JPH0358043A - camera - 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] [Industrial Field of Application] The present invention is directed to the arrangement of a finder system as a distance measuring system of a camera, and in particular to a distance measuring system that is configured separately from a photographic lens system. Concerning a rangefinder without parallax in the viewfinder field of view. [Prior art] The finder system of a camera, which is relatively advantageous in terms of miniaturization and cost reduction, is a so-called external finder in which each optical axis is placed apart from the optical axis of the photographic lens. Generally, it is structured as a system. However, this type of camera is different from a single-lens reflex camera, which measures the shape of the viewfinder's field of view and distance based on the photographic light flux that passes through the photographic lens, and has the disadvantage that distance measurement variation is likely to occur. Therefore, for example, in the so-called active-o1 focusing method, which projects a distance measuring beam from outside the photographic lens onto an object and detects the position of the reflected beam to measure the distance, a distance measuring beam is sent to the moving lens in the photographic lens. For example, Japanese Patent Laid-Open No. 169026/1984 proposes a technique in which the direction of light projection is changed by changing the projection direction to prevent parallax from occurring in the field of view.

By the way, in recent years there has been a trend to include built-in lenses that can shoot up to the telephoto end, such as bifocal switching lenses or zoom 1/lens lenses. As a result, there are cases where distance measurement is not possible for distant objects.

The so-called passive autofocus method, which performs focus detection using only external light (natural light), is being reconsidered. Even in video cameras, higher resolution has been achieved due to improvements in the technical level of photographic elements and circuit processing systems.As a result, improvements in focal point accuracy have been required, and the passive autofocus method has been changed from the active autofocus method for small cameras. It's coming.

[Problems to be Solved by the Invention] However, the above-mentioned passive autofocus camera, which is a small camera, generally has two objective lenses located apart from each other by a predetermined baseline length, while a finder system is arranged separately. Therefore, there will basically be distance measurement variation in the viewfinder field of view.

SUMMARY OF THE INVENTION In view of these problems, it is an object of the present invention to provide a passive type distance measurement system that does not have distance measurement parallax in the viewfinder field of view.

[Problems to be Solved by the Invention] Therefore, the present invention provides a viewfinder system for observing an image formed by an objective lens provided separately from a photographing lens system, and a plurality of pupil-divided objective lenses. The photographic lens is equipped with a detection means for detecting a focus state from the correlation of the images, and the focus of the photographing lens is adjusted based on the detection result of the detection means.

[Examples] Examples of the present invention will be described below with reference to the drawings. 1st
In the figure, 1 is a focusing lens group of the photographic lens system, 2 and 3 are variator lens groups that have a variable power function by controlling the variable power section of the photographic lens system, and Each convenser lens group compensates for the image plane movement, and moves in the traces of arrows when zooming from the wide-angle side to the telephoto side. 4 is an aperture, 5 is a relay lens group with an imaging function, 6 is a parallel plate member including an optical low-pass filter and an infrared cut filter,
7 is a CO that converts the optical image of the imaging system into an electrical video signal.
It is a D sensor. 8.9 has a first lens group with a negative refractive power and a positive refractive power, which constitutes the objective lens of the finder system and the distance measuring system. An image is formed on the primary imaging plane 11 by the J2 1/lens group. Note that when zooming from the wide-angle side to the telephoto side, the lens moves in a trajectory shown by an arrow. 10
is a primary filled lens placed near the primary imaging plane 11.

12.13 are the first and second mirrors for bending the light beam from the finder and guiding it to the eyepiece side; the first mirror 1
2 is guarded by a half mirror, while the second mirror 13
is made up of mirror surfaces.

14 is a secondary imaging lens for re-forming an image on a secondary imaging plane 16, 15 is a second field lens, and 17 is an eyepiece lens. 18, 19, and 20 are focus detection devices that detect the focus state by dividing the pupil of the objective I nons (8.9) into a plurality of parts.
A pair of line sensors (19a, 19b) corresponding to each image position of the next imaging lens, and arithmetic processing based on the output signal of this line sensor to detect the focus state and driving the focusing lens group 1. Control circuit 2 to control
Consists of 0. Reference numeral 21 denotes a driving means for driving the focusing lens group 1 according to the focus adjustment amount output from the arithmetic circuit. Note that the first field lens 10 is a secondary imaging lens 14.
A pair of secondary imaging lenses (1
8a, 18b). It has the role of focusing light. Here, a pair of secondary images I are formed for the first field lens 10.
The position of the non-lens (18a, 18b) is optically slightly different from that of the secondary imaging lens 14, but since the distance measurement field of view is limited to the vicinity of the center of the viewfinder field of view, the first field lens 10 has only one pair. secondary imaging lenses (18a, 18b)
It can be said that it performs a sufficient light-concentrating function even for light.

