JP4534120B2 - Real-image variable magnification finder and imaging device - Google Patents

Description

  The present invention relates to a novel real image type variable magnification finder and an imaging apparatus. More specifically, the present invention relates to a high-magnification real image type zoom finder suitable for mounting on a digital still camera or the like and having good optical performance, and an imaging apparatus including such a real image type zoom finder.

  Conventionally, in a camera in which a photographing system and a finder system are separately provided, when the photographing system has a scaling function, the finder system is also provided with a scaling function corresponding to fluctuations in the photographing field angle. As such a finder system, various real image type variable magnification finders having a good view of the field frame have been proposed.

  As a real image type zoom finder, those described in Patent Document 1 and Patent Document 2 are known. The objective lens system includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens having a positive refractive power. It consists of groups and has achieved a zoom ratio of about 2 to 4 times.

JP-A-2-173713

JP-A-6-102454

  In recent years, in the field of digital still cameras, there is an increasing demand for zooming ratios exceeding 4x, and the finder system is compatible with high zooming objective optical systems while maintaining compactness. It is demanded. However, the finder systems described in Patent Document 1 and Patent Document 2 described above have a low zoom ratio and cannot meet such requirements.

  On the other hand, in order to increase the zoom ratio, it is necessary to increase the refractive power of the lens group that contributes to zooming. However, it is extremely difficult to correct various aberrations that occur in each lens group while maintaining a compact size. It is difficult to.

  The present invention has been made in view of such a situation, and provides a real image type zoom finder and an image pickup apparatus which realize a high zoom ratio exceeding 4 times while having a small and good optical performance. Let it be an issue.

In order to solve the above-described problems, the real image type zoom finder of the present invention converts an objective optical system having a positive refractive power and an inverted image formed by the objective optical system in order from the object side into an erect image. And an eyepiece optical system having a positive refractive power for observing the erect image. The objective optical system has a first lens group having a positive refractive power and a negative refractive power. The zoom lens includes a second lens group, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. The second lens group and the third lens group are moved on the optical axis to change the magnification and change the magnification. In the real-image magnification finder for correcting diopter change accompanying magnification, Z2 = β2t / β2w, Z3 = β3t / β3w, β2w is the lateral magnification at the wide angle end of the second lens group, and β2t is the second lens. The lateral magnification at the telephoto end of the group, β3w, of the third lens group With the lateral magnification at the corner end, β3t as the lateral magnification at the telephoto end of the third lens group, f2 as the focal length of the second lens group, and fw as the focal length at the wide-angle end of the objective optical system, the following conditional expression ( 1) Z2 · Z3> 4.0, (2) 0.60 <| f2 | / fw <1.00 , (3) 0.75 <1 / Z3 <0.90 .

  Therefore, the real image type zoom finder of the present invention has a high zoom ratio exceeding 4 times and good optical performance.

In order to solve the above-described problems, the imaging apparatus of the present invention includes a variable focal length lens, a recording unit that records a subject image captured by the variable focal length lens, and a change in the focal length of the variable focal length lens. An imaging apparatus including a real image type zoom finder whose viewing angle is changed in accordance with an angle of view that changes with the object, wherein the real image type zoom finder is an objective having a positive refractive power in order from the object side. An optical system, a reversal optical system for converting an inverted image formed by the objective optical system into an erect image, and an eyepiece optical system having a positive refractive power for observing the erect image. The optical system includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. 2 lens group and 3rd lens group While moving on the optical axis to correct zooming and diopter change accompanying zooming, Z2 = β2t / β2w, Z3 = β3t / β3w, and β2w is the lateral magnification at the wide angle end of the second lens group , Β2t is the lateral magnification at the telephoto end of the second lens group, β3w is the lateral magnification at the wide-angle end of the third lens group, β3t is the lateral magnification at the telephoto end of the third lens group, and f2 is the second magnification of the second lens group. The following conditional expressions (1) Z2 · Z3> 4.0, (2) 0.60 <| f2 | / fw <1.00 , where the focal length, fw is the focal length at the wide angle end of the objective optical system ( 3) 0.75 <1 / Z3 <0.90 is satisfied.

