JPS62172311A - Automatic focusing device - Google Patents

Abstract

PURPOSE:To simplify the structure of a focusing device and to improve the reliability of the device by moving or rotating only an optical system to detect the focusing state. CONSTITUTION:A light beam emitted from a light emitting element 3 is projected into a subject 8 by a projection lens 1, the reflected light is bent by a plane mirror 21 through a photodetecting lens 3 and its image is formed on a two-divided photodetecting element. A photodetecting spot image is formed on a position separated from the dividing line of the photodetecting element 4, and when a fixed difference is generated between the quantity of light made incident upon two photodetecting surfaces, the difference of the quantity of light is detected by a photodetecting circuit and decided as a defocused state and the rotating direction of a focus ring 5 is detected. A driving circuit rotated the focus ring 5 and moves a optional system holding member 22 through a rink mechanism 7 in a direction that the center of the photodetecting spot coincides with the dividing line of the photodetecting element 4. When the dividing line of the photodetecting element 4 coincides with the center of the photodetecting spot and the difference of the quantity of light made incident upon the two photodetecting surfaces is reduced less than the fixed value, and decided, as the focusing state. Consequently, the reliability of the focusing device can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an automatic focusing device suitable for use in a video camera or the like.

[Background of the invention]

Conventionally, video cameras have been equipped with an automatic focusing device that automatically adjusts focusing in order to improve operability. Various such means have been proposed, and one example is disclosed in Japanese Patent Publication No. 46-28500, which includes a light emitting means and a light receiving means, and irradiates the subject with light emitted from the light emitting means. The reflected light is received by a light receiving means,
There are several techniques that detect the irradiation position of the reflected light on a sensor (light receiving element) in the light receiving means and adjust the focusing.

Hereinafter, such a conventional automatic focusing device will be specifically explained with reference to FIG. In addition, in the same figure, 1 is a projection lens,
2 is a light emitting element, 3 is a light receiving lens, 4 is a two-part light receiving element,
5 is a focus ring, 6 is a cam, 7 is a link mechanism, 9 is a biasing member, 10 is a fixing member, and 11 is a wire rod.

In the figure, this automatic focusing device includes a light emitting section consisting of a projection lens 1 and a light emitting element 2, a light receiving lens 5 having an optical axis separated by a distance t from the optical axis of the light emitting section, and a two-part light receiving cable 4. and a light receiving element drive section including a focus ring 5 having a cam 6, a link mechanism 7, and a biasing member (elastic body) 9. With this configuration, a spot light beam (projection light beam) from the light emitting element 2 is projected onto the subject by the projection lens 1, and reflected light from the subject is received by the light receiving lens 3 and the two-split light receiving element 4. When the subject distance y changes, the angle at which the reflected light of the spot light projected onto the subject enters the light receiving lens 3 changes, and the image of the projected spot light (light receiving spot) is formed at the focal length f position of the light receiving lens 5. ) moves in a direction perpendicular to the optical axis of the fifth light receiving lens. This amount of movement is uniquely determined by the subject distance y, so the two-split light receiving element 4 is placed at the position where the light receiving spot has moved.
The light receiving spot is set so that when the light receiving element is moved in the X direction, the light receiving spot is located on the dividing line of the two-split light receiving element.

The movement of the two-split light receiving element 4 in the X direction is performed by a cam 6 provided on a focus ring 5 rotated by a motor or the like, a link mechanism 7, and a biasing member 9.

Incidentally, a wire 11 is connected to the two-split light receiving element 4 for transmitting two systems of signals corresponding to each split light receiving element, and this wire is connected to a signal processing circuit board (not shown). There is. Furthermore, since this wire transmits a weak electrical signal from the light receiving element, a shielded wire that is less susceptible to noise is used. However, since the shield wire has strong elasticity, when installing the 2 min*lJ photodetector, it is necessary to fix it with the fixing member 10 and then connect it to the signal processing circuit board. It has a structure that eliminates the influence of the tensile force caused by the wire between it and the substrate.

However, regarding the wire between the fixing member 10 and the two-split light-receiving element 4, since the fixing member described above cannot be used as a countermeasure, twisting and tensile force caused by the wire remain. For this reason, force is applied to the two-split light receiving element 4, and the position of the two-segment light receiving element 4 cannot be determined correctly, causing a decrease in focusing accuracy. In order to ensure the accuracy of this position, the biasing member 9
The two-split light receiving element 4 is forced to one side, and the position tI
I had to set it to L. Therefore, the force of the biasing member 9 is increased, resulting in a complicated structure and a large number of parts. Since it is necessary to connect to the board via a wire, there are disadvantages in that there are many work steps and workability is poor.

