JP2001141980A - Optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical device which extends an area, where focus detection is possible in an arbitrary area in horizontal and vertical directions or plural areas within a photographic range and detects a focus even at an arbitrary point in a two-dimensional continuous area with high precision and detects a focus with a subject image free from distortion. SOLUTION: The optical device is provided with a first reflection mirror 4, which reflects a luminous flux from a photographic lens system 1 to a finder optical system (5, 6, and 7) and is withdrawn off an optical axis 2 of the photographic lens system 1 at the time of photographing and is translucent, and a second reflection mirror 8 which reflects a transmission luminous flux from the first reflection mirror 4 to a focus detection optical system (11, 12, 13, and 14) and is withdrawn off the optical axis 2 of the photographic lens system 1, and an optical member 9 which is withdrawn off the optical axis of the photographic lens system at the time of photographing and has a light converging property is provided between the first reflection mirror 4 and the second reflection mirror 8 and on the optical axis of the photographic lens system 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical apparatus such as a camera, a video camera, and a digital camera having a TTL finder and a focus detection optical system.

[0002]

2. Description of the Related Art Conventionally, there has been proposed a camera using a light beam passing through a photographing lens system for a finder optical system and a focus detection optical system.

FIG. 16 is a schematic view of a camera showing a conventional example, in which 101 is a photographing lens for photographing, 102 is a photographing lens.
Is a translucent main mirror, 103 is a reticle, 104 is a pentaprism, 105 is an eyepiece, 106 is a submirror, 107 is a film, and 108 is a focus detection device.

In FIG. 1, a light beam from a subject (not shown) passes through a photographing lens 101, is reflected upward from a main mirror 102, and forms an image on a focusing screen 103 to form a subject image.

A subject image formed on a focusing screen 103 is visually recognized by a photographer or an observer via an eyepiece lens 105 through a plurality of reflections by a pentaprism 104.

On the other hand, from the taking lens 101 to the main mirror 10
A part of the light beam that has reached 2 passes through the transmission portion of the main mirror 102, is reflected downward by the sub-mirror 106, and is guided to the focus detection device 108.

The focus detection device 108 is a focus detection device using a well-known phase difference detection method generally called an image shift method.

Here, in the above-described optical apparatus, since a light beam necessary for focus detection is guided to the focus detection device 108 via the sub-mirror 106, the range in which the focus can be detected in the photographing range is the sub-mirror 106. Size (area).

It is difficult to expand the sub-mirror 106 particularly upward due to the positional relationship with the main mirror 102. Therefore, it is not possible to expand the area where the focus can be detected above the film 107, that is, on the subject side, in the downward direction.

In FIG. 1, to increase the area of the sub mirror 106 without interfering with the main mirror 102, a method of moving the sub mirror 106 backward is considered.

However, in this case, the sub mirror 106
The position of the planned focal plane of the objective lens 101 formed after reflecting the light is moved upward, so that the distance between the planned focal plane and the focus detection device 108 is large, and a field lens (not shown) in the focus detection device 108 is considerably moved. Need to be bigger.

This is a major obstacle in arranging the focus detection system at the bottom of the camera.

In order not to enlarge the field lens with respect to the planned focal plane moved upward, the field lens may be moved upward in accordance with the planned focal plane. However, this causes the field lens to block the luminous flux. Therefore, at the time of photographing, it is necessary to retract the field lens out of the photographing light beam.

To achieve this, the mechanical structure becomes extremely complicated and costly, and it is difficult to maintain the same accuracy as that of the conventional focus detection device.

Therefore, in Japanese Patent Application Laid-Open No. 09-184696, instead of the sub-mirror 102, a reflecting mirror having a light-collecting property such as a concave mirror or an elliptical mirror is used, and the function of a field lens is given to the reflecting mirror itself. Things are known.

FIG. 17 is a schematic view of a camera showing the conventional example.

In the figure, reference numeral 109 denotes a reflecting mirror having a light collecting property.

