JPS6292905A - Lens focusing device - Google Patents

Abstract

PURPOSE:To move a lens smoothly and finely by rotating a knob for fine adjustment to perform focusing when an inner lens barrel inserted to an outer lens barrel is rotated to perform focusing. CONSTITUTION:An inner lens barrel 2 is stored in a cavity of an outer lens barrel 1 so that the inner lens barrel 2 can be freely moved forward and backward and be rotated. Band-shaped projecting parts 2a and 2b rubbing on the inside peripheral wall of the cavity of the outer lens barrel 1 are formed in two positions in the front and the rear on the outside peripheral part of the inner lens barrel 2, and the outer lens barrel 1 and the inner lens barrel 2 are so finished that they are slid and rotated in a good fitting state. The first, the second, ... the seventh lenses L1, L2...L7 are set to the inner lens barrel 2 in order from the left. The 8th lens 8 is set to the rear part of the outer lens barrel 1, and the inner lens barrel 2 is rotated and slid and the air gap between the 7th lens L7 and the 8th lens L8 is adjusted to perform focusing.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a lens focusing device such as an enlarged projection lens used in a projection type television receiver or the like.

2. Description of the Related Art In recent years, so-called projection televisions, in which a large screen is obtained by enlarging and projecting images projected on a small picture tube onto a screen using a projection lens, have rapidly become popular. This projection television uses a large-sized, large-diameter projection lens in order to obtain a bright projection screen. In order to clearly form a projected image on a screen at a predetermined position, focusing adjustment is always necessary, and after adjustment, it must be securely fixed so that the focus does not shift easily.

FIG. 6 shows an example of a conventional focusing device. Reference numeral 21 denotes an outer lens barrel, and an inner lens barrel 22 is housed in the inner space of the outer lens barrel so as to be movable back and forth and rotatable.

Convex annular portions 22a are formed around the entire circumference at two locations on the front and back of the outer circumference of the inner barrel 22, and these convex portions slide into contact with the inner surface of the outer barrel cavity in an appropriate fit state. Inner tube 2
2 is configured to slide and rotate back and forth.

Further, the outer wall surface of the outer lens barrel 21 is provided with a cam hole 21a.

21b are formed at rotationally symmetrical positions spaced apart by 18o0. The cam displacement curves of the guide holes 21a and 21b are the same.

Reference numeral 23 denotes an operating lever that applies force when rotating the inner lens barrel 22, and extends through the cam hole 21a and projects to the outside. The operating lever 23 also serves as a cam follower shaft, and a portion of its diameter is in sliding contact with the wall surface of the cam hole 21a. Further, the operating lever 23 has a male screw threaded at its distal end for screwing it onto the endoscope barrel, and a male screw threaded portion for screwing the wing nut 24 at its upper part. After focus adjustment, the wing nut 24 and the outer wall of the outer barrel 21 clamp the outer wall of the outer barrel 21 to fix the inner barrel 22 so that it does not move. Further, on the opposite side of the operating lever 23, a cam follower shaft 26 that fits and slides into the cam hole 21b is implanted in the outer wall of the inner lens barrel 22.

To perform focusing adjustment, hold the operating lever 23 and apply rotational force to it to rotate the inner lens barrel. The cam follower shaft 25 has a cam hole 21a,
21b, the inner lens barrel 22 moves back and forth while rotating. Focusing adjustment is performed by moving the entire projection lens or a part of the lens group back and forth in this manner.

Problems to be Solved by the Invention In the conventional lens focusing device configured as described above, the inner lens barrel is rotated by applying force directly to the operating lever, so rough focusing adjustment is relatively easy. However, it is not suitable for fine adjustments that require fine and smooth movements. In addition, this type of large-diameter projection lens has a large diameter lens barrel and requires a considerable amount of force to rotate it. This is a major factor that makes it difficult to make fine adjustments. The present invention provides a lens focusing device that can easily and reliably perform fine focusing adjustments in such a large-diameter projection lens.

Means for Solving the Problems In order to solve the above-mentioned problems, the lens focusing device of the present invention rotates the inner barrel by directly applying force to the operating shaft installed in the inner barrel. At the same time, a fine adjustment knob that rotates around this operating shaft is inserted, and the friction circumference formed on this fine adjustment knob is applied to the pressing surface formed on the outer periphery of the outer lens barrel. The lens is rotated while being pressed, and the frictional reaction force generated at this time moves the operating shaft and rotates the inner lens barrel to perform focusing adjustment.It provides an extremely smooth operating feel and allows for fine adjustments. can be easily done.

