JP2001042422A - Single-lens reflex camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a finder image bright and to reduce the loss of the light quantity of subject luminous flux guided to an exposure surface in a single-lens reflex camera constituted so that the finder image can be observed even in the midst of an exposure action. SOLUTION: In the mirror box MB of this single-lens reflex camera, a 1st half mirror 6 and a 2nd half mirror 8 are installed. The mirror 6 is constituted so that it can be turned with a turning shaft 6p as a center. When the exposure action is not executed, the mirrors 6 and 8 are positioned in the optical path of the luminous flux L transmitted through a photographing lens 2 and advanced toward a photographic film 14. The sufficient light quantity of object luminous flux is guided to a reticle 16. When the exposure action is executed, the mirror 6 and a sub-mirror unit 10 installed at the bottom part of the box MB are retreated outside the optical path. Since the transmissivity of the mirror 8 is set to be higher than reflectivity, the sufficient light quantity of luminous flux is guided to the exposure surface of the film 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-lens reflex camera capable of observing a finder image even during an exposure operation.

[0002]

2. Description of the Related Art A half mirror is installed at a quick return mirror of a single-lens reflex camera to guide a subject light transmitted through a photographic lens to a finder optical system and a photographic film at the same time, and to observe a finder image even during an exposure operation. Some are possible. The single-lens reflex camera has an advantage that the finder image does not disappear even while the shutter is running, so that it is possible to confirm whether or not the flash device emits light during flash photography, whether or not the model blinks, etc. even during the exposure operation. In addition, there is an advantage that the captured state of the subject can be confirmed during the exposure operation even when the camera is shaken following the movement of the subject during the exposure operation, that is, in so-called panning.

[0003]

However, in the above-mentioned single-lens reflex camera, only a part of the subject light is guided to the finder optical system, so that the finder image becomes darker than that of a normal single-lens reflex camera. Also, since a part of the subject light is guided to the viewfinder optical system during the exposure operation, the amount of the subject light incident on the photographic film even with the same subject brightness and the same F-number as compared with a normal single-lens reflex camera. Is reduced. For this reason, even if the aperture of the taking lens is set to the open side, the shutter time may be delayed, or the range of the photographable distance using the flash device may be narrowed.

An object of the present invention is to allow a finder image to be observed even during an exposure operation, to guide a sufficient amount of subject light to a finder optical system during a photographing preparation operation, and to provide a sufficient amount of subject light during an exposure operation. To provide a single-lens reflex camera that can guide the camera to a photographic film.

[0005]

FIG. 1 shows an embodiment of the present invention.
The following invention will be described in association with. (1) According to the first aspect of the present invention, the incident light flux L is divided and the light flux of the first light amount is divided into the finder optical systems 16 and 1.
The present invention is applied to a single-lens reflex camera having light beam splitting means 6 and 8 for guiding light beams of the second light amount toward the exposure surface at the same time as guiding the light beams toward 8, 20, and 22. The ratio between the first light amount and the second light amount is different between the exposure operation and the non-exposure operation, thereby achieving the above object. (2) The single-lens reflex camera according to the second aspect of the present invention retreats from a light path of a light beam that enters and travels toward an exposure surface, and a viewfinder that locates at least a part of the light beam in the light path. A first mirror 6 that can be switched to a state where it is guided to the optical systems 16, 18, 20, and 22; and a first mirror 6 that is located in the optical path during both the exposure operation and the non-exposure operation, and reflects a part of the light beam, Second mirror 8 for transmitting the remaining light beam
And (3) In the single-lens reflex camera according to the third aspect of the present invention, the first and second mirrors 6 and 8 are overlapped at least during a photographing preparation operation in which the photographer checks a finder image. (4) In the single-lens reflex camera according to the fourth aspect of the present invention, the first mirror 6 and the second mirror 8 have different reflectances. (5) In the single-lens reflex camera according to the fifth aspect of the invention, the transmittance of the second mirror 8 is set to be higher than the reflectance. (6) The single-lens reflex camera according to the sixth aspect of the present invention will be described with reference to FIG. 3 showing an embodiment. When evacuating from the optical path of the second mirror 8, the reflecting surface 8
It moves along a plane substantially parallel to r.

[0006] In the section of the means for solving the above-mentioned problems, which explains the configuration of the present invention, the drawings of the embodiments of the present invention are used to make the present invention easy to understand. However, the present invention is not limited to this.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION First Embodiment FIG. 1 is a diagram showing a schematic configuration of a single-lens reflex camera according to a first embodiment of the present invention. 2 shows a vertical section along the optical axis of the taking lens 2 to be used.
Inside the mirror box MB of the single-lens reflex camera, two half mirrors, that is, a first half mirror 6 and a second half mirror 8 are incorporated. The first half mirror 6 includes a frame member 6b and a semipermeable mirror 6a having a semipermeable film formed by vapor deposition or the like on a surface of a polymer film having a thickness of about several tens of microns called a pellicle. Similarly, the second half mirror 8 is formed by extending a semi-transparent mirror 8a on a frame member 8b.