  Therefore, the image pickup apparatus of the present invention can be provided with a real image type zoom finder having a high zoom ratio exceeding 4 times and good optical performance.

The real image variable magnification finder according to the present invention includes, in order from the object side, an objective optical system having a positive refractive power, an inversion optical system for converting an inverted image formed by the objective optical system into an erect image, and the positive optical system. The eyepiece optical system has a positive refractive power for observing a standing image, and the objective optical system includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a positive refractive power. And a fourth lens group having a positive refractive power, and the second lens group and the third lens group are moved on the optical axis to correct magnification change and diopter change accompanying magnification change. A real-image magnification finder, wherein the following conditional expressions (1), (2) , and (3) are satisfied when Z2 = β2t / β2w and Z3 = β3t / β3w.

(1) Z2 · Z3> 4.0
(2) 0.60 <| f2 | / fw <1.00
(3) 0.75 <1 / Z3 <0.90
However,
β2w: Lateral magnification at the wide-angle end of the second lens group β2t: Lateral magnification at the telephoto end of the second lens group β3w: Lateral magnification at the wide-angle end of the third lens group β3t: At the telephoto end of the third lens group Horizontal magnification f2: focal length fw of second lens group: focal length at the wide angle end of the objective optical system.

In addition, the imaging apparatus according to the present invention responds to a variable focal length lens, a recording unit that records a subject image captured by the variable focal length lens, and an angle of view that changes as the focal length of the variable focal length lens changes. An image pickup apparatus having a real image type variable magnification finder in which a viewing angle is changed, and the real image type variable magnification finder includes, in order from an object side, an objective optical system having a positive refractive power, and the objective optical system. It is composed of a reversing optical system for converting an inverted image to be an erect image and an eyepiece optical system having a positive refractive power for observing the erect image, and the objective optical system has a positive refractive power The first lens group includes a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. The second lens group and the third lens group are Zooming and zooming by moving on the optical axis While correcting the diopter change caused, Z2 =? 2t / .beta.2w, as Z3 = [beta] 3t /? 3w, the following conditional expression (1), (2), an imaging apparatus that satisfies the (3).

(1) Z2 · Z3> 4.0
(2) 0.60 <| f2 | / fw <1.00
(3) 0.75 <1 / Z3 <0.90
However,
β2w: Lateral magnification at the wide-angle end of the second lens group β2t: Lateral magnification at the telephoto end of the second lens group β3w: Lateral magnification at the wide-angle end of the third lens group β3t: At the telephoto end of the third lens group Horizontal magnification f2: focal length fw of second lens group: focal length at the wide angle end of the objective optical system.

Therefore, in the real image type zoom finder and the image pickup apparatus of the present invention, a real image type zoom finder having a zoom ratio of 4 times or more, a small size, and good optical properties can be realized. For this reason, it is possible to reduce the size of an imaging apparatus including a variable focal length lens having a zoom ratio of 4 times or more. Further, since the third lens group satisfies the conditional expression (3) 0.75 <1 / Z3 <0.90, various aberrations can be favorably corrected while realizing a reduction in size of the finder.

In the inventions described in claims 2 and 7 , since the second lens group is composed of a single plastic lens, it is possible to further reduce the size of the finder in the optical axis direction, It can be configured at low cost.

In the inventions described in claims 3 and 8 , since both the object side and the observer side of the single plastic lens constituting the second lens group are aspherical, the aspherical surface is formed. In addition to being easy, by selecting these aspherical shapes, various aberrations can be corrected well while realizing a high zoom ratio of the finder.

In the inventions described in claims 4 and 9 , since the four lens groups of the first lens group to the fourth lens group are each composed of one plastic lens, further in the optical axis direction of the finder. Can be realized at a lower cost, and can be configured at a lower cost.

In the invention described in claims 5 and 10 , since at least two of the surfaces of the plastic lens are aspherical, it is easy to form an aspherical surface, and these aspherical surfaces By selecting the shape, various aberrations can be favorably corrected while realizing a high zoom ratio of the finder.

The best mode for carrying out the real image type variable magnification finder and imaging apparatus of the present invention will be described below with reference to the accompanying drawings.