Function The present invention enables fine focusing adjustment of a large-diameter projection lens to be performed easily, accurately, and quickly.

As shown in the conventional example, in conventional focusing devices, focusing is performed by directly applying force to an operating shaft installed in the inner barrel to rotate the inner barrel. The outer barrel and inner barrel are fitted with extremely high precision to avoid any looseness. For this reason, a considerable amount of force is required to rotate the inner lens barrel, and fine adjustments that require smooth movement are extremely difficult due to repeated fine-grained forward and reverse rotations.

In the present invention, a fine adjustment knob that is rotatable about the operation shaft is inserted into the operation shaft implanted in the inner barrel, and a friction circumference formed on the fine adjustment knob is formed on the outer periphery of the outer barrel. When the fine adjustment knob is rotated while being pressed against the friction guide surface and moved along the friction guide surface, the operating shaft that supports the fine adjustment knob also moves in the same way, so the inner lens barrel The lens rotates and slides like a cam hole, allowing for focusing.

In this way, instead of directly applying rotational force to the inner lens barrel, the operating shaft is driven by the rotation of the fine adjustment knob. Focusing is done by rotating the fine adjustment knob, so it is easy to adjust the force and respond to subtle movements.The diameter of the fine adjustment knob is several times larger than the diameter of the operating shaft, so it has a deceleration effect, making it easy to operate. The fine adjustment knob can be rotated by force.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is an axial cross-sectional view of a projection lens employing an embodiment of the present invention. In the drawings, reference numeral 1 denotes an outer lens barrel, and an inner lens barrel 2 is housed in its cavity so as to be movable back and forth and rotatable. Belt-shaped protrusions 2a and 2b are formed at two locations on the front and back of the outer circumferential portion of the inner barrel 2, and are in sliding contact with the inner circumferential wall of the cavity of the outer barrel 1.
The outer barrel 1 and the inner barrel 2 are finished so that they slide and rotate in a well-fitted state. Now, on the left side, the inner lens barrel 2 is equipped with a seventh lens L1, a lens L2, a seventh lens L7. Further, an eighth lens L8 is attached to the rear part of the outer lens barrel 1. Focusing adjustment is performed by rotating and sliding the inner lens barrel 2, and adjusting the 7th lens L7 and the 8th lens L7.
This is done by adjusting the air spacing between 8 and 8.

FIG. 2 shows cam holes drilled in the outer wall surface of the outer lens barrel 1. A first cam hole 1a and a second cam hole 1b are bored at positions facing each other. .

The first and second cam holes 1a and 1b have the same cam displacement curve. Further, around the first cam hole 1a, a friction groove 3 is formed along the shape of the cam hole. The cross-sectional shape of this friction groove 3 is as shown in FIG. 1, and the peripheral wall of the groove is sloped outward. Note that the friction groove 3 is formed to be offset from the center of the cam hole, and therefore, from the center of the cam hole 1a to the side wall surface 3 of the friction groove 3.
a.

The dimensions up to 3b are different. This is so that the friction circumferential portion 4a of the fine adjustment knob 4, which will be described later, comes into contact with only one side of the side wall surface 3a, ab.

FIG. 3 is an enlarged detailed view of the vicinity of the fine adjustment knob 4. An operating shaft 6 is threaded onto the outer wall surface of the endoscope barrel 2. The operating shaft 6 has a large diameter part and a small diameter part, and is formed with a stepped part 5a. Then, the biasing spring 6 is inserted across the operating shaft, and one end thereof is held in contact with the stepped portion 6a. Furthermore, the fine adjustment knob 4 is inserted from behind the biasing spring 6 without compressing it, and the press-fitting rivet 7 is press-fitted into the rivet hole 5b formed in the operating shaft 5 to prevent it from being pulled out. The fine adjustment knob 4 is rotatable around the operating shaft 6 as a supporting shaft. As shown in FIG. 3, a biasing spring 6 is housed in a space formed by the operating shaft 6 and the fine adjustment knob 4. As shown in FIG.

The fine adjustment knob 4 is pushed upward by the restoring force of the constant biasing spring 6, and is maintained as shown in FIG. 3 in the normal state. Further, the large diameter portion of the operating shaft 6 is in sliding contact with the wall surface of the cam hole 1a, and also functions as a cam follower shaft. A cam follower shaft 8 is screwed onto the outer wall of the inner barrel 2 and is slidably engaged with the cam hole 1b.

