JP2004240420A - Electronic imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic imaging apparatus which can adjust a sufficiently wide range of light quantity even by an extremely thin type in a depth direction. <P>SOLUTION: The electronic imaging apparatus is composed by using optical systems G1, G2, G3, G4, and G5 having at least one reflection surface RF for bending an optical path. Also, the electronic imaging apparatus is provided with optical elements which can change the transmittance of light in the optical systems and is so constituted that the optical path passes the optical elements a plurality of times. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

The present invention relates to an electronic imaging apparatus that adjusts a light amount by a method of changing an internal transmittance of an optical system.

In electronic imaging devices such as recent digital cameras, miniaturization and thinning have been progressing. This reduction in size and thickness is largely due to the reduction in size of electric circuits and recording media. As a result of miniaturization of electric circuits and recording media, the ratio of the size of an optical system to the entire image pickup apparatus has been relatively increasing. Therefore, the miniaturization of the optical system, particularly the zoom lens, has been promoted through the miniaturization of the image sensor. For example, the use of a retractable lens barrel can be mentioned. The collapsible lens barrel has a structure in which the optical system protrudes during photographing, and the optical system is housed in the housing of the electronic imaging device when the camera is carried. This has responded to miniaturization or thinning.
However, as miniaturization progresses, there is a limit to miniaturization of the entire optical system in proportion to progress of miniaturization of the imaging device. This is because there is a limit in the physical processing of the lens element constituting the optical system, a limit in the mechanical strength of the mechanical mechanism, and a limit in the manufacturing accuracy. Therefore, the use of an aspherical surface or a high-refractive-index, low-dispersion glass material has reduced the number of components to the limit. However, this also has reached the upper limit of securing the basic specifications and aberration correction. Therefore, in the conventional configuration in which the optical elements are arranged in a straight line, the reduction of the volume and the total length of the optical system, or the reduction in the depth direction at the time of collapsing has reached the limit.
Therefore, there are the following methods for achieving a reduction in thickness particularly in the depth direction. One is a configuration having a reflection surface for bending an optical path in an optical system. Another is a configuration using an electrochromic element instead of an optical filter or a dichroic mirror. In this configuration, there is a configuration in which a plurality of electrochromic elements having different wavelength ranges of a plurality of transmitted lights are combined (see Patent Documents 1 and 2). Such a configuration greatly contributes to a reduction in the thickness of the electronic imaging device housing.
Japanese Patent Publication No. 5-27083 JP-A-11-160739

  However, in these devices, with the miniaturization of the electronic image pickup device, the problem of diffraction cannot be ignored. For example, when the aperture is stopped down to F / 5.6 or more, the deterioration of the image quality becomes remarkable, so that a new problem such as a narrow adjustment range of the light amount has been emerging. Therefore, conventionally, a method of removing and replacing some optical elements in order to reduce the transmittance, and a method of using an optical element whose transmittance is variable have been proposed. However, in the former case, the mechanism is complicated, and the space therefor is a factor that hinders miniaturization. In this respect, the latter is suitable for miniaturization, but the variable range of the transmittance is narrow, and it is insufficient for adjusting the light amount in a wide range.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide an electronic imaging system capable of adjusting a light amount in a sufficiently wide range even in a very thin depth direction. It is to provide a device.

In order to achieve the above object, an electronic imaging device according to the present invention can change the light transmittance of the optical system in an electronic imaging device using an optical system having a reflection surface for bending an optical path. An optical element is provided, and the light beam passes through the optical element a plurality of times.
In the electronic imaging device according to the present invention, in an electronic imaging device using an optical system having a reflection surface for bending an optical path, light transmittance can be changed on the reflection surface or immediately before the reflection surface. An optical element is provided, and the light beam passes through the optical element a plurality of times.
Further, the electronic imaging device according to the present invention is configured such that the transmittance τ520 when light having a wavelength of 520 nm passes through the optical element once satisfies the following condition in the entire range of τmin ≦ τ520 ≦ τmax.
0.70 <τ440 / τ520 <1.20
0.80 <τ600 / τ520 <1.30
Here, τ440 is the transmittance of light having a wavelength of 440 nm and the transmittance of τ600 is light having a wavelength of 600 nm. Further, τmin is the minimum transmittance when the optical element capable of changing the transmittance is in the most opaque state, and τmax is the optical element capable of changing the transmittance is the most transparent. It is the maximum transmittance at the time of the state.