Furthermore, since the two-split light-receiving element 4 is moved every time a focusing operation is performed, the wire connected to the two-segment light-receiving element 4 is bent and stretched, which may cause material fatigue and breakage. I had problems with my sexuality.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide an automatic focusing device with a simple structure and high reliability.

[Summary of the invention]

In order to achieve this object, the present invention employs a light-receiving optical system that is capable of focusing while a two-split light-receiving element is fixed. In the 5'e section optical system, the imaging position of the light beam from the subject on the two-split light receiving element can be adjusted by moving these two in the optical axis direction at the same time, or by rotating only the plane mirror. It is unique in that it is made to focus by

The amount of movement or rotation of the light receiving optical system is linked to the amount of rotation of the focus ring by a cam and a link mechanism provided on the focus ring. In addition, focusing is similarly achieved in the light-receiving optical system made of a concave mirror.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram showing a first embodiment of an automatic focusing device according to the present invention, in which 8 is a subject, 21 is a plane mirror, 22 is an optical system holding member, and the parts corresponding to FIG. are given the same sign.

In the figure, an optical system holding material 22 holds an optical system composed of a light receiving lens 5 and a plane mirror as a reflecting mirror.

The link mechanism 7 transmits the movement of the cam B integrated with the focus R&5 to the optical system holding member 22.

The ends of this link mechanism 7 abut on the cam 6 and the optical system holding member 22, respectively, and the position of the optical system holding member 22 is regulated by the focus ring 5.

The biasing member 9 is for bringing the link mechanism 7 into contact with the cam 6 and the optical system holding member 22.

The distance between the optical axis of the projection lens 10 and the optical axis of the light receiving lens 5 is
It is set to l (base plate length). The plane mirror 21 is fixed at an angle of 45 degrees with respect to the optical axis of the light receiving lens 30. The optical system holding material 22 has a structure that is movable in the optical axis direction (X direction) of the light receiving lens 30.

Next, the automatic focusing operation with the above configuration will be explained.

A light beam emitted from the source light source 2 is projected onto a subject 8 by a projection lens 1. The reflected light from the object passes through the light-receiving lens 3 and is bent by the flat arm 21, forming an M image on the two-split light-receiving element 4.

The following relationship exists between the sunspot distance f of the light-receiving lens 3, the subject distance y, and the imaging position of the light-receiving spot image.

In addition, the moving wave in the optical axis direction of the optical system holding member 220 is
If the length of the contact point between the link mechanism 70 fulcrum A and the optical system holding material 22 is l3, the length of the contact point between the fulcrum A and the cam 6 is 6, and the amount of movement of the contact point on the cam 6 is Z, then the amount of movement is X is expressed by the following formula.

In the automatic focusing operation of this implementation hook, when an equal amount of light is incident on the two light-receiving surfaces of the two-part light-receiving element 4, a focused state is achieved.

When a light-receiving spot mound is formed at a position cut from the top of the 2-split light-receiving element 40 dividing line (light-receiving surface division boundary of the 2-split light-receiving element), a certain difference occurs in the amount of light incident on the two light-receiving surfaces. The difference in light amount is detected by a light receiving circuit (not shown), it is determined that the focus ring 5 is out of focus, and the direction in which the focus ring 5 should be rotated is detected. When the light receiving circuit detects an out-of-focus state, a motor drive circuit (not shown) energizes the motor to rotate the focus ring 5. At the same time, the 10,000 contact points of the link mechanism 7 are housed in the cam 6 of the focus R5 and move in the X direction. The other contact point of the link mechanism 7, which is in contact with the optical system holding member 22, moves the optical system holding member 22 in a direction in which the center of the light receiving spot is aligned with the 40 divisions of the two-divided receiving element.

When the center of the dividing line of the two-split light-receiving element 4 and the light-receiving spot are separated by a distance, and the difference in the amount of light incident on the two light-receiving surfaces becomes less than a certain value, the light-receiving circuit determines that the focus is on and stops the rotation of the motor. make it stop.

To give an example of the amount of movement of the optical system holding material 22, if the subject distance y = 1 m, the distance of the light receiving lens = 25 mm, and the focal length of the light receiving lens is 1@f = 2 am, then the amount of movement is Q, 5 mm. Become.