The description of the same parts as in FIG. 16 will be omitted.

The reflecting mirror 109 is arranged so that the exit pupil position of the photographing lens 101 and the incident position of a secondary imaging system (not shown) in the focus detection device 108 substantially form an image, and functions as a field lens. Play.

Therefore, the reflecting mirror 109 can be arranged as rearward as possible, and it is possible to detect a focus in a wide range in the photographing screen.

[0021]

However, in the above-mentioned prior art, the subject image re-imaged on a photoelectric conversion element (not shown) in the focus detection device 108 has a large asymmetry distortion. .

For this reason, it is necessary to adjust the arrangement of the pixels of the photoelectric conversion element to some extent to the distortion of the subject image.

Further, since the reflecting mirror 109 is inclined with respect to the optical axis of the taking lens 101, the parallax when the pupil of the taking lens 101 is divided into two parts differs depending on the position on the focus detection area. The moving speed of the image due to the defocus varies depending on the position on the focus detection area, and the defocus amount of the photographing lens 101 cannot be accurately detected.

Japanese Patent Laid-Open Publication No. Hei 10-311945 discloses a technique for correcting the output of a photoelectric conversion element based on the distribution of parallax in a focus detection area.

As described above, the reflecting mirror 109 having a light collecting property
Although it is possible to enlarge the focus detection area by using, it is necessary to correct the arrangement of pixels and output signals on the photoelectric conversion element due to distortion of the subject image on the photoelectric conversion element, and the cost is also high. In addition, it is difficult to maintain the accuracy of the focus detection device.

According to the present invention, a focus can be detected at any point in a continuous two-dimensional area while extending a focus detectable area in a vertical or horizontal direction or a plurality of areas in a photographing range. It is another object of the present invention to provide a camera that can perform the processing with high accuracy and that can detect a focus with a subject image without distortion, and an optical apparatus using the camera with a simple configuration.

[0027]

According to an aspect of the present invention, there is provided a semi-transmissive first reflecting mirror for reflecting a light beam from a photographic lens system, and a transmission of the first reflecting mirror. An optical device including a second reflecting mirror that bends a light beam, wherein an optical member having a light-collecting property is provided between the first reflecting mirror and the second reflecting mirror.

The optical member can be retracted to a position which does not interfere with a photographing optical path during photographing.

The optical member is disposed between the first reflecting mirror and the second reflecting mirror and on the optical axis of the photographing lens system, and can be retracted outside the optical axis of the photographing lens system during photographing. It is characterized by having.

The optical member is a convex lens.

[0031] The optical member is a diffractive optical element.

[0032] The second reflecting mirror is characterized in that a light beam transmitted through the first reflecting mirror is bent to a focus detecting optical system.

The focus detection optical system includes: a secondary imaging system configured to form a light beam from an object image, which is condensed by the optical member and then reflected and guided by a second reflecting mirror, as a secondary image; And a photoelectric conversion element for detecting a light amount distribution relating to the secondary imaging system.

According to the above configuration, the area in which the focus can be detected can be greatly expanded with a simple configuration without increasing the size of the camera.

Further, the focus detection is extended to a continuous two-dimensional area, so that it is easy to focus on an object at an arbitrary desired position, and the degree of freedom in setting a composition for photographing or observation is increased. An effect such as increase can be obtained.

Furthermore, since focus detection can be performed with a good secondary image without distortion, stable focus detection with high accuracy is possible.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 is a schematic view of a main part when a focus detection device according to a first embodiment of the present invention is applied to an optical device such as a camera, and FIG. FIG. 2 is a schematic diagram of a main part of a main part constituting the focus detection device of FIG. 1, showing a light beam incident on a focus detection optical system.

In the drawing, reference numeral 1 denotes a photographic lens system, 2 denotes an optical axis of the photographic lens system 1, 3 denotes a film (image pickup surface), and 4 denotes a semi-transmissive main mirror arranged on the optical axis 2 of the photographic lens system 1. Reference numeral 5 denotes a focusing screen on which a subject image formed by the photographing lens system 1 is formed via the main mirror 4.

