KR20030048328A - compact variable-magnification finder - Google Patents

Abstract

PURPOSE: A small-sized variable finder is provided to obtain the high variable magnifying power and the high aberration performance by simplifying a structure of the small-sized variable finder. CONSTITUTION: A small-sized variable finder includes an object lens portion(1,2,3), a phase inversion lens portion, and an eyepiece portion. The object lens portion includes the first lens group having a negative refractive index, the second lens group having a positive refractive index, and the third lens group having the positive refractive index. The phase inversion lens portion changes an inverse image formed by the object lens portion to an erect image. The eyepiece portion observes the erect image of the phase inversion lens portion. The first lens group is shifted to the second lens group along an optical axis in order to satisfy a condition of 14.0<=L<=18.0 when a wide-angle stage is changed to a telephoto stage.

Description

Compact variable-magnification finder

TECHNICAL FIELD The present invention relates to a finder and, more particularly, to a small variable finder used in a compact camera.

Recently, many developments have been made in the compact camera for the purpose of easy portability and convenient use rather than various functions. With this trend, cameras are becoming smaller and smaller, and accordingly, the finder is becoming smaller and lighter.

As a finder optical system used in a conventional compact camera, a virtual image such as an Albada type or an inverse Galileo type was used. The virtual finder has a relatively wider field of view and eliminates the need for an erecting prism, which makes it possible to miniaturize the finder. However, the size of the first lens on the object side is increased and the boundary of the field of view is unclear, resulting in blurring of the outline.

Due to these shortcomings, a virtual finder has been adopted in recent years instead of a virtual finder.

The actual viewfinder is composed of an objective lens unit and an eyepiece unit, and has a form in which a user can observe the image of an image formed through the objective lens unit through the eyepiece unit. At this time, the image formed in the objective lens unit is reversed, and when the user observes the image through the eyepiece unit, the original subject is inverted, that is, the inverted image is visible. Therefore, the in-phase finder should be equipped with a phase inversion optical system for establishing an image formed through the objective lens unit. In addition, various methods have been used, such as using a mirror or a prism having various shapes in order to establish an image and make the overall length of the camera, that is, the size of the body as small as possible.

Conventional finder techniques include the following.

1) Japanese Unexamined Patent Publication No. 4-230719

2) Japanese Unexamined Patent Publication No. 10-227975

3) Japanese Unexamined Patent 2001-75023

In the above prior art, the finder disclosed in 1) is composed of three lens groups in which the objective lens unit has negative, positive and positive refractive power arrangements from the object side, and the first lens group and the second lens group are moved to shift and aberration. It is a structure to correct. However, the overall length of the objective lens unit is difficult to miniaturize. In particular, since the amount of movement of the second lens group is large and the total number of lenses is large, the mechanical configuration is complicated and productivity is reduced due to manufacturing difficulties.

Since the finder disclosed in 2) is composed of three lens groups each having a negative, positive and positive refractive power arrangement, the first lens group and the second lens group are moved to correct displacement and aberration. As described above, there is a problem that miniaturization is difficult and the mechanical configuration is complicated, and in addition, the number of lenses of the third lens group increases, leading to a manufacturing cost increase.

The finder disclosed in 3) has an objective lens unit consisting of three lens groups of negative, positive, positive or negative, positive and negative from the object side, and the first lens group and the second lens group are moved to correct displacement and aberration. On the other hand, it is possible to miniaturize the short length. However, in order to compensate for the deterioration of performance due to miniaturization, the second lens group is composed of aspherical lenses on both sides, and in particular, the structure of the inverted optical system is very difficult to use a free curved surface, resulting in difficulty in manufacturing and productivity. There is a falling problem.

Therefore, the technical problem to be achieved by the present invention is to provide a compact variable-speed finder having a simple structure of the lens and having high performance aberration characteristics.

1 is a diagram illustrating a zoom position structure of a small variable size finder according to a first exemplary embodiment of the present invention.

2 to 4 are aberration diagrams at the wide-angle end, the intermediate end, and the telephoto end of the small variable size finder according to the first embodiment of the present invention, respectively.

5 is a diagram illustrating a zoom position-specific structure of the small variable size finder according to the second exemplary embodiment of the present invention.

6 to 8 are aberration diagrams at the wide-angle end, the intermediate end, and the telephoto end of the small variable-speed finder according to the second embodiment of the present invention, respectively.

9 is a diagram illustrating a zoom position structure of the small variable-speed finder according to the third exemplary embodiment of the present invention.

10 to 12 are aberration diagrams at the wide-angle end, the intermediate end, and the telephoto end of the small variable-speed finder according to the third embodiment of the present invention, respectively.