The first half mirror 6 includes a mirror box M
It is configured to be rotatable around a rotation shaft 6p fixed in B. On the other hand, the second half mirror 8 is a fixed mirror fixed in the mirror box MB. A sub-mirror unit 10 is installed below the mirror box MB, and the arm 10d is rotatable about a rotation shaft 10c fixed to the lower part of the mirror box MB.
A rotating shaft 10b is fixed to the tip of the arm 10d, and the sub-mirror 10a is rotatable about the rotating shaft 10b. Below the sub-mirror unit 10, an AF module 12 for detecting the focus adjustment state of the taking lens 2 is fixed.

A focusing screen 16 is provided above the mirror box MB.
And the condenser lens 18 is fixed. The focusing screen 16 is manufactured by injection molding or compression molding using methacrylic resin as a material. A Fresnel lens 16f is formed on the lower surface of the reticle 16f, and a matte surface 16f is formed on the upper surface.
m is formed. Above the Fresnel lens 18, a pentagonal roof prism 20 (hereinafter, referred to as “pentaprism 20”) is fixed. An eyepiece lens 22 is fixed near the exit surface 20e of the pentaprism 20.

The operation of the single-lens reflex camera configured as described above will be described. At the time of non-exposure operation, or at the time of shooting preparation operation in which the photographer looks into the viewfinder to determine the composition and exposure value, and to check the focus adjustment operation or focus adjustment state,
The first half mirror 6, as shown in FIG.
Are located in the optical path toward the exposure surface of the photographic film 14. Hereinafter, the above-described state of the camera is simply referred to as “non-exposure operation time”. During the non-exposure operation, the sub-mirror unit 10 is also located in the optical path of the subject light beam L toward the exposure surface of the photographic film 14, as shown by the solid line in FIG. That is, during the non-exposure operation, a part of the subject light beam L is reflected by the first half mirror 6 and the second half mirror 8 and proceeds in the direction along the dashed line r in FIG. To form a subject image.

Although FIG. 1 shows a state in which a large gap is provided between the first half mirror 6 and the second half mirror 8 for easy understanding, the gap should be made as small as possible. Is desirable. The reason is that if the gap is large, the distance between the subject light flux L reflected by the first half mirror 6 and guided to the focusing screen 16 and the subject light flux L reflected by the second half mirror 8 and guided to the focusing screen 16 is increased. This is because deviation occurs. FIG. 2 shows the first half mirror 6.
FIG. 5 is a diagram schematically showing a relationship between a gap d between the semi-transmissive mirror 6a of FIG. 1 and the semi-transparent mirror 8a of the second half mirror 8 and a shift amount δ of the subject light beam L. As shown in FIG. 2, the semi-transparent mirror 6a,
The shift amount δ of the subject light beam L when the gap d exists between 6b is obtained by the following equation (1). δ = (1 / SIN45 ゜) × d ≒ 1.414 · d Equation (1)

When the gap d is large, δ also becomes large,
In an extreme case, the finder image becomes a double image, and it is difficult to adjust the focus or confirm the focus adjustment state. To cope with such a problem, (1) by reducing δ to some extent or (2) by increasing the reflectance of the semi-transmissive mirror 6a, the amount of subject light reflected by the semi-transparent mirror 8a and guided to the focusing screen 16 It is effective to relatively reduce.

The single-lens reflex camera shown in FIG.
Assuming that a type of photographic film is used, the allowable diameter of confusion is often set to about 1/30 mm. Then, the subject image formed on the focusing screen 16 is also 1
It is desirable to be able to visually recognize with a resolution of / 30 mm or more.
For that purpose, it is desirable that the above-mentioned δ be 1/30 mm or less. Substituting δ = 1/30 (mm) into the equation (1), the gap d between the semi-transparent mirrors 6a and 8a becomes 1 / (30 ×
1.414) mm ≒ 24 μm or less is desirable.

The above description has been made on the assumption that the single-lens reflex camera shown in FIG. 1 uses a 135 type photographic film. However, the present invention is also applicable to cameras using films of other formats and electronic cameras. In this case, the permissible circle of confusion corresponding to the film size or the area size of the image sensor is determined, so it is necessary to determine the upper limit of the gap d according to the permissible circle of confusion.

A part of the subject light beam L (light beam near the center of the screen) transmitted through the first half mirror 6 and the second half mirror 8 described above is reflected by the sub-mirror 10a and follows the dashed line t in FIG. Go in the direction, mirror box M
It is led to the AF module 12 located below B. A
The F module 12 detects the focal position of the photographing lens 2. A focus detection circuit (not shown) connected to the AF module 12 moves the photographing lens 2 based on a signal output from the AF module 12. Find the direction and the amount of movement. A lens drive circuit (not shown) drives the photographing lens 2 based on a signal output from the focus detection circuit described above to perform focus adjustment.

