JP2005045609A - Electronic imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small electronic imaging apparatus which, especially, is very thin in its depth. <P>SOLUTION: In a focusing optical system that satisfies the following conditional equation (1) where the reference numeral 19 is a lens closest to an image in the optical system, P is an imaging element surface, and d is a distance between them on an optical axis, a material having a reflectively of 20% or less and 80% or more near the optical axis for wavelengths 500nm and 800nm is comprised at any point on the optical axis as an infrared cut filter, and a double refraction medium F11 which satisfies the following equation (2) is comprised between the lens component 19 which is closest to an image in the focusing optical system and the electronic imaging element surface P. The conditional equation (1) is d≤(0.4p+3.0)/1.5 and the conditional equation (2) is 5<ne no/¾ne<SP>2</SP>- no<SP>2</SP>¾<20 (where, no≤1.7). In the conditional equations (1) and (2), p is horizontal pixel pitch of imaging elements (μm in unit), no is refractive index relative to normal light ray of a double refraction medium, ne is a refractive index relative to the abnormal light ray of the double refraction medium, and d is air-reduced length (mm in unit). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electronic imaging apparatus in which the overall length and volume of an imaging optical system are reduced.

In recent electronic imaging devices such as digital cameras, the miniaturization and thinning have been progressing. This downsizing and thinning are largely due to downsizing of electric circuits and recording media. For this reason, the ratio of the size of the optical system to the entire imaging apparatus has been relatively increased. Therefore, downsizing of the optical system (especially a zoom lens) has also progressed through downsizing of the image sensor. As an example, there is a so-called collapsible lens barrel that protrudes from the optical system at the time of photographing and is housed in an electronic imaging device casing when carried. Thus, the downsizing of the optical system has coped with the reduction in thickness by using mechanical means such as a retractable lens barrel.
However, as miniaturization progresses, the physical processing limit of the lens element constituting the optical system, the mechanical strength limit of the mechanical mechanism, and the limit of manufacturing accuracy are generated. Such a limit makes it difficult to reduce the size of the entire optical system in proportion to the progress of downsizing of the image sensor. Therefore, the number of constituent elements is reduced to the limit by using an aspherical surface and a high refractive index and low dispersion glass material. However, it has also reached the limits of securing basic specifications and correcting aberrations. Therefore, miniaturization of the volume and the total length of the optical system, or thinning in the depth direction at the time of the collapse, has reached its limit.
Thus, as a method for realizing a reduction in thickness particularly in the depth direction, an optical system having a reflecting surface for bending an optical path has been proposed. Such a configuration greatly contributes to reducing the thickness of the electronic imaging device casing.
On the other hand, in the conventional optical system for an electronic imaging device, the ratio of the space occupied by the light amount adjusting mechanism and various filters in the optical system is relatively large and wasteful. Here, examples of the filter include an infrared cut filter and an optical low-pass filter for preventing aliasing.

In a normal electronic imaging apparatus, an optical low-pass filter is disposed between the lens on the most image side of the imaging optical system and the photoelectric conversion surface of the electronic imaging device. As this optical low-pass filter, for example, crystal is used as shown in Patent Document 1. In such a case, for example, when the pixel pitch of the image sensor is 3 μm, d = 2 · ne · no · p / | ne ² −no ² | = 2 · 1.553 · 1.544 · 3 × 10 ^-3 /(1.553 ² -1.544 ² ) ≒ 0.5mm
In addition, a vertical occupancy of about 0.5 mm and a depolarizing plate of about 0.5 mm are added. However, in this example, the angle formed by the optical axis of the imaging optical system and the slow axis of the optical low-pass filter is 45 degrees, ne = 1.553, no = 1.544, and p = 3 × 10 ⁻³ . .
Furthermore, an infrared cut filter having a thickness of about 1 mm is added to this, so that an extra space of about 2.5 mm or more must be secured.
JP-A-8-122708

  The present invention has been made in view of the above-mentioned problems of the prior art. The purpose of the electronic imaging device is to reduce the filter thickness and light amount adjustment mechanism unique to the electronic imaging device, which is an obstacle to downsizing the electronic imaging device, and to reduce the size, especially in the depth direction, extremely thin. Is to provide.

In the electronic image pickup apparatus according to the present invention, the distance d (air conversion length: unit: mm) on the optical axis between the lens closest to the image side of the optical system and the photoelectric conversion surface of the image pickup element is the conditional expression (1). An imaging optical system in the range that has a substance having a reflectance (near the optical axis) of 20% or less and 80% or more at wavelengths of 500 nm and 800 nm, respectively, as an infrared cut filter at any position on the optical axis. A birefringent medium satisfying the following conditional expression (2) is provided between the lens component closest to the image side of the imaging optical system and the electronic image pickup element.
(1) d ≦ (0.4 ・ p + 3.0) /1.5
(2) 5 <ne · no / | ne 2 -no 2 | <20 ( However, no ≦ 1.7)
Here, p is the horizontal pixel pitch (unit: μm), no is the refractive index of the birefringent medium with respect to ordinary rays, and ne is the refractive index of the birefringent medium with respect to extraordinary rays.

In the electronic imaging apparatus according to the invention of the present application, the air conversion length d (distance on the optical axis: unit is mm) between the lens closest to the image side of the optical system and the photoelectric conversion surface of the imaging element is conditional expression (1). In the imaging optical system in the range, a substance having a reflectance (near the optical axis) of 20% or less and 80% or more at wavelengths of 500 nm and 800 nm, respectively, as an infrared cut filter at any position on the optical axis A birefringent medium that satisfies the following conditional expression (2) between the lens component closest to the image side of the imaging optical system and the electronic image pickup device, and when the electronic image pickup device is turned off: Even in a state in which the imaging optical system is housed in the electronic imaging device, the air conversion length d, which is the distance on the optical axis between the lens closest to the image side of the optical system and the photoelectric conversion surface of the imaging device, is a conditional expression. (1) is satisfied.
(1) d ≦ (0.4 ・ p + 3.0) /1.5
(2) 5 <ne · no / | ne 2 -no 2 | <20 ( However, no ≦ 1.7)
p is the horizontal pixel pitch (unit: μm), no is the refractive index of the birefringent medium for ordinary rays, and ne is the refractive index of the birefringent medium for extraordinary rays.

In the electronic imaging apparatus according to the invention of the present application, the air conversion length d (distance on the optical axis: unit is mm) between the lens closest to the image side of the optical system and the photoelectric conversion surface of the imaging element is conditional expression (1). In the imaging optical system in the range, a substance having a reflectance (near the optical axis) of 20% or less and 80% or more at wavelengths of 500 nm and 800 nm, respectively, as an infrared cut filter at any position on the optical axis A birefringent medium that satisfies the following conditional expression (2) between the lens component closest to the image side of the imaging optical system and the electronic image sensor, and the substance as the infrared cut filter is: In the vicinity of the optical axis, the reflectance at a wavelength of 680 nm is 65% or more.
(1) d ≦ (0.4 ・ p + 3.0) /1.5
(2) 5 <ne · no / | ne 2 -no 2 | <20 ( However, no ≦ 1.7)
p is the horizontal pixel pitch (unit: μm), no is the refractive index of the birefringent medium for ordinary rays, and ne is the refractive index of the birefringent medium for extraordinary rays.