  1 to 4 show a first embodiment (numerical example 1) of the real image type zoom finder of the present invention, and FIGS. 5 to 8 show a second embodiment (numerical value) of the real image type zoom finder of the present invention. 9 to 12 show a third embodiment (numerical example 3) of the real image type variable magnification finder of the present invention, and FIGS. 13 to 16 show a fourth embodiment of the real image type variable magnification finder of the present invention. Embodiment (Numerical Example 4) and FIGS. 17 to 20 show the fifth embodiment (Numerical Example 5) of the real image type variable magnification finder of the present invention, respectively.

  As shown in FIGS. 1, 5, 9, 13, and 17, each embodiment of the real image variable magnification finder according to the present invention includes, in order from the object side, an objective optical system Go having a positive refractive power; It is composed of a reversal optical system Gr for making an inverted image formed by the objective optical system an erect image, and an eyepiece optical system Ge having a positive refractive power for observing the erect image. 1, 5, 9, 13, and 17, the upper stage shows the wide-angle end state, the middle stage shows the intermediate focus state, and the lower stage shows the telephoto end state.

  In each of the above embodiments, the objective optical system Go includes a first lens group G1 having a positive refractive power composed of one convex lens, and a second lens group G2 having a negative refractive power composed of one concave lens. A third lens group G3 having a positive refractive power composed of one convex lens and a fourth lens group G4 having a positive refractive power composed of one convex lens, and the second lens group G2 and the third lens The group G3 is moved on the optical axis to perform zooming and correction of diopter change associated therewith. The first lens group G1 and the fourth lens group G4 are fixed during zooming.

  The second lens group G2 of the objective optical system Go is set so as to satisfy the following conditional expressions (1) and (2) with Z2 = β2t / β2w and Z3 = β3t / β3w. Real image type variable magnification viewfinder with high magnification exceeding 4x while having good optical performance.

(1) Z2 · Z3> 4.0
(2) 0.60 <| f2 | / fw <1.00
However,
β2w: Lateral magnification at the wide-angle end of the second lens group β2t: Lateral magnification at the telephoto end of the second lens group β3w: Lateral magnification at the wide-angle end of the third lens group β3t: At the telephoto end of the third lens group Horizontal magnification f2: focal length fw of second lens group: focal length at the wide angle end of the objective optical system.

  Conditional expression (1) sets the composite ratio of the lateral magnifications at the wide-angle end and the telephoto end of the second lens group G2 and the third lens group G3 that act on zooming. This conditional expression (1) is By satisfying this, it is possible to provide a real image type zoom finder having a high zoom ratio exceeding 4 times.

  Conditional expression (2) sets the ratio of the focal length of the second lens group G2 to the focal length at the wide-angle end of the objective optical system Go, and restricts the refractive power of the second lens group G2. If the upper limit of conditional expression (2) is not satisfied, the refractive power of the second lens group G2 responsible for zooming will become small. Although it works advantageously in correcting aberrations, in order to obtain a zoom ratio exceeding 4 times, the movement amount of the second lens group G2 must be increased, and the total length becomes longer. On the other hand, if the lower limit of conditional expression (2) is not reached, the refractive power of the second lens group G2 responsible for zooming will increase, making it difficult to correct off-axis aberrations, particularly coma and curvature of field. In addition, it becomes difficult to suppress negative distortion at the wide-angle end.

  Moreover, it is desirable to satisfy the following conditional expression (3).

(3) 0.75 <1 / Z3 <0.90
Conditional expression (3) sets the ratio of the lateral magnification at the wide-angle end and the telephoto end of the third lens group G3, and restricts the sharing ratio of the multiplication action. If the upper limit of conditional expression (3) is exceeded, it will be difficult to correct off-axis aberrations, particularly coma and curvature of field. If the lower limit of conditional expression (3) is not satisfied, the overall length becomes long and miniaturization cannot be achieved.

  In addition, since the second lens group G2 is composed of a single plastic lens, the overall length can be reduced and the size can be reduced, and the number of parts can be reduced, which is advantageous in terms of cost. . Furthermore, by forming the lens with a plastic lens, it becomes easy to form both the object side and the viewer side with aspherical surfaces, thereby facilitating correction of various aberrations.

