JPH0540491Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to the shape of a roof-type reflector used in a finder optical system of a single-lens reflex camera.

Conventional technology Instead of a glass pentagonal roof prism as a viewfinder optical system for single-lens reflex cameras,
A roof section with two reflective surfaces intersecting at right angles,
It is generally known to use a roof-type reflecting mirror configured with a second reflecting surface that guides the light that has been left and right reversed by these two reflecting surfaces to the eyepiece portion. The shape of the conventionally known roof-type reflector is the same as that of a glass penta-roof prism, and the surface formed by the rear end of the roof-type reflector, which is the exit surface of the penta-roof prism ( (hereinafter referred to as the rear end surface of the roof) is perpendicular to the reticle.

Problems that the invention aims to solve By the way, as single-lens reflex cameras are becoming more compact and lighter, there is also a demand for smaller and lighter viewfinder optical systems.
However, if, for example, a glass penta roof prism were to be downsized while retaining its conventional shape, the exit surface that emits light toward the eyepiece would also be downsized, so the exit surface would have to restrict the rays of the finder light even more. As a result, the eye relief becomes shorter. This problem also occurs at the rear end surface of a roof-type reflector. Furthermore, in the case of a glass pentagonal roof prism, if the shape is changed from a conventional prism, ghosting becomes a problem.

Therefore, an object of the present invention is to provide a lightweight and compact viewfinder optical system that maintains a certain level of eye relief by using a roof-type reflector.

Means for Solving the Problems In order to achieve the above object, the present invention moves the rear end surface of the roof of the roof-type reflector slightly forward of the plane perpendicular to the focus plate, so that the viewfinder field light flux from the focal point to the roof part is moved slightly forward. It is tilted at an angle that does not block the light rays reaching the lower part of the field of view.

Effect: With the structure of the roof-type reflector described above, the light ray restriction of the finder light by the rear end surface of the roof is less than when the rear end surface of the roof is perpendicular to the focus plate, and therefore the eye relief becomes longer. That is, when it is desired to ensure a certain level of eye relief, a lighter and more compact finder optical system can be constructed by tilting the rear end surface of the roof of the roof-type reflecting mirror.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a finder optical system using a roof-type reflector, where 2 is a roof portion of the roof-type reflector, and 3 is a second reflecting surface of the roof-type reflector. The image formed on the refocusing plate 1 is left and right reversed at the roof section 2 and converted into a second image.
It is guided to a reflective surface 3, where it is reflected backwards and passes through an eyepiece 4 to reach the eye. 5 is a light ray that reaches the lower part of the finder field of view out of the finder field of view light flux shown by a solid line. In a conventional glass penta-roof prism or roof-type reflector, the exit surface or rear end surface of the roof is connected to the focusing plate 1 as shown by the broken line in 6.
In contrast, in the present invention, the exit surface 7 is inclined at an angle that does not block the light ray 5. Ray 5 reaching the bottom of the viewfinder field of view
has an inclination of 3° to 6° from a plane perpendicular to the reticle, so the inclination of the exit surface 7 is also preferably about 3° to 6°.

FIG. 2 is a view of the exit surface viewed from the eyepiece side. The conventional roof rear end surface 6 in FIG. 1 and the roof rear end surface 7 of the present invention are designated by the same numbers in FIG. 2, respectively. 8 represents an eyepiece lens, and 9 represents a viewfinder optical axis. The ridge line formed by the intersection line of the two reflective surfaces of the roof section climbs upward as it goes forward, so the roof surface is tilted more than the roof rear end surface 6 that is perpendicular to the reticle. End face 7
As shown in the figure, the area of the motsumono can be larger.

FIG. 3 is a simplified view of the finder optical path at cross section A in FIG. 2 by expanding the reflection by the reflection surface of the roof portion and the second reflection surface. 1 is a focusing plate,
4 is an eyepiece lens, and 9 is an optical axis. As shown in FIG. 2, 10 is the open end of the rear end surface of the roof that is perpendicular to the focusing screen, and 11 is the open end of the rear end surface of the roof that is tilted with respect to the focusing screen. Of the light emitted from the focus plate, the field ray that passes through the limit of regulation by the aperture end 10 is designated as 12, and the field ray that passes through the limit of regulation by the aperture end 11 is designated as 13, and is shown by a broken line and a solid line, respectively. In other words, by tilting the rear end of the roof at a certain angle from the plane perpendicular to the focus screen, the area of the rear end of the roof is expanded, so the light ray restriction by the open end of the rear end of the roof is reduced, resulting in an eye relief as seen in the figure. becomes longer. Thinking about this from the opposite perspective, when a certain eye relief is set, the light restriction of the viewfinder light can be reduced by tilting the rear end of the roof, so that the rear end of the roof is perpendicular to the focusing screen. It is possible to create a more compact roof-type reflector than would otherwise be possible.

The following will explain what kind of problems occur when the exit surface of a glass pentagonal roof prism is similarly tilted. FIG. 4 is a sectional view of a conventional finder optical system using a glass pendant roof prism, where 14 is the pendant roof prism, and 5 is a ray of light from the finder field of view that reaches the lower part of the finder field of view. Unlike the above-mentioned roof-type reflector, the exit surface 15 exists substantially and forms an interface with the air, so a ghost ray 16 is generated due to total reflection at the exit surface 15. This appears in the shape of an inverted triangle below the regular screen of the finder field of view, and as the exit surface 15 approaches the light beam 5, it appears larger closer to the field of view. However, in the case of a roof-type reflector, the rear end surface of the roof does not form a boundary, so the above-mentioned ghost does not occur at all.

Effects of the Invention As described above in detail with reference to the embodiments, the rear end surface of the roof of the roof-type reflector is moved slightly forward of the plane perpendicular to the focus plate, and among the finder field light beams directed from the focus plate to the roof part. When trying to secure a certain eye relief by tilting the beam at an angle that does not block the rays reaching the lower part of the field of view, a more compact roof reflector can be made, and the finder optical system itself can also be made more compact. It becomes compact.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a finder optical system using a roof-type reflector representing an embodiment of the present invention, Fig. 2 is a view looking at the rear end of the roof from the eyepiece side, and Fig. 3 is shown in Fig. 2. FIG. 4 is a sectional view of a finder optical system using a glass pentagonal roof prism. 2... Roof portion, 3... Second reflective surface, 7... Rear end surface of roof, 5... Light ray reaching the lower part of the viewfinder field of view.

Claims (1)

[Claims for Utility Model Registration] 1. A roof section consisting of two reflective surfaces intersecting at right angles that inverts the observation light incident from the focusing plate and guides it forward; and a roof section that connects the light guided forward by the roof section. In a roof-type reflector having a second reflective surface that reflects toward the eye, a light ray that reaches the lower part of the visual field among the finder visual field light fluxes that travel from the focus plate to the roof part through the rear end surface of the roof formed by the rear end of the roof part. This roof-type reflector is characterized by being tilted at an angle that does not block the view. 2. The roof-type reflecting mirror according to claim 1, wherein the slope of the rear end surface of the roof is 3° to 6° from a plane perpendicular to the focusing plate.