  ADVANTAGE OF THE INVENTION According to this invention, it is a small and thin electronic device in which the light intensity can be adjusted in a very thin depth direction and a sufficiently wide range by arranging a light beam to pass through an optical element whose transmittance can be changed a plurality of times. An imaging device can be provided.

Hereinafter, embodiments of the present invention will be described with reference to the illustrated embodiments. Prior to the description, the operation and effect of the present invention will be described.
According to the present invention, an image forming light beam passes through an optical element capable of changing the transmittance (hereinafter, referred to as a variable transmittance optical element) twice, for example, twice by utilizing a reflection surface in an optical system. You can make it. Thus, even if the variable range of the transmittance of the variable transmittance optical element is narrow, the ratio of the maximum value and the minimum value of the transmittance of the entire optical system becomes approximately the square, and the light amount adjustment range can be greatly expanded. .
In order to allow the imaging light beam to pass through the variable transmittance optical element twice, it is advantageous to arrange the variable transmittance optical element on or immediately before the reflection surface as much as possible in order to reduce the size of the optical system. It is.
Further, it is preferable that the spectral transmittance τ520 when light having a wavelength of 520 nm passes through the transmittance variable optical element once satisfy the following conditions in the entire range of τmin ≦ τ520 ≦ τmax.
0.70 <τ440 / τ520 <1.20 (1)
0.80 <τ600 / τ520 <1.30 (2)
Here, τx (x is a number) is the transmittance of light having a wavelength of xnm. (Thus, τ440 is the transmittance of light with a wavelength of 440 nm and τ600 is the transmittance of light with a wavelength of 600 nm.) Τmin is the minimum transmittance when the transmittance variable optical element is in the most opaque state. , Τmax are the maximum transmittances when the transmittance variable optical element is in the most transparent state.
If any of the above conditions is not satisfied, the color balance tends to deteriorate, which is not preferable.

In addition,
0.75 <τ440 / τ520 <1.15 (1 ′)
0.85 <τ600 / τ520 <1.25 (2 ')
Even better if you meet the following conditions,
0.80 <τ440 / τ520 <1.10 (1 ")
0.90 <τ600 / τ520 <1.20 (2 ")
It is best if certain conditions are satisfied.

Although the above description relates to the case where the variable transmittance optical element is used, an optical element whose reflectance is variable (hereinafter, referred to as a variable reflectance optical element) may be used instead. Also in this case, it is preferable that the reflectance R520 for light having a wavelength of 520 nm satisfy the following condition in the entire range of Rmin ≦ R520 ≦ Rmax.
0.50 <R440 / R520 <1.40 (3)
0.60 <R600 / R520 <1.70 (4)
Here, Rx (x is a number) is the reflectance of light having a wavelength of x nm. (Therefore, R440 is the reflectance of light having a wavelength of 440 nm, and R600 is the reflectance of light having a wavelength of 600 nm.) Rmin is the minimum reflection when the variable reflectance optical element is in the most transparent state. The rate, Rmax, is the maximum reflectance when the variable reflectance optical element is in the most opaque state.
Also in this case, if any of the conditional expressions (3) and (4) is not satisfied, the color balance tends to deteriorate, which is not preferable.

In addition,
0.60 <R440 / R520 <1.30 (3 ')
0.70 <R600 / R520 <1.60 (4 ')
Even better if you meet the following conditions,
0.70 <R440 / R520 <1.20 (3 ")
0.80 <R600 / R520 <1.50 (4 ")
It is best if certain conditions are satisfied.

Here, τmin and τmax will be described. For example, when two different predetermined voltages are applied to the electrochromic element, a state of high transmittance and a state of low transmittance are obtained as shown in FIG. Here, in the state where the transmittance is highest, the electrochromic element is the most transparent state. On the other hand, when the transmittance is the lowest, the electrochromic element is the most opaque.
Therefore, τmin is the minimum transmittance when the variable transmittance optical element is in the most opaque state, and τmax is the maximum transmittance when the variable transmittance optical element is in the most transparent state. It turns out that.
For example, when τmin ≦ τ520 ≦ τmax, τmin is the minimum transmittance at a wavelength of 520 nm when the transmittance variable optical element is in the most opaque state. Further, τmax is the maximum transmittance at a wavelength of 520 nm when the transmittance variable optical element is in the most transparent state.
Further, as shown in FIG. 5, in the variable reflectivity optical element, by applying two different predetermined voltages, a state of high reflectivity and a state of low reflectivity are obtained. Here, when the reflectivity is highest, the variable reflectivity optical element is in the most opaque state. However, light is reflected because almost no absorption occurs. On the other hand, in the state where the reflectance is the lowest, the variable reflectance optical element is the most transparent state.
Therefore, Rmin is the minimum reflectance when the variable reflectance optical element is in the most transparent state, and Rmax is the maximum reflectance when the variable reflectance optical element is in the most opaque state. It turns out that.

