JPH1184473A - Observing optical system and optical instrument provided with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an observing optical system which will not sacrifice the facility in seeing, while providing a permanent clouding preventing property by having the observing optical system whose eye relief is at a specific value or below and forming a clouding preventing film having water absorptivity on the surface of a member which constitutes an eyepiece optical system and is nearest to an observer. SOLUTION: A camera consists of a camera main body 1, a photographic lens 2, a reflection mirror 3, a finder system 4, a rear cover 8, etc. The finder system 4 consists of a fousing screen 5, a pentagonal prism 6 and an eyepiece 7. In the camera, the clouding preventing film having the water absorptivity is formed on the surface 10, which is at least exposed to outdoor air and nearest to the observer side in optical members constituting the eyepiece 7, to prevent the clouding of the eyepiece 7 caused by the expiration of an observer. In the case the eye relief is >=25 mm, the observing optical system by such a constitution is most effective, especially in a finder whose eye relief is >=15 mm, more effect is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an observation optical system,
In particular, the present invention relates to an observation optical system suitably used for a finder optical system such as a camera.

[0002]

2. Description of the Related Art FIG. 5 is a schematic configuration diagram of a conventional single-lens reflex camera.

In FIG. 5, reference numeral 101 denotes a camera body, 10
2 is a photographing lens, 103 is a reflection mirror, 104 is a finder system including a focusing plate 105, a pentaprism 106, and an eyepiece 107, 108 is a back cover, and 109 is an eyepiece for forming an image formed on the focusing plate 105 by the taking lens 102. 107 represents the eyes of the photographer observing through 107.

In such a camera, exhalation from the photographer's mouth and nose rises along the surface of the camera's back cover 108 and passes between the eyepiece 107 and the observer's eye 109. Become. When the outside air temperature is low and the surface temperature of the camera 101 or the eyepiece 107 is low, part of the exhalation touches the surface of the eyepiece 107 of the finder,
When cooled, water droplets are formed, which may cause clouding and make it difficult to observe the viewfinder. In particular, if the mouth and nose are covered with a mask or the like to protect from the cold, fogging of the eyepiece 107 is more likely to occur, and in order to avoid such a state, the photographer is forced to hold his breath and shoot.

In order to solve such a problem, there has been known a method in which a solution having an antifogging effect such as a surfactant is thinly applied to the surface of an eyepiece.

[0006] In addition, as shown in FIG.
A hood 110 surrounding the periphery of the eyepiece 1
A method of making it difficult to touch 07 is also conceivable.

[0007]

As described above, various methods for preventing fogging due to exhalation of an eyepiece, which is a problem when a camera is used at a low temperature, can be considered variously. Have.

[0008] In the method of applying a surfactant, it is difficult to apply the same solution evenly to a slightly recessed surface of an eyepiece, and the antifogging effect is only temporary. Further, since the surfactant exerts an anti-fog effect by making the applied surface hydrophilic and enhancing so-called wettability, a thin water film is formed on the surface, and the amount of aggregated water droplets is large. In such a case, the observed image may be distorted.

On the other hand, in order to obtain a sufficient anti-fog effect in the method of providing the hood in the eyepiece shown in FIG. 6, it is necessary to increase the length L of the hood 110 to a certain extent or more. For example, in order to obtain an anti-fog effect even at a temperature of −10 ° C., it is desirable to set L to 20 mm or more. In this case, the distance between the eyepiece 107 and the observer's eye 109 is different. It will be about 25 mm apart. A numerical value generally referred to as an eye relief is used as an index indicating how much the finder field of view can be observed regardless of how far the eye is away from the eyepiece.
The finder system having an eye relief exceeding 5 mm has a problem that it is expensive because of its large size.

The present invention has been made in view of the above-mentioned conventional technology, and has as its object to realize an observation optical system having a permanent anti-fog effect without sacrificing visibility. .

[0011]

In order to achieve the above object, an observation optical system according to the present invention is an observation optical system having an eye relief of 25 mm or less, and the surface of a member closest to the observer constituting an eyepiece optical system. It is characterized in that an antifogging film having a water absorbing property is formed thereon.

Further, an optical apparatus according to the present invention is characterized by having the observation optical system according to the present invention.

Further, the optical attachment of the present invention is an optical attachment detachable between an eyepiece optical system and an eye of an observer, wherein an optical member and a space between the optical member and the eyepiece optical system are provided. Means for substantially isolating the optical member from the outside air, and a water-absorbing anti-fog film is formed on the surface of the optical member closest to the observer.

[0014]

FIG. 1 is a schematic diagram of a single-lens reflex camera having an observation optical system according to a first embodiment of the present invention.

