JPH04340940A - Camera optical system - Google Patents

Abstract

PURPOSE:To correct parallax(deviation of an object image) and simultaneously to obtain sufficient brightness in the case of observation through a finder and photographing by a photographing lens in a camera optical system provided with a finder system separately from the optical axis of the photographing lens. CONSTITUTION:This system is constituted of a parallel plate 2 arranged at a specified angle ahead of the photographing lens 1, a total reflection mirror 4 which totally reflects a luminous flux reflected by the plate 2, and a finder lens 5 arranged on the optical axis of the luminous flux reflected by the mirror 4, and the parallel plate is set so that the transmissivity and the reflectance of light are changed in the case of turning off a shutter and turning on the shutter by controlling an electrical signal.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] This invention relates to a camera optical system in which a finder is provided in a part of a photographic lens barrel in parallel with the photographic optical path, in addition to the photographic optical path, and in particular corrects parallax of the finder. The invention relates to a camera optical system.

0002

[Prior Art] In general, in a lens-shutter camera optical system in which the optical axis of a photographing lens that images a subject on film and the optical axis of a finder lens that observes a subject do not coincide with the subject, the shooting range is from infinity to close range. Parallax occurs over the entire area between the subject image captured on the film and the subject image observed through the finder.

[0003] This occurs because the optical axis of the photographing lens and the optical axis of the finder lens do not match, and the amount of occurrence increases as the photographing magnification increases and the photographing distance decreases. For example, in a single-lens reflex camera, the optical axis of the photographing lens and the optical axis of the finder lens are aligned, so parallax does not occur in principle.

In conventional lens shutter cameras, in order to correct this parallax, a parallax correction mark is provided within the field frame of the finder. for example,
In the finder field of view shown in FIG. 7, a mark 22 for checking the composition of a subject 2 m or less away is newly provided in the viewfinder field 20 based on the field frame 21 for checking the composition of a subject 2 m or more away, for example, This corrected parallax. However, with this method, the mark is always displayed in the viewfinder field of view, making it very difficult to see the viewfinder image, and the relative relationship (positional relationship) between the background or foreground and the target subject cannot be seen through the viewfinder. It will be different from what you observed.

Therefore, in Japanese Patent Application Laid-Open No. 2-54222, a half mirror is attached as an accessory to align the optical axes of the viewfinder and the photographing lens to prevent the occurrence of parallax during close-up photography where parallax is likely to occur. A method is disclosed. Also, JP-A-2-
Japanese Patent No. 54221 discloses a method for correcting parallax by arranging a removable half mirror member in front of a photographic lens.

[0006]

[Problem to be Solved by the Invention] However, the former of the above-mentioned conventional camera optical systems for correcting parallax cannot support all photographic magnifications, and also requires carrying and wearing accessories. The drawback was that it was troublesome. In addition, in the latter of the above conventional examples, since a half mirror is simply arranged,
There was a problem in that the amount of light from the object was reduced to 1/2 to the finder lens and 1/2 to the photographic lens, making it darker than a conventional finder lens, making it difficult to see the object during observation. Furthermore, since the amount of light in the photographic lens is always 1/2 compared to the normal F/NO, there is a problem that it is difficult to obtain a bright photographic lens because it is in a one-step aperture state.

Therefore, the present invention solves the above-mentioned conventional problems, does not reduce the brightness of the finder or photographic lens, does not cause inconvenience in attaching and detaching, and prevents the occurrence of parallax. Our goal is to provide a camera optical system that can.

[0008]

[Means for Solving the Problems] The gist of the present invention is that in the invention of claim 1, a parallel plate disposed in front of a photographic lens at a predetermined angle with respect to the optical axis of the photographic lens; A total reflection mirror for the light beam reflected by the parallel flat plate,
A camera optical system comprising a finder lens disposed on the optical axis of the light beam reflected by the total reflection mirror,
The parallel plate has a light transmittance of approximately 0% (reflectance of approximately 100%) when the shutter is off and approximately 100% (reflectance of approximately 100%) when the shutter is on by controlling the input of electrical signals. The feature is that the reflectance is approximately 0%). In the invention of claim 2, a parallel plate arranged in front of the finder lens at a predetermined angle with respect to the optical axis of the finder lens, and a total reflection mirror that totally reflects the light beam reflected by the parallel plate; The camera optical system includes a photographing lens placed on the optical axis of the light beam reflected by the total reflection mirror, and the parallel plate controls the light output when the shutter is off by controlling the input of an electric signal. The light transmittance is approximately 100% (reflectance is approximately 0%), and when the shutter is on, the light transmittance is approximately 0% (reflectance is approximately 100%).

[0009]

Therefore, in claim 1, when the shutter is off, since the light reflectance of the parallel plate is approximately 100%, sufficient light is guided to the finder lens, allowing bright observation. Furthermore, when the shutter is on, the light transmittance of the parallel plate is approximately 100%, so most of the incident light flux of the subject is guided to the photographing lens, making it possible to obtain the brightness necessary for photographing. In addition, in claim 2, the control of light in the parallel plate is opposite to that in claim 1, and when the shutter is off, the light transmittance of the parallel plate is approximately 100%, and sufficient light is guided to the finder lens. When the shutter is on, the reflectance of light on the parallel plate is approximately 100%, so most of the light beam incident on the subject is guided to the photographic lens.