As the variable transmittance optical element, for example, an electrochromic element is preferable. This element can change the transmittance or the reflectance of light by electrically controlling a chemical change. Use of such an element is preferable in terms of size, controllability, response speed, and the like. In particular, such an element can obtain a stable transmittance with high-speed tracking. Therefore, if such an element is provided in the optical path, for example, by controlling the amount of electricity under a certain voltage, the light amount can be rapidly and stably adjusted. The variable reflectance optical element includes, for example, a dimming mirror using a magnesium or nickel alloy thin film.
In this case, in order to widen the light amount adjustment range as much as possible, the ratio between the maximum transmittance τmax (≧ 0.7) and the minimum transmittance τmin (≦ 0.3) of the variable transmittance optical element in one pass of light having a wavelength of 520 nm is used. Is preferably at least 2.5 or more. Preferably, it is 3.5 or more. In the case of reflection, it is desirable that it is at least 4 or more, preferably 5.5 or more.

The following imaging optical system as an optical system is extremely effective in reducing the depth direction of an electronic imaging device, and therefore, the smaller the electronic imaging device becomes, the more effective it becomes. This imaging optical system has at least a reflecting surface and a lens group having a positive refractive power. Here, the reflecting surface is used to bend the optical path. Further, the lens unit having a positive refractive power monotonously moves to the object side when zooming from the wide-angle end to the telephoto end.
In such an optical system, even if the aperture stop is set to, for example, about F8, which is commonly used, the image quality deteriorates due to the influence of diffraction, so that the aperture diameter cannot be reduced to a small value. Therefore, if the above-described combination of the variable transmittance optical element and the reflective surface or the variable reflectance optical element is used, the light amount can be adjusted without deteriorating the image quality. In order to make the depth direction thinner, it is preferable that at least one reflecting surface be provided on the object side of the most object side lens of all the groups movable during zooming.

  Alternatively, at least one prism is arranged in the optical system. Then, the reflecting surface is arranged substantially parallel to one surface of the prism. Furthermore, a medium capable of changing the light transmittance (hereinafter, referred to as a variable transmittance medium) may be arranged between one surface of the prism and the reflection surface. In this case, the prism, the variable transmittance medium, and the reflection surface correspond to the variable transmittance optical element. It is more preferable that a prism be arranged closest to the object side of the optical path passing through the optical system. This is because the use of a medium having a high refractive power in the depth direction is effective for achieving a longer optical path length, that is, a shorter actual size.

  Further, the most object side surface (incident surface) of the prism is preferably a concave surface. The reason is that by making the depth (distance) from the entrance surface of the entire optical system to the entrance pupil position as small as possible, the reflecting surface can be physically arranged closer to the entrance surface of the entire optical system. This is effective in reducing the depth. The refractive index of the prism should be as high as 1.55 or more (better if 1.65 or more, best if 1.75 or more).

  In addition to the above, increasing the refractive index of the prism has the following effects. Some of the transmittance variable media or the transparent electrodes have an extremely high refractive index higher than that of ordinary glass. Here, it is assumed that a variable transmittance medium is interposed between the prism and the reflection surface without passing through air. In this case, the interface between the prism and the transmittance variable medium has a high reflectance. As a result, a part of the image forming light beam that should be reflected on the reflecting surface is reflected on the boundary surface to form a ghost image. Therefore, the difference in refractive index between the prism and the transmittance variable medium is preferably set to 0.4 or less (better if 0.3 or less, better if 0.2 or less). As described above, by increasing the refractive index of the prism, an effect that ghost can be suppressed can be obtained.

Alternatively, when the refractive index of the prism is not a condition, the relationship between the reflectance Rb at the boundary surface, the reflectance Rm at the reflection surface, and the distance d between both surfaces for light having a wavelength of 520 nm may be as follows.
0.1 <Rb / {(1−Rb) (Rm × τ520 ² )} <10
d = Pixel pitch x α / cos θ
0 <α <1.0 (α ... coefficient)
20 ° <θ <70 ° (θ: angle of the reflecting surface with respect to the incident optical axis)
The above conditions are conditions in a case where a double image caused by reflection on each side is used for a reverse hand. That is, the double image is used to eliminate aliasing distortion due to a component of the electronic imaging element that is higher than the Nyquist frequency. This uses a double image to add the effect of an optical low-pass filter. If these conditions are removed, the resolving power is excessively lowered or an image recognized as a ghost is formed, which is not preferable.