  Furthermore, by configuring all the lens groups from the first lens group G1 to the fourth lens group G4 with a single plastic lens, it is possible to achieve further downsizing and cost reduction, as well as desired. These two or more surfaces can be easily formed as aspherical surfaces, thereby making it easier to correct various aberrations.

  FIG. 21 shows an example 10 of a specific application example of the real image type variable magnification finder according to the present invention. The viewfinder 10 is configured by arranging an objective optical system Go, a reversal optical system Gr, and an eyepiece optical system Ge in a substantially L-shaped housing 20 in a plan view, and an opening 21 on the front side of the housing 20. The first lens group G1 made of one plastic lens of the objective optical system Go faces forward. An eyepiece optical system Ge composed of a single lens faces rearward from the rear opening 22 of the housing 20. An inversion optical system Gr composed of two prisms P1 and P2 having a roof prism configuration is positioned between the objective optical system Go and the eyepiece optical system Ge, and the eyepiece optics from the first lens group G1 of the objective optical system Go. A crank-shaped optical path leading to the system Ge is formed, whereby further downsizing in the optical axis direction is achieved. A field frame FI is positioned on the intermediate image plane between the two prisms P1 and P2, thereby limiting the field of view of the finder 10. Of course, the specific structure of the finder according to the present invention is not limited to that shown in FIG.

  For example, by mounting the real image type zoom finder 10 as shown in FIG. 21 on an imaging apparatus having a variable focal length lens and a recording means for recording a subject image captured by the variable focal length lens, a variable focal length lens is provided. It is possible to make the zoom ratio of 4 or more. The recording means described above may be, for example, an electrical recording means for recording an electrical output generated in the solid-state imaging device on an electrical recording medium, or may be recorded as a chemical change on a silver salt film, for example. It may be a scientific recording means.

  Next, numerical examples in the respective embodiments of the real image type variable magnification finder of the present invention will be shown. The meanings of symbols used in each numerical example are as follows. In FIG. 1, FIG. 5, FIG. 9, FIG. 13 and FIG. 17, FI indicates a field frame inserted in an intermediate imaging plane located in the middle of the inverting optical system Gr, thereby limiting the field of view range. It is supposed to be. Ep indicates an eye point.

2ω: Diagonal angle of view Si: i-th surface Ri counted from the object side Ri: radius of curvature of the surface Si di: surface distance ni between the i-th surface and the (i + 1) -th surface from the object side : Refractive index νi at the d-line (wavelength 587.6 nm) of the i-th lens: Abbe number of the i-th lens *: Surface using an aspheric surface In each numerical example, several surfaces are configured by an aspheric surface. ing. Here, the aspherical shape is defined by Equation 1 where X is the depth of the aspherical surface and H is the height from the optical axis. A, B, C, and D are fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients, respectively.

  Table 1 shows specific numerical values of the optical system in the first embodiment shown in FIG.

  In Numerical Example 1, the second surface (the surface on the observer side of the first lens group G1 of the objective optical system Go), the third surface (the surface on the object side of the second lens group G2 of the objective optical system Go), the first surface 4 surfaces (surface on the observer side of the second lens group G2 of the objective optical system Go), 5th surface (surface on the object side of the third lens group G3 of the objective optical system Go), 7th surface (object optical system Go) Surface of the fourth lens group G4 on the object side), the eighth surface (the surface on the observer side of the fourth lens group G4 of the objective optical system Go), and the fifteenth surface (the surface on the observer side of the eyepiece optical system Ge). Is formed of an aspherical surface. Table 2 shows the aspheric coefficients of these surfaces.

  In the finder according to the first embodiment, the second lens group G2 and the third lens group G3 of the objective optical system Go are moved on the optical axis to correct the magnification change and the diopter change accompanying the magnification change. Accordingly, the surface intervals d2 (D2), d4 (D4), and d6 (D6) are variable. Therefore, Table 3 shows numerical values of the surface distances d2, d4, and d6 at the wide-angle end, the intermediate focal position, and the telephoto end in Numerical Example 1.

