JPH04355571A - Electronic camera - Google Patents

Abstract

PURPOSE:To make the entire lens system small and to keep excellent picture quality by arranging a low pass filter in an optical path between a quick return mirror in a camera main body and a shutter means. CONSTITUTION:A low pass filter 7 is arranged between a quick return mirror 50 and a shutter means 4. Moreover, an image forming face of an image pickup lens 1 is prolonged more than the shutter means 4 through the arrangement of the filter 7 and the image pickup means 6 is arranged to the extended position. That is, the filter 7 is arranged behind the quick return mirror 50 and a sub-mirror 51 and this side from the shutter means. In this case, a focal position 3 of the image pickup lens 1 goes backward by the filter 7 arranged in this way and an optical distance from the surface of an electronic camera back 101 of the image pickup element 6 till the image pickup face of the image pickup element 6 is much extended.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic camera, and more particularly to an electronic camera suitable for photographing images using a solid-state imaging device such as a CCD as an imaging means.

0002

2. Description of the Related Art Various so-called electronic cameras using solid-state imaging devices such as CCDs as imaging means have been proposed. In the form of an electronic camera, an adapter is attached to the camera body for 35mm silver halide film, and a solid-state image sensor is placed at the original imaging position, or at an imaging position formed by a secondary optical system installed behind the imaging position. There are two types of electronic cameras: one is an electronic camera configured as a conventional camera, and the other is an electronic camera that uses a dedicated camera body that has been designed for an imaging system suitable for a solid-state image sensor.

0003

Among these types of electronic cameras, the former type is mainly constructed by modifying the back cover of a so-called single-lens reflex camera body. At this time, the image sensor is placed either directly in the original imaging plane of the back cover, or in a secondary imaging position created by a secondary imaging system placed behind the imaging position. There is an indirect method. In the former direct method, it is necessary to place the image sensor immediately behind the shutter means.

[0004] However, since there is generally only a space of about 1 to 2 mm from the shutter to the imaging plane (focal position), it is difficult to arrange the optical low-pass filter and infrared cutoff filter that are required when using an image sensor. becomes. It also becomes difficult to appropriately configure the package of the image sensor.

FIG. 4 is a schematic diagram of the main parts of the direct method. In the figure, an image sensor 6 is directly placed at an imaging position 3 formed by the photographing lens 1. In this method, as described above, the optical distance from the surface of the package 61 to the imaging surface of the image sensor 6 is strictly limited, and it is very difficult to arrange a low-pass filter or the like.

On the other hand, in the indirect method using a secondary imaging system, 2
There are problems in that image quality deteriorates due to aberrations in the secondary imaging system, and the entire optical system becomes larger. Furthermore, there is a problem in that the secondary imaging system obstructs the use of the finder, which requires some kind of countermeasure.

FIG. 5 is a schematic diagram of the main parts of the indirect method. A condenser lens 81 (this means that the exit pupil of the photographic lens 1 is located at the image forming position 3 of the photographic lens 1 at the secondary imaging lens 82 described later)
(by projecting onto the pupil of the camera, most of the light rays passing through the photographing lens 1 are incident on the secondary imaging lens 82), and the secondary imaging lens 82 forms an image on the image sensor 6.

In this case, the low-pass filter 7 and the like can be easily placed in front of the image sensor 6 or between the condenser lens 81 and the secondary imaging lens 82.

However, there are problems in that the entire optical system becomes large and the image quality deteriorates due to aberrations of the secondary imaging lens. (In the following explanation, the term "electronic camera back" refers to the component used to construct an electronic camera in place of the back cover of the original 35mm silver halide film camera body.)
That's what it means. ) The present invention uses an electronic camera back for a 35mm film camera body, allows the image sensor to be easily positioned on the image forming plane of the camera body even though it is a direct method, and reduces the size of the entire lens system. The purpose of the present invention is to provide an electronic camera that can improve image quality and maintain good image quality.