Next, the operation of the single-lens reflex camera shown in FIG. 1 during exposure will be described. When the photographer operates a release button (not shown), the first half mirror 6 is flipped up by a mirror driving mechanism (not shown) in a direction indicated by an arrow u in FIG. That is, the first half mirror 6 retreats from the optical path of the subject light beam L toward the exposure surface of the photographic film 14. At this time, the sub mirror unit 1
1 also rotates in the direction shown by the arrow d in FIG.
The sub-mirror 10a turns counterclockwise about the turning shaft 10b. Then, the sub-mirror unit 10
Is retracted from the above optical path of the subject light beam L by being folded as shown by the two-dot chain line in FIG.

The luminous flux L of the subject transmitted through the taking lens 2 is
Part of the light is reflected by the second half mirror 8, passes through the first half mirror 6 that has been flipped upward, and passes through the reticle 1.
A subject image is formed on the mat surface 16m of No. 6. On the other hand, the subject light beam L transmitted through the second half mirror 8 enters the exposure surface of the photographic film 14 as a focal plane shutter (not shown) travels. Thereafter, the first half mirror 6 returns to the state shown in FIG. 1, and a series of exposure operations is completed.

Here, the reflectance and the transmittance of the first half mirror 6 and the second half mirror 8 will be described.
The reflectance of the first half mirror 6 is R1, the transmittance is T1, the reflectance of the second half mirror 8 is R2, and the transmittance is T2.
Then, the light amount ratio of the subject light guided to the reticle and the exposure surface of the photographic film 14 during the non-exposure operation / exposure operation is as follows. (A) Light amount ratio of subject light beam L guided to reticle 16 during non-exposure operation D1 = R1 + T1 × R2 × T1 Expression (2) (b) Light amount ratio D of subject light beam L guided to reticle plate 16 during exposure operation = R2 × T1 Expression (3) Light amount ratio of subject light beam L guided to the film surface D3 = T2 Expression (4)

The meaning of the above equation will be described. Equation (2) indicates that the subject light flux L guided to the focusing screen 16 is equal to the first light flux L.
The portion (R1) reflected by the half mirror 6 transmits through the first half mirror 6 (T1), is reflected by the second half mirror (× R2), and transmits again through the first half mirror 6 (× T
1) It means that it is obtained by the sum with the amount to be done. Equation (3) indicates that the subject light beam L guided to the focusing screen 16 when the first half mirror is up is reflected by the second half mirror 8 (R2) and transmitted through the first half mirror 6. (× T1). The expression (4) means that the light passes through the second half mirror 8 (T2) and reaches the exposure surface of the photographic film 14.

The single-lens reflex camera according to the present invention guides as much light of the subject as possible to the focusing screen 16 during the non-exposure operation (when observing the viewfinder image) and the finder image during the exposure operation (when photographing). It is an object of the present invention to guide as much light as possible to the film surface while maintaining an observable state. To achieve this goal, the first
It is desirable that the half mirror 6 and the second half mirror 8 have different reflectances. It is desirable that the reflectance of the first half mirror 6 be set higher than the reflectance of the second half mirror 8. Further, even during the exposure operation, the second half mirror 8 existing in the optical path of the subject light beam L
It is desirable to set the transmittance higher than the reflectance.

For example, the reflectance R of the first half mirror 6
1 is set to 70%, and the transmittance is set to 30%. Also, the second
The reflectance R2 of the half mirror 8 is set to 20%, and the transmittance T2 is set to 80%. When these values are substituted into Expressions (2) to (4), the light amount ratio of light reaching the reticle 16 or the film surface becomes a value represented by the following Expressions (5) to (7). D1 = 0.7 + 0.3 × 0.2 × 0.3 = 0.718 Equation (5) D2 = 0.2 × 0.3 = 0.06 Equation (6) D3 = 0.8 Equation ( 7)

At the time of non-exposure operation, as shown in equation (5), 7
1.8% of the light is guided to the reticle. Therefore,
For example, compared to a conventional single-lens reflex camera in which a half mirror having a reflectance of 35% and a transmittance of 65% is fixed in a mirror box, the finder image becomes brighter, and the focus adjustment state can be easily confirmed. it can.

Also, at the time of the exposure operation, as shown in the equation (6), the subject light flux of 6% light amount is guided to the focusing screen, so that it is checked whether or not the flash light is emitted at the time of flash photography, and the subject's eye It is possible to easily confirm the presence or absence of a blow, or to capture a subject during panning. At this time, as shown in the equation (7),
% Of the subject light flux is guided, so that the photographing lens 2 can be set to a smaller aperture or a faster shutter speed as compared with the above-described single-lens reflex camera according to the related art. In addition, it is possible to extend the reach of flash light during flash photography (the maximum photography distance at which an appropriate exposure can be obtained by flash photography).