  FIG. 2 shows a spherical aberration diagram, an astigmatism diagram and a distortion aberration diagram at the wide-angle end, FIG. 3 at the intermediate focal position, and FIG. 4 at the telephoto end. In the spherical aberration diagram, the solid line indicates the value on the d line, the broken line indicates the value on the C line, and the alternate long and short dash line indicates the value on the F line. In the astigmatism diagram, the solid line indicates the value on the sagittal image plane and the broken line indicates the value on the tangential image plane. Is shown.

  Table 4 shows specific numerical values of the optical system in the second embodiment shown in FIG.

  In Numerical Example 2, the second surface (the surface on the observer side of the first lens group G1 of the objective optical system Go), the third surface (the surface on the object side of the second lens group G2 of the objective optical system Go), the first surface 4 surfaces (surface on the observer side of the second lens group G2 of the objective optical system Go), 5th surface (surface on the object side of the third lens group G3 of the objective optical system Go), 7th surface (object optical system Go) Surface of the fourth lens group G4 on the object side), the eighth surface (the surface on the observer side of the fourth lens group G4 of the objective optical system Go), and the fifteenth surface (the surface on the observer side of the eyepiece optical system Ge). Is formed of an aspherical surface. Table 5 shows the aspheric coefficients of these surfaces.

  In the viewfinder according to the second embodiment, the second lens group G2 and the third lens group G3 of the objective optical system Go are moved on the optical axis to correct the magnification change and the diopter change accompanying the magnification change. Accordingly, the surface intervals d2 (D2), d4 (D4), and d6 (D6) are variable. Therefore, Table 6 shows numerical values of the surface distances d2, d4, and d6 at the wide-angle end, the intermediate focal position, and the telephoto end in Numerical Example 2.

  FIG. 6 shows a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram at the wide-angle end, FIG. 7 at the intermediate focal position, and FIG. 8 at the telephoto end. In the spherical aberration diagram, the solid line indicates the value on the d line, the broken line indicates the value on the C line, and the alternate long and short dash line indicates the value on the F line. In the astigmatism diagram, the solid line indicates the value on the sagittal image plane and the broken line indicates the value on the tangential image plane. Is shown.

  Table 7 shows each numerical value of the optical system in the third embodiment shown in FIG.

  In Numerical Example 3, the second surface (the surface on the observer side of the first lens group G1 of the objective optical system Go), the third surface (the surface on the object side of the second lens group G2 of the objective optical system Go), the first surface 4 surfaces (surface on the observer side of the second lens group G2 of the objective optical system Go), 5th surface (surface on the object side of the third lens group G3 of the objective optical system Go), 7th surface (object optical system Go) Surface of the fourth lens group G4 on the object side), the eighth surface (the surface on the observer side of the fourth lens group G4 of the objective optical system Go), and the fifteenth surface (the surface on the observer side of the eyepiece optical system Ge). Is formed of an aspherical surface. Table 8 shows the aspheric coefficients of these surfaces.

  In the finder according to the third embodiment, the second lens group G2 and the third lens group G3 of the objective optical system Go are moved on the optical axis to correct magnification change and diopter change accompanying magnification change. Accordingly, the surface intervals d2 (D2), d4 (D4), and d6 (D6) are variable. Accordingly, Table 9 shows numerical values of the surface intervals d2, d4, and d6 at the wide-angle end, the intermediate focal position, and the telephoto end in Numerical Example 3.

  FIG. 10 shows a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram at the wide-angle end, FIG. 11 at the intermediate focal position, and FIG. 12 at the telephoto end. In the spherical aberration diagram, the solid line indicates the value on the d line, the broken line indicates the value on the C line, and the alternate long and short dash line indicates the value on the F line. In the astigmatism diagram, the solid line indicates the value on the sagittal image plane and the broken line indicates the value on the tangential image plane. Is shown.

  Table 10 shows specific numerical values of the optical system in the fourth embodiment shown in FIG.

