JPH09236850A - Finder for camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact finder for a camera capable of executing high accurate focusing without causing any parallax between a finder optical system and a range-finding optical system and capable of excellently observing a visual field image. SOLUTION: The finder optical system is constituted by arranging a diaphragm 1, positive lens 2, an optical path dividing prism 3 and a visual field frame 5, as an objective optical system and a three-times reflection prism 6 and positive lens 7, as an eyepiece optical system, in order from an object side. The optical path dividing prism 3 has an optical path dividing surface 8 coated so as to transmit an infrared radiation and reflect a visible radiation. A projection optical system is in common from the objective optical system to the optical path dividing surface 8, and a prism 9 and a focusing optical element 10 are arranged behind the optical path dividing surface 8 in the order from the object side. The working surface 1a of the diaphragm 1 is made of a material having the property of intercepting the visible radiation and transmitting the infrared radiation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a finder for a camera, and more particularly to a finder for a camera which has a finder optical system separate from a photographing optical system and further has an automatic focus detection mechanism.

[0002]

2. Description of the Related Art Conventionally, an infrared projection active triangulation system has been adopted in many distance detection devices for lens shutter type cameras. This is because infrared light is projected from an infrared light emitting diode (IRED) to a subject through a light projecting lens, and reflected light from the subject is passed through a light receiving lens provided at a fixed distance (baseline length) from the light projecting lens. Light is received by a semiconductor detection device (PSD), and the subject distance is detected by the position of the incident light. According to this method, since the light projecting lens is usually arranged separately from the finder optical system by a predetermined distance, it is arranged between the optical axis of the light projecting lens and the optical axis of the finder optical system. Parallax occurs. In such a case, even if the photographer looks through the viewfinder and confirms the distance measuring range of the subject with the distance measuring frame, the actual spot light position of the light projecting lens will shift depending on the subject distance, which is the intention of the photographer. There is a risk of focusing on a point that does not exist. Therefore, cameras that improve such drawbacks and ensure that the subject aimed by the photographer is in focus are disclosed in Japanese Patent Laid-Open Nos. 63-229439 and 2-29723.
Japanese Patent Application Laid-Open No. 5-188281, Japanese Patent Application Laid-Open No. 5-2821
It is disclosed in Japanese Patent No. 88984.

In the cameras described in these patent publications, an optical path dividing member is used in the middle of the finder optical system to divide one optical path on the object side into two optical paths, an optical path of the finder optical system and an optical path for distance detection. On the other hand, the parallax is eliminated by matching the optical axis of the finder optical system with the optical axis of the light projecting optical system or the light receiving optical system of the distance detecting device.

Japanese Patent Application Laid-Open No. 63-229439, Japanese Patent Application Laid-Open No. 2-29723, Japanese Patent Application Laid-Open No. 5-288984 and the like describe that an optical path splitting member is provided in an objective optical system of a real image finder. Proposals have been made, and those disclosed in these publications have a configuration in which a common lens is used for the projection optical system and the objective optical system. But F
The performance of the objective optical system of the viewfinder that is desired to have a wide angle of view even if the number is large, and the projection optical system of the range finding optical system that is desired to have a small F number and be bright even if the angle of view is not so wide. It is difficult to achieve both performance and the same lens system.

Therefore, Japanese Patent Laid-Open No. 5-188281
Japanese Patent Laid-Open No. 5-288984 describes that after the optical path dividing surface in the objective optical system of the real image finder, from this surface to the distance measuring element for automatic focus detection and to the intermediate image forming surface of the finder. The one designed to have a positive power is proposed. However, in either case, the aperture of the distance measuring optical system is large, so that the aperture is larger than the luminous flux normally required by the finder optical system. For this reason, unnecessary light rays enter the viewfinder,
Ghosts and flares are likely to occur, resulting in poor visibility of the visual field image.

