JP2002090624A - Electronic imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To thoroughly thin an electronic imaging device, having a zoom lens by selecting a zoom system which has stable high image-forming performance, ranging from infinity to a short distance. SOLUTION: This electronic imaging device is provided with the zoom lens provided with a 1st negative group G1 nearest to the object side, consisting of four or more groups G1 to G4, set so that the spaces between the groups from the 1st one to the 4th one from the object side are changed in the middle of varying power; and the group G4 nearest to an image side is fixed and consists of one positive aspherical single lens, and is provided with an aperture diaphragm integrally moving with the 2nd group G2 at the time of varying power, and satisfying the condition: (1), 1.5<L2/Y<3.5, where L2 is the moving amount of the 2nd group G2 from the wide-angle end to the telephoto end, and Y is the diagonal length of the effective imaging area of an imaging device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic image pickup apparatus which is made thinner in the depth direction by devising an optical system such as a zoom lens, and more particularly to a video camera and a digital camera. In addition, the zoom lens makes rear focus possible.

[0002]

2. Description of the Related Art In recent years, digital cameras (electronic cameras) have been attracting attention as next-generation cameras replacing silver halide 35 mm film (commonly known as Leica) cameras. Furthermore, it has come to have a number of categories in a wide range from professional high-performance types to portable popular types. The present invention pays particular attention to the portable popular category, and aims to provide a technique for realizing a video camera and a digital camera with a small depth while ensuring high image quality. The biggest bottlenecks in reducing the depth of the camera are the optics,
In particular, the thickness from the most object side surface of the zoom lens system to the imaging surface. In recent years, it has become mainstream to employ a so-called collapsible lens barrel that protrudes an optical system from the inside of a camera body during photographing and stores the optical system in the camera body when carrying the camera. However, the thickness when the optical system is collapsed greatly differs depending on the lens type and filter used. In particular, in order to set specifications such as the zoom ratio and the F value to be high, a so-called positive-lead type zoom lens in which the lens unit closest to the object side has a positive refractive power has a large thickness and dead space of each lens element, and However, the thickness is not so small (Japanese Patent Laid-Open No. 11-258507). A negative lead type zoom lens having two or three groups is particularly advantageous in that respect.
Even if the number of components in the group is large, the thickness of the element is large, or if the lens closest to the object side is a positive lens or collapsed, the lens does not become thin (Japanese Patent Laid-Open No. 11-52246). Japanese Patent Application Laid-Open No. Hei 11 (1999) discloses an example of a device which is currently known, which is suitable for an electronic image pickup device, has good imaging performance including a zoom ratio, an angle of view, an F value, and the like, and has the possibility of making the collapsed thickness the thinnest.
JP-A-194274, JP-A-11-287953 and JP-A-2000-9997.

[0003] In order to make the first lens group thinner, it is better to make the entrance pupil position shallower. For this purpose, the magnification of the second lens group must be increased. On the other hand, the burden on the second lens unit increases, which makes it difficult to reduce the thickness of the second lens unit itself, and also increases the difficulty of aberration correction and the effect of manufacturing errors, which is not preferable. In order to reduce the thickness and size, it is necessary to reduce the size of the imaging element. However, in order to obtain the same number of pixels, it is necessary to reduce the pixel pitch, and the lack of sensitivity must be covered by an optical system. The same goes for the effects of diffraction.

Further, in order to make the camera body thinner, a so-called rear focus, rather than a front lens group, is effective on the layout of a drive system when the lens is moved during focusing. Then, it is necessary to select an optical system that causes little aberration fluctuation when the rear focus is performed.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of such a situation of the prior art, and has as its object to reduce the number of components in an electronic image pickup apparatus having a zoom lens, and to use a rear focus method or the like. Select a zoom configuration or a zoom configuration that has a high imaging performance that is stable from infinity to short distances because of its small size, easy to make simple in terms of mechanism layout, and furthermore, the lens element is thinned to reduce the total thickness of each group. In addition, the thickness should be reduced thoroughly in consideration of the selection of filters.

[0006]

In order to achieve the above object, an electronic imaging apparatus according to the present invention comprises an electronic imaging device having an imaging optical system and an electronic imaging device arranged on the image side of the imaging optical system. In the imaging apparatus, the imaging optical system includes an aspherical and always fixed most image-side final lens, and a focus lens group that is disposed immediately before the object side of the final lens and moves for focusing. And characterized in that:

In this case, it is preferable that the imaging optical system has a lens unit having a positive refractive power that moves only to the object side when zooming from the wide-angle end to the telephoto end.

The imaging optical system includes, in order from the object side, a first lens unit having a negative refractive power, and a first lens unit having a positive refractive power that moves only to the object side when zooming from the wide-angle end to the telephoto end. It may have two lens groups.

The imaging optical system includes, in order from the object side, a first lens unit having a negative refractive power, and a plurality of positive refractive powers moving only to the object side when zooming from the wide-angle end to the telephoto end. May be provided.

According to another aspect of the present invention, there is provided an electronic imaging apparatus including an imaging optical system and an electronic imaging device disposed on an image side of the imaging optical system.
A mutual distance from a first lens group having a negative refractive power disposed closest to the object side and at least three lens groups disposed on the image side thereof to a fourth lens group continuing from the object side; Is changed for zooming or focusing, and the lens group closest to the image side is fixedly constituted by one aspherical lens, and is integrated with the lens group immediately after the image side of the first lens group during zooming. It has a moving aperture stop.

According to another aspect of the present invention, there is provided an electronic image pickup apparatus including a zoom lens and an electronic image pickup element arranged on an image side of the zoom lens, wherein the zoom lens is arranged in order from an object side. A first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a positive refractive power, and a fourth lens group. By extending the lens to the side, it is possible to focus on a subject at a shorter distance, and the fourth lens group is composed of a single fixed lens including an aspheric surface.

According to another aspect of the present invention, there is provided an electronic image pickup apparatus including a zoom lens and an electronic image pickup device arranged on an image side of the zoom lens.
A first lens group having a negative refractive power, in order from the object side;
A second lens group having a positive refractive power, a third lens group having a positive refractive power, and a fourth lens group. By moving the third lens group toward the object side, it is suitable for a subject at a shorter distance. The second lens group is composed of one single lens including an aspheric surface, and a cemented lens composed of a positive lens and a negative lens in order from the object side, and the third lens group is , One positive single lens.

Still another electronic imaging apparatus according to the present invention is an electronic imaging apparatus including a zoom lens and an electronic imaging element arranged on the image side of the zoom lens, wherein the zoom lens is a negative lens in order from an object side. A first lens group having a positive refractive power, a second lens group having a positive refractive power, a third lens group having a positive refractive power, and a fourth lens group. The second lens group is composed of one positive lens including an aspherical surface and one negative lens by extending to the side, and the third lens group Is characterized by comprising one positive single lens.

In the above, the first lens group can be moved during zooming.

In the image forming optical system employed in the electronic image pickup apparatus of the present invention, the lens closest to the image (single lens or cemented lens) includes an aspherical surface, which is always fixed, and the lens group immediately before this focuses. This is a rear focus type zoom lens that is moved for the purpose. Therefore,
Despite the rear focus method, stable and high imaging performance can be secured from infinity to short distance. This is particularly effective when a lens unit having a positive refractive power that moves monotonously to the object side when zooming from the wide-angle end to the telephoto end. In a zoom lens having such a lens group, an aspherical surface is introduced in the final lens group in order to reduce aberration fluctuations over the entire zoom range from the wide-angle end to the telephoto end and to reduce aberrations in any state. Then, off-axis aberrations such as coma and astigmatism are corrected. Therefore,
When focusing is performed by the final group having an aspherical surface, fluctuations in off-axis aberrations such as coma and astigmatism due to the movement in the optical axis direction tend to increase, leading to performance degradation. Therefore, it is preferable that the last group having an aspheric surface is fixed, and focusing is performed in the group immediately before the last group.

It is to be noted that the first group of such zoom lenses is preferably made up of a negative lens group for compactness, but the above problem is more remarkable than when the first group is a positive lens group. .

For example, specifically, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power ,
An imaging optical system comprising a zoom lens capable of focusing on a subject at a shorter distance by extending the third lens group to the object side, wherein the fourth lens group is aspheric. An imaging optical system composed of one fixed lens including: or, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power,
A zoom lens, comprising a third lens group having a positive refractive power and a fourth lens group, which can focus on an object at a shorter distance by extending the third lens group toward the object side. The group includes one single lens including an aspheric surface, and one cemented lens in the order of a positive lens and a negative lens.
The lens group includes an imaging optical system including a single positive lens as a single lens, or a first lens group having a negative refractive power and a second lens group having a positive refractive power in order from the object side.
A zoom lens, comprising a third lens group having a positive refractive power and a fourth lens group, which can focus on an object at a shorter distance by extending the third lens group toward the object side. Positive lens (single lens or cemented lens) and negative lens (single lens or cemented lens) whose group includes an aspheric surface
This is the case in the case of an imaging optical system composed of a single positive lens, which is a single lens, in which the third lens group is a single lens.

It is more preferable that the fourth lens group, which is the final lens group, has a positive refractive power because the angle of incidence on the electronic image pickup device can be made nearly vertical. In order to reduce the number of parts, this lens group can be formed as an aspheric single lens.

As described above, in the movable lens group during zooming, aberration variation over the entire zooming range is corrected to be as small as possible, and substantially uniform aberrations, particularly off-axis aberrations, are reduced by placing an aspherical surface in the final lens group. Has been removed. However, especially in the case of coma aberration, correction cannot be performed unless the lens surface for correction is at a certain distance from the image plane. Therefore, the air-equivalent distance DR on the optical axis between the last lens group and the image plane preferably satisfies the following condition.

(X) 0.3 <DR / Y <2.5 where Y is the diagonal length of the effective imaging area (substantially rectangular) of the imaging device.

When the lower limit of 0.3 to condition (x) is exceeded,
It is easy to correct distortion due to the aspherical surface of the last lens group, but it is difficult to correct coma. If the upper limit of 2.5 is exceeded, the overall length of the optical system and the lens diameter of the lens group far from the aperture stop tend to be enlarged.

More preferably, (x-1) 0.4 <DR / Y <2.0.

