JP3330725B2 - Rear converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear converter comprising an afocal lens system which is mounted between a lens mounting portion of a camera body and a detachable photographing lens and converts the focal length of the photographing lens.

[0002]

2. Description of the Related Art Conventionally, a rear converter of this type has a lens extension means using a helicoid for focusing on the photographing lens side and a lens extension means on the camera body side, such as a 35 mm single-lens reflex camera. In general, it is used in cameras that do not have a camera, and is mounted between the camera body and the photographing lens to convert the focal length of the photographing lens to 1.4 times to 2 times. With almost no loss of performance, the shortest shooting distance was almost the same, and it was possible to double the shooting magnification during close-up shooting.

FIG. 5 is a configuration diagram schematically showing the entire configuration of a 35 mm single-lens reflex camera when a photographing lens 3 of a telephoto type is mounted on a camera body 1 via a rear converter 2. In such a configuration, the photographing lens 3
The entire lens system or the lens system involved in focus adjustment moves back and forth with respect to the film surface F by a well-known helicoid mechanism linked to the rotation of the focus adjustment ring 3a, and the distance between the rear converter 2 and the film surface F is It is kept constant.

[0004] Here, the film surface F is the rear converter 2
Assuming that a point that intersects with the optical axis A of the photographing lens 3 is P1 and a conjugate point of the point P1 through the rear converter 2 is P2, the point P2 is fixed to the camera body 1 because the rear converter 2 is fixed to the camera body 1. It will be a fixed point. Therefore, the rear converter 2 is set so that the focal point of only the photographing lens 3 is at the point P2.
By setting the distance between the front and rear mounting surfaces, shooting becomes possible. At this time, if the amount of extension of the photographing lens 3 is constant, the shortest photographing distance becomes substantially the same regardless of the presence or absence of the rear converter 2.

[0005]

However, such a conventional rear converter is mounted on a camera having a lens extension mechanism such as a rack and pinion on the camera body side and no extension mechanism on the photographing lens side. When mounted on a unit, the focal length of the photographing lens increases by the magnification of the rear converter, but at the same time, the shortest photographing distance also significantly increases, and there is a problem that close-up photography becomes impossible. The reason will be described below.

FIG. 6 shows an object point P by a general lens L1.
FIG. 4 is an optical path diagram showing a relationship between the image point 3 and an image point P4. Now
If the front focus of the lens L1 having the focal length f is F1, the rear focus is F2, the distance from the front focus F1 to the object point P3 is x, and the distance from the rear focus F2 to the image point P4 is x ', x
The relational expression x '= f ² holds. Where Δ is the lens L
Of the main surface. Here, when the camera distance x 'corresponds to the feeding amount of the lens L1, corresponds to approximately the object distance is the distance x When ^{x»f, x = f 2 / x} ' becomes.

If a rear converter is added to the lens L1 to double the focal length, the lens L1 is
And the rear converter are integrated, and the feed is performed by the feed amount x ′ set on the camera body side, x = (2f) ²
/ X becomes a '= 4f ² / x'. That is, assuming that the extension amount x 'of the lens L1 is constant, the addition of the rear converter makes the shooting distance x four times as large as that without the rear converter.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and provides a camera which adjusts the focus by moving a lens mounting portion back and forth with respect to a film surface even when a rear converter is mounted. The purpose is to prevent extension.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a camera for adjusting focus by moving a lens mounting portion of a camera body to which a taking lens can be attached and detached back and forth with respect to a film surface. A rear converter that is mounted between the photographic lens and the lens mounting portion to convert the focal length of the photographic lens, wherein a lens system is moved from the film surface to a predetermined position regardless of the movement of the lens mounting portion. To provide a rear converter provided with a lens system fixing means capable of holding the lens system at a distance of.

A lens mounting portion of a camera body to which a photographing lens can be attached and detached is mounted between the photographing lens and the lens mounting portion of a camera which performs focus adjustment by moving the lens forward and backward with respect to a film surface. A lens outer cylinder, one end of which is detachably attached to a lens mounting portion of the camera body and the other end of which is detachably attachable to the photographing lens; A guide member for slidably and freely fitting a lens barrel holding the lens system therein and a lens system fixing capable of holding the lens system at a predetermined distance from the film surface via the lens barrel A rear converter provided with the means is also provided.

