movable range of the flange back is 10 mm, 5 mm, and 3 mm, respectively, as in FIG. Position and AF
It shows the relationship of the response range. The minimum photographing limit distance unique to this lens is 0.45 m, and the adjustment range of the distance ring is from ∞ to 0.45 m. In the manual shooting using the lens distance ring, the range is a straight line ab (MF line) that is obliquely drawn, and the shooting can be manually performed from ∞ to a close distance of 0.45 m. The movable range of FB of this lens is 10m
The response ranges of the shortest shooting distance AF when m, 5 mm, and 3 mm are respectively represented by the following curves.

If the lens is set at the ∞ position, the point (c ₁ , c ₂ ,
The distance of c ₃ ) is the AF response range from ∞ to a close distance.
In this standard lens, the closest response range is about 0.98 m in the case of a curve and 0.65 m in the case of a curve. In such a case, it is larger than the shortest shooting distance unique to the lens. Is smaller than the shortest shooting distance unique to the lens. This means that the shortest photographing distance of the lens can be covered no matter where the distance ring is set. That is, if the adjustment by the distance ring is used together, when the movable range of the FB is 10 mm, ac ₁ d ₁ ba
AF shooting is possible in the range of, and the shortest shooting distance (0.45 m) unique to the lens regardless of the position of the distance ring of the lens
The photographing range (c ₁ d ₁ bfc ₁ ) is further extended to the nearest side. When the movable range of the FB is 5 mm, (ac ₂ d
_In the case of ₂ ba) and 3 mm, the range of (ac ₃ d ₃ ba) is the AF response range, which can include the shortest shooting distance, and the range gradually narrows, but the shooting range (e ₂ d) ₂ be ₂ ) and (e ₃ d ₃ be ₃ ).

FIG. 3 is a schematic sectional view showing the basic structure of a film plane moving type autofocus camera according to the present invention. In consideration of making the control movable range of the flange back relatively large, the present inventors have proposed that the film chambers disposed on both sides of the optical axis of the camera can be moved by holding the opening of the film. I've been focusing on it. However, as described above, the concept of the present invention does not depart from the concept of the present invention even for a relatively small moving distance depending on the model, and therefore, it is a new structural proposal for these models. In FIG. 3, a camera body fixing block A including an AF driving mechanism 7 for driving the optical axis unit B in the AF mode using the interchangeable lens 9, the lens mount 1, and the flange back driving motor 7a as driving sources, and a distance measuring mechanism 3 are included. It is divided into an optical axis unit (portion surrounded by a two-dot chain line) B, which is an integrated unit including a mirror box mechanism, a finder mechanism 5, and a photographing exposure mechanism including a shutter, a film opening 10 and a film holding unit 27. Note that the AF drive mechanism 7 of the camera body fixing block A
When the AF mode is released, it is also possible to drive in the MF mode to focus.

Light from a subject (not shown) passes through the interchangeable lens 9, the optical path is guided upward by the mirror 13, and enters the finder mechanism 5. In the finder mechanism 5, the light is guided by the pentaprism 5a so as to be parallel to the main optical axis, and reaches the eyepiece 5b. Part of the subject light that has passed through the interchangeable lens 9 also enters the AF mirror 3a of the distance measuring mechanism 3, the optical path is guided downward, and reaches the AF sensor 3c via the AF lens 3b. A flange back drive motor 7a is provided below the camera body fixing block A, and the rotation output of the flange back drive motor 7a is transmitted to a lead screw 7d via a gear 7c by a pinion 7b fixed to the motor shaft. When the lead screw 7d rotates, the female screw 7e moves back and forth, and the optical axis unit B
Is movable. Although not shown in FIG. 3, the film chambers on the winding side and the rewinding side are provided in the camera body fixing block A. A mechanism for feeding the film is also provided in the camera body fixing block A.

FIG. 4 is a sectional view of FIG. 3 as viewed from above. A mirror box mechanism 21 and a shutter unit 2 are provided on the right side of the mirror box 14 containing the mirror 13.
2 are provided. The optical axis unit B includes the mirror 1
3, a mirror box 14, a mirror box mechanism 21, a shutter unit 22, a film opening 10, and a pressure plate holding plate 19. The mirror box 14 is provided in fitting portions 14a, 14b, and 14c having through holes, and a slide rod 11 having both ends fixed to the camera body fixing block A and a slide rod 12 having one end fixed to the through holes. Are slidably fitted. The film chambers 15 and 16 are provided in the camera body fixing block A on both sides of the film opening 10 as described above, and the patrone 17 and the spool 18 are accommodated therein, respectively. The film feeding mechanism includes a cartridge 17, a spool 18, and a spool 1.
8 includes a drive source (not shown) for rotating the motor 8 and a gear group (not shown) for connecting the drive sources. The film 20 is held in the film opening 10 by the pressure plate holding plate 19 and wound on the spool 18.
The pressure plate holding plate 19 is attracted to the film opening 10 side by, for example, a magnet or the like, and reliably holds the film. Since the pressure plate holding plate 19 is provided on the optical axis unit B side, even if the optical axis unit B moves within the FB movable range in the optical axis direction, the pressure for holding the film does not change.

FIG. 4A shows a state where the optical axis unit B for photographing has reached the maximum movable distance position, and FIG. 4B shows a state where it is at the same reference position of the flange back as the conventional manual camera. I have. The AF operation can be performed in the movable range (FB movable range) of (a) and (b). A major problem here is the processing of the film 20 when the film is loaded and moved while holding the film 20 in the film opening 10 of the optical axis unit B. In this embodiment, since a camera having a relatively small movable distance is considered, this does not cause a great problem. However, when the film 20 stretched between the patrone 17 on the film sending side and the spool 18 on the winding side is moved in the optical axis direction, even if the movement is small, the film 20 moves backward in a state where the film 20 is stretched. It is clear that you cannot move.

