JP2007323012A - Finder optical system and optical apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a finder optical system capable of removing harmful light among visible light caused by a double image ghost arising in an air gap part, and also, capable of preventing a harmful light leakage phenomenon due to an evanescent wave. <P>SOLUTION: Regarding the finder optical system having prisms 8 and 9 with an air gap part 14 between them, wherein a reflection ghost luminous flux is generated in the air gap part 14, the maximum value of the distance H of the air gap part is set so that a shift amount between a first reflection ghost luminous flux Y3 generated by first reflection on the incident surface 9a of the air gap part 14 and the finder luminous flux 6 may be smaller than eye resolution related to an image observed through eyepiece optical systems 10, 11 and 12, and the minimum value of the distance H of the air gap part 14 is set so that the leakage of total reflection light due to the evanescent wave may not occur. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a finder optical system and an optical apparatus, and more particularly to a finder optical system and an optical apparatus that are suitably used for a single-lens reflex camera, a lens shutter camera, a digital still camera, and the like.

  As a conventional finder optical system, there is disclosed a finder optical system in which the distance H between the air gap portions of the prism is set in a range of 0 <H ≦ 0.05 mm in order not to separate the ghost light beam and the normal light beam (for example, Patent Document 1).

  In addition, if the value of the air gap interval H is large, the optical path length varies greatly depending on the angle of the light beam incident on the prism and the location where the light beam passes through the prism, so aberration at the pupil position, particularly astigmatism, etc. The impact on will be greater.

Therefore, in consideration of these problems, the influence of the temperature and humidity differences of the prism material, manufacturing errors, etc., the air gap portion spacing H is set in a range of 0 <H ≦ 0.2 mm. (For example, refer to Patent Document 2).
JP-A-8-179400 Japanese Patent No. 3673048

  The above-mentioned Patent Document 1 does not disclose any solution for ghost, and the incident light is not totally reflected by the air gap portion even for the minimum value (0 <H) of the gap H of the air gap portion. It is only described that it cannot be made “0” because it cannot be made.

  On the other hand, the above-mentioned Patent Document 2 does not disclose anything regarding the viewfinder appearance, such as what the astigmatism will be if the air gap interval H is 0 <H ≦ 0.2 mm. Further, there is no disclosure or suggestion about the ghost generation of the double image in the air gap portion.

  Therefore, in Patent Document 1 and Patent Document 2 described above, the air gap portion of the air gap portion that removes the harmful light of the visual field light caused by the double image ghost generated in the air gap portion and prevents the leakage phenomenon of harmful light due to the evanescent wave. The technical significance of the interval H cannot be found.

  Therefore, the present invention is capable of removing the harmful light of the field light beam caused by the double image ghost generated in the air gap part, and preventing the harmful light leakage phenomenon due to the evanescent wave and An object is to provide an optical device.

  In order to achieve the above object, the finder optical system according to claim 1 has an air gap portion in a prism, and in the finder optical system in which a reflected ghost light beam is generated in the air gap portion, an interval between the air gap portions. The maximum value of H is set such that the amount of deviation between the first reflected ghost beam and the finder beam caused by the first reflection on the incident surface of the air gap portion is smaller than the eye resolution for the image observed through the eyepiece optical system. The minimum value of the distance H of the air gap portion is set so that light leakage from total reflection as an evanescent wave does not occur.

  An optical device according to an eighth aspect includes the finder optical system according to any one of the first to seventh aspects.

  According to the present invention, the maximum value of the gap H of the air gap portion is set so that the amount of deviation between the first reflected ghost beam and the finder beam is smaller than the eye resolution, and the total reflection from the evanescent wave is reduced. The minimum value of the interval H is set so that light leakage does not occur.

  Thereby, the ghost of the double image generated in the air gap portion can be made a size that cannot be confirmed with the naked eye, and harmful light in the field light can be removed. It is also possible to prevent harmful light leakage due to evanescent waves.

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic sectional view for explaining a camera as an optical apparatus having a finder optical system as an example of an embodiment of the present invention, and FIGS. 2 to 5 explain a ghost image generated in an air gap portion. It is explanatory drawing for. FIGS. 6 to 8 are views for explaining a process of forming an air gap portion, FIGS. 9 to 11 are views for explaining a finder optical system according to another embodiment of the present invention, and FIGS. FIG. 5 is a graph showing the relationship between visual acuity and eye resolution.