In the electronic imaging apparatus according to the invention of the present application, the air conversion length d (distance on the optical axis: unit is mm) between the lens closest to the image side of the optical system and the photoelectric conversion surface of the imaging element is conditional expression (1). In the imaging optical system in the range, a substance having a reflectance (near the optical axis) of 20% or less and 80% or more at wavelengths of 500 nm and 800 nm, respectively, as an infrared cut filter at any position on the optical axis A birefringent medium that satisfies the following conditional expression (2) between the lens component closest to the image side of the imaging optical system and the electronic image pickup device, and when the electronic image pickup device is turned off: Even in a state in which the imaging optical system is housed in the electronic imaging device, the air conversion length d, which is the distance on the optical axis between the lens closest to the image side of the optical system and the photoelectric conversion surface of the imaging device, is a conditional expression. (1) is satisfied, and the substance as the infrared cut filter is near the optical axis. The reflectance at a wavelength of 680 nm is 65% or more.
(1) d ≦ (0.4 ・ p + 3.0) /1.5
(2) 5 <ne · no / | ne 2 -no 2 | <20 ( However, no ≦ 1.7)
p is the horizontal pixel pitch (unit: μm), no is the refractive index of the birefringent medium for ordinary rays, and ne is the refractive index of the birefringent medium for extraordinary rays.

  According to the present invention, it is possible to reduce the size and thickness of an optical system that is an obstacle to downsizing an electronic imaging device, and to realize a small electronic imaging device that is particularly thin in the depth direction. It becomes possible to do.

Prior to the description of the embodiments of the present invention, actions and effects of the present invention will be described.
In the electronic image pickup apparatus of the present invention, a configuration with a short back focus length is employed in the optical system in order to shorten the overall length of the imaging optical system portion. Furthermore, extremely thin filters are used as infrared cut filters and optical low-pass filters. The air-converted length d (distance on the optical axis in the unit of mm) between the most image-side lens of the optical system and the photoelectric conversion surface of the image sensor satisfies the following conditional expression. This d corresponds to the back focus length of the imaging optical system.
(1) d ≦ (0.4 ・ p + 3.0) /1.5
However, p is a horizontal pixel pitch (distance between pixel centers in units of μm).

As the quartz optical filter, a quartz crystal designed so as to be able to perform four-point separation with one point image shifted by about one pixel in the horizontal and vertical directions is often used. In this case, the thickness of the low-pass filter is approximately 0.4 · p (mm). Furthermore, about 0.5 mm is required as a depolarizing plate, about 1 mm as an infrared absorption filter, about 1 mm as a cover glass of an electronic image sensor, and about 0.5 mm in other margins. As a result, conventionally, these elements occupy (0.4 · p + 3.0) /1.5 [mm] of the air-converted distance from the final lens of the imaging optical system to the imaging position.
On the other hand, the imaging optical system employed in the electronic imaging apparatus of the present invention employs an optical system with a shorter back focus. As an infrared cut filter, a material having a reflectance (near the optical axis) of 20% or less and 80% or more at wavelengths of 500 nm and 800 nm, respectively, is used for the optical element at any position on the optical axis. This material is preferably a material having a reflectance of 65% or more at a wavelength of 680 nm. And this substance is substituted as an infrared cut filter by vapor deposition or sputtering. Further, as the optical low-pass filter, a birefringent medium that satisfies the following conditional expression (2) is used between the lens component closest to the image side of the imaging optical system and the electronic image pickup device. By doing in this way, the area | region which functions as an optical low-pass filter can be made very thin.
(2) 5 <ne · no / | ne ² −no ² | <20 (where no ≦ 1.7)
Here, no is the refractive index of the birefringent medium for ordinary rays, and ne is the refractive index of the birefringent medium for extraordinary rays.
In this case, the thickness as a low-pass filter is approximately 0.05 · p (mm), and further, it is approximately 0.05 mm as a depolarizing plate, the thickness as an infrared absorption filter is zero, and is approximately as a cover glass for an electronic image sensor. 1 mm or 0 mm sealed by using a part of the imaging optical system instead of the cover glass, and about 0.5 mm with other margins, etc., d is (0.05 · p + 0.55) /1.5 or (0.05 · p + 1. 55) /1.5 or higher.

Further, the imaging optical system of the present invention may satisfy the following conditional expression (1 ′) or conditional expression (1 ″) instead of the conditional expression (1).
(1 ′) (0.05 · p + 0.55) /1.5≦d≦ [(0.4 · p + 3.0) /1.5] −1.0
(1 ") (0.05 · p + 0.55) /1.5 ≤ d ≤ [(0.4 · p + 3.0) /1.5]-1.5

  As a birefringent medium that satisfies the conditional expression (2), for example, there is a photopolymerizable liquid crystal composition disclosed in JP-A-2002-247455. By controlling the direction of the lines of magnetic force applied to this photopolymerizable liquid crystal composition, it is possible to obtain a state of molecular orientation suitable for an optical low-pass filter (angle formed between the normal to the filter plane and the slow axis). . In this state, a film-like product made of an organic substance can be obtained by performing a photopolymerization reaction. A film-like material made of an organic material is preferable as an optical low-pass filter. In this case, ne = 1.55 and no = 1.63 are possible.

  As an optical low-pass filter, it is necessary to separate four point images in the horizontal direction and the vertical direction. In consideration of this, it is more preferable that the birefringent medium is composed of at least two layers of junctions having different slow axis directions. Since the birefringent medium is a thin film, a support is required. Use of the support occupies that much space, making it meaningless to use a thin birefringent medium. Therefore, the thin film-like birefringent medium is bonded to an optical element constituting an existing imaging optical system or a related optical element. This eliminates the need to use a support. For example, a method in which the image side surface of the image-side lens of the imaging optical system is a plane and the birefringent medium is bonded to the plane is preferable. However, it is not very efficient to perform this joining operation on each lens. Therefore, a plurality of image-side lenses (one surface is flat) of the image forming optical system are integrally formed in a flat shape (arrayed). Further, in this state, the birefringent medium is joined to the plane side so as to reach the plurality of lenses. After that, it is preferable to cut the birefringent medium so that the lenses are one by one. For this purpose, it is preferable that the outermost image side lens of the imaging optical system has a substantially rectangular shape.

  The retractable method can also be adopted in this electronic imaging apparatus. The collapsible method is a structure in which the imaging lens system is housed in the housing when not in use, that is, in a power-off state. In this case, the electronic imaging device may satisfy the conditional expression (1), or the conditional expression (1 ′) or (1 ″) even in the power-off state.