Further, it is more preferable that (x-2) 0.5 <DR / Y <1.5.

In order to cover as much as possible the space loss caused by the above configuration, the distance D between the fixed last lens group including the aspherical surface and the focus group immediately before the fixed last lens group.
_{For 34W} (at the wide-angle end when _{focusing on an} object point at infinity), it is better to satisfy the following conditions.

(Y) 0.05 <D _{34W /Y<0.8 When the} value exceeds the upper limit of 0.8 of the condition (y), the overall length of the optical system is likely to be long or it is difficult to secure a zoom ratio. Lower limit of 0.05
Is provided to avoid mechanical interference between the two groups.

Further, it is more preferable that (y-1) 0.05 <D _34W /Y<0.6.

It is more preferable that (y-2) _satisfy 0.05 < _{D34W /} Y < _0.4 .

Further, by making the first lens unit, which is the lens unit closest to the object side, movable with zooming, the first lens unit can be provided with a compensator function. It is more preferable because the magnification ratio can be increased.

Next, an invention to which the above-mentioned invention is applied will be described.

To achieve the above object, another electronic imaging apparatus according to the present invention comprises a first electronic imaging device having a negative refractive power closest to an object.
A group having four or more groups. The groups up to the fourth group from the object side change their mutual distance during zooming, and the group closest to the image has a fixed positive refractive power. A zoom lens and an electronic image pickup device, comprising an aspherical single lens, having an aperture stop that moves integrally with the second unit during zooming, and satisfying the following condition (1): It has.

(1) 1.5 <L ₂ /Y<3.5 where L ₂ is the amount of movement of the second lens unit from the wide-angle end to the telephoto end, and Y is the effective imaging area (substantially rectangular) of the imaging device. Diagonal length.

In the structure of the zoom lens according to the present invention, the thickness of each lens unit is easily reduced, the structure is simple, and the image forming performance is stable both during zooming and during focusing. Also,
F value fluctuation due to zooming is small. However, there is a disadvantage that the fluctuation of the exit pupil position is large. This is because the amount of movement of the diaphragm during zooming is large. When the value exceeds the upper limit of 3.5 of the condition (1), the angle of the principal ray on the imaging surface at the wide angle end or the telephoto end becomes too large, which is not preferable. If the lower limit of 1.5 is exceeded, fluctuations of aberrations such as astigmatism at the time of zooming or focusing become large, which is not preferable.

It is more preferable to replace condition (1) with the following.

(1-1) 1.6 <L ₂ /Y<3.3 Further, the following is more preferable.

(1-2) 1.7 <L ₂ /Y<3.0 It is preferable that the lower limit or the upper limit of the above formula be individually limited.

According to the present invention, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, a third lens unit having a positive refractive power, and a positive refractive power are arranged in order from the object side. When the zoom lens is composed of a fourth lens unit and the magnification is changed from the wide-angle end to the telephoto end at the time of focusing on an object point at infinity, the distance between the second and third lens units becomes large,
By extending the third group toward the object side, it is possible to focus on a subject at a shorter distance, and the fourth group is composed of a single aspheric single lens having a positive refractive power. An electronic imaging apparatus may include a zoom lens and an electronic imaging element satisfying the condition (2).

[0037] (2) -1.2 <however ^{_{ex P W / ex P T <}} 0, measured from the image plane at the wide angle end and the telephoto end during ^ex P _W, ^ex P _T respectively focused on an infinite object point Exit pupil position.

In the case of this zoom system, since the change amount of the exit pupil position is large from wide angle to telephoto, it is necessary to make it fall within the condition (2). Beyond the upper limit of 0,
Shading tends to occur at the wide-angle end, and when the lower limit of -1.2 is exceeded, shading tends to occur at the telephoto end.

The following is more preferable.

(2-1) −1.1 < ^ex _PW / ^ex _PT <−0.2 Further, the following is more preferable.

[0041] _{^{(2-2) -1.0 <ex P W}} / ex P T <-0.4 be limited each individually lower limit or the upper limit value of the above formula preferably.

According to the present invention, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, a third lens unit having a positive refractive power, and a positive refractive power are arranged in order from the object side. When zooming from the wide-angle end to the telephoto end when focusing on an object point at infinity, the distance between the second and third units increases, and the third unit is extended toward the object side. It is possible to focus on a subject at a closer distance with the second group, one single lens including an aspheric surface in order from the object side and a positive lens from the object side,
The third lens unit includes a cemented lens configured in the order of a negative lens, and the third unit includes one single lens having a positive refractive power, and satisfies the following conditions (3) and (4). An electronic imaging device having an imaging element may be provided.

(3) −1.5 <(R _2C1 + R _2C2 ) ·
( _{R2C2- R2C3} ) / ( _{R2C1- R2C2} ). ( _R2C2 +
_{R 2C3) <- 0.3 (4} ) 0.05 <t 2N / t 2 <0.3 , _{however, R 2C1, R 2C2, R} 2C3 is the first and second from the object side of the cemented lens in the second group And the radius of curvature of each of the third lens surfaces on the optical axis, t _2N is the thickness of the negative lens in the cemented lens of the second group on the optical axis, and t ₂ is the distance from the most object side surface of the second group. This is the thickness on the optical axis up to the surface closest to the image.

The condition (3) defines the ratio of the shape factor of each lens element (positive lens / negative lens) of the cemented lens of the second group. Exceeding the lower limit of -1.5 is disadvantageous for correcting axial chromatic aberration, and exceeding the upper limit of -0.3 is disadvantageous for increasing the thickness of the lens element and reducing its size.

The condition (4) defines the thickness on the optical axis of the negative lens (joined) of the second group. If this part is not thickened to some extent, astigmatism cannot be corrected completely, but this is a constraint when the thickness of each element of the optical system is reduced. Therefore, astigmatism is corrected by introducing an aspherical surface into the lens on the image side. Nevertheless, when the value exceeds the lower limit of 0.05, astigmatism cannot be completely corrected. Exceeding the upper limit of 0.3 makes the thickness unacceptable.

It is more preferable that the conditions (3) and (4) be set individually or together as follows.

(3-1) -1.3 <(R _2C1 +
R _2C2 ) ・ (R _2C2 −R _2C3 ) / (R _2C1 −R _2C2 ) ・
_{(R 2C2 + R 2C3) <} - 0.4 (4-1) 0.06 <t 2N / t 2 <0.28 In addition, the condition (3), if (4) the as follows individually or together Still preferred.

(3-2) -1.2 <(R _2C1 +
R _2C2 ) ・ (R _2C2 −R _2C3 ) / (R _2C1 −R _2C2 ) ・
_{(R 2C2 + R 2C3) <} - 0.5 (4-2) 0.07 <t 2N / t 2 < preferable to limit each individual 0.26 lower limit or the upper limit value of the above formula.

The present invention also has, in order from the object side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, a third lens unit having a positive refractive power, and a positive refractive power. When the zoom lens system is composed of the fourth lens unit and zooms from the wide-angle end to the telephoto end when focusing on an object point at infinity, the distance between the second lens unit and the third lens unit increases, and the third lens unit is extended toward the object side. The second group is composed of one positive lens component and one negative lens component each including an aspheric surface in order from the object side, and the third group has a positive refractive power. And an electronic imaging device comprising a zoom lens and an electronic imaging element that includes one single lens having the following and satisfies the following condition (5).

(5) 0.05 <t _2NI / t ₂ <0.3 where t _2NI is the thickness of the negative lens closest to the image side in the second group on the optical axis, and t ₂ is the thickness of the second group. This is the thickness on the optical axis from the surface closest to the object to the surface closest to the image. Here, the lens component is a concept indicating a single lens or a cemented lens.

The condition (5) is a condition for balancing the correction of astigmatism and the thickness of the second lens unit, similarly to the condition (4).

The condition (5) may be the following condition (5-1) or (5-2), and it is preferable to limit only the upper limit or the lower limit of the following formula.

(5-1) 0.06 <t _2NI / t ₂ <0.28 (5-2) 0.07 <t _2NI / t ₂ <0.26 By the way, in each of the above inventions, the zoom lens When the zoom ratio is 2.3 or more, satisfying the following conditions (a) and (b) contributes to a reduction in thickness.

(A) 0.9 <-β _23t <1.8 (b) 2.0 <f ₂ / f _W <3.0 where β _23t is infinity at the telephoto end of the second and third lens _units . synthesis magnification upon focusing object point focusing, f ₂ is the focal length of the second lens group, f _W
Is the wide-angle end focal length of the entire zoom lens system when focused on an object point at infinity.

The condition (a) defines the infinite object point magnification β _23t at the telephoto end of the second and third lens _units .
In this case, when the absolute value is as large as possible, the entrance pupil position at the wide angle end can be made shallower, so that the diameter of the first lens unit can be easily reduced, and the thickness can be reduced. Beyond the lower limit of 0.9,
It is difficult to satisfy the thickness, and if it exceeds the upper limit of 1.8,
Aberration correction (spherical aberration, coma, astigmatism) becomes difficult.

The condition (b) defines the focal length f ₂ of the second lens unit. A shorter focal length is advantageous for reducing the thickness of the second unit itself, but the front principal point of the second unit is located on the object side,
It is easy for the power arrangement such that the rear principal point of the first group is located on the image side to occur, which is not preferable for aberration correction. If the lower limit of 2.0 is exceeded, it becomes difficult to correct spherical aberration, coma, astigmatism, and the like. If the upper limit of 3.0 is exceeded, thinning becomes difficult.

It is more preferable that each of (a) and (b) be performed individually or together as follows.

(A-1) 0.9 <-β _23t <1.7 (b-1) 2.1 <f ₂ / f _W <2.8 Further, the following is more preferable.

(A-2) 1.1 <-β _23t <1.6 (b-2) 2.2 <f ₂ / f _W <2.6 The lower limit or upper limit of the above formula is individually limited. It is also preferable.

The first unit may be composed of a negative lens unit composed of two negative lenses and a positive lens unit composed of one positive lens in order from the object side, or two lenses in order from the object side.
A negative lens group consisting of no more than one negative lens and a positive lens group consisting of one positive lens, wherein at least one negative lens in the negative lens group has a configuration including an aspheric surface;
Good compatibility with the configuration of the second, third and fourth lens groups in aberration correction. In other words, aberration variation during focusing is small, and aberration correction can be favorably performed in all magnification ranges.

