JPS6046686B2 - automatic focus adjustment device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic focus adjustment device used in cameras and the like.

When automatically adjusting the focus of a camera or the like, one problem is the mechanism for driving the lens system.

Naturally, in high-end cameras, it is necessary to adjust the focus by continuously changing the focal length of the photographing system, but such a mechanism is inevitably complicated and expensive. Therefore, by adopting the zone focus focusing method used in intermediate-level cameras, the automatic focus publication No. 47-20731 allocates a specific zone to each of multiple distance-measuring optical systems. This document describes a device that measures whether the zone is in focus and moves the lens system to a position where the zone is in focus. Adopting zone focusing in this way not only simplifies the distance measurement system, but also simplifies the structure of the lens system drive mechanism, as it is only necessary to change the focal length of the lens system to each set zone position. I can do it. However, the above-mentioned Special Public Interest Publication No. 47-2073
In the device described in Publication No. 1, the mechanism for changing the focal length of the lens system is basically a normal focusing method,
In other words, it is similar to the method of continuously changing the focus,
This is done by moving all or part of the lens system in the optical axis direction. The mass of the parts driven for this purpose was not particularly reduced by adopting the zone focus type, and no improvement was seen in this respect. An object of the present invention is to provide a focal length adjustment device suitable for an automatic focus adjustment mechanism that employs a zone focus type.

The present invention is an apparatus that performs automatic focus adjustment using a zone focusing method, and in order to provide the lens system with different focal lengths corresponding to each zone, some lenses of the lens system have a plurality of different focal lengths. The lens is configured such that any one of these lenses can be selectively inserted into the optical path at high speed, and is characterized by being equipped with a drive device that switches to the optimal lens based on a signal from the distance measuring device. be.

The invention will be explained in detail below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of a focusing device according to the present invention.

In the present invention, the focal length of the photographic lens system is changed by replacing a part of the photographic lens system (not shown), for example, one of the rear group lenses. In this embodiment, a four-point zone focus is adopted, and four interchangeable lenses 1 to 4 with different focal lengths are attached to a fan-shaped lens stand 6 that rotates in the direction of the arrow around an axis 5, and this is attached to the photographing lens. It is used as part of the system. In the illustrated position, the lens stand 6 has been fully rotated counterclockwise.
When the lens stand 6 rotates clockwise from this position,
First, when the lens 1 reaches the position indicated by the broken line 10, the optical axis of the lens 1 coincides with the optical axis of another photographic lens system placed on the front side of the paper, thereby forming the photographic lens system as a whole. When the lens stand 6 further rotates clockwise from this position, the lenses 2, 3, and 4 sequentially come to the position indicated by the broken line 10, each forming a part of the photographic lens system. As mentioned above, since the light conversion lenses 1 to 4 have different focal lengths, the focal length of the entire photographic lens system changes depending on which lens is used in the photographic lens system. Therefore, if you set the focal length of the photographic lens system when each lens is used as a photographic lens to correspond to each zone in the zone focus method, by switching lenses 1 to 4, you can use the zone focus method. This means that focus adjustment can be achieved by The actual operation is as follows.

First, by winding up the film, the shutter is charged, and the lens stand 6 is also rotated counterclockwise against the spring 7 to the position shown in the figure, where it is locked by the stopper 8. When the release button is pressed, the stopper 8 rotates around the shaft 9, and the lens stand 6 is unlocked and pulled by the spring 7 to rotate clockwise. A switch piece 11 is attached to the lens stand 9, and this is a fixed lens stand position detection electrode 12.
15 and the lens stand 9 are sequentially brought into contact with each other as they rotate, thereby detecting which of the interchangeable lenses 1 to 4 is to be used as a photographic lens system. If the distance measuring optical system is provided independently of the photographing lens system and configured to detect which lenses 1 to 4 to use before the shutter release, the lens stand position detection electrodes 12 to 15 are used. It is preferable to provide means for detecting the rotational position of the lens stand 9.

When the release button is pressed, that is, when the lens stand 9 is in the position shown, the switch piece 11 is connected to the detection electrode 1.
2, and a signal can be obtained from this electrode. For example, if information is obtained from the ranging device 16 that it is okay to use the lens 1, the control circuit 1
7 operates in response to a signal from the electrode 12 to energize the electromagnet 18 and rotate the stopper 19 about the shaft 20 in the direction of the arrow. Therefore, the claw 21 provided on the fan-shaped lens stand 6
23, the claw 21 engages with the stopper 19 to stop the lens stand 6 when the lens 1 comes to the position indicated by the broken line 10. Similarly, when the distance measuring device 16 obtains information that the lens 3 should be used, the control circuit 17 is activated by the signal from the detection electrode 14, so the lens stand 6 is rotated. When the switch piece 11 comes into contact with the detection electrode 14, the control circuit 17 operates to rotate the stopper 19 in the direction of the arrow. This is done at a timing when the pawl 22 passes the position of the stopper 19 and before the pawl 23 comes to the position of the stopper 19, so the pawl 23 and the stopper 19 engage with each other, and at this point the rotation of the lens stand 6 begins. stops. Of course, the lens 3 at this time is placed at the position indicated by the broken line 10. The same applies when using lenses 2 and 4, but when using lens 4, the stopper 19
does not operate, but rotates until the lens stand 6 hits the stopper pin 24, and at this position the lens 4 is exactly at the position indicated by the broken line 10. Therefore, the detection electrode 15 may be omitted. Also, if the rotation speed of the lens stand 6 is stable, the timing for actuating the stopper 19 is from the electrode 12 to
Instead of detecting and determining the position of the lens stand 15, the timing may be controlled based on the time that has passed since the rotation of the lens stand 6 started. In the above embodiment, the distance measuring device 16 was provided independently of the photographing lens system, but
It can also be associated with a photographic lens system.