  A single-lens reflex camera (optical member) shown in FIG. 1 has a lens barrel 2 detachably attached to a camera body 1, and the lens barrel 2 has photographing lenses 3, 4, and 5 for photographing a subject. Is held. Subject light from the photographic lenses 3, 4, 5 is transmitted to the finder optical system via the reflection mirror 6 and the focus plate 7.

  As shown in FIGS. 1 and 2, the finder optical system includes prisms 8 and 9, and an air gap portion 14 is provided between the prisms 8 and 9.

  The prisms 8 and 9 are held back by the eyepiece 13 while returning to the same direction as the photographic lens optical axis while inverting the subject optical axis bent upward by the reflecting mirror 6 in the horizontal direction and vertical direction in the figure. It is sent out to eyepieces (eyepiece optical systems) 10, 11, and 12.

  More specifically, the subject optical axis X passes through the photographing lenses 3, 4, 5, is bent upward by the reflecting mirror 6 to become X 2, passes through the focusing plate 7 (although it is diffused to some extent by the focusing plate 7). (Omitted here) The light enters the prism 8 from the incident surface 8a of the prism 8.

  At this time, since the air gap portion 14 is provided between the prism 8 and the prism 9, and the angle formed by the total reflection surface 8b of the prism 8 and the light beam X2 satisfies the total reflection condition, the light beam X2 is totally reflected. It is totally reflected by the surface 8b and proceeds in the X3 direction.

  The roof surface mirror 8c of the prism 8 is subjected to silver vapor deposition or the like in order to reflect the light beam and to invert the left and right. Therefore, the light beam X3 is reflected by the surface of the roof surface mirror 8c to become the light beam X4. It reaches the reflecting surface 8b again.

  At this time, unlike the case of the light beam X2, the angle between the total reflection surface 8b and the light beam X4 is set so as not to be the total reflection angle, so that the light beam X4 travels from the total reflection surface 8b to the air gap portion.

  The light beam X4 is refracted at the air gap portion 14 like the light beam X5 and bent slightly downward, and enters the prism 9 from the incident surface 9a of the prism 9, and then the light beam X5 becomes the light beam X6.

  A light beam (finder light beam) X6 passes through the eyepieces 10, 11, and 12 from the exit surface 9b of the prism 9 and enters the eye lens 101 of the observer away from the eyepiece lens 12, and further enters the eye lens 101. To reach the retina 102 imaged. Thereby, the subject luminous flux X6 is recognized as a subject image.

  In this embodiment, since it is a single-lens reflex camera, at the time of shooting, the reflecting mirror 6 is raised, and the subject luminous flux imaged by the shooting lenses 3, 4 and 5 passes through the shutter mechanism to the image sensor. However, the imaging system and the like are omitted for the description of the finder system.

  Here, as shown in FIGS. 2 and 3, the light beam X5 transmitted through the total reflection surface 8b is slightly incident on the incident surface 9a of the prism 9 and proceeds to the light beam X6. Is reflected to generate a light beam Y1.

  The reflected light beam Y1 is reflected again by the total reflection surface 8b of the prism 8 separated by the interval H of the air gap portion 13, and becomes a reflected light beam Y2, reaching the incident surface 9a of the prism 9 again, and passing through the prism 9 The light beam Y3 passes through.

  Since this light beam Y3 is a ghost light beam generated by the first reflection with respect to the incident surface 9a of the prism 9, it is referred to as a first reflected ghost light beam. The first reflected ghost light beam Y3 travels through the prism 9, is scaled by the eyepiece lenses 10, 11, and 12, and reaches the eye lens 101 as the ghost light beam Y4.

  The angle θ formed when the ghost beam Y4 and the subject beam X6 enter the eye lens 101 from the final exit surface of the eyepiece 12 is the eye resolution (see FIG. 2). It is known that the angle θ, which is the resolution of the eye, is about 1 minute in normal human eyesight.

  FIG. 12 shows an eye resolution angle θ = 1 minute for a person with a visual acuity of 1.0, and an eye resolution angle θ = 0.5 minutes for a person with a visual acuity of 2.0. Is defined. Therefore, the condition that the ghost beam Y4 is not recognized as harmful ghost by the eye is that the eye resolution angle θ is less than 0.5 minutes, and (Z) × (eyepiece loupe magnification) <(limit incident angle θ of resolution). (= 0.5 minutes)) It is expressed by a formula of a considerable amount.

  Here, Z is an interval between the subject light beam (finder light beam) X6 and the first reflected ghost light beam Y3. Further, when this expression is converted into the distance H of the air gap portion 14, it is expressed by an expression of 800 nm ≦ H ≦ 0.01 mm / eyepiece loupe magnification.

