JPH11242166A - Eyepiece, finder optical system and optical equipment having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively eliminate a harmful light performing an internal-surface reflection at the side edge surface (outside surface) of an ocular optical system without making the system larger by providing a light shielding groove at the side edge surface while making an eyepiece in the facade shape corresponding to a visual shape. SOLUTION: A harmful light which never reaches the pupil of an observer is made incident on the pupil by the internal-surface reflection at the side edge surface of a second lens to lower the visibility of a finder. For the purpose, the eyepiece has the constitution provided with a light shielding groove at the side edge surface of the lens to eliminate the harmful light satisfactorily. The lens has a facade shape analogous to a light beam effective area so as to be miniaturized as much as possible like it is seen in the figure (c). Since the light beam effective area is decided according to the shape of a visual field, the facade shape of the lens is decided according to the shape of the visual field. Since there is a possibility that one part of the harmful light reflected at the light shielding groove of the lens is left in the lens even after the light shielding groove is formed in this manner, a black coating is applied on the side edge surface together with the light shielding groove.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eyepiece lens, a finder optical system and an optical apparatus having the same, and is particularly preferably used for a single-lens reflex camera.

[0002]

2. Description of the Related Art An optical element for forming an erect image such as a pentaprism and an eyepiece constituting a viewfinder optical system of a single-lens reflex camera and an eyepiece are used to avoid interference with other parts or to reduce the size of the entire camera. In order to achieve this, it is general to reduce the portion other than the effective area of the light beam as much as possible to obtain a compact configuration. With such a configuration, the side end surface (outer peripheral surface) of the optical component exists close to the effective light area for observing the subject image, and the light reflected by the side end surface becomes harmful light and becomes a finder. Cause a decrease in visibility.

In a conventional finder optical system, in order to reduce such harmful light, it is common practice to reduce the intensity of reflected light by applying a black coating to the side end surfaces of each optical component. ing. Further, as disclosed in Japanese Utility Model Laid-Open No. 1-67627, for example, the side end face of the optical component is inclined with respect to the optical axis so that harmful light reflected by the side end face does not reach the direction of the pupil of the observer. Some are known.

On the other hand, in fields other than the finder optical system, it has been conventionally performed to form a light shielding groove on the side end surface of the optical component in order to remove harmful light reflected by the side end surface of the optical component. I have. For example,
In the wide-angle lens disclosed in JP-A-46408, a lens having a large center thickness and a long length in the optical axis direction at an outer peripheral portion is disposed, and a light-shielding groove is provided on a side end surface of the lens to remove harmful light. Are doing.

[0005]

However, the method of applying a black coating on the side end surface of the eyepiece has the advantage that the outside of the field of view of the finder can be easily darkened, but the side end surface of the eyepiece is simple. When the length in the optical axis direction becomes long, the effect of anti-reflection becomes insufficient. In particular, when the refractive index of the optical material of the eyepiece lens is higher than a certain level, there is a problem that it is difficult to reduce the reflectance at the side end face by ordinary black coating.

On the other hand, a conventional example in which a light shielding groove is provided on a side end face of a thick lens having a large center thickness constituting a wide-angle lens is a photographing lens, and thus the front shape of the lens is considered to be rotationally symmetric, and the effective light area is limited. When applied to an eyepiece optical system having a shape of a visual field (usually rectangular), the eyepiece optical system has many useless areas other than the effective ray area, and the finder optical system becomes large.

An object of the present invention is to provide a finder optical system capable of effectively removing harmful light internally reflected by a side end surface (outer peripheral surface) of an eyepiece optical system without increasing the size of the system. And

[0008]

To achieve the above object, an eyepiece according to a first aspect of the present invention has a front shape corresponding to a visual field shape, and is characterized in that a light-shielding groove is provided on a side end surface.

A finder optical system according to a second aspect of the present invention is a finder optical system for observing an object image formed by an objective optical system with an eyepiece optical system, and includes at least one optical member constituting the eyepiece optical system. A light shielding groove is provided on the side end surface.

An optical apparatus according to a third aspect of the present invention includes an objective lens and an eyepiece according to the first aspect of the present invention or a finder optical system according to the second aspect of the present invention.

In the method of manufacturing a lens according to the fourth aspect of the present invention, the side end surface of the lens is processed by using a grinding means having a projection for processing a light shielding groove on the ground surface, and the light shielding groove is formed on the side end surface of the lens. It is characterized by forming.

[0012]

(Embodiment 1) FIG. 1 is a sectional view of a finder optical system of a single-lens reflex camera to which the present invention is applied.

In FIG. 1, reference numeral 1 denotes a reticle, 2 denotes a pentaprism acting as an optical system for erect image formation, 3 denotes an eyepiece, and 4 denotes a position of a pupil of an observer (photographer). Reference numeral 5 denotes a taking lens, and 6 denotes a quick return mirror. Light from a subject forms an image on the reticle 1 via the taking lens 5 and the quick return mirror 6. The observer magnifies the subject image (object image) formed on the focusing screen 1 via the pentaprism 2 and the eyepiece 3 for observation.

