JPH0731299B2 - Automatic focus adjustment device - Google Patents

Description

The present invention relates to an automatic focus adjustment device suitable for use in a video camera or the like.

[Prior art]

Conventionally, the video camera is provided with means for automatically adjusting the focus in order to enhance the operability.

Although various means have been proposed, for example, a light emitting means and a light receiving means are provided, light emitted from the light emitting means is applied to a subject, and reflected light from this is received by the light receiving means, and a sensor in the light receiving means is used. A technique is known in which the irradiation position of reflected light is detected to adjust the focus. One example is that described in Japanese Patent Application No. 60-92230 by the present applicant. This is configured so that a rotatable parallel plane transparent plate between a light receiving lens and a light receiving element of a light receiving unit is brought into contact with a cam of a focus ring for moving a photographing lens and is rotated in association with the movement of the focus ring. There is. The reflector from the subject passes through the light-receiving lens and the plane-parallel transparent plate, and when the light-receiving surface is not evenly incident on each divided surface of the light-receiving element (two-division sensor), that is, when it is out of focus The ring is rotated by the motor, and along with that, the parallel flat transparent plate in contact with the cam of the focus ring is also centered on the rotation axis.
It rotates until the reflected light is evenly incident on each divided surface of the two-divided sensor. This will bring the video camera into focus. Further, in the conventional example, the total rotation angle of the plane parallel plate is determined by the distance between the optical axis of the light receiving lens and the optical axis of the photographing lens (that is, also 1/2 of the base line length) and the movement amount of the focus ring.

On the other hand, the total rotation angle of the plane-parallel transparent plate is within an allowable range that does not result in total reflection of the infrared light receiving beam (for example, the plane-of-plane plate refractive index
It is 41.2 ° when 1.5168), and it is desirable to take as large a value as possible. There are two reasons, part 1
First, since the parallel plane transparent plate rotation angle allowable tolerance for improving the focusing accuracy is proportional to the total rotation angle, the tolerance can be made large. The two points are that the thickness of the parallel plane transparent plate can be reduced, the weight of the parallel plane transparent plate can be reduced, and the sink mark at the time of molding can be prevented in the case of a plastic molded product. The relationship between the total rotation angle and the thickness of the plane-parallel transparent plate will be described below with reference to FIG.

FIG. 3 is a side view for explaining the action of the plane-parallel transparent plate in the automatic focusing device. 3 is a light-receiving lens, 4 is a light-receiving element, 5 is a plane-parallel transparent plate, and 5a is orthogonal to the optical axis. Rotation axis, 5b is a cam follower that contacts the cam of the focus ring, 5c is a lever that connects the parallel flat transparent plate and the cam follower, 12 is an optical axis, 13 is a reflected light incident light beam, D is a close range to the subject, and f is a light receiving light. Lens focal length, θ is the total rotation angle of the plane-parallel transparent plate, t and N are the thickness of the plane-parallel transparent plate,
The refractive index, L is the distance between the optical axis of the projection lens and the optical axis of the light receiving lens, that is, the base line length.

In the figure, the reflected light projected from the projection lens and reflected by the subject enters the light receiving lens 3 as a reflected input ray 13, and reaches the light receiving element 4 via the plane-parallel transparent plate 5.

FIG. 4 is a front view showing an example of the structure of a plane-parallel transparent plate. Reference numeral 5 is a plane-parallel transparent plate, 5a is a rotary shaft, 5b is a cam follower, and 5c is a lever, which are shown in FIG. It corresponds to the part.

In the figure, one of the levers 5c is fixed to the parallel flat transparent plate 5, and the cam follower 5b is fixed to the other end. The lever 5c and the cam follower 5b may be formed integrally with the parallel flat transparent plate 5 or its holding member.

With the configuration shown in the figure, when the cam follower 5b is moved by the cam of the focus ring, the parallel flat transparent plate 5 is rotated about the rotation axis 5a via the lever 5c.

At this time, the plane-parallel transparent plate 5 determined according to the subject distance
The relationship between the total rotation angle θ of and the thickness t is defined by the following three equations.