In the present invention, the aperture stop diameter of the imaging optical system may be fixed, and a light quantity adjustment function member may be provided between the most image-side surface and the image sensor photoelectric conversion surface. In particular, an element such as an electrochromic element that can change the amount of transmitted light by controlling the amount of electricity is preferable. Alternatively, a focal plane shutter using electrostatic force may be used. In this way, the mechanism can be considerably miniaturized.
In that case, the distance between the position on the optical axis that determines the aperture value and the top of the object side of the lens group immediately after the aperture stop should be smaller than the lens thickness with the smallest thickness on the optical axis in the lens system. May be. Alternatively, there may be a focal length state in which the top of the surface is located closer to the object side than the aperture stop position. Here, the position on the optical axis that determines the aperture value is the position where the aperture is formed. For example, when the thickness of the aperture stop (in the optical axis direction) is very thin, the position on the optical axis that determines the aperture value is the position of the aperture stop itself. When the aperture stop is thick, the position on the optical axis that determines the aperture value is the aperture position that actually limits the luminous flux.

  Further, it is assumed that the imaging optical system is a zoom lens having the following configuration, for example. That is, a zoom lens having a positive refractive power and including a lens group that moves only to the object side when zooming from the wide-angle end to the telephoto end, and an aperture stop that determines the axial beam diameter is disposed immediately before Suppose that In this case, generally, by bringing the lens unit as close as possible to the front and back of the aperture stop, it is possible to achieve a great effect in improving the zoom ratio and shortening the overall length. This is because it is possible to increase the movable distance of the lens group having the positive refractive power and to increase the positive refractive power. Here, the largest reason why the air space is required is that various mechanisms for making the aperture value variable and an occupied space for the accompanying shutter are necessary. Therefore, if the aperture value is fixed and the shutter is arranged in the vicinity of the imaging surface, this space can be considerably reduced.

  On the other hand, when the shutter is disposed in the vicinity of the imaging surface, it is necessary to lengthen the back focus of the imaging optical system correspondingly. However, in terms of shortening the optical system, the effect obtained by fixing the inner diameter of the diaphragm is much greater. Therefore, the optical total length can be shortened. Therefore, in this case, conditional expression (1) may not necessarily be satisfied. In this case, the thin birefringent medium may be bonded or bonded using the light quantity adjusting function member as a support. However, since the light quantity adjusting function member is coated with a transparent electrode, it is bonded or adhered to the opposite surface.

It should be noted that any of the following (a), (b), or (c) may be employed as the zoom lens type and the electronic image pickup device housing method.
(A) The retractable zoom lens including a first lens unit having a negative refractive power and a second lens unit having an aperture stop and having a positive refractive power and moving only to the object side upon zooming from the wide-angle end to the telephoto end. .
In this case, in order to make the lens group particularly thin, the first group has two negative lenses and a positive lens, and the second group has two positive lenses and one negative lens. These two lenses or all three lenses may be cemented, or it may be configured to have three or fewer lenses.
(B) A first group including a reflective optical element for bending the optical path in order from the object side, an aperture stop, and a lens group that has positive refractive power and moves only to the object side when zooming from the wide-angle end to the telephoto end. Optical path folding zoom lens.
In this case, in particular, the first group is preferably fixed.
(C) A zoom lens in which the number of operating groups including zooming and focusing is two or less. In particular, the lens groups from the object side are arranged in the order of negative, positive, negative, positive, those in the order of negative, positive, positive, positive, those in the order of positive, negative, positive, positive, positive, negative, positive, A zoom lens that is arranged in negative order, and the lens group on the most object side is fixed at both zooming and focusing.
In this case, the storage may be performed by arranging the imaging optical system and the imaging optical system on a straight line and changing the direction of the straight line.

  The infrared cut coat (infrared reflective coat) may be applied between the thin optical low-pass filter and an optical element serving as a support thereof. The thin optical low-pass filter may be disposed closer to the object side than the lens component closest to the image side of the imaging optical system. In this case, it is necessary to make the thickness of the thin optical low-pass filter the reciprocal of the optical system combined lateral magnification on the image side. In addition, it is not preferable that the magnification change greatly as it exceeds 2 times at the maximum and minimum times due to zooming or focusing.

 In addition, as a support for the thin optical low-pass filter, a cover glass for the image sensor or a cover for sealing the periphery of the image sensor may be used.

The electronic image pickup apparatus of the present invention is intended to be downsized and has a certain number of pixels. Therefore, the image pickup element should satisfy the following conditional expression.
(3) 0.2 ≤ p / L ≤ 0.8 (L ≤ 6 mm)
However, L is the diagonal length or circumscribed circle diameter mm of the effective screen area of the image sensor.

  Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view taken along the optical axis of an imaging optical system (zoom lens) used in the electronic imaging apparatus according to the first embodiment of the electronic imaging apparatus of the present invention. FIG. 1 shows a lens arrangement at the time of focusing on a wide-angle end object point, and shows a configuration in which the optical path is bent. FIG. 2 is a cross-sectional view along the optical axis showing the optical configuration of the lens according to Example 1 when focusing on an object point. (A) is a wide-angle end, (b) is an intermediate end, and (c) is a telephoto end. Shows the state.
As illustrated in FIG. 2A, the electronic imaging device according to the first embodiment includes lenses L11 to L9 and a CCD that is an electronic imaging element in order from the object side. In FIG. 1, P is the imaging surface of the CCD. An optical element F11 and an optical element F12 are provided between the lens L19 closest to the image side and the imaging surface P.
The optical element F11 is an optical low-pass filter made of a birefringent medium. As will be described later, the surface of the lens L19 disposed closest to the image side is a flat surface. The optical element F11 is bonded to the plane of the lens L19. A birefringent medium that satisfies conditional expression (2) is used. Further, the birefringent medium is preferably a film-like material made of an organic material obtained by performing a photopolymerization reaction in a state where the photopolymerizable liquid crystal composition has an appropriate molecular orientation as described above. The optical element F12 is a cover glass for an electronic image sensor.
Further, the optical element F12 may be provided with a coating that cuts off light in the infrared region. The infrared cut material is composed of a material having a reflectance in the vicinity of the optical axis of 20% or less and 80% or more for wavelengths of 500 nm and 800 nm on the optical axis, respectively. The infrared cut material and the birefringent medium used in the first embodiment are similarly applied to the second to fifth embodiments. Moreover, you may provide an infrared cut substance in the air contact surface of a lens. Further, the infrared cut substance may be provided on any one surface of the optical element L11, and it is more preferable to do so.

Next, the configuration of the optical system in Example 1 will be described with reference to FIGS. As shown in FIG. 2A, the optical system includes, in order from the object side, a first lens group G11, a second lens group G12, an aperture stop S, a third lens group G13, and a fourth lens group G14. Have.
The first lens group G1 has a negative refractive power as a whole. The first lens group G1 includes a prism L11 and a lens L12 having a positive refractive power and a convex surface facing the object side. The prism L11 has a concave object side surface and a reflective optical surface R1. The prism L11 is configured as a reflecting prism that bends the optical path by 90 °.
The second lens group G12 includes, in order from the object side, a biconcave lens L13 and a biconvex lens L14, and has a positive refractive power as a whole.
The third lens group G13 includes a biconvex lens L15, a biconvex lens L16, and a biconcave lens L17. The lenses L16 and L17 are cemented.
The fourth lens group G14 includes a lens L18 having a positive refractive power whose convex surface faces the object side, and a lens L19 having a positive refractive power whose image side is a plane.
The aperture stop S is provided between the second lens group G12 and the third lens group G13.
As described above, the plane parallel plates F11 and F12 are provided between the lens L19 of the fourth lens group G14 and the imaging surface P in order from the object side.