In the present embodiment, the eyepiece 3
Are, in order from the object side, a first lens 3 having a negative refractive power.
1. It is composed of four lenses: a second lens 32 having a positive refractive power, a third lens 33 having a positive refractive power, and a fourth lens 34 having a negative refractive power. The distance (eye relief) from the exit surface of the eyepiece lens 3 to the pupil of the observer is made sufficiently long while it is large. Further, the diopter of the finder can be adjusted by moving the second lens 32 in the optical axis direction.

When an attempt is made to realize a finder optical system in which the finder magnification is increased and the eye relief is lengthened as in the present embodiment, an eyepiece must be used to satisfactorily correct various aberrations generated in the finder optical system. It is necessary to make the refractive power of each lens constituting the lens relatively high, and it is necessary to make the refractive index of the material of the eyepiece relatively high.

As shown in FIG. 2, the pupil 4 of the observer
The harmful light TL that does not reach the pupil 4 by being internally reflected at the side end surface of the second lens 32, and reduces the visibility of the finder. For this reason, in the present embodiment, the second lens 32 has a configuration in which a light-shielding groove is provided on the side end surface as shown in FIG. 3, and the harmful light TL is satisfactorily removed. FIG. 3A shows the second lens 3.
2, (b) is a top view, and (c) is a front view.
As can be seen from FIG. 3C, the third lens 32 has a frontal shape similar to the effective light area in order to reduce the size as much as possible. Since the effective ray region is determined according to the shape of the visual field, in other words, the front shape of the third lens 32 is also determined according to the visual field shape.

Since the harmful light reflected by the light-shielding groove of the third lens 32 may remain partially even after the light-shielding groove is formed as described above, the harmful light is conventionally used together with the light-shielding groove. It is desirable to apply a certain black paint to the side end face and the side end face.

In the present embodiment, a plurality of light-shielding grooves are formed in the optical axis direction. When the distance between the light-shielding grooves in the optical axis direction is L and the depth of the light-shielding groove is d, 0.03 <d / L <0.3 (1) It is configured to satisfy the following conditional expression.

Conditional expression (1) is a conditional expression for appropriately forming a plurality of light-shielding grooves and effectively removing harmful light, and defining the ratio of the depth and interval of the plurality of light-shielding grooves. This makes it difficult for harmful light to reach the pupil of the observer. When the ratio between the depth and the interval of the light-shielding groove becomes smaller than the lower limit value of the conditional expression (1), most of the reflected light on the side end surface of the eyepiece reaches the pupil of the observer, and the light-shielding effect is weakened. Come. Conversely, conditional expression (1)
If the ratio between the depth and the interval of the light-shielding groove becomes larger than the upper limit of the above, the flat portion of the side end surface of the eyepiece lens decreases and the number of defective parts such as chipping increases, and the number of light-shielding grooves increases. This is not preferable because it causes a problem that it becomes difficult.

Further, in the present embodiment, when the refractive index at the d-line of the lens in which the light-shielding groove is formed is Nd, the following conditional expression is satisfied: 1.60 <Nd (2)

Conditional expression (2) shows conditions for more effectively obtaining the effects of the present invention. Conditional expression (2)
Of course, even if the refractive index of the material of the eyepiece lens is lower than the lower limit of the above, the light-shielding groove is effective. Can be removed.

Next, a method of processing the eyepiece (second lens 32) of the present embodiment will be described.

FIG. 4 is a schematic diagram when processing the side end surface of the eyepiece. In FIG. 1, reference numeral 11 denotes an eyepiece whose side end surface is being processed, and reference numeral 12 denotes a grindstone for processing the side end surface of the eyepiece 11.

After the polishing of the lens surface is completed, the grindstone 12 moving in one side direction while rotating about a predetermined rotation axis is brought close to the eyepiece 11 fixed to the holding member 13 for processing the side end face, and the eyepiece is brought close. One side of the end face of the lens 11 is processed. Thereafter, each side is sequentially processed in the same manner to form an eyepiece 11 having a front shape corresponding to the visual field shape.

In this way, all the shaded areas of the eyepiece 11 of FIG. 4 are deleted, and the processing of the side end face is completed.
At this time, projections for processing light-shielding grooves are provided in advance on the grinding surface of the grindstone 12, and light-shielding grooves are formed simultaneously when processing each end face of the eyepiece 11.

FIG. 5 is a diagram showing a schematic shape of a grindstone 12 for performing such processing. The processing of the light-shielding groove of the eyepiece 11 is performed at the same time as the processing of the side end face using a grindstone having a new shape shown in FIG. 5, so that it is possible to realize the eyepiece without increasing the cost of parts.

(Embodiment 2) FIG. 6 is a sectional view showing another embodiment of a finder optical system of a single-lens reflex camera to which the present invention is applied. 6, members having the same reference numerals as those shown in FIG. 1 mean the same members.

