JPS6243610A - Automatic focusing device - Google Patents

Abstract

PURPOSE:To simplify a device, to reduce its size, and to improve the reliability by providing a plane mirror which has its axis of rotation at right angles to the plane containing the optical axes of a photodetecting lens and a photodetecting element and associating its rotation with the quantity of extension of a photographic lens. CONSTITUTION:The light of a light emitting element 2 is projected on an object 12 through a lens 1 and its reflected light is passed through a lens 3 and reflected by the plane mirror 8 to reach the photodetecting element 4. At this time, when the light is not incident on photodetecting surfaces of the two- division photodetecting element 4, a focus can 5 is rotated and the plane mirror 8 contacting its can surface 6 rotates until the light is incident on the element 4 uniformly. Thus, the plane mirror 8 is provided between the lens 3 and element 4, so as complex mechanism for moving the element 4 is not necessary and the device is reduced in size; and the photodetecting element 4 is fixed, so the reliability is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an automatic focus adjustment device for a camera, and particularly to a distance measuring mechanism that is advantageous for miniaturization.

[Background of the invention]

A conventional device is shown in FIG. Light-emitting lens 1 and light-emitting element 2
a light receiver consisting of a two-split light receiving sensor 4 that moves in a direction perpendicular to the optical axis of the light receiving lens in conjunction with the amount of extension of the light receiving lens 5 and the photographing lens in conjunction with the amount of extension of the light receiving lens 5; and a focus can movement amount. A cam 6 is used to enlarge the cam 6 and improve sensor positioning accuracy, and a K is used to convert the displacement amount of the cam 6 into the displacement amount of the two-split light receiving sensor 4. One end is in contact with the cam 6, and the other end is connected to one of the two split sensor sensors. The link mechanism 7 is biased by an elastic body 9 in order to make contact with the part without any gaps.
It consists of

The light beam projected from the light emitting element 2 passes through the light emitting lens 1 and is irradiated onto a subject at a distance 7.

The reflected light from the subject passes through the light receiving lens and is focused on the two-split light receiving sensor 4. At this time, if the reflected light is not evenly incident on each divided surface of the two-divided sensor 4, the 7f-cascan 5 is moved by a motor ( (not shown), and when the reflected light is evenly distributed on each divided surface, the rotation of the motor is stopped.

On the other hand, the amount of movement of the light receiving sensor is determined by the base line length t, which is the distance between the optical axis of the emitter and the optical axis of the receiver, and the focal length f of the light receiving lens.
Subject distance l11! It is determined by ν and is expressed by the following formula.

fL , , , , , , , , , ,
(1) ν Furthermore, the relationship between the amount of movement X of the light receiving sensor, the amount of movement Z of the light receiving sensor, and the link mechanism consisting of a lever having a length l+ and t2 is expressed by the following equation.

X=-beggar-Z ・・・・・・・・・・・・
(2) In order to downsize the emitter and receiver, it is necessary to reduce the base line length t, and when t is made smaller, the formula (
1), the sensor movement amount X also becomes smaller.

Therefore, t! in equation (2)! Alternatively, it is necessary to decrease 2 or increase tl. However, 2 is a value determined by optical design, and there is a structural limit to K, which also reduces t2.

In addition, when tl is increased, the light receiver is moved away from the photographic lens, which has the disadvantage that the overall size becomes larger, and that the reflected light from the subject may become distorted within the screen depending on the distance to the subject. Ta. As described above, it has been difficult to reduce the amount of sensor movement using the link mechanism.

Furthermore, by reducing the baseline length, high precision is required, and it has been difficult to satisfy this requirement with conventional link mechanisms due to their complicated structures.

A related device of this type is, for example, Japanese Patent Publication No. 46-28500.

[Purpose of the invention]

An object of the present invention is to provide a distance measuring mechanism that is advantageous for downsizing in an active automatic focusing device.

[Summary of the invention]

In the conventional method, the linear movement of the focus can was converted into rotational movement using a link mechanism, and the light receiving sensor was moved linearly in a direction perpendicular to the optical axis of the light receiving lens, making the structure complex and making it difficult to downsize. there were. Therefore, the present invention provides a plane mirror having a rotation center perpendicular to the plane formed by the light receiving lens optical axis and a light emitting lens optical axis between the light receiving lens and the light receiving sensor, or a concave mirror having a similar rotation center, and the light receiving lens We decided to form a cam so that the plane mirror or the concave mirror changes the angle it makes with the optical axis depending on the subject distance, and this angle corresponds to the amount of movement of one cascade.

As a result, the conventional moving mechanism is no longer necessary, and accuracy can be easily achieved.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4. Figure 1 is for explaining the structure of the automatic focus adjustment device housed in the camera grip.

A part of the grip is broken. FIG. 2 shows the camera viewed from the front, with the automatic focus adjustment device installed on the left side when facing the camera. Figure 5 shows that instead of a plane mirror,
FIG. 7 is a side view of another embodiment in which a concave mirror is used and a light receiving lens is not required.

In FIG. 1, a light emitting part consists of a light emitting lens 1 and a light emitting element (for example, an infrared light emitting diode) 2, a light receiving lens S, a two-split light receiving element (for example, a two split pin-foot diode) 4, and a light receiving lens optical axis A1. and a plane mirror 8 having an axis 8α for rotation perpendicular to the light receiving sensor central axis A2 and a plane @! A light receiving section is constituted by an elastic member (for example, a tension coil spring or a torsion spring) 9 that brings the cam 8 into contact with the cam 6 of the focusing can 5 of the photographic lens without a gap.