  Note that the focusing function is preferably provided in an optical element group as close to the image side of the optical system as possible. In the case of the present invention, the movable group closest to the image fulfills the focusing function. Then, it is preferable that the electronic imaging apparatus includes a means for electrically controlling the state of the optical system, the electric signal related to the image obtained from the electronic imaging element, and the transmittance of the transmittance variable medium.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 and 2 are a first embodiment of an electronic imaging apparatus, and are cross-sectional views along an optical axis showing an optical configuration used in the electronic imaging apparatus. These figures respectively show the states when focusing on an object point at infinity at the wide angle end. This optical system is a bending optical system.
1 and 2, I denotes an image pickup surface of a CCD which is an electronic image pickup device, and LPF denotes an optical low-pass filter. The optical system, the optical low-pass filter LPF, and the imaging plane I are arranged in this order from the object side.
The optical system includes, in order from the object side, a first lens group G1, a second lens group G2, an aperture stop S, a third lens group G3, a fourth lens group G4, and a fifth lens group G5. ing.
The first lens group G1 has a positive refractive power as a whole. The first lens group G1 includes, in order from the object side, a prism P and a rear sub-group. The prism P has a reflecting surface RF for bending the optical path toward the object side and a light incident surface IF. The light incident surface IF has a concave surface on the object side and has an aspheric surface whose divergence decreases as the distance from the optical axis increases. The rear sub-group has a positive refractive power.
In addition, a medium whose reflectivity is variable is adhered to the reflection surface RF of the prism P shown in FIG. On the other hand, a transmittance variable medium is interposed between the reflection surface RF shown in FIG. These constitute a variable reflectance optical element or a variable transmittance optical element. 1 and 2, the light amount can be adjusted at high speed and stably.
In the configuration of FIG. 2, the light incident on the prism P passes through the transmittance variable medium and reaches the reflection surface RF. This light is reflected by the reflection surface RF and then returns to the prism P through the variable transmittance medium again. That is, the light incident on the prism P passes through the variable transmittance medium twice. Therefore, the configuration of FIG. 2 can have a wider light amount adjustment range than the configuration of FIG.
Here, the prism P is configured as a reflection prism that bends the optical path by 90 degrees. In addition, the rear sub-unit includes a biconvex positive lens.
The second lens group G2 has a negative refractive power as a whole. The second lens group G2 is composed of a biconcave negative lens and a positive meniscus lens arranged in order from the object side.
The third lens group G3 includes, in order from the object side, a biconvex positive lens, and a cemented lens of a biconvex positive lens and a biconcave negative / positive lens.
The fourth lens group G4 includes a positive meniscus lens.
The fifth lens group G5 includes a plano-convex lens having a convex surface facing the object side.
Note that the aspect ratio of the effective imaging area in each embodiment of the present invention is 3: 4, and the optical path bending direction is the horizontal direction.

When zooming from the wide-angle end to the telephoto end in a state in which the zoom lens is focused on an object point at infinity, the positions of the first lens group G1 and the aperture stop S are fixed, and the second lens group G2 is moved toward the image side. Only, and the third lens group G3 moves only to the object side.
During the focusing operation, the fourth lens group G4 and the fifth lens group G5 move on the optical axis.
The aspheric surface includes, in addition to the light incident surface IF of the prism P in the first lens group G1, the object side surface of the biconvex lens in the first lens group G1, the object side of the biconcave lens in the second lens group G2, and The image side surface, the object side surface and the image side surface of the biconvex positive lens in the third lens group G3, and the object side surface of the meniscus lens of the fifth lens group G5 are respectively provided.

Next, numerical data of optical members constituting the optical system used in the first embodiment will be described.
In the numerical data of the optical system used in the first embodiment, r ₁ , r ₂ ,... Indicate the radius of curvature of each lens surface, d ₁ , d _{2 ,.} n _d2 ,... are the refractive indices of each lens at the d-line, v _d1 , v _d2 ,. Represents the F number, f represents the focal length of the entire system, and D0 represents the distance from the object to the first surface. The unit of r, d, f, D0 is mm.
The aspheric surface shape is represented by the following equation, where z is the optical axis direction, y is the direction orthogonal to the optical axis, K is the cone coefficient, and A ₄ , A ₆ , A ₈ , and A ₁₀ are the aspheric coefficients. Is represented by
^{z = (y 2 / r)} / [1+ {1- (1 + K) (y / r) 2} 1/2]
^{_{+ A 4 y 4 + A 6}} y 6 + A 8 y 8 + A 10 y 10
These symbols are common to the numerical data of the embodiments described later.

