JPH02204730A - Finder optical system variable in observing direction - Google Patents

Abstract

PURPOSE:To obtain a finder optical system capable of easily observing the visual field of a finder and varying the observing direction by rotating a 3rd reflector in accordance with the observing direction in case of observation at a waist level and observing an object image formed on a 2nd focusing plate through a roof type reflection prism. CONSTITUTION:In an array level finder optical system, light flux 8 from an object is guided to the focusing 2 to form an image. The light flux diffused from the focusing plate 3 is observed from an array level direction through a 2nd reflector 4, a 3rd reflector and an eyepiece 6. In the case of waist level, the 3rd reflector 5 is rotated in an arrow direction, the light flux reflected by the 2nd reflector 4 is reflected to an upper oblique direction by the 3rd reflector 5 and the image of the reflected light flux is formed again on the 2nd focusing plate 11 through an image forming lens 9 and a 4th reflector 10. Thus, the object image on a 2nd focusing plate 11 can be observed from the upper or oblique direction in a natural posture.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a viewfinder optical system with a variable viewing direction, and in particular to a viewfinder optical system that uses a rotatable reflector to reflect a subject image formed on the viewfinder imaging plane by a photographing lens. This invention relates to a finder optical system that can change the observation direction and is suitable for photo cameras, video cameras, etc., which can switch between eye level and waist level (eye level and waist level). .

(Prior Art) Pentagonal roof prisms have been widely used for erect images in the finder optical systems of single-lens reflex cameras among still cameras.

This penta roof prism is generally manufactured by grinding and polishing a glass block material, but each reflective surface can also be constructed from a plate-shaped mirror (hereinafter referred to as a "hollow penta roof prism").

FIG. 5 is a schematic diagram of a main part showing the configuration of a conventional finder optical system using a hollow pentagonal roof prism.

In the figure, reference numeral 51 denotes a photographing lens, which condenses a light beam 58 from an object. 52 is a quick return mirror 53 is a focusing plate, on which a photographing lens 51 is mounted.
An image of the subject is formed. Reference numeral 54 denotes a roof-type reflecting plate, which inverts the subject image left and right. Reference numeral 55 denotes a flat reflecting plate 556 which is an eyepiece lens, through which the subject image formed on the focusing plate 53 is observed from an eye point 57.

In the figure, a light beam 58 from an object (not shown) is converged by a photographing lens 51 and reflected upward by a quick return mirror 52 to form an image of the object on an imaging plane of a focusing plate 53. Then, the luminous flux 5 from the subject image on the focusing plate 53
8 is reflected toward the subject side by the roof-type reflector 54,
It is reflected in the direction of the eyepiece lens 56 by the plane reflector 55,
Light is guided to the eyepiece lens 56 and observed from an eye point 57.

That is, the object image formed on the focusing plate 53 by passing through such an optical path is observed from the normal eye level (waist height) using the eyepiece lens 56. Further, a finder optical system using such a hollow pentagonal roof prism has been proposed, for example, in Japanese Patent Publication No. 31845/1983.

FIGS. 6(A) and 6(B) are schematic diagrams of the finder optical system proposed in the same publication. The same figure (A) shows that the view direction of the viewfinder field of view is at eye level, and the same figure (B)
is at waist level.

In FIGS. 5A and 5B, the same elements as those shown in FIG. 5 are given the same reference numerals. 65 is a rotatable flat reflector, 56' is an eyepiece, and roof-shaped reflector 5
It is placed diagonally in front of the 4.

In the same publication, the planar reflector 55 shown in FIG. 5 (the planar reflector 65 in FIG. 6) is rotatable, and the planar reflector 55
By rotating the roof type reflector 54, the reflected light beam from the roof type reflector 54 is adjusted to be at eye level (waist height) or waist level (
We have proposed a method that can selectively reflect the light toward any of the observation directions (at eye level).

That is, the operation at eye level in FIG. 5A is the same as that in FIG. 5 described above.

