JPH02267509A - Automatic focusing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improving the focusing performance of an automatic focusing device suitable for use in video cameras, movies, etc.

[Prior art] Conventional automatic focusing devices emit a light-emitting spot image from a light-emitting element toward a subject, and the reflected light is received by a light-receiving part, and the distance to the subject is determined by the light-receiving state of the light-receiving element. There are devices that detect and automatically focus on the subject.

Since the optical axis of the light emitting part of the cutting device is generally different from the optical axis of the photographing lens, the emitted light (hereinafter referred to as the light emitting spot) should be placed at the center of the photographing screen at the center of the photographing angle of view for all photographing distances. is not possible.

In general, the majority of systems emit light parallel to the optical axis of the photographic lens. However, during close-up shooting, the light emitting spot is projected at a position far away from the center of the shooting screen. As a result, a problem arises in that even if the subject to be photographed is placed in the center, it is not in focus.

An example of this prior art is Japanese Patent Laid-Open No. 57-20708. In addition, as a patent related to this case, Japanese Patent Application Laid-Open No. 63-757
There is Publication No. 17.

[Problem to be solved by the invention]

In the above-mentioned conventional technology, one light emission spot image does not coincide with the center of the photographing lens field of view at all subject distances.

That is, there is a problem in that parallax occurs, and the parallax becomes large, especially in close-up photography, and the object in the center of the screen cannot be brought into focus.

An object of the present invention is to provide an automatic focusing device that can reduce the parallax as much as possible.

[Means to solve the problem]

In order to achieve the above object, the light emitting element of the light emitting part and the light receiving element of the light receiving part are made into a mechanism that can simultaneously move perpendicular to the optical axis, and the above mechanism part is made to be able to be linked with the movement of the focus lens. .

[Effect]

Since the light emitting element position changes with the movement of the focus lens, the light emitting spot position is projected near the center of the photographic screen according to the photographing distance of each photographing lens. Furthermore, the light-receiving element also moves in the same way as the light-emitting element, so that the light-receiving optical system is also set at an accurate position. Thereby, the parallax between the optical axis of the light emitting section and the photographing lens can be greatly reduced.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a schematic structural diagram of the present invention, in which 4 is a light emitting element, 1 is a projection lens, 2 is a light receiving lens, 5 is a light receiving element, 6 is a focus ring with a built-in focus lens, and 9 is provided in a focus 1516. The first cam 3 represents a transparent deflecting member which is interposed between the light receiving lens 2 and the light receiving element 5 and is rotatable about a fulcrum 11, and the deflecting member is made of, for example, a parallel plane transparent plate. First cam 9 and deflection member 3
are in contact with each other by a spring 14 so as to maintain a constant relationship. Reference numeral 8 denotes an autofocus circuit that determines the in-focus state based on the amount of light received by the light receiving sensor 5 and controls the focus ring 6 via the autofocus motor 7.

In the figure, automatic focusing operation will be explained.

The light emitted from the light emitting element 4 is transmitted through the projection lens 1 to the subject 9.
to be projected. This projected light is reflected by the object, and this reflected light is transmitted to the light receiving lens 2. The light is guided to the light receiving element 5 via the deflection member 3. The light receiving state of this light receiving element 5 is determined by a 5-oto focus circuit 8.

The light receiving element 5 is a two-part light receiving element, and outputs a signal corresponding to the amount of reflected light received by each photoelectric conversion element. These signals are supplied to the autofocus circuit 8, from which a signal corresponding to the difference in the amount of received light is formed. This signal drives the autofocus motor 7, rotates the focus ring 6, and moves the focus lens 6a in the optical axis direction.

As the focus ring 6 rotates, the deflection member 3 rotates along the first cam 9, and the light receiving state at the light receiving element 5 changes. When a specific light receiving state is reached in which the amounts of reflected light received by the two photoelectric conversion elements of the light receiving element 4 are equal, the autofocus motor 7 stops, the focus ring 6 also stops, and an automatic focusing state is achieved. It should be noted that this automatic focusing device and its automatic focusing operation are known, for example, from Japanese Patent Laid-Open No. 75717/1983, so a detailed explanation thereof will be omitted.

The light emitting element 4 and the light receiving element 5 are attached to a frame 12 so as to be movable about a shaft 13 in a direction perpendicular to each optical axis. The frame 12 is interlocked with the second cam IO set on the focus ring 6 by a spring 15 so as to maintain a constant relationship. FIG. 2 is a three-dimensional view of the automatic focusing device.

FIG. 3 shows the locus of the light ray when the position of the light emitting spot of one light emitting element 4 is set parallel to the optical axis of the focus lens 6a. In this case, Z parallax occurs for each distance. However, the subject is 121→Q2→Q.

As the distance becomes shorter, the parallax from the center of the photographing lens increases with respect to the angle of view G in FIG. 4, causing a phenomenon in which the object deviates from the angle of view. FIG. 4 shows the position of the light emitting element when viewed from direction A. When setting a light emitting spot near the optical axis (04' to 03') of the photographing lens for each subject from Q to Q3, it is necessary to change the light emitting position as shown in R, R,, R3. Become. The position Ro is the case where the subject is at an infinite position. If we consider Q3 as the closest,
Assuming that the distance between the focus lens optical axis and the projection lens optical axis is 2, the change angle θ of the light emitting element 4 is defined as follows.

Z θ:=tan-”() Also, since one light-emitting part changes as shown in θ above, the light-receiving part also needs to change by the same amount at the same time. This is why the light receiving element 2 is simultaneously rotated by the frame 12.

What has been described above is the parallax with the photographic lens viewed from six directions, but in reality, parallax in the B direction also occurs.

This parallax with the photographic lens is very small compared to the Z-direction component, and does not pose much of a problem even at close range.

(Effects of the Invention) According to the present invention, it is possible to arrange a light-emitting spot approximately in the center of the shooting angle of view for each subject, and even at close range, the light-emitting spot is illuminated near the center of the angle of view. Therefore, it has the effect of being able to focus on subjects placed in the center.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of an automatic focusing device according to the present invention, FIG. 2 is a three-dimensional view thereof, FIG. 3 is a light emission ray tracing diagram of a conventional automatic focusing device, and FIG. 4 is an A FIG. 4 is an improved side view of ray tracing from a directional perspective; DESCRIPTION OF SYMBOLS 1... Projection lens, 2... Light receiving lens, 3... Polarizing member, 4... Light emitting element, 5... Light receiving element, 6...
・Focus ring, 9...1st cam, 10...2nd cam, 12...frame

Claims (1)

[Claims] It consists of a projection optical system and a light-emitting element, and consists of a light-emitting part that irradiates light onto a subject, a light-receiving optical system, and a light-receiving element, and a light-receiving part that receives reflected light from the subject, and a light-receiving part that A polarizing means for the reflected light received is provided between the light-receiving optical system of the automatic focusing means for controlling the focusing lens and the light-receiving element, and an automatic method for changing the reception state of the reflected light at the light-receiving element. In the focusing method, the emitted light emitted from the light emitting unit is emitted to the center or near the center of the angle of view of the photographing lens, so that the reflected light from the subject can be received.
An automatic focusing device characterized in that the light emitting element and the light receiving element are moved in conjunction with the focusing lens.