In this embodiment, the position of the light-receiving spot is detected by moving the optical system instead of by moving the two-split light-receiving element. The position llIc degree is the same as that of the conventional example. However, since the two-split light-receiving element is fixed, there is no effect on the set position of the two-split light-receiving element due to twisting or tensile force of the wire. As a result, even if a shield wire with high elasticity is used as the edge material as in the past, the position of the light-receiving spot and the two-split light-receiving element will not be misaligned due to twisting or tensile force of the wire.

Furthermore, since the two-split light-receiving element is fixed, the wire does not bend or stretch due to the focusing operation, so the material does not deteriorate due to fatigue due to bending or stretching, and reliability deterioration factors such as wire breakage can be eliminated.

Note that the two-split receiving element may be directly attached to the circuit board for processing the blank, and in that case, the wire can be omitted.

FIG. 2 is a block diagram showing the main parts of a second embodiment of the eye movement focusing lens 1 according to the present invention, in which 25 is a concave mirror as a reflective imaginary;
24 is a concave mirror holding member, and parts corresponding to those in FIG. 1 are given the same reference numerals. In this embodiment, the light-receiving lens in the first embodiment is replaced with a concave mirror, and the center of the concave mirror 25 is located at a distance from the optical axis of the projection lens 1! (baseline length).

The mirror axis of the concave mirror 23 intersects the optical axis of the projection lens 1 at an angle of 45 degrees, and after bending the light beam incident on the concave mirror 25 parallel to the optical axis of the projection lens 1 by 90 degrees, 4
image on top.

The concave mirror holding member 24 has a structure that fixes the concave mirror 23 and is movable in the optical axis direction of the projection lens 10, and its position is between a cam 6 formed on the focus ring 5, a link mechanism 7 that contacts the cam 6, and a link mechanism 7 that contacts the cam 6. and the biasing member 9.

The focusing operation of this embodiment will be explained below.

The two-split receiving element 4 is arranged on the imaging plane of the concave mirror 23. When the subject is at infinity, the position where the light receiving spot is focused is on a concave surface! ! An image is formed at a focal length f of the concave mirror 23 from the center of the concave mirror 23.

When the subject moves and the distance @y changes, the angle of incidence of the light receiving spot light beam on the concave mirror 23 changes. The amount of change in the angle of incidence on the concave mirror and the amount of change in the reflection angle are the same. Here, if the focal length of the concave mirror 23 is f and the amount of change in the angle of incidence is θ, then the amount of movement of the light receiving spot 3:
8 becomes xs=f@θ. The amount of change θ in the incident angle is the subject. Therefore, the amount of movement of the light receiving spot when the subject moves is the amount by which the concave mirror is moved.As shown in the second embodiment, the mechanism of movement of the concave mirror 25 expressed by equation (11) is the first This is similar to the optical system holding member 22 shown in the embodiment.

To give an example of the amount of movement mentioned above, the subject distance is y=1y+s
, the base length is l = 25 mm, and the focal length of the concave mirror is f = 2.
If it is 0 mm, the amount of movement of the concave mirror will be 0.5 mm.

According to this embodiment, the light-receiving lens shown in Fig. 1 is not required, and focusing can be performed only by moving the concave mirror, so the mechanism is simpler and more compact than the first embodiment. can do.

FIG. 3 is a block diagram showing a third embodiment of the automatic focusing device according to the present invention, in which 25 is a plane mirror, 26 is a lever, and corresponding parts in FIG. 1 are given the same reference numerals. ing.

In the interchromatic state, the reflected beam of spot light projected onto the subject 8 by the light emitting element and the projection lens (not shown) enters the plane @25 via the light receiving lens 3, and enters the plane wj! , 25 forms a light receiving spot image on the two-split light receiving cable 4. The plane mirror 25 has a mechanism that rotates around a point that intersects with the optical axis of the light receiving lens 3 as a result of displacement of the contact point between the cam 6 and the lever 26 due to rotation of the focus R5.

FIG. 4 is an explanatory diagram for explaining the operation of the embodiment shown in FIG. 5, and the same parts as those in FIG. 5 are shown.

According to the same figure, the light flux incident on the light receiving lens 5 at an angle θ,
The relationship with the angle α of the plane mirror 250 for reflecting the luminous flux to the central portion of the two-split light receiving element 4 will be explained.

L is the optical path length from the three-point position 5a of the light receiving lens 5 to the plane mirror 25, and 10 is a plane! The optical path length from I25 to the two-split light receiving element 4, θ is the angle of the light beam incident on the light receiving lens 3, α
is the angle with respect to the optical axis of the plane mirror 250, and β is the plane! This is the angle of incidence of the luminous flux onto I25.

Between these, the following equation holds true as shown in the figure.