At the waist level in the same figure (B), the focus plate 53
A light beam 58 from the subject image formed on the roof reflector 5
4 and is reflected toward the subject side, and the plane reflector 6 is rotated as shown by the arrow with respect to the eye-level state shown in FIG.
5, the light passes through an eyepiece 56' and is guided to the observer's eye 57. The object image formed on the focusing plate 53 by passing through such an optical path is observed at waist level through the eyepiece lens 56'.

As described above, in the conventional finder optical system, by rotating the flat reflector 65 according to the observation direction, the reflected light beam from the roof-type reflector 54 is directed to either the observation direction at eye level or waist level. By selectively reflecting the light, the viewing direction of the viewfinder field can be changed.

However, in the conventional example, observation is performed from the same eye point position even when the waist level shown in FIG. I had to get close to the camera and look through the viewfinder.

Therefore, when observing at waist level, the observer has to observe the viewfinder field from above the camera, which poses problems such as having to bend forward in an awkward posture, making it difficult to observe.

(Problems to be Solved by the Invention) In order to solve the problems that occur when observing at waist level as shown in the above-mentioned conventional example, the present invention aims to direct the light beam reflected from the rotatable flat reflector to the imaging lens and the roof. The object image is formed on the focusing plate surface by passing through a reflective prism, and the eye point is made long so that the object image formed on the focusing plate surface can be observed. The purpose of the present invention is to provide a finder optical system in which a subject image can be observed in a natural posture, the viewfinder field of view is easy to see, the eye level and the waist level can be switched, and the observation direction is variable.

(Means for solving the problem) A roof-shaped reflecting surface in which a first reflector is disposed diagonally for the axial light flux that has passed through the photographic lens, and the reflected light flux from the first reflector is reflected toward the subject side. A second reflector having
A rotatable third reflector that selectively reflects the object is arranged, and the object image is observed from the horizontal direction through an eyepiece using the light beam reflected in the opposite direction to the object by the third reflector. and rotating the third reflector,
The light beam reflected toward the subject by the third reflector passes through an imaging lens and a fourth reflector having a roof-shaped reflective surface to form a subject image on the focusing plate surface. The object image formed on the plate surface is observed from above or diagonally above.

(Embodiment) FIGS. 1A and 1B are schematic diagrams of essential parts of a finder optical system with variable observation direction, each showing an embodiment of the present invention.

(A) shows the observation state (eye level finder optical system) at eye level, and (B) shows the observation state (waist level finder optical system) at waist level.

In the same figures (A) and (B), 8 is a light beam from a subject (not shown), 1 is a photographing lens, and 2 is a first reflector, which is made up of a quick return mirror. It is obliquely provided with respect to the optical axis of the shadow lens 1. Reference numeral 3 denotes a focusing plate, on which a subject image formed by the photographing lens 1 is formed. Reference numeral 4 denotes a second reflector, which is composed of a roof-shaped reflecting plate having a roof-shaped reflecting surface and a roof-shaped prism body, and is arranged obliquely with respect to the light beam from the focusing plate 3. 5 is the third reflector, and the fulcrum 5a
It is made up of a planar reflector that can be rotated around the center, and selectively reflects the reflected light beam from the second reflector 4 in two different directions. 6 is an eyepiece lens, 7 is an eye point position, and 9 is an imaging lens, which condenses the light beam from the third reflector 5. A fourth reflector 10 is made of a roof-shaped reflective prism having a roof-shaped reflective surface, and is fixed to a wall surface 13 inside the camera. 11 is a second focusing plate;
The imaging lens 9 consists of a diffuser plate, a Fresnel lens, etc.
A subject image is formed.

Next, the observation state of the subject image of the finder optical system in this embodiment will be described.

First, in the eye level finder optical system shown in FIG. 3A, a light beam 8 from an object (not shown) is converged by the photographic lens 1, reflected upward by the first reflector 2, and guided onto the surface of the focusing plate 3. A subject image is formed on that surface. The diffused light flux from the focusing plate 3 is reflected by the second reflector 4 towards the subject, reflected by the third reflector 5 in the direction opposite to the subject, and guided to the eyepiece 6. From the eye point 7, the subject image on the focus plate 3 is observed from the eye level direction.