Numeric data 1
r ₁ = -9.4520 (aspherical surface)
d ₁ = 8.2000 n _d1 = 1.80518 ν _d1 = 25.42
r ₂ = ∞
d ₂ = 0.1500
r ₃ = 9.6078 (aspherical surface)
_{d 3 = 2.3000 n d3 = 1.78800} ν d3 = 47.37
r ₄ = -36.5601
d ₄ = D4
r ₅ = -12.2968 (aspherical surface)
d ₅ = 0.8000 n _d5 = 1.74320 ν _d5 = 49.34
r ₆ = 5.0653 (aspherical surface)
d ₆ = 0.6000
r ₇ = 7.3064
d ₇ = 1.5000 n _d7 = 1.84666 ν _d7 = 23.78
r ₈ = 30.2966
d ₈ = D8
r ₉ = ∞ (aperture)
d ₉ = D9
r ₁₀ = 10.4103 (aspherical surface)
_{d 10 = 5.8865 n d10 = 1.69350} ν d10 = 53.21
r ₁₁ = -6.9390 (aspherical surface)
d ₁₁ = 0.1500
r ₁₂ = 8.4519
d ₁₂ = 2.4987 n _d12 = 1.51742 ν _d12 = 52.43
r ₁₃ = -10.7434
d ₁₃ = 0.7000 n _d13 = 1.84666 ν _d13 = 23.78
r ₁₄ = 4.1500
d ₁₄ = D14
r ₁₅ = 6.0955
d ₁₅ = 1.8000 n _d15 = 1.48749 ν _d15 = 70.23
r ₁₆ = 9.7078
d ₁₆ = D16
r ₁₇ = 8.7554 (aspherical surface)
d ₁₇ = 1.8000 n _d17 = 1.58423 ν _d17 = 30.49
r ₁₈ = ∞
d ₁₈ = 0.7000
r ₁₉ = ∞
d ₁₉ = 0.6000 n _d19 = 1.51633 ν _d18 = 64.14
r ₂₀ = ∞
d ₂₀ = D20
r ₂₁ = ∞ (imaging plane)

Aspheric coefficient first surface K = 0
A ₂ = 0 A ₄ = 9.5837 × 10 ^-4 A ₆ = -1.1998 × 10 ^-5
A ₈ = 1.1926 × 10 ^-7
Third surface K = 0
A ₂ = 0 A ₄ = -5.2184 × 10 ^-4 A ₆ = 1.4369 × 10 ^-6
A ₈ = 1.3193 × 10 ^-8
Fifth surface K = 0
A ₂ = 0 A ₄ = -8.5131 × 10 ^-4 A ₆ = 1.2914 × 10 ^-4
A ₈ = -5.4974 × 10 ^-6
6th surface K = 0
A ₂ = 0 A ₄ = -1.8812 × 10 ^-3 A ₆ = 1.7977 × 10 ^-4
A ₈ = -1.1418 × 10 ^-5
10th surface K = 0
A ₂ = 0 A ₄ = -9.0524 × 10 ^-4 A ₆ = -1.4899 × 10 ^-5
A ₈ = -2.7354 × 10 ^-6
11th surface K = 0
A ₂ = 0 A ₄ = 2.0252 × 10 ^-4 A ₆ = -1.5683 × 10 ^-5
A ₈ = -2.5889 × 10 ^-7
17th surface K = 0
A ₂ = 0 A ₄ = 1.3132 × 10 ^-4 A ₆ = 2.2399 × 10 ^-5
A ₈ = -2.5971 × 10 ^-6

When the zoom data D0 (distance from the object to the first surface) is ∞
Wide-angle end Middle telephoto end f (mm) 4.60394 7.80037 13.19942
Fno. 2.8634 3.5902 4.5306
D0 ∞ ∞ ∞
D4 0.99877 3.91855 6.57280
D8 6.47386 3.54652 0.89974
D9 5.54148 3.31646 0.99874
D14 1.37738 3.62339 5.91816
D16 1.19791 1.19758 1.19992
D20 0.89970 0.87855 0.89957