The total thickness of the first group and the second group may satisfy the following condition.

(6) 0.6 <t ₁ /Y<2.2 (7) 0.3 <t ₂ /Y<1.5 where t ₁ is the most image from the most object side surface of the first lens unit. Is the thickness on the optical axis up to the side surface, t ₂ is the thickness on the optical axis from the most object side surface to the most image side surface of the second group, and Y is the effective imaging of the image sensor. This is the diagonal length of the region (substantially rectangular).

The conditions (6) and (7) define the total thickness of the first and second lens units, respectively. Exceeding the respective upper limit values of 2.2 and 1.5 tends to hinder thinning, and exceeding the lower limit values of 0.6 and 0.3 necessitates relaxing the radius of curvature of each lens surface. It becomes difficult to establish a paraxial relationship and to correct various aberrations. When the lower limits of the conditions (6) and (7) are smaller than the lower limits of 0.6 and 0.3, respectively, the lens thickness becomes thin. Therefore, when trying to secure the thickness and the rim from the center of the lens to the periphery, the curvature of each lens becomes loose, and it becomes impossible to secure the power required for each lens.

It should be noted that this condition range is preferably changed according to the value of Y in order to secure the rim and machine space.

Specifically, the following conditions (6-1) and (7)
It is desirable to satisfy -1).

(6-1) When Y ≦ 6.2 mm 0.8 <t ₁ /Y<2.2 When 6.2 mm <Y ≦ 9.2 mm 0.7 <t ₁ /Y<2.0 When 9.2 mm <Y 0.6 <t ₁ /Y<1.8 (7-1) When Y ≦ 6.2 mm 0.5 <t ₂ /Y<1.5 6.2 mm <Y ≦ 9 0.2 mm 0.4 <t ₂ /Y<1.3 9.2 mm <Y 0.3 <t ₂ /Y<1.1 As described above, an image is formed while reducing the collapsed thickness of the zoom lens unit. A means to improve performance was provided.

Next, the point that the filters are made thinner will be described. In an electronic imaging apparatus, an infrared absorption filter having a certain thickness is usually inserted on the object side of the imaging element so that infrared light does not enter the imaging surface. Consider replacing this with a thinner coating. Naturally, it is thinner, but it has a side effect. The transmittance at the wavelength of 600 nm is 80% or more and the transmittance at the wavelength of 700 nm is 10% on the object side with respect to the imaging element located behind the zoom lens system.
When the following near-infrared sharp cut coat is introduced, the transmittance on the red side becomes relatively higher than that of the absorption type, and the tendency of magenta on the blue-violet side, which is a drawback of the CCD having a complementary color mosaic filter, is reduced by gain adjustment. Thus, color reproduction comparable to that of a CCD having a primary color filter can be obtained. On the other hand, in the case of the complementary color filter, since the transmitted light energy is high, the sensitivity is substantially higher than that of the CCD with the primary color filter and the resolution is also advantageous.
The advantage of using D is great.

It is preferable that the total thickness t _LPF on the optical axis of the optical low-pass filter, which is the other filter, satisfy the following condition.

(8) 0.15 × 10 ³ <t _LPF / a <
0.45 × 10 ³ where a is the horizontal pixel pitch of the electronic image sensor.

It is effective to reduce the thickness of the optical low-pass filter in order to reduce the collapsible thickness. However, in general, the effect of suppressing moiré is undesirably reduced. On the other hand, as the pixel pitch becomes smaller, the contrast of the frequency component equal to or higher than the Nyquist limit decreases due to the influence of the diffraction of the imaging lens system, and the reduction of the moiré suppression effect is allowed to some extent. For example, when the azimuth angle during projection on the image plane is horizontal (= 0
It is known that when three types of filters having crystal axes in the directions of (°) and ± 45 °, respectively, are used in an overlapping manner in the optical axis direction, there is a considerable moire suppressing effect. The thinnest filter in this case is specified as aμ
It is known to shift SQRT (1/2) × a in the directions of m and ± 45 °, respectively. Here, SQRT is a square route and means a square root. Filter thickness is approximately [1 + 2 × SQRT (1/2 )] × a × 10 3/5.
88 (mm). This is a specification that makes the contrast zero at a frequency corresponding to the Nyquist limit. If the thickness is reduced by several percent to several tens percent, contrast at a frequency corresponding to the Nyquist limit appears slightly, but it can be suppressed by the influence of the diffraction. It is preferable that the condition (8) is satisfied including filter specifications other than those described above, for example, the case where two filters are stacked or one filter is used. When the value exceeds the upper limit of 0.45 × 10 ³ , the optical low-pass filter is too thick, which hinders reduction in thickness.
If the lower limit of 0.15 × 10 ³ is exceeded, moire removal will be insufficient. However, when this is performed, the condition of a is desirably 5 μm or less.

When a is 4 μm or less, it is more susceptible to diffraction, so that it is preferable to satisfy the following condition (8-1).

(8-1) 0.13 × 10 ³ <t _LPF /
a <0.42 × 10 ³ Alternatively, the following may be performed. The low-pass filter is a stack of three low-pass filters,
When 4 μm ≦ a <5 μm, (8-2) 0.3 × 10 ³ <t _LPF /a<0.4×1
0 ³ may be satisfied.

The low-pass filter is obtained by superposing two low-pass filters, and 4 μm ≦ a <
At the time of 5 μm, (8-3) 0.2 × 10 ³ <t _LPF /a<0.28×
It is better to satisfy 10 ³ .

When the low-pass filter is a single low-pass filter and 4 μm ≦ a <5 μm, (8-4) 0.1 × 10 ³ <t _LPF /a<0.16×
It is better to satisfy 10 ³ .

When the low-pass filter is obtained by superposing three low-pass filters and a <4 μm, (8-5) 0.25 × 10 ³ <t _LPF /a<0.37
It is better to satisfy × 10 ³ .

When the low-pass filter is obtained by superposing two low-pass filters and a <4 μm, (8-6) 0.16 × 10 ³ <t _LPF /a<0.25
It is better to satisfy × 10 ³ .

When the low-pass filter is composed of one low-pass filter and a <4 μm, (8-7) 0.08 × 10 ³ <t _LPF /a<0.14
It is better to satisfy × 10 ³ .

When an image pickup device having a small pixel pitch is used, the image quality is degraded due to the diffraction effect caused by stopping down. Accordingly, a plurality of apertures having a fixed aperture shape are provided, and one of the apertures is connected to the lens surface closest to the image in the first group and the third aperture.
An electronic imaging device capable of adjusting the image plane illuminance by being able to be inserted into any optical path between the lens surfaces closest to the object side of the group and being replaceable with another is provided. In some of the plurality of openings, a wavelength of 5
The transmittance for 50 nm is different, and
%, It is preferable to adjust the amount of light by setting the transmittance of the other openings to a wavelength of 550 nm of 80% or more.

Alternatively, the F number (f / ID) obtained from the focal length f of the zoom lens and the diameter ID of the entrance pupil is expressed by F
_no , F _no / ΔT when the transmittance at the wavelength of 550 nm in the aperture is T is an effective F number F _no ′, and when the horizontal pixel pitch of the electronic imaging device is a, F _no / ΔT
_{When the} adjustment is performed so that the light amount is equivalent to the effective F-number such that _no '> a / 0.4 μm, an opening provided with a medium having a transmittance T of less than 80% at a wavelength of 550 nm in the opening. It is preferable to use an electronic imaging device that is inserted into the optical path of the zoom lens. For example, when the aperture value is out of the range of the above conditions, a dummy medium or space having a transmittance of 91% or more for the medium or a wavelength of 550 nm is set. It is better to adjust the light amount with something like an ND filter instead of reducing the diameter.

Further, the plurality of apertures are arranged so that their diameters are reduced in inverse proportion to the F value, and optical low-pass filters having different spatial frequency characteristics are inserted in the apertures instead of the ND filters. May be. Since the aperture diffraction deterioration increases as the aperture is narrowed down,
It is preferable to set the spatial frequency characteristics of the optical low-pass filter higher as the aperture diameter becomes smaller. Here, higher spatial frequency characteristics mean that the contrast of the spatial frequency of the object image is kept higher than that of the others. In other words, it means that, for example, the cutoff frequency is large.

[0081]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 to 6 of a zoom lens used in an electronic image pickup apparatus according to the present invention will be described below. FIGS. 1 to 6 show sectional views of the lenses at the wide-angle end when focusing on an object point at infinity in these embodiments. In each figure, the first
Group G1, Group 2 G2, Group 3 G3, Group 4 G
An optical low-pass filter F having a near-infrared cut coat provided on the first surface (surface on the object side) of an optical low-pass filter composed of four or three sheets, and a cover glass of a CCD which is an electronic imaging device. C, the image plane of the CCD where the complementary color mosaic filter is provided is indicated by I, and the optical low-pass filter F and the cover glass C arranged in order from the object side are the fourth group G4. Image plane I
Is fixedly arranged between them. In addition, in each figure,
The focus group is illustrated as “focus”, and the direction of focusing to a short distance is illustrated by an arrow.

As shown in FIG. 1, the zoom lens according to the first embodiment has a first group G1 having a negative refractive power, a second group G2 having a positive refractive power,
The zoom lens includes a third lens unit G3 having a positive refractive power and a fourth lens unit G4 having a positive refractive power. When zooming from the wide-angle end to the telephoto end during focusing on an object point at infinity, the first lens unit G1 temporarily moves to the image side. Thereafter, the lens moves in reverse to the object side, moves from the wide-angle end to the object side at the telephoto end, the second group G2 moves toward the object side, and the third group G3 moves slightly toward the image side and then moves toward the object side. Inverse, at the telephoto end, the position becomes the same as the position at the wide-angle end. The fourth unit G4 is a fixed lens unit, and the distance between the second unit G2 and the third unit G3 is changed when zooming from the wide-angle end to the telephoto end. growing. Then, the third lens group G3 is moved toward the object side to focus on a subject at a short distance.