Then, in the above rear converter,
A lens system fixing means is radially protruded from the lens barrel, is inserted through a slit formed in the guide member and the lens outer cylinder, and protrudes to the outside. One end is fixed to the connection shaft and the other end is the camera body. And a connecting plate fixed to the connecting member.

[0012]

The rear converter according to the present invention is constructed as described above, so that the lens system of the rear converter remains stopped irrespective of the movement even if the lens mounting portion is extended with the taking lens for focus adjustment. Therefore, the shortest photographing distance is almost equal to the shortest photographing distance of the photographing lens when the rear converter is not attached, and close-up photography is possible.

In the case where a lens barrel holding a lens system is slidably and loosely fitted in a guide member integrated with a lens barrel of a rear converter, the guide member moves with the movement of the lens mounting portion. Even so, the lens barrel can slide on the guide member and stay at a predetermined position.

In the above rear converter,
A connection shaft projecting the lens system fixing means to the lens barrel,
By using a connecting plate for connecting the connecting shaft and the camera body fixing portion, the lens system of the rear converter can be fixed at a predetermined position with a very simple configuration.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a plan sectional view showing a state in which a rear converter according to one embodiment of the present invention is mounted between a lens mounting portion of a camera body and a taking lens, and the lens mounting portion is retracted. FIG. FIG. 3 is a side sectional view showing a state in which the lens mounting portion is extended, and FIG.

First, referring to FIG. 3, an outline of a camera equipped with a rear converter 12 according to the present invention, particularly a focus adjusting mechanism thereof, will be described. This camera 10 is 6 × 7c
This is a lens shutter type single-lens reflex camera having an m-size lens and a replaceable film back, which includes a camera body 11, a replaceable photographing lens 13, and a film back 14. The film back 14 is rotated by 90 degrees by a revolving adapter 15. , It is possible to immediately switch the vertical and horizontal directions of the screen.

The camera body 11 has a mirror, a light shielding plate (both not shown) and its charging mechanism, a lens shutter charging mechanism in the taking lens 13, a winding mechanism for the film back 14, and the like inside. Is provided with a charge lever 16 (see FIG. 4). The camera body 11 and the lens mounting portion 17 are connected via an elastic bellows 18, and include a rack 19 fixed to both sides of the lens mounting portion 17 and a pinion 20 rotatably supported by the camera body 11. By rotating a focus adjustment knob 21 integrated with the pinion 20, the lens mounting portion 17 can be moved back and forth to perform focus adjustment.

As shown in FIG. 4, the photographing lens 13 has an operating plate 13a on the back side for charging and releasing a lens shutter 13d (see FIG. 1) by rotating in both forward and reverse directions by a predetermined angle. A pair of connecting pins 13b, 13b protrude rearward from the plate 13a. When the photographing lens is mounted, the connecting pins 13b, 13b are used for a pair of through holes 22 of the rotary drive plate 22 of the lens mounting portion 17 on the camera body 11 side.
a and 22a to charge and release the shutter from the camera body 11 side. Each photographing lens 13 is provided with a tightening ring 13c provided with a bayonet portion at the rear end so as to be rotatable by a predetermined angle, and while the photographing lens 13 is kept in a non-rotating state, a bayonet portion fixed to the lens mounting portion 17 side is provided. It can be fixed.

As shown in FIG. 1, the rear converter 12 mounted between the lens mounting portion 17 on the camera body 11 side of the camera 10 having the above-described structure and the photographing lens 13 holds the lens system L. Lens barrel 23, a guide cylinder 24 which is a guide member for slidably housing the lens barrel 23, and a free-rotatably loose fit on the outer periphery of the guide cylinder 24 via a pair of ball bearings 25, 25. Charge cylinder 2
6 and a lens outer cylinder 27 surrounding these.

The lens barrel 23 is provided with a pair of connecting shafts 28, 28 as a pair of columnar members projecting in a radial direction, and a pair of slits 24a, 24a formed in the guide barrel 24, and a charge barrel 26.
And a pair of slits 27a, 27a formed in the lens outer cylinder 27 are respectively inserted through the pair of openings 26a, 26a formed in the lens outer cylinder 27 so as to project outside the lens outer cylinder 27. Then, the connecting plates 29, 29 are fixed with four set screws 30 between the distal end portions of the connecting shafts 28, 28 and the fixing portions on the left and right side surfaces of the camera body 11, thereby fixing the lens system of the rear converter 12. Configure means.