  Note that the eyepiece loupe magnification is used in the above formula, because the interval Z between the subject light beam X6 and the first reflected ghost light beam Y3 is enlarged by the eyepieces 10, 11, and 12 with reference to FIG. This is because the luminous flux becomes Y4. Such enlargement of the light flux by the eyepieces 10, 11, and 12 is performed by a general finder optical system.

  The viewfinder optical system is not limited to the type shown in FIG. 2, and various designs are made. When the interval H of the air gap portion 14 is set in the present invention, the angle θ formed between the subject light beam X6 and the ghost light beam Y4 when entering the observer's eyes is made smaller than the eye resolution, so that the eyepiece loupe Conversion by magnification is required.

  Note that, under the conditions of the above two formulas, the light beam Y4 is recognized as ghost light for a person whose visual acuity is 2.0 or more. If this becomes a problem, it is possible to make the ghost light completely unrecognizable to everyone by setting the interval H of the air gap portion 14 narrow within a range where an evanescent wave described later does not occur. . However, it goes without saying that setting the upper limit value of the interval of the air gap portion 14 on the condition that most people cannot recognize it as a ghost is the intention of the present invention.

  Further, the reflected light beam Y2 described above is reflected on the surface of the incident surface 9a, although it is a very small amount of light when it reaches the incident surface 9a of the prism 9 in addition to proceeding to the first reflected ghost light beam Y3. Thus, a second reflected ghost light beam is generated.

  Considering the generation principle of this reflection ghost, although there is a considerable amount of attenuation, a ghost beam is repeatedly generated as in the third reflection ghost and the fourth reflection ghost. However, what is harmful to the appearance in the actual viewfinder optical system is that the first reflected ghost beam is mostly attenuated, and the ghost beam after the second reflected ghost is attenuated to the extent that it cannot be visually confirmed. Therefore, it will be ignored in the present invention.

  FIG. 3 shows an example in which the interval H of the air gap portion 14 is within the scope of the present invention.

  In FIG. 3, similarly to FIG. 2, the subject light beam X5 exits from the total reflection surface 8b of the prism 8, travels straight through the air gap portion 14, and reaches the incident surface 9a of the prism 9, and enters the prism 9. And the luminous flux Y1 reflected by the incident surface 9a of the prism 9.

  When the light beam X6 incident on the prism 9 travels straight through the prism 9 and reaches the exit surface 9b, the light beam X6 proceeds toward the eyepiece 10 as it is. On the other hand, the reflected light beam Y1 is reflected again by the total reflection surface 8b of the prism 8 to become a reflected light beam Y2, and again travels toward the prism 9 and enters the prism 9 from the incident surface 9a to become the first reflected ghost light beam Y3. Proceed in the direction of the eyepiece 10 from the surface 9b.

  Then, the first reflected ghost light beam Y3 having the same image component as the subject light beam shifted by the interval Z with respect to the subject light beam X6 passes through the eyepieces 10, 11, and 12 to become the light beam Y4. It becomes a ghost image.

  3 is set within the scope of the present invention, the angle θ formed by the subject light beam X6 and the ghost light beam Y4 is the resolution of the eye of the observer. Less than 5 minutes.

  Therefore, the first reflected ghost light beam Y3 cannot be distinguished from the subject light beam X6 by the observer, and a finder image having no ghost can be observed.

  FIG. 4 shows an example in which the interval H of the air gap portion 14 in FIG.

  4, when the subject light beam X4 exits from the total reflection surface 8b of the prism 8, the light beam X10 has the same angle as the light beam X5, reaches the incident surface 9a of the prism 9, and reaches the prism 9 as in FIG. The light beam X11 that enters the light beam and the reflected light beam Y10 that is reflected by the light incident surface 9a travel in a divided manner.

  At this time, the reflected light beam Y10 is reflected again by the total reflection surface 8b of the prism 8 to become a light beam Y11, enters the prism 9 from the incident surface 9a of the prism 9, and becomes the first reflected ghost light beam Y12, which becomes the eyepiece lens 10, 11 and 12. A ghost image is obtained by observing the light flux that has passed through the eyepieces 10, 11, and 12 with the eyes. In this example, the subject light flux X <b> 11 and the first reflected ghost light flux Y <b> 12 are only an interval Z <b> 1 that is greater than the interval Z. Shift.