In order to achieve the technical problem of the present invention, the small-variable finder according to the features of the present invention, the first lens group having a negative refractive power, the second lens group having a positive refractive power, and a positive refractive power in order from the object side An objective lens unit including a third lens group and forming an inverted image of an object corresponding to an incident ray; An image reversal lens unit for establishing an inverted image formed by the objective lens unit as a sizing image; And an eyepiece lens unit for observing an upright image established by the image inverting lens unit, wherein the first lens group and the second lens group move along the optical axis when the lens is shifted from the wide-angle end to the telephoto end, , (Mw: subject magnification at wide-angle end, Mt: subject magnification at telephoto end, L: distance from the first lens surface closest to the object side of the first lens group at the wide-angle end to the object side surface of the third lens group) Satisfies.

Besides, (fw: focal length of the objective lens portion at the wide-angle end, f1: focal length of the first lens group of the objective lens portion) is further satisfied.

In the variable displacement finder having such a feature, when changing from the wide angle end to the telephoto end, the first lens group moves to the image surface side and then to the object side, and the second lens group moves to the object side.

The first lens group may be formed of a concave lens on the object side, and the second lens group may be formed of a convex lens on both sides thereof. In addition, the third lens group may have an image side surface convex, and at least one or more surfaces may be reflective surfaces. In this case, the reflective surface of the third lens group has no refractive power.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1, 5, and 9 illustrate the structure of the small variable size finder according to each embodiment of the present invention for each zoom position.

1, 5, and 9, the small variable size finder according to the embodiment of the present invention includes the objective lens unit I, the image reversal lens unit II, And the eyepiece portion III.

As shown in FIGS. 1, 5, and 9, the objective lens unit I includes a first lens group 1 having a negative refractive power and a concave lens on the object side, and a positive refractive power and both convex surfaces. A second lens group 2 made of a lens and a third lens group 3 made of a lens having a positive refractive power and having an image side surface convex.

The first lens group 1 and the second lens group 2 move along the optical axis to perform a shift. When shifting, the first lens group 1 moves from the object side to the image side and then back to the object side. The second lens group 2 moves from the image side to the object side.

In the embodiment of the present invention, the third lens group 3 has at least one reflective surface while the image side surface is convex. Therefore, the third lens group 3 reflects the light emitted through the second lens group 2 and exits to the image reversal lens unit II, thereby functioning as the image reversal lens unit II for establishing the inverted image. Some of this may be performed, or may be a prism. The reflective surface of this third lens group 3 has no refractive power.

On the other hand, the inverted lens part II inverts the inverted image formed by the objective lens part I and outputs it to the eyepiece lens part III, whereby an upright image is observed through the eyepiece part III.

In the embodiment of the present invention having such a structure, the following conditions are satisfied in order to enable the variable displacement finder to be compact while having high performance aberration performance.

(Condition 1)

Here, L represents the distance from the first lens surface closest to the object side of the first lens group 1 at the wide-angle end to the object side surface of the third lens group 3.

Conditional Expression 1 above is to improve aberration performance while facilitating miniaturization. When the upper limit of Conditional Expression 1 is exceeded, the overall length of the objective lens unit I becomes long, which makes it difficult to miniaturize. When the lower limit of Conditional Expression 1 is not satisfied, the first lens group 1 and the second lens group 2 The power gets bigger, so all the aberrations get bigger.

(Condition 2)

Here, Mw represents a subject magnification at the wide-angle end, and Mt represents a subject magnification at the telephoto end.

Conditional Expression 2 relates to a variable ratio, and when the conditional expression 2 is not satisfied, the variable ratio becomes small and high magnification becomes difficult.

(Condition 3)

Here, fw represents the focal length of the objective lens unit I at the wide-angle end, and f1 represents the focal length of the first lens group 1 of the objective lens unit I.

Conditional Expression 3 is to improve aberration performance. If the upper limit of Conditional Expression 3 is exceeded, the power of the first lens group 1 is increased to increase all aberrations. If the lower limit of Conditional Expression 3 is not satisfied, the power of the second lens group 2 is increased to cause all aberrations. Becomes large. By satisfying Condition 3, the focal length of the first lens group 1 is maintained at an appropriate value with respect to the total focal length of the objective lens group I at the wide-angle end, so that the aberration performance is high even with a simple structure as described above. Can be maintained.

Example values of the small variable size finder according to the embodiment of the present invention satisfying these conditions (Conditions 1 to 3) are as follows.

F is the focal length, ri (i = 1-12) is the radius of curvature of the lens surface, di (i = 1-12) is the thickness of the lens or the distance between the lenses, nd is the refractive index, v is Dispersion value is shown. The unit of the value representing length is mm.

In each embodiment, the lens surface 8 is a primary imaging surface in which an image is formed by the objective lens unit I, and the lens surface 12 represents a surface in which an image is formed by the eyepiece lens unit III.