Reference numeral 6 denotes a pentaprism, and reference numeral 7 denotes an eyepiece system for observing an object image on the reticle 5.

Reference numeral 8 denotes a sub-mirror disposed obliquely on the image plane side of the photographing lens system 1 with respect to the optical axis 1, 9 denotes a convex lens provided between the main mirror 4 and the sub-mirror 8, and 10 denotes a film formed by the sub-mirror 8. A subject image is formed on a paraxial image plane conjugate to 3.

11 is an infrared cut filter, 12 is 2
A diaphragm 13 having two apertures 12-1 and 12-2, and a secondary connection 13 having two lenses 13-1 and 13-2 arranged corresponding to the two apertures 12-1 and 12-2 of the diaphragm 12. An image system 14 indicates a photoelectric conversion element (light receiving unit) having two area sensors 14-1 and 14-2.
The sub-mirror 8, the secondary imaging system 13, and the like constitute one element of the optical means.

The convex lens in this embodiment has a light-converging curvature, and has two apertures 12-1 and 12-2 of the diaphragm 12.
Is projected near the exit pupil 1a of the taking lens system 1.

The sub-mirror 8 is formed by depositing a metal film such as aluminum or silver so that only necessary areas reflect light, and also functions as a visual field mask (regulating means) for limiting a range in which focus detection is performed. ing.

FIG. 3 is a plan view of the diaphragm 12 shown in FIG. The aperture 12 has a configuration in which two horizontally long apertures 12-1 and 12-2 are arranged in a direction in which the aperture width is narrow (up and down direction of the photographing range).

The dotted lines in the figure correspond to the apertures 12-1 and 12-2 of the diaphragm 12 and correspond to the lenses 13-1 of the secondary imaging system 13 disposed behind the apertures 12-1 and 12-2. , 13
-2.

FIG. 4 is a plan view of the photoelectric conversion element 14.
The two area sensors 14-1 and 14-2 shown in FIG. 1 are two-dimensionally arranged with a plurality of pixels as shown in FIG.
The area sensors 14-1 and 14-2 are arranged.

Here, the main mirror 4 corresponds to the first reflecting mirror of the first aspect, the sub-mirror 8 corresponds to the second reflecting mirror of the first aspect, and the convex lens 9 corresponds to the optical member having the light collecting property of the first aspect. Yes, it is.

In the above configuration, as shown in FIG.
After passing through the main mirror 4, the two light beams 15-1 and 15-2 are reflected by the sub-mirror 8 in a direction substantially along the inclination of the sub-mirror 8, and form a subject image on the paraxial image plane 10.

At this time, the convex lens 9 forms a minute image of a subject image formed on the imaging plane 3 on the paraxial imaging plane 10.

The luminous flux from the subject image formed on the paraxial imaging plane 10 passes through the infrared cut filter 11 and the two apertures 12-1 and 12-2 of the aperture 12, and each lens 13 of the secondary imaging system 13 The light is condensed by -1 and 13-2 and reaches the area sensors 14-1 and 14-2 of the photoelectric conversion element 14, respectively.

The light fluxes 15-1 and 15-2 in the drawing are the light fluxes that form an image at the center of the film 3, but the light fluxes that form an image at other positions, for example, 16-1 and 16-2 in FIG.
-2, 17-1, and 17-2 also reach the photoelectric conversion element 14 via the same route.

The photoelectric conversion element 14 corresponding to a predetermined two-dimensional area on the film 3 in the photographing range as a whole
The two secondary images relating to the subject image on each of the area sensors 14-1 and 14-2, that is, 18-1 and 1-1 indicated by dotted lines in FIG.
8-2 are formed, and the area sensors 14-1 and 14-2 of the photoelectric conversion element 14 form two secondary images 18-1 and 18-2.
Two light quantity distributions for 18-2 are formed.

