JPS5925209B2 - Flange back conversion adapter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention is an industry that uses interchangeable lenses such as still cameras with long flange backs and short flange backs.

This product relates to a flange back conversion adapter that can be used for TV cameras, etc. In general, interchangeable lenses and cameras each have a specific flange focal length, so it is not possible to use interchangeable lenses and cameras with different flange focal lengths in combination, but the flange focal length of the interchangeable lens is L.

, when the flange back of the camera is R (however, L
0>R), and the total length Q is expressed as Q=(L0-R).If a flange bag conversion adapter is interposed between the two, the two can be used in combination, increasing the versatility of the interchangeable lens. improves. However, for example, industrial television cameras (hereinafter referred to as ITV cameras) or general small television cameras are generally equipped with a dedicated photographing optical system that includes an infrared cut filter, ND filter, polarizing filter, or optical low-pass filter. Therefore, it is clear that sufficient performance cannot be obtained even if the above-mentioned flange back conversion adapter is used instead of the dedicated photographic optical system and a commercially available interchangeable lens such as a still camera is used. However, there remains a problem with the versatility of commercially available interchangeable lenses.

Along with this, in ITV cameras and the like, it is common to add special filters to the dedicated photographic optical system depending on the purpose of shooting, but such special filters are not available for commercially available interchangeable lenses. In many cases, the lens is not equipped with a special filter, and generally cannot be attached to the filter mount section of an interchangeable lens, so commercially available interchangeable lenses cannot be used even in this type of photography where a special filter is added.

This also applies to some ITV cameras where the filter section is left in the camera and only the imaging system is replaced, rather than the entire dedicated photographic optical system. When shooting with special filters, commercially available interchangeable lenses cannot be used for the same reason as above. Therefore, this invention makes it possible to use interchangeable lenses for still cameras, etc., which are generally widely available on the market, for cameras that require a dedicated photographic optical system as described above.
Moreover, the purpose is to provide a flange back conversion adapter that can simultaneously overcome the difference in flange back between an interchangeable lens and a camera. A separable holding member is provided so that the total length of the adapter when attached to the adapter body matches the difference between the flange back of the interchangeable lens and the flange back of the camera, and the holding member and the adapter body are The feature is that a spacer having a thickness matching the increase in the geometrical optical path length due to the insertion of the filter can be attached between the filters.

The present invention will be described below based on illustrated embodiments.

First, FIG. 1 shows a first embodiment of the present invention, where T represents an interchangeable lens such as a still camera, P represents an imaging plane of a camera (not shown), and A represents an adapter according to the present invention.

The interchangeable lens T has a flange back L as shown in FIG.
. , and the flange back of the other camera is set to R. However, here, the flange back of the interchangeable lens T is the distance from the contact surface of the interchangeable lens T to the imaging plane P.
The flange back of the camera refers to the distance from the contact surface of the camera for the interchangeable lens T to the imaging plane P. Adapter A includes a main mount 1 that can be attached to an interchangeable lens T and a screw 1 to this main mount 1.
It consists of an adapter body having an intermediate tube 2 attached by a, a slave mount 3 that can be attached to a camera, and a holding member having a screw ring 4 for pressing the slave mount 3 against the intermediate tube 2.

That is, the intermediate cylinder 2 has a screw 2a on its outer periphery that engages with a screw 4a formed on the inner periphery of the screw ring 4, and has an annular protrusion 2b on its inner periphery that can come into contact with the slave mount 3. When the screw ring 4 is fitted into the intermediate tube 2, the slave mount 3 is pressed against the protrusion 2b by the screw ring 4, thereby being fixed to the intermediate tube 2. Incidentally, in order to satisfy the required performance as will be described later, F is the same filter included in the dedicated photographing optical system of the camera, and is fixed to the protrusion 2b by a screw washer 5. On the other hand, 6 is an annular spacer made of metal or plastic, for example, and is inserted between the slave mount 3 and the protrusion 2b of the intermediate cylinder 2, and fixes the slave mount 3 to the intermediate cylinder 2 as described above. At this time, the position at which the slave mount 3 is fixed is restricted in the axial direction of the adapter A.

Now, the thickness D of this spacer 6 is due to the insertion of the filter 1F. It is equal to the increase in the geometrical optical path length of the photographing beam along the optical axis Δ2, that is, Δl−d(1−1) N (where D and N are the thickness and refractive index of the filter F).

On the other hand, the total length of the adapter A when the slave mount 3 is brought into direct contact with the protrusion 2b of the intermediate cylinder 2 without intervening the spacer 6 is expressed as (LO-R). Then, if the spacer 6 is interposed as described above,
The total length Q of adapter A is Q-(LO-R)+D (LO-R)+d(1-1) (2)0N.