The first group G1 of the first embodiment includes a negative meniscus lens having a convex surface facing the object side, a biconcave lens, and a positive meniscus lens having a convex surface facing the object side.
A third lens unit G3 includes a stop, a biconvex lens disposed after the stop, and a cemented lens of the biconvex lens and the biconcave lens.
Is composed of one positive meniscus lens having a concave surface facing the object side, and the fourth group G4 is composed of one positive meniscus lens having a convex surface facing the object side. The aspherical surface is used for the three surfaces of the object side surface of the biconcave lens in the middle of the first group G1, the most object side surface of the second group G2, and the object side surface of the fourth group G4.

As shown in FIG. 2, the zoom lens according to the second embodiment has a first group G1 having a negative refractive power, a second group G2 having a positive refractive power,
The zoom lens includes a third lens unit G3 having a positive refractive power and a fourth lens unit G4 having a positive refractive power. When zooming from the wide-angle end to the telephoto end during focusing on an object point at infinity, the first lens unit G1 temporarily moves to the image side. After that, the lens moves in reverse to the object side, and moves from the wide-angle end to the object side at the telephoto end. The second group G2 moves toward the object side, the third group G3 moves toward the object side, and the fourth group G4 moves toward the object side. The second group G is a fixed lens group.
The distance between the second lens unit and the third lens unit G3 increases when zooming from the wide-angle end to the telephoto end. Then, the third lens group G3 is moved toward the object side to focus on a subject at a short distance.

The first group G1 of the second embodiment includes a negative meniscus lens having a convex surface facing the object side, a biconcave lens, and a positive meniscus lens having a convex surface facing the object side.
Numeral 2 is composed of a stop lens, a biconvex lens disposed thereafter, a cemented lens of a positive meniscus lens having a convex surface facing the object side, and a negative meniscus lens having a convex surface facing the object side.
The group G3 includes one positive meniscus lens having a concave surface facing the object side, and the fourth group G4 includes one positive meniscus lens having a convex surface facing the object side. The aspherical surface is used for the three surfaces of the object side surface of the biconcave lens in the middle of the first group G1, the most object side surface of the second group G2, and the object side surface of the fourth group G4.

As shown in FIG. 3, the zoom lens according to the third embodiment has a first group G1 having a negative refractive power, a second group G2 having a positive refractive power,
The zoom lens includes a third lens unit G3 having a positive refractive power and a fourth lens unit G4 having a positive refractive power. When zooming from the wide-angle end to the telephoto end during focusing on an object point at infinity, the first lens unit G1 temporarily moves to the image side. Thereafter, the lens moves in reverse to the object side, moves from the wide-angle end to the object side at the telephoto end, the second group G2 moves toward the object side, and the third group G3 moves slightly toward the image side and then moves toward the object side. Inverse, at the telephoto end, the position becomes the same as the position at the wide-angle end. The fourth unit G4 is a fixed lens unit, and the distance between the second unit G2 and the third unit G3 is changed when zooming from the wide-angle end to the telephoto end. growing. Then, the third lens group G3 is moved toward the object side to focus on a subject at a short distance.

The first group G1 of the third embodiment includes a negative meniscus lens having a convex surface facing the object side, a biconcave lens, and a positive meniscus lens having a convex surface facing the object side.
A third lens unit G3 includes a stop, a biconvex lens disposed after the stop, and a cemented lens of the biconvex lens and the biconcave lens.
Is composed of one positive meniscus lens having a concave surface facing the object side, and the fourth group G4 is composed of one positive meniscus lens having a convex surface facing the object side. The aspherical surface is used for the three surfaces of the object side surface of the biconcave lens in the middle of the first group G1, the most object side surface of the second group G2, and the object side surface of the fourth group G4.

As shown in FIG. 4, the zoom lens of the fourth embodiment has a first group G1 having a negative refractive power, a second group G2 having a positive refractive power,
The zoom lens includes a third lens unit G3 having a positive refractive power and a fourth lens unit G4 having a positive refractive power. When zooming from the wide-angle end to the telephoto end during focusing on an object point at infinity, the first lens unit G1 temporarily moves to the image side. Thereafter, the lens unit is inverted and moved to the object side, at the telephoto end, slightly closer to the image side than at the wide-angle end, the second unit G2 moves to the object side, and the third unit G3 temporarily moves slightly to the image side and then moves to the object side. At the telephoto end, the position becomes the same as the position at the wide-angle end. The fourth unit G4 is a fixed lens unit, and the distance between the second unit G2 and the third unit G3 changes when zooming from the wide-angle end to the telephoto end. Become larger. Then, the third lens group G3 is moved toward the object side to focus on a subject at a short distance.

The first group G1 of the fourth embodiment includes a biconcave lens,
It consists of a positive meniscus lens with the convex surface facing the object side,
The second group G2 includes a stop, a biconvex lens disposed after the stop, and a cemented lens of the biconvex lens and the biconcave lens.
The third group G3 includes one positive meniscus lens having a concave surface facing the object side, and the fourth group G4 includes one positive meniscus lens having a convex surface facing the object side. The aspherical surface is the image-side surface of the biconcave lens of the first group G1, the most object-side surface of the second group G2,
The third group G4 is used for three surfaces on the object side.

As shown in FIG. 5, the zoom lens according to the fifth embodiment includes a first group G1 having a negative refractive power, a second group G2 having a positive refractive power,
The zoom lens includes a third lens unit G3 having a positive refractive power and a fourth lens unit G4 having a positive refractive power. When zooming from the wide-angle end to the telephoto end during focusing on an object point at infinity, the first lens unit G1 temporarily moves to the image side. Thereafter, the lens unit is inverted and moved to the object side, at the telephoto end, slightly closer to the image side than at the wide-angle end, the second unit G2 moves to the object side, and the third unit G3 temporarily moves slightly to the image side and then moves to the object side. At the telephoto end, the position becomes the same as the position at the wide-angle end. The fourth unit G4 is a fixed lens unit, and the distance between the second unit G2 and the third unit G3 changes when zooming from the wide-angle end to the telephoto end. Become larger. Then, the third lens group G3 is moved toward the object side to focus on a subject at a short distance.

The first group G1 of the fifth embodiment includes a negative meniscus lens having a convex surface facing the object side and a positive meniscus lens having a convex surface facing the object side. The third group G3 comprises a positive meniscus lens 1 having a concave surface facing the object side, and a cemented lens of a bi-convex lens and a negative meniscus lens having a concave surface facing the object side, and a negative meniscus lens having a convex surface facing the object side. 4th
The group G4 includes one positive meniscus lens having a convex surface facing the object side. The aspherical surface is the image-side surface of the negative meniscus lens of the first group G1, the most object-side surface of the second group G2, and the fourth group G4.
Are used for three surfaces on the object side.

As shown in FIG. 6, the zoom lens of Embodiment 6 has a first group G1 having a negative refractive power, a second group G2 having a positive refractive power,
The zoom lens includes a third lens unit G3 having a positive refractive power and a fourth lens unit G4 having a positive refractive power. When zooming from the wide-angle end to the telephoto end during focusing on an object point at infinity, the first lens unit G1 temporarily moves to the image side. Thereafter, the lens unit is inverted and moved to the object side. At the telephoto end, the image is slightly closer to the image side than at the wide-angle end. At the telephoto end, it is slightly closer to the object side than at the wide-angle end. The fourth group G4 is a fixed lens group, and the distance between the second group G2 and the third group G3 varies from the wide-angle end to the telephoto end. When you get bigger. Then, the third lens group G3 is moved toward the object side to focus on a subject at a short distance.

The first unit G1 of the sixth embodiment includes a negative meniscus lens having a convex surface facing the object side and a positive meniscus lens having a convex surface facing the object side. The third group G3 comprises one positive meniscus lens having a convex surface facing the object side, and the fourth group G4 has a concave meniscus lens having the convex surface facing the object side. It consists of one positive meniscus lens. The aspherical surface is used for the image-side surface of the negative meniscus lens of the first group G1, the object-side surface of the second group G2, and the image-side surface of the fourth group G4.

In the following, numerical data of each of the above embodiments are shown. Symbols other than those described above, f is the focal length of the entire system, ω is a half angle of view,
F _NO is the F-number, FB designates the back focal, WE wide-angle end, ST intermediate state, TE is the telephoto end, r _1, r ₂ ... curvature radius of each lens surface, d _1, d ₂ ... each lens surface , N _d1 , n _d2 ... are the d-line refractive indices of each lens, ν _d1 ,
ν _d2 ... is the Abbe number of each lens. The aspherical shape is represented by the following equation, where x is an optical axis where the traveling direction of light is positive, and y is a direction orthogonal to the optical axis.

X = (y ² / r) / [1+ ｛1- (K +
^{1) (y / r) 2} } 1/2] + A 4 y 4 + A 6 y 6 + A 8 y 8 +
A ₁₀ y ¹⁰ where r is the paraxial radius of curvature, K is the conic coefficient, A ₄ , A ₆ ,
A ₈ and A ₁₀ are fourth-order, sixth-order, eighth-order, and tenth-order aspherical coefficients, respectively.