Flanges 26b and 26c are formed at both ends of the charge cylinder 26, and through holes 26 into which the connecting pins 13b and 13b of the photographing lens 13 are fitted into the flanges 26b.
and d, 26d, and a pair of connecting pins 26e, 26e that can be fitted into the through holes 22a, 22a of the rotary drive plate 22 of the lens mounting portion 17 protrude from the flange 26c.

Further, a fixed bayonet portion 27b to which the tightening ring 13c of the photographing lens 13 can be bayonet-coupled is formed at the front end of the lens outer cylinder 27, and bayonet can be connected to the fixed bayonet portion 17a of the lens mounting portion 17 at the rear end. A simple tightening ring 27c is provided to be rotatable by a predetermined angle.

This embodiment is configured as described above.
1, the lens barrel 23 of the rear converter 12 is located near the tip of the guide barrel 24, and the lens system L is close to the lens system L1 of the photographing lens 13. , The subject at infinity is in focus.

In this state, when the focus adjusting knob 21 is rotated and the lens mounting portion 17 is extended by the rack and pinion mechanism, the guide tube 24, the charging tube 26, and the lens outer tube 27 of the rear converter 12 are shown together with the lens mounting portion 17. It is paid out to the left. However, since the lens barrel 23 is connected to the camera body 11 via the connection shaft 28 and the connection plate 29, the guide barrel 24 slides on the outer peripheral surface of the lens barrel 23 and the lens system L is stopped. , And only the taking lens 13 integrated with the lens mounting portion 17 is extended through the lens barrel 27 to focus on a short-distance subject.

When the lens mounting portion 17 is fully extended to the state shown in FIG. 2, the lens barrel 23 is located near the rear end of the guide tube 24, and the lens system L is separated from the lens system L1 of the photographing lens 13. It is in the position that I did. In this state, the shortest photographing distance is almost equal to the shortest photographing distance when the photographing lens 13 is used alone, and close-up photography in which the photographing magnification is increased by the ratio of the focal length becomes possible.

When the charge lever 16 of the camera body 11 is pushed in regardless of the position of the lens mounting portion 17, the rotation driving plate 22 of the lens mounting portion 17 rotates in a predetermined direction, and the image is taken via the charging cylinder 24. The operation plate 13a of the lens 13 is rotated to charge the lens shutter 13d of the photographing lens 13, and the light-shielding plate and the mirror are lowered to shield the film surface, and then the aperture and shutter blades of the lens shutter are opened. .

When the release button 31 (FIG. 3) provided on the lower part of the camera body 11 is pressed in this state, the rotation driving plate 22 of the lens mounting portion 17 rotates in the opposite direction, and the image is taken via the charge cylinder 24. The operating plate 13a on the lens 13 side reverses and raises the mirror, closes the shutter blade halfway, then raises the light blocking plate and narrows the aperture to a predetermined value, and then opens and closes the shutter blade for a predetermined time. Exposure is performed.

In the above embodiment, the case where the lens barrel of the rear converter is freely slidably fitted in the guide barrel has been described. However, the lens barrel and the guide barrel are helicoid-coupled to each other, and the rotation thereof is performed. The side helicoid is made to move together with the rotating member separately provided on the lens mounting part,
The rotating member may be linked to the rotation of a pinion integrated with the focus adjustment knob. At this time, the rotating helicoid may be either the lens barrel side or the guide barrel side, and the other is straight.

When the focus adjustment knob is rotated and the lens mounting portion is advanced by the rack and pinion mechanism in such a configuration, the rotating member in the lens mounting portion rotates in conjunction with the rotation of the pinion, and rotates on the rotation side of the rear converter. The lens barrel is moved in the optical axis direction by rotating the helicoid. Therefore, by appropriately setting the screw direction, rotation angle, lead, and the like of the helicoid, the lens barrel is moved in the opposite direction by the same amount as the amount of movement of the lens mounting portion. It can be kept stationary with respect to the body.

Further, if this lens system fixing means is applied to a camera of a type in which the lens mounting portion is moved between the lens mounting portion and the camera body via a helicoid mechanism instead of a rack and pinion mechanism, the rear converter can be used. The lens system fixing means can be configured more simply.

