JPS6127516A - Rear conversion lens - Google Patents

Abstract

PURPOSE:To make the constitution of a rear conversion lens simple and small in size by splitting a luminous flux from an interchangeable lens of a lens interchangeable type camera, by an optical splitter provided in the rear of an image forming optical system, and providing a photodetector at a conjugate position to the surface of a film. CONSTITUTION:A luminous flux which has beem made incident on an interchangeable lens 3 is condensed by the interchangeable lens 3, a part of said luminous flux is made to transmit through an optical splitting prism 12 through an image forming optical system 11 of a rear conversion lens 1, and an image is formed on a film surface 2a of a camera body 2. Also, a part of the luminous flux which has passed through the image forming optical system 11 of the rear conversion lens 1 is reflected by an optical splitting surface 12a of the optical splitting prism 12, and thereafter, emitted from the splitting prism 12, and an image is formed on a photodetector 13 provided at a conjugate position to the film surface 2a.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a rear conversion lens that can be used as a focusing device for an interchangeable lens camera.

Conventional art A relay optical system that can be installed between the camera body and the interchangeable lens of an interchangeable lens camera and that splits the luminous flux and guides it to the light receiving element is known, for example, from Japanese Patent Application Laid-Open No. 50-11322.
No. 8 is known, but this is composed of an imaging optical system and a light splitter inserted between the imaging optical system, so that the light receiving element and the film surface are In order to maintain a conjugate relationship between the two, it is necessary to provide an auxiliary lens in front of the light-receiving element, which complicates the entire optical system and limits the detection accuracy of the luminous flux due to manufacturing errors and assembly errors of the auxiliary lens. It will be done. In addition, when placing a light splitter between the imaging optical systems, the light splitter will be split in areas where the light beam is not sufficiently converged, so the light splitter may not be large enough in this area because the diameter of the light beam is large. This increases the size of the entire relay optical system. Furthermore, focusing operations are now performed by moving the interchangeable lens relative to the relay optical system and camera body, and when the interchangeable lens is large and heavy, such as a telephoto lens, focusing operations require a great deal of strength. If this focusing operation is performed by a motor, an excessive load will be applied to the motor, which may make automatic focusing impossible.Also, if a motor with sufficient torque is used, automatic focusing will be impossible. The entire focusing device becomes large.

Purpose In view of the above points, an object of the present invention is to provide a rear conversion lens with a simple and compact configuration that can be used as a focusing device without using a specially configured camera body or an interchangeable lens. .

Overview This purpose is to provide a rear conversion lens that can be installed between the camera body and the interchangeable lens of an interchangeable lens camera, and to provide an imaging optical system that focuses the light beam from the interchangeable lens onto a film surface within the camera body. It includes a light splitter disposed behind the imaging optical system, and a light receiving element disposed at a position conjugate with the film surface on the optical path split by the light splitter. This is solved by a rear conversion lens featuring the following.

Furthermore, this object has been solved by a rear conversion lens characterized in that a focusing operation is performed by moving at least a portion of an imaging optical system and a light splitter in the optical axis direction. Ru.

EXAMPLES The present invention will be explained below with reference to the examples shown in the drawings. FIG. 1 shows the basic configuration of a rear conversion lens according to the present invention, and l indicates a camera body 2 and an interchangeable lens 3.
The rear conversion lens is installed between the
An imaging optical system 11 that forms an image of the light beam from the interchangeable lens 3 onto a film surface 2a in the camera body 2;
A light splitting prism 12 arranged behind the light splitting prism 12 and a light receiving element 13 arranged at a position conjugate with the film surface 2a of the camera body 2 on the optical path split by the light splitting surface 12a of the light splitting prism 12. Contains.

According to such a configuration, the light beam incident on the interchangeable lens 3° is condensed by the interchangeable lens 3, and then a part of it passes through the imaging optical system 11 of the rear conversion lens 1 and passes through the light splitting prism 12. through the film surface 2 of the camera body 2
A part of the light beam that is imaged on a and passes through the imaging optical system 11 of the rear conversion lens 1 is transferred to the light splitting prism 12.
After being reflected by the light splitting surface 12a, the light exits the light splitting prism 12 and forms an image on the light receiving element 13. Here, since the light splitting prism 12 is disposed behind the imaging optical system 11, the light beam that has passed through the light splitting prism 12 is then filtered by a lens or the like before reaching the film surface 2a of the camera body 2. The state of the light beam cannot be changed and the light splitting prism 1
The light beam reflected by the light splitting surface 12a of No. 2 is only reflected before reaching the light receiving element 13 and the state of the light beam cannot be changed in the same way. An imaging state equivalent to the imaging state on the film surface 2a is obtained above, and the light splitting prism 12
Since there is no need to arrange an auxiliary lens in the optical path from the light splitting surface 12a to the light receiving element 13, the optical system becomes complicated and the light beam detection accuracy decreases due to manufacturing error of the auxiliary lens 1 assembly error. Never. Furthermore, since the light splitting prism 12 is disposed behind the imaging optical system 11, the light beam at the light splitting surface 12a is sufficiently converged and the diameter of the light beam is small. 1
2 can be configured to be compact.