  In Numerical Example 4, the second surface (the surface on the observer side of the first lens group G1 of the objective optical system Go), the third surface (the surface on the object side of the second lens group G2 of the objective optical system Go), the first surface 4 surfaces (surface on the observer side of the second lens group G2 of the objective optical system Go), 5th surface (surface on the object side of the third lens group G3 of the objective optical system Go), 7th surface (object optical system Go) Surface of the fourth lens group G4 on the object side), the eighth surface (the surface on the observer side of the fourth lens group G4 of the objective optical system Go), and the fifteenth surface (the surface on the observer side of the eyepiece optical system Ge). Is formed of an aspherical surface. Table 11 shows the aspheric coefficients of these surfaces.

  In the viewfinder according to the fourth embodiment, the second lens group G2 and the third lens group G3 of the objective optical system Go are moved on the optical axis to correct magnification change and diopter change accompanying magnification change. Accordingly, the surface intervals d2 (D2), d4 (D4), and d6 (D6) are variable. Therefore, Table 12 shows numerical values of the surface distances d2, d4, and d6 at the wide-angle end, the intermediate focal position, and the telephoto end in Numerical Example 4.

  14 shows a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram at the wide angle end, FIG. 15 at the intermediate focal position, and FIG. 16 at the telephoto end. In the spherical aberration diagram, the solid line indicates the value on the d line, the broken line indicates the value on the C line, and the alternate long and short dash line indicates the value on the F line. In the astigmatism diagram, the solid line indicates the value on the sagittal image plane and the broken line indicates the value on the tangential image plane. Is shown.

  Table 13 shows specific numerical values of the optical system according to the fifth embodiment shown in FIG.

  In Numerical Example 5, the second surface (the surface on the observer side of the first lens group G1 of the objective optical system Go), the third surface (the surface on the object side of the second lens group G2 of the objective optical system Go), the first surface 4 surfaces (surface on the observer side of the second lens group G2 of the objective optical system Go), 5th surface (surface on the object side of the third lens group G3 of the objective optical system Go), 7th surface (object optical system Go) Surface of the fourth lens group G4 on the object side), the eighth surface (the surface on the observer side of the fourth lens group G4 of the objective optical system Go), and the fifteenth surface (the surface on the observer side of the eyepiece optical system Ge). Is formed of an aspherical surface. Table 14 shows the aspheric coefficients of these surfaces.

  In the finder according to the fifth embodiment, the second lens group G2 and the third lens group G3 of the objective optical system Go are moved on the optical axis to correct magnification change and diopter change accompanying magnification change. Accordingly, the surface intervals d2 (D2), d4 (D4), and d6 (D6) are variable. Therefore, Table 15 shows numerical values of the surface intervals d2, d4, and d6 at the wide-angle end, the intermediate focal position, and the telephoto end in Numerical Example 5.

  18 shows a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram at the wide-angle end, FIG. 19 at the intermediate focal position, and FIG. 20 at the telephoto end. In the spherical aberration diagram, the solid line indicates the value on the d line, the broken line indicates the value on the C line, and the alternate long and short dash line indicates the value on the F line. In the astigmatism diagram, the solid line indicates the value on the sagittal image plane and the broken line indicates the value on the tangential image plane. Is shown.

  Table 16 shows numerical data of the conditional expressions (1), (2), and (3) in the numerical examples described above.

  As described above, according to the present invention, there are provided a real image type zoom finder having good optical performance, a short lens total length and a high zoom ratio exceeding 4 times, and the real image type zoom finder. An imaging device provided can be obtained.

  It should be noted that the specific shapes, configurations, and numerical values shown in the respective embodiments and numerical examples described above are merely examples of the implementation performed in the practice of the present invention, and as a result, the present invention. The technical scope should not be interpreted in a limited way.

  It is suitable for use as a camera finder equipped with a zoom lens having a high zoom ratio of 4 times or more and requiring miniaturization.