3 and 4 show a second embodiment of the electronic imaging apparatus, and are cross-sectional views along an optical axis showing an optical configuration used in the electronic imaging apparatus. These figures respectively show the states when focusing on an object point at infinity at the wide angle end. This optical system is also a bending optical system.
3 and 4, I denotes an image pickup surface of a CCD which is an electronic image pickup device, and LPF denotes an optical low-pass filter. The optical system, the optical low-pass filter LPF, and the imaging plane I are arranged in this order from the object side.
The optical system includes, in order from the object side, a first lens group G1, a second lens group G2, an aperture stop S, a third lens group G3, a fourth lens group G4, and a fifth lens group G5. ing.
The first lens group G1 has a negative refractive power as a whole. The first lens group G1 includes, in order from the object side, a negative meniscus lens, a prism P, and a rear sub-group. The prism P has a reflection surface RF that bends the optical path to the object side. The rear subgroup has negative refractive power.
Note that a medium having a variable reflectivity is adhered to the reflection surface RF of the prism P shown in FIG. In addition, a variable transmittance medium is interposed between the reflection surface RF shown in FIG. These constitute a variable reflectance optical element or a variable transmittance optical element.
The prism P is configured as a reflection prism that bends the optical path by 90 degrees. The rear sub-unit includes a biconcave negative lens.
The second lens group G2 includes a positive meniscus lens.
The third lens group G3 includes, in order from the object side, a cemented lens formed by joining a positive meniscus lens and a negative meniscus lens, and a biconvex positive lens.
The fourth lens group G4 includes a positive meniscus lens.
The fifth lens group G5 includes, in order from the object, a cemented lens formed by joining a negative meniscus lens and a positive meniscus lens, a plane parallel plate, and an optical low-pass filter LPF.

When zooming from the wide-angle end to the telephoto end in a state in which the zoom lens is focused on an object point at infinity, the positions of the first lens group G1 and the aperture stop S are fixed, and the second lens group G2 is moved toward the image side. Only to move.
During the focusing operation, the fourth lens group G4 and the fifth lens group G5 move on the optical axis.
The aspheric surface includes, in addition to the entrance surface and the exit surface of the rear sub-group lens in the first lens group G1, the most object side surface of the third lens group G3, and the image of the cemented lens in the fifth lens group G5. Each is provided on the side surface.
In the present embodiment, as a modified example, instead of the positive meniscus lens and the prism P closest to the object side in the first lens group G1, the entrance surface as shown in the first embodiment has the concave surface facing the object side. It can be configured using a prism.

Next, numerical data of optical members constituting the optical system according to the second embodiment will be described.
Numeric data 2
r ₁ = 18.1242
d ₁ = 1.1000 n _d1 = 1.77250 ν _d1 = 49.60
r ₂ = 11.0917
d ₂ = 3.0000
r ₃ = ∞
_{d 3 = 12.5000 n d3 = 1.80610} ν d3 = 40.92
r ₄ = ∞
d ₄ = 0.3000
r ₅ = -189.0024 (aspherical surface)
d ₅ = 0.9000 n _d5 = 1.80610 ν _d5 = 40.92
r ₆ = 7.0839 (aspheric surface)
d ₆ = 0.8000
r ₇ = 8.8339
d ₇ = 1.9000 n _d7 = 1.76182 ν _d7 = 26.52
r ₈ = 33.9090
d ₈ = D8
r ₉ = ∞ (aperture)
d ₉ = 1.0000
r ₁₀ = 6.5543 (aspherical surface)
_{d 10 = 2.5000 n d10 = 1.74320} ν d10 = 49.34
r ₁₁ = 16.5 000
d ₁₁ = 0.7000 n _d11 = 1.84666 ν _d11 = 23.78
r ₁₂ = 6.8813
d ₁₂ = 0.8000
r ₁₃ = 110.5063
d ₁₃ = 1.5000 n _d13 = 1.72916 v _d13 = 54.68
r ₁₄ = -13.4784
d ₁₄ = D14
r ₁₅ = 17.0895
d ₁₅ = 1.4000 n _d15 = 1.48749 ν _d15 = 70.23
r ₁₆ = 214.7721
d ₁₆ = D16
r ₁₇ = -8.1890
d ₁₇ = 0.8000 n _d17 = 1.84666 ν _d17 = 23.78
r ₁₈ = -20.0000
d ₁₈ = 2.1000 n _d18 = 1.74320 ν _d18 = 49.34
r ₁₉ = -7.6979 (aspherical surface)
d ₁₉ = 0.6600
r ₂₀ = ∞
d ₂₀ = 1.4400 n _d20 = 1.54771 ν _d20 = 62.84
r ₂₁ = ∞
d ₂₁ = 0.8000
r ₂₂ = ∞
d ₂₂ = 0.6000 n _d22 = 1.51633 ν _d22 = 64.14
r ₂₃ = ∞
d ₂₃ = D23
r ₂₄ = ∞ (imaging surface)