In this optical system, the position of the aperture stop S, the first lens group G11, and the fourth lens group G14 is fixed when zooming from the wide-angle end to the telephoto end. On the other hand, the second lens group G12 moves to the image side, and the third lens group G13 moves to the object side so as to reduce the distance from the second lens group G2.
The aspherical surfaces are the object side surface of the prism L11 in the first lens group G11, the object side surface of the biconvex lens L12 in the second lens group G12, both surfaces of the lens L13 in the second lens group G12, and the third lens. Provided on both surfaces of the lens L15 in the group G13.

Here, d is the air-converted length between the lens L19 closest to the image side and the imaging surface P (distance on the optical axis: unit is mm), p is the pitch of the horizontal pixel, and no is the refraction of the birefringent medium with respect to the ordinary ray. , Ne is the refractive index of the birefringent medium for extraordinary rays, and L is the diagonal length or circumscribed circle diameter L of the effective screen area of the image sensor.
These numerical values and the numerical values of the specifications calculated in the conditional expressions (1), (2) and (3) in Example 1 are as shown in Table 1 below.
The definitions of the symbols d, p, no, ne and L are the same in the other examples 2 to 5.
Table 1: Specification data of optical element of Example 1

Next, numerical data of optical members constituting the lens optical system of Example 1 are shown.
In the numerical data of the first embodiment, r ₁ , r ₂ ,... Are the curvature radii of the lens surfaces, d ₁ , d ₂ ,... Are the thickness or air spacing of each lens, and n _d1 , n _d2,. , D _d , ν _d2 ,... Are Abbe numbers of the respective lenses, Fno. Is the F number, f is the total focal length, and D0 is the distance from the object to the first surface. The aspherical shape is expressed by the following equation when the optical axis direction is z, the direction orthogonal to the optical axis is y, the conic coefficient is K, and the aspherical coefficients are A ₄ , A ₆ , A ₈ , A _10. It 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 numerical data in Examples 2 to 5 described later.

Numerical data 1
( Example 1: FIGS. 1-2 )
r ₁ = -7.3536 (aspherical surface)
d ₁ = 7.7000 n _d1 = 1.84666 ν _d1 = 23.78
r ₂ = ∞
d ₂ = 0.1500
r ₃ = 9.1610 (aspherical surface)
d ₃ = 2.5000 n _d3 = 1.81474 ν _d3 = 37.03
r ₄ = −37.1914
d ₄ = 0.9988
r ₅ = −7.6332 (aspherical surface)
d ₅ = 0.8000 n _d5 = 1.74320 ν _d5 = 49.34
r ₆ = 9.6951 (Aspherical surface)
d ₆ = 0.6000
r ₇ = 13.1688
d ₇ = 1.6000 n _d7 = 1.846660 ν _d7 = 23.78
r ₈ = −102.0557
d ₈ = 7.1130
r ₉ = ∞ (S: Aperture)
d ₉ = 6.2732
r ₁₀ = 6.6221 (aspherical surface)
d ₁₀ = 4.0001 n _d10 = 1.69350 ν _d10 = 53.21
r ₁₁ = −10.0634 (aspherical surface)
d ₁₁ = 0.1500
r ₁₂ = 14.1848
d ₁₂ = 2.2671 n _d12 = 1.56384 ν _d12 = 60.67
r ₁₃ = −9.6597
d ₁₃ = 0.7000 n _d13 = 1.84666 ν _d13 = 23.78
r ₁₄ = 4.5373
d ₁₄ = 1.2313
r ₁₅ = 7.3234
d ₁₅ = 1.8000 n _d15 = 1.48749 ν _d15 = 70.23
r ₁₆ = 27.3925
d ₁₆ = 1.2082
r ₁₇ = 12.8288
d ₁₇ = 1.6000 n _d17 = 1.68893 ν _d17 = 31.07
r ₁₈ = ∞
d ₁₈ = 0.1500 n _d18 = 1.55000 ν _d18 = 55.00
r ₁₉ = ∞
d ₁₉ = 0.6000
r ₂₀ = ∞
d ₂₀ = 0.6000 n _d20 = 1.51633 ν _d20 = 64.14
r ₂₁ = ∞
d ₂₁ = 0.9003
P = Imaging surface

Aspheric coefficient
First side K = 0
A ₄ = 1.4132 × 10 ^-3 A ₆ = −1.9028 × 10 ^-5
A ₈ = 2.9093 × 10 ^-7
Third side K = 0
A ₄ = −6.1927 × 10 ^-4 A ₆ = 2.755810 ^-6
A ₈ = 5.2339 × 10 ^-9
5th surface K = 0
A ₄ = 1.9790 × 10 ^-3 A ₆ = −3.6491 × 10 ^-5
A ₈ = −2.6053 × 10 ^-7
6th surface K = 0
A ₄ = 1.2893 × 10 ^-3 A ₆ = 1.1954 × 10 ^-5
A ₈ = −3.6742 × 10 ^-6
10th surface K = 0
A ₄ = −5.6290 × 10 ^-4 A ₆ = −1.9308 × 10 ^-6
A ₈ = −2.4047 × 10 ^-7
11th surface K = 0
A ₄ = 6.1196 × 10 ^-4 A ₆ = −7.5022 × 10 ^-6
A ₈ = −1.7398 × 10 ^-8

Zoom data (Example 1)
When D0 (distance from the object to the first surface) is ∞
Wide-angle end Middle Telephoto end
f (mm) 4.02138 6.44535 10.82596
Fno. 2.8489 3.5064 4.3811
D0 ∞ ∞ ∞
D4 0.99882 4.56982 6.81192
D8 7.11296 3.53570 1.30000
D9 6.27316 4.52679 1.30000
D14 1.23135 3.01342 6.20989
D16 1.20824 1.19590 1.20267
D21 0.90031 0.87619 0.90023

  FIG. 3 is a cross-sectional view taken along the optical axis of an imaging optical system (zoom lens) used in the electronic imaging apparatus according to the second embodiment of the electronic imaging apparatus of the present invention. FIG. 3 shows a lens arrangement at the time of focusing on a wide-angle end object point, and shows a configuration in which the optical path is bent. FIG. 4 is a cross-sectional view along the optical axis showing the optical configuration of the lens according to Example 2 when focusing on an object point, where (a) is a wide-angle end, (b) is an intermediate end, and (c) is a telephoto end. Shows the state.

As shown in FIG. 4A, the electronic imaging apparatus of the second embodiment includes lenses L21 to L30 and a CCD that is an electronic imaging element in order from the object side. In FIG. 4, P is the imaging surface of the CCD. An optical element F21 and an optical element F22 are joined between the most image side lens L30 and the imaging surface P.
The optical element F21 is an optical low-pass filter made of a birefringent medium. The optical element F22 is a cover glass for an electronic image sensor.
The birefringent medium is the same as that used in the first embodiment. In addition, the infrared cut substance that cuts off the light in the infrared region can have the same characteristics and arrangement position (coating position) as in the first embodiment.