The magnification of the variable displacement finder according to the first embodiment of the present invention has a value of 0.339 to 0.865 between the wide-angle end and the telephoto end, and the angle of view (2ω) has a value of 55.12 ° to 20.44 °.

Table 1 shows an example value of each lens (including a prism) constituting the variable displacement finder according to the first embodiment of the present invention.

Face number Radius of curvature (r) Thickness, distance (d) Refractive index (nd) Variance (v) One ∞ D1 2 -10.0217 1.20 1.49176 57.4 * 3 14.8864 D3 * 4 7.9618 1.98 1.49176 57.4 5 -7.6558 D5 6 ∞ 13.20 1.49176 57.4 * 7 -4.8640 1.51 8 ∞ 24.00 1.52540 54.0 9 ∞ 0.60 * 10 18.9650 2.00 1.49176 57.4 11 -14.5930 18.00 12 ∞ 0.00

Where * represents an aspherical surface, and an equation for aspherical surface coefficient is as follows.

x: distance from lens vertex to optical axis direction

y: distance in the direction perpendicular to the optical axis

c: Inverse of the radius of curvature at the vertex of the lens (1 / R)

K: Conic constant

A ₄ , A ₆ , A ₈ , A ₁₀ : Aspheric coefficient

The coefficients of each aspherical surface according to the first embodiment of the present invention calculated according to Equation 1 are shown in Table 2 below.

Aspheric coefficient of the third side Aspheric coefficient of the fourth side K -0.9899017770E + 1 K -0.1320335329E + 2 A4 0.4755684157E-4 A4 0.1557082175E-2 A6 -0.1078317759E-3 A6 -0.1014902806E-3 A8 0.2317701524E-4 A8 0.9912044643E-6 A10 -0.1434474430E-5 A10 0.7516170798E-7

Aspheric coefficient of page 7 Aspheric coefficient of the tenth face K -0.2521063571E + 2 K -0.6801507124E + 1 A4 0 A4 0 A6 0 A6 0 A8 0 A8 0 A10 0 A10 0

And the distance D1 between the object side and the first lens group 1 of the objective lens unit I, which are changed during shifting, the distance D3 between the first lens group 1 and the second lens group, and The change amount of the distance D5 between the two lens groups 2 and the third lens group 3 is shown in Table 3 below.

Face number Wide-angle end (2ω = 55.12 °) Middle end (2ω = 31.63 °) Telephoto (2ω = 20.44 °) D1 0.000 2.648 1.482 D3 9.620 3.810 0.800 D5 1.701 4.864 9.040

Fig. 2 shows aberration characteristics at the wide-angle end of the shift finder according to the first embodiment of the present invention, which is composed of such embodiment values, Fig. 3 shows aberration characteristics at the intermediate end, and Fig. 4 shows the telephoto end. The aberration characteristic at is shown.

Further, the magnification of the variable-view finder according to the second embodiment of the present invention has a value of 0.339 to 0.865 between the wide-angle end and the telephoto end, and the angle of view (2ω) has a value of 55.12 ° to 20.44 °.

Table 4 shows exemplary values of each lens constituting the variable displacement finder according to the second exemplary embodiment of the present invention.

Face number Radius of curvature (r) Thickness, distance (d) Refractive index (nd) Variance (v) One ∞ D1 2 -10.4363 1.20 1.49176 57.4 * 3 15.7053 D3 * 4 8.3273 2.50 1.49176 57.4 5 -7.67473 D5 6 ∞ 13.20 1.49176 57.4 * 7 -5.0000 1.45 8 ∞ 24.00 1.52540 54.0 9 ∞ 0.60 * 10 18.9650 2.00 1.49176 57.4 11 -14.5930 18.00 12 ∞ 0.00

The coefficients of each aspherical surface according to the second embodiment of the present invention are shown in Table 5 below.

Aspheric coefficient of the third side Aspheric coefficient of the fourth side K -0.1643005576E + 2 K -0.1385258276E + 2 A4 0.2000477877E-3 A4 0.1431606374E-2 A6 -0.6244209515E-4 A6 -0.9284191166E-4 A8 0.1090263667E-4 A8 0.2806049401E-5 A10 -0.4059387156E-6 A10 -0.1472346713E-6

Aspheric coefficient of page 7 Aspheric coefficient of the tenth face K -0.3507213675E + 2 K -0.6801507124E + 1 A4 0 A4 0 A6 0 A6 0 A8 0 A8 0 A10 0 A10 0

And the distance D1 between the object side and the first lens group 1 of the objective lens unit I, which are changed during shifting, the distance D3 between the first lens group 1 and the second lens group, and The change amount of the distance D5 between the two lens groups 2 and the third lens group 3 is shown in Table 6 below.