2 to 4 show a first embodiment of the real image type variable magnification finder of the present invention, and this figure shows a configuration of an optical system. FIG. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in a wide angle end. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in an intermediate focus position. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in a telephoto end. 6 to 8 show a second embodiment of the real image type variable magnification finder of the present invention, and this figure shows a configuration of an optical system. FIG. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in a wide angle end. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in an intermediate focus position. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in a telephoto end. FIG. 10 to FIG. 12 show a third embodiment of the real image type variable magnification finder of the present invention, and this figure shows a configuration of an optical system. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in a wide angle end. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in an intermediate focus position. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in a telephoto end. FIGS. 14 to 16 show a fourth embodiment of the real image type variable magnification finder according to the present invention, and FIG. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in a wide angle end. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in an intermediate focus position. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in a telephoto end. FIG. 18 shows a fifth embodiment of the real image type variable magnification finder according to the present invention together with FIG. 18 to FIG. 19, and this figure shows a configuration of an optical system. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in a wide angle end. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in an intermediate focus position. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in a telephoto end. It is a partially cutaway perspective view showing a specific application example of the real image type variable magnification finder according to the present invention.

Explanation of symbols

  Go ... objective optical system, Gr ... reversal optical system, Ge ... eyepiece optical system, G1 ... first lens group, G2 ... second lens group, G3 ... third lens group, G4 ... fourth lens group

Claims (10)

In order from the object side, an objective optical system having a positive refractive power, a reversal optical system for converting an inverted image formed by the objective optical system into an erect image, and a positive refraction for observing the erect image The objective optical system includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive lens. In the real image type variable magnification finder, which is composed of a fourth lens group having refractive power and moves the second lens group and the third lens group on the optical axis to correct magnification change and diopter change accompanying magnification change, Z2 = A real-image magnification finder that satisfies the following conditional expressions (1), (2) , and (3) as β2t / β2w and Z3 = β3t / β3w.
(1) Z2 · Z3> 4.0
(2) 0.60 <| f2 | / fw <1.00
(3) 0.75 <1 / Z3 <0.90
However,
β2w: Lateral magnification at the wide-angle end of the second lens group β2t: Lateral magnification at the telephoto end of the second lens group β3w: Lateral magnification at the wide-angle end of the third lens group β3t: At the telephoto end of the third lens group Horizontal magnification f2: focal length fw of second lens group: focal length at the wide angle end of the objective optical system. The real image type zoom finder according to claim 1, wherein the second lens group includes a single plastic lens. The real image type variable magnification finder according to claim 2 , wherein both the object side and the observer side of one plastic lens constituting the second lens group are aspherical surfaces. 4. The real image type zoom finder according to claim 1, wherein each of the four lens groups of the first lens group to the fourth lens group includes one plastic lens. The real image type zoom finder according to claim 4 , wherein at least two of the surfaces of the plastic lens are aspherical. A variable focal length lens, a recording means for recording a subject image captured by the variable focal length lens, and a real image in which a viewing angle is changed according to an angle of view that changes with a change in the focal length of the variable focal length lens. An imaging apparatus equipped with a variable magnification finder,
The real image type variable magnification finder includes, in order from the object side, an objective optical system having a positive refractive power, an inversion optical system for converting an inverted image formed by the objective optical system into an erect image, and the erect image. The objective optical system includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a positive refractive power. A third lens group having a positive refractive power and a fourth lens group having a positive refractive power, and moving the second lens group and the third lens group on the optical axis to correct magnification change and diopter change accompanying magnification change. , Z2 = β2t / β2w, Z3 = β3t / β3w, and satisfy the following conditional expressions (1), (2) , (3):
(1) Z2 · Z3> 4.0
(2) 0.60 <| f2 | / fw <1.00
(3) 0.75 <1 / Z3 <0.90
However,
β2w: Lateral magnification at the wide-angle end of the second lens group β2t: Lateral magnification at the telephoto end of the second lens group β3w: Lateral magnification at the wide-angle end of the third lens group β3t: At the telephoto end of the third lens group Horizontal magnification f2: focal length fw of second lens group: focal length at the wide angle end of the objective optical system. The imaging apparatus according to claim 6 , wherein the second lens group includes one plastic lens. The imaging apparatus according to claim 7 , wherein both the object side and the observer side of one plastic lens constituting the second lens group are aspherical surfaces. The imaging device according to claim 6 , wherein the four lens groups of the first lens group to the fourth lens group are each composed of a single plastic lens. The imaging apparatus according to claim 9 , wherein at least two of the surfaces of the plastic lens are aspherical.

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