Next, a lens system of the electronic imaging apparatus according to the second embodiment will be described. In FIG. 4A, this electronic imaging apparatus includes a first lens group G21, an aperture stop S, a second lens group G22, a third lens group G23, and a fourth lens group G24 in order from the object side. is doing.
As shown in FIG. 3, the first lens group G21 has a positive refractive power as a whole. The first lens group G1 includes a negative refractive meniscus lens L21 having a convex surface facing the object side, a prism L22, a biconcave lens L23, and a positive refractive power lens L24 having a convex surface facing the object side. The prism L22 has a flat object side surface and image side surface, and has a reflective optical surface R1. The prism L22 is configured as a reflecting prism that bends the optical path by 90 °.
The second lens group G22 includes, in order from the object side, a lens L25 having a positive refractive power convex toward the object side, a lens L26 having a negative refractive power convex toward the object side, and a biconvex lens L27. The lens L25 and the lens 26 are meniscus lenses and are joined.
The third lens group G23 includes a lens L28 having a positive refractive power and a convex surface on the object side.
The fourth lens group G24 includes a negative refractive power lens L29 and a positive refractive power lens L30 having a concave surface directed toward the object side. The lens L29 and the lens L30 are cemented.
The aperture stop S is provided in the vicinity of the most object side lens unit L27 of the second lens unit G22.
An optical element F22 is provided between the lens L29 closest to the image side of the fourth lens group G24 and the imaging surface P. This optical element F22 is a cover glass of an electronic image sensor. An optical element F21 is provided on the object side surface of the optical element F22. The optical element F21 is an optical low-pass filter made of a birefringent medium.

In this optical system, the positions of the first lens group G21 and the fourth lens group G24 are fixed when zooming from the wide-angle end to the telephoto end. The second lens group G22 moves to the object side together with the aperture stop S, and the third lens group G23 moves to the object side so as to widen the distance from the fourth lens group G24.
The aspheric surfaces are provided on the image side surface of L21 in the first lens group G21, the object side surface of the positive lens L25 in the second lens group G22, and the image side surface of the lens L30 in the fourth lens group G24. It has been.

The numerical values of the specifications used in the conditional expressions (1), (2) and (3) and the numerical values calculated by the conditional expressions in Example 2 are as shown in Table 2 below.
Table 2: Specification data of optical element of Example 2

Next, numerical data of optical members constituting the lens optical system of Example 2 are shown.
Numerical data 2
( Example 2: FIG. 3)
r ₁ = 24.0832
d ₁ = 1.1000 n _d1 = 1.74320 ν _d1 = 49.34
r ₂ = 10.9766 (aspherical surface)
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 = −210.9325
d ₅ = 0.9000 n _d5 = 1.77250 ν _d5 = 49.60
r ₆ = 9.4845
d ₆ = 0.8000
r ₇ = 10.3871
d ₇ = 1.9000 n _d7 = 1.76182 ν _d7 = 26.52
r ₈ = 28.3371
d ₈ = 17.3120
r ₉ = ∞ (S: Aperture)
d ₉ = −0.3001
r ₁₀ = 5.7451 (aspherical surface)
d ₁₀ = 2.5317 n _d10 = 1.74320 ν _d10 = 49.34
r ₁₁ = 13.9263
d ₁₁ = 0.7000 n _d11 = 1.84666 ν _d11 = 23.78
r ₁₂ = 5.6972
d ₁₂ = 0.8000
r ₁₃ = 36.6052
d ₁₃ = 1.5000 n _d13 = 1.72916 ν _d13 = 54.68
r ₁₄ = −16.0591
d ₁₄ = 1.5216
r ₁₅ = 15.8345
d ₁₅ = 1.4000 n _d15 = 1.48749 ν _d15 = 70.23
r ₁₆ = 120.5922
d ₁₆ = 8.0278
r ₁₇ = −17.1776
d ₁₇ = 0.8000 n _d17 = 1.84666 ν _d17 = 23.78
r ₁₈ = 433.7543
d ₁₈ = 2.1000 n _d18 = 1.74320 ν _d18 = 49.34
r ₁₉ = −16.5464 (aspherical surface)
d ₁₉ = 0.8000
r ₂₀ = ∞
d ₂₀ = 0.1500 n _d20 = 1.55000 ν _d20 = 55.00
r ₂₁ = ∞
d ₂₁ = 0.6000 n _d21 = 1.51633 ν _d21 = 64.14
r ₂₂ = ∞
d ₂₂ = 1.0002
P = Imaging surface

Aspheric coefficient
Second side K = 0
A ₄ = −1.5759 × 10 ^-5 A ₆ = −1.6317 × 10 ^-6
A ₈ = 4.0962 × 10 ^-8 A ₁₀ = −3.3522 × 10 ^-10
10th surface K = 0
A ₄ = −3.2319 × 10 ^-4 A ₆ = −4.0466 × 10 ^-6
A ₈ = −3.2128 × 10 ^-7
19th side K = 0
A ₄ = 4.2974 × 10 ^-4 A ₆ = 5.3757 × 10 ^-6
A ₈ = −4.2834 × 10 ^-7

Zoom data (Example 2)
When D0 (distance from the object to the first surface) is ∞
Wide-angle end Middle Telephoto end
f (mm) 6.02364 10.39706 17.98771
Fno. 2.8375 3.8018 4.7313
D0 ∞ ∞ ∞
D8 17.31198 9.30367 1.49840
D14 1.52165 10.76288 9.44741
D16 8.02782 6.78858 15.91574
D22 1.00023 0.97912 1.00002

FIG. 5 is a third embodiment of the electronic image pickup apparatus of the present invention, and is a cross-sectional view taken along the optical axis of an imaging optical system (zoom lens) used in the electronic image pickup apparatus. ) Shows the state at the middle, and (c) shows the state at the telephoto end.
As shown in FIG. 5B, the electronic image pickup apparatus according to the third embodiment includes lens groups G31, G32, G33, and G34 and an image pickup surface P of a CCD that is an electronic image pickup element in order from the object side. . Between the lens L36 closest to the image side of the lens group G34 and the imaging surface P, there are an optical element F31, optical elements F32, F33, and F34 in order from the object side. The optical element F35 is a cover glass for an electronic image sensor.
Here, the optical element F31 is an optical low-pass filter made of a birefringent medium. The optical elements F32 to F34 are parallel plane plates for sandwiching a physical substance having a transmittance variable function or a shutter function. These physical substances have a thickness of several μm to several tens of μm. The parallel flat plate F32, F33, F34 or F35 can be subjected to infrared cut coating.
The birefringent medium is the same as that used in the first embodiment. In addition, the infrared cut substance that cuts off the light in the infrared region can have the same characteristics and arrangement position (coating position) as in the first embodiment.

Next, the configuration of the lens group of Example 3 will be described. As shown in FIG. 5, the electronic imaging apparatus includes a first lens group G31, an aperture stop S, a second lens group G32, and a third lens group G33 in order from the object side.
The first lens group G31 includes a negative refractive power lens L31 having a concave surface directed toward the object side and a positive refractive power lens L32 having a convex surface directed toward the object side. The second lens group G32 includes, in order from the object side, a positive refractive power lens L33 with a convex surface facing the object side, a negative refractive power lens L34, and a positive refractive power lens L35 with a convex surface facing the image side. It consists of Here, the lenses L33 and L34 are cemented. The third lens group G33 is composed of a biconvex lens L36.