In the above embodiment, an example in which the first half mirror 6 is flipped up during the exposure operation has been described. However, depending on the shooting conditions, the first half mirror 6 should not be flipped up during the exposure operation. Is also possible. This makes it possible to use the first half mirror 6 as a substitute for the ND filter. As an example of the transmittance set for the first half mirror 6 and the second half mirror 8, an example in which the transmittance is 30% and 80%, respectively, has been described above. If the first half mirror 6 is prevented from jumping up during the exposure operation under this condition, 0.3 × 0.8 = 0.2
4, that is, approximately 1/4 of the subject light L is guided to the exposure surface of the photographic film 14. This makes it possible to perform dimming of about 2 EV.

When portrait photography or the like is performed under relatively high brightness such as during the daytime, it may be desirable to blur the background and foreground by opening the aperture and to make the main subject stand out. If the sensitivity of the loaded photographic film is relatively high, it may be difficult to set the aperture at or near the maximum even at the highest shutter speed. In such a case, by photographing without raising the first half mirror 6 in the single-lens reflex camera of the present embodiment, it is possible to reduce the amount of the subject reaching the film surface. Therefore, even when a film having high sensitivity under high luminance is used, it is easy to set an arbitrary aperture value. In addition, it is easy to select a relatively slow shutter speed under high brightness, and the degree of freedom in drawing such as intentionally blurring the subject image can be greatly increased. At this time, in comparison with the case where the ND filter is attached and detached in front of the imaging lens 2, the single-lens reflex camera according to the present embodiment can set the imaging condition of rapidly performing or not performing the dimming. Further, since it is not necessary to prepare a plurality of types of ND filters having a filter diameter corresponding to the type of the photographing lens 2 (the size of the front frame), there is no need to find an ND filter having a size corresponding to the type of the photographing lens. . Further, there is no need to prepare a plurality of ND filters of a size corresponding to the type of the photographing lens, so that the cost is excellent.

Second Embodiment FIG. 3A is a diagram illustrating a schematic configuration of a single-lens reflex camera according to a second embodiment of the present invention. FIG. 3 (a)
In FIG. 7, the same components as those in FIG. 1 showing the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. The description will focus on the differences from the first embodiment.

In the first embodiment, the first half mirror 6 shown in FIG. 1 is rotatable about a rotation shaft 6p. Then, the first half mirror 6 is swung up and retracted from the optical path of the subject light beam L toward the exposure surface of the photographic film 14, and the first half mirror 6 is lowered and positioned in the above optical path, and It was possible to switch at least a part to a state in which it was guided to a finder optical system. On the other hand, in the single-lens reflex camera according to the second embodiment, the mirror 60 is moved prior to the exposure operation.
The slide retracts along a plane substantially parallel to the reflection surface of the second half mirror 8 as described later.

FIG. 3B is a partially enlarged view of the mirror 60 and the second half mirror 8, and FIG.
The configuration of the single-lens reflex camera according to the second embodiment will be described with reference to FIG.

As shown in FIG. 3B, the mirror 60
Is a back-surface reflecting mirror in which an anti-reflection thin film 60ar is deposited on the front surface of a transparent parallel flat plate 60g made of optical glass or the like, and a reflection film 60r of aluminum or silver is deposited on the back surface. Even when the mirror 60 is positioned in the optical path of the subject light beam L toward the exposure surface of the photographic film 14, a part of the subject light beam is transmitted to the AF module 12 via the sub-mirror unit 10 disposed behind the mirror 60. Is configured to be guided. That is, a large number of pinholes are formed partially on the reflection film 60r of the mirror 60, or are randomly arranged. And
A part of the subject light beam L transmitted through the semi-permeable membrane or the pinhole is reflected by the sub-mirror 10, travels along the dashed line t, and enters the AF module 12.

The reflectance of the mirror 60 is set to a value close to 100%. This mirror 60 is the second half mirror 8
Is held by a mirror driving mechanism (not shown) in a state having a gap d between the semi-transparent mirror 8a and the semi-permeable film 8r formed by vapor deposition or the like. The mirror 60 moves along a plane substantially parallel to the semipermeable membrane 8r of the second half mirror 8. At this time, the gap d is desirably set to a predetermined value so that the semipermeable film 8r of the second half mirror 8 and the reflective film 60r of the mirror 60 are not rubbed and damaged. Alternatively, when the movement of the mirror 60 is started, first, the gap d may move in a direction in which the gap d increases, and then the mirror 60 may move along a plane substantially parallel to the semi-permeable membrane 8r of the second half mirror 8. The gap d will be described again at the end of the description of the present embodiment.

Next, the operation of the single-lens reflex camera according to the second embodiment will be described. During the non-exposure operation, the mirror 60 is located in the optical path of the subject light beam L toward the exposure surface of the photographic film 14, and reflects almost all of the subject light beam L except for the light beam guided to the AF module 12. The luminous flux reflected by the mirror 60 is represented by a dashed line r
To form an object image on the reticle 16. As described above, since almost all of the subject light beam L is guided to the focusing screen 16, the finder image becomes bright. Therefore, the photographer can easily confirm the focus adjustment state and the like.