[0096] (Example _{1) r 1 = 18.0970 d 1} = 0.7000 n d1 = 1.77250 ν d1 = 49.60 r 2 = 5.8020 d 2 = 2.1000 r 3 = -177.9703 ( _{aspherical) d 3 = 1.1000 n d2 =} 1.69350 ν _{d2 = 53.21 r 4 = 51.8035 d} 4 = 0.2000 r 5 = 10.6733 d 5 = 1.6000 n d3 = 1.84666 ν d3 = 23.78 r 6 = 18.0845 d 6 = ( variable) r ₇ = ∞ (stop) d ₇ = 1.2000 r ₈ = 7.2593 _{(aspherical) d 8 = 1.7000 n d4 =} 1.80610 ν d4 = 40.92 r 9 = -18.3091 d 9 = 0.2000 r 10 = 15.6090 d 10 = 1.5000 n d5 = 1.77250 ν d5 = 49.60 r 11 = -43.4179 d 11 _{= 0.6000 n d6 = 1.84666 ν d6} = 23.78 r 12 = 5.1331 d 12 = ( _{variable) r 13 = -41.6479 d 13 =} 1.5000 n d7 = 1.48749 ν d7 = 70.23 r 14 = -10.1261 d 14 = ( variable) r ₁₅ = 7.2826 _{(aspherical) d 15 = 1.5000 n d8 =} 1.48749 ν d8 = 70.23 r 16 = 50.0000 d 16 = 0.5000 r 17 = ∞ d 17 = 1.6000 n d9 = 1.54771 ν d9 = 62.84 r 18 = ∞ d 18 = 0.8000 _{r 19 = ∞ d 19 = 0.7500} n d10 = 1.51633 ν d10 = 64.14 r ₂₀ = ｄ d ₂₀ = 1.2092 r ₂₁ = ∞ Aspheric coefficient third surface K = 0 A ₄ = 3.4145 × 10 ^-4 A ₆ = -1.1843 × 10 ^-5 A ₈ = 5.7153 × 10 ^-7 A ₁₀ = 0.0000 eighth surface _{K = 0 A 4 = -6.5802 ×} 10 -4 A 6 = 1.2613 × 10 -5 A 8 = -1.8636 × 10 -6 A 10 = 0.0000 fifteenth surface _{K = 0 A 4 = -5.3407 ×} 10 - ⁴ A ₆ = 2.0151 × 10 ^-5 A ₈ = -1.2730 × 10 ^-6 A ₁₀ = 0.0000 Zoom data (∞) WEST TE f (mm) 4.49823 8.69116 12.90020 F _NO 2.5234 3.5716 4.5401 2ω (°) 58.2 32.1 22.0 d ₆ 13.32311 4.84747 1.50000 d ₁₂ 1.72237 9.30698 15.42999 d ₁₄ 1.20000 0.60000 1.20000 Zoom data (20 cm) WEST TE d ₆ 13.32311 4.84747 1.50000 d ₁₂ 1.34032 7.87880 12.68428 d ₁₄ 1.58205 2.02818 3.94571.

(Example 2) r ₁ = 12.0547 d ₁ = 0.7000 n _d1 = 1.77250 v _d1 = 49.60 r ₂ = 5.3746 d ₂ = 2.1000 r ₃ = -110.7152 (aspherical surface) d ₃ = 1.1000 n _d2 = 1.69350 v _{d2 = 53.21 r 4 = 26.5615 d} 4 = 0.2000 r 5 = 7.9348 d 5 = 1.6000 n d3 = 1.84666 ν d3 = 23.78 r 6 = 10.5244 d 6 = ( variable) r ₇ = ∞ (stop) d ₇ = 1.2000 r ₈ = 5.9452 _{(aspherical) d 8 = 1.7000 n d4 =} 1.80610 ν d4 = 40.92 r 9 = -27.4015 d 9 = 0.2000 r 10 = 12.7674 d 10 = 1.5000 n d5 = 1.77250 ν d5 = 49.60 r 11 = 184.0467 d 11 = _{0.6000 n d6 = 1.84666 ν d6 =} 23.78 r 12 = 4.0178 d 12 = ( _{variable) r 13 = -70.2155 d 13 =} 1.5000 n d7 = 1.48749 ν d7 = 70.23 r 14 = -9.1337 d 14 = ( variable) r ₁₅ = 7.5302 (aspheric surface) d ₁₅ = 1.5000 n _d8 = 1.48749 ν _d8 = 70.23 r ₁₆ = 50.0000 d ₁₆ = 0.5000 r ₁₇ = ∞ d ₁₇ = 1.6000 _{nd 9} = 1.54771 ν _d9 = 62.84 r ₁₈ = ｄ d ₁₈ = 0.8000 r _{19 = ∞ d 19 = 0.7500 n} d10 = 1.51633 ν d10 = 64.14 _{20 = ∞ d 20 = 1.2094 r} 21 = ∞ aspherical coefficients third surface _{K = 0 A 4 = 3.1630 ×} 10 -4 A 6 = -1.1384 × 10 -5 A 8 = 4.5936 × 10 -7 A 10 = 0.0000 second 8th surface K = 0 A ₄ = -8.3820 × 10 ^-4 A ₆ = 1.6127 × 10 ^-5 A ₈ = -3.4324 × 10 ^-6 A ₁₀ = 0.0000 15th surface K = 0 A ₄ = -9.4093 × 10 ^-5 A ₆ = 2.4910 × 10 ^-5 A ₈ = -3.0519 × 10 ^-7 A ₁₀ = 0.0000 Zoom data (∞) WEST TE f (mm) 4.50859 8.68782 12.89685 F _NO 2.5234 3.5716 4.5401 2ω (°) 58.0 32.1 22.0 d ₆ 13.23777 4.60124 1.50000 d ₁₂ 1.82131 3.84703 8.20830 d ₁₄ 1.20000 5.08615 9.20000 Zoom data (20cm) WEST TE d ₆ 13.23777 4.60124 1.50000 d ₁₂ 1.51294 2.95755 6.48645 d ₁₄ 1.50837 5.97563 10.92185.

[0098] (Example _{3) r 1 = 24.1351 d 1} = 0.7000 n d1 = 1.77250 ν d1 = 49.60 r 2 = 5.9538 d 2 = 2.1000 r 3 = -147.9609 ( _{aspherical) d 3 = 1.1000 n d2 =} 1.52542 ν _{d2 = 55.78 r 4 = 74.8539 d} 4 = 0.2000 r 5 = 11.5684 d 5 = 1.6000 n d3 = 1.84666 ν d3 = 23.78 r 6 = 20.8120 d 6 = ( variable) r ₇ = ∞ (stop) d ₇ = 1.2000 r ₈ = 6.3335 _{(aspherical) d 8 = 1.7000 n d4 =} 1.80610 ν d4 = 40.92 r 9 = -20.9376 d 9 = 0.2000 r 10 = 14.9502 d 10 = 1.5000 n d5 = 1.77250 ν d5 = 49.60 r 11 = -40.4131 d 11 _{= 0.6000 n d6 = 1.84666 ν d6} = 23.78 r 12 = 4.4044 d 12 = ( _{variable) r 13 = -27.9946 d 13 =} 1.5000 n d7 = 1.48749 ν d7 = 70.23 r 14 = -11.0236 d 14 = ( variable) r ₁₅ = 7.2319 _{(aspherical) d 15 = 1.5000 n d8 =} 1.58913 ν d8 = 61.14 r 16 = 50.0000 d 16 = 0.5000 r 17 = ∞ d 17 = 1.6000 n d9 = 1.54771 ν d9 = 62.84 r 18 = ∞ d 18 = 0.8000 _{r 19 = ∞ d 19 = 0.7500} n d10 = 1.51633 ν d10 = 64.14 r ₂₀ = ∞ d ₂₀ = 1.2055 r ₂₁ = ∞ Aspheric coefficient third surface K = 0 A ₄ = 5.6426 × 10 ^-4 A ₆ = -1.8014 × 10 ^-5 A ₈ = 7.8500 × 10 ^-7 A ₁₀ = 0.0000 8th page K = 0 A ₄ = -7.7896 × 10 ^-4 A ₆ = 5.8597 × 10 ^-6 A ₈ = -1.6485 × 10 ^-6 A ₁₀ = 0.0000 15th page K = 0 A ₆ = 2.0215 × 10 ^-5 A ₈ = -6.7754 × 10 ^-7 A ₁₀ = 0.0000 Zoom data (∞) WEST TE f (mm) 4.51243 8.69332 12.89908 F _NO 2.5234 3.5716 4.5401 2ω (°) 58.0 32.1 22.0 d ₆ 13.45457 4.75960 1.50000 d ₁₂ 1.62026 8.97143 15.03122 d ₁₄ 1.20000 0.60000 1.20000 Zoom data (20 cm) WEST TE d ₆ 13.45457 4.75960 1.50000 d ₁₂ 1.05019 6.89577 11.11046 d ₁₄ 1.77007 2.67566 5.12076

(Example 4) r ₁ = -90.5260 d ₁ = 0.7000 n _d1 = 1.69350 v _d1 = 53.21 r ₂ = 6.9963 (aspherical surface) d ₂ = 2.4000 r ₃ = 15.5562 d ₃ = 1.6000 n _d2 = 1.84666 v _{d2 = 23.78 r 4 = 35.4570 d} 4 = ( variable) r ₅ = ∞ _{(stop) d 5 = 1.2000 r 6 =} 6.8717 ( _{aspherical) d 6 = 1.7000 n d3 =} 1.80610 ν d3 = 40.92 r 7 = -32.7562 d _{7 = 0.2000 r 8 = 10.9848 d} 8 = 1.5000 n d4 = 1.77250 ν d4 = 49.60 r 9 = -57.7545 d 9 = 0.6000 n d5 = 1.84666 ν d5 = 23.78 r 10 = 4.8088 d 10 = ( variable) r ₁₁ = - _{23.4086 d 11 = 1.5000 n d6 =} 1.48749 ν d6 = 70.23 r 12 = -9.0966 d 12 = ( variable) r ₁₃ = 9.0801 _{(aspherical) d 13 = 1.5000 n d7 =} 1.58913 ν d7 = 61.14 r 14 = 50.0000 d 14 _{= 0.5000 r 15 = ∞ d 15} = 1.6000 n d8 = 1.54771 ν d8 = 62.84 r 16 = ∞ d 16 = 0.8000 r 17 = ∞ d 17 = 0.7500 n d9 = 1.51633 ν d9 = 64.14 r 18 = ∞ d 18 = 1.2048 r ₁₉ = ∞ aspheric coefficient second surface K = 0 A ₄ = -6.6705 × 10 ^-4 A ₆ = 1.8556 × 10 ^-5 A ₈ = -5.2741 × 10 ^-7 A ₁₀ = 0.0000 Surface 6 K = 0 A ₄ = -5.6147 × 10 ^-4 A ₆ = 1.9580 × 10 ^-5 A ₈ = -2.9306 × 10 ^-6 A ₁₀ = 0.0000 13th surface K = 0 A ₄ = -9.7948 × 10 ^-4 A ₆ = 4.3215 × 10 ^-5 A ₈ = -2.2531 × 10 ^-6 A ₁₀ = 0.0000 Zoom data (∞) WEST TE f (mm) 4.52161 8.70287 12.89602 F NO 2.5234 3.5716 4.5401 2ω (°) 57.9 32.1 21.9 d 4 14.08487 4.78144 1.50000 d 10 2.00000 8.61349 14.24568 d 12 1.20000 0.60000 1.20000 zoom data _{(20cm) WE ST TE d 4} 14.08487 4.78144 1.50000 d 10 1.58469 7.08728 11.33642 d ₁₂ 1.61531 2.12620 4.10926.

