JP2006276483A - Finder device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a finder device enabling a camera user to accurately and surely recognize the degree of the focusing of a photographic lens system in spite of simple constitution where miniaturization, lightening in weight and thinning are contrived. <P>SOLUTION: The finder device includes: a cemented lens element 2 whose refractive power is variable and which deviates diopter from a proper value when the photographic lens system of a camera is not focused; and a voltage application circuit 50 which applies voltage to the cemented lens element 2 in accordance with the degree of the focusing of the photographic lens system. The cemented lens element 2 has a structure where first fluid substance 21 and second fluid substance 22 having a refractive index different from each other are arranged along an optical axis X, and joined each other so as to fill a container 24 with, and also the shape of the joined surface 23 of the first fluid substance 21 and the second fluid substance 22 is changed in accordance with the voltage applied from the voltage application circuit 50. Furthermore, the finder device satisfies a predetermined conditional expression concerning the constitution of the cemented lens element 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a finder device used for a camera having an autofocus function, and more particularly to a finder device that allows a camera user to recognize that a photographing lens system is out of focus.

  Conventionally, various finder apparatuses that can make a camera user recognize that a photographing lens system is out of focus have been proposed (see, for example, Patent Document 1 and Patent Document 2).

  In the finder device described in Patent Document 1, an optical lens is detachably disposed between the objective lens and the eyepiece lens, and the objective lens and the eyepiece lens are in the out-of-focus state. By positioning the optical lens between the camera lens and the camera lens, the camera user can recognize that the taking lens system is out of focus as being out of focus.

  In the finder device described in Patent Document 2, a convex lens and a concave lens that have a refractive power of zero when they are brought into close contact with each other are disposed in the optical path of the inverse Galileo finder so that the photographing lens is not displaced from the focus position. Accordingly, by moving one of the convex lens and the concave lens along the optical axis, the camera user is made to recognize the in-focus state and the out-of-focus state of the photographing lens system.

JP 54-106225 A Japanese Utility Model Publication No. 62-39376

  However, since the finder device described in Patent Document 1 has an optical lens detachably disposed between the objective lens and the eyepiece lens, a physical mechanism for moving the optical lens is necessary. As a result, the structure of the finder apparatus becomes complicated and the size of the finder apparatus becomes large, and a compact camera cannot be obtained.

  Similarly, the finder apparatus described in Patent Document 2 moves either a convex lens or a concave lens arranged in the optical path of the inverted Galilean finder along the optical axis, and thus moves these lenses. Therefore, the structure of the finder apparatus becomes complicated and the size of the finder apparatus becomes large, and a compact camera cannot be obtained.

  In recent years, digital cameras that have become widespread have been desired to be smaller and lighter. In particular, the development of thin cameras has become an urgent task. Can not respond to.

  The present invention has been made in view of the above-described circumstances, and is a simple mechanism that is reduced in size, weight, and thickness, while accurately and reliably focusing a photographing lens system on a camera user. An object of the present invention is to provide a finder device that can recognize the degree of the above.

The finder apparatus of the present invention is a finder apparatus used for a camera having an autofocus function,
When the refractive power is variable and the taking lens system of the camera is out of focus, a cemented lens element that deviates the diopter from an appropriate value;
Voltage application means for applying a voltage to the cemented lens element according to the degree of focus of the photographing lens system;
The cemented lens element is formed by arranging a first fluid material and a second fluid material having different refractive indexes along an optical axis and filling a container so as to be joined to each other. According to the change of the voltage applied by the applying means, the shape of the joint surface between the first fluid substance and the second fluid substance changes,
The following conditional expression (1) is satisfied.

0.1 <| N _d1 −N _d2 | (1)
However,
N _d1 : Refractive index at the d-line of the first fluid substance N _d2 : Refractive index at the d-line of the second fluid substance

Further, the cemented lens element is configured to deviate the diopter from an appropriate value to the plus side when the photographing lens system of the camera is out of focus.
It is preferable that the following conditional expression (2) is satisfied.

2 <DI <6 (2)
However,
DI: Diopter of the cemented lens element

  Furthermore, it is preferable that the following conditional expression (3) is satisfied.

0.01 <L / | R | <0.1 (3)
However,
R: radius of curvature at the time of maximum deformation of the cemented lens element L: thickness of the cemented lens element

  In the present specification, “diopter” means diopter described on page 524 of “Physical and Chemical Dictionary (4th edition): Iwanami Shoten”.

  According to the finder device of the present invention, a simple structure can be obtained by using a cemented lens element that makes the refractive power variable and deviates the diopter from an appropriate value when the photographing lens system of the camera is out of focus. Finder device. In particular, it is possible to reduce the size, weight, and thickness required for digital cameras that have become widespread in recent years, and to accurately and reliably focus the shooting lens system to the camera user. The state can be recognized.

