JPS6234135A - Af device for variable focus camera - Google Patents

Abstract

PURPOSE:To cut off disturbing incident light and to improve the precision of distance measurement by providing a hood for limiting the external light incidence in the front of an AF optical system and providing an interlocking means which associates the operation of a hook position switching means for moving forth and back the hood with the operation of a focus varying mechanism. CONSTITUTION:A subordinate lens 2 is used behind a main lens 1 for wide-angle photography during telephotography and those optical photography systems are incorporated in a lens barrel part 4 so that the subordinate lens 2 moves onto and away from an optical path of photography through the movement of the lens barrel part 4. A projection means 5 and a light-receiving means 6 are fixed to the front part of a camera body 9 through frame members 5c and 6c, provided externally with the lens barrel part 4 as a hood, and incorporated in the lens barrel part 4 so that they move relatively in the front-rear direction of the camera. The lens barrel part 4 is provided with a hood opening part 4a provided in front of a projection part and a hood opening part 4b which is provided in front of the light reception system of AF to cut off external disturbing light.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to an automatic focusing device (
(hereinafter abbreviated as AF device).

[Background of the invention]

In most conventional AF cameras, the focal length of the photographic lens was closer to the wide-angle side. This is because when designing with priority given to compactness and cost reduction, the AF control device and the like can be configured relatively easily if the focus is short. In other words, when trying to design a compact AF camera with a lens whose focal length is closer to the telephoto side or a lens angle that changes between wide-angle and telephoto, it is difficult to improve its controllability due to various factors such as shallow depth of field. This is because it is difficult.

For example, considering the problem of external light intruding into the distance measurement optical system that obtains distance measurement information and reducing its accuracy, when using a long focal length lens, the subject is often far away, so it is inevitable that the distance measurement information S/ This is because the N ratio decreases, deteriorating distance measurement accuracy, and resulting in failure to achieve highly accurate AF.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned problems, and its purpose is to provide a highly accurate AF device for a camera incorporating a variable focus lens without requiring a large installation space. All devices that allow distance measurement information to be obtained are provided.

Another object of the present invention is to have high moldability, low cost,
Furthermore, it is possible to provide a highly functional compact camera using an AF device with good distance measurement accuracy.

[Summary of the invention]

The ninth feature of the AF device according to the present invention that achieves the above-mentioned object is that, in a variable focus camera equipped with a variable focus mechanism and an AF device including an AF optical system, A hood for restricting the incidence of disturbance light is provided on the front surface, a hood position switching means for moving the hood in the front and back direction of the camera, and the operation of the hood position switching means is operatively linked to the operation of the variable focus mechanism. The means of communication is set up by a friend.

[Embodiments of the invention]

FIGS. 1 and 2 are diagrams showing an outline of the configuration of an embodiment of the present invention. FIG. 1 shows the entire configuration during wide-angle shooting, and FIG. 2 shows the entire configuration during telephoto shooting.

In the camera in this example, a lens barrel section (hood for restricting the incidence of ambient light) 4 provided on the front surface of the camera body 9 has a fixed length in the front-rear direction, with a straight lever 7 installed between them. It has a characteristic configuration in which it is relatively displaced within a range, thereby modifying the characteristics as a hood for the AP optical system.

The various parts of the system are explained below. 1 is the main lens for wide-angle photography, 2 is the auxiliary lens that is placed behind the main lens 1 during telephoto shooting, and these photographic optical systems are incorporated inside the lens barrel section 4. The sub-lens of this example is provided so as to advance or retreat into the photographing optical path via a gear mechanism (not shown) or the like as the lens barrel section 4 moves relative to the camera body 9.

The two are a light projecting means and a light receiving means that constitute the optical system part of the AF device, and are fixed to a predetermined position on the front surface of the camera body 9 by frame members 5c and 6c, respectively, and are also used as a hood. A lens barrel section 4 is externally mounted, and the camera is assembled to be relatively movable in the front and rear directions.

Note that 5a is a light projecting lens, 5b is a light projecting element, 6& is a light receiving lens, and 6bH is a light receiving element, and the light projecting element and the light receiving element are connected to a control circuit (not shown).

Further, the lens barrel section 4 is provided with a hood opening 4 placed in front of the light projecting system and a hood opening 4b placed in front of the AF light receiving system to prevent external light from entering.

Note that the film 13 mounted inside the 3#:t camera body
This figure shows the inner hood formed by the frame member 6c of the AE light receiving system.

Note that the symbols 8 to 12 shown in these figures indicate the following, respectively. That is, 8 #i external incident light, 9 the field of view of the AF floodlight system, 11 the object when using a relatively short focal length lens, 11 m the distance measuring light flux,
12 Subject when using long distance long focal length lens, 12a
Fi is the distance measuring light flux.

Next, I will explain the characteristics of the camera with the above configuration, especially the characteristics of the AF device. During wide-angle shooting as shown in FIG. 10 is obtained. On the other hand, during telephoto shooting as shown in Figure 2, external light entering from a wide angle is
The light does not easily enter the light receiving element because it is obstructed by the hood opening 4b of the lens barrel section 4 that has moved forward relative to the AF optical system.

Therefore, according to this example, it is possible to obtain the disturbance light entering the AF light receiving system at a temperature suitable for the husband's shooting mode using the moving hood (lens barrel section). This is effective when shooting using a long focal length lens when the target is far away and the ratio of distance measurement information to noise such as ambient light is low, potentially reducing distance measurement accuracy.

〔Effect of the invention〕

As explained above, according to the rC of the present invention, in an AF camera with a built-in variable focus lens that operates as a long focal length lens, the hood moves back and forth according to changes in focal length, which reduces the AF distance measurement accuracy due to the intrusion of external light. This makes it possible to easily improve distance measurement accuracy, especially when measuring long distances where the S/N ratio of distance measurement information decreases. Effective when focusing.

Also, without adding cost l- to distance measurement circuits, elements, etc.
It is possible to semi-regenerate the AF system 6 which is highly dusty, and has the advantage of showing a remarkable effect on improving the functionality of compact cameras, especially where an L-type and inexpensive configuration is required.

[Brief explanation of the drawing]

The drawings are cross-sectional views showing an example of the general configuration of a compact camera equipped with an AF device according to the present invention, with FIG. 1 showing the camera during wide-angle shooting, and FIG. 2 showing the camera during telephoto shooting. l: Raw lens 2: Sub-lens 3: Film 4: Lens barrel part Σ: Light projecting system D: Light receiving system 5a: Light projecting lens 5b: Light projecting element 6 凰: Light receiving lens 6b: Light receiving cables 5c, 6c: Frame 7: @ Advance lever 9: Camera body

Claims (1)

[Claims] In a variable focus camera equipped with a variable focus mechanism and an AF device including an AF optical system, a hood for restricting the incidence of disturbance light is provided on the front face of the AF optical system, and the hood is moved in the front and back direction of the camera. An AF device for a variable focus camera, comprising: a hood position switching means; and a linking means for operatively linking the operation of the hood position switching means and the operation of the variable focus mechanism.