Aspheric coefficient fifth surface K = 0
A ₂ = 0 A ₄ = 3.1801 × 10 ^-4 A ₆ = -7.4933 × 10 ^-6
A ₈ = 1.3268 × 10 ^-7
6th surface K = 0
A ₂ = 0 A ₄ = 1.0755 × 10 ^-4 A ₆ = -2.2069 × 10 ^-6
A ₈ = -4.2215 x 10 ^-8 A ₁₀ = 1.2946 x 10 ^-9
10th surface K = 0
A ₂ = 0 A ₄ = -2.8130 × 10 ^-4 A ₆ = -7.1076 × 10 ^-7
A ₈ = -1.7424 × 10 ^-7
19th page K = 0
A ₂ = 0 A ₄ = 5.5956 × 10 ^-4 A ₆ = -1.7107 × 10 ^-5
A ₈ = 5.6651 × 10 ^-7

When the zoom data D0 (distance from the object to the first surface) is ∞
Wide-angle end Middle telephoto end f (mm) 6.00227 10.39870 17.99964
Fno. 2.8302 3.7274 4.5463
D0 ∞ ∞ ∞
D8 17.74229 9.38185 1.50012
D14 1.39992 10.71211 9.41560
D16 7.69801 6.74827 15.92451
D23 1.36012 1.35450 1.36012

  In each of the above embodiments, an optical system having one reflecting surface is used, but it is also possible to use two or more reflecting surfaces.

  FIG. 5 is a diagram illustrating spectral characteristics of an electrochromic element used as a medium having a variable reflectance. This medium is a medium (substance) that is brought into close contact with the reflection surface FR of the prism P shown in FIGS. FIG. 6 is a diagram showing spectral characteristics of an electrochromic element (when sandwiched between two 1 mm-thick plate glasses) used as a transmittance variable medium. This medium is a medium (substance) inserted between the reflection surface FR shown in FIGS. 2 and 4 and the opposing surface of the prism P.

The values of various conditional expressions and various parameters are shown in the following table. Here, the transmissivity of the electrochromic element itself when used in combination with a transmissive electrochromic element and a reflective surface (see FIGS. 2 and 4) is defined as A1 (Example 1) and A2 (Example 2). I have. Further, in the case of a reflection type electrochromic element (see FIGS. 1 and 3), the transmittance of the electrochromic element itself is B1 (Example 1) and B2 (Example 2). The focal length of the lens group G2 is fb, and the focal length of the entire system at the wide-angle end is fw. The lens group G2 has a positive refractive power, and moves monotonously to the object side when zooming from the wide-angle end to the telephoto end. In the table below, only the maximum value and the minimum value of the transmittance and the reflectance of the electrochromic element are shown, but it is also possible to continuously take an intermediate value between them.

  7 and 8 are conceptual diagrams of a configuration in which the bending optical system is incorporated in a digital camera as the photographing optical system 41. Here, FIG. 7 is a front perspective view showing the appearance of the digital camera 40, and FIG. 8 is a rear perspective view of the same. The illustrated digital camera has a configuration in which the imaging optical path is bent in the long side direction of the digital camera body.

  In this example, the digital camera 40 includes a photographing optical system 41 having a photographing optical path 42, a finder optical system 43 having a finder optical path 44, a shutter 45, a flash 46, a liquid crystal display monitor 47, and the like. When the shutter 45 disposed above the camera 40 is pressed, the photographing is performed through the photographing optical system 41, for example, the optical path bending optical system of the first embodiment in conjunction therewith.