In the present embodiment, the convex lens 9 is provided with an exit pupil position of the photographing lens system 1, for example, when various photographing lenses are used interchangeably, their average exit pupil position and a secondary imaging system. Thirteen incident positions are substantially imaged.

Thus, the convex lens 9 functions as an ideal field lens.

In the present embodiment, the first surface 13a, which is the surface on the incident side of the secondary imaging system 13, has a concave shape, so that light incident on the secondary imaging system 13 is forcibly refracted. And the photoelectric conversion element 14
Good secondary images 18-1 and 18-2 without distortion are formed over a wide range of the upper two-dimensional region.

With respect to the two light quantity distributions of the subject image obtained in this manner, the separation direction, that is, the two area sensors 14-1 and 14- shown in FIG. 2 is calculated at each position composed of arbitrary plural elements of the area sensors 14-1 and 14-2 so that the focus state of the photographing lens system 1 is two-dimensionally set in the photographing range. Detected in any area.

Next, the operation of the camera of the present embodiment at the time of shooting will be described.

FIG. 6 is a block diagram of the electric system of the camera according to the present embodiment. Reference numeral 18 denotes a CPU (Central Processing Unit).

In FIG. 6, 19 is a power supply, and 20 is a SW.
1, well-known release button with SW2, 21
A focus detection device including an infrared cut filter 11, an aperture 12, a secondary imaging system 13, a photoelectric conversion element 14, and the like.
A photographing lens system driving circuit 22 drives the photographing lens system based on the focus adjustment state of the focus detection device 22, a convex lens driving circuit 23 retracts the convex lens 9 out of the photographing light beam at the time of photographing, and a photographing light beam 24 moves the mirror system at the time of photographing. Mirror drive circuits for retreating outside are connected to the central processing unit 18 respectively.

FIG. 7 is a flowchart showing the operation of the camera of this embodiment. The operation of the camera at the time of photographing will be described with reference to this flowchart.

First, when the release button SW1 is turned on in step 201, the process proceeds to step 202.

In step 202, the defocus amount of the photographing lens system is calculated by detecting the focus adjustment state of the photographing lens system 1 by the focus detecting device 22.

Next, in step 203, step 20
The photographing lens system is driven based on the defocus amount calculated in step 2, and the process proceeds to step 204.

In step 204, the focus detecting device 2 determines whether or not the camera is in focus by driving the photographing lens system.
2 is used.

If it is not in focus, the process returns to step 202, and a series of operations are performed again. If it is determined that focus is achieved, the process proceeds to step 205.

When SW2 is turned on in step 205, the process proceeds to step 206.

In step 206, the convex lens 9 retracts with the turning on of SW2.

Here, the retracting structure of the convex lens will be briefly described with reference to FIG.

FIG. 8 is a view of FIG. 1 as viewed from the film surface side, and shows only components necessary for the retreat operation of the convex lens.

In the figure, 9 is a convex lens, 21 is FIG.
Is a focus detection device including an infrared cut filter 11, an aperture 12, a secondary imaging system 13, a photoelectric conversion element 14, and the like.

Reference numeral 25 denotes a holding member for holding the convex lens 9, which is provided rotatably about a rotation shaft 27 by a convex lens rotation driving means 26.

The retracting structure of the convex lens 9 in the above configuration will be described.

First, when the ON of SW2 is detected, the central processing unit 18 sends a convex lens retracting drive signal to the convex lens driving circuit 23.

Next, by driving the convex lens driving means 26 in response to the convex lens retracting drive signal sent to the convex lens driving circuit 23, the holding member 25 is rotated about the rotation shaft 27 in the direction of the arrow, as shown by the dotted line in FIG. Out of the luminous flux.

Thereafter, when the retreat of the convex lens 9 and the holding member 25 is completed, the process proceeds to step 207.

In step 207, the main mirror 4 and the sub-mirror 8 are retracted out of the photographic light beam by the mirror-up mechanism and the driving means (not shown).