The light beam from the light emitting element 2 passes through the light emitting lens 1 and reaches the subject 1.
The reflected light from the subject 12 passes through the light-receiving lens 5, is reflected by the plane mirror 8, and reaches the light-receiving sensor 4. At this time, when the reflected light is not equally incident on each light-receiving surface of the two-split light-receiving sensor 4, that is, when it is out of focus, the camera 5 is rotated by a motor (not shown), and the The plane mirror 8 in contact with the cam surface 6 of the focus can 5 also rotates about the rotation center axis 8α until the reflected light evenly enters the two-split light receiving sensor 4.

FIG. 5 is for explaining the relationship between a light beam that enters the light-receiving lens 5 at an angle θ and an angle a of the plane mirror 8 for reflecting the light beam to the center of the light-receiving sensor 4.

L is from the principal point position 5α of the light receiving lens 5 to the plane fip,
8, the optical path length lo is from the plane mirror 8 to the light receiving sensor 4.
is the optical path length up to.

θ is the angle of the light beam incident on the light receiving lens 5, α is the angle with respect to the optical axis of the plane mirror 8, and β is the angle of incidence of the light beam on the plane mirror 8. Between these, the following equation holds true.

Further, θ is determined from the subject distance ν and the base line length t using the following equation.

θ= jAx-' l-・・・・・・・・・・・・・・・
- (4) Equation (5) 1 Using Equation (4), the rotation angle 4 of the plane mirror 80 with respect to the object distance my is determined.

For example, when the subject distance is infinite, the angle α of the plane mirror is 45 degrees. Further, when the subject distance y is 1 m at close range, L = lOswa, t6 = 5 cod, and the base line length t is 25 cm, n becomes 42.85 degrees.

In this example, the angle for focusing the plane mirror from close range to infinity is Z15 degrees.

FIG. 4 is a front view of the plane mirror mounting portion. The plane mirror mounting part includes the plane mirror 8, the rotation center shaft 8a, the lever 14, and the pin 1.
Consists of 5.

The pin 15 is in contact with the cam 6 of the focus can 5, and as the focus can 5 moves, the plane mirror 8
a has a structure that rotates around a rotation center axis 8a.

When a plane mirror is set between the light-receiving lens and the light-receiving sensor in this way, there is no need for a complicated mechanism to move the light-receiving sensor as in the past, and all you have to do is rotate the plane mirror. This structure is advantageous when shortened length and high precision are required.

FIG. 5 shows the light receiving lens 5 and the plane f! ! , 8 is replaced by a concave mirror 15.

When the concave mirror 15 is used, the light receiving lens 5 is unnecessary, and the number of parts can be reduced compared to when the flat surface 9B is used.
The same effect as using a plane mirror can be obtained.

Calculating an example using a concave mirror, if the incident axis B1 is a ray from infinity, then the mirror axis B2j of the concave mirror! When the angle is set at 45 degrees with respect to the incident axis B1 and the light beam is incident on the center of the light receiving sensor 4, the close distance ν=1rn and the base line length 1
= 25 m, the mirror axis only needs to be rotated by 1/2 of θ in equation (4). That is, the angle is approximately 0.7 degrees, and distance measurement can be performed at a smaller angle than when using a flat surface.

〔Effect of the invention〕

According to the present invention, the conventional link mechanism can be replaced.

Since the distance is measured by rotating a flat mirror or a concave mirror, the entire device can be made compact.

Furthermore, since the light receiving element can be fixed, repeated loads are not applied to the connection portion, and there is no possibility of wire breakage or contact failure, thereby improving reliability.

Furthermore, there are fewer parts that affect accuracy compared to conventional traps, making it easier to achieve high precision in the mechanism due to miniaturization.

[Brief explanation of the drawing]

Fig. 1 is a side view of one embodiment of the present invention, and Fig. 2 is a front view.
．． FIG. 5 is an explanatory diagram of the principle, FIG. 4 is a front view of a plane mirror mounting portion, FIG. 5 is an explanatory diagram of another embodiment, and FIG. 6 is an explanatory diagram of a conventional example. 1... Light-emitting lens, 2... Light-emitting element, S.
... Light receiving lens, 4... Light receiving element, 5...
Focus can, 6... cam, 7... link mechanism, 8... plane mirror, 9... elastic member,
10...Camera, 11...Photographing lens,
12...Subject, 15...Pin, 14...Lever, 15...Concave mirror◇, ζ°-\

Claims (1)

[Claims] 1. Consists of a light emitter consisting of a light emitting optical system and a light emitting element, a light receiver consisting of a light receiving optical system and a light receiving element, and a mechanism that controls the incident light beam to the light receiving element in conjunction with the extending operation of the photographic lens. In the automatic focusing device, a plane mirror is arranged between the light-receiving optical system and the two-split light-receiving element, and the plane mirror is arranged on an axis perpendicular to the plane formed by the optical axes of the light-emitting optical system and the light-receiving optical system. An automatic focusing device characterized by having a rotation center and rotating in conjunction with the extending operation of a photographic lens.