  Thus, in proportion to the interval H of the air gap portion 14 being increased to the interval H1, the interval between the subject light beam X11 and the first reflected ghost light beam Y12 increases from the interval Z to the interval Z1. . Therefore, the angle θ when reaching the observer's eyes becomes 0.5 minutes or more, and a ghost image deviating from the subject image is observed, resulting in a very poor quality finder image.

  FIG. 5 shows an example in which the interval H2 between the air gap portions 14 is narrower than that in FIG.

  In FIG. 5, similarly to FIG. 3, the subject light beam X <b> 20 exits from the total reflection surface 8 b of the prism 8, travels straight through the air gap portion 14, and reaches the incident surface 9 a of the prism 9. And a light beam Y20 reflected by the incident surface 9a of the prism 9.

  The light beam Y20 is reflected again by the total reflection surface 8b, becomes a light beam Y21, enters the incident surface 9a again, proceeds toward the eyepiece lens 10 as the first reflected ghost light beam Y22, and is separated from the subject light beam X21 by an interval Z2. It becomes a shifted ghost and enters the observer's eyes.

  Here, it is assumed that the interval H2 of the air gap portion 14 in FIG. 5 is a very small interval, for example, an interval of less than 800 nm or almost as close as 0 mm. Therefore, the ghost image generated by the first reflected ghost light beam Y22 is merely an image shift of about 0.05 minutes or less with respect to the eyes of the observer, and the ghost image is not observed at all.

  However, when the distance H2 between the air gap portions 14 is set to a value smaller than the wavelength 350 nm to 800 nm in the visible light region in this way, an evanescent wave is generated when the subject light beam X2 incident on the prism 8 is totally reflected by the total reflection surface 8b. It protrudes out of the prism 8 from the total reflection surface 8b.

  The evanescent wave E is known to be difficult to propagate. However, if the subject luminous flux X2 is strong, the evanescent wave E also becomes strong, passes through the prism 9 (light leakage), and passes through the eyepiece to the observer's eyes. To reach a harmful ghost or flare image.

  Accordingly, by setting the interval H of the air gap portion 14 to 800 nm ≦ H ≦ 0.01 mm / eyepiece loupe magnification in the range of the present invention, generation of harmful ghost images and flare images due to the evanescent wave E is visible light (wavelength 350 nm). ˜800 nm).

  In this way, by setting the minimum value of the interval H2 of the air gap portion 14 to a value larger than the wavelength in the visible light region, light leakage from total reflection due to the evanescent wave can be prevented, and it can be viewed as a viewfinder field. Is significantly improved.

  When the interval H between the air gap portions 14 is 800 nm ≦ H, a harmful ghost or flare due to the evanescent wave E is generated in principle for a light beam having a wavelength of 800 nm or more. However, it is well known that the viewfinder is set to be observed by humans and the visibility characteristics of the human eye are in the visible light range, so that even if the light beam has a wavelength of 800 nm or more, the ghost light beam of the viewfinder can be seen. Needless to say, it has no effect.

  6 to 8 are perspective views for explaining a method of forming the air gap portion 14 of the present invention in which the distance H is 800 nm ≦ H ≦ 0.01 mm / eyepiece loupe magnification.

  In a method in which a spacer such as a general metal plate or plastic plate is interposed between the prisms 8 and 9, the interval H of the air gap portion 14 becomes too wide, and 800 nm ≦ H ≦ 0.01 mm / eyepiece loupe magnification. It is difficult.

  Therefore, in the present embodiment, a dry film is used as a spacer material interposed between the prisms 8 and 9, and the distance H of the air gap portion 14 is easily set to 800 nm ≦ H ≦ 0.01 mm / eyepiece magnifier magnification. The range can be set.

  The dry film is used for an etching mask of about several μm to several tens of μm, and the thickness uniformity is far superior to that of a general metal plate or plastic plate. Further, since the dry film can be selected by exposure after exposure and a portion to be removed, it can be used as a substitute for a prism mask.

  FIG. 7 shows a state where the dry film 20 is attached to the entire surface of the total reflection surface 8b of the prism 8 shown in FIG. When the mask shape is exposed to the opening 20a in FIG. 7, the dry film 20 positioned in the opening 20a changes.

  Then, when the changed dry film 20 is removed by alkali etching or the like, the mask portion 20b of the dry film 20 as a spacer for ensuring the interval H of the air gap portion 14 remains as shown in FIG.

  At this time, the delicate curved surface portion 20c1 corresponding to the curved surface edge portion of the mask that affects the appearance of the finder is also faithfully reproduced, and the straight portions 20c2 and 20c3 can be processed as clean edges instead of the surfaces cut by machining. it can.