Further, in the above-described embodiment, a case has been described in which the present invention is applied to a single-lens reflex camera which mechanically charges a lens shutter in a photographic lens from the camera body side, but a motor for driving a lens shutter is provided on the photographic lens side. It is also possible to implement the present invention in a camera that operates a lens shutter in response to a signal from the camera main body or a camera that does not have a lens shutter on the taking lens side and has a focal plane shutter on the camera main body side,
In this case, there is no need to provide a charge cylinder in the rear converter, and the configuration can be further simplified.

[0032]

As described above, in the rear converter according to the present invention, the lens system of the rear converter, which is mounted on the camera for adjusting the focus by moving the lens mounting portion back and forth with respect to the camera body, from the film surface. As the fixed distance is fixed, the shortest shooting distance when the lens mount is extended can be made almost equal to the shortest shooting distance when the shooting lens is used alone. Become.

In the case where the lens barrel of the rear converter is slidably and loosely fitted in a guide barrel integrated with the lens barrel, the lens barrel can be moved even if the lens mounting part is moved for focus adjustment. The lens barrel slides on the guide member and can be kept stationary.

Further, in the above rear converter,
A lens system fixing means, a connecting shaft protruding from the lens barrel,
By using this connecting shaft and a connecting plate that connects the camera body fixing part, the lens system of the rear converter can be fixed at a predetermined position with a very simple configuration regardless of the movement of the lens mounting part. become.

[Brief description of the drawings]

FIG. 1 is a plan sectional view showing a state where a rear converter according to an embodiment of the present invention is mounted between a lens mounting portion of a camera body and a taking lens, and the lens mounting portion is retracted.

FIG. 2 is a plan sectional view showing a state where the lens mounting portion is extended.

FIG. 3 is a side view showing a state where the lens mounting portion is extended.

FIG. 4 is a perspective view showing a camera body, a lens mounting portion, and a connecting portion of a taking lens of the camera embodying the present invention;

FIG. 5 is a side view showing a state where a conventional rear converter is mounted between a camera body and a photographing lens.

FIG. 6 is an optical path diagram for explaining the principle of the present invention.

[Explanation of symbols]

 10: Camera 11: Camera Body 12: Rear Converter 13: Photographic Lens 17: Lens Mounting Part 18: Bellows 19: Rack 20: Pinion 21: Focus Adjustment Knob 23: Lens Barrel 24: Guide Tube 26: Charge Tube 27: Lens Outer cylinder 28: Connecting shaft 29: Connecting plate L: Lens system

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-161326 (JP, A) JP-A-62-194243 (JP, A) JP-A-52-38923 (JP, A) JP-A-63-194 115118 (JP, A) JP-A-4-369978 (JP, A) JP-A-4-6011 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03B 17/14 G02B 15 / 10 G03B 17/56 G02B 7/02-7/08

Claims (3)

(57) [Claims] 1. A lens mounting portion of a camera body to which a photographing lens is detachable is mounted between the photographing lens and the lens mounting portion of a camera which performs focus adjustment by moving the lens body back and forth with respect to a film surface. A rear converter for converting the focal length of the photographing lens, wherein lens system fixing means capable of holding a lens system at a predetermined distance from the film surface regardless of movement of the lens mounting portion is provided. Features a rear converter. 2. A lens mounting portion of a camera body to which a photographing lens is detachable is mounted between the photographing lens and the lens mounting portion of a camera for performing focus adjustment by moving the lens mounting portion back and forth with respect to a film surface. A rear converter for converting the focal length of the photographing lens, one end of which is detachable from a lens mounting portion of the camera body,
The other end has a lens barrel in which the photographing lens can be attached and detached, a guide member slidably and loosely fitted with a lens barrel holding a lens system inside the lens barrel integrally with the lens barrel, and the lens barrel. And a lens system fixing means for holding the lens system at a predetermined distance from the film surface via the lens converter. 3. A connecting shaft, wherein the lens system fixing means radially protrudes from the lens barrel, extends through a guide member and a slit formed in the lens barrel, and protrudes to the outside. One end is fixed to the connecting shaft. 3. The rear converter according to claim 2, wherein the other end comprises a connecting plate fixed to the camera body.