When zooming from the wide-angle end to the telephoto end when the object is in focus, only the position of the third lens group G33 is fixed. On the other hand, from the wide-angle end to the intermediate point, the first lens group 31 moves to the image side, and the second lens group G32 moves to the object side. Further, when zooming from the intermediate point to the telephoto end, the zoom lens moves toward the object side so as to reduce the distance between the first lens group G31 and the second lens group G32.
The aspheric surface is provided on the image side surface of the lens L31 in the first lens group G31 and the object side surface of the positive lens L33 in the second lens group G32.

The numerical values of the specifications used in the conditional expressions (1), (2) and (3) in Example 3 and the calculated values based on the conditional expressions are as shown in Table 3 below.
Table 3: Specification data of optical element of Example 3

Next, numerical data of optical members constituting the lens system of Example 3 are shown.
Numerical data 3
( Example 3: FIG. 5)
r ₁ = −237.7768
d ₁ = 1.0000 n _d1 = 1.74320 ν _d1 = 49.34
r ₂ = 4.6140 (Aspherical surface)
d ₂ = 2.2194
r ₃ = 9.6798
d ₃ = 1.8000 n _d3 = 1.84666 ν _d3 = 23.78
r ₄ = 27.1249
d ₄ = 13.2109
r ₅ = ∞ (S: Aperture)
d ₅ = −0.3000
r ₆ = 3.8810 (aspherical surface)
d ₆ = 2.0000 n _d6 = 1.74320 ν _d6 = 49.34
r ₇ = 13.5543
d ₇ = 0.7000 n _d7 = 1.84666 ν _d7 = 23.78
r ₈ = 3.5784
d ₈ = 0.4000
r ₉ = 21.5339
_{d 9 = 1.3000 n d9 = 1.69350} ν d9 = 53.21
r ₁₀ = −9.5160
d ₁₀ = 4.2594
r ₁₁ = 22.1335
d ₁₁ = 1.8000 n _d10 = 1.48749 ν _d10 = 70.23
r ₁₂ = -15.8015
d ₁₂ = 1.4000
r ₁₃ = ∞
d ₁₃ = 0.1500 n _d13 = 1.55000 ν _d13 = 55.00
r ₁₄ = ∞
d ₁₄ = 0.5500 n _d14 = 1.80610 ν _d14 = 40.92
r ₁₅ = ∞
d ₁₅ = 0.5500 n _d15 = 1.80610 ν _d15 = 40.92
r ₁₆ = ∞
d ₁₆ = 0.5500 n _d16 = 1.80610 ν _d16 = 40.92
r ₁₇ = ∞
d ₁₇ = 0.8000
r ₁₈ = ∞
d ₁₈ = 0.6000 n _d18 = 1.51633 ν _d18 = 64.14
r ₁₉ = ∞
d ₁₉ = 0.9985
P = Imaging surface

Aspheric coefficient
Second side K = 0
A ₄ = −1.2109E-03 × 10 ^-3 A ₆ = 9.5995 × 10 ^-6
A ₈ = −3.9173 × 10 ^-6
6th surface K = 0
A ₄ = −1.0331 × 10 ^-3 A ₆ = −2.2307 × 10 ^-5
A ₈ = −4.9292 × 10 ^-6

Zoom data (Example 3)
When D0 (distance from the object to the first surface) is ∞
Wide-angle end Middle Telephoto end
f (mm) 4.51553 8.69354 12.90018
Fno. 2.8393 3.8981 4.8344
D0 ∞ ∞ ∞
D4 13.21087 4.80964 1.35092
D10 4.25941 9.84579 14.31454
D12 1.40000 0.89799 1.49086
D19 0.99846 0.99631 0.99819

FIG. 6 shows a fourth embodiment of the electronic image pickup apparatus of the present invention, which is a sectional view taken along the optical axis of an imaging optical system (zoom lens) used in the electronic image pickup apparatus. ) Shows the state at the middle, and (c) shows the state at the telephoto end.
As shown in FIG. 6B, the electronic image pickup apparatus according to the fourth embodiment includes lens groups G41, G42, and G43 and an image pickup surface P of a CCD that is an electronic image pickup element in order from the object side. An optical element F41 and an optical element F42 are joined between the lens L46 of the lens group G43 and the imaging surface P. The optical element F41 is an optical low-pass filter made of a birefringent medium. The optical element F42 is a cover glass for an electronic image sensor. In addition, the coating which cuts an infrared region can also be given to the optical element F42.
The birefringent medium is the same as that used in the first embodiment. In addition, the infrared cut substance that cuts off the light in the infrared region can have the same characteristics and arrangement position (coating position) as in the first embodiment.

Next, the lens system of Example 4 will be described. The electronic imaging apparatus includes a first lens group G41, an aperture stop S, a second lens group G42, and a third lens group G43 in order from the object side.
The first lens group G41 includes, in order from the object side, a negative refractive power lens L41 having a flat surface facing the object side and a positive refractive power lens L42 having a convex surface facing the object side. The second lens group G42 includes, in order from the object side, a lens L43 having a positive refractive power which is a biconvex surface, a lens L44 having a negative refractive power having a concave surface facing the image side, and a lens L45 having a positive refractive power. . The third lens group G43 includes a lens L46 having a positive refractive power and a convex surface on the object side.
The aperture stop S is provided between the first lens group G41 and the second lens group G42.

When zooming from the wide-angle end to the telephoto end at the time of focusing on the object point, the position of the third lens group G43 is fixed. On the other hand, from the wide-angle end to the intermediate point, the first lens group G41 moves toward the image side, and the aperture stop S and the second lens group G42 move toward the object side. When zooming from the intermediate point to the telephoto end, the first lens group G41, the aperture stop S, and the second lens group G42 are configured to reduce the distance between the first lens group G41, the stop S, and the second lens group G42. It moves to the object side.
The aspheric surfaces are provided on the image side surface of the lens L41 in the first lens group G41, the object side surface of the lens L43 in the second lens group G42, and the object side surface of the lens L46 in the third lens group G43. ing.