In general, when a rear conversion lens is attached between the camera body and an interchangeable lens, if the imaging magnification of the rear conversion lens is MR and the F value of the interchangeable lens is A, then the F of the light flux emitted from the rear conversion lens is The value A' is given by A' MR - A, and since MR > 1, the F value A' will be larger than A, which may reduce the luminous flux detection accuracy, but in this case, the light splitting prism By inserting an auxiliary lens into the optical path between the light receiving element 12 and the light receiving element 13, the light receiving element 1
By converting the F value of the light beam incident on the lens 3, it is possible to compensate for the decrease in light beam detection accuracy, and furthermore, the auxiliary lens may be switched in accordance with the F value of the interchangeable lens.

Furthermore, when performing a focusing operation in such a configuration, the objective lens 3 may be moved as in the conventional method as shown in FIG. Since this is disadvantageous, it is preferable to move only the imaging optical system 11 of the 'J7 conversion lens 1 in the optical axis direction as shown in FIG. 3 or as shown in FIG. The entire optical system of the rear conversion lens 1, that is, the imaging optical system 11 and the light splitting prism 12, are moved integrally in the optical axis direction, and as shown in FIG. Optical system 11
A focusing operation can be performed by moving a part of the lens, for example, the front group 11a or the rear group 11b (in the case of FIG. 5, the front group 11a) in the optical axis direction. In the case of FIG. 4, since the distance from the light splitting prism 12 to the film surface 2a changes, the light is received from the light splitting prism 12 so that the light receiving element 13 and the film surface 2a are always in a conjugate relationship. The air-equivalent optical path length up to the element 13 is always set to the prism 12.
4 to the film surface 2a. Therefore, the light receiving element 13 is connected to the imaging optical system 110.
It is disposed on the optical axis parallel to the optical axis so as not to move relative to the film surface 2a of the camera body 2 when the light splitting prism 12 moves. Note that the imaging optical system 11 in the focusing operation described above. The movement of the light splitting prism 12 can be performed manually or automatically by controlling a drive mechanism such as a shimo motor using a signal corresponding to the in-focus state detected by the light receiving element 13.

Specific examples according to the present invention will be shown below, and the paraxial quantities of the interchangeable lens as a reference lens to be mounted in each example are as follows.

Focal length: 51.84 Rear focal length: 37.856 F number: 1.8 FIG. 6 shows a specific embodiment of the rear conversion lens according to the present invention, in which the imaging optical system 11 is integrated in the optical axis direction. Focusing operation is performed by moving the lens, and each numerical value is as follows. “MR=2.O r+ =68.9975 d, -1,0257, n, =1.80400,
v, =46.6r2=17.1343 d2=0.7774 r,3=25.0837 d3 =4.6653, n3 =1.59270
, vs =35.3r4=-31,4737 d4=3.7174 r,=-24,6619 d, =2.7064, n, =1.804
00, v, =46.6re =741.65
09 d, = 3.2946 rγ = 106.4253 d7 = 8.6307, n, = 1.50137
, Schiff = 56.4 r8 = -18,3086 d8 =, 0.1910 r9 = -51,5728 d, = 1.1764, no = 1.815
54,,v,=44.5r1o=121.6
660 dlo-variable r, , = (X) d, , ==11.5 , n, , =1.51
633, I/,, = 64.2 r12 = ω do = 0.2434 ~ 6.1264 d + o = 7.1 ~ 1.127 MR is the imaging magnification % of the rear conversion lens
r, l r2 + r3... The radius of curvature of each surface of the barrier conversion lens, do is the air distance PIL from the rearmost surface of the interchangeable lens to the first surface of the rear conversion lens, (L, d2. d3... is Thickness and air spacing of each lens of rear conversion lens, nl+
n8. ... is the refractive index of each lens, and C1. C8. ...
is the Atsube number of each lens.

According to this embodiment, when the interchangeable lens is attached, a focusing range from infinity to o, 75 m-1 can be obtained.

FIG. 7 shows a second embodiment of the present invention, in which focusing operation is performed by moving only the front group 1'la of the imaging optical system 11 in the optical axis direction, and each numerical value is The following is the general rule.

Mn=2.0 r,=62.2257 d,=1.1704, n,=1.80400
, shi, =46.6r2=17.9717 d2' =LO301 r,=25.3432 d3=4.5163, n3 =1.5927
0, v3 = 35.3r, = -29,5200 d4 = 2.3472 rs = -26,1037 ds = 1.5376, n5 = 1.804
00, v, =46.6re =-702,1
960 d, = variable r7 = 327.8450 d, = 7.9100, n7 = 1.50137
, v7=56.4rs −−20,3095 d8=0.2230 rg =−55,1148 do=1.4990 , n, ,=1.8155
．． j', shi, =44.5r1o=74.1996 d,, =1.1000 r,, -00 dH=11.5000, nB=1.51633
, v, , = 64.2 pa 1°'' do = 0.276
5~7.885d6=7.7697~0.16Also, l,, MR is the imaging magnification of the rear conversion lens, r,, r2. r3... is the radius of curvature of each surface of the rear conversion lens, do is the rearmost glass of the interchangeable lens 7=I air distance to the first surface of the conversion lens, dl, d2.d3... According to this embodiment of the barrier conversion lens, when the interchangeable lens is attached This provides a focusing range from infinity to 0.6 m.