(Example 5) r ₁ = 1364.8623 d ₁ = 0.7000 n _d1 = 1.77250 v _d1 = 49.60 r ₂ = 7.7562 (aspherical surface) d ₂ = 2.7000 r ₃ = 9.1332 d ₃ = 1.6000 n _d2 = 1.84666 v _{d2 = 23.78 r 4 = 12.6368 d 4} = ( variable) r ₅ = ∞ _{(stop) d 5 = 1.2000 r 6 =} 4.5764 ( _{aspherical) d 6 = 1.7000 n d3 =} 1.80610 ν d3 = 40.92 r 7 = -12.3191 d 7 _{= 0.6000 n d4 = 1.84666 ν d4} = 23.78 r 8 = -29.2855 d 8 = 0.2000 r 9 = 10.1774 d 9 = 0.6000 n d5 = 1.84666 ν d5 = 23.78 r 10 = 3.2791 d 10 = ( variable) r ₁₁ = -22.4450 _{d 11 = 1.5000 n d6 = 1.48749} ν d6 = 70.23 r 12 = -8.1070 d 12 = ( variable) r ₁₃ = 12.7877 _{(aspherical) d 13 = 1.5000 n d7 =} 1.58913 ν d7 = 61.14 r 14 = -100.0000 d 14 _{= 0.5000 r 15 = ∞ d 15} = 1.6000 n d8 = 1.54771 ν d8 = 62.84 r 16 = ∞ d 16 = 0.8000 r 17 = ∞ d 17 = 0.7500 n d9 = 1.51633 ν d9 = 64.14 r 18 = ∞ d 18 = 1.1975 r ₁₉ = ∞ aspheric coefficient second surface K = 0 A ₄ = -3.2314 × 10 ^-4 A ₆ = 8.4338 × 10 ^-6 A ₈ = -2.1412 × 10 ^-7 A ₁₀ = 0.0000 Surface 6 K = 0 A ₄ = -1.2990 × 10 ^-3 A ₆ = -7.1492 × 10 ^-6 A ₈ = -5.0874 × 10 ^-6 A ₁₀ = 0.0000 13th page K = 0 A ₄ = -5.0625 × 10 ^-4 A ₆ = 1.8104 × 10 ^-5 A ₈ = -8.0922 × 10 ^-7 A ₁₀ = 0.0000 Zoom data (∞) WE ST TE f (mm) 4.52690 8.67687 12.88328 F _NO 2.5234 3.5716 4.5401 2ω (°) 57.8 32.1 22.0 d ₄ 14.72422 5.33805 1.50000 d ₁₀ 2.00000 8.54310 13.63534 d ₁₂ 1.20000 0.60000 1.20000 Zoom data (20 cm) WE ST TE d ₄ 14.72422 5.33805 1.50000d ₁₀ 1.65044 7.24626 11.15552 d ₁₂ 1.54956 1.89684 3.67982.

Example 6 r ₁ = 22.6195 d ₁ = 0.7000 n _d1 = 1.777250 v _d1 = 49.60 r ₂ = 6.0587 (aspheric surface) d ₂ = 2.7000 r ₃ = 6.9219 d ₃ = 1.6000 n _d2 = 1.84666 v _{d2 = 23.78 r 4 = 8.0657 d 4} = ( variable) r ₅ = ∞ _{(stop) d 5 = 1.2000 r 6 =} 4.0157 ( _{aspherical) d 6 = 1.7000 n d3 =} 1.69350 ν d3 = 53.21 r 7 = -70.6293 d 7 = 0.2000 r ₈ = 6.1392 d ₈ = 0.6000 n _d4 = 1.84666 v _d4 = 23.78 r ₉ = 2.9613 d ₉ = (variable) r ₁₀ = 9.5613 d ₁₀ = 1.5000 n _d5 = 1.48749 v _d5 = 70.23 r ₁₁ = 102.2252 d ₁₁ = _{(variable) r 12 = -8.1352 d 12 =} 1.5000 n d6 = 1.58913 ν d6 = 61.14 r 13 = -5.2208 ( _{aspherical) d 13 = 0.5000 r 14 =} ∞ d 14 = 1.6000 n d7 = 1.54771 ν d7 = 62.84 r ₁₅ = ∞ d ₁₅ = 0.8000 r ₁₆ = ｄ d ₁₆ = 0.7500 n _d8 = 1.51633 ν _d8 = 64.14 r ₁₇ = ｄ d ₁₇ = 1.2088 r ₁₈ = ∞ aspheric coefficient second surface K = 0 A ₄ = -2.1576 × 10 ^-4 A ₆ = 8.8126 × 10 ^-6 A ₈ = -4.3302 × 10 ^-7 A ₁₀ = 0.0000 Surface 6 K = 0 A ₄ = -1.5957 × 10 ^-3 A ₆ = 2.2500 × 10 ^-5 A ₈ = -1.4500 × 10 ^-5 A ₁₀ = 0.0000 Surface 13 K = 0 A ₄ = 1.7620 × 10 ^-3 A ₆ =- 4.1021 × 10 ^-5 A ₈ = 2.0115 × 10 ^-6 A ₁₀ = 0.0000 Zoom data (∞) WEST TE f (mm) 4.59300 8.65611 12.88288 F _NO 2.7298 3.3922 4.5086 2ω (°) 57.1 32.2 22.0 d ₄ 15.32489 3.88201 1.50000 d ₉ 2.00000 3.50000 11.75031 d ₁₁ 1.20000 3.15313 1.72785 Zoom data (20cm) WEST TE d ₄ 15.32489 3.88201 1.50000 d ₉ 1.77271 2.81389 10.15331 d ₁₁ 1.42729 3.83924 3.32485.

FIG. 7 is an aberration diagram for Example 1 upon focusing on an object point at infinity. In this aberration diagram, (a) is a wide-angle end, (b) is an intermediate state, (c) is a spherical aberration SA, an astigmatism AS, a distortion DT, and a chromatic aberration of magnification CC at a telephoto end.
Is shown. In the drawing, “FIY” represents the image height.

Next, the conditional expression (1) in each of the above embodiments is used.
The values of (8), (a) and (b) are shown below. Conditional expression Example 1 Example 2 Example 3 Example 4 (1) 2.7415 2.8774 2.6822 2.4491 (2) -0.9390 -0.5387 -1.0063 -0.6977 (3) -0.5975 -1.1000 -0.5724 -0.8040 (4) 0.1500 0.1500 0.1500 0.1500 (5) 0.1500 0.1500 0.1500 0.1500 (6) 1.1400 1.1400 1.1400 0.9400 (Y is mm) (Y = 5.0) (Y = 5.0) (Y = 5.0) (Y = 5.0) (7) 0.8000 0.8000 0.8000 0.8000 (Y is mm ) (Y = 5.0) (Y = 5.0) (Y = 5.0) (Y = 5.0) (8) × 10 ^-3 0.333 0.333 0.333 0.333 (a is μm) (a = 3.0) (a = 3.0) (a = (3.0) (a = 3.0) 3 layers 3 layers 3 layers 3 layers (a) 1.2728 1.4759 1.3736 1.2400 (b) 2.5660 2.5299 2.5530 2.5036 (x) 0.80752 0.80756 0.80678 0.80664 (y) 0.24 0.24 0.24 0.24 Conditional expression Example 5 Example 6 (1) 2.3271 2.0556 (2) -0.6733 -0.4677 (3) *** *** (4) *** *** (5) 0.1935 0.2400 (6) 1.0000 1.0000 (Y (Mm) (Y = 5.0) (Y = 5.0) (7) 0.6200 0.5000 (Y is mm) (Y = 5.0) (Y = 5.0) (8) × 10 ^-3 0.333 0.333 (a is μm) (a = 3.0) (a = 3.0) 3 stacks 3 stacks (a) 1.1248 0.9555 (b) 2.5047 2.3990 (x) 0.80518 0.80744 (y) 0.24 0.24

In each of the above embodiments, a low-pass filter F having a near-infrared sharp cut coat on the incident surface side is provided on the image side of the fourth lens unit G4 as shown in the figure.
This near-infrared sharp cut coat has a transmittance of at least 80% at a wavelength of 600 nm and a transmittance of 1 at a wavelength of 700 nm.
It is configured to be 0% or less. Specifically, for example, it is a multilayer film having the following 27 layers.
However, the design wavelength is 780 nm.

Base Material Material Physical Thickness (nm) λ / 4 １ First Layer Al ₂ O ₃ 58.96 0.50 Second layer TiO ₂ 84.19 1.00 Third layer SiO ₂ 134.14 1.00 Fourth layer TiO ₂ 84.19 1.00 Fifth layer SiO ₂ 134. 14 1.00 Sixth layer TiO ₂ 84.19 1.00 Seventh layer SiO ₂ 134.14 1.00 Eighth layer TiO ₂ 84.19 1.00 Ninth layer SiO ₂ 134.14 1.00 Tenth Layer TiO ₂ 84.19 1.00 11th layer SiO ₂ 134.14 1.00 12th layer TiO ₂ 84.19 1.00 13th layer SiO ₂ 134.14 1.00 14th layer TiO ₂ 84.19 1.00 15th layer SiO ₂ 178.41 1.33 16th layer TiO ₂ 101.03 1.21 17th layer SiO ₂ 167.67 1.25 18th layer TiO ₂ 96.82 1.15 19th layer SiO ₂ 147.55 1.05 20th layer TiO ₂ 84.19 1.00 21st layer SiO ₂ 160 .97 1.20 22 layer TiO ₂ 84.19 1.00 23rd layer SiO ₂ 154.26 1.15 24th layer TiO ₂ 95.13 1.13 25th layer SiO ₂ 160.97 1.20 second 26th layer TiO ₂ 99.34 1.18 27th layer SiO ₂ 87.19 0.65 ── Air.

The transmittance characteristics of the near-infrared sharp cut coat are as shown in FIG.

