JPH02267507A - Automatic focusing device - Google Patents

Abstract

PURPOSE:To always eliminate the parallax even if a distance of an object to be photographed is varied by providing a prism in front of a projection optical system, and varying a prism fitting angle in accordance with a focus ring. CONSTITUTION:In front of a light emitting element 34 and a projection lens 35, a prism 36 is placed, connected to a focus ring 30 by a lever 39, and the focus ring 30 rotates and slides forward and backward, by which the prism 36 turns centering around a fulcrum 31. Therefore, an angle (angle theta) made by a straight line vertical to base length and a focus lens optical axis, and a projection light beam can be varied. Accordingly, since the projection light beam 37 is set so as to be always on the focus lens optical axis 32, the parallax on this plane always is eliminated.

Description

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

[Prior Art] An automatic camera that has a light emitting section consisting of a projection optical system and a light emitting element, and a light receiving section consisting of a light receiving optical system and a light receiving element, and performs automatic focusing by receiving reflected light from a subject. Various focusing devices have been proposed, for example, Japanese Patent Application Laid-Open No. 62-264014.
In the publication, a deflection means is provided between a light receiving optical system and a light receiving element to achieve automatic focusing. FIG. 1 is a plan view of an embodiment of a conventional automatic focusing device, and the invention relates to an automatic focusing operation within a plane including the base line length a and the focus lens optical axis 14, and the plane shown in FIG. It becomes.

FIG. 2 is a side view of one embodiment of the conventional automatic focusing device, in which the light beam emitted from the light emitting element 26 becomes the projection light beam 24 through the projection lens 25 and travels toward the object. When , the amount of deviation between the focus lens optical axis 22 and the projected light beam 24 (hereinafter referred to as balarax) is P8, and when the subject distance is Xii r-2, balarax is P2. In Fig. 2, if the projection lens 25 and the light emitting element 26 are aligned with the focus lens optical axis 22, the vararax will disappear, but in both Figs. If you try to do this, you will have to use an internal light emitting method that has a light emitting part inside the photographic lens, and if you use an external light emitting method in which the light emitting part is outside the photographic lens, variation will inevitably occur within the plane of Figure 1 or 2. do.

[Problem that the invention seeks to solve]

In the above-mentioned conventional technology, there was a problem in that an external light-emitting autofocus device in which the light-emitting part was located outside the photographic lens produced a parallax as shown in FIG. The object of the present invention is to provide an automatic focusing device with no or a small number of automatic focusing devices.

[Means for solving problems]

The above purpose is to provide deflection means for the projection light beam in front of the light emitting element or the projection optical system, and to adjust the angle (angle θ shown in FIG. 2) between the projection light beam and a straight line perpendicular to the base length and the focus lens optical axis. This is achieved by causing the deflection means to move together with the movement of the focus lens so as to change the focus.

[Effect]

The deflection means moves so as to change the angle θ shown in FIG. 2, and does not change the angle of the ray within the plane shown in FIG. 1, so it does not adversely affect the automatic focusing operation. .

〔Example〕

Three embodiments of the present invention will be described below with reference to FIGS. 3 to 8. FIG. 3 is a side view of the first embodiment of the automatic focusing device according to the present invention, showing a straight line perpendicular to the base length and the focus lens optical axis, and a plane including the focus lens optical axis. In FIG. 3, light emitted from a light emitting element 34 passes through a projection lens 35, is deflected by a prism 36, becomes a projection beam 37, and travels toward a subject 33. As the subject distance L changes, the light is focused by a natural focusing device. The prism 36 is connected to the focus ring 30 by a lever 39 as the ring 30 rotates and the focus ring 30 moves back and forth by a helicoid screw. By rotating the focus ring 30 and moving back and forth, the prism 3
6 rotates around a fulcrum 31. This prism 36
The rotation is set so that the position at which the projected light 41137 hits the subject 33 is always on the focus lens optical axis 32 even if the subject distance L1 changes, that is, there is no variation. The prism 36 projects light l!
What is the angle θ that 37 makes with the focus lens optical axis 32 in the plane shown in FIG.

When the balax is zero, it is expressed by the following equation.

θ□= j an−1 L However, L: Subject distance L: The distance angle θ1 between the focus lens optical axis 32 and the projection lens optical axis 38 in the plane shown in FIG. From the formula, when the subject distance L changes,
Each is uniquely determined for Lo.

