JPS6150298B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an autofocus camera with interchangeable lenses, and in particular uses light from a subject passing through two areas symmetrical with respect to the optical axis at the periphery of an objective lens, and detects this light. The present invention relates to a focus status display device for a camera having an autofocus mechanism that obtains a focused point by moving a photographing optical system forward or backward in accordance with the output of a focus detection element.

As an automatic focusing system in a camera, as shown in FIG. The light passing through the holes a and b of the mask 3 is detected by the detection elements A and B arranged behind the focal position c of the objective lens 1.
(COD), and the photographing optical system is designed to eliminate the phase difference between the waveforms A' and B', which are formed by the output difference between the A group and B group of these elements, for example, as shown in Figure 1B. An autofocus method is known in which focusing is achieved by moving the lens forward and backward in the optical axis direction to match the deviations.

Specifically, a pinhole, slit, or
A pupil division optical system 4 such as a lenticular lens or a fly's eye lens is arranged, and a focus detection element is also installed.
Focus detection element group Ai, Bi, which is a pair of Ai and Bi,
Arrange A _i-1 , B _i-1 , ......, objective lens 1
so that among the imaging action rays 1, 1 passing through the A part and B part of the exit pupil of the lens, the light incident on the same part of the focus detection surface is incident on each corresponding element of the focus detection element Ai, Bi group. By doing so, when the objective lens 1 is focused in front or behind the focus position c, the contrast in brightness of the object 5 from areas A and B centered on the optical axis 2 of the objective lens 1 remains unchanged. A
As shown in the third figure, a difference in brightness appears in the light rays 1 and 1 that entered through the portions 1 and 1 with respect to each center, so a difference occurs in the outputs of the focus detection elements Ai and Bi groups, and the output difference As shown in Figure 4, the phase difference caused by
The deviation appears in the opposite direction from the Bi group. By focusing this in the directions of arrows A and B and moving the photographing optical system forward and backward by a motor or manually so as to align it with the in-focus position, focusing can be achieved according to the above-mentioned principle.

However, when the above autofocus method is applied to a single-lens reflex camera, the focus detection element
If the light rays 1, 1 passing through the peripheral parts A and B of the objective lens 1 that reach the Ai, Bi groups do not have a predetermined angle with respect to the optical axis 2, the focus detection elements Ai, Bi
Therefore, in the case of a lens with a large open F value, that is, a dark lens (F3.5 or less), the accuracy of focus detection deteriorates or becomes impossible.

Therefore, if a lens other than the one effective for the autofocus mechanism is mistakenly used, there is a risk that the image will be photographed with insufficient focus, which will likely result in a failure in photographing.

In view of this, the present invention identifies lenses capable of fully autofocusing, semi-autofocus lenses that require manual focusing, and lenses that cannot be autofocused, and uses the autofocus mechanism on the camera body side to distinguish between these lenses. The object of this invention is to provide a focus status display device for an autofocus camera, which automatically switches the display when attached to a camera body to prevent failures during photographing.

In order to achieve the above object, in the present invention,
In a camera equipped with an autofocus mechanism that guides a portion of the peripheral part of the incident light beam from the photographic optical system to a focus detection element and detects focus using these focus detection elements, the autofocus mechanism causes the focus to be focused. A signal member capable of distinguishing between a detectable lens and a lens whose focus cannot be detected is provided at the rear of the lens, and a responsive member is provided that responds to the signal member when the lens is attached to the camera body, and the movement of this responsive member is provided. Accordingly, whether or not autofocus is possible is displayed in the field of view of the viewfinder or its surroundings.

The present invention will be explained below with reference to FIGS. 5 to 8.

In the embodiment shown in the figure, a pin-shaped signal member 12 is provided protruding in the optical axis direction at the rear end of a lens 11 that is bright enough to enable automatic focusing by an autofocus mechanism installed on the camera body 10 side. A response member 14 is provided in the mount portion 13 on the side of the camera body 10, which engages with and responds to the signal member 12 when the lens 11 is mounted.

This responsive member 14 has a pointer 15 and is placed in a rest position (as shown) in the case of a lens without a signal member 12 (a dark lens in the example);
When engaged with the signal member 12 provided on a full auto focus lens or a semi auto focus lens, the signal member 12 is moved in the direction of the arrow in FIG. By changing the protrusion position, when a full auto focus lens is attached, the pointer 14 indicates full auto focus (FA) displayed in the viewfinder field of view 16, and when a semi auto focus lens is attached, the pointer 14 indicates full auto focus (FA). Focus (SA) is designated, and in the case of a lens without a signal member 12 (dark lens), manual (M) is designated.

As a modification of the display means, as shown in FIG.
7 may be engaged with each other so that the rotary pointer 19 indicates (FA), (SA), and manual (M) within the viewfinder field of view by means of an attached lens. Other display means can be selected as appropriate.

Further, by utilizing the movement of the response member 14, when it is placed in the full autofocus position (FA), the autofocus mechanism within the camera body 10 is activated, and the helicoid of the photographing optical system is driven by a motor. When placed in the semi-auto focus position (SA), only the focus display signal of the auto focus mechanism is displayed within the viewfinder field of view 16 to serve as a focus instruction during manual focusing. Manual display (M)
When the camera is in this position, all autofocus mechanisms may be turned off so that it can be used as a manual camera.

In FIG. 8, the display in the viewfinder by the response member 14 is changed to a lighting display using a lamp, LED, etc. In this embodiment, a part of the signal member 12 or response member 14 is moved on the sliding resistor 21, and the The electrical signal conversion circuit 22 is operated to turn on any one of full autofocus (FA), semi-autofocus (SA), and manual (M).

As described above, the present invention provides a signal member on the lens side for identifying an autofocusable lens and a non-autofocusable lens, a response member that responds to the signal member on the camera body side, and a signal member that responds to the signal member on the camera body side. Since the response member that is activated by the member displays whether or not the attached lens is capable of auto-focusing in the viewfinder, when a lens that cannot be focused by the auto-focusing mechanism is attached, there is no possibility of accidentally accidentally focusing the lens. It is possible to prevent photos from being taken with the intention of autofocus,
Failures due to misuse can be reliably prevented.

[Brief explanation of the drawing]

1A, B to 4 are diagrams explaining the principle of an example of the autofocus method used in the present invention,
FIG. 5 is a perspective view showing an embodiment of the present invention, FIG. 6 is an explanatory view showing an example of a focus display device, FIG. 7 is an explanatory view showing another modification, and FIG. It is an explanatory view showing another modification. 1... Objective lens, 2... Optical axis, 3... Mask, 4... Pupil division optical system, 5... Subject, Ai,
Bi... Focus detection element, 10... Camera body, 11
... Lens, 12 ... Signal member, 13 ... Mount, 14 ... Response member, 15 ... Pointer, 16 ...
Finder visual field.

Claims (1)

[Claims] 1 An automatic system that guides the incident light that passes through two areas symmetrical with respect to the optical axis at the periphery of the objective lens to a focus detection element, and obtains focus by moving the photographing optical system forward and backward according to the output of this focus detection element. In a camera using a focus mechanism, a signal member is provided at the rear of the lens to identify a lens whose focus can be detected by the autofocus mechanism and a lens whose focus cannot be detected. A focus availability display device for an autofocus camera, which is provided with a responsive member that responds to a signal member, and displays whether autofocus is possible in or around the viewfinder field of view by the movement of the responsive member.