The numerical values of the specifications used in the conditional expressions (1), (2) and (3) in Example 4 and the numerical values calculated by the conditional expressions are as shown in Table 4 below.
Table 4: Specification data of optical element of Example 4

Next, numerical data of optical members constituting the lens system of Example 4 are shown.
Numerical data 4
( Example 4: FIG. 6)
r ₁ = ∞
d ₁ = 0.7000 n _d1 = 1.74320 ν _d1 = 49.34
r ₂ = 5.3396 (aspherical surface)
d ₂ = 1.4911
r ₃ = 8.2804
d ₃ = 2.0000 n _d3 = 1.84666 ν _d3 = 23.78
r ₄ = 15.3056
d ₄ = 15.0761
r ₅ = ∞ (S: Aperture)
d ₅ = 1.2000
r ₆ = 5.5089 (aspherical surface)
d ₆ = 2.2000 n _d6 = 1.74320 ν _d6 = 49.34
r ₇ = −21.2357 *
d ₇ = 0.2000
r ₈ = 15.3280
d ₈ = 0.7000 n _d8 = 1.84666 ν _d8 = 23.78
r ₉ = 4.4663
d ₉ = 1.5000
r ₁₀ = 11.1733
d ₁₀ = 1.2000 n _d10 = 1.69680 ν _d10 = 55.53
r ₁₁ = 59.5366
d ₁₁ = 5.9922
r ₁₂ = 9.4345 (aspherical surface)
d ₁₂ = 1.5000 n _d12 = 1.58913 ν _d12 = 61.14
r ₁₃ = 1432.0920
d ₁₃ = 0.7000
r ₁₄ = ∞
d ₁₄ = 0.1500 n _d14 = 1.55000 ν _d14 = 55.00
r ₁₅ = ∞
d ₁₅ = 0.6000 n _d15 = 1.51633 ν _d15 = 64.14
r ₁₆ = ∞
d ₁₆ = 0.8000
P = Imaging surface

Aspheric coefficient
Second side K = 0
A ₄ = −5.5363 × 10 ^-4 A ₆ = 5.0629 × 10 ^-6
A ₈ = −1.2187 × 10 ^-6
6th surface K = 0
A ₄ = −8.6371 × 10 ^-4 A ₆ = 4.9477 × 10 ^-7
A ₈ = −2.7074 × 10 ^-6
12th surface K = 0
A ₄ = 06.6468 × 10 ^-5 A ₆ = −1.8037 × 10 ^-4
A ₈ = 6.7441E-06 * × 10 ^-6

Zoom data (Example 4)
When D0 (distance from the object to the first surface) is ∞
Wide-angle end Middle Telephoto end
f (mm) 4.51576 8.69042 12.89754
Fno. 2.8489 3.6635 4.4531
D0 ∞ ∞ ∞
D4 15.07610 5.08003 1.50000
D9 1.50000 2.00040 2.70000
D11 5.99216 9.99596 14.21031
D13 0.70000 0.70000 0.70000
D16 0.79996 0.82102 0.79872

FIG. 7 is a fifth embodiment of the electronic imaging apparatus of the present invention, and is a cross-sectional view taken along the optical axis of an imaging optical system (zoom lens) used in the electronic imaging apparatus. ) Shows the state at the middle, and (c) shows the state at the telephoto end.
As shown in FIG. 7B, the electronic imaging apparatus of the fifth embodiment includes, in order from the object side, a lens group G51, aperture stops S, G52, G53, and G54, and an imaging surface P of a CCD that is an electronic imaging element. Have. An optical element F51, optical elements F52, F53, and F54 are provided on the optical axis between the lens L57 and the imaging surface P of the lens group G54. The optical element F55 is a cover glass for an electronic image sensor.
Here, the optical element F51 is an optical low-pass filter made of a birefringent medium. The optical elements F52 to F54 are parallel plane plates for sandwiching a physical substance having a transmittance variable function or a shutter function. These physical substances have a thickness of several μm to several tens of μm. This parallel flat plate F52, F53, F54 or F55 can be subjected to infrared cut coating. The optical element F55 also serves as a light control element.
The birefringent medium is the same as that used in the first embodiment. In addition, the infrared cut substance that cuts off the light in the infrared region can have the same characteristics and arrangement position (coating position) as in the first embodiment.

Next, a lens system according to Example 5 will be described. The electronic imaging apparatus includes a first lens group G51, an aperture stop S, a second lens group G52, and a third lens group G53 in order from the object side.
The first lens group G51 includes a negative refractive power lens L51 having a concave surface facing the object side, and a positive refractive power lens L52 having a convex surface facing the object side. The second lens group G52 includes, in order from the object side, a positive refractive power lens L53 having a convex surface facing the object side, a positive refractive power lens L54, and a negative refractive power lens L55 having a concave surface facing the image side. It is configured. Here, the lenses L54 and L55 are cemented.
The third lens group G53 is composed of a biconcave lens L56, and the fourth lens group G54 is composed of a biconvex lens L57.

When zooming from the wide-angle end to the telephoto end when the object is in focus, only the position of the fourth lens group G54 is fixed. On the other hand, from the wide-angle end to the intermediate point, the first lens group G51 moves to the image side, and the second lens group G52 moves to the object side. Further, when zooming from the intermediate point to the telephoto end, the distance between the first lens group G51 and the second lens group G52 is shortened, and the distance between the second lens group G52 and the third lens group G53 is increased. It moves to the object side so as to spread.
The aspheric surface is provided on the image side surface of the lens L51 in the first lens group G51, the object side surface of the positive lens L53 in the second lens group G52, and the image side surface of L57 in the fourth lens group G54. ing.

The numerical values of the specifications used in the conditional expressions (1), (2) and (3) in Example 5 and the numerical values calculated by the conditional expressions are as shown in Table 5 below.
Table 5: Specification data of optical element of Example 5

Next, numerical data of optical members constituting the lens optical system of Example 5 are shown.
Numerical data 5
( Example 5: FIG. 7 )
r ₁ = -14.8863
d ₁ = 0.7000 n _d1 = 1.80610 ν _d1 = 40.92
r ₂ = 5.3084 (aspherical surface)
d ₂ = 1.9998
r ₃ = 14.2302
d ₃ = 1.8000 n _d3 = 1.71736 ν _d3 = 29.52
r ₄ = −21.3860
d ₄ = 13.6191
r ₅ = ∞ (S: Aperture)
d ₅ = −0.1500
r ₆ = 10.5813 (aspherical surface)
d ₆ = 5.0000 n _d6 = 1.69350 ν _d6 = 53.21
r ₇ = −7.9769
d ₇ = 0.1500
r ₈ = 3.6083 *
d ₈ = 1.5000 n _d8 = 1.51633 ν _d8 = 64.14
r ₉ = 20.0000
d ₉ = 0.7000 n _d9 = 1.84666 ν _d9 = 23.78
r ₁₀ = 2.7838 *
d ₁₀ = 1.1998
r ₁₁ = −452.3818
d ₁₁ = 0.7000 n _d11 = 1.72916 ν _d11 = 54.68
r ₁₂ = 12.5029
d ₁₂ = 1.5014
r ₁₃ = 144.4615
d ₁₃ = 1.8000 n _d13 = 1.68893 ν _d13 = 31.07
r ₁₄ = -7.9374 (aspherical surface)
d ₁₄ = 0.8000
r ₁₅ = ∞
d ₁₅ = 0.1500 n _d15 = 1.55000 ν _d15 = 55.00
r ₁₆ = ∞
d ₁₆ = 0.5500 n _d16 = 1.51633 ν _d16 = 64.14
r ₁₇ = ∞
d ₁₇ = 0.5500 n _d17 = 1.51633 ν _d17 = 64.14
r ₁₈ = ∞
d ₁₈ = 0.5500 n _d18 = 1.51633 ν _d18 = 64.14
r ₁₉ = ∞
d ₁₉ = 0.5500 n _d19 = 1.51633 ν _d19 = 64.14
r ₂₀ = ∞
d ₂₀ = 0.9491
P = Imaging surface

