JPS5944611B2 - Zoom lens structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a zoom lens used as an interchangeable lens for a single-lens reflex camera having a TTL aperture metering type exposure meter.

In conventionally known zoom lenses, the aperture aperture is generally constant. However, some lenses have apertures that change over part or the entire zoom range. When such a zoom lens is combined with a TTL aperture metering type exposure meter, it becomes necessary to correct the exposure value in accordance with changes in focal length and aperture aperture. Also, depending on the position of the light receiving element, errors in the amount of light incident on the light receiving element due to vignetting of the optical path, etc., especially in cameras where the light receiving element is placed around a pentaprism, can also affect the focal length of the lens. It changes depending on the diaphragm aperture, and it is necessary to consider correction of these errors.

An object of the present invention is to provide an interchangeable lens structure capable of performing the above-mentioned correction in a zoom lens whose aperture aperture is changed in accordance with zoom operation. Corrects the aperture aperture or aperture ratio according to the zoom operation using an aperture correction means such as an aperture unit or preset device, inputs the corrected information or aperture value information from the lens side to the camera side, and inputs it to the exposure meter. In order to serve as a correction means, a signal means representing the information is provided in the zoom lens structure, and the exposure calculation is corrected.

Embodiments of the present invention will be described below with reference to the drawings.

In the figure, 1 is a lens barrel fixing part, 2 is a tightening ring for fixing the lens barrel to the camera body, and 3 is a sliding guide tube integrally connected to the fixing part 1 for the first lens group I and the lens barrel. The movable barrels 4 and 5 that hold the second lens group (2) are slidably fitted inside the movable barrels 4, 5.

The guide tube 3 has linear guide grooves 3a and 3b as is known,
The keys 6 and T provided on each movable tube are inserted into the keys 6 and 6, respectively.
, 7 are fitted into cam grooves Ila and Ilb provided in a cam cylinder 11 integrated with the zoom operation ring 10,
By rotating the operation ring 10, the movable barrels 4 and 5 are slid back and forth within the guide barrel 3, thereby adjusting the focal length. S
The first lens group I is held by a holding frame 12, which is screwed into the movable tube by a helicoid screw 12a provided on its outer periphery, and has a pin 15 fixed at its front end.
is fitted into the straight groove 14a of the distance operation ring 14, and the operation ring 1
By the rotation of the helicoid 4, the helicoid 0 moves back and forth within the movable cylinder 4 by the action of the screws 4a and 12a, and focusing is performed.

The distance operation ring 14 is a cylindrical member 16 fixed to the sliding guide cylinder 3.
It is screwed together and held rotatably.

The second lens group ■ has a frame 155a with the aperture unit 17 in between.
, 5b, and is configured to be able to slide back and forth within the sliding guide cylinder 3 integrally with the aperture unit 17 and preset cam 18.

The diaphragm unit 17 has a known structure in which the diaphragm blades are held between a retaining ring 5 fixed to the frame 5 and an operating ring 17a that is rotatable relative to the holding ring 5, and has a preset blade rotatably held in the frame 5. A bell crank lever 19, which has a pin 19a that engages with the cam portion 18a of the cam ring 18 and a pin 19b that acts as a stopper on the engaging portion 17b of the operating ring 17a, is pivotally connected to the frame 5 by a shaft 19c, and the lever 19 is pivotally connected to the frame 5 by a shaft 19c. 17a is biased in the narrowing direction by a weak spring 20 that is engaged with a pin 17d implanted thereon. Reference numeral 21 denotes a preset member integrally connected to the diaphragm operation ring 22, which is supported within the lens barrel so as to be rotatable around the optical axis.
It has a cam groove 21b as shown in the figure, and a pin 18b fixed to the arm 18c of the preset cam ring 18 is fitted into the cam groove.

A rearwardly extending arm 21c of the preset ring 21 engages with an exposure meter provided within the camera. The aperture operating ring 22 has a click stop mechanism between it and the lens barrel fixing portion, and rests at the set position against the force of the spring 20.

Reference numeral 23 denotes an interlocking member for interlocking the diaphragm operating ring 17a, the diaphragm on the camera side, and the drive lever.It is supported so as to be rotatable around the optical axis, and an arm 23a extending forward is connected to the protrusion 17c of the diaphragm operating ring 17a. The actuating ring 17a is normally held in the fully open aperture position against the spring 20 by being engaged and biased by the strong spring 24.

An arm 23b extending rearward from the member 23 is provided so as to be able to engage with an aperture drive lever (not shown) on the camera side. A cam surface 23c as shown in FIG. 4 is formed on the engagement surface of the arm 23a of the interlocking member 23 with the operating ring 17. As shown in FIG.