Face number Wide-angle end (2ω = 55.12 °) Middle end (2ω = 31.63 °) Telephoto (2ω = 20.44 °) D1 0.000 3.282 2.517 D3 10.511 4.180 0.842 D5 1.790 4.840 8.943

Fig. 6 shows aberration characteristics at the wide-angle end of the shift finder according to the second embodiment of the present invention made up of such embodiment values, Fig. 7 shows aberration characteristics at the intermediate end, and Fig. 8 shows the telephoto end. The aberration characteristic at is shown.

Further, the magnification of the variable-view finder according to the third embodiment of the present invention has a value of 0.339 to 0.865 between the wide-angle end and the telephoto end, and the angle of view (2ω) has a value of 55.12 ° to 20.44 °.

Table 7 shows an example value of each lens constituting the shift finder according to the third embodiment of the present invention.

Face number Radius of curvature (r) Thickness, distance (d) Refractive index (nd) Variance (v) One ∞ D1 2 -11.0041 1.44 1.49176 57.4 * 3 15.9413 D3 * 4 8.7370 2.50 1.49176 57.4 5 -7.9583 D5 6 ∞ 13.20 1.49176 57.4 * 7 -5.0000 1.50 8 ∞ 24.00 1.52540 54.0 9 ∞ 0.60 * 10 18.9650 2.00 1.49176 57.4 11 -14.5930 18.00 12 ∞ 0.00

The coefficient of each aspherical surface according to the third embodiment of the present invention is shown in Table 8 below.

Aspheric coefficient of the third side Aspheric coefficient of the fourth side K -0.3242259586E + 2 K -0.1818657292E + 2 A4 0.5301941171E-3 A4 0.1993316766E-2 A6 0.3256565251E-4 A6 -0.1837099344E-3 A8 -0.1639937111E-4 A8 0.1219688704E-4 A10 0.1471076385E-5 A10 -0.5470590370E-6

Aspheric coefficient of page 7 Aspheric coefficient of the tenth face K -0.3105220893E + 2 K -0.6801507124E + 1 A4 0 A4 0 A6 0 A6 0 A8 0 A8 0 A10 0 A10 0

And the distance D1 between the object side and the first lens group 1 of the objective lens unit I, which are changed during shifting, the distance D3 between the first lens group 1 and the second lens group, and The change amount of the distance D5 between the two lens groups 2 and the third lens group 3 is shown in Table 9 below.

Face number Wide-angle end (2ω = 55.12 °) Middle end (2ω = 31.63 °) Telephoto (2ω = 20.44 °) D1 0.000 3.697 3.119 D3 11.442 4.663 1.089 D5 2.116 5.198 9.350

Fig. 10 shows aberration characteristics at the wide-angle end of the shift finder according to the third embodiment of the present invention having these embodiment values, Fig. 11 shows aberration characteristics at the intermediate end, and Fig. 12 shows the telephoto end. The aberration characteristic at is shown.

Conditional expression values of the present invention according to each embodiment having such characteristics are shown in Table 10 below.

Condition First embodiment Second embodiment Third embodiment L 14.5 16.0 17.5 Mw 0.339 0.339 0.339 Mt 0.865 0.865 0.865 Mt / Mw 2.55 2.55 2.55 f1 -11.99 -12.56 -13.01 fw 5.80 5.80 5.80 fw / f1 0.484 0.462 0.446

The invention is not limited to the embodiments described above, and various modifications and changes are possible within the scope of the following claims.

As described above, according to the exemplary embodiment of the present invention, it is possible to provide a small displacement finder having a high aberration performance while having a simple structure.

It is also possible to provide a small variable size finder with a wide field of view.

Claims (5)

In order from the object side, An objective lens unit including a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power to form an inverted image of an object corresponding to an incident ray ; An inverted lens unit for establishing an inverted image formed by the objective lens unit as a sizing image; And It includes an eyepiece for observing the sizing image established by the phase inversion lens unit, The small variable-speed finder in which the said 1st lens group and the 2nd lens group move along an optical axis at the time of a change from a wide angle end to a telephoto end, and satisfy | fills the following conditions. Mw: Magnification of the subject at the wide end Mt: magnification of subject in telephoto L: distance from the first lens surface closest to the object side of the first lens group at the wide-angle end to the object side surface of the third lens group The small variable finder according to claim 1, which further satisfies the following conditions. fw: Focal length of the objective lens unit at the wide end f1: focal length of the first lens group of the objective lens unit The method of claim 1, And the first lens group moves toward an image surface side and moves toward an object side, and the second lens group moves toward an object side when changing from the wide-angle end to the telephoto end. The method of claim 1, And the first lens group is formed of a concave lens on the object side, and the second lens group is formed of a convex lens on both sides thereof. The method of claim 1, The third lens group of claim 3, wherein an image side surface is convex, and at least one surface is a reflective surface.