In the observation state of the eye-level finder optical system shown in FIG. 5A, the reflected light beam from the second reflector 4 made of a roof-type reflector is selectively reflected by the third reflector 5 in the opposite direction toward the subject. , the imaging lens 9, the fourth reflector 10 consisting of a roof-type reflective prism, and the second focusing plate 11 are not used.

Next, in the waist level finder optical system, the third
The reflector 5 is rotated in the direction of the arrow in FIG. 1(A), and the light beam 8 reflected by the second reflector 4 is reflected toward the subject side as shown in FIG. 1(B), and the eye level is adjusted. The state of observation has changed from that of observation to that of waist level.

That is, the optical path of the light beam 8 that has passed through the photographic lens l is the same as the optical path shown in FIG. Because the second reflector 4 is rotated and positioned as shown in FIG. And the luminous flux 8 is the fourth
The light passes through the reflector 10 and is re-imaged onto the second focusing plate 11 surface. The subject image on the second focusing plate 11 is observed from above or from an oblique direction.

In the waist level finder optical system shown in FIG.
25 cm) or more (for example, in the same figure (
The viewfinder field of view can be observed from position 7a) shown in B), and can be observed in a natural posture without bringing the eye close to the eyepiece as shown in the conventional example (Fig. 6 (B)). . The second focusing plate 11 is preferably a diffuser plate, but a transparent plate can also be used.

In this way, in this embodiment, the observation distance of the subject image when the subject is at waist level is increased, thereby providing a finder system that is easy for the observer to view in a natural posture.

In this embodiment, the imaging lens 9 is replaced by the fourth reflector 10.
It may be arranged behind (on the second focusing plate 11 side).

Next, FIG. 2(A) shows the optical effect of the roof-type reflective prism 10 as the fourth reflector in this embodiment.

This will be explained using (B).

Figure (A) shows an imaging lens 9 in the form of a conventional finder optical system proposed in Japanese Patent Publication No. 48-31845.
A schematic diagram when the is inserted behind the third reflector 5, the same figure (
B) is a schematic diagram configuring the waist level finder optical system of the present invention.

In Figures (A) and (B), the same elements as those shown in Figure 1 are given the same reference numerals. Reference numeral 12 denotes a subject, whose positional relationship in the vertical and horizontal directions is indicated by arrows.

In the figure (A,), a light beam from a subject 12 passes through a photographing lens 1, is reflected upward by a quick return mirror 2, and forms an image on a focusing plate 3. A subject image is formed on the focusing plate 3, which is normal in the vertical direction but reversed in the horizontal direction. When the subject image formed on the focusing plate 3 is re-imaged on the second focusing plate 11 via the second reflector 4, the third reflector 5, and the imaging lens 9, On the second focusing plate 11, an image of the subject is re-imaged in the opposite directions both vertically and horizontally, which is not suitable for observing the subject image.

On the other hand, in FIG. 3(B), the vertical and horizontal positional relationships of the object images formed on the focusing plate 3 are the same as those shown in FIG. 3(A).

However, the second reflector 4, the third reflector 5, the imaging lens 9, and the fourth reflector 10 consisting of a roof-shaped reflective prism.
The upper and lower surfaces of the second focusing plate 11
A normal real subject image is formed in both the left and right directions. As a result, the corrected erect image of the subject is observed.

Figure 3 shows the roof-type reflective prism 10 shown in Figure 2 (B).
FIG. 2 is a perspective view of one embodiment of the invention. In the figure, 10 is a roof-shaped reflective prism, 10a is an entrance surface, 10b and 10c are roof-shaped reflective surfaces (roof surfaces), 10d is an exit surface, and 9 is an imaging lens.

In the figure, the light beam that has passed through the imaging lens 9 is at the incident surface 10.
Incident from a, roof surface 10b (point b), fOc (point c)
It is reflected in this order and exits from the exit surface 10d. Depending on the luminous flux, it may be reflected from the roof surfaces 10c and 10b in that order.