During the exposure operation, the mirror 60 is driven by a mirror driving mechanism (not shown) in a direction substantially perpendicular to the plane of FIG. Then, the mirror 60 retracts out of the optical path where the subject light beam L is directed to the exposure surface of the photographic film 14. At this time, the arm 10d of the sub-mirror unit 10 also turns in the direction indicated by the arrow d in FIG. 1, and the sub-mirror 10a turns counterclockwise about the turning shaft 10b. Then, the sub-mirror unit 10 is folded as shown by the two-dot chain line in FIG.

The luminous flux L of the subject transmitted through the taking lens 2 is
A part of the light is reflected by the second half mirror 8, and the reticle 16
A subject image is formed on the mat surface 16m. On the other hand, the subject light beam L transmitted through the second half mirror 8 enters the exposure surface of the photographic film 14 as a focal plane shutter (not shown) travels. Thereafter, the mirror 60 returns to the position at the time of the non-exposure operation, and a series of exposure operations is completed.

In the single-lens reflex camera according to the second embodiment, the reflectance and the transmittance of the semi-transmissive mirror 8a of the second half mirror 8 are set to, for example, 85% and 15%. During the exposure operation, since the mirror 60 is retracted as described above,
15% of the light of the photographing light beam L is guided to the focusing screen 16, and 85% of the light is guided to the exposure surface of the film 14.

Therefore, during the non-exposure operation, the finder image is significantly different from that of a conventional single-lens reflex camera in which, for example, a half mirror having a reflectance of 35% and a transmittance of 65% is fixed in a mirror box. It becomes bright, and the focus adjustment state can be easily confirmed.

Also, during the exposure operation, the subject light of 15% light amount is guided to the focusing screen, so as to confirm the presence or absence of the emission of the flash light at the time of flash photography, and to check the eye of the object as in the first embodiment. It is possible to easily confirm the presence or absence of a blow, or to capture a subject during panning. At this time, since subject light of 85% light amount is guided to the film surface, the photographing lens 2 can be set to a smaller aperture or a higher shutter speed than the single-lens reflex camera according to the related art described above. Can be set. Further, at the time of flash photography, it is possible to make the reach of the flash light substantially long.

In the above description of the embodiment, an example has been described in which the mirror 60 is driven to the near side in FIG. 3A during the exposure operation, but it may be driven to the far side in FIG. . Alternatively, the second half mirror 8 may be driven in the lower left direction in FIG. 3A along a plane substantially parallel to the semi-transmissive mirror 8a.

In the single-lens reflex camera according to the second embodiment, the mirror 60 is driven along a plane substantially parallel to the semi-transparent mirror 8a of the second half mirror 8 during the exposure operation. The following effects are also obtained. That is, since the mirror 60 is driven while the gap d between the mirror 60 and the semi-transmissive mirror 8a of the second half mirror 8 is kept substantially constant, no negative pressure is generated. In other words, instead of being driven in the direction in which the two flat members are peeled off,
Driven in the so-called shear direction, there is almost no negative pressure between these two members. Therefore, the driving force of the mirror 60 can be reduced, the actuator for driving the mirror 60 can be reduced in size, and the driving energy can be reduced. In addition, since the load caused by the negative pressure generated as described above is not applied to the half mirror 8, it is possible to suppress the finder image from being disturbed due to the half mirror 8a of the half mirror 8 fluttering.

In the above embodiment, the mirror 60 has been described as a back mirror. The reason is that if the gap d between the reflection surface of the mirror 60 (reflection film 80r) and the reflection surface of the second half mirror 8 (semi-transmissive film 8r) is too large, the finder may be retracted during the exposure operation. This is because the movement of the image becomes conspicuous. That is, if the mirror 60 is a surface mirror, the gap (distance) between the reflective film 80r and the semi-permeable film 8r is the sum of the dimension d in FIG. 3B and the thickness of the mirror 60. For such a reason, the mirror 60 is constituted by a back mirror. If the movement of the finder image does not matter much, the mirror 60 may be constituted by a surface mirror. Alternatively, by forming the mirror 60 from a film such as a pellicle, the amount of movement of the image can be reduced even when the mirror 60 is a surface mirror.

As described above, the mirror 60 is exposed during the exposure operation.
In order to minimize the movement of the finder image when the camera is retracted, it is desirable to make the gap d shown in FIG. 3B as small as possible. On the other hand, in order to prevent the semi-permeable film 8r of the second half mirror 8 and the reflective film 60r of the mirror 60 from being rubbed and damaged when the mirror 60 performs the retracting / restoring operation, the above-described operation is performed. It is desirable that the gap d has a certain amount. Therefore, if the gap d is determined by giving priority to preventing the scratch, if the movement of the finder image is conspicuous, the angular relationship between the mirror 60 and the second half mirror 8 is determined as follows. It is good to decide.