The angle φ is an angle determined by the positional relationship between the light emitting element 34 and the projection lens 35, and if the angle α between the prism 36 and the projection lens optical axis 38 is set to a certain value, the angle θ is determined from θ1 determined from the above equation. It is assumed that the settings are set so that it can be obtained. Once the angle θ and the angle ψ are determined, the angle α for the prism 36 whose apex angle and refractive index are determined is also determined 6
As described above, even if the subject distance ri changes, by rotating the prism 36 accordingly and setting the angle α to a predetermined value, the intersection of the projected light ray 37 and the subject 33 can be aligned on the focus lens optical axis 32. Therefore, it is possible to provide an automatic focusing device that is free from variation and deviation within the third national plane. FIG. 4 shows a configuration diagram of this first embodiment. A spring 44 is used to keep a portion of the lever of the prism 43 always in contact with the focus ring 41 without play.

Next, a second embodiment of the present invention will be explained with reference to FIGS. 5, 6, and 7. FIG. 5 is a side view of a second embodiment of the automatic focusing device according to the present invention, in which light emitted from a light emitting element 51 passes through a projection lens 52, reaches a mirror 53, and is reflected there, reaching an object. The mirror 53 is brought into contact with the focus cam 56 by the lever 55 without play due to the force of the spring 54. The focus cam 56 moves back and forth by one rotation in accordance with the rotation and back and forth movement of the focus ring 57.
It is connected to 7. FIG. 6 is a front view of a second embodiment of the automatic focusing device according to the present invention, including a light emitting element 61 and a projection lens 62.
, a distance detection optical system consisting of a light-receiving element 64 and a light-receiving lens 65 detects the object distance, and automatically focuses by moving the focus ring 66.
The structure is such that a change in object distance is detected by a distance detection optical system, the focus ring 66, 57 and focus cam 56 move, and the mirror 53 rotates.

How to rotate the mirror according to changes in the subject distance will be explained with reference to FIG. FIG. 7 is a diagram schematically showing the same side view as FIG. 5, in which light emitted from a light emitting element 71 passes through a projection lens 72, is reflected by a mirror 73, and reaches a subject 74. The angle θ between the projected light beam 76 and the focus lens optical axis 77 is determined by the distance L2 between the subject distance and the mirror and the focus lens optical axis 77.
It is expressed by the following formula.

θ = t an-' ・・・・・・ ■L
.

Assuming that the angle β between the projection lens optical axis and the focus lens optical axis 77 is the angle β, the incident light ray angle to the mirror and the reflected light ray angle ψ are expressed by the following formula.

Letting α be the angle between the normal line of the mirror and the focus lens optical axis 77, α is expressed as follows.

α= 180＠−ψ−β・・・・・・ ■Since the angle β is set in advance, the formulas ■,■
, ■, the angle α is uniquely determined. Therefore, if the mirror 73 is rotated so that the angle α obtained from formulas ■, ■, and
The intersection point always intersects on the focus lens optical axis within the 7th national military plane (a plane that includes the focus lens optical axis and a straight line perpendicular to the focus lens optical axis and the base line length), so within the 7th national military plane It can be an automatic focusing device with zero vararax.

Next, a third embodiment of the present invention will be described with reference to FIG. 8th
The figure is a side view of an automatic focusing device according to a third embodiment of the present invention, in which a light emitting element 83 emits light representing a plane including the focus lens optical axis and a straight line perpendicular to the focus lens optical axis and the base line length. The light is transmitted to the parallel plane plate 84 and the projection lens 85.
The reflected light is detected by a light receiving lens and a light receiving element to detect the distance, and the focus ring 81 is rotated and moved back and forth to achieve automatic focusing. The focus cam 82 is connected to the focus ring 81, and as the focus ring 81 rotates and moves back and forth, the focus cam 82 also rotates and moves back and forth. Parallel plane plate 84
The lever 80 is brought into contact with the focus cam 82 without play by a spring or the like, so that the parallel plane plate 84 rotates as the focus cam 82 rotates and moves back and forth. That is, the structure is such that the focus ring 81 moves due to automatic focusing as the subject distance changes, and the parallel plane plate 84 rotates. Subject distance L1, focus lens optical axis 87
Letting the distance Ili between the projection lens optical axis 88 and the projection lens optical axis 88 be L2, the angle θ between the projection light beam 89 and the focus lens optical axis 87 is expressed by the following formula.

L.

θ=tan″″1 ...... ■Light emitting element 83
The emitted light passes through a plane-parallel plate 84 tilted by an angle α, deviates from the projection lens optical axis 85 by d, and enters the projection lens 85 in parallel to the projection lens optical axis 88. At this time, if the focal length of the projection lens is f, the relationship with the angle θ is expressed by the following formula.

θ: tan-1... ■Furthermore, the relationship between d and angle α is uniquely determined from the refractive index and thickness of the parallel plane plate. Therefore, when the subject distance L1 changes, ■,■
By tilting the parallel plane plate 84 by an angle α that gives d determined by the formula, the intersection between the projected light ray 89 and the subject 86 is always on the focus lens optical axis 87, and automatic focusing with zero parallax is achieved within the eighth national plane. It can be a device.

