JP2603892Y2 - Viewfinder prism structure - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of a prism used in a finder of a camera.

[0002]

2. Description of the Related Art In recent years, a real image type finder such as a lens shutter type camera uses a prism 30 as shown in FIG. 4 to convert an inverted image into an erect image. The prism 30 reflects the image incident from the incident surface 31 upward on the first reflecting surface 32, reflects the image in the incident direction on the second reflecting surface 33, and turns the image upside down. The light is reflected at 34, changes the optical path 90 ° lateral to the incident direction, and exits from the exit surface 35.

[0003] In recent years, a plastic molded product has been generally used for the prism 30. In plastic molding, it is convenient to have an overhanging shoulder portion for projecting a molded product from a mold, a knob for assembling into a finder, or a positioning fixing portion. Therefore, the first reflection surface 32
And the second reflection surface 33 intersect with the overhanging shoulder 37
Is provided.

[0004] However, a part of the light beam 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, proceeds into the optical path of the normal light, is reflected by the third reflection face 34, and is emitted from the emission face 35. The peripheral light La emitted from the emission surface 35 in this manner becomes harmful light such as ghost or flare.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the conventional prism, and has as its object to provide a prism structure which does not cause ghost.

[0006]

SUMMARY OF THE INVENTION In order to achieve this object, the present invention is a finder prism for reflecting a light beam incident from an entrance surface in a direction different from the incident direction by sequentially reflecting the light beams on a plurality of reflection surfaces. At the intersection of the adjacent reflecting surfaces, a projecting shoulder for fixing and projecting the prism at the time of molding is provided, and the end face of the projecting shoulder is moved in the direction of the incident surface by the light beam incident from the incident surface. It is characterized by being angled to reflect.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on illustrated embodiments. FIG. 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 in a real image type viewfinder of a camera, and an inverted object image formed by an objective lens can be observed as an erect image with a mirror 22 and can be observed as a real image through an eyepiece 23. To

The luminous flux (image) of the subject passing through the objective lens 21 is reflected laterally by the mirror 22, enters the prism 10 from the entrance surface 11, is reflected upward by the first reflection surface 12, and is reflected by the second reflection surface 12. The light is reflected in the incident direction by the reflection surface 13 and the image is inverted upside down. Further, the subject light beam is reflected laterally on the third reflection surface 14, exits the prism 10 from the exit surface 15, and exits the camera via the eyepiece 23.

The prism 10 has a first reflecting surface 1
2, a protruding shoulder 1 extending along the intersection of the first and second reflection surfaces 12, 13 at a portion where the second reflection surface 13 intersects
7 are protruded. The overhang shoulder 17 is
Functions as a protrusion for removing the molded product (prism 10) from the mold when the plastic injection molding is performed by the mold, and when mounted on the finder, it is fitted into the positioning groove of the finder (not shown). Prism 1
It acts as a means for positioning and fixing the zero. The prism 10 is not limited to a plastic injection molded product,
A glass prism may be used.

Since the overhanging shoulder 17 is formed integrally with the prism 10, the peripheral light beam La incident from the entrance surface 11 enters the overhanging shoulder 17. Overhang shoulder 1
The light beam that has entered the inside 7 is reflected by the end face 18 and returns to the inside of the prism 10 again. So, as mentioned earlier,
Depending on the reflection direction, the light exits from the exit surface 15 and the normal light beam L
n and becomes harmful light such as ghost.

Therefore, in the present embodiment, the end face 18 is inclined by θ from the direction parallel to the incident surface 11 toward 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 17 does not exit from the exit surface 15 or travels directly from the entrance surface 11.

As described above, in the prism 10 of this embodiment,
The end face 18 of the overhang shoulder 17 is formed at a predetermined angle,
The light reflected at 8 exits from the entrance surface 11 but exits at 1
Since no light is emitted from No. 5, no ghost is generated in the finder visual field.

Although the present invention has been described based on the illustrated embodiment, the present invention is not limited to this embodiment. In short, in the prism, when the overhanging shoulder is integrally formed at the portion where the adjacent reflecting surfaces intersect, an angle is set so that the light rays incident on the overhanging shoulder can be reflected in the incident direction or the direction deviating from the optical path of the normal light flux. You do it.

[0015]

As is apparent from the above description, in the present invention, a projecting shoulder for fixing and forming the prism is provided at the intersection of the reflecting surfaces adjacent to the prism, and the end surface of the projecting shoulder is formed as follows. Since the light beam incident from the incident surface is angled so as to be reflected in the direction of the incident surface, the light beam incident on the overhang shoulder from the incident light direction is reflected in the incident light direction. Does not emerge from the exit surface of the prism and become harmful light such as a ghost.

[Brief description of the 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 incorporating the prism.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Prism 11 Incident surface 12 1st reflective surface 13 2nd reflective surface 15 Outgoing surface 17 Overhang shoulder 18 Slant end surface

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-58-17429 (JP, A) JP-A-2-48643 (JP, A) JP-A-59-24803 (JP, A) JP-A-59-24803 24802 (JP, A) Fully open sho 59-66227 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03B 13/06-13/28 G02B 5/00-5/04 G02B 7/02

Claims (2)

(57) [Scope of request for utility model registration] 1. A finder prism, which sequentially reflects a light beam incident from an incident surface on a plurality of reflecting surfaces and emits the light in a direction at an angle different from the incident direction, wherein: Protruding or protruding shoulders at the time of forming the prism are provided, and an end face of the protruding shoulder is angled to reflect a light beam incident from the incident surface in the direction of the incident surface. The finder prism structure. 2. The prism according to claim 1, wherein the prism reflects the image incident from the incident surface on the first and second reflecting surfaces and inverts the image up and down. (4) The prism structure of the finder, wherein the light is reflected laterally and is emitted from the emission surface, and the overhanging shoulder is protruded from an intersection of the first and second reflection surfaces.