In the above configuration, assume that the interchangeable lens T is attached to the camera via the adapter A.

Then, it enters the interchangeable lens T and forms an image plane P along the optical axis.
The geometrical optical path length of the photographing light beam directed toward is longer than in the case without the filter F by Δ2 expressed by the above equation (1). Therefore, if there were no spacer 6, the photographing light beam would form an image behind the imaging plane P, and as a result, even if this interchangeable lens T was used, a good pit image would not be obtained. However, when the spacer 6 is interposed as shown in FIG.
Since the total length of the adapter A is expressed by the above equation (2), the photographing light beam passing through the filter 1F is precisely focused on the imaging plane P. Therefore, for example, if the above-mentioned camera is an ITV camera that requires a dedicated photographing optical system including an infrared cut filter 1, an adapter A to which the same filter 1F as the infrared cut filter 1 is attached may be used. Therefore, with the interchangeable lens T, it is possible to obtain a good pit image on the imaging plane P with the same performance as using a dedicated photographing optical system.

The same applies to the case of photographing with a special filter added.If the special filter is attached to the adapter A, the interchangeable lens T can be used. In addition, in this adapter A, the screw washer 15 of the filter 1F can be removed from the protrusion 2b of the intermediate cylinder 2,
Furthermore, since the spacer 6 can also be removed, this adapter A can be used in combination with an interchangeable lens T and a camera that does not require a filter 1 at all or does not require the addition of a filter 1.

Furthermore, in order to be able to use the interchangeable lens T with a camera that requires another type of filter (for example, an ND filter), the filter F can be replaced with that filter, and the spacer 6 can be used for that filter. Above (1)
It is sufficient to select a spacer having a thickness D that matches Δl expressed by the formula. Adapter A thus allows interchangeable lens T to be used with a variety of cameras. Next, FIG. 3 shows a second embodiment of the present invention, in which the filter 1F is attached to the protrusion 2b of the intermediate cylinder 2 by a spacer 16 instead of using a screw washer 1.

That is, since the spacer 16 in this embodiment also has the role of fixing the filter F, as shown in FIG. notches 16b,
The overall shape is comb-shaped, and the comb-shaped portions are slightly bent to provide elasticity.

The thickness of the spacer 16 is expressed by D (=Δl) above, considering the thickness of the plate itself as the thickness of the spacer 16 without considering the amount of bending. With such a configuration, before fixing the slave mount 3 to the intermediate cylinder 2,
First, put the filter 1F, then the spacer 16 into the intermediate cylinder 2.
After that, the screw ring 4 is fitted into the intermediate cylinder 2 and tightened.

Then, since the spacer 16 is sandwiched and pressed between the filter 1F and the subordinate mount 3, the comb-like portions described above are elastically deformed, and finally become similar to a plate material having a thickness D. However, the restoring force of the comb-shaped portion acts on the filter 1F at that time, and the filter 1F is firmly fixed to the protrusion 2b of the intermediate cylinder 2. As described above, in this embodiment, the spacer 16 is formed into a comb-like shape, but with this configuration, for example, the hole 2c of the protrusion 2b for holding the filter 1F is larger than the thickness of the filter 1F. Even if the depth is too deep and a gap is created between the filter 1F and the spacer, the filter 1F can be held down by the comb-shaped portion of the spacer 16, and therefore there is an advantage that the filter 1F can be securely fixed.

However, as long as, for example, the thickness of the filter 1F and the depth of the hole 2c are made equal, it is also possible to use the spacer 6 in the first embodiment as the spacer. Furthermore, FIG. 5 shows a third embodiment of the present invention, in which the spacer 26 and the filter 1F are integrally formed so that both can be replaced at the same time.

That is, 21 is a holding ring for attaching the filter F to the spacer 26, and has a hole 21a.

After the filter F is inserted into the hole 21a, it is sandwiched between the spacers 26 as shown in FIG. 6, and when the spacer 26 is tightened to the holding ring 21 with the screws 22, the filter F becomes integral with the spacer 26. Note that in the intermediate cylinder 20 of this embodiment, the part for holding the filter 1F is not necessary, so the part corresponding to the part for holding the inner filter 1F of the protruding part 2b in the above two embodiments is is removed, and the spacer 26 holding the filter 1F at the contact surface 20c against the slave mount 3 is removed.
It is becoming more and more popular. Further, in this embodiment, the intermediate tube 20 also serves as the main mount 1 in the above embodiment, and constitutes an adapter body, and the front end (left end in the figure) of the intermediate tube 20 has a mount part for the interchangeable lens T and a fitting part. A matching mount is formed. Note that forming the main mount 1 and the intermediate cylinder 2 integrally in this way is the first
This is also possible in the second embodiment. 7 shows an embodiment that is a further modification of the embodiment shown in FIG. 5. In this embodiment, the screw ring 4 for tightening the slave mount 3 is omitted, and instead, intermediate cylinder 2
A screw 30a that fits with a screw 20a formed on the outer periphery of
is formed so that the slave mount 30 is directly fixed to the intermediate cylinder 20, and this slave mount 30 constitutes a holding member.