For example, distance measurement can be performed using the TTL method using light that has passed through a photographic lens system including interchangeable lenses 1 to 4. In this case, distance measurement can be performed when each lens reaches the position indicated by the broken line 10. Configure. It also works in conjunction with the rotation of the lens stand 6, so that, for example, when it is necessary to use the lens 2, the lens 2
It is also possible to employ a distance measuring mechanism that generates a focusing signal at a convenient timing to stop the camera at the broken line 10, and to operate the electromagnet 18 in response to this focusing signal. FIG. 2 is a diagram showing an example of a lens drive mechanism when three-point zone focusing is adopted. Of course, in the case of three-point zone focusing, three lenses may be used in a configuration similar to that shown in FIG.
is arranged so as to be rotatable around the shaft 35, and this is the neutral position,
That is, when the lens 32 is in the position shown in the figure, the optical axis of the lens 32 is aligned with that of another photographic lens system to constitute a photographic lens system,
When the lens stand 34 is rotated left and right from this position, the lenses 31 and 33 come to the position of the photographing lens system, that is, the position of the lens 32 in the figure. For this purpose, if the position to rotate left and right is determined by stopper pins 36 and 37, and if the lens stand 34 is supported by a spring (not shown) so that it is normally in a neutral position, the lens 31 or 33 can be moved. When in use, the lens stand can be pulled using a means such as an electromagnetic plunger, and the structure is simple, the response speed is fast, and the mechanical shock can be reduced. In this embodiment, two plungers 38 and 39 are arranged, and a control circuit 40 is configured to energize plunger 38 when lens 33 is used and plunger 39 when lens 31 is used.
controlled by. Note that the springs 41 and 42 are attached to the lens stand 34.
It is inserted for the purpose of buffering between the plunger and the plungers 38 and 39. FIG. 3 shows another embodiment of the present invention. In the above-mentioned example, a fan-shaped lens stand was used to move the lens to be replaced in a plane perpendicular to the optical axis, but in this embodiment, the photographic lens system The interchangeable lens 5 is arranged around an axis 53 perpendicular to the optical axis 52 of the lens 51.
4, 55, and 56 are designed to rotate.

Therefore, the lens stand 57 has the shape of a polygonal prism (hexagonal prism in this embodiment) vertically divided in half with the rotation axis 53 as the central axis. 3A shows the mode of shooting at a medium distance, and FIG. 3B shows the mode of shooting at a short distance.
4, a light image is formed on the film surface 58. Although means for driving the rotation of these lenses 54 to 56 is not particularly shown, a mechanism similar to that of each of the above-described embodiments may be employed. Note that the present invention is not limited to the embodiments described above, and various modifications are possible. The interchangeable lens used for focus adjustment is not necessarily the last lens in the photographic lens system. Furthermore, instead of using one lens as an interchangeable lens, a plurality of lenses may be interchanged. Furthermore, various modifications can be made to the method of exchanging lenses, and various shapes and driving methods of the lens stand can also be considered. According to the present invention, the lens driving mechanism is simplified, and since multiple different lenses are used by switching instead of moving the same lens in the optical axis direction, the degree of freedom of the optical system is large, and zone focusing is achieved. A suitable lens can be selected.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of one embodiment of the focusing device according to the present invention, FIG. 2 is a diagram showing another embodiment of the present invention, and FIGS. A diagram showing an example is provided. 1, 2, 3, 4...Interchangeable lens, 6...Lens stand, 10...Photographing lens system position, 11...
...Switch pieces, 12, 13, 14, 15...
Luns stand position detection electrode, 16... Distance measuring device, 17
...Control circuit, 18...Electromagnet, 19.
...Stopper, 21, 22, 23...Claw, 2
4. Stopper pin, 31, 32, 33...
Interchangeable lens, 34... Luns stand, 38, 39...
...Plunger, 41, 42...Spring, 51...
...Taking lens system, 52...Taking lens system optical axis, 54, 55, 56...Interchangeable lens, 58...
···film.

Claims (1)

[Claims] 1. In a device that performs automatic focus adjustment using a zone focus method, in order to have the lens system have different focal lengths corresponding to each zone, lenses with multiple different focal lengths are prepared as part of the lens system. , configured so that any of these can be selectively inserted into the optical path at high speed,
An automatic focus adjustment device characterized by being provided with a drive device that switches to an optimal lens based on a signal from a distance measuring device.