JPH05249358A - Lens barrel - Google Patents

Abstract

PURPOSE:To miniaturize the lens barrel and to reduce the cost thereof by preventing reflected light which is the cause of ghost. CONSTITUTION:This lens barrel is provided with a first guiding member 30 guiding a lens frame 20 holding a lens 10 in an optical axis direction, a second guiding member 40 preventing the lens holding frame 20 from rotating with a center at the first guiding member 30 in a direction crossing at a right angle with the optical axis, a belt-like member 70 disposed on a place which is closer to an optical axis side than the second guiding member 40 in parallel with the guiding member, and having the performance of low reflectance process 70a in an inside surface, and having the performance of an encoder pattern 70b for detecting the moving position of the lens holding frame 20 on an outside surface opposed to the second guiding member 40, and a position detecting parts provided on the lens frame 20 in a state where it is brought into contact with the surface of the encoder pattern.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens barrel used in optical equipment such as video cameras.

[0002]

2. Description of the Related Art In recent years, a lens barrel of this type has a guide bar, which is arranged parallel to the optical axis direction, provided with a lens holding frame for a focus adjusting lens and a zoom adjusting lens. A bar system, which supports the shaft so that it can move in the axial direction, is often used. FIG. 6 is a perspective view showing a lens barrel adopting the bar system, which moves through the lens frame 20 holding the lens 10 and the sleeve 20a of the lens frame 20 in the optical axis direction. First to guide
A guide bar 30 as a guide bar and a second guide bar engaged with the concave portion 20b of the lens frame 20 so as to prevent the lens frame 20 from rotating around the guide bar 30 in the direction orthogonal to the optical axis. The U-bar 40 and the potentiometer 90 for detecting the position of the lens frame 20.

[0003]

However, in the above-mentioned conventional example, the high-luminance light outside the designed light flux is reflected by the surface inside the lens barrel, and the reflected light reaches the image forming surface and causes a ghost. Was there. To remove or reduce this ghost, it is relatively easy to reduce the reflectance of the inner surface of the lens barrel. However, in order to reduce the reflectance of the bar that holds the lens frame and guides the movement of the lens frame in the optical axis direction, roughening the surface of the bar makes it possible to move the lens frame smoothly in the optical axis direction. There was a problem that it could not be done.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to obtain a lens barrel which is capable of miniaturization by preventing reflected light which causes ghost.

[0005]

According to the present invention, there is provided a first guide member for guiding the lens frame holding the lens in the optical axis direction, and the lens holding frame is provided with the first guide member as a center. A second guide member for preventing rotation in a direction orthogonal to the axis, and an optical axis side of the second guide member which is arranged parallel to the guide member and whose inner surface is processed to have a low reflectance,
A strip-shaped member having an encoder pattern for detecting the moving position of the lens holding frame provided on the outer surface facing the second guide member, and a position detecting component provided on the lens frame so as to contact the encoder pattern surface. By having
In addition to preventing reflection from the guide bar, it is possible to reduce the size by incorporating a position detection device that was conventionally mounted outside the lens frame.

[0006]

1 to 4 show an embodiment of the present invention, and FIGS. 1 to 4 are drawings which best show the features of the present invention, in which a lens 10 is held by a lens frame 20. The lens frame 20 includes an arm portion 20-1 having a sleeve 20a on one side.
Is provided with an arm portion 20-2 having a notch recess 20b on the other side. The lens frame 20 is attached to the sleeve 20a.
A guide bar 30 is inserted as a first guide member for guiding the lens so that it can move in the optical axis direction, and the lens frame rotates in the direction orthogonal to the optical axis around the guide bar 30 in the notch recess 20b. Second to prevent
The U bar 40 as a guide member is engaged.

A band-shaped member 70 disposed in parallel with the U-bar 40 is provided in a recess 20c formed in the base of the arm 20-2 of the lens frame 20 at a right angle to the cutout recess 20b. Engaged. The belt-shaped member 70 is, for example, an antireflection tape, the inner surface of which is subjected to a low-reflectance treatment 70a such as flocking, and the outer surface of which faces the U-bar 40 moves the lens frame 20 as shown in FIG. An encoder pattern 70b is provided so that the position can be detected.
Further, the lens frame 20 is provided with a brush 80 as a position detecting component which is in contact with the encoder pattern 70b and reads the encoder pattern information to detect the position.

The bottom surface of the recess 20c with which the belt-shaped member 70 engages is shown in FIG.
It is formed in a convex arc shape as shown in FIG. Further, as shown in FIG. 4, the bottom surface is formed in a U shape when viewed from the cross-sectional direction of the belt-shaped member 70, and the belt-shaped member 70 can be engaged so as not to shift in the width direction. ..

With the above structure, a part of the light beam entering the lens barrel and traveling toward the U bar 40 is absorbed by the low-reflectance treated surface 70a of the belt-shaped member 70, and unnecessary reflection does not occur. Therefore, the occurrence of ghost is small. Then, when a driving force (not shown) is applied to the lens frame 20 in the optical axis direction, the lens frame 20 moves in the optical axis direction using the guide bar 30 and the U bar 40 as guides.

Due to this movement, the contact position of the brush 80 with the encoder pattern 70b changes, and as a result, the read information from the encoder pattern 70b changes and the moving position of the lens frame 20 can be detected.

[0011]

As described above, according to the present invention,
Since a strip-shaped member having a low-reflectance processed inner surface is provided in parallel with the bar for guiding the movement of the lens frame in the optical axis direction, unnecessary reflection light is reduced and ghosts caused by the reflection light are provided. Can be significantly reduced. Also, since the encoder pattern for position detection is provided on the surface of the belt-shaped member opposite to the low-reflectance processed surface, it is possible to eliminate the conventional position detection device externally attached to the lens frame and reduce the cost increase by adding the belt-shaped member. In addition to the above, there is an effect that the size can be reduced.

[Brief description of drawings]

FIG. 1 is a perspective view of a lens barrel showing an embodiment of the present invention.

FIG. 2 is a front view of a main part showing an embodiment of the present invention.

3 is a vertical cross-sectional view taken along the line AA of FIG.

FIG. 4 is a front view of FIG. 2 with a brush removed.

FIG. 5 is a front view of a belt-shaped member showing an encoder pattern.

FIG. 6 is a perspective view of a conventional lens barrel.

[Explanation of symbols]

 10 lens 20 lens frame 30 first guide member 40 second guide member 70 strip-shaped member 70a encoder pattern

Claims (1)

[Claims] 1. A first guide member for guiding a lens frame holding a lens in an optical axis direction, and preventing the lens holding frame from rotating around the first guide member in a direction orthogonal to the optical axis. And a second guide member which is disposed on the optical axis side of the second guide member in parallel with the guide member and whose inner surface is processed to have a low reflectance, and the outer surface facing the second guide member is A lens barrel comprising: a belt-shaped member provided with an encoder pattern for detecting a moving position of a lens holding frame; and a position detecting component provided on the lens frame so as to be in contact with the encoder pattern surface.