Thereafter, the flow advances to step 208, where the shutter is activated and the photographing is completed.

After the photographing, the main mirror 4, the sub-mirror 8, and the convex lens 9 return to their original positions in this order.

As described above, by disposing the convex lens 9 between the main mirror 4 and the sub-mirror 8, it becomes possible to collect the light beam transmitted through the main mirror 4.

Here, the light beam incident on the focus detection optical system is limited by the size of the sub-mirror 8.

Therefore, the area where the focus can be detected in the photographing range is determined by the size of the sub-mirror 8.

On the other hand, the size of the sub-mirror 8 is limited due to the positional relationship with a shutter unit (not shown) arranged immediately before the film surface 3.

However, in the present embodiment,
Since the light beam condensed by the convex lens 9 is reflected by the sub-mirror 8 and guided to the focus detection optical system, even if the size of the sub-mirror 8 is limited, it is possible to detect the focus in a wide area in the shooting range with a simple configuration. became.

Further, since the convex lens 9 only minutely forms an image in an area in the photographing range where focus detection is performed, it is possible to perform focus detection with a good secondary image without distortion.

Here, in the present embodiment, the method of retracting the convex lens 9 is such that the convex lens 9 is retracted below the camera by rotation as shown in FIG. Instead of the sub-mirror 8 retracted, a mechanism that retracts the convex lens 9 and lowers the sub-mirror 8 toward the focus detection device 21 may be used. Further, a mechanism for retracting the convex lens 9 by linearly sliding the lens is also conceivable.

In this embodiment, the pair of secondary images 18-1 and 18-2 used for focus detection are formed by dividing the exit pupil 1a of the photographing lens system 1 into upper and lower parts. Focus detection may be performed using a pair of secondary images obtained by dividing the exit pupil 1a into right and left.

Further, the focus detection may be performed with two pairs of secondary images obtained by dividing the exit pupil 1a of the photographing lens system 1 into upper and lower parts and left and right parts.

(Second Embodiment) A second embodiment is an improvement of the convex lens of the first embodiment, and FIG. 9 shows a focus detection device of the present embodiment using an optical device such as a camera. FIG. 10 is a schematic view of a main part of the focus detection device shown in FIG. 9 and shows a light beam incident on a focus detection optical system.

Here, in the following, components denoted by the same reference numerals as those in the first embodiment perform the same functions, and detailed descriptions thereof will be omitted.

In FIG. 8, reference numeral 28 denotes a diffractive optical element (Diff).
aractive Optical Element). Here, the DOE 28 corresponds to the optical member having the light-collecting property of the first aspect.

Regarding DOE, "Optics" Vol. 22, No. 12
Although introduced on pages 6 to 130 (Yuzo Ono), DOE will be briefly described below.

DOE is an optical element based on the light diffraction phenomenon. As shown in FIG. 11, when the incident angle is θ, the exit angle is θ ′, the diffraction order is m, and the pitch of the diffraction grating is d, the DOE is diffracted according to the following equation. A phenomenon occurs. sin θ−sin θ ′ = mλ / d (1) An example of a focus detection optical system to which such a diffraction phenomenon is applied is proposed in Japanese Patent Application Laid-Open No. 61-134716.

In this proposal, light beams of a plurality of diffraction orders that are divided into substantially the same light amount by a diffraction phenomenon are used.

On the other hand, when attention is paid to the luminous flux of one diffraction order, for example, when the pitch d of the diffraction grating is continuously changed as shown in FIG. be able to.

When the sectional shape of the DOE is made serrated as shown in FIG. 13 and the height h of the peak satisfies the following expression (2), 100% of the m-th order diffracted light with respect to the incident light of wavelength λ is obtained.
Becomes Here, n is the refractive index of the substrate. h = mλ / (n−1) (2) Such a shape is called a kinoform.

As shown in FIG. 14, a DOE obtained by stepwise approximating this kinoform is a binary optical element (Binary Optical Element).
Element).