The color reproduction of the electronic image can be further improved by providing or coating a color filter on the emission surface side of the low-pass filter F, which reduces transmission of colors in a short wavelength range as shown in FIG. Is increasing the character.

Specifically, with this filter or coating, the ratio of the transmittance of the wavelength of 420 nm to the transmittance of the wavelength having the highest transmittance at a wavelength of 400 nm to 700 nm is 15% or more, and the transmittance of the highest wavelength is not less than 15%. The ratio of the transmittance at a wavelength of 400 nm to the transmittance is preferably 6% or less.

As a result, it is possible to reduce the difference between the recognition of the color of the human eye and the color of the captured and reproduced image. In other words, it is possible to prevent the deterioration of the image caused by the color on the short wavelength side which is hardly recognized by human eyes to be easily recognized by human eyes.

When the transmittance ratio at the wavelength of 400 nm is 6
%, The single-wavelength castle, which is hardly recognized by human eyes, is reproduced to a wavelength recognizable.
When the ratio of the transmittance at the wavelength of nm is smaller than 15%, the reproduction of the wavelength castle recognizable by humans becomes low, and the color balance becomes poor.

The means for limiting the wavelength is more effective in an image pickup system using a complementary color mosaic filter.

In each of the above embodiments, as shown in FIG. 9, the transmittance at a wavelength of 400 nm is 0%, the transmittance at 420 nm is 90%, and the transmittance peak is 10 at 440 nm.
The coating is 0%.

By multiplying the above action with the near-infrared sharp cut coat, the transmittance 99 at a wavelength of 450 nm is obtained.
% As a peak, the transmittance at 400 nm is 0%,
The transmittance at 420 nm is 80%, the transmittance at 600 nm is 82%, and the transmittance at 700 nm is 2%. Thereby, more faithful color reproduction is performed.

The low-pass filter F uses three types of filters having crystal axes in horizontal (= 0 °) and ± 45 ° directions, respectively, in the optical axis direction when projected on the image plane. , And for each, aμm horizontally,
Moiré is suppressed by shifting each in the ± 45 ° direction by SQRT (1/2) × a. Here, SQRT is a square route as described above and means a square root.

As shown in FIG. 10, a complementary color mosaic in which four color filters of cyan, magenta, yellow, and green (green) are provided in a mosaic pattern corresponding to the image pickup pixels on the image pickup surface I of the CCD. A filter is provided.
These four types of color filters are arranged in a mosaic so that each has approximately the same number, and adjacent pixels do not correspond to the same type of color filters.
Thereby, more faithful color reproduction becomes possible.

The complementary color mosaic filter is, specifically,
As shown in FIG. 10, it is preferable that the color filters are composed of at least four types of color filters, and the characteristics of the four types of color filters are as follows.

[0117] Each green color filter element G has a spectral strength peak at a wavelength G _P, yellow filter element Y _e has a spectral strength peak at a wavelength Y _P, each cyan filter element C to the wavelength C _P The magenta color filter M has a peak of the spectral intensity, and has peaks at the wavelengths M _P1 and M _P2 , and satisfies the following conditions.

[0118] _{510nm <G P <540nm 5nm <} Y P -G P <35nm -100nm <C P -G P <-5nm 430nm <M P1 <480nm 580nm <M P2 <640nm Furthermore, green, yellow, cyan The filter has an intensity of 80% or more at a wavelength of 530 nm with respect to the peak of each spectral intensity, and the magenta color filter has an intensity of 10% to 50% with a larger peak at a wavelength of 530 nm with respect to the peak of the spectral intensity. It is more preferable to have strength in order to enhance color reproducibility.

FIG. 11 shows an example of each wavelength characteristic in each of the above embodiments. Green color filter G is 5
It has a beak of spectral intensity at 25 nm. The yellow filter element Y _e has a spectral strength peak at 555 nm. The cyan color filter C has a peak of the spectral intensity at 510 nm. Magenta color filter M
Has peaks at 445 nm and 620 nm. In each color filter at 530 nm, G is 99% and _Ye is 95% with respect to the peak of each spectral intensity.
%, C is 97%, and M is 38%.

In the case of such a complementary color filter, a controller (not shown) (or a controller used in a digital camera) electrically performs the following signal processing to obtain a luminance signal Y = | G + M + _Ye + C | × 1/1. Four-color signal R−Y = | (M + Y _e ) − (G + C) | BY − = (M + C) − (G + Y _e ) | R (red), G (green), B (blue) Is converted to a signal.

By the way, the position of the near-infrared sharp cut coat described above may be any position on the optical path. The number of low-pass filters F may be two or one as described above.

FIG. 12 shows the details of the aperture stop in each embodiment. First group G1 and second group of imaging optical systems
At the stop position on the optical axis between the group G2 and the stop position, 0 stage, -1 stage,-
A turret 10 is provided which enables two-stage, -3 stage, and -4 stage brightness adjustments. The turret 10 has an opening 1A (a transmittance for a wavelength of 550 nm of 1 mm) having a circular, fixed space having a diameter of about 4 mm and having an aperture shape for adjusting 0 steps.
An aperture 1B made of a transparent parallel flat plate (having a transmittance of 99% for a wavelength of 550 nm) having a fixed aperture shape having an opening area of about half of the aperture area of the aperture 1A in order to perform -1 step correction. An ND filter having a circular opening having the same area as the opening 1B and having transmittances of 50%, 25%, and 13% for a wavelength of 550 nm is provided for correction to -2, -3, and -4 steps. Openings 1C, 1D, and 1E.

The light amount is adjusted by arranging one of the apertures at the stop position by rotating the turret 10 around the rotation axis 11.

Further, if the effective F number F _no 'is F _no '> a
When /0.4 μm, an ND filter having a transmittance of less than 80% for a wavelength of 550 nm is disposed in the opening. Specifically, in the first embodiment, the effective F-number at the telephoto end satisfies the above equation when the effective F-number of -2 stops relative to the time when the aperture is fully opened (0 stops) is 9.0. Yes, and the corresponding opening is 1C at that time. Thereby, the deterioration of the image due to the diffraction phenomenon of the stop is suppressed.

An example is shown in which a turret 10 'shown in FIG. 13A is used in place of the turret 10 shown in FIG. At the aperture stop position on the optical axis between the first group G1 and the second group G2 of the imaging optical system, 0, -1, 2 and -3 steps
Turret 10 'that can adjust the brightness of steps and -4 steps
Has been arranged. The turret 10 ′ has a fixed opening 1 A ′ having a circular shape with a diameter of about 4 mm for performing zero-step adjustment.
An opening 1B 'having a fixed opening shape having an opening area of about half of the opening area of the opening 1A' for correcting -1 step;
Further, the opening area becomes smaller in order, -2 steps, -3 steps,-
Openings 1C 'and 1 for which the shape for correcting in four steps is fixed.
D ′ and 1E ′. And turret 1
The light amount is adjusted by arranging one of the apertures at the stop position by rotating the rotation about the rotation axis 11 of 0 ′.

Also, optical low-pass filters having different spatial frequency characteristics are arranged at 1A 'to 1D' in the plurality of apertures. Then, as shown in FIG. 13B, the spatial frequency characteristic of the optical filter is set higher as the aperture diameter becomes smaller, thereby suppressing the deterioration of the image due to the diffraction phenomenon caused by stopping down. In addition,
Each curve in FIG. 13B shows the spatial frequency characteristic of only the low-pass filter, and the characteristics including the diffraction of each aperture are set to be equal.

The electronic image pickup apparatus of the present invention as described above is an image pickup apparatus which forms an object image with a zoom lens and receives the image with an image pickup device such as a CCD or a silver halide film to perform photographing. The present invention can be used for a video camera, a personal computer as an example of an information processing apparatus, a telephone, particularly a portable telephone which is easy to carry. Below, the embodiment is illustrated.

FIGS. 14 to 16 are conceptual diagrams of a configuration in which the zoom lens according to the present invention is incorporated in a photographing optical system 41 of a digital camera. 14 is a front perspective view showing the appearance of the digital camera 40, FIG. 15 is a rear perspective view of the same, and FIG. 16 is a sectional view showing the configuration of the digital camera 40. 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, and a flash 4.
6. When the shutter 45 including the liquid crystal display monitor 47 and the like, which is disposed above the camera 40, is pressed, the photographing is performed through the photographing optical system 41, for example, the zoom lens of the first embodiment in conjunction with the pressing. An object image formed by the photographing optical system 41 is formed on an imaging surface of the CCD 49 via an optical low-pass filter F provided with a near-infrared cut coat. The object image received by the CCD 49 is displayed as an electronic image on the liquid crystal display monitor 47 provided on the back of the camera via the processing means 51. Further, a recording means 52 is connected to the processing means 51 so that a captured electronic image can be recorded. The recording means 52 may be provided separately from the processing means 51, or may be configured to perform electronic recording and writing using a floppy (registered trademark) disk, a memory card, an MO, or the like. Also, CC
It may be configured as a silver halide camera in which a silver halide film is arranged in place of D49.

Further, a finder objective optical system 53 is arranged on the finder optical path 44. The object image formed by the finder objective optical system 53 is formed on a field frame 57 of a Porro prism 55 which is an image erecting member. Behind the polyprism 55, an eyepiece optical system 59 for guiding the erect image into the observer's eyeball E is disposed. Note that cover members 50 are arranged on the incident side of the photographing optical system 41 and the objective optical system 53 for the viewfinder, and on the exit side of the eyepiece optical system 59, respectively.

The digital camera 40 thus configured
Since the photographing optical system 41 is a zoom lens having a wide angle of view, a high zoom ratio, good aberration, good brightness, and a large back focus on which filters and the like can be arranged, high performance and low cost can be realized.

In the example of FIG. 16, a parallel flat plate is arranged as the cover member 50, but a lens having power may be used.