FIG. 8 shows a third embodiment of the present invention, in which focusing operation is performed by moving only the rear group 11b of the imaging optical system 11 in the optical axis direction, and each numerical value is as follows. It is common knowledge.

MR=1.85 r, =51.1971 dl-1,1478, n, =1.80400,
I/, =46.6r2=17.5855 d2=0.9599 r3=29.324 d3=4.284, n,=1.5927
, si, =3s, ar4 =-29,7263 d, =2.3636 r, =-26,0529 d, =1.3499, n, =1.804
00, v, =46.6ra =32s, as
ss d6-variable r, = 150.8132 d7 = 7.9084, n7 = 150137
, v, = 56.4 ra = -20,6858 d, = 0.223 r, , = -ss, a7t7 d, = 1.4899 , n, , = 1.8154
4, shi, = 44°5r, (, = 123.201
7 dlo-variable r,,=O1) d,,=11.5, ng=1.5163
3, ci,, = 64.2r, 2 = "1 da = 9.3121 ~ 0.77 ci, o = t, i ~ 9.64 Also, MR is the imaging magnification of the rear conversion lens,
rl + r2 + r3... is the radius of curvature of each surface of the rear conversion lens, cio is the air distance from the rearmost surface of the interchangeable lens to the first surface of the rear conversion lens, dl, d2. d3... is the thickness and air spacing of each lens of the rear conversion lens, nl, n3...
is the refractive index of each lens, ν1. ν, . . . are the Atsube numbers of each lens.

According to this embodiment, a focusing range from infinity to 1.5 m can be obtained by attaching the interchangeable lens.

In the embodiments described above, a light splitting prism is used to split the light beam, but it goes without saying that the present invention is not limited to this, and a light splitter with other configurations may be used.

Effects of the Invention As described above, according to the present invention, a rear compaction lens is disposed at the rear of the imaging optical system that forms an image of the light beam from the interchangeable lens on the film surface within the camera body. The structure consists of a light splitter and a light-receiving element arranged at a position conjugate with the film surface on the optical path branched by the light splitter, so it can be used in combination with a conventional camera body and an interchangeable lens. Since the light splitter is placed behind the imaging optical system, the light flux that passes through the light splitter is then processed by a lens, etc. before it reaches the film surface of the camera body. The state of the light flux that remains unchanged and is split by the light splitter is not changed in the same way before reaching the light receiving element, so that an image is formed on the film surface on the light receiving element arranged at a position conjugate with the film surface. Since it is possible to obtain an imaging state equivalent to the state, and there is no need to install an auxiliary lens in the optical path from the light splitter to the light receiving element, the optical system is simple, and the accuracy of light flux detection by the light receiving element is reduced. Since the beam incident on the light splitter is sufficiently converged by the imaging optical system and its diameter is small, the light splitter can be made compact, and thus the rear conversion lens The entire structure can be made compact, and by moving at least part of the imaging optical system and the light splitter in the optical axis direction, focusing can be achieved (if carried out, the size and weight of the interchangeable lens can be reduced by one weight). There are effects such as smooth focusing operation that can always be performed with a constant amount of force regardless of the situation.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing how an embodiment of the rear conversion lens according to the present invention is used, and FIG. 2 is an operational diagram of the embodiment shown in FIG. 1 when focusing is performed by moving the interchangeable lens. 3 to 5 are operation diagrams showing various methods of focusing operation according to the present invention in the embodiment shown in FIG. 1, and FIGS. 6 to 8 show specific embodiments of the rear conversion lens according to the present invention. FIG. 1°--rear conversion lens, 2...camera body, 3...interchangeable lens, 11...imaging optical system,
12... Light splitting prism, 13... Light receiving element. Figure 1 Spear 2 Figure 3 Figure 3 □ Figure 41 Figure 5 y! -6 figure 18 figure

Claims (2)

[Claims] (1) A rear conversion lens that can be attached between the camera body and the interchangeable lens of an interchangeable lens camera includes an imaging optical system that focuses the light beam from the interchangeable lens onto a film surface within the camera body, and It is characterized by including a light splitter arranged at the rear of the optical system, and a light receiving element arranged at a position conjugate with the film surface on the optical path branched by the light splitter. , rear conversion lens. (2) A rear camera according to claim (1), characterized in that the focusing operation is performed by moving at least part of the imaging optical system and the light splitter in the optical axis direction. conversion lens.