Except for some special ones, in a single-lens reflex camera, in order to maintain the conjugation between the image formed on the image plane (exposure plane of the photographic film) and the image formed on the reticle, the incidence of the reflex mirror The corner is set at 45 °. If there is an error in the incident angle of the reflex mirror, the conjugation is lost, and a shift occurs between the image formed on the reticle and the image formed on the exposure surface of the photographic film. This contributes to the parallax generated by a single-lens reflex camera. By utilizing this property in reverse, for example, the incident angle of the mirror 60 is set to 45 °, while the incident angle of the second half mirror is set to be smaller than 45 °. In other words, in FIG.
Rotate the half mirror 8 in the counterclockwise direction. Then
Since the subject image reflected on the second half mirror 8 and formed on the focusing screen 16 moves leftward in FIG. 3A,
The movement amount of the finder image described above decreases. At this time,
The imaging surface of the subject light beam L reflected by the second half mirror 8 has a slight inclination with respect to the mat surface 16m of the reticle 16. However, the inclination is so small that it can be ignored. Further, since the second half mirror 8 is extremely thin, even if the angular position of the second half mirror 8 is changed as described above, the effect on the image formed on the photographic film 14 can be almost ignored.

Third Embodiment FIG. 4 is a diagram illustrating a schematic configuration of a single-lens reflex camera according to a third embodiment of the present invention. In FIG. 4, the same components as those in FIG. 1 showing the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. The description will focus on differences from the first or second embodiment. .

In the first embodiment, the first half mirror 6 shown in FIG. 1 is rotatable about a rotation shaft 6p. Then, the first half mirror 6 is swung up so as to be retracted from the optical path of the subject light beam L entering the exposure surface of the photographic film 14, and the first half mirror 6 is lowered and positioned in the optical path. Thus, at least a part of the light beam can be switched to a state of being guided to the finder optical system. Further, in the second embodiment, the mirror 60 shown in FIG. 3A slides and retracts along a plane substantially parallel to the semi-permeable film 8r of the second half mirror 8 during the exposure operation. On the contrary,
In the single-lens reflex camera according to the third embodiment, two half mirrors 61 and 80 are provided in the mirror box MB, and the first half mirror 61 provided on the film surface side is the second half mirror 61 during the exposure operation. The slide retracts along a plane substantially parallel to the reflection surface of the mirror 80a. At this time, unlike the first and second embodiments, the first half mirror 61 is located closer to the film surface than the second half mirror 80 is.

The configuration of the single-lens reflex camera according to the third embodiment will be described below with reference to FIG.

The first half mirror 61 comprises a frame member 61b and a semi-transparent mirror 61a having a semi-permeable film formed by vapor deposition or the like on a polymer film having a thickness of about several tens of microns called a pellicle film. . Similarly, the second half mirror 80 is formed by extending a semi-transparent mirror 80a on a frame member 80b.

The second half mirror 80 is a fixed mirror fixed inside the mirror box MB. Second half mirror 8
The transmittance of 0 is set to T2, and the reflectance is set to R2. First
The half mirror 61 is a semi-transparent mirror 8 of the second half mirror 80.
0a is held by a mirror holding mechanism (not shown) with a predetermined gap. First half mirror 61
Is set to T1 and the reflectance is set to R1. Specific examples of T1, T2, R1, and R2 will be described later.

As described in the second embodiment,
The first half mirror 61 moves along a plane substantially parallel to the semi-transmissive mirror 80a of the second half mirror 80. At this time, the above-mentioned gap is set so that the semi-transmissive mirror 80a of the second half mirror 80 and the reflection film 61r of the first half mirror 61 do not rub against each other and are not damaged. Alternatively, as described in the second embodiment, the first half mirror 6
At the start of movement of the first half mirror 80, it may first move in the direction in which the gap increases, and then move along a plane substantially parallel to the semi-transmissive mirror 80a of the second half mirror 80.

Next, the operation of the single-lens reflex camera according to the third embodiment will be described. During the non-exposure operation, the first half mirror 61 moves the subject light beam L
4 is located in the optical path toward the exposure surface. That is,
In the state shown in FIG. At this time, the second half mirror 80 and the first half mirror 6 of the subject light beam L
An image of a subject is formed on the reticle 16 by the light flux reflected by the light 1 and traveling along the dashed line r. The remaining beam is the second
The light passes through the half mirror 80 and the first half mirror 61, and a part of the light flux is reflected by the sub-mirror 10 a downward in FIG. 4, travels along the dashed line t, and enters the AF module 12.

During the exposure operation, the first half mirror 61 is driven by a mirror driving mechanism (not shown) in a direction substantially perpendicular to the plane of FIG. Then, the first half mirror 61 retreats out of the optical path of the subject light beam L toward the exposure surface of the photographic film 14. At this time, the arm 10d of the sub-mirror unit 10 also turns in the direction indicated by the arrow d in FIG. 1, and the sub-mirror 10a turns counterclockwise about the turning shaft 10b. Then, the sub-mirror unit 10 is folded as shown by a two-dot chain line in FIG. 1 and retracts out of the optical path.