Next, a personal computer which is an example of an information processing apparatus in which the zoom lens of the present invention is incorporated as an objective optical system is shown in FIGS. 17 is a front perspective view of the personal computer 300 with the cover opened, FIG. 18 is a sectional view of the photographing optical system 303 of the personal computer 300, and FIG. 19 is a side view of the state of FIG. As shown in FIGS. 17 to 19, the personal computer 300 includes a keyboard 301 for the processor to input information from outside, an information processing unit and a recording unit not shown, and a monitor for displaying the information to the operator. 302, a photographing optical system 303 for photographing the image of the operator himself or the surroundings
And Here, the monitor 302 may be a transmissive liquid crystal display element that illuminates from behind with a backlight (not shown), a reflective liquid crystal display element that reflects and displays light from the front, a CRT display, or the like. Also,
In the figure, the photographing optical system 303 is built in the upper right of the monitor 302, but is not limited to that location, and may be anywhere around the monitor 302 or around the keyboard 301.

The photographing optical system 303 includes a photographing optical path 304
Above, an objective lens 112 including a zoom lens (not shown in the drawing) according to the present invention, and an image sensor chip 1 for receiving an image
62. These are built in the personal computer 300.

Here, an optical low-pass filter F is additionally attached on the image pickup element chip 162 to be integrally formed as the image pickup unit 160, and the objective lens 11
Since the second lens frame 113 can be fitted and attached to the rear end of the lens frame 113 with one touch, the centering of the objective lens 112 and the image sensor chip 162 and the adjustment of the surface interval are not required, and the assembly is simplified. . Further, a cover glass 114 for protecting the objective lens 112 is disposed at the tip of the lens frame 113. The drive mechanism of the zoom lens in the lens frame 113 is not shown.

The object image received by the image pickup device chip 162 is input to the processing means of the personal computer 300 via the terminal 166 and is displayed on the monitor 302 as an electronic image. The photographed image 305 of the person is shown. Also, this image 305
The information can be displayed on a personal computer of a communication partner from a remote place via the processing means, the Internet or a telephone.

Next, FIG. 20 shows a telephone as an example of an information processing apparatus in which the zoom lens of the present invention is incorporated as a photographic optical system, particularly a portable telephone which is easy to carry. FIG.
20A is a front view of the mobile phone 400, FIG. 20B is a side view, and FIG. 20C is a cross-sectional view of the photographing optical system 405.
As shown in FIGS. 20A to 20C, the mobile phone 40
0 is a microphone section 401 for inputting the voice of the operator as information.
A speaker unit 402 for outputting the voice of the other party, an input dial 403 for the operator to input information, a monitor 404 for displaying an image of the operator himself / herself and the other party and information such as a telephone number, An optical system 405, an antenna 406 for transmitting and receiving communication radio waves, image information and communication information,
Processing means (not shown) for processing input signals and the like. Here, the monitor 404 is a liquid crystal display element. In addition, in the drawings, the arrangement position of each component is not particularly limited to these. The photographing optical system 405 is a zoom lens according to the present invention (abbreviated in the drawing) disposed on the photographing optical path 407.
And an image sensor chip 162 for receiving an object image. These are mobile phones 4
00.

Here, an optical low-pass filter F is additionally attached on the image pickup element chip 162 to be integrally formed as an image pickup unit 160, and the objective lens 11
Since the second lens frame 113 can be fitted and attached to the rear end of the lens frame 113 with one touch, the centering of the objective lens 112 and the image sensor chip 162 and the adjustment of the surface interval are not required, and the assembly is simplified. . Further, a cover glass 114 for protecting the objective lens 112 is disposed at the tip of the lens frame 113. The drive mechanism of the zoom lens in the lens frame 113 is not shown.

The object image received by the imaging element chip 162 is input to a processing means (not shown) via a terminal 166, and is sent as an electronic image to the monitor 404, a monitor of a communication partner, or both. Is displayed. When transmitting an image to a communication partner, the processing unit includes a signal processing function of converting information of an object image received by the image sensor chip 162 into a transmittable signal.

The above-described electronic imaging device of the present invention can be configured, for example, as follows.

[1] In an electronic imaging apparatus including an imaging optical system and an electronic imaging device arranged on the image side of the imaging optical system, the imaging optical system includes an aspherical surface and is always fixed. An electronic imaging apparatus comprising: a final lens closest to the image side; and a focus lens group disposed immediately before the final lens on the object side and moving for focusing.

[2] The electronic imaging system according to item 1, wherein the imaging optical system has a lens group having a positive refractive power that moves only to the object side when zooming from the wide-angle end to the telephoto end. apparatus.

[3] The imaging optical system includes, in order from the object side, a first lens unit having a negative refractive power, and a positive lens having a positive refractive power that moves only to the object side when zooming from the wide-angle end to the telephoto end. 3. The electronic imaging device according to the above 1 or 2, further comprising a second lens group.

[4] The imaging optical system includes, in order from the object side, a first lens unit having a negative refractive power, and a plurality of positive refractions moving only to the object side when zooming from the wide-angle end to the telephoto end. 3. The electronic imaging apparatus according to the above item 1 or 2, further comprising a power lens group.

[5] In an electronic image pickup apparatus provided with an image forming optical system and an electronic image pickup device arranged on the image side of the image forming optical system, the image forming optical system may be a negative electrode arranged closest to the object side. A first lens group having a refractive power of at least three, and at least three lens groups disposed on the image side thereof, and
The mutual distance to the second lens group changes for zooming or focusing, and the lens group closest to the image is fixed at 1 mm.
An electronic imaging apparatus comprising an aspherical lens, and having an aperture stop that moves integrally with the lens group immediately after the first lens group on the image side during zooming.

[6] In an electronic image pickup apparatus including a zoom lens and an electronic image pickup device arranged on the image side of the zoom lens, the zoom lens is a first lens having a negative refractive power in order from the object side. Group, a second lens group having a positive refractive power, a third lens group having a positive refractive power, and a fourth lens group. By moving the third lens group toward the object side, An electronic imaging apparatus capable of focusing on a subject, wherein the fourth lens group includes a single fixed lens including an aspheric surface.

[7] In an electronic image pickup apparatus including a zoom lens and an electronic image pickup device arranged on the image side of the zoom lens, the zoom lens is a first lens having a negative refractive power in order from the object side. Group, a second lens group having a positive refractive power, a third lens group having a positive refractive power, and a fourth lens group. By moving the third lens group toward the object side, The second lens group includes one single lens including an aspherical surface, and a cemented lens including a positive lens and a negative lens in order from the object side. An electronic imaging apparatus, wherein the lens group includes one positive single lens.

[8] In an electronic image pickup apparatus including a zoom lens and an electronic image pickup element arranged on the image side of the zoom lens, the zoom lens is a first lens having a negative refractive power in order from the object side. Group, a second lens group having a positive refractive power, a third lens group having a positive refractive power, and a fourth lens group. By moving the third lens group toward the object side, a shorter distance The second lens group includes one positive lens including an aspheric surface and one negative lens, and the third lens group includes one positive single lens. An electronic imaging device, comprising:

[0148]

[9] The electronic imaging apparatus according to any one of [1] to [8], wherein the first lens group moves during zooming.

[10] The first group having the negative refractive power is provided closest to the object side, and is composed of four or more groups. The fourth group from the object side has a mutual distance during zooming. Is changed, the most image side group is constituted by a single aspheric single lens having a fixed positive refractive power, and has an aperture stop that moves integrally with the second group at the time of zooming. An electronic imaging apparatus comprising a zoom lens and an electronic imaging element satisfying the condition (1).

(1) 1.5 <L ₂ /Y<3.5 where L ₂ is the amount of movement from the wide-angle end to the telephoto end of the second lens unit, and Y is the diagonal length of the effective image pickup area of the image pickup device. is there.

[11] In order from the object side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, a third lens unit having a positive refractive power, and a fourth lens unit having a positive refractive power When the magnification is changed from the wide-angle end to the telephoto end at the time of focusing on an object point at infinity, the distance between the second unit and the third unit becomes large,
By extending the group toward the object side, it is possible to focus on an object at a closer distance. The fourth group is composed of a single aspheric single lens having a positive refractive power. An electronic image pickup apparatus comprising a zoom lens and an electronic image pickup element satisfying 2).

[0152] (2) -1.2 <however ^{_{ex P W / ex P T <}} 0, measured from the image plane at the wide angle end and the telephoto end during ^ex P _W, ^ex P _T respectively focused on an infinite object point Exit pupil position.

[12] In order from the object side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, a third lens unit having a positive refractive power, and a fourth lens unit having a positive refractive power When the magnification is changed from the wide-angle end to the telephoto end at the time of focusing on an object point at infinity, the distance between the second unit and the third unit becomes large,
By moving the group toward the object side, it is possible to focus on an object at a shorter distance. The second group is composed of one single lens including an aspheric surface in order from the object side, and a positive lens and a negative lens from the object side. The third unit is composed of one single lens having a positive refractive power, and the zoom lens and the electronic imaging device satisfy the following conditions (3) and (4). An electronic imaging device comprising:

(3) −1.5 <(R _2C1 + R _2C2 ) ·
( _{R2C2- R2C3} ) / ( _{R2C1- R2C2} ). ( _R2C2 +
_{R 2C3) <- 0.3 (4} ) 0.05 <t 2N / t 2 <0.3 , _{however, R 2C1, R 2C2, R} 2C3 is the first and second from the object side of the cemented lens in the second group And the radius of curvature of each of the third lens surfaces on the optical axis, t _2N is the thickness of the negative lens in the cemented lens of the second group on the optical axis, and t ₂ is the distance from the most object side surface of the second group. This is the thickness on the optical axis up to the surface closest to the image.

[13] In order from the object side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, a third lens unit having a positive refractive power, and a fourth lens unit having a positive refractive power Consisting of
When zooming from the wide-angle end to the telephoto end when focusing on an object point at infinity,
The distance between the second group and the third group increases, and it is possible to focus on a subject at a shorter distance by extending the third group toward the object side. It consists of one positive lens component including a spherical surface and one negative lens component,
An electronic imaging apparatus, wherein the third group includes a single lens having a positive refractive power, and includes a zoom lens and an electronic imaging element satisfying the following condition (5).

(5) 0.05 <t _2NI / t ₂ <0.3 where t _2NI is the thickness of the negative lens closest to the image side in the second group on the optical axis, and t ₂ is the thickness of the second group. This is the thickness on the optical axis from the surface closest to the object to the surface closest to the image.

[14] The first group is composed of, in order from the object side, a negative lens group composