JP2004078083A - Digital single-lens reflex camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital single-lens reflex camera (SLR) which can be provided with a low-pass filter and IR cut filter with substantially no addition of changes to major mechanisms of silver salt film SLRs and with substantially no addition of restrictions to the basic performance of the camera. <P>SOLUTION: The digital SLR is provided with the low-pass filter 11 having a large thickness between a lens mount surface 1AS and a quick return mirror 3 and is provided with the IR cut filter 12 of a small thickness between a shutter mechanism 7 and an imaging device 8. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a digital single-lens reflex camera, and more particularly to a single-lens reflex digital camera that captures and records image information using a CCD or the like as an image sensor.
[0002]
[Prior art]
Digital single-lens reflex cameras that use single-lens reflex cameras for silver halide films allow the use of accessories such as interchangeable lenses for shooting and external strobes used in film-lens reflex cameras without changing system compatibility. It is customary to consider user convenience in this way. Therefore, it is most reasonable to set the light-receiving surface of an image sensor represented by a CCD or the like on the focal plane of a photographing lens based on the mechanism of a film-lens reflex camera, and many such digital single-lens reflex cameras are used. Proposed.
[0003]
In a digital camera using such a CCD or the like as an image sensor, the pixels of the image sensor are arranged with regularity. Therefore, if the image sensor is used as it is, the influence of aliasing noise due to the spatial high frequency of the subject. Receive. In order to prevent this, an optical low-pass filter is generally arranged on the front surface of the image sensor. Further, in order to correct the spectral sensitivity characteristics of the imaging device, it is common to arrange an infrared light cut filter for reducing light having a wavelength longer than a predetermined wavelength.
[0004]
On the other hand, even when the image pickup device has an electronic shutter function, light must be shielded so that subject light that has passed through the lens does not hit the image pickup device during the transfer process of charges accumulated after image pickup. A focal plane shutter is required. If the image pickup device does not have an electronic shutter function, the shutter function at the time of image pickup by the image pickup device must be realized by a mechanical shutter like a film camera, and a focal plane shutter is also required.
[0005]
That is, the digital single-lens reflex camera based on the mechanism of the conventional silver halide film-lens reflex camera is configured as follows.
{Circle around (1)} An image sensor is provided on the focal plane of the taking lens instead of the film.
(2) A focal plane shutter is provided immediately before the image sensor.
(3) A quick return mirror is arranged between the focal plane shutter and the lens mounting mount.
In addition to the arrangements of (4) (1) to (3), the above-mentioned low-pass filter and infrared light cut filter are arranged at appropriate places.
[0006]
Japanese Patent Application Laid-Open No. 8-313776 discloses a digital single-lens reflex camera in which a low-pass filter and an infrared light cut filter are separately disposed before and after a focal plane shutter as the above configuration (4).
[0007]
[Problems to be solved by the invention]
In the digital single-lens reflex camera disclosed in Japanese Patent Application Laid-Open No. 8-313776, the following considerations are necessary when using a silver halide film single-lens reflex camera as a digital camera.
[0008]
That is,
{Circle around (1)} In order to provide a low pass filter between the quick return mirror and the AF sub-mirror and the focal plane shutter, it is necessary to increase the distance between the quick return mirror and the AF sub-mirror and the focal plane shutter.
{Circle around (2)} In order to provide a low-pass filter between the focal plane shutter and the image sensor, it is necessary to increase the distance between the focal plane shutter and the image sensor.
[0009]
As described above, it is very difficult to dispose the low-pass filter without changing the installation position or the mechanism of the quick return mirror, the AF sub-mirror, or the shutter.
[0010]
The present invention provides a low-pass filter or an infrared cut filter with little change to the main mechanism of a silver halide film-lens reflex camera, such as a shutter mechanism and a quick return mirror, and almost no restriction on the basic performance of the camera. It is an object of the present invention to provide a digital single-lens reflex camera in which two optical filters represented by (1) are arranged.