[0006]

In order to maintain the high accuracy of the distance measurement, it is necessary to make the apertures of the light projecting optical system and the light receiving optical system included in the distance measuring optical system large, and the objective optical of the finder. When a part of the system is shared with the distance measuring optical system, the aperture of the distance measuring optical system is larger than the aperture of a normal finder. For this reason, harmful light causing flare and ghost enters the finder optical system, and the visibility of the visual field image deteriorates. Originally, in order to prevent such harmful light from entering, a light-shielding plate that blocks light passing through the periphery other than the range necessary for the finder light flux is used, but in order to maintain the aperture of the distance measuring optical system, However, it is not possible to put in a light-shielding plate that is effective in blocking the above light. for that reason,
It has been a problem to prevent unnecessary light rays from entering the viewfinder while keeping the aperture of the distance measuring optical system large.

Therefore, the present invention has been made in view of the above problems, and an object thereof is to achieve high-precision distance measurement without parallax between the finder optical system and the distance-measuring optical system. It is an object of the present invention to provide a small finder for a camera that is capable of observing a field image well.

[0008]

In order to achieve the above object, the camera finder of the present invention comprises a distance measuring optical system in which a part of the objective optical system of the finder optical system is formed separately from the photographing optical system. A finder for a camera shared by the above and the present invention is characterized in that it has a diaphragm having an action surface having a property of transmitting infrared light higher than visible light.

The camera finder of the present invention is
Preferably, the working surface has a wavelength characteristic of substantially blocking visible light and substantially transmitting infrared light.

Further, the camera finder of the present invention is
Preferably, the working surface is constituted by an independent member having a wavelength characteristic of substantially blocking visible light and substantially transmitting infrared light. Further, the camera finder of the present invention is characterized in that the peripheral portion thereof has a member having a wavelength characteristic that the transmittance of infrared light is higher than that of visible light. That is, the camera finder of the present invention is preferably characterized by having a member having a wavelength characteristic of substantially blocking visible light and substantially transmitting infrared light outside the range of the finder light flux. Also,
The camera finder of the present invention is preferably characterized in that the member has a wavelength characteristic of substantially transmitting visible light within a range of a finder light beam. Further, the finder for a camera of the present invention is preferably characterized in that the member is provided with a space portion in a range of a finder light beam. Further, in the camera finder of the present invention, preferably, the member has a visible light transmittance of 0 to 0 in an outer portion of the finder light flux range.
It is characterized by having wavelength characteristics such that the transmittance of infrared light is within the range of 70% and 25-100%. Here, "visible light is substantially shielded" and "infrared light is substantially transmitted".
The term includes cases where the transmittance of visible light and infrared light has wavelength characteristics such that they fall within the respective ranges described above. The camera finder of the present invention is preferably such that the member is
Visible light transmittance in the outer portion of the range of the finder light flux is in the range of 0 to 25%, or infrared light transmittance in the outer portion is in the range of 70 to 100%. Characterize.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In general, since the active method is adopted for distance measurement by a distance measuring optical system as described above, infrared light is used, whereas for observing an object by a finder optical system. , Using visible light. At this time, even if harmful light enters the viewfinder, if it is not visible light, it has little effect on the appearance of the field of view image. Visible light passing through the outside may be blocked. Therefore,
For example, a diaphragm configured by using an interference filter, etc., which transmits infrared light and blocks visible light, is installed in the viewfinder, and the range of the light flux used for the viewfinder is visible light, infrared light passes through the diaphragm, Only the infrared light passes through the diaphragm in the range outside which the light flux for distance measurement passes.
In order to effectively remove harmful light, it is better to provide a diaphragm where the luminous flux of the finder becomes thin, and it is better to diaphragm on the object side from the positive lens component of the objective optical system. Furthermore, it is desirable that the harmful light can be most efficiently blocked by narrowing the aperture in the vicinity of the entrance pupil position. The visible light can be shielded by reflecting the visible light, but when a means having a wavelength characteristic of reflecting the visible light is used, the diaphragm surface may cause a ghost, etc., In order to prevent this, it is desirable to shield by using a means having a wavelength characteristic of absorbing visible light.

The embodiments of the present invention will be illustrated and described below.
FIG. 1 is a sectional view showing an embodiment of a camera finder of the present invention. The camera finder of the present invention includes a finder optical system and a distance measuring optical system. The finder optical system is, in order from the subject side, an objective optical system including a diaphragm 1, a positive lens 2, and a reflecting surface for image inversion.
An optical path splitting prism 3 including a surface, a field frame 5, and an eyepiece optical system including a three-fold reflecting prism 6 and a positive lens 7 each having three reflecting surfaces for image reversal as shown in FIGS. The reflection surface of the optical path splitting prism 3 and the reflection surfaces 6a, 6b, 6c of the three-time reflection prism 6 are arranged so that the intermediate image by the objective optical system becomes an erect image by a total of four reflections. There is. The projection optical system of the distance measuring optical system is composed of optical elements common to the objective optical system of the finder from the subject side to the optical path splitting surface 8 of the optical path splitting prism 3, and after the optical path splitting surface 8. The prism 9 and the distance measuring light emitting element 10 are arranged.

The optical path splitting prism 3 is formed by joining two prisms 4 and 9 at an optical path splitting surface 8. The junction surface of either one of the two prisms 4 and 9 is visible. It is coated to allow wavelength selection that reflects light and transmits infrared light. In the present embodiment, the optical path splitting surface 8 having such a wavelength characteristic is used as the reflecting surface of the optical path splitting prism 3 so that the unnecessary loss of light quantity can be almost suppressed. In addition, the entrance pupil position of the viewfinder is the positive lens 2
The diaphragm 1 is located on the subject side of the and near the entrance pupil position. The diaphragm 1 has a working surface 1a made of a material having a wavelength characteristic of blocking visible light and transmitting infrared light, and transmits all light rays in a range of an opening 1b through which a light beam used for a finder passes. It is supposed to do.

According to the configuration of this embodiment, the infrared light emitted from the distance measuring light emitting element 10 is projected onto the subject through the optical path dividing prism 3, the positive lens 2 and the diaphragm 1. At this time, since the working surface 1a of the diaphragm 1 transmits infrared light, the infrared light projected from the distance measuring light emitting element 10 is directed to the subject without being blocked by the diaphragm 1 and is reflected by the subject. The light is received by a light receiving element for distance measurement (not shown). On the other hand, of the light flux traveling from the subject to the finder optical system, the light flux used for the finder passes through the aperture 1b of the diaphragm 1 and the positive lens 2, and then only the visible light is finder optical by the optical path splitting surface 8 of the optical path branching prism 3. The visible light that is reflected in the direction of the optical path of the system and further becomes an erect normal image through the field frame 5, the three-time reflection prism 6, and the positive lens 7, while the visible light incident on the outside of the aperture 1b of the diaphragm 1 is It is blocked by the working surface 1a of No. 1. Therefore, extra visible light does not enter the observation side of the aperture stop 1, and ghost, flare, etc. are reduced.

Therefore, according to this embodiment, it is possible to block unnecessary light rays from entering the viewfinder while keeping the aperture of the distance measuring optical system large. Further, since the diaphragm 1 is provided in the vicinity of the position of the entrance pupil on the object side of the positive lens 2 of the objective optical system, the diaphragm 1 for which the finder light flux becomes the thinnest.
The action surface 1a can be made large, and harmful light can be blocked more efficiently. The diaphragm 1 may itself be made of a substance that blocks visible light and transmits infrared light. However, as shown in FIG. 3, for example, as shown in FIG. The transparent plate member 1c attached as a cover to the front surface may be integrated with a film 1d having a property of blocking visible light and transmitting infrared light by coating or printing. . Further, as means for blocking visible light, it is conceivable to use two types of means on the working surface 1a of the diaphragm 1; a means having a wavelength characteristic of reflecting visible light and a means having a wavelength characteristic of absorbing visible light. However, in order to avoid the occurrence of ghosts and flares, it is desirable to use a means having a wavelength characteristic of absorbing visible light, such as a visible light absorption filter, for the working surface 1a of the diaphragm 1 to block visible light. The optical path splitting surface 8 is preferably configured to have a wavelength characteristic of transmitting infrared light and reflecting visible light, but the optical path splitting surface 8 is made of a metal film having no such wavelength characteristic. May be configured.

FIG. 4 is a sectional view of another embodiment of the camera finder according to the present invention. In this embodiment, the finder optical system includes, in order from the subject side, a negative lens 12, a positive lens 13, an optical path splitting member 14 having a first reflecting surface for image inversion, and a positive lens 15 as objective optical systems.
The field frame 16 and the eyepiece optical system are each composed of a three-reflection prism 17 and a positive lens 18, each of which has three reflecting surfaces for image reversal as in the embodiment shown in FIGS. Similar to the embodiment, the intermediate image formed by the objective lens is arranged so as to be an erect image by a total of four reflections by the first reflection surface and the three reflection surfaces of the three-time reflection prism 17. Further, the projection optical system of the distance measuring optical system is composed of optical elements common to the objective optical system of the finder up to the optical path dividing member 14 in order from the subject side, and the distance measuring light emission is performed after the optical path dividing member 14. The element 19 is arranged.

The optical path dividing member 14 is composed of, for example, a plane mirror having a wavelength characteristic of reflecting visible light and transmitting infrared light, and the plane on the object side is the optical path dividing surface 14a. ing. In this embodiment, the optical path splitting surface 14a having such wavelength characteristics is used as the first reflecting surface. The entrance pupil position of the finder optical system is located near the object-side surface of the negative lens 12. On the surface of the negative lens 12 on the object side, a film of a substance having a wavelength characteristic of blocking visible light and transmitting infrared light is applied by printing except for a range through which a light beam used for a finder passes. The film itself constitutes the working surface 11 a of the diaphragm 11.

According to the configuration of this embodiment, the infrared light emitted from the distance measuring light emitting element 19 is projected onto the subject through the optical path dividing member 14, the positive lens 13 and the negative lens 12. At this time, since a film formed by printing as the working surface 11a of the diaphragm 11 transmits infrared light, the infrared light projected from the distance measuring light emitting element 19 is directed toward the subject without being disturbed and reflected by the subject. The light is then received by a distance measuring light receiving element (not shown). On the other hand, of the light flux heading for the finder optical system from the subject, the light flux used for the finder passes through the aperture 11b of the diaphragm 11, passes through the negative lens 12 and the positive lens 13, and then is passed through the optical path splitting surface 14a of the optical path splitting member 14. Only visible light is reflected in the direction of the optical path of the finder optical system, and further an erect normal image is formed via the positive lens 15, the field frame 16, the three-time reflection prism 17, and the positive lens 18. On the other hand, visible light incident on the outside of the opening 11b of the diaphragm 11 is blocked by the working surface 11a of the diaphragm 11. Therefore, extra visible light does not enter the observation side from the diaphragm 11, and ghost, flare, etc. are reduced.

Therefore, according to this embodiment, it is possible to block harmful light entering the finder without reducing the aperture of the distance measuring optical system. Further, the diaphragm 11 is provided near the entrance pupil position on the object side of the positive lens 13 of the objective optical system.
Since the finder light flux is provided, the action surface 11a of the diaphragm 11 where the finder light flux becomes the thinnest can be made large, and harmful light can be blocked more efficiently. As means for blocking visible light, there are two types of means, one having a wavelength characteristic of reflecting visible light and the other having a wavelength characteristic of absorbing visible light.
It is conceivable to use it on the working surface 11a of No. 1, but in order to avoid the generation of ghost, flare, etc., it is better to use means having wavelength characteristics for absorbing visible light on the working surface 11a of the diaphragm 11 to block visible light. desirable. In addition, the optical path splitting surface 14
It is preferable that a is configured to have a wavelength characteristic of transmitting infrared light and reflecting visible light, but the optical path dividing surface 14a is made of a metal film having no such wavelength characteristic. Good.

FIG. 5 is a sectional view of still another embodiment of the camera finder according to the present invention. In the present embodiment, the finder optical system has a configuration including a negative lens 20 instead of the diaphragm 11 and the negative lens 12 in the embodiment of FIG. The negative lens 20 is formed by integrally molding resins having different physical properties, or by partially injecting a dye into a resin molded product, so that the infrared light in the peripheral portion of the lens is higher than that of visible light. It has a wavelength characteristic of high transmittance, and in particular, visible light is substantially shielded at a portion through which a finder light beam passes (hatched portion shown in FIG. 5), and visible light is substantially transmitted at other portions. Further, the negative lens 20 is configured to substantially transmit infrared light over the entire surface.
The negative lens 20 is preferably formed so as to have wavelength characteristics such that the transmittance of visible light rapidly changes from a distance of a predetermined radius from the optical axis. It may be formed to have a wavelength characteristic that decreases with distance from the axis. The shaded portion of the negative lens 20 is designed to have a wavelength characteristic such that the transmittance of visible light is in the range of 0 to 70%, and the transmittance of infrared light is in the range of 25 to 100%. It is designed to have a wavelength characteristic within. However, since it is desirable that the visible light transmittance be lower and the infrared light transmittance be higher, the negative lens 20 has a visible light transmittance in the range of 0 to 25% in the shaded portion. It is preferable that the wavelength characteristic be such that the infrared ray transmittance be in the range of 70 to 100%. Other configurations are substantially the same as those of the embodiment shown in FIG.

According to the configuration of this embodiment, the negative lens 20
The part indicated by the diagonal lines in FIG.
The same effect as that of “a” is achieved, and excess light does not enter the observation side from the negative lens 20, and ghost, flare, etc. are reduced. At this time, according to the present embodiment, since the negative lens 20 itself is provided with the effect of the diaphragm, the number of parts can be reduced and the assembly becomes easy. Other effects are shown in Figure 4.
This is substantially the same as the embodiment.

FIG. 6 is a sectional view showing still another embodiment of the camera finder according to the present invention. In the present embodiment, the finder optical system includes, in order from the subject side, a negative lens 21, a positive lens 13, an optical path splitting member 14 having a first reflecting surface for image inversion, and a field frame 1 as an objective optical system.
6. As the eyepiece optical system, it is composed of a triple reflection prism 17 and a positive lens 18 having three reflecting surfaces for image reversal as in the embodiment shown in FIGS. 1 and 2, and the embodiment of FIG. Similarly to the above, the intermediate image formed by the objective lens is arranged so as to be an erect image by a total of four reflections by the first reflection surface and the three reflection surfaces of the three-time reflection prism 17. Further, the projection optical system of the distance measuring optical system is composed of optical elements common to the objective optical system of the finder up to the optical path dividing member 14 in order from the subject side, and the distance measuring light emission is performed after the optical path dividing member 14. The element 19 is arranged.

The negative lens 21 has a wavelength characteristic of substantially blocking visible light and substantially transmitting infrared light. Further, as shown in FIG. 6, the negative lens 21 has a space 21a formed in a portion through which the finder light flux passes. The negative lens 21
The shaded area has a wavelength characteristic in which the transmittance of visible light is in the range of 0 to 70%, and a wavelength characteristic in which the transmittance of infrared light is in the range of 25 to 100%. Is to have. However, since it is desirable that the transmittance of visible light is lower and the transmittance of infrared light is higher,
The negative lens 21 has a wavelength characteristic in which the transmittance of visible light in the shaded portion is in the range of 0 to 25%, or a wavelength in which the transmittance of infrared light is in the range of 70 to 100%. It is preferably designed to have characteristics. Other configurations are substantially the same as those of the embodiment of FIGS.

According to the configuration of this embodiment, the negative lens 21
1 has the same effect as the operation surface 1a of the diaphragm 1 shown in the embodiment of FIG.
Further, it does not enter the observation side and reduces ghost and flare. At this time, according to the present embodiment, since the lens itself is provided with the effect of the diaphragm, the number of parts can be reduced, and the assembly is facilitated.
Since the range through which the finder light flux of the negative lens 21 passes is a space, there is no loss such as surface reflection and the like.
It is possible to transmit 00% of light. Other functions and effects are substantially the same as those of the embodiment of FIGS.

As described above, the camera finder of the present invention has the following features in addition to the features described in the above claims.

(1) The camera finder according to claim 1 or 2, wherein the working surface is printed on a lens.

(2) The working surface is disposed on a plate-like member provided on the front surface of the camera including the finder, or in any one of the above (1). The viewfinder for the camera described in.

(3) The working surface substantially blocks visible light,
The camera finder according to claim 1, wherein the finder for a camera comprises an independent member having a wavelength characteristic of substantially transmitting infrared light.

(4) The working surface transmits visible light in the range of the finder light flux, blocks visible light in the other range, and transmits infrared light. Item 1 or 2 or the finder for a camera according to any one of (1) to (3) above.

(5) The finder for a camera according to any one of claims 1 and 2 or (1) to (4), wherein the finder is a real image type finder.

(6) The working surface is arranged on the object side of a positive lens component included in the objective optical system of the finder, or in any one of the above (1) to (5). The viewfinder for the camera according to any one of 1.

(7) The camera according to any one of (1) to (6) above, wherein the working surface is arranged in the vicinity of the entrance pupil position of the finder. Finder for.

(8) The working surface is configured to shield visible light by absorbing it, or in any one of the above (1) to (7). Viewfinder for camera.

(9) The camera finder according to claim 3, wherein the member has a wavelength characteristic of substantially transmitting visible light within a range of a finder light beam.

(10) The camera finder according to claim 3, wherein the member is provided with a space in the range of the finder light flux.

(11) The above-mentioned member has wavelength characteristics such that the visible light transmittance in the outer portion of the range of the finder light flux is in the range of 0 to 70% and the infrared light transmittance is in the range of 25 to 100%. The viewfinder for a camera according to claim 3, further comprising:

[0037]

As described above, according to the present invention, it is possible to dispose an appropriate flare stop in the view optical path of the viewfinder while maintaining a large aperture of the optical system on the distance measuring side. It is possible to observe a good visual field image with a viewfinder while maintaining high accuracy and less ghost and flare.

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic configuration of an embodiment of a camera finder according to the present invention.

FIG. 2 is a schematic plan view of the eyepiece lens system according to the above embodiment.

FIG. 3 is a partially enlarged view showing the diaphragm of the above embodiment.

FIG. 4 is a sectional view showing a schematic configuration of another embodiment of the camera finder according to the present invention.

FIG. 5 is a sectional view showing a schematic configuration of still another embodiment of the camera finder according to the present invention.

FIG. 6 is a sectional view showing a schematic configuration of still another embodiment of the camera finder according to the present invention.

[Explanation of symbols]

 1,11 Aperture 2,7,13,15,18 Positive lens 3 Optical path splitting prism 5,16 Field frame 6,17 3 times reflection prism 8,14a Optical path splitting surface 8,10 Prism 9,19 Distance measuring light emitting element 12 , 20, 21 Negative lens 14 Optical path splitting member 1a, 11a Working surface 5a, 5b, 5c 3 times reflecting surface

Claims (3)

[Claims] 1. A finder for a camera in which a part of an objective optical system of a finder optical system formed separately from a photographing optical system is shared with a distance measuring optical system. A viewfinder for a camera, which has a diaphragm having an action surface having a high transmittance of outside light. 2. The viewfinder for a camera according to claim 1, wherein the working surface has a wavelength characteristic of substantially blocking visible light and substantially transmitting infrared light. 3. A camera finder in which a part of an objective optical system of a finder optical system formed separately from a photographing optical system is shared with a distance measuring optical system, outside the range of the finder light flux. A viewfinder for a camera, which has a member having a wavelength characteristic of substantially blocking visible light and substantially transmitting infrared light.