Further, a distance measurement field display mark 1lb as shown in FIG. 2 is engraved on the primary focus surface side 11 of the first field lens 10 to indicate the distance measurement field to the user.

Next, the flow of the ranging system will be explained with reference to FIG. The control circuit 20 receives the signals of the two images formed on the pair of line sensors 19a and 19b, calculates the focal position, and based on the calculation result, controls the focusing lens 1 of the photographing lens via the drive device 21. Drive and focus.

Focusing in the finder system is performed by mechanically interlocking the first lens 8 with the focusing lens 1 of the photographing lens. The focal state is a pair of secondary imaging lenses 18a.
, 18b, a pair of line sensors 19, 19b are confirmed through the control circuit system 20, and if the in-focus state is not achieved, the focusing lens 1 and the first lens 8 are driven via the focusing drive device 21. Ru. When this is repeated and it is confirmed that the focus is in focus, it becomes clear that the lens is 1'B! ．． and the first lens 8 is stopped. This operation completes the preparation for photographing the shot. FIG. 2 shows the field of view arranged near the primary focus plane 11. In the figure, LLa indicates a finder field frame, Ilb indicates a distance measurement field frame, and Lie indicates a short distance correction mark.

According to the configuration as explained above, the finder system is placed at a certain distance from the photographic lens system, which causes parallax as shown by the short distance correction mark llc, but the distance measuring system is located at a certain distance from the photographic lens system. Since it is shared with the objective lens system of the system, the distance measurement field mark is always within the viewfinder field of view regardless of the zoom setting or shooting distance. Accurate focus detection can be performed for the subject 11b.

In other words, focus can always be detected without parallax in the observation field of view. Also, since it uses a passive auto autofocus system, it can demonstrate sufficient range-finding ability even for distant subjects. FIG. 3 is a view of a flat type camera with a long depth, incorporating the finder and AF system of the present invention, as seen from the subject side. In the figure, 30 is the camera, 31 is the photographing lens,
2 is a finder, 33 is a photometric lens, and 34 is a strobe window. As shown in the figure, since there is no AF lens, a simple design can be realized.

[Effects of the Invention] As explained above, by arranging the pupil-splitting passive autofocus system within the external finder system, it is possible to always detect focus without parallax for the finder system, and the focus is comfortable to the user. It has the effect of being able to be matched.

Furthermore, since the AF lens disappears from the front of the camera, we can expect a side effect of creating a cleaner design.

Additionally, since the focus is adjusted according to the subject distance, it is possible to always keep the viewfinder diopter adjusted.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing contents displayed in the viewfinder field of view, and FIG. 3 is a diagram showing an example of the design of a flat plate type camera. 1 is a focusing lens of the photographic lens, 2 is a variator, 3 is a convencator, 4 is an aperture, 5 is a relay lens, 6 is a parallel plane plate, 7 is a CCD sensor, 8 is a first lens group, 9 is a second lens group , 10 is a first field lens, 12 is a half mirror, 13 is a total reflection mirror 14 is 2
A secondary imaging lens, 15 is a second field lens, 17 is an eyepiece lens, j8a, 18b are a pair of secondary imaging lenses,
19a and L9b are a pair of line sensors, 19c is a dead zone, 20 is a control circuit system, and 2l is a focusing lens drive device.

Claims (3)

[Claims] (1) A finder system for observing an image formed by an objective lens provided separately from the photographic lens system; and a detection means for detecting a focus state based on light related to the objective lens; A camera characterized in that focus adjustment of the photographic lens is performed based on the detection result of the means. (2) The camera according to claim 1, wherein the detection means is means for detecting a focal state from a correlation between a plurality of images formed by dividing the objective lens into pupils. (3) The finder system includes, after the image plane formed by the objective lens, two reflective mirrors that bend the optical path;
An automatic focus detection device according to claim 1, characterized in that it comprises a secondary imaging lens and an eyepiece lens.