[0011]
[Means for Solving the Problems]
In the digital single-lens reflex camera according to the first aspect of the present invention, there is provided an image pickup device in which a subject light flux incident via a photographing interchangeable lens mounted on a lens mounting surface of a lens mount forms an image, and a lens mounting surface and an image pickup device. A non-photographing, at least a part of the subject light beam that has passed through the interchangeable lens for photographing is guided to the observation optical system, and at the time of photographing, a quick return mirror that allows the subject light beam to enter the image sensor; A shutter mechanism provided between the quick return mirror and the image sensor; a first optical filter having a first thickness provided between the lens mounting surface and the quick return mirror; a shutter mechanism and the image sensor And a second optical filter that is thinner than the first optical filter.
It is preferable that the first optical filter is a low-pass filter and the second optical filter is an infrared light cut filter.
The infrared light cut filter is composed of an infrared light cut vapor deposition film deposited on the cover glass of the imaging device, or is disposed immediately before the cover glass of the imaging device, and the infrared light cut vapor deposition film is deposited on the subject side. It may be thin glass. Alternatively, the infrared light cut filter may be formed of an infrared light cut glass that is disposed immediately before the cover glass of the imaging device and absorbs infrared light.
As the shutter mechanism, a focal plane shutter can be adopted.
According to a seventh aspect of the present invention, there is provided a digital single-lens reflex camera including the imaging device of the first aspect, a quick return mirror, and a shutter mechanism, and an infrared light between the lens mounting surface of the lens mount and the quick return mirror. The cut filter is characterized in that a low-pass filter having a single birefringent plate is provided between the shutter mechanism and the image sensor.
In this digital single-lens reflex camera, the infrared light cut filter can be a thin glass having an infrared light cut deposition film deposited on the subject side, or an infrared light cut glass that absorbs infrared light.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
-1st Embodiment-
FIG. 1 and FIG. 2 are central cross-sectional views of the digital single-lens reflex camera showing the first embodiment, and show a mirror-down state of a quick return mirror. The mirror down state is a so-called finder observation state. In FIGS. 1 and 2, reference numeral 1 denotes a camera body, and a photographing interchangeable lens 2 is detachably mounted on a lens mount 1A of the camera body 1. In the mirror-down state shown in FIGS. 1 and 2, a part of the subject light beam L <b> 1 transmitted through the lens mount 1, specifically, the photographing interchangeable lens 2 mounted on the lens mounting surface 1 </ b> AS is reflected by the quick return mirror 3 to the finder section 6. Is done. That is, a part of the light beam of the subject is guided to the observation optical system by the quick return mirror 3, and the subject can be observed from the finder. The remaining subject light flux L2 transmitted through the quick return mirror 3 is reflected by the sub mirror 4 to the autofocus (AF) module 5. The autofocus module 5 outputs a signal corresponding to the focus adjustment state of the photographing lens 2 based on the incident subject light beam.
[0013]
At the time of photographing (when fully pressed), the quick return mirror 4 is in a mirror-up state, as shown by the two-dot chain line in FIG. 2, and the subject light beam L1 transmitted through the interchangeable lens for photography 2 is blocked by the quick return mirror 3. The entire amount goes to the light receiving element 8a of the image pickup device 8 without any change. When the focal plane shutter 7 is driven to open, the photographing light beam L1 enters the image pickup device 8 to photograph the subject.
[0014]
In the digital single-lens reflex camera 1 having such a configuration, the low-pass filter 11 is disposed between the mount surface (lens mounting surface) 1AS of the lens mount 1A of the interchangeable lens 2 for photography and the quick return mirror 3. That is, as shown in FIG. 2, the low-pass filter 11 is located in a space between the trajectory 3a of the tip when the quick return mirror 3 is operated and the lens mount surface 1AS.