  Next, FIG. 9 shows the subject image F before passing through the finder, and FIG. 10 shows the subject light flux passing through the finder having an air gap portion in the prism, so that the subject image F and the ghost image G are shifted by an interval A. The state is shown. This deviation interval A corresponds to the incident angle θ of the observer's eye. If the angle θ is less than 0.5 minutes, the subject image F and the ghost image G do not appear to be shifted.

  FIG. 11 is a diagram for explaining a finder optical system according to another embodiment of the present invention. The subject image J has a line width B of θ = 0.5 minutes, which is the limit of the resolution of the observer's eyes. The case where it has is shown.

  Here, in this embodiment, the maximum value of the distance H between the air gap portions 14 is set such that a dimension C obtained by subtracting the line width B from the deviation width A between the subject image J and the ghost image K is smaller than the line width B ( A−B = C and C <B) are set.

  As a result, the displacement width A is smaller than the eye resolution B, so the displacement width A cannot be recognized, and the ghost image K resulting from the first reflected ghost beam is the line width B that is a field image in the viewfinder. Equated. As a result, the discrepancy between the visual field image and the ghost image cannot be discriminated with the naked eye, and the ghost image can be substantially invisible.

  In this embodiment, when the distance H between the air gap portions 14 is maximum, that is, when the first reflected ghost light beam is slightly smaller than the line width B that is the limit of eye resolution, the line width B can only be seen about twice, but it cannot be seen by the double line. Therefore, the generation of the ghost is observed as if suppressed, and the ghost can be suppressed even in the worst case.

It is a schematic sectional drawing for demonstrating the camera as an optical apparatus provided with the finder optical system which is an example of embodiment of this invention. It is explanatory drawing for demonstrating the ghost image which generate | occur | produces in an air gap part. It is explanatory drawing for demonstrating the ghost image which generate | occur | produces in an air gap part. It is explanatory drawing for demonstrating the ghost image which generate | occur | produces in an air gap part. It is explanatory drawing for demonstrating the ghost image which generate | occur | produces in an air gap part. It is a perspective view for demonstrating the process of forming an air gap part. It is a perspective view for demonstrating the process of forming an air gap part. It is a perspective view for demonstrating the process of forming an air gap part. It is a perspective view which shows a to-be-photographed image. It is a perspective view for demonstrating the shift | offset | difference of a to-be-photographed image and a ghost image. It is a perspective view for demonstrating the finder optical system which is other embodiment of this invention. It is a graph which shows a visual relationship and the resolution | decomposability of eyes.

Explanation of symbols

H Spacing between air gap portions J Subject image K Ghost image Y3 First reflected ghost light beam X6 Viewfinder light beams 8, 9 Prism 9a Incident surface 14 Air gap portion 20 Dry film

Claims (8)

In the finder optical system which has an air gap part in the prism and a reflected ghost light beam is generated in the air gap part,
The maximum value of the distance H between the air gap portions is determined with respect to an image in which the amount of deviation between the first reflected ghost light beam and the finder light beam caused by the first reflection on the incident surface of the air gap portion is observed through the eyepiece optical system. Set it to be smaller than the eye resolution,
The minimum value of the interval H of the air gap portion was set so that light leakage from total reflection as an evanescent wave did not occur.
A viewfinder optical system.   2. The finder optical system according to claim 1, wherein a minimum value of the gap H of the air gap portion is a value larger than a wavelength in a visible light region. The wavelength in the visible light region is 350 nm to 800 nm,
The viewfinder optical system according to claim 2. Forming the air gap part using a dry film;
The finder optical system according to any one of claims 1 to 3. The amount of deviation between the first reflected ghost light beam and the finder light beam on the final exit surface of the eyepiece optical system is made smaller than an incident angle of 0.5 minutes with respect to the eyeball lens of the observer.
The finder optical system according to any one of claims 1 to 4, wherein The interval H between the air gap portions was 800 nm ≦ H ≦ 0.01 mm / ocular magnifier magnification,
The finder optical system according to any one of claims 1 to 5, wherein: The maximum value of the gap H of the air gap portion is set so that the dimension C obtained by subtracting the line width B which is the limit of eye resolution from the deviation width A between the subject image and the ghost image is smaller than the line width B. ,
The finder optical system according to any one of claims 1 to 4, wherein A finder optical system according to any one of claims 1 to 7,
An optical device.

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