Aspheric coefficient
Second side K = 0
A ₄ = −1.3562 × 10 ^-3 A ₆ = −9.1346 × 10 ^-6
A ₈ = −9.3488 × 10 ^-7
6th surface K = 0
A ₄ = −7.9013 × 10 ^-4 A ₆ = −1.9664 × 10 ^-5
A ₈ = 7.4124 × 10 ^-7
14th surface K = 0
A ₄ = 1.2358 × 10 ^-3 A ₆ = −1.0460 × 10 ^-5
A ₈ = −3.5525 × 10 ^-7

Zoom data (Example 5)
When D0 (distance from the object to the first surface) is ∞
Wide-angle end Middle Telephoto end
f (mm) 4.50064 8.69054 12.90039
Fno. 2.8045 3.6955 4.8669
D0 ∞ ∞ ∞
D4 13.61915 3.12109 0.55000
D10 1.19982 4.05832 4.34689 *
D12 1.50135 1.49861 4.99523 *
D14 0.80000 0.80000 0.80000
D20 0.94906 0.95434 0.95028S

In the above embodiment, the infrared cut coat may be applied to any one of the air contact surfaces of each lens. Optical elements and optical element surfaces are preferred. In the case of an optical element or an optical element, it is not always necessary to apply the air contact surface. The birefringent material may be a polymer film.
The invention of the present application has the following characteristics in addition to the invention described in the claims.
4. The small electronic imaging device according to claim 1, wherein the birefringent medium is composed of at least two layers of junctions having different slow axis directions.
(Ii) The image side surface of the most image-side lens of the imaging optical system is a plane, and the birefringent medium is joined to the plane. A small electronic imaging device according to any one of the above.
(Iii) A plurality of lenses on the most image side (one surface is flat) of the imaging optical system are integrally formed in a flat shape, and in this state, a plurality of lenses are arranged so as to reach the plurality of lenses on the flat side. The small electronic imaging device as described in (ii) above, wherein the birefringent medium is cut and formed so that the refractive media are joined and the lenses are one by one.
(Iv) The compact electronic imaging device according to item (iii), wherein the lens on the most image side of the imaging optical system has a substantially rectangular outer shape.
(V) The small-sized electronic imaging device according to claim 1, wherein an aperture stop diameter of the imaging optical system is fixed.
(Vi) The distance between the position on the optical axis for determining the aperture value and the top of the object side surface of the lens group immediately after the aperture stop is smaller than the lens thickness with the smallest thickness on the optical axis in the lens system or the top of the surface The small electronic imaging device as described in (v) above, wherein there is a focal length state in which is located closer to the object side than the aperture stop position.
(Vii) A light amount adjusting function member is provided between a surface closest to the image side of the imaging optical system and a photoelectric conversion surface of the image sensor, or (i) to (vi) A small electronic imaging device according to any one of the above.
(Viii) The imaging optical system has a positive refractive power, and includes a lens unit that moves only to the object side when zooming from the wide-angle end to the telephoto end. The small electronic imaging device according to any one of claims 1 to 3 or (i) to (vii), comprising a zoom lens, wherein the zoom lens is a lens disposed.
(Ix) The light quantity adjusting functional member includes a planar optical member coated with a transparent electrode, and a birefringent medium satisfying the following conditional expression is bonded to one of them. 3. A small electronic imaging apparatus according to 1 or 2.
(2) 5 <ne · no / | ne ² −no ² | <20
(X) The compact electronic imaging according to any one of claims 1 to 3 and (ii) to (ix), wherein the position of the lens closest to the object side of the imaging optical system is fixed. apparatus.
(Xi) The compact electronic imaging device as described in (x) above, wherein the lens unit closest to the object side of the imaging optical system has a reflective optical element for bending the optical path.
(Xii) The small electronic imaging device according to any one of claims 1 to 3 or (i) to (xi), wherein at least two lens groups move during zooming.

It is sectional drawing which follows the optical axis which shows the optical structure concerning Example 1 of the lens used for the electronic imaging device by this invention, and has shown the state at the time of bending at the time of wide-angle end object point focusing. FIG. 2 is a cross-sectional view along the optical axis showing the optical configuration of the lens according to Example 1, where (a) shows the state at the wide-angle end, (b) shows the middle, and (c) shows the state at the telephoto end. It is sectional drawing which follows the optical axis which shows the optical structure concerning Example 2 of the lens used for the electronic imaging device by this invention, and has shown the state at the time of bending at the time of wide-angle end object point focusing. FIG. 5 is a cross-sectional view along the optical axis showing the optical configuration of a lens according to Example 2, where (a) shows a state at a wide angle end, (b) shows an intermediate state, and (c) shows a state at a telephoto end. FIG. 7 is a cross-sectional view along an optical axis showing an optical configuration at the time of focusing of a lens according to Example 3, where (a) shows a state at a wide angle end, (b) shows an intermediate state, and (c) shows a state at a telephoto end. . FIG. 7 is a cross-sectional view along an optical axis showing an optical configuration at the time of focusing of a lens according to Example 4, where (a) shows a state at a wide angle end, (b) shows an intermediate state, and (c) shows a state at a telephoto end. . FIG. 10 is a cross-sectional view along an optical axis showing an optical configuration at the time of focusing of a lens according to Example 5, where (a) shows a state at a wide angle end, (b) shows an intermediate state, and (c) shows a state at a telephoto end. .

Explanation of symbols

F11, F21, F31, F41, F51 Optical low-pass filters F12, F22, F35, F42, F55 Cover glasses G11, G21, G31, G41, G51 First lens group G12, G22, G32, G42, G52 Second lens group G13, G23, G33, G43, G53 Third lens group G14, G24, G34, G44, G54 Fourth lens group Lnn Lens element P Imaging surface R1 Reflective optical surface S Aperture stop

Claims (3)

An imaging optical system that satisfies the following conditional expression (1), where d is the distance on the optical axis between the lens closest to the image side of the optical system and the photoelectric conversion surface of the image sensor, The most image side lens of the imaging optical system having a material having a reflectance in the vicinity of the optical axis of 20% or less and 80% or more for wavelengths of 500 nm and 800 nm, respectively, as an infrared cut filter at any of the above positions An electronic imaging apparatus comprising a birefringent medium that satisfies the following conditional expression (2) between a component and an electronic imaging element:
(1) d ≦ (0.4 ・ p + 3.0) /1.5
(2) 5 <ne · no / | ne 2 -no 2 | <20 ( However, no ≦ 1.7)
Where p is the horizontal pixel pitch of the image sensor (unit: μm), no is the refractive index of the birefringent medium with respect to the ordinary ray, ne is the refractive index of the birefringent medium with respect to the extraordinary ray, and d is the air equivalent length (unit is mm). ).   Even when the imaging optical system is housed in the electronic imaging device when the electronic imaging device is turned off, the distance on the optical axis between the lens closest to the image side of the optical system and the photoelectric conversion surface of the imaging device The electronic imaging apparatus according to claim 1, wherein d satisfies the conditional expression (1).   The electronic imaging apparatus according to claim 1 or 2, wherein the substance as the infrared cut filter has a reflectance of 65% or more at a wavelength of 680 nm in the vicinity of the optical axis.

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