However, i ₁ is the incident angle and i ₂ is the outgoing angle.

Here, an example in which the relationship between the total rotation angle θ of the plane-parallel transparent plate and its thickness t is calculated by using specific numerical values will be shown. As a condition, if D = 1200, L = 20, f = 30.802, N = 1.4897, then θt 20.653 ° 4mm 26.490 ° 3mm 36.893 ° 2mm, and the larger the total rotation angle θ, the smaller the thickness t. is there.

[Problems to be solved by the invention]

In the above conventional example, the total rotation angle of the parallel plane transparent plate cannot be arbitrarily selected once the focus ring movement amount and the base line length are determined. There was a problem that the thickness becomes thick when the rotation angle of is small.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the conventional example and to provide an automatic focus adjusting device which has a simple structure and can be downsized.

[Means for solving problems]

As described above, it is advantageous to increase the total rotation angle of the plane-parallel transparent plate because the allowable tolerance is proportional to the total rotation angle. Increase, (2) Shorten the baseline length,
(3) There are three possible ways to shorten the lever length,
Since (1) is inevitably determined by the optical design, it cannot be arbitrarily large. It is advantageous not to make (2) shorter because it is advantageous to make it longer than it is made shorter to improve performance. On the other hand, (3)
If a means for shortening the lever length is selected, the total rotation angle and thickness of the parallel flat transparent plate can be easily selected with the conventional design values.

Therefore, the object of the present invention is to arrange the light emitting portion optical axis and the light receiving portion optical axis unevenly with respect to the photographing lens optical axis, that is, eccentric without changing the baseline length and the focus ring movement amount, By arranging the light receiving part arbitrarily shorter than the light emitting part, the length of the lever connecting the parallel flat transparent plate and the cam follower is made shorter, and the total rotation angle of the parallel flat transparent plate and its thickness are arbitrarily selected. This is achieved by configuring so that it can.

〔Example〕

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

FIG. 1 is a cross-sectional configuration diagram showing an embodiment of an automatic focusing apparatus according to the present invention, in which 1 is a projection lens which constitutes a projection optical system, 2 is a light emitting element (for example, infrared light emitting diode), and 3 is A light-receiving lens that constitutes a light-receiving optical system, 4 is a light-receiving element (two-divided sensor, for example, two-divided pin photodiode), 5 is a parallel flat transparent plate (for example, glass or plastic plate), 6 is a focus ring, and 7 is a cam , 8 is an elastic member (for example, a tension coil spring), 9 is a camera body,
10 is a subject. In this embodiment, the projection lens 1 and the light emitting element 2 constitute a light emitting portion, and the light receiving lens 3, the light receiving element 4 and a parallel plane transparent plate 5 rotatable on a side surface about a rotation axis 5a orthogonal to the optical axis. An elastic member 8 for contacting the cam follower 5b with the cam 7 of the focus ring 6 without a gap, and a lever 5c for connecting the cam follower 5b and the parallel flat transparent plate 5 together constitute a light receiving portion.

In the figure, the light from the light emitting element 2 is projected onto the subject 10 via the projection lens 1, and the reflected light from the subject 10 reaches the light receiving element 4 via the light receiving lens 3 and the plane-parallel transparent plate 5. To do. At this time, when the reflected light is not evenly incident on each divided surface of the two-divided sensor of the light receiving element 4, that is, when out of focus, the focus ring 6 is rotated by a motor (not shown), and accordingly. The plane-parallel transparent plate 5 is also rotated by the cam follower 5b which is in contact with the cam 7 of the focus ring 6 and the rotary shaft 5a.
The center of rotation is until the reflected light is evenly incident on each divided surface of the two-divided sensor.

This will bring the video camera into focus.