Next, the operation of the lens focusing device configured as above will be explained.

To perform focusing adjustment, first turn the fine adjustment knob 4, apply a rotational force to it, and rotate the inner lens barrel 2. The operating shaft 5 and cam follower shaft 9 will slide along the cam hole, and The lens barrel 2 moves back and forth while rotating. In this way, coarse focusing adjustment is performed by directly applying rotational force to the operating shaft 6 and rotating the inner lens barrel, but it is extremely difficult to make fine adjustments using this method due to the reasons mentioned above. .

Now, in order to fine-adjust the focusing with this device, push in the fine-adjustment knob 4 so that the friction circumference 4a formed on the fine-adjustment knob 4 is connected to the friction groove 3 formed around the cam hole 1a.
is pressed against the side wall surface 3a.

FIG. 4 shows the state at this time. As described above, since the friction groove 3 is formed offset from the center of the cam hole 1d, the friction circumferential portion 4a only comes into contact with the side wall surface 3a. Now, when the fine adjustment knob 4 is rotated in this pressing state, the frictional force generated by the pressing contact is reduced, and the fine adjustment knob 4 is rotated.
moves on the side wall surface 3a just like a tire rolling. Therefore, the operating shaft that supports the fine adjustment knob 4 also
Naturally, it moves in exactly the same way as the fine adjustment knob 4, the inner lens barrel 2 rotates, and focusing adjustment is performed.

By rotating the fine adjustment knob 4 in the left and right directions while pressing it in this way, focusing can be adjusted quickly and easily without applying any force directly to the operating shaft 5. Further, the friction circumferential portion 4a and the side wall surface 3a may be processed with knurling or the like, or may be lined with an elastic material with a high friction coefficient such as rubber, or a rubber
If you use a method such as winding an elastic body such as a ring,
The force transmission relationship between the two becomes more reliable, and the focusing operation becomes easier.

As described in detail, according to the present invention, when performing focusing by rotating the inner lens barrel housed in the outer lens barrel,
Focusing adjustment is performed by rotating a fine adjustment knob, rather than by directly applying rotational force to the drive shaft installed in the inner lens barrel, which allows for light, clean, and fine movements. This provides the effect of quickly and accurately making fine adjustments to focusing.

[Brief explanation of drawings]

Fig. 1 is a detailed cross-sectional view of the vicinity of the lens focal length in an embodiment of the present invention, and Fig. 4 is a cross-sectional view showing the state when the fine adjustment knob is pushed in and the friction circumferential portion is pressed against the friction groove. , FIG. 5 is a sectional view of a projection lens using a conventional lens focusing device. 1... Outer barrel, 2... Inner barrel, 3...
...Friction groove, 4...Fine adjustment knob, 6...
...Operating axis, 6...Biasing spring, 7...
...Press-fit vent, 8...Cam follower shaft. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure revised l Figure 3 Figure 4

Claims (4)

[Claims] (1) A first lens barrel, a second lens barrel that can freely move back and forth and rotate inside the first lens barrel, a cam hole drilled in the outer wall surface of the first lens barrel, and a second lens barrel that a drive shaft that is embedded in the outer wall surface of the lens barrel and protrudes to the outside through the cam hole; a fine adjustment knob that is inserted into the drive shaft and is movable in the axial direction and rotatable about the drive shaft; , a friction circumferential portion formed at the lower end of the fine adjustment knob, and a friction wall surface provided along the cam hole, and when the fine adjustment knob is moved in the axial direction, the friction circumferential portion is The lens is pressed against the friction wall surface, and in this pressed state, the fine adjustment knob is rotated to transfer contact on the friction wall surface, and the reaction force of the friction force generated at this time moves the drive shaft to perform focusing. A lens focusing device characterized by: (2) The lens focusing device according to claim 1, wherein the friction circumferential portion and the friction wall surface are provided with uneven grooves such as knurling. (3) The lens focusing device according to claim 1, wherein the friction circumferential portion and the friction wall surface are lined with an elastic material having a high friction coefficient such as rubber. (4) Claim 1, characterized in that an elastic body such as a rubber ring is wound around a portion corresponding to the friction circumferential portion.
The lens focusing device described in Section 1.