The luminous flux L transmitted through the photographing lens 2 is
A part thereof is reflected by the second half mirror 80, and the reticle 1
A subject image is formed on the mat surface 16m of No. 6. On the other hand, the subject light beam L transmitted through the second half mirror 80 is incident on the exposure surface of the photographic film 14 as a focal plane shutter (not shown) travels. Thereafter, the first half mirror 61 returns to the position at the time of the non-exposure operation, and a series of exposure operations is completed.

In the single-lens reflex camera according to the third embodiment, the transmittance and the reflectance of the semi-transmissive mirror 61a of the first half mirror 61 are set to, for example, 30% and 70%. Then, the reflectance and the transmittance of the semi-transmissive mirror 80a of the second half mirror 80 are set to, for example, 20% and 80%. During the exposure operation, the first half mirror 61 retracts as described above, so that 20% of the light of the photographic light beam L is guided to the focusing screen 16 and 80% of the light is
4 to the exposure surface. On the other hand, during the non-exposure operation, the second
The amount reflected by the semi-transparent mirror 80a of the half mirror 80 (80
%), And transmits through the semi-transparent mirror 80a, and the first half mirror 61
Is reflected by the semi-transmissive mirror 61a and again transmitted through the semi-transparent mirror 80a (20% × 70% × 20% = 2.8%). I will

As described above, during the non-exposure operation, the light of 82.8% of the light flux L of the subject is guided to the focusing screen 16. During the exposure operation, 20 out of the subject light beam L
% Of light is guided to the focusing screen 16, and 80% of light is guided to the exposure surface of the photographic film 14. Therefore,
During the non-exposure operation, for example, the reflectance is 35% and the transmittance is 65%
The finder image becomes brighter than in a conventional single-lens reflex camera in which the half mirror is fixed in a mirror box, and the focus adjustment state can be easily confirmed.

Also, during the exposure operation, the subject light beam L having a light quantity of 20% is guided to the focusing screen. Therefore, as in the first and second embodiments, it is checked whether or not flash light is emitted during flash photography. In addition, it is possible to easily confirm whether or not the subject has blinked, or to capture the subject during panning. At this time, since 80% of the subject light is guided to the film surface, as in the first and second embodiments, the photographic lens 2 can be moved compared to the single-lens reflex camera according to the above-described conventional technique. It is possible to set a smaller aperture or a faster shutter speed. First, it is also possible to substantially extend the reach of the flash light during flash photography.
This is the same as the second embodiment.

In the above description of the embodiment, an example has been described in which the first half mirror 61 is driven to the near side in FIG. 4 during the exposure operation. However, the first half mirror 61 may be driven to the far side in FIG. . Alternatively, the second half mirror 80 may be driven in the lower left direction in FIG. 4 along a plane substantially parallel to the semi-transmissive mirror 80a.

In the single-lens reflex camera according to the third embodiment, the first half mirror 61 is driven along a plane substantially parallel to the semi-transparent mirror 80a of the second half mirror 80 during the exposure operation. In addition to the above, it also has the effect described in the second embodiment. That is, the first half mirror 61
It is difficult to generate a negative pressure during the operation of the first half mirror 6.
1, the driving force of the first half mirror 61 can be reduced, and the driving energy can be reduced. In addition, since the load due to the negative pressure is less likely to be applied to the semi-transmissive mirrors 61a and 80a of both the first half mirror 61 and the second half mirror 80, it is possible to prevent the semi-transmissive mirrors 61a and 80a from flapping and disturbing the finder image.

Also in the third embodiment, if the gap between the semi-transmissive mirror 61a of the first half mirror 61 and the semi-transmissive mirror 80a of the second half mirror 80 is too large, the first half mirror 61 is exposed during the exposure operation. When retracted, the movement of the finder image becomes conspicuous. In order to minimize the movement of the finder image, it is desirable to make the gap between the semi-transparent mirrors 61a and 80a as small as possible. On the other hand, in order to prevent the semi-transparent mirrors 61a and 80a from rubbing each other when the first half mirror 61 performs the retracting / restoring operation, a certain amount of the above-described gap is secured. Is desirable. Therefore, as a result of determining the gap giving priority to preventing the above scratches,
If the movement of the finder image is conspicuous, the same operation as in the second embodiment may be performed. That is, the second half mirror 80 may be turned in the counterclockwise direction in FIG.

In the above description of the embodiment, the example in which the first half mirror 61 is retracted outside the optical path of the subject light beam L toward the exposure surface of the photographic film 14 during the exposure operation has been described. The first half mirror 61 may remain in the optical path even during the exposure operation as described in the embodiment. By doing so, the first
The half mirror 61 can be used as a substitute for the ND filter.

As described above, the single-lens reflex cameras according to the second and third embodiments are also similar to the single-lens reflex cameras according to the first embodiment only if they use a 135 type silver halide film. The present invention is also applicable to silver halide film cameras and electronic cameras of other formats.