FIG. 2 is a front view of the video camera viewed from the side of the subject 10 in FIG. 1, 11 is a taking lens, L is the base length of the projection lens 1 and the light receiving lens 3, and l ₁ and l ₂ are respectively. From a point where a straight line (base line) connecting the optical axes of the projection lens 1 and the light receiving lens 3 and passing through the optical axis of the taking lens 11 intersects with the base line, the optical axis of the projection lens and the optical axis of the light receiving lens are It is a distance and has a relationship of L = l ₁ + l ₂ . The parts corresponding to those in FIG. 1 are designated by the same reference numerals.

In the figure, the base line length L with respect to the optical axis of the taking lens 11, are decentered midpoint of the base line so that the distance l ₂ of the distance l ₁ between the light receiving lens 3 of the projection lens 1 becomes uneven, light The distance l ₂ of the lens ₂ is arbitrarily set smaller than the distance l ₁ of the projection lens 1, and the distance from the rotary shaft 5a of the plane-parallel transparent plate 5 to the cam follower 5b shown in FIG. Thus, the total rotation angle of the plane-parallel transparent plate 5 (θ in FIG.
Is made arbitrarily large.

As described above, according to the present embodiment, the light-emitting unit optical axis and the light-receiving unit optical axis are arranged unevenly with respect to the optical axis of the photographing lens, that is, the base length is not changed and the light-receiving unit is eccentric. By arbitrarily setting the distance l ₂ shorter than the distance l _{1 of the} light emitting part, the lever length of the parallel flat transparent plate 5 can be shortened, and the total rotation angle can be arbitrarily increased. A video camera or the like can be configured.

〔The invention's effect〕

As described above, according to the present invention, the total rotation angle of the parallel flat transparent plate can be arbitrarily increased without changing the base lengths of the projection lens and the light receiving lens and the focus ring movement amount of the photographing lens, and the thickness is thin. As a result, it is possible to provide an automatic focus adjustment device that has superior functions over the conventional technology, such as a mechanism that has a simple structure, overall compactness, and greatly improved reliability. it can.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram showing an embodiment of an automatic focusing apparatus according to the present invention, FIG. 2 is a front view of a video camera as seen from the subject side, and FIG. 3 is a plane-parallel transparent plate in the automatic focusing apparatus. FIG. 4 is a side view for explaining the operation, and FIG. 4 is a front view showing a configuration example of a plane-parallel transparent plate. 1 ... Projection lens 2 ... Light emitting element 3 ... Light receiving lens 4 ... Light receiving element 5 ... Parallel plane transparent plate 5a ... Rotating shaft 5b ... Cam follower 5c ... Lever 6 ... Focus ring 7 ... Cam 8 …… Elastic member 9 …… Camera body 10 …… Subject 11 …… Shooting lens

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenji Sano Kenji Sano, 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Inside the Home Appliance Research Laboratory, Hitachi, Ltd. (72) Inventor Hironobu Sato 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Ceremony Company Home Appliance Research Laboratory, Hitachi, Ltd.

Claims (1)

[Claims] 1. A light emitting section comprising a projection optical system and a light emitting element, and a light emitting section comprising a light receiving optical system and a light receiving element, wherein a subject is irradiated with light emitted from the light emitting section, and the light is emitted from the subject. The reflected light of the above is received by the light receiving portion, and the photographing lens is extended according to the light receiving state of the reflected light at the light receiving portion to focus on the subject, and the light receiving optical system and the A parallel plane transparent plate is rotatably provided between the light receiving element and an axis perpendicular to a plane including the optical axis of the projection optical system and the optical axis of the light receiving optical system, and the parallel plane transparent plate is provided with the taking lens. In the automatic focusing device adapted to rotate in association with the feeding operation of, when a straight line orthogonal to the optical axis of the light emitting unit and the optical axis of the light receiving unit is a base line, the base line and the optical axis of the photographing lens are From the point where a straight line intersects with the baseline, The light emitting unit and the light receiving unit are arranged such that the distance from the point where the orthogonal line orthogonal to the optical axis of the taking lens intersects the base line to the optical axis of the light receiving unit is shorter than the distance to the optical axis of the light receiving unit. The automatic focus adjustment device is characterized in that.