It should be noted that, as common to all three embodiments of the present invention, the angle θ in FIG. 8, the angle θ in FIG. 7, and the angle θ1 in FIG. 3 change as the subject distance changes. In the conventional automatic focusing device, the angle (90° θ) shown in Fig. 2 does not change, so in all three embodiments of the present invention, the angle of the reflected light from the subject is the same as that shown in Figs. 8 and 7. However, as shown in the mirror 63 in FIG. 6 and the prism 43 in FIG. If the deflection means covering the light-receiving section is used to reverse the angle change of the light beam made by the deflection means in one light-emitting section, the incidence of the light beam on the light-receiving element will be different from that of the conventional method. Since it can be done in the same manner as above, there is no negative effect on distance detection and automatic focusing.Also, if the size of the light receiving part of the light receiving element is made sufficiently large in the direction perpendicular to the base line length, the deflection means described above can be used. Distance detection and automatic focusing can be performed in the same way as before without covering the light receiving section.

〔Effect of the invention〕

According to the present invention, the intersection point between the projected light beam emitted from the light receiving section of the distance detection optical system and the subject is located within the plane including the focus lens optical axis, a straight line perpendicular to the focus lens optical axis and the base length, and the subject. Since the focus lens can always be on the optical axis even if the distance changes, there is an effect that the parallax within the plane can always be zero.

[Brief explanation of drawings]

Figure 1 is a plan view of an embodiment of a conventional automatic focusing device;
The figure is a side view of one embodiment of a conventional automatic focusing device, FIG. 3 is a side view of a first embodiment of an automatic focusing device according to the present invention, and FIG.
The figure is a configuration diagram of a first embodiment of an automatic focusing device according to the present invention.
FIG. 5 is a side view of a second embodiment of the automatic focusing device according to the present invention, FIG. 6 is a front view of the second embodiment of the automatic focusing device according to the present invention, and FIG. 7 is an automatic focusing device according to the present invention. FIG. 8 is a side view of a second embodiment of the device, and FIG. 8 is a side view of a third embodiment of the automatic focusing device according to the invention. 11: Focus lens, 12: Light emitting element, 13: Projection lens, 14: Projection light beam, focus lens optical axis, and projection lens optical axis. 15: Light receiving lens optical axis, 16 Two reflected rays, 17: Light receiving lens, 18: Parallel plane plate, 19: Light receiving element, 21: Focus lens, 22: Focus lens optical axis, 23: Projection lens optical axis, 24: Projection Ray, 25: Projection lens, 26: Light emitting element. 30: Focus ring, 31: Fulcrum, 32: Focus lens optical axis, 33: Subject, 34: Light emitting element, 35:
Projection lens, 44: 56: 58: 62: 64: 66 Near 2 Near 4 Near 6: 81: 83 Niprism, 37: Projection light beam, Projection lens optical axis, 39 Nilever photographic lens, 41: Focus ring, distance detection optical system , 43 Nibrism, Spring, 45: Dedicated, 46: Stopping member, Light emitting element, 52: Projection lens, 53: Mirror 54: Spring, 55 Nilever focus cam, 57: Focus ring, Photographing lens, 6
1: Light-emitting element, projection lens, 63: Mirror light-receiving element, 65: Light-receiving lens, focus ring, 71: Light-emitting element, projection lens, 73: Mirror object, 75: Focus ring, projection light beam, 77: Focus lens optical axis, Focus ring, 82: Focus cam, light emitting element, 84: Parallel plane plate, 86: Subject, 85: Projection lens, 87: Focus lens optical axis, 88: Projection lens optical axis.

Claims (1)

[Scope of Claims] 1. A light-emitting section comprising a projection optical system and a light-emitting element and projecting a light beam onto a subject; and a light-receiving section comprising a light-receiving optical system and a light-receiving element and receiving reflected light from the subject. In the automatic focusing device, the automatic focusing device includes an optical system that detects a distance by using the light emitting element or the projection optical system, and a drive device that moves the focus lens according to the distance detected by the optical system. Deflecting means for the projected light beam is provided, and the deflecting means deflects the focused beam so as to change the angle formed by the projected light beam and a straight line perpendicular to the base length of the light emitting element and the light receiving element and the optical axis of the focus lens. An automatic focusing device that moves with the movement of the lens. 2. The automatic focusing device according to claim 1, wherein said deflection means is a prism. 3. The automatic focusing device according to claim 1, wherein said deflection means is a mirror. 4. The automatic focusing device according to claim 1, wherein said deflecting means is a parallel plane plate.