In the present embodiment, the eyepiece 3 is
It is composed of a plurality of cemented lenses 35 and satisfactorily corrects chromatic aberration generated by the eyepiece. Thus, even when the eyepiece 3 is composed of the cemented lens 35, the length of the side end face in the optical axis direction is long, so that the configuration in which the light shielding groove is provided on the side end face is effective.

Since the third lens 32 of the first embodiment is made of an optical material having a relatively high refractive index and is a lens having a relatively large center thickness, harmful light which lowers the visibility of the viewfinder is generated. It was very effective to provide a light shielding groove on the side end face. The cemented lens 35 of the present embodiment
Although the refractive index of the optical material is not so high, since it is a cemented lens and the center thickness is relatively thick as described above, it is also effective to provide a light shielding groove on the side end face.

In the above description of the embodiment, the optical components forming the light-shielding groove are all eyepieces. However, when, for example, a prism for displaying information is arranged before and after the eyepiece, the end face of this prism is used. It is also conceivable to form a similar light-shielding groove in this case, and this can be said to be a modification of the present invention.

The following are numerical examples. Numerical Example 1 corresponds to the finder optical system of Embodiment 1, and Numerical Example 2 corresponds to the finder optical system of Embodiment 2.
In the numerical examples, ri is the radius of curvature of the i-th surface, di is the distance between the i-th surface and the (i + 1) -th surface, and ni and νi are the refractive index and Abbe number of the i-th optical member, respectively. The first surface and the second surface are the entrance surface and the exit surface of the pentaprism 2, respectively.

[0032]

[Outside 1]

[0033]

[Outside 2]

[0034]

As described above, according to the present invention,
Without increasing the size of the system, harmful light internally reflected by the side end surfaces of the eyepiece optical system can be effectively removed, and good visibility can be obtained in the viewfinder optical system.

[Brief description of the drawings]

FIG. 1 is a sectional view of a finder optical system of a single-lens reflex camera according to a first embodiment.

FIG. 2 is a diagram for explaining harmful light that reduces visibility of a viewfinder.

FIG. 3 is a three-view drawing of a second lens 32;

FIG. 4 is a schematic diagram when processing a side end surface of an eyepiece.

FIG. 5 is an explanatory diagram of a schematic shape of a grindstone 12;

FIG. 6 is a sectional view of a finder optical system of a single-lens reflex camera according to a second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Focusing plate 2 Penta prism 3 Eyepiece 4 Position of pupil of observer 5 Shooting lens 6 Quick return mirror

Claims (15)

[Claims] An eyepiece having a front shape corresponding to a visual field shape, wherein a light-shielding groove is provided on a side end face. 2. The eyepiece according to claim 1, wherein the eyepiece has a rectangular front shape. 3. The eyepiece according to claim 1, wherein an antireflection paint is applied to the side end surfaces and the light shielding grooves. 4. The light-shielding groove is formed in a plurality in the optical axis direction. When an interval between each light-shielding groove in the optical axis direction is L and a depth of the light-shielding groove is d, 0.03 <d / L <. 3. The conditional expression 0.3 is satisfied.
The eyepiece described. 5. The optical system according to claim 1, wherein a conditional expression of 1.60 <Nd is satisfied, where Nd is a refractive index of the constituent member with respect to the d-line.
The eyepiece described. 6. A viewfinder optical system for observing an object image formed by an objective optical system by an eyepiece optical system, wherein a light-shielding groove is provided on a side end surface of at least one optical member constituting the eyepiece optical system. Viewfinder optical system. 7. The finder optical system according to claim 6, wherein said optical member is an eyepiece having a front shape corresponding to a visual field shape. 8. The finder optical system according to claim 7, wherein said eyepiece has a rectangular front shape. 9. The finder optical system according to claim 6, wherein an antireflection paint is applied to the side end surfaces and the light shielding grooves. 10. The objective optical system is a photographing lens, and forms an object image on a reticle by the photographing lens.
10. The finder optical system according to claim 6, wherein the object image is observed by the eyepiece optical system including an image reversing optical member that uses the object image as an erect image. 11. A plurality of the light-shielding grooves are formed in the optical axis direction. When an interval of each light-shielding groove in the optical axis direction is L and a depth of the light-shielding groove is d, 0.03 <d / L <. 3. The conditional expression 0.3 is satisfied.
0. The finder optical system according to 0. 12. The optical system according to claim 6, wherein when the refractive index of the optical member with respect to the d-line is Nd, the following conditional expression is satisfied: 1.60 <Nd.
2. The finder optical system according to 1. 13. An optical apparatus comprising an objective optical system and an eyepiece according to claim 1 for observing an object image formed by the objective optical system. 14. An optical apparatus comprising an objective optical system and the finder optical system according to claim 6. 15. The lens according to claim 1, wherein a side end surface of the lens is ground by using a grinding means having a projection for processing a light shielding groove on the ground surface, and a light shielding groove is formed on the side end surface of the lens. Production method.