JPS63187212A - Lens position detector - Google Patents

Abstract

PURPOSE:To perform highly durable and stable position detection without contacting by detecting a light-shade pattern part provided to the outer periphery of a focus ring or zoom ring optically by a photosensor. CONSTITUTION:Infrared rays l emitted by a light emitting element 23 pass through 19a of an optical fiber 19 and are transmitted to a projection lens 15 and projected on the light-shaped pattern part 12a printed on the circumference of the zoom ring 12. The infrared rays (m) are reflected by a white part of the pattern part 12a, projected into a fiber 19 through a lens 15, and transmitted to a light receiving element 27 through 19b of the fiber 19, so that the infrared rays (n) from the element 23 are detected. The opposite surface of the projection lens 16, on the other hand, is a black frosted part on the surface of the ring 12 and infrared rays which are emitted by a light emitting element 24, transmitted by an optical fiber 20, and projected by a lens 16 is hardly reflected, so a light receiving element 28 detects no reflected light. Thus, the prescribed light-shape pattern part is only provided to the circumferential part of the ring 12 to obtain a corresponding signal, and the position of the ring 12 can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a lens position detection device for an autofocus lens in a video camera or a camera-integrated video tape recorder (hereinafter referred to as a camera-integrated VTR).

2. Description of the Related Art In recent years, video tape recorders (hereinafter referred to as VTRs) have become rapidly popular, and as video cameras and camera-integrated VTRs have become smaller and lighter, opportunities to enjoy camera photography have also increased. When taking pictures with a camera, an autofocus (hereinafter referred to as AF) mechanism is becoming an essential element because it allows easy and reliable photography. In order to operate the AF mechanism accurately, the states of focus, zoom, etc. must be detected, and a lens position detection device is required for this purpose. An example of a conventional lens position detection device will be described below with reference to the drawings.

FIG. 4 is a sectional view showing the configuration of a conventional lens position detection device used to detect the focus state. Further, FIG. 5 is a side view of FIG. 4.

In FIG. 6, the focus ring 2 is rotatable around the lens optical axis 7. As shown in FIG. A drive pin 2a is protruded from the outer circumference of the focus ring 2, and is loosely fitted into a groove 3a of the slider 3 to which the contact 4 is fixed. Further, on both sides of the lens position detection device 1, a circular guide groove 5a is provided with the lens optical axis 7 as the center, and the slider 3 is loosely fitted into this guide groove 6a and rotates around the lens optical axis 7. It is rotatable.

The tip 4a of the contact 4 fixed to the slider 3 is connected to the case 5
Printed circuit board held inside (hereinafter referred to as P board)
It is in contact with the inner surface of 6. Therefore, when the focus ring 2 is rotated about the lens optical axis t7, the tip 4a of the contact 4 slides on the P plate e. As shown in FIG. 5, conductive parts 6a, 6b, and 6c are provided on the P plate 6 at positions facing the tip 4a of the contact 4.

The operation of the conventional lens position detection device configured as described above will be described below.

In FIG. 4, the focus ring 2 rotates about the lens optical axis 7 in the direction opposite to the arrow A, and the tip 4a of the contact 4
When is at position X, the conductive portion 6a and the conductive portion 6b are electrically connected through the contact point 4, as is clear from FIG. Similarly, when the tip 4a of the contact 4 rotates in the A direction and is between the X and Y positions, there is no conduction between the conductive parts 6a, eb, and 8c.

Next, between the Y and Z positions, the conductive portion 6a and the conductive portion 6C are electrically connected. And at the Z position, there is a conductive part 6a.

sb and 6c are all conductive. Therefore, if the X position is the focus ■ position, the Z position is the closest distance position, and the Y position is approximately midway between ■ and the closest distance, then
By checking the conduction between the conductive parts 8a, 6b, and 6c, it is possible to detect the position of the lens when focusing is performed. Furthermore, a similar method can be used to detect the lens position when the zoom is operated.

Problems to be Solved by the Invention However, in the above configuration, the slider 3. Contact point 4. P board 6. Since the case 6 is located there and the contact 4 rotates together with the focus ring 2 (rotation angle is approximately 1oo0), it is very large in the radial and circumferential directions and is heavy in weight. Become. In addition, the number of parts is large, precision is required, and assembly man-hours are required, which increases costs. Therefore, this poses a major hindrance to efforts to reduce the size, weight, and cost of recent video cameras or camera-integrated VTRs. In addition, in the above method, the position is detected by contact between the contact 4 and the P plate 6, and the tip 4a of the contact 4 is always sliding on the P plate 6, so the durability and
There are serious problems in terms of stability. Elements such as durability and stability are very important for video cameras and camera-integrated VTRs that are often used continuously for long periods of time.

The present invention solves the above problems and provides a lens position detection device that is small, lightweight, low cost, and highly durable and stable.

Means for Solving the Problems In order to solve the above problems, the lens position detection device of the present invention includes a lens barrel body, a focus ring that rotates to focus the lens barrel body, and a variable magnification. a light-dark pattern portion provided on the circumference of at least one of the zoom rings that rotate to perform the zoom ring, a light-emitting means for emitting light, and a pair of optical fibers for transmitting the light from the light-emitting means;
a lens that projects light transmitted from the light emitting means through one of the optical fibers onto the bright and dark pattern portion, and projects light reflected from the bright and dark pattern portion of the projected light into the other optical fiber; and a light receiving means for receiving the reflected light transmitted by the optical fiber.