[0015]
On the other hand, on the surface of the cover glass 8b of the imaging device 8, a deposition film 12 having an infrared light cut effect is deposited. That is, the vapor deposition film 12 is used as an infrared light cut filter without providing a separate infrared light cut filter. The thickness of the vapor deposition film 12 is usually several μm to several tens μmm, and the same effect as the case where the infrared light cut filters are separately arranged can be obtained without changing the arrangement of the focal plane shutter 7 at all.
[0016]
The thickness of the low-pass filter 11 is inevitably determined by the material of the birefringent plate and the pixel pitch of the image sensor. Usually, two birefringent plates having different separation directions are bonded together with a phase plate interposed therebetween. Therefore, it is difficult to reduce the total thickness. However, in the silver halide film single-lens reflex camera, the space between the trajectory 3a of the tip when the quick return mirror 3 is operated and the lens mount surface 1AS is larger than the thickness of a general low-pass filter. Therefore, the low-pass filter 11 can be arranged without changing the positional relationship between the lesbian mount surface 1A and the tip trace 3a when the quick return mirror 3 is operated, which is designed as a silver halide film single-lens reflex camera.
[0017]
On the other hand, the thickness of the infrared light cut film 12 deposited on the cover glass 8b of the imaging device 8 is several μm to several tens μm as described above. Generally, the distance between the focal plane shutter 7 and the cover glass 8b of the imaging device 8 is 0.5 mm to 1.5 mm. Therefore, the infrared light cut filter can be arranged without changing the positional relationship between the focal plane shutter 7 and the imaging device 8 designed as a silver halide film single-lens reflex camera.
[0018]
In the digital camera according to the first embodiment described above, there is almost no need to restrict the basic performance of the silver halide film camera, and the following effects can be obtained. Since the low-pass filter is arranged away from the imaging surface of the image sensor, defects and scratches of the low-pass filter do not appear in the captured image. That is, as disclosed in Japanese Patent Application Laid-Open No. 8-313776, when a low-pass filter is arranged near the imaging surface of an image sensor, defects such as striae and scratches that are often present in the low-pass filter cause defects in the focal plane (imaging surface) of the lens. ), There is also a problem that the image appears in the image especially when the aperture of the taking lens is on the small aperture side. In the first embodiment, such a problem can be solved.
[0019]
In addition, since it is not necessary to provide an optical filter between the AF sub-mirror and the focal plane shutter 7, the following advantages are provided.
(1) Since the size of the AF sub-mirror is not restricted, the arrangement of the AF area is not restricted.
(2) It is not necessary to assume that the blade bends and comes into contact with the filter arranged immediately at the time of high-speed running of the blade of the shutter, so that the high-speed time of the shutter can be maintained.
That is, there are no various restrictions on the performance of the camera.
[0020]
-2nd Embodiment-
FIG. 3 is a central sectional view of a digital single-lens reflex camera showing a second embodiment. The components denoted by the same reference numerals as those in FIG. 1 indicate the same components as in the first embodiment. The difference is that an infrared light cut filter 12A made of a thin glass different from the cover glass is disposed immediately before the cover glass 8b of the imaging device 8.
[0021]
The thickness of the infrared light cut filter does not depend on the pixel pitch or the like of the image sensor, but only needs to satisfy the specifications of its spectral transmission characteristics alone, and can be formed of a single thin glass plate or resin plate. Usually, the absorption type infrared light cut filter is used with a thickness of about 0.3 to 0.6 mm, preferably about 0.35 to 0.5 mm. Therefore, if a small space is provided between the focal plane shutter 7 and the cover glass 8b of the imaging device 8, for example, as described above, a space of about 0.5 mm to 1.5 mm is provided. The external light absorption type infrared light cut filter 12 </ b> A can be disposed immediately before the imaging device 8.
[0022]
It is not essential that the infrared light cut filter 12A be an infrared light absorbing type infrared cut glass. That is, the infrared light cut filter may be formed by depositing an infrared light cut film on a thin glass plate having the same thickness as the infrared light absorption type filter 12A described above. In this case, the deposition surface is set on the subject side.
[0023]
In the second embodiment, it is not necessary to form an infrared light cut deposition film on the surface of the cover glass 8b of the imaging device 8.
[0024]
The digital single-lens reflex camera of the second embodiment has the same operation and effect as the digital camera of the first embodiment.
[0025]
-Third embodiment-
FIG. 4 is a central sectional view of a digital single-lens reflex camera according to the third embodiment. Similarly, the components denoted by the same reference numerals as those in FIG. 1 indicate the same components as those in the first embodiment. The difference is that an infrared light cut filter 12B is disposed in a space between the mount surface 1AS of the lens mount 1A and the quick return mirror 3, and a low-pass filter 11A is provided between the focal plane shutter 7 and the cover glass 8b of the imaging device 8. That is,
[0026]
As described above, it is often difficult to reduce the total thickness of a low-pass filter in which a plurality of birefringent plates and a phase difference plate are bonded. However, when a low-pass filter is constituted by only one birefringent plate, for example, by taking a separation direction in a direction shifted by 45 degrees from the pixel array direction of the image sensor, the thickness of the low-pass filter is 0.2 to 0.5 mm. It is about the thickness. In this case, the low-pass filter 11A can be arranged between the focal plane shutter 7 and the cover glass 8b of the imaging device 8. Further, an infrared light cut filter 12B is disposed on the subject side of the quick return mirror 3. That is, the infrared light cut filter 12B is arranged in a space between the trajectory 3a of the tip when the quick return mirror 3 is operated and the lens mount surface 1AS.
[0027]
As the infrared light cut filter 12B, an infrared light cut filter obtained by depositing an infrared light cut film on a thin glass plate or an absorption type infrared light cut glass can be used. When an infrared light absorbing type infrared cut filter is arranged between the interchangeable lens for photographing 2 and the quick return mirror 3, the transmitted light is colored blue, and the observation light flux guided from the quick return mirror 3 to the finder 6 L3 may also be colored blue. Therefore, by using an infrared light cut filter in which an infrared light cut film is deposited on a thin glass plate, the problem that a finder image observed with the naked eye looks blue can be solved.
[0028]
-Fourth embodiment-
FIG. 5 is a central sectional view of a digital single-lens reflex camera showing a fourth embodiment. Similarly, components denoted by the same reference numerals as those in FIG. 1 indicate the same components as in the first embodiment. In the fourth embodiment, a low-pass filter 11B is arranged in a space between the mount surface 1AS of the lens mount 1A of the replacement photographing lens 2 and the quick return mirror 3, and has an infrared light cut effect on the subject side surface. A deposited film is formed. In a normal infrared light absorption type infrared light cut filter, transmitted light looks blue to the naked eye, but transmitted light hardly changes in color with a deposited film. According to the digital camera of the fourth embodiment, the finder image does not look blue.
[0029]
In the digital camera according to the fourth embodiment described above, the main mechanism of the silver halide film-lens reflex camera such as the focal plane shutter and the quick return mirror is hardly changed, and the basic performance of the camera is hardly restricted. Not even. Further, since the low-pass filter is arranged away from the imaging surface of the image sensor, defects and scratches of the low-pass filter do not appear in the captured image, as described in the first embodiment.
[0030]
In the above, the low-pass filter and the infrared light cut filter have been described. However, the present invention can be applied to a digital camera using two different types of filters. In addition, the infrared cut filter is not limited to one using the infrared cut glass or the one using the vapor-deposited film. Alternatively, an infrared cut filter using both of them may be used.
[0031]
【The invention's effect】
As described above, the present invention has the following effects.
Since the first optical filter having a large thickness is arranged in the space between the lens mounting surface and the quick return mirror, and the second optical filter having a small thickness is arranged in the space between the shutter mechanism and the image pickup device, the quick return is achieved. Two types of optical filters, such as a low-pass filter and an infrared cut filter, can be arranged in a digital single-lens reflex camera without making a mirror and a shutter mechanism different from a silver halide film single-lens reflex camera.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of a digital camera according to a first embodiment of the present invention.
FIG. 2 is a schematic sectional view of the digital camera according to the first embodiment of the present invention.
FIG. 3 is a schematic sectional view of a digital camera according to a second embodiment of the present invention.
FIG. 4 is a schematic sectional view of a digital camera according to a third embodiment of the present invention.
FIG. 5 is a schematic sectional view of a digital camera according to a fourth embodiment of the present invention.
[Explanation of symbols]
1: Camera body 1A: Lens mount 1AS: Lens mounting surface 2: Interchangeable lens for shooting 3: Quick return mirror 4: Sub mirror 5: Auto focus module 6: Viewfinder section 7: Focal plane shutter 8: Image pickup device 8a: Image pickup device 8b : Cover glass 11, 11A, 11B: low-pass filter 12, 12A, 12B: infrared light cut filter

Claims (10)

An image sensor that forms an image of a subject luminous flux incident via an imaging interchangeable lens mounted on a lens mounting surface of a lens mount;
Provided between the lens mounting surface and the image sensor, at the time of non-photographing, at least a part of the subject luminous flux that has passed through the interchangeable lens for photography is guided to an observation optical system. A quick return mirror that allows the light to enter the image sensor,
A shutter mechanism provided between the quick return mirror and the image sensor;
A first optical filter provided between the lens mounting surface and the quick return mirror and having a first thickness;
A digital single-lens reflex camera, comprising: a second optical filter provided between the shutter mechanism and the image sensor, the second optical filter being thinner than the first optical filter. The digital single-lens reflex camera according to claim 1,
The first optical filter is a low-pass filter;
A digital single-lens reflex camera, wherein the second optical filter is an infrared light cut filter. The digital single-lens reflex camera according to claim 2,
The digital single-lens reflex camera, wherein the infrared light cut filter is an infrared light cut deposited film deposited on a cover glass on a surface of the imaging device. The digital single-lens reflex camera according to claim 2,
The digital single-lens reflex camera, wherein the infrared light cut filter is a thin glass sheet disposed just before a cover glass of the imaging device and having an infrared light cut deposition film deposited on a subject side. The digital single-lens reflex camera according to claim 2,
The digital single-lens reflex camera, wherein the infrared light cut filter is an infrared light cut glass that is attached to a cover glass of the imaging device and absorbs infrared light. The digital single-lens reflex camera according to claim 1,
The digital single-lens reflex camera, wherein the shutter mechanism is a focal plane shutter. An image sensor that forms an image of a subject luminous flux incident via an imaging interchangeable lens mounted on a lens mounting surface of a lens mount;
Provided between the lens mounting surface and the image sensor, at the time of non-photographing, at least a part of the subject luminous flux that has passed through the interchangeable lens for photography is guided to an observation optical system. A quick return mirror that allows the light to enter the image sensor,
A shutter mechanism provided between the quick return mirror and the image sensor;
An infrared light cut filter provided between the lens mounting surface and the quick return mirror,
A digital single-lens reflex camera, comprising: a low-pass filter provided between the shutter mechanism and the image sensor, the low-pass filter having a single birefringent plate. The digital single-lens reflex camera according to claim 7,
The digital single-lens reflex camera, wherein the shutter mechanism is a focal plane shutter. The digital single-lens reflex camera according to claim 7 or 8,
A digital single-lens reflex camera, wherein the infrared light cut filter is a thin glass plate on which an infrared light cut deposition film is deposited on a subject side. The digital single-lens reflex camera according to claim 7 or 8,
The digital single-lens reflex camera, wherein the infrared light cut filter is an infrared light cut glass that absorbs infrared light.

Images