In the present invention, when the film is loaded and each time the film is wound, as shown in FIG. 4A, the operation is performed with the optical axis unit B always retracted to the film rewind position. As shown in FIG. 4B, the movement of the shaft unit B only causes slacks 20a and 20b on both sides of the film 20, but does not hinder the movement. Also, the flatness of the film due to the AF operation is not significantly impaired. Although the film rewind position is the maximum movable distance of the optical axis unit B in this embodiment,
It is not always the maximum movable distance. Depending on the position where the film chambers 15 and 16 are provided, for example, when the film is pulled out most at an intermediate distance of the movable range, that position is set as the film rewind position.

FIG. 5 is a flowchart for explaining the operation of the camera according to the present invention. Hereinafter, description will be made mainly with reference to FIG. When the film is loaded, the optical axis unit B is
As shown in (a), it is brought to the maximum movement distance of the FB movable range. When the release button is depressed, the distance is measured and the AF sensor 3c sends distance measurement data to a control circuit (not shown) (S1). The control circuit calculates the defocus amount ± Δf based on the distance measurement data (S2), and drives the flange back drive motor 7a (hereinafter, referred to as “motor 7a”). The rotation output of the motor 7a is transmitted to the lead screw 7d via the pinion 7b and the gear 7c, and moves the optical axis unit B in the optical axis direction (S3). When the amount of (defocus amount ± Δf) is moved, the motor 7a is stopped, and the focus is determined (S4). If the focus position has not been reached, the process returns to S1 to measure the distance and perform the focusing operation. If it is in focus, the position of the optical axis unit B, that is, the position of the flange back, is stored in the storage unit (S5).

When the release is further depressed, the mirror 13 is raised (S6), the shutter unit 22 is operated and the shutter runs (S7), and the exposure of the film is completed. Immediately after the photographing is completed, the control circuit drives the motor 7a to move the optical axis unit B to the winding position (maximum position) (S8), and winds the film 20 (S9).
At the same time, the mirror 13 is lowered, and the operation of other mechanisms such as shutter charging is terminated (S10). When the film winding is completed, the flange back position information is read from the storage unit, and based on the information, the motor 7a is driven to return the optical axis unit B to the original focus position (S11).

[0026]

As described above, according to the present invention,
It is possible to provide a camera of a new ABF system of a simultaneous operation type of auto and manual. Although this camera is an ABF system, it is possible to further reduce the size and weight of the optical axis unit, which is a movable unit, and to perform high-speed control and highly accurate back focus control. Also, by using the manual operation of the lens together, the shooting range is further moved to the short distance side by the movable amount of the back focus, and the macro function can be realized at the same time as the AF of the manual lens. Therefore, these functions can be effective means for the user to make full use of his or her own photography technology.

[Brief description of the drawings]

FIG. 1 The movable range of the flange back is 10 m each.
FIG. 11 is a diagram illustrating a relationship between a position of a distance ring of a lens and an AF response range when a typical telephoto lens of 135 mm is mounted on a camera having a size of m, 5 mm, and 3 mm.

FIG. 2 shows a movable range of 10 m for each of the flange backs.
The position of the distance ring of the lens and A when a typical standard lens 50 mm is attached to a camera with a diameter of 5 mm, 3 mm, and 3 mm
It is a figure showing relation of F response range.

FIG. 3 is a schematic cross-sectional view of an embodiment of a film surface moving type autofocus camera according to the present invention as viewed from the side, and FIG.
Shows the infinity shooting, and (b) shows the closest shooting.

FIG. 4 is a schematic cross-sectional view of an embodiment of a film plane moving type autofocus camera according to the present invention as viewed from a plane, and FIG.
Shows a state in which the optical axis unit has been moved to the film winding position, and (b) shows a state in which the position of the FB is adjusted.

FIG. 5 is a flowchart illustrating an operation of back focus control for moving the optical axis unit according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lens mount 3 Distance measuring mechanism 5 Finder mechanism 6 Encoder 7 AF drive mechanism 8 Position detection SW 9 Interchangeable lens 10 Film opening 11, 12 Slide rod 14 Mirror box 15, 16 Film chamber 17 Patrone 18 Spool 19 Pressure plate holding plate 20 Film 21 Mirror box mechanism 22 Shutter unit 26 Back cover 27 Film holder

Claims (3)

(57) [Claims] 1. A fixing part mainly including a camera exterior part having a lens mount for a photographing lens and a back cover for taking in and out a film, a finder mechanism, a distance measuring mechanism, and a finder mechanism arranged at the center of the optical axis of the photographing lens . An autofocus camera having an exposure mechanism and a film opening, and an optical axis unit movable by a predetermined distance in an optical axis direction with respect to the camera appearance fixing part, wherein a film disposed on the left and right of the film opening A film chamber on a winding side and a rewinding side and a film feeding mechanism for feeding the film are provided in the camera exterior fixing portion, and the film opening is formed even when the optical axis unit is moved to any position in the entire movable range. as part and Rumi was between cartridge and spool accommodated in the film chamber is formed, said cartridge spool to The film opening of Kihikarijiku units leave positioned in a predetermined position, the film plane movement autofocus camera and performs focusing by moving the optical axis unit in the optical axis direction thereafter. 2. A film winding position, wherein the predetermined position of the film opening is a film winding position, and after the shutter operation is completed, the optical axis unit is moved to the predetermined position to wind the film. Autofocus camera with movable film surface. 3. The camera according to claim 2, wherein the film winding position is a maximum moving distance of a movable range of the optical axis unit.