  In addition, by using a cemented lens element that deviates the diopter from the appropriate value to the plus side when the camera lens system is out of focus, the camera lens system is more accurately and reliably focused. Can be recognized. That is, the human eye is less adaptable when the diopter is shifted to the plus side than when the diopter is shifted to the minus side, and the diopter is shifted to the plus side. As a result, the effect of deviating from the diopter becomes remarkable.

  Further, by satisfying each conditional expression, it is possible to more effectively deviate from the diopter and make the camera user recognize the degree of focusing of the taking lens system accurately and reliably.

<Finder device>
Embodiments of a finder apparatus according to the present invention will be described below with reference to the drawings.
FIG. 1 is a configuration diagram of a viewfinder device according to a first embodiment of the present invention.
As shown in FIG. 1, the finder apparatus according to the first embodiment of the present invention includes a biconvex lens L, a biconvex prism P, and a cemented lens element 2 in order from the object side. In FIG. 1, X indicates an optical axis and 1 indicates an eye point.

<Bonded lens element>
The cemented lens element 2 has a first fluid material 21 and a second fluid material 22 having different refractive indexes arranged along the optical axis X and is joined to each other and filled in a container 24. The shape of the joint surface 23 between the first fluid substance 21 and the second fluid substance 22 changes according to the change in the voltage applied from the voltage application circuit 50. The refractive power changes as the shape of the surface 23 changes.

  The cemented lens element 2 is known as, for example, a Fluid Focus lens manufactured by Philips, the Netherlands, and has a conductive container having different refractive indexes in a cylindrical container whose both end faces in the optical axis X direction are transparent. Water-soluble liquid (for example, the first fluid substance 21) and a non-conductive oily liquid (for example, the second fluid substance 22) are encapsulated, and the water-soluble liquid is changed according to switching of the voltage applied to the container. The refractive power can be changed by changing the shape of the boundary surface between the functional liquid and the oily liquid by the surface tension. That is, at the time of out-of-focus, for example, the cemented surface 23 of the cemented lens element 2 has a curved surface shape (a cross section of the curved surface is shown) as shown in FIG. The cemented surface 23 of the cemented lens element 2 has a planar shape (a planar cross section is shown) as shown in FIG.

  Whether or not a voltage is applied to the cemented lens element 2 from the voltage application circuit 50 is determined by whether or not the subject image on the image sensor 52 by the photographing lens 51 is in focus.

  In other words, this photographing system includes an autofocus system, and the subject image on the image sensor 52 by the photographing lens 51 is subjected to predetermined image signal processing in the image signal processing unit 53, and how much the CPU 54 deviates from the in-focus position. Is determined. If the amount of deviation is greater than or equal to a predetermined value, the CPU 54 sends a signal to the motor drive circuit 55 instructing to move the photographing lens 51 so that the amount of deviation is small. The motor drive circuit 55 drives the motor 56 based on the instruction signal from the CPU 54 to move the photographing lens 51 in an appropriate direction. In such a system, since the CPU 54 determines the in-focus state and the out-of-focus state at that time, the determination result can be sequentially sent to the voltage application circuit 50. Therefore, the voltage application circuit 50 switches ON / OFF of the voltage application in the cemented lens element 2 based on the determination result sent from the CPU 54.

<Conditional expression>
This cemented lens element 2 satisfies the following conditional expression.

0.1 <| N _d1 −N _d2 | (1)
2 <DI <6 (2)
0.01 <L / | R | <0.1 (3)
However,
N _d1 : Refractive index at the d-line of the first fluid substance N _d2 : Refractive index at the d-line of the second fluid substance DI: Diopter of the cemented lens element (diopter)
R: radius of curvature at the time of maximum deformation of the cemented lens element L: thickness of the cemented lens element

  Next, the technical significance of the conditional expressions (1) to (3) will be described.

Conditional expression (1) is a conditional expression that defines an absolute value N _d1 -N _d2 of a difference in refractive index between two fluid substances bonded in the cemented lens element 2. In the conditional expression (1), when the absolute value of N _d1 −N _d2 is below the lower limit, the change in diopter with respect to the change in the radius of curvature R of the joint surface 23 becomes small, and the effective diopter deviates. I can't.

If the absolute value N _d1 -N _d2 of the difference between the refractive indexes of the two fluid substances is set to 0.5 or more, generally the light transmittance of the high refractive material is reduced (yellowish). Since a problem arises, it is preferable to make this less than 0.5.