In this way, the light flux incident on the roof-type reflecting prism 10 is reflected by each of the roof surfaces 10b and 10c, thereby making it possible to observe an erect image of the subject corrected in the normal direction both vertically and horizontally as a whole. .

Incidentally, the roof-type reflecting prism described above may be configured as a hollow pentagonal roof prism.

FIG. 4 is a sectional view of an embodiment of the present invention in which the imaging lens and the roof-shaped reflective prism are integrated. In the figure, 10 is a roof-type reflecting prism, and an imaging lens 9 is fixed to its entrance surface. Note that 10e is the incident plane, 10
d is the exit surface.

In this embodiment, the entrance surface 1 of the roof-type reflecting prism 10 is
By making 0e a spherical surface and also serving as an imaging lens, it is integrated. This makes the entire device simpler and more compact.

If the optical member described above is molded from a material such as plastic, it can be manufactured at low cost and costs can be reduced.

Incidentally, the exit surface 10d may be made spherical and the imaging lens 9 may be formed integrally with the roof-type reflecting prism 10, or both the entrance surface 10e and the exit surface 10d may be made spherical and integrated. good.

Note that it is preferable to make one or both surfaces of the entrance surface 10e and the exit surface 10d aspherical because imaging performance can be further improved.

Further, in this embodiment, in order to set the eye point at a desired distance, a Fresnel lens having a positive refractive power is formed on the second focusing plate 11, or a Fresnel lens with a positive refractive power is provided near the second focusing plate 11. By arranging the lens, you can provide a viewfinder field of view that is easier to see.

Note that in the waist level finder optical system, when observing a subject image, a left-right reversed image may be allowed than in the past. In this case, the roof-type reflecting prism 10 may be constructed of a normal flat reflecting plate.

(Effects of the Invention) According to the present invention, by rotating a rotatable reflector, the reflected light beam from a hollow or solid roof prism is
When selectively observing at eye level and waist level by reflecting the light beam in one direction, in one observation, the light beam from the reflector is passed through an imaging lens and a roof-type reflective prism to form a subject image on a focusing plate, By observing the subject image on the focus plate, the observation distance can be extended, the subject image can be observed in a natural posture, and the viewfinder field of view can be easily viewed by switching between eye level and waist level. A finder optical system with variable observation direction can be achieved.

[Brief explanation of the drawing]

Figures 1 (A) and (B) are schematic diagrams of a finder optical system according to an embodiment of the present invention, with (A) at eye level and (B)
2(A) and 2(B) are schematic views of the finder optical system for explaining the optical function of the roof-type reflective prism according to the present invention, and FIG. 3 is a perspective view of the roof-type reflective prism. FIG. 4 is a sectional view of an integrated imaging lens and roof-type reflective prism according to another embodiment of the present invention, and FIGS. 5, 6 (A) and (B) are respectively conventional finder optical systems. In this schematic diagram, (A) is at eye level, and (B) is at waist level. In the figure, 1 is a photographing lens, 2 is a first reflector (quick return mirror), 3 is a focusing plate, 4 is a second reflector (roof type reflector), 5 is a third reflector (flat reflector), 6 is an eyepiece lens, 7 is an eye point, 8 is a luminous flux, 9 is an imaging lens,
10 is the fourth reflector (roof type reflective prism), 11 is the second reflector
This is the focus board. Figure (A)

Claims (1)

[Claims] (1) A first reflector is disposed diagonally with respect to the axial light flux that has passed through the photographic lens, and a second reflector has a roof-shaped reflective surface that reflects the reflected light flux from the first reflector toward the subject. , a rotatable third reflector is arranged to selectively reflect the reflected light flux from the second reflector in two different directions, one toward the subject and the other direction, and the third reflector selectively reflects the reflected light flux in the opposite direction to the subject. At the same time, the third reflector is rotated to condense the light beam reflected by the third reflector in the direction toward the object. The object image is formed on the focusing plate surface by passing through an image lens and a fourth reflector having a roof-shaped reflecting surface, and the object image formed on the focusing plate surface is observed from above or diagonally above. A finder optical system with a variable observation direction.