In FIG. 1, 1 is a camera body, 2 is a photographic lens, 3 is a reflection mirror, 4 is a finder system including a focusing plate 5, a pentaprism 6, and an eyepiece 7, 8 is a back cover, and 9 is a photographic lens. Reference numeral 2 denotes an eye of a photographer who is observing an image formed on the focusing screen 5 through the eyepiece 7.

In such a configuration, when the observer observes the viewfinder, expiration from the observer's mouth and nose rises along the surface of the back cover 8 and passes between the eye 9 and the eyepiece 7. Conventionally, when the outside air temperature is low, a part of the exhaled air comes into contact with the cooled eyepiece lens 7 to cause aggregation and fogging. However, in the present embodiment, of the optical members constituting the eyepiece lens 7, a water-absorbing anti-fog film is formed at least on the surface 10 closest to the observer that comes into contact with the outside air, and the fogging of the eyepiece lens 7 due to the breath of the observer. Has been prevented.

When a long eye relief can be ensured, it is possible to prevent fogging by providing a hood at the eyepiece as described above to make it difficult for the exhaled air to directly touch the eyepiece 7. When the thickness is 25 mm or less, it is difficult to completely prevent fogging by such a method.

Therefore, the observation optical system of the present invention is most effective when the eye relief is 25 mm or less, and a smaller observation optical system, particularly, one eye relief is used.
A finder having a size of 5 mm or less is more effective.

Various antifogging agents for forming an antifogging film having a water absorbing property are known. In the present embodiment, the antifogging agent disclosed in JP-A-8-231944 is used. Was. This anti-fogging agent includes an inorganic alkoxide and OH formed by hydrolysis and polycondensation of the alkoxide.
A composition comprising at least one polymer having a group; a polyalkylene oxide; a catalyst; and a water-containing organic solvent.

As the alkoxide, at least one compound represented by the following formula is preferably used.

M (OR) _n (X) _an where M is Si, Al, Ti, Zr, Ca, Fe,
An inorganic atom selected from the group consisting of V, Sn, Li, Be, B, and P, R is an alkyl group, X is an alkyl group or an alkyl group having a functional group or a halogen, a is a valence of M, and n is 1 Represents an integer from to a.

As the above polyalkylene oxide,
Polyethylene oxide is preferably used.

As the above-mentioned base catalyst, N, N-dimethylbenzylamine is preferably used.

[0024] In addition to the above composition, at least one kind of polyacrylic acid may be contained. More specifically, at least one kind selected from polyacrylic acid, polymethacrylic acid, and salts thereof is preferably used. Used.

Table 1 shows an example of specific components and parts by weight of the antifogging agent.

[0026]

[Table 1]

Polyacrylic acid, N, N-dimethylbenzylamine and γ-glycidoxypropyltrimethoxysilane were added to a 10% polyethylene oxide (weight average molecular weight 300,000) methanol solution according to the components shown in Table 1. After stirring for 10 minutes, a previously prepared hydrolyzed solution of aluminum isopropoxide (Al ₂ O ₃ min 5%
Methanol solution) was mixed and stirred for 30 minutes, and the obtained solution was applied to both surfaces of the eyepiece or one surface exposed to the outside, and heated and dried (baked) at 150 ° C. for 10 minutes.

The obtained eyepiece is incorporated in a camera,
After being left in an environment of -10 ° C for 2 hours, the finder was observed under the same environment, and breathing was performed with the mouth and nose, but the eyepiece was not clouded.

Since the above-mentioned anti-fogging agent prevents fogging due to its water absorption, a film to be coated on the lens surface needs to have a certain thickness in order to exhibit the anti-fogging effect. In the case of the anti-fog agent having the above composition, in order to exhibit the effect under the general use conditions of the camera, at least 0.5 μm
The above film thickness is required. A film thickness of 1 μm or more is more desirable.

On the other hand, if a too thick film is formed on the lens surface, the surface accuracy of the surface deteriorates, and the observed image deteriorates. In order to observe the image without remarkable image deterioration, the film thickness of the antifogging agent applied to the lens surface needs to be 10 μm or less. It is more desirable that the thickness be 5 μm or less.

In the present embodiment, known techniques such as a dipping method, a spraying method, and a spinning method are used for coating the anti-fogging agent. However, when it is difficult to secure a sufficient thickness by a single film formation. The coating and baking may be repeated twice or more.

In this embodiment, the anti-fog film is applied directly to the eyepiece having a refractive power. However, a parallel flat glass having no refractive power provided as a protective member closest to the observer of the eyepiece optical system. May be applied to the observer side or both sides. A flat surface can more uniformly apply the anti-fog film to the surface than a surface having a curvature, and it is easier to maintain surface accuracy.
In addition, if it is a flat surface, a large-sized substrate can be coated with an antifogging film and cut into a required size in a later step, which is advantageous in terms of mass productivity.