As is clear from the above description, the electronic imaging device of the present invention has the following features in addition to the features described in the claims.
(1) In an electronic imaging apparatus using an optical system having at least one reflecting surface for bending an optical path, the reflecting surface includes an optical element (for example, an electrochromic element) capable of changing light reflectance. An electronic imaging apparatus using an optical system in which the reflectance R520 of light having a wavelength of 520 nm is Rmin ≦ R520 ≦ Rmax and the spectral reflectance satisfies the following condition.
0.50 <R440 / R520 <1.40
0.60 <R600 / R520 <1.70
Here, Rx (x is a number) is the reflectance at a wavelength of x nm. Rmin is the minimum reflectance when the variable reflectance optical element is in the most transparent state, and Rmax is the maximum reflectance when the reflectance variable optical element is in the most opaque state. is there.
(2) The electron according to any one of (1) to (3) or (1), wherein the optical element is made of a medium capable of changing a light transmittance by controlling a chemical change electrically. Imaging device.
(3) The optical system according to any one of (1) to (3), wherein the optical system includes a lens group having a positive refractive power and monotonously moving to the object side when zooming from the wide-angle end to the telephoto end. The electronic imaging device according to (1) or (2).
(4) The optical system according to any one of claims 1 to 3, wherein the optical system includes at least one reflecting surface for bending an optical path on the object side of the lens closest to the object in all the lens groups movable during zooming. An electronic imaging apparatus according to any one of the above (1) to (3).
(5) The optical system includes at least one prism, and the reflection surface is disposed substantially parallel to one surface of the prism, and changes light transmittance between one surface of the prism and the reflection surface. The electronic imaging device according to any one of claims 1 to 3, or any of the above (1) to (4), wherein a medium capable of being caused to intervene is interposed.
(6) The electronic imaging device according to (5), wherein the prism is disposed closest to an object in an optical path passing through the optical system.
(7) The electronic imaging device according to (6), wherein a surface (incident surface) closest to the object in an optical path passing through the prism is a concave surface.
(8) The electronic imaging device according to (7), wherein the prism has a refractive index of 1.68 or more, 1.75 or more, and 1.80 or more.
(9) The electronic imaging device according to any one of (1) to (8) or (1) to (8), wherein the movable lens group closest to the image in the optical system has a focusing function.
(10) The electronic device according to any one of (1) to (3) or (1), further comprising means for electrically controlling a state of the optical system, an electric signal related to an image obtained from an electronic image sensor, and a transmittance of the medium. The electronic imaging device according to any one of (1) to (9).

FIG. 3 is a cross-sectional view along an optical axis showing an optical configuration when a variable-reflectance substance is adhered to a reflection surface of the electronic imaging device according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view along an optical axis showing an optical configuration when a substance having a variable transmittance is sandwiched between a reflecting surface and a prism according to the first embodiment of the electronic imaging apparatus according to the present invention. FIG. 11 is a cross-sectional view along an optical axis showing an optical configuration when a variable-reflectance substance is adhered to a reflection surface of an electronic imaging device according to a second embodiment of the present invention. FIG. 7 is a cross-sectional view along an optical axis showing an optical configuration when a substance with variable transmittance is sandwiched between a reflecting surface and a prism according to a second embodiment of the electronic imaging apparatus according to the present invention. FIG. 4 is a diagram illustrating spectral characteristics of an electrochromic element used as a variable-reflectance substance. FIG. 4 is a diagram illustrating spectral characteristics of an electrochromic element (when sandwiched between two sheet glasses having a thickness of 1 mm) used as a substance having a variable transmittance. FIG. 2 is a front perspective view showing the appearance of the digital camera. FIG. 2 is a rear perspective view showing the appearance of the digital camera.

Explanation of reference numerals

G1 First lens group G2 Second lens group G3 Third lens group G4 Fourth lens group G5 Fifth lens group P prism IF Light incident surface RF reflecting surface I Imaging surface LPF Optical low-pass filter

Claims (3)

  In an electronic imaging apparatus using an optical system having a reflection surface for bending an optical path, an optical element capable of changing light transmittance is provided in the optical system, and a light beam passes through the optical element a plurality of times. An electronic imaging device having a configuration.   In an electronic imaging apparatus using an optical system having a reflecting surface for bending an optical path, an optical element capable of changing light transmittance is provided on the reflecting surface or immediately before the reflecting surface, and a light beam is emitted from the optical element. An electronic imaging device configured to pass through a plurality of times. The electronic imaging apparatus according to claim 1, wherein a transmittance τ520 when light having a wavelength of 520 nm passes through the optical element once satisfies the following condition in an entire range of τmin ≦ τ520 ≦ τmax.
0.70 <τ440 / τ520 <1.20
0.80 <τ600 / τ520 <1.30
Here, τ440 is the transmittance of light having a wavelength of 440 nm and the transmittance of τ600 is light having a wavelength of 600 nm. Further, τmin is the minimum transmittance when the optical element capable of changing the transmittance is in the most opaque state, and τmax is the optical element capable of changing the transmittance is the most transparent. It is the maximum transmittance at the time of the state.