0010

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIGS. 1 and 2 showing the invention of claim 1,
In front of the photographic lens 1, a parallel plate 2 whose transmittance and reflectance can be arbitrarily changed by an output signal from an external electric circuit (not shown) is inclined at a predetermined angle θ with respect to the optical axis A of the subject 6. It is located. The photographing lens 1 is placed on the optical axis B of the light beam transmitted through the parallel plate 2, and the film 3 is placed behind it. On the other hand, behind the optical axis C of the light beam deflected and reflected at the predetermined angle θ by the parallel plate 2, a total reflection mirror 4 making an angle α with respect to the optical axis C is arranged, and further behind that A finder lens 5 is arranged at.

[0011] Regarding the positional relationship between the parallel plate 2 and the total reflection mirror 4, a predetermined angle θ that determines their arrangement is determined.
and α can be set freely, for example α=θ=45°
If set to , optical axis B and optical axis C become parallel. Also,
The parallel plate 2 and the total reflection mirror 4 must have a size that includes the width of the incident light beam (not shown).

In the above configuration, light from the subject 6 is incident on the parallel plate 2. At this time, in the viewfinder observation state, the light reflectance of the parallel plate 2 is close to 100%, and most of the incident light flux reaches the finder (finder lens 5), allowing bright observation of the subject 6. That is, as shown in FIG.
It has a characteristic that the transmittance and reflectance change depending on the strength of the input signal level, and as shown in Figure 4 (solid line),
The input signal level is set in conjunction with the shutter so that the reflectance is close to 100% when the shutter is off (when the shutter is not pressed). As a parallel plate having such characteristics, for example, "Umu" (trade name) manufactured by Nippon Glass Co., Ltd. is used.

When the shutter is on (photographing state), the input signal level is set so that the reflectance of the parallel plate 2 is close to 0% (the transmittance is close to 100%), as shown in FIG. At this time, the parallel plate 2 becomes nearly transparent. In this state, the light from the subject 6 does not reach the finder, so it cannot be observed, but this is not a problem since the shutter is normally on for 1/125 seconds. In this way, when the shutter is in the on state, the parallel plate 2 becomes almost transparent, and most of the light from the object passes through the parallel plate 2 and forms an image on the film 3 via the photographing lens 1. Further, since the optical axis B and the optical axis C coincide with the optical axis A, it is possible to obtain the same effect as a single-lens reflex camera in principle, so that parallax does not occur.

Next, another embodiment (invention of claim 2) will be described with reference to FIGS. 4 and 5. This embodiment is exactly the same in principle as the previously described embodiment, and the difference is that the light beam totally reflected by the parallel plate 2 is guided to the finder in the previous embodiment, whereas it is guided to the film 3. It is that you are. Therefore, in this example, FIG.
As shown in (dashed line), when the shutter is off, the transmittance of the parallel plate 2 is close to 100% (reflectance is close to 0%), and when the shutter is on, the reflectance of the parallel plate 2 is 100%. The input signal level to the parallel plate 2 is set so as to be close to %, and the reflectance and transmittance are set opposite to those of the embodiment of claim 1.

[0015]

[Effects of the Invention] As explained above, according to the present invention, a parallel plate for guiding light from a subject to a photographing lens or a finder lens is controlled by an electric signal to correspond to when the shutter is turned on and off. In this way, transmission and reflection of light can be selected, and the optical axis of the photographic lens and the optical axis of the viewfinder lens are aligned with the optical axis of the subject. Approximately 100% of the incident light from the subject
%, and it is possible to observe and photograph in bright conditions without parallax.

[Brief explanation of drawings]

FIG. 1 is an optical layout diagram showing an embodiment of claim 1 of the present invention.

FIG. 2 is a perspective view showing an embodiment of claim 1 of the present invention.

FIG. 3 is a characteristic diagram showing the light transmittance and reflectance of a parallel plate.

FIG. 4 is an explanatory diagram showing the relationship between the light reflectance of a parallel plate and shutter operation.

FIG. 5 is an optical layout diagram showing an embodiment of claim 2 of the present invention.

FIG. 6 is a perspective view showing an embodiment of claim 2 of the present invention.

FIG. 7 is an explanatory diagram showing a viewfinder field of a conventional lens shutter camera.

[Explanation of symbols]

1 Photography lens 2 Parallel plate 4 Total reflection mirror 5 Finder lens 6 Subject

Claims (2)

[Claims] 1. A parallel plate disposed in front of a photographic lens at a predetermined angle with respect to the optical axis of the photographic lens, a total reflection mirror that totally reflects the light beam reflected by the parallel plate, and the total reflection mirror. A camera optical system consisting of a finder lens placed on the optical axis of the light beam reflected by a mirror, and the parallel plate has a light transmittance that changes when the shutter is turned off by controlling the input of an electric signal. is approximately 0% (reflectance is approximately 1)
00%), and the light transmittance is approximately 100 when the shutter is on.
% (reflectance is approximately 0%). 2. A parallel plate arranged in front of a finder lens at a predetermined angle with respect to the optical axis of the finder lens, a total reflection mirror that totally reflects the light beam reflected by the parallel plate, and the total reflection mirror. A camera optical system comprising a photographing lens disposed on the optical axis of the light beam reflected by the mirror, the parallel plate controlling the input of an electric signal to
When the shutter is off, the light transmittance is approximately 100% (reflectance is approximately 0%), and when the shutter is on, the light transmittance is approximately 0%.
A camera optical system characterized by having a reflectance of approximately 100%.