FIG. 2 is a schematic configuration diagram of a single-lens reflex camera according to a second embodiment of the present invention. The same members as those in FIG. 1 are denoted by the same reference numerals.

In this embodiment, the eyepiece 7 'is
Unlike the eyepiece 7 of the first embodiment, no antifogging agent is applied to the surface thereof. Instead, in the present embodiment, the anti-fog unit 12 including the transparent member 11 is attached to the observer side of the eyepiece 7 '. Transparent member 11
Is a parallel plate glass, and the same anti-fog agent as in the first embodiment is applied to at least the surface 13 on the side facing the observer's eyes.

The anti-fog unit 12 of the present embodiment is
It is detachable from the camera 1 by the following mechanism.

FIG. 3 is an enlarged view of only the eyepiece of FIG. 2. FIG. 3 (a) is a central sectional view of a camera similar to FIG. 2, and FIG. 3 (b) is a view of the camera viewed from the observer side. Each of the eyes is shown. 3A and 3B, reference numerals 11 and 12 denote the transparent member and the anti-fog unit shown in FIG.
2 denotes an opening, 15 denotes a camera-side mounting frame for mounting the anti-fog unit 12, and 16 denotes a claw member for mounting the anti-fog unit 12 to the mounting frame 15 of the camera.

In FIG. 3B, grooves 17 are formed on the left and right sides of the mounting frame 15. On the other hand, the claw member 16 has elasticity, and the tip portion 18 can be opened and closed right and left. When the anti-fog unit 12 is installed, the claw members 16
Descend while fitting, and finally the tip 1 of the claw member 16
8 is dropped and locked at the end of the mounting frame 15. At the time of removal, the front end portion 18 of the claw member 16 is opened by pressing the side surface portion 19 of the anti-fog unit 12 from both sides, the engagement at the end portion of the mounting frame 15 is released, and it can be pulled out upward.

When the anti-fog unit 12 is mounted on the camera, the space between the transparent member 11 and the eyepiece 7 'is sealed, and it is particularly desirable to prevent the breath of the observer from below from entering the interior. . However, even if the necessary minimum gap is provided in the attachment portion for easy attachment and detachment, the inflow of exhaled air is sufficiently restricted, and the effect of the anti-fogging is hardly reduced.

In this embodiment, the transparent member 11 in the anti-fog unit 12 is a parallel plate glass.
This may be a lens having a curvature, and an antifogging film may be formed on one or both sides, so that the function of the antifogging and the function of a diopter correction lens of a finder can be provided.

When an antifogging film is applied to the surface of an optical component such as a viewfinder of a camera to have an antifogging effect, it is desirable that reflection on the surface be suppressed as much as possible. Various configurations of the anti-fog film having an anti-reflection effect can be considered,
The method disclosed in Japanese Patent Application No. 9-213269 by the present applicant is preferably used as having both anti-fogging property and anti-reflection property and excellent durability. In this method, a high-refractive-index thin film made of at least one substance of a metal alkoxide or a composite of a metal alkoxide and an inorganic substance is sandwiched between the above-described antifogging films.

FIG. 4 is a diagram showing a configuration of an anti-fogging film provided with an anti-reflection effect by the above method. In FIG.
2, a substrate glass corresponding to the transparent member 11 in FIG. 2, 21 is a first anti-fog film layer, 22 is a titanium tetraisopropoxide layer, and 23 is a second anti-fog layer made of the same material as 21. Each of the cloudy film layers is shown. Although the substrate glass 20 is shown as a plane for convenience, it may of course have a curvature.

The thickness of each layer is as shown in Table 2.

[0043]

[Table 2]

In Table 2, the first antifogging film layer and the titanium tetraisopropoxide layer have an actual film thickness, and the second antifogging film layer has an optical film thickness (refractive index × film thickness).

The first antifogging film layer is obtained by applying the same antifogging agent as in the first embodiment in the same manner. The thickness of the coating is related to the anti-fogging performance and the surface accuracy.
It is determined depending on the purpose from a range of about m to 10 μm, preferably about 1 μm to 5 μm.

The titanium tetraisopropoxide layer is obtained by applying a titanium tetraisopropoxide solution in isobutyl acetate by a dipping method and drying the coating, has a refractive index of 1.7 or more, and enhances the antireflection effect. Plays a role.

Since the second anti-fog film layer is very thin compared to the first anti-fog film layer, it is necessary to dilute the anti-fog agent with a solvent or the like to reduce the viscosity and apply the anti-fog agent. The thickness of the second antifogging film layer is set to １ ／ of the wavelength (design wavelength) at which the reflectance is to be reduced most. In the case of the present embodiment, the design wavelength is 540 nm (= 1).
35 nm × 4).