  Conditional expression (2) is a conditional expression that defines the value of the diopter DI when deviating from the appropriate value. In the conditional expression (2), when the value of DI is below the lower limit, the diopter is not sufficiently deviated from the appropriate value, and the focusing of the photographing lens system is accurately and surely performed for the user. The out-of-focus state cannot be recognized. On the other hand, if the DI value exceeds the upper limit, the diopter will deviate from the appropriate value, and the information obtained through the viewfinder will be reduced. That is, when the value of DI exceeds the upper limit, even if the user looks into the viewfinder, the target cannot be accurately observed, and the camera cannot be pointed at the target.

  Conditional expression (3) defines the thickness of the cemented lens element with respect to the radius of curvature R at the time of maximum deformation of the cemented surface 23 of the cemented lens element 2, and below the lower limit, the cemented lens element with respect to the degree of deformation of R. The thickness of the film is too small, which is not preferable for production. When the upper limit is exceeded, the thickness of the cemented lens element becomes large, and a wide arrangement space is required. In particular, when the lens is disposed closest to the eye point as in Example 1 described later, the distance from the final exit surface to the eye point (eye relief) is shortened, resulting in poor usability.

<Specific values>
Specific data regarding the finder apparatus according to the first embodiment will be described below. In order to facilitate understanding of the distance relationship in the optical axis direction of the optical system of the apparatus shown in FIG. 1, FIG.

In Table 1 below, for the finder device of Example 1, the radius of curvature R (mm) of each lens surface, the distance between the top surfaces of the lenses (center thickness of each lens and the air space D (mm) between each lens, The refractive index N _d and Abbe number ν _d of each lens at the d-line are shown, where the numbers corresponding to the respective symbols in Table 1 are sequentially increased from the object side. Reference numerals 5, 6, and 7 represent the light incident surface, the cemented surface, and the light emitting surface of the cemented lens element 2, respectively.

  In Table 1 below, the surface marked with * to the left of the surface number represents an aspheric surface, and each aspheric surface is represented by the following aspheric expression.

Table 2 below shows the values of the eccentricity K and the fourth, sixth, eighth, and tenth aspheric coefficients A ₄ , A ₆ , A ₈ , and A _{10 related to} the aspheric surface.

  Table 3 below shows the values of the conditional expressions (1) to (3) in the finder apparatus of Example 1. That is, in the present embodiment, the radius of curvature of the cemented surface 23 of the cemented lens element 2 is 70.58 during out-of-focus, and the diopter at this time is 4 diopters. At the time of focusing, the radius of curvature of the cemented surface 23 of the cemented lens element 2 is ∞.

  As is apparent from Table 3 below, the finder apparatus of Example 1 satisfies the conditional expressions (1) to (3).

  In addition, the lens which comprises the optical system of a finder apparatus with a cemented lens element is not restricted to the thing of Example 1, For example, there may be one lens other than a cemented lens element, and it is good also as three or more. Further, the arrangement position of the cemented lens element is not limited to the case where it is closest to the eye point side.

  Further, the cemented lens element can be configured to deviate the diopter from the appropriate value to the minus side when the photographing lens system of the camera is out of focus.

1 is a configuration diagram of a viewfinder device according to a first embodiment of the present invention. The figure for demonstrating the change state of the joint surface according to a voltage application in the cemented lens element shown by FIG. FIG. 1 is an exploded configuration diagram of the optical system of the finder apparatus shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Eye point 2 Joint lens element 21 1st fluid substance 22 2nd fluid substance 23 Joint surface 24 Container 50 Voltage application circuit 51 Shooting lens 52 Image sensor 53 Image signal processing part 54 CPU
55 Motor drive circuit 56 Motor L Lens P Prism

Claims (3)

A finder device used for a camera having an autofocus function,
When the refractive power is variable and the taking lens system of the camera is out of focus, a cemented lens element that deviates the diopter from an appropriate value;
Voltage application means for applying a voltage to the cemented lens element according to the degree of focusing of the photographing lens system;
The cemented lens element includes a first fluid substance and a second fluid substance having different refractive indexes arranged along an optical axis, and is filled in a container so as to be joined to each other. According to the change of the voltage applied by the applying means, the shape of the joint surface between the first fluid substance and the second fluid substance changes,
A finder apparatus that satisfies the following conditional expression (1):
0.1 <| N _d1 −N _d2 | (1)
However,
N _d1 : Refractive index at the d-line of the first fluid substance N _d2 : Refractive index at the d-line of the second fluid substance The cemented lens element is configured to deviate diopter from an appropriate value to a plus side when the photographing lens system of the camera is out of focus.
The finder apparatus according to claim 1, wherein the following conditional expression (2) is satisfied.
2 <DI <6 (2)
However,
DI: Diopter of the cemented lens element The finder apparatus according to claim 1 or 2, wherein the following conditional expression (3) is satisfied.
0.01 <L / | R | <0.1 (3)
However,
R: radius of curvature at the time of maximum deformation of the cemented lens element L: thickness of the cemented lens element

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