Operation According to the present invention, the position of the lens can be detected in a non-contact manner by optically detecting the light and dark pattern provided on the outer periphery of the focus or zoom ring using a photosensor. Therefore, extremely durable and stable detection is possible. Further, by transmitting light through an optical fiber, the degree of freedom in arranging the light emitting means and the light receiving means increases. Due to recent advances in semiconductor technology, photosensors have become extremely small and low cost. On the other hand, the bright and dark pattern can be printed or pasted directly on the focus ring or zoom ring, which reduces the number of parts and the number of assembly steps, making it possible to detect the lens position with a small, lightweight, and low-cost device. Become.

Embodiment Hereinafter, a lens position detection device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a side view showing the configuration of an embodiment of the present invention.
FIG. 2 is a sectional view of the main part of FIG. 1.

In FIG. 1, the focus ring 11 and the zoom ring 12 are located on the outer periphery of the lens barrel body 32, and the lens optical axis 3
3, each can be rotated by a predetermined angle. On the circumference of the focus ring 11 and the zoom ring 12, there are two rows of light and dark pattern parts 11a, 111) and 12a, 1.
2b are arranged respectively. This light and dark pattern portion 11a
, 11b.

12a and 12b are constructed by silk printing white paint on the outer circumferences of the focus ring 11 and the zoom ring 12, respectively, which are painted matte black.

Then, as shown in FIG. 3, each light and dark pattern portion 11a.

Light projecting lenses 13, 14, 15.16 are arranged at positions facing 11b, 12a, 12b, and each light projecting lens 13, 14, 15.18 is connected to an optical fiber 17.18.
, 19.20 are connected, and the projection lenses 13.14,
15 and 16 are fixed to the lens holding plate 3o by a fixing member 29. said optical fiber 17.18,
The other ends of 19.20 are each branched into two as shown in FIG. 1, and one end of each fiber is 17&, 18a.

19a and 20a are light emitting elements 21. each using an infrared light emitting diode or the like disposed on the camera circuit board 34.
22, 23, 24, and the other end 1
7b, 1sb, 19b, and 20b are light receiving elements 25, 26, 27, and 27 disposed on the camera circuit board 34, respectively.
28.

The operation when the lens position detection device of this embodiment configured as described above is used to detect the position of the zoom ring 12 will be described. As shown in FIG.
The light is transmitted to the light projecting lens 16 shown in the figure, and is projected by the light projecting lens 16 onto a bright and dark pattern portion 12a printed on the circumference of the zoom ring 120. The infrared rays m projected onto the light and dark pattern portion 12a affect the white portion (the third
The light is reflected by the satin-shape portion shown in the figure), passes through the light projection lens 15 again, and is projected into the optical fiber 19.
As shown in the figure, the infrared rays n are transmitted through the optical fiber 19 b to the light receiving element 27 and can be detected from the light emitting element 23 .

On the other hand, the opposing surface of the light projecting lens 16 has a bright and dark pattern portion 1.
It is not the white part of 2b, but the black matte part on the surface of the zoom ring 12, and since the infrared rays emitted by the light emitting element 24, transmitted by the optical fiber 20, and projected by the light emitting lens 16 are hardly reflected, the light receiving element 28, reflected light cannot be detected. Therefore, if a predetermined bright and dark pattern is provided on the circumference of the zoom ring 120, signals can be obtained corresponding to the bright and dark pattern.
position detection becomes possible.

Detection of the position of the focus ring 11 is also exactly the same as that of the zoom ring 12, so a description thereof will be omitted.

As described above, according to this embodiment, at least two light emitting lenses are arranged at positions facing each of the two rows of light and dark pattern parts, and the light emitting lenses, the light emitting element, and the light receiving means are connected by optical fibers. By doing so, the positions of the focus ring and zoom ring can be detected without contact, improving durability and stability. Further, the optical fiber allows for increased flexibility in the arrangement of the light emitting means and the light receiving means, has a small number of parts, is easy to assemble, and is highly effective in reducing size and weight.

In addition, although the above-mentioned example showed the case where an infrared light emitting diode was used as the light emitting means, visible light may also be used.
In this case, a light receiving means for visible light can also be used.

Effects of the Invention As described above, the present invention is highly reliable because it detects the positions of the focus ring and zoom ring in a non-contact manner.
In addition, since the number of parts is small, it is easy to assemble and a reliable position detection device can be realized at low cost. Therefore, a significant effect can be obtained in increasing the reliability of lenses, video cameras, etc., and reducing the size and weight of the lenses and video cameras.

[Brief explanation of the drawing]

FIG. 1 is a side view of a lens position detection device according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of the main parts of the zoom lens and position detection means of the same device, and FIG. 3 is a light projection device. FIG. 4 is a sectional view of a conventional lens position detection device as seen from the front, and FIG. 5 is a partially cutaway right side view of FIG. 4. 11...Focus ring, 12...
Zoom ring, 11a, 11b, 12a, 12b=-River/light and dark pattern section, 13-16...Light projection lens, 1
7~2°...Optical fiber, 21~24...
...Light emitting element, 26-28... Light receiving element, 3
2... Lens barrel body. Name of agent: Patent attorney Toshio Nakao and 1 other person f2
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Claims (1)

[Claims] A light and dark pattern portion provided on the circumference of at least one of a lens barrel body, a focus ring that rotates to focus the lens barrel body, and a zoom ring that rotates to change magnification; a pair of optical fibers that transmit light from the light emitting means; one of the optical fibers projects the light transmitted from the light emitting means onto the bright and dark pattern area; A lens position detection device comprising: a lens for projecting light reflected by a bright and dark pattern into another optical fiber; and a light receiving means for receiving the reflected light transmitted by the optical fiber.