Further, the angle of incidence θ of the light flux onto the light receiving lens 3 is determined by the following formula, where y is the subject distance and l is the base line length.

θ= tar&-'cj/y)
The rotation angle α of the plane mirror 25 with respect to the subject distance y is determined from the te1 equation (3) and the equation (4). - To give an example, when the subject distance y is infinite (■), the angle α of the plane mirror is 45 degrees, and the subject distance is y = 1 m + L = 10 mnx
If 10 = 5 mm and l = 25 mm, then α = 4
It becomes 2.8S degree. Therefore, in this example, the rotation angle of the plane mirror is 2.15 degrees when the subject distance changes from close range (1 m) to infinity.

In this way, it is sufficient to simply install a plane mirror between the light receiving lens and the two-part receiving element and rotate the plane mirror, which simplifies the structure. Furthermore, since there are fewer movable parts, error factors related to movement are reduced, and instability in the position of the light receiving spot with respect to the two-split light receiving element 4 is reduced.

FIG. 5 is a block diagram showing the main parts of a fourth embodiment of the automatic focusing device according to the present invention, in which a lever 27 is a concave mirror, and parts corresponding to those in FIG. 1 are given the same reference numerals. .

In the figure, the reflected light flux of the light spot projected onto the subject 8 by the light emitting element and the projection lens (1 not shown) enters the concave mirror 27, and the reflected light flux is reflected onto the two-split light receiving element 4 by the convergence effect of the concave mirror 27. Form an image.

The concave mirror 27 has a mechanism that rotates about the center of the concave mirror by displacement of the contact point between the cam 6 and the lever 26 due to rotation of the focus ring 5.

6 is an explanatory diagram for explaining the operation of the embodiment shown in FIG. 5, and the same parts as in FIG. 5 are given the same reference numerals.

In the figure, when the object approaches and the angle of incidence of the light beam on the concave mirror 27 is θ, and the focal length of the concave mirror is f, the movement tx of the light-receiving spot image becomes −=f−θ. That is, the center of the light-receiving spot is imaged at a position f·θ apart from the dividing line of the two-part light-receiving element 4. In order to rotate the concave mirror and make the center U of the light receiving spot enter the 40 dividing line of the 2-split receiving element, the normal incidence angle and the reflection angle are inappropriate.
All you have to do is rotate it by θ/2.

A specific example of this embodiment will be explained below.
), the reflected light flux χ from the subject is 4 due to the concave mirror 27.
It is set so that an image is formed on the two-split light receiving element 4 when it is bent 5 degrees. aThe object distance is y = 1m and the baseline length is 1
-25 degrees, the concave mirror only needs to be rotated by 0.7 degrees in order to image the light receiving spot on the dividing line of the two-part light receiving element 4. This amount of rotation is different from that in the case of the third embodiment. It is about 1/3. Therefore, the rotation mechanism can be made smaller, which is effective for downsizing.

〔Effect of the invention〕

As explained above, according to the present invention, since the in-focus state is detected by moving or rotating only the optical system, the two-split light-receiving element can be fixed. This prevents the positioning of the two-split photodetector from becoming unstable due to twisting and tensile force of the wire (and also prevents bending and stretching of the wire at the end (repetitive loads), resulting in wire breakage and poor contact. Thus, it is possible to provide an automatic focusing GC position with superior functionality, except for the drawbacks of the prior art described above.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of an automatic focusing device according to the present invention, FIG. 2 is a block diagram showing a main part of a second embodiment of an automatic focusing device according to the present invention, and FIG. 4 is a main part configuration diagram showing the third embodiment of the automatic focusing IT according to the present invention, and FIG.
FIG. 5 is a diagram illustrating the main part of a fourth practical example of the automatic focusing device according to the present invention. FIG. 6 is an explanatory diagram of the operation of the embodiment shown in FIG. , FIG. 7 is a block diagram showing an example of a conventional automatic focusing device. 1: Projection lens 2: Light emitting element 3: Light receiving lens 4: 2-split light receiving element 5: Focus ring 6: Cam

Claims (1)

[Claims] The light-receiving section includes a light-emitting section consisting of a projection lens and a light-emitting element, and a light-receiving section having a light-receiving element. In an automatic focusing device that focuses on the subject by rotating a focus ring of a photographing lens according to the reception state of the reflected light flux at The focus is automatically adjusted by installing a reflecting mirror at an angle with the axis, fixing the light receiving element of the light receiving part, and changing the position or angle of the reflecting mirror in conjunction with rotation of the focus ring. An automatic focusing device characterized in that the automatic focusing device is configured to obtain a focused state using the following steps.