The binary optical element can be manufactured relatively easily by a lithographically manufactured method.

In the binary optical element, 81 in four-step approximation
It is known that a diffraction efficiency of 95% can be obtained by approximation in 8 steps and 99% by approximation in 16 steps.

As can be seen from equation (1), DOE
The wavelength characteristic of the focal length of the lens constituted by the following equation is expressed by the following equation (3), and when converted into a so-called Abbe number, νd = −3.4.
5, which means that it has a large inverse dispersion.

Here, f (λ) is the focal length at the wavelength λ of the lens constituted by the DOE. .lambda.f (.lambda.) = constant (3) It is known that the diffraction efficiency k at the wavelength .lambda. of the kinoform whose diffraction efficiency is 100% at the wavelength .lambda.0 follows the following equation (4).

K = sin2 [π ｛(λ0 / λ) -m｝] / [π ｛(λ0 / λ) -m｝] 2 (4) The DOE 28 having the basic performance as described above is the first embodiment. It has the same light-converging power as the convex lens 9 in the form, and minutely forms a subject image on the paraxial image plane 10.

Further, when the exit pupil position of the photographing lens system 1, for example, various photographing lens systems are used interchangeably, their average exit pupil position and the incident position of the secondary imaging system 13 are substantially formed. I am trying to be imaged.

As a result, the DOE 28 functions as an ideal field lens.

With the above-described configuration, similarly to the first embodiment, using the light beam obtained by dividing the exit pupil 1a of the photographing lens system into upper and lower parts, the photographing lens system 1 is formed by a well-known image shift type focus detection principle. Is detected two-dimensionally in an arbitrary region in the photographing range.

The light beam entering the focus detection optical system follows the same path as in the first embodiment as shown in FIG. 10, and the secondary image re-imaged on the photoelectric conversion element 14 is also formed. As in the first embodiment, a good secondary image without distortion is obtained, and stable focus detection with high accuracy is possible.

Also, regarding the operation of the camera at the time of shooting,
The description is omitted because it is the same as the first embodiment.

In this embodiment, the DOE 28 is used in place of the convex lens 9 of the first embodiment.
It is possible to make the thickness t of the DOE shown in (2) thinner than that of the convex lens 9.

Therefore, the DOE 9 can be arranged further rearward (on the film surface 3 side), and accordingly, the DOE 9 can be made larger and the area of the light beam transmitted through the main mirror 4 can be widened. Focus detection of a wider area in the photographing range can be performed.

Further, the degree of freedom of the retracting structure of the DOE 28 at the time of photographing is further increased. For example, at the time of photographing, the DOE 28 can be retracted outside the photographing light beam by a structure sandwiched between the main mirror 4 and the sub mirror 8 as shown in FIG. It is.

It is to be noted that if the DOE is used, the imaging performance may be deteriorated due to chromatic aberration. In such a case, an optical member for removing chromatic aberration may be provided between the DOE 9 and the photoelectric conversion element 14.

Here, in FIG. 15, reference numeral 29 denotes the main mirror 4.
The rotation axis 30 is a rotation axis of the sub-mirror 8 and the DOE 28, and is configured to be rotatable about the respective rotation axes by a mirror-up mechanism and a driving unit (not shown).

In the present embodiment, a pair of secondary images used for focus detection are formed by dividing the exit pupil 1a of the photographing lens system 1 into upper and lower parts. Focus detection may be performed using the pair of secondary images thus obtained.

Further, the focus detection may be performed with two pairs of secondary images obtained by dividing the exit pupil 1a of the photographing lens system 1 into upper and lower parts and left and right parts.

[0114]

As described above, according to the present invention, the area in which the focus can be detected can be dramatically increased with a simple configuration without increasing the size of the camera.

Further, the focus detection is extended to a continuous two-dimensional area, so that it is easy to focus on an object at an arbitrary desired position, and the degree of freedom in setting the composition when photographing or observing is increased. An effect such as increase can be obtained.