When the above film was formed on the transparent member 11 shown in FIG. 2 and tested, a sufficient antireflection effect was exhibited without impairing the antifogging property.

The film configuration and the film forming method for providing the anti-reflection effect are not limited to those shown in FIG.
No. 088, a method of forming a porous inorganic film on the anti-fogging film layer may be used.

In an environment in which the surface of a normal optical system that has not been subjected to anti-fog treatment becomes cloudy, dew condensation occurs not only on the surface of the optical system but also on the surface of the member holding the optical system. And flow to the surface of the optical system.

In view of such circumstances, it is desirable that the member holding the optical system having the anti-fogging film of the present invention is made of a material having a certain degree of hydrophilicity to prevent or reduce the flow of the water droplets. In terms of the numerical value of the contact angle of water indicating the degree of hydrophilicity, the holding member needs to be at least 90 ° or less, more preferably 70 ° or less. Specifically, there is a method of using a resin material meeting such conditions or forming fine irregularities on the surface.

[0052]

As described above, according to the present invention,
It is possible to realize an observation optical system that has a permanent anti-fog effect without sacrificing visibility.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a single-lens reflex camera according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a single-lens reflex camera according to a second embodiment of the present invention.

FIG. 3 is an enlarged view of a main part of a second embodiment of the present invention.

FIG. 4 is a configuration diagram of an antifogging film provided with an antireflection effect.

FIG. 5 is a schematic configuration diagram of a conventional single-lens reflex camera.

FIG. 6 is a schematic configuration diagram of a conventional single-lens reflex camera.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Camera main body 2 Photographing lens 3 Reflecting mirror 4 Viewfinder system 5 Focusing plate 6 Penta prism 7, 7 'Eyepiece 8 Back cover 9 Photographer's eye 10 Surface of eyepiece with anti-fog film formed 11 Transparent member 12 Anti-fog Unit 13 Surface of the transparent member on which the antifogging film is formed

Claims (18)

[Claims] 1. An observation optical system having an eye relief of 25 mm or less, wherein a water-absorbing anti-fog film is formed on a surface of a member closest to an observer constituting an eyepiece optical system. system. 2. The observation optical system according to claim 1, wherein the member on which the antifogging film is formed is an eyepiece. 3. The observation optical system according to claim 1, wherein the member on which the antifogging film is formed is a protection member for protecting an eyepiece. 4. The anti-fogging film comprises an inorganic alkoxide and O formed by hydrolysis and polycondensation of the inorganic alkoxide.
The observation optical system according to any one of claims 1 to 3, wherein the observation optical system is constituted by a composition containing at least one kind of polymer having an H group. 5. The anti-fogging film having a thickness of 0.5 μm or more and 1
The observation optical system according to claim 1, wherein the observation optical system has a thickness of 0 μm or less. 6. The observation optical system according to claim 1, wherein a film having an antireflection property is formed on the surface of the member. 7. The observation optical system according to claim 6, wherein the film having antireflection properties is a thin film made of at least one substance of a metal alkoxide or a composite of a metal alkoxide and an inorganic substance. . 8. The observation optical system according to claim 6, wherein the film having antireflection properties is a porous inorganic film. 9. The observation optical system according to claim 1, wherein the member holding the eyepiece optical system on which the antifogging film is formed has a contact angle with water of 90 ° or less. 10. An optical apparatus comprising the observation optical system according to claim 1. 11. An optical attachment detachable between an eyepiece optical system and an observer's eye, wherein the optical member and a space between the optical member and the eyepiece optical system are substantially isolated from the outside air. An optical attachment, wherein a water-absorbing anti-fog film is formed on the surface of the optical member closest to the observer. 12. The optical attachment according to claim 11, wherein the optical member has a refractive power. 13. The anti-fogging film is constituted by a composition containing at least one of an inorganic alkoxide and a polymer having an OH group formed by hydrolysis and polycondensation of the inorganic alkoxide. Claim 1
13. The optical attachment according to items 1 and 12. 14. The antifogging film according to claim 11, wherein the thickness of the antifogging film is 0.5 μm or more and 10 μm or less.
3. The optical attachment according to 3. 15. The optical member according to claim 11, wherein a film having an antireflection property is formed on the surface of the optical member.
Optical attachment as described. 16. The optical attachment according to claim 15, wherein the film having antireflection properties is a thin film made of at least one substance of a metal alkoxide or a complex of a metal alkoxide and an inorganic substance. 17. The optical attachment according to claim 15, wherein the film having antireflection properties is a porous inorganic film. 18. The optical attachment according to claim 11, wherein the member holding the optical member has a contact angle with water of 90 ° or less.