In FIG. 5, a cam plate 26 is attached to the cam cylinder 11 via a connecting rod 25 so that it can rotate integrally with the zoom operation ring 10.

Reference numeral 27 denotes a correction pin supported slidably in the optical axis direction at the rear end of the lens barrel, and is biased by a spring 28 so that its tip always engages with the cam surface 26a of the cam plate 26. It protrudes from the rear end of the lens barrel and engages with the exposure meter on the camera side.

When the zoom operation ring 10 is rotated in a zoom lens structure configured as described above, the cam barrel 11 rotates integrally and is moved by its cam grooves 11a, 11b and pins 8, 9. The tubes 4 and 5 each move linearly within the sliding guide tube 3, and a zooming effect is performed by adjusting the focal length.

At this time, the diaphragm unit 7 moves together with the lens support frame 5b, and the protrusion 17c of the diaphragm operating ring 17a rotates along the cam surface 23c of the arm 23a of the interlocking ring, so the diaphragm blades operate and the diaphragm changes when the aperture is opened. The aperture is regulated according to zooming, and the amount of light incident on a light-receiving element (not shown) changes, and accordingly, the deflection of the meter pointer of the exposure meter also changes. At this time, the preset cam ring 18 also moves together with the movable cylinder 5, and its arm 18c
Since the upper pin 18b rotates along the cam groove 21b of the arm 21a of the preset ring, the cam surface 18a of the cam ring
The bell crank lever 19 is
rotates, and the position of the pin 19b relative to the protrusion 17c of the aperture operating ring 17a is corrected in accordance with changes in the aperture diameter due to the abutment between the aperture operating ring 17a and the pin 19b. When the aperture operation ring 22 is rotated in this state, the preset member 21 rotates as a unit, and the arm 21c transmits the rotation to the exposure meter in the camera, and the preset cam ring 18 is transmitted via the cam groove 21b and the pin 18b. The appropriate aperture value is preset according to the exposure meter's instructions. Next, in conjunction with the shutter release operation of the camera, the aperture drive lever pushes the arm 23b of the interlocking ring 23 against the spring 24 and moves it a certain amount, and the aperture operation ring 17a is pulled by the spring 20 and moves in the aperture direction. The aperture diameter is determined at the position where the engaging portion 17b contacts the pin 19b. The signal means 27 shown in FIG. 5 changes the aperture opening aperture as described above and corrects the preset position accordingly by rotating the zoom operation ring 10, and also by rotating the cam plate 26. The signal means 27 in contact with this moves in the optical axis direction. The cam surface 26a is designed so that the amount of protrusion of the signal means 27 changes in accordance with the error in the amount of light received by the light receiving element depending on the open aperture. When the aperture operation ring is operated, an appropriate aperture value is preset with the light reception error corrected.

As described above, in the present invention, when the zoom lens is zoomed, the aperture device inside the zoom lens moves along the optical axis, and the aperture aperture or aperture ratio changes, and the maximum aperture on the lens side is inputted to the exposure meter on the camera side. When correcting value information, the signal means 27 provided at the rear end of the lens barrel is configured to be movable along the optical axis in response to a zooming operation, and the amount of movement L1 to L2 of the signal means 27 is adjusted by the amount of movement L1 to L2 on the cam plate. The aperture value is changed according to zooming by the cam 26a of 26, and the signal means 27 is linked to an exposure meter on the camera side (not shown) to transmit information on the aperture value on the lens side. information can be reliably transmitted to the camera side.

[Brief explanation of the drawing]

1 to 5 show embodiments of the present invention. FIG. 1 is a cross-sectional view of a main part of a lens structure according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line A-X in FIG. The figure is a developed view of FIG. 2 taken along line B, FIG. 4 is a developed view taken along line C-C' of FIG. 2, and FIG. , 6th
The figure is a perspective view of the cam plate of FIG. 5. 1... Lens barrel fixed part, 2... Tightening ring, 3... Sliding guide tube, 4, 5... Moving tube, 10... ...Zoom operation ring, 11...
Cam tube, 12... Luns holding frame, 14...
・Distance operation ring, 17... Aperture unit, 18.
...Preset cam, 21 ... Preset member, 22 ... Aperture operation ring, 23 ...
・Interlocking member, 26...Cam plate, 27...
・Signal means, I...First lens group,...
-Second lens group.

Claims (1)

[Claims] 1. A movable signal means is provided at the rear end of the lens barrel, and the amount of movement of the signal means is changed in accordance with a zooming operation to transmit a correction signal of exposure information of an aperture device due to zooming to the attached side. A zoom lens structure characterized by being configured as follows.