Furthermore, since focus detection can be performed with a good secondary image without distortion, stable focus detection with high accuracy is possible.

[Brief description of the drawings]

FIG. 1 is a schematic view of a main part of a first embodiment according to the present invention.

FIG. 2 is an enlarged explanatory view of a part of the focus detection device of FIG. 1;

FIG. 3 is an explanatory diagram showing a stop and a secondary imaging system in FIG. 1;

FIG. 4 is an explanatory view showing the photoelectric conversion element of FIG. 1;

FIG. 5 is an explanatory view showing a secondary image re-imaged on the photoelectric conversion element in FIG. 1;

FIG. 6 is an explanatory diagram of an electric system according to the first embodiment of the present invention.

FIG. 7 is an explanatory diagram showing the operation of the camera according to the first embodiment of the present invention.

FIG. 8 is an explanatory view showing the convex lens retracting structure of FIG. 1;

FIG. 9 is a schematic view of a main part of a second embodiment according to the present invention.

FIG. 10 is an enlarged explanatory view of a part of the focus detection device of FIG. 9;

FIG. 11 is an explanatory view showing a diffraction phenomenon of the diffractive optical element according to the second embodiment of the present invention.

FIG. 12 is an explanatory diagram showing a function of a diffractive optical element lens according to a second embodiment of the present invention.

FIG. 13 is an explanatory diagram showing a cross-sectional shape of a diffractive optical element configured as a kinoform according to the second embodiment of the present invention.

14 is an explanatory diagram showing a cross-sectional shape of a binary optical element obtained by stepwise approximating the kinoform of FIG.

FIG. 15 is an explanatory diagram showing a diffractive optical element (DOE) retreat structure of FIG. 9;

FIG. 16 is a schematic diagram of a camera showing a conventional example.

FIG. 17 is a schematic view of a camera showing another conventional example.

[Explanation of symbols]

 Reference Signs List 1 shooting lens system 1a exit pupil 2 optical axis of shooting lens system 3 film surface 4 main mirror 5 focusing plate 6 pentaprism 7 eyepiece system 8 sub mirror 9 convex lens 10 paraxial imaging surface 11 infrared cut filter 12 aperture 13 secondary Imaging system 14 Photoelectric conversion element 25 Holding member 26 Convex lens driving means 28 Diffractive optical element (DOE) 101 Photographic lens system 102 Main mirror 103 Focus plate 104 Penta prism 105 Eyepiece lens system 106 Submirror 107 Film surface 108 Focus detecting device 109 Focusing Reflective mirror

Claims (7)

[Claims] 1. An optical apparatus comprising: a first reflecting mirror having a semi-transmissive property for reflecting a light beam from a photographing lens system; and a second reflecting mirror for bending a light beam transmitted by the first reflecting mirror. An optical device comprising an optical member having a light collecting property between the first reflecting mirror and the second reflecting mirror. 2. The optical apparatus according to claim 1, wherein said optical member is retractable to a position which does not interfere with a photographing optical path during photographing. 3. The optical member is disposed between the first reflecting mirror and the second reflecting mirror and on the optical axis of the photographing lens system, and is located outside the optical axis of the photographing lens system during photographing. The optical device according to claim 1, wherein the optical device can be retracted. 4. The optical device according to claim 1, wherein the optical member is a convex lens. 5. The optical apparatus according to claim 1, wherein the optical member is a diffractive optical element. 6. The optical apparatus according to claim 1, wherein the second reflecting mirror folds a light beam transmitted through the first reflecting mirror to a focus detection optical system. 7. A secondary imaging system, wherein the focus detection optical system forms a light flux from a subject image, which is condensed by the optical member and then reflected and guided by a second reflecting mirror, as a secondary image. 7. An optical apparatus according to claim 6, wherein said optical apparatus comprises a photoelectric conversion element for detecting a light amount distribution related to said secondary imaging system.