In the correspondence between the above-described embodiment and the claims, the reticle 16, the condenser lens 18, the pentaprism 20, and the eyepiece lens 22 constitute the finder optical system, and the first half mirror 6 and the second half mirror 8. Are the light beam splitting means, the first half mirror 6, the mirror 60
The first half mirror 61 and the second half mirror 8 constitute a first mirror, and the second half mirror 8 and the second half mirror 80 constitute a second mirror.

[0060]

As described above, according to the present invention, the following effects can be obtained. (1) According to the first aspect of the present invention, the light amount ratio of the luminous flux guided toward the finder optical system and the exposure surface is made different between the time of the exposure operation and the time of the non-exposure operation. A light beam having a light amount ratio suitable for the exposure operation can be guided to the finder optical system and the exposure surface. (2) According to the second aspect of the present invention, a state in which the light beam is retracted from the optical path of the light beam that enters and travels toward the exposure surface, and at least a part of the light beam that is located in the optical path is transmitted to the finder optical system. A first mirror that can be switched to a guiding state, and a second mirror that is located in the optical path during both the exposure operation and the non-exposure operation and reflects a part of the light beam and transmits the remaining light beam.
With such a mirror, a light beam having a light amount ratio suitable for the exposure operation and the non-exposure operation can be guided to the finder optical system and the exposure surface. (3) According to the invention described in claim 3, at least:
At the time of the photographing preparation operation in which the photographer checks the finder image, the first and second mirrors are superimposed, so that the amount of light flux guided to the finder optical system can be increased, and the finder image can be brightened. (4) According to the fourth aspect of the present invention, since the first mirror and the second mirror have different reflectances, the luminous flux having a light amount ratio suitable for the exposure operation and the non-exposure operation is transmitted to the finder optical system. It can be led to the exposure surface. (5) According to the invention described in claim 5, both in the exposure operation and in the non-exposure operation, the light beam is located in the optical path of the light beam that enters and travels toward the exposure surface, and reflects a part of the light beam. By setting the transmittance of the second mirror, which transmits the remaining light flux, to be higher than the reflectance, the light quantity ratio of the light flux traveling toward the exposure surface can be increased. Therefore, the aperture of the taking lens can be set to a small aperture, a faster shutter speed can be set, and the reach of flash light during flash shooting can be extended. (6) According to the invention described in claim 6, when the first mirror is retracted from the optical path of the light beam that enters and travels toward the exposure surface, the first mirror moves to a plane substantially parallel to the reflection surface of the second mirror. By moving along, it is possible to suppress the generation of an attractive force between the first and second mirrors due to the negative pressure, and it is possible to prevent the first and second mirrors from rattling and disturbing the finder image.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration of a single-lens reflex camera according to a first embodiment of the present invention.

FIG. 2 is a diagram schematically illustrating a relationship between a gap d between a semi-transmissive mirror of a first half mirror and a semi-transmissive mirror of a second half mirror and a shift amount δ of a subject light beam L.

FIG. 3 is a diagram illustrating a schematic configuration of a single-lens reflex camera according to a second embodiment of the present invention.

FIG. 4 is a diagram illustrating a schematic configuration of a single-lens reflex camera according to a third embodiment of the present invention.

[Explanation of symbols]

2 ... Shooting lens 6, 61 ...
First half mirrors 6a, 61a ... Semi-transparent mirrors 8, 80 ...
Second half mirror 8a, 80a ... Semi-transparent mirror 10 ...
Sub-mirror unit 12 ... AF module 14 ...
Photographic film 16 ... Focusing plate 60 ...
Mirror L… Subject light flux MB…
Mirror box

Claims (6)

[Claims] 1. A single-lens reflex camera having a light beam splitting means for splitting an incident light beam and guiding a first light amount toward a finder optical system and simultaneously guiding a second light amount toward an exposure surface. 2. The single-lens reflex camera according to claim 1, wherein a ratio between the first light amount and the second light amount is different between an exposure operation and a non-exposure operation. 2. A first switchable state between a state of being retracted from an optical path of a light beam entering and traveling toward an exposure surface and a state of being located in the optical path and guiding at least a part of the light beam to a finder optical system. A mirror in the optical path during both the exposure operation and the non-exposure operation,
A second mirror that reflects a part of the light beam and transmits the remaining light beam. 3. A single-lens reflex camera according to claim 2, wherein said first and second mirrors are overlapped at least during a photographing preparation operation in which a photographer checks a finder image. . 4. The single-lens reflex camera according to claim 2, wherein the first mirror and the second mirror have different reflectances. 5. The single-lens reflex camera according to claim 2, wherein the second mirror has a transmittance set higher than a reflectance. 6. The single-lens reflex camera according to claim 2, wherein said first mirror is a plane substantially parallel to a reflection surface of said second mirror when retracting from said optical path. A single-lens reflex camera characterized by moving along.