0010

[Means for Solving the Problems] The electronic camera of the present invention includes:
A camera body for 35 mm film having a lens mount for an interchangeable lens is provided with an image sensor for recording image information near an image forming position in the camera body, and a quick return mirror and a shutter means in the camera body. The feature is that a low-pass filter is placed in the optical path between the two.

In addition, the present invention provides a camera body for 35 mm film having a lens mount for an interchangeable lens.
An image sensor for recording image information is provided in the vicinity of the image forming position in the camera body, and an optical path between the quick return mirror and the shutter means in the camera body and between the shutter means and the image sensor is provided. It is characterized by a low-pass filter placed in the optical path.

0012

Embodiments FIGS. 1 to 3 are sectional views of main parts of embodiments 1 to 3 of the present invention. 1 to 3 show an example in which an electronic camera back is attached to a 35 mm film camera body having a lens mount for an interchangeable lens.

In FIG. 1, reference numeral 1 denotes a photographic lens, which is detachably mounted on a lens mount (not shown) on the camera body. 50 is a quick return mirror (QRM) that reflects the light beam from the photographing lens 1 to the finder system. Reference numeral 53 denotes a focusing plate, on which a subject image formed by the photographing lens 1 is formed. Optical systems such as a pentaprism and an eyepiece after the focusing plate 53 are omitted because they are well known.

Reference numeral 51 denotes a submirror, which guides the light beam that has passed through a portion of the quick return mirror 50 to an automatic focus detection means 52. 4 is a shutter means attached to the camera body. Reference numeral 101 denotes an electronic camera back, which has an imaging means (imaging element, CCD) 6. 7 is a low-pass filter, which is arranged between the quick return mirror 50 and the shutter means 4. Note that the photographing means 6 is arranged so that the imaging surface of the photographing lens 1 extends from the shutter means 4 due to the arrangement of the low-pass filter 7, and is disposed at this extended position.

That is, in this embodiment, the low-pass filter 7
is arranged behind the quick return mirror 50 and the sub-mirror 51 and in front of the shutter means 4. At this time, the photographing lens 1 is
The focal position 3 moves backward, and the optical distance from the surface of the electronic camera back 101 of the image sensor 6 to the imaging surface of the image sensor 6 becomes larger than in FIG.

Generally, the image sensor 6 is often smaller than the original film. In this case, the low-pass filter 7 can be made small because it only needs to pass enough light flux necessary for the image sensor, but if it is necessary to measure the light reflected from the image sensor 6 for photometry and light control, these filters can be used. The size may be determined so that the necessary luminous flux passes through.

If the low-pass filter 7 is large due to the above-mentioned requirements for photometry and light control, it does not have to be symmetrical with respect to the optical axis 2. Also, regarding the image sensor 6, the image sensor 6 may be placed somewhat lower than the original optical axis 2 in order to avoid mechanical interference between the low pass filter 7 and the quick return mirror 50.

Similar to a single-lens reflex camera for 35 mm film, it is preferable that the finder of an electronic camera has a field frame, field mask, etc. that matches the image pickup device 6.

Furthermore, the low-pass filter 7 may be made removable if the camera body needs to be shared for shooting 35 mm film. In this case, it is preferable that the "electronic camera back" side has a cap for protecting the surface of the image sensor 6 and a storage mechanism for the low-pass filter 7.

In this case, the amount of retraction of the imaging plane 3 by the low-pass filter 7 can be used to make the focal point 3 approximately at the surface of the image sensor 6 or in front of it when the low-pass filter 7 is removed. By removing the low-pass filter 7, "Electronic camera back 101"
It is also possible to shoot 35mm film without having to replace the camera back with a regular camera back.

In these cases, in order to harmonize multiple modes of use and/or prevent malfunction, the low-pass filter 7 or/and the normal back cover or/and the back cover attached to the image sensor 6 ("electronic camera back") may be used. It is preferable to provide means for detecting attachment/detachment and means for communication between these.