Further, 31 further securely attaches the follower mount 30 to the intermediate cylinder 20.
After fitting the slave mount 30 to the intermediate cylinder 20 as shown in the figure, screw it in and tighten it to the outer periphery of the intermediate cylinder 20 using a screw for fixing the secondary mount 30 to the intermediate cylinder 20. In the embodiment shown in FIG. 5 and this embodiment, the total length Q of the adapter A is defined as the distance from the contact surface of the intermediate tube 20 against the interchangeable lens T to the contact surface of the slave mounts 3, 30 against the camera. Although the embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above.

For example, the above-mentioned filter 1F may not only have a filter effect on its entirety, but also may be one in which one or both sides of a substrate such as glass is treated to provide a filter effect. The whole including the filter will be referred to as one filter, and its overall thickness and refractive index will be expressed by D and N, respectively.
Furthermore, in the above embodiments, only one filter is used, but it is also possible to attach a plurality of filters to the adapter A, in which case (2) ) formula is Q-(LO-R)+ΣD
It is expressed as i(1-[MejNi (where Di and Ni are the thickness and refractive index of the i-th filter).

Furthermore, although omitted in the explanation of the above embodiment, it is possible to make the mounting types of the attachment parts of the main mat 1 and the intermediate tube 20 for the interchangeable lens T and the attachment parts of the slave mounts 3 and 30 for the camera different from each other. , interchangeable lenses and cameras that employ different mount formats can be used together, further improving the versatility of the interchangeable lens T.

Also, if the mounting types of the camera and interchangeable lens mounting parts are the same but their diameters are different, adjust the diameters of the main mount opening and intermediate tube 20 mounting part, and the secondary mounts 3 and 30 accordingly. Just set it. For example, in the embodiment shown in FIGS. 2 and 3, the attachment part of the main mount 1 is a bayonet mount, and the attachment part of the secondary mount 3 is a screw mount, and in the embodiment shown in FIGS. 5 and 7, Main mount 1
The mounting portion of the intermediate cylinder 20 and the mounting portions of the mounts 3 and 30 are both screw mounts, and the former has a larger diameter than the latter. In each of the embodiments shown in FIGS. 1, 3, 5, and 7, the rotational position of the filter F can be set arbitrarily when installing the filter F, so that it can be used, for example, in a T-camera. For filters such as optical low-pass filters whose cutoff frequency changes depending on the rotational position at the time of installation, the cutoff frequency can be set arbitrarily.

As explained above, the flange bag conversion adapter of the present invention has a normal (LO-R) overall length, but
By interposing the spacer, the total length can be increased by the increase in the mechanical optical path length of the photographing light beam due to the insertion of the filter, which reduces the flange back of the interchangeable lens when the filter is attached. Since the change can be compensated for, interchangeable lenses such as commercially available still cameras can be used with cameras that require a dedicated photographic optical system that includes the same filter, increasing the versatility of interchangeable lenses. It has the effect of improving

Furthermore, even in the case of photography in which a special filter is added to such a camera, a commercially available interchangeable lens can be used, and in this sense, the versatility of the interchangeable lens is also useful.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a first embodiment of the invention, FIG. 2 is a front view showing a flange back of an interchangeable lens T, FIG. 3 is a sectional view showing a second embodiment of the invention, and FIG. is a perspective view of the spacer 16 and the filter 1F, FIG. 5 is a sectional view showing the third embodiment, FIG. 6 is a perspective view showing the mounting structure of the filter 1F, and FIG. 7 is a still another embodiment. FIG. T...Interchangeable lens, P...Camera imaging plane, 1...Main mount, 2, 20...
・Intermediate cylinder, 3, 30...Sub mount, 4...
...Screw ring, 5...Screw washer 1 2
1... Holding ring, F... Filter 3, 4, 30... Holding member.

Claims (1)

[Claims] 1. A flange back exchange adapter for making it possible to use an interchangeable lens with a long flange back on a camera with a short flange back, the adapter comprising a filter holder to which at least one filter can be attached;
A holding member that is separable from the adapter body is provided, and the total length of this adapter when this holding member is attached to the adapter body is (L_0-R), and the thickness is determined between this holding member and the adapter body. △l is △l=Σdi
A mount conversion adapter characterized by interposing a spacer represented by (1-1/Ni). However, L_0, R: flange back di of the photographic lens and camera, Ni: i attached to the filter holding part
Thickness and refractive index of the second filter.