JPH0741536U - Finder prism structure - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a structure of a finder prism in which no ghost or the like occurs. A structure of a finder that reflects a light beam incident from an incident surface 11 in the order of a first reflective surface 12, a second reflective surface 13, and a third reflective surface 14 and emits it in a direction forming an angle different from the incident direction. The prism 10 includes the first adjacent
An overhanging shoulder portion 17 is provided at the intersection of the second reflecting surfaces 12 and 13 for projecting or fixing when the prism 10 is molded, and the end surface 18 of this overhanging shoulder portion 17 is formed into the incident surface 11 described above.
It is characterized in that the light flux incident from the above is angled so as to be reflected in the direction of the incident surface 11.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to the structure of a prism used in a finder of a camera.

[0002]

[Prior art and its problems]

 In recent years, real-image type viewfinders such as lens shutter type cameras use a prism 30 as shown in FIG. 4 in order to make an inverted image an erect image. The prism 30 reflects an image incident from the incident surface 31 upward by the first reflecting surface 32, reflects it in the incident direction by the second reflecting surface 33 and inverts the image vertically, and further reflects the third reflected light. The light is reflected by the surface 34, the optical path is changed 90 ° laterally with respect to the incident direction, and the light exits the exit surface 35.

Here, in recent years, the prism 30 is generally a plastic molded product. In plastic molding, it is convenient to have an overhanging shoulder for ejecting the molded product from the mold, and a knob for mounting in the finder or a positioning fixing part. Therefore, an overhanging shoulder portion 37 is provided at a portion where the first reflecting surface 32 and the second reflecting surface 33 intersect.

However, a part of the light flux incident from the periphery of the incident surface 31 enters the overhanging shoulder portion 37. Then, the peripheral light La is reflected by the end face 38 and advances into the optical path of the normal light, is reflected by the third reflecting face 34, and is emitted from the emitting face 35. The ambient light La emitted from the emission surface 35 in this way becomes harmful light such as ghost and flare.

[0005]

[The purpose of the device]

 The present invention has been made in view of the above problems of the conventional prism, and an object thereof is to provide a structure of a prism in which ghost does not occur.

[0006]

[Outline of the device]

 The present invention which achieves this object is a finder prism for sequentially reflecting a light beam incident from an incident surface on a plurality of reflecting surfaces and emitting the light in a direction forming an angle different from the incident direction. An overhanging shoulder is provided at the intersection for protrusion of the prism during fixing and molding, and the end face of the overhanging shoulder is angled to reflect the light flux incident from the incident surface toward the incident surface. It is characterized by being attached.

[0007]

【Example】

 The present invention will be described below with reference to illustrated embodiments. 1 is a side view of a prism according to the present invention, FIG. 2 is a perspective view of the prism, and FIG. 3 is a schematic view of an optical system of a finder incorporating the prism.

The prism 10 of this embodiment is used for a real image type viewfinder of a camera, and an inverted subject image formed by an objective lens is made an erect image by a mirror 22 and is observed as an actual image through an eyepiece lens 23. to enable.

A subject light flux (image) that has passed through the objective lens 21 is laterally reflected by the mirror 22, enters the prism 10 from the incident surface 11, and is reflected upward by the first reflecting surface 12. The image is reflected by the second reflecting surface 13 in the incident direction, and the image is turned upside down. Further, this subject light flux is laterally reflected by the third reflecting surface 14, is emitted from the exit surface 15 to the outside of the prism 10, and is further emitted to the outside of the camera via the eyepiece lens 23.

In this prism 10, an overhanging shoulder portion 17 extending along the intersection of the first and second reflecting surfaces 12 and 13 at the portion where the first reflecting surface 12 and the second reflecting surface 13 intersect. Is projected. The overhanging shoulder portion 17 functions as a protrusion for ejecting the molded product (prism 10) from the mold when the prism 10 is plastic-molded by the mold, and is shown in the figure when mounted on the finder. However, it fits in the positioning groove of the finder and acts as a positioning and fixing means for the prism 10. The prism 10 is not limited to a plastic injection molded product, and may be a glass prism.

Since the overhanging shoulder portion 17 is formed integrally with the prism 10, the peripheral light flux La that is incident from the incident surface 11 enters the overhanging shoulder portion 17. The light beam incident on the overhanging shoulder portion 17 is reflected by the end face 18 thereof and returns to the inside of the prism 10 again. Therefore, as described above, depending on the reflection direction, the light exits from the exit surface 15 and is mixed with the normal light flux Ln to become harmful light such as ghost.

Therefore, in the present embodiment, the end surface 18 is inclined from the direction parallel to the incident surface 11 by θ in the direction of the incident surface 11. That is, the angle θ is set so that the ambient light La that enters from the incident surface 11 and enters the overhanging shoulder portion 17 goes backward so as not to exit from the exit surface 15 or directly exits from the incident surface 11.

As described above, in the prism 10 of the present embodiment, the end surface 18 of the overhanging shoulder 17 is provided with a predetermined angle, and the light reflected by the end surface 18 is emitted from the incident surface 11. Since it is not ejected, there is no ghost in the viewfinder field.

Although the present invention has been described based on the illustrated embodiment, the present invention is not limited to this embodiment. In short, when forming an overhanging shoulder at the intersection of adjacent reflecting surfaces in a prism, the angle of light that is incident on this overhanging shoulder should be such that it can be reflected either in the incident direction or in the direction deviating from the optical path of the normal light beam. To do.

[0015]

[Effect of device]

 As is apparent from the above description, according to the present invention, a protrusion shoulder is provided at the intersection of the reflecting surfaces adjacent to the prism for protrusion during fixing and molding of the prism, and the end face of the shoulder is incident from the incident surface. Since the incoming light beam was angled to reflect it in the direction of the incident surface, the light beam incident on the overhanging shoulder portion from the incident light direction is reflected in the incident light direction, so the light beam incident on the overhanging shoulder portion is reflected. Does not emerge from the exit surface of the prism to become ghost or other harmful light.

[Brief description of drawings]

FIG. 1 is a side view of an embodiment of a prism according to the present invention.

FIG. 2 is a perspective view of the prism.

FIG. 3 is a schematic diagram of an optical system of a finder in which the prism is incorporated.

FIG. 4 is a side view showing an example of a conventional finder prism.

[Explanation of symbols]

 10 prism 11 incident surface 12 first reflective surface 13 second reflective surface 15 exit surface 17 overhanging shoulder 18 inclined end surface

Claims (2)

[Scope of utility model registration request] 1. A finder prism for sequentially reflecting a light beam incident from an incident surface on a plurality of reflecting surfaces and emitting the light in a direction forming an angle different from an incident direction, wherein: Providing an overhanging shoulder for protrusion or fixing during prism formation, the end surface of the overhanging shoulder is a light beam incident from the incident surface, and is angled to reflect in the incident surface direction, The viewfinder prismatic structure. 2. The prism according to claim 1, wherein the prism reflects the image incident from the incident surface by the first and second reflecting surfaces to turn it upside down, and the third reflecting surface moves the image by 90 degrees with respect to the incident direction. A prism structure of a finder characterized in that it is laterally reflected and emitted from an emission surface, and the overhanging shoulder portion is projectingly provided at an intersection of the first and second reflection surfaces.