Embodiment 2 shown in FIG. 2 is a modification of Embodiment 1 shown in FIG. In this embodiment, the low-pass filter 7 is divided into two parts, and one part of the low-pass filter 71 is placed in front of the shutter means 4, and the other low-pass filter 72 is placed behind the shutter means 4. Originally, a low-pass filter consists of multiple optical members (such as a crystal plate). For this reason, in this embodiment, the infrared cutoff filter 61 is combined with the low-pass filter (and the order if necessary).
Appropriate ones are divided and arranged before and after the shutter means 4.

In this embodiment, the quick return mirror 50
This is suitable when the arrangement as shown in FIG. 1 is not possible due to mechanical interference between the filter and the low-pass filter 7.

Embodiment 3 shown in FIG. 3 is a modification of Embodiment 2 shown in FIG. In this embodiment, the low-pass filter 72 is arranged behind the cover glass 61 of the image sensor 6.

This embodiment is particularly effective when only members with poor moisture resistance, such as certain types of infrared cutoff filters, are placed at the rear (if they are made integrally, there is usually a problem with their environmental resistance). Some members are sandwiched between other members). In this embodiment, the low-pass filter 72 may be protected with a sealing material 62 if necessary.

In this embodiment, a member with good environmental resistance may be placed at the rear and used in place of the cover glass of the image sensor 6. (In the case where the cover glass 61 in FIG. 3 is not provided) In each of the above embodiments, the portions after the image pickup device 6 can be configured in the same manner as a generally disclosed electronic camera, and therefore are omitted in each embodiment.

[0027]

Effects of the Invention According to the present invention, by configuring each element as described above, an electronic camera back can be used for a 35 mm film camera body, and an image sensor can be connected to the camera body even though it is a direct method. It is possible to achieve an electronic camera that can be easily positioned on the imaging plane, the entire lens system can be made smaller, and good image quality can be maintained.

Further, according to the present invention, an electronic camera can be easily constructed using the main parts of a camera body for 35 mm film, and if necessary, it can be designed for dual use. There is.

Furthermore, according to the present invention, by arranging a low-pass filter and/or an infrared cutoff filter behind (and below) the so-called quick return mirror and in front of the shutter, the camera body for 35 mm film can be used or used for both purposes. It has the advantage of being able to rationally manufacture electronic cameras.

[Brief explanation of the drawing]

[Fig. 1] Cross-sectional view of main parts of Example 1 of the present invention

[Figure 2]
Embodiment 2 of the present invention Main part sectional view

[Fig. 3] Cross-sectional view of main parts of Embodiment 3 of the present invention

[Figure 4] Cross-sectional view of main parts of a conventional electronic camera

[Figure 5] Cross-sectional view of main parts of a conventional electronic camera

[Explanation of symbols]

1 Photographing lens 2 Optical axis 3 Imaging surface 4 Shutter means 6 Imaging elements 7, 71, 72 Low-pass filter 50 Quick return mirror 51 Sub-mirror 52 Automatic focus detection device 53 Focus plate 61 Infrared cut filter

Claims (3)

[Claims] Claim 1: A camera body for 35 mm film having a lens mount for an interchangeable lens is provided with an image sensor for recording image information near the image forming position in the camera body, and a quick return device in the camera body. An electronic camera characterized in that a low-pass filter is arranged in an optical path between a mirror and a shutter means. 2. A camera body for 35 mm film having a lens mount for an interchangeable lens is provided with an image sensor for recording image information near the image forming position in the camera body, and a quick return device in the camera body. An electronic camera characterized in that a low-pass filter is arranged in an optical path between a mirror and a shutter means and in an optical path between the shutter means and the image pickup device. 3. An infrared absorption filter is disposed in an optical path between the quick return mirror and the shutter means and/or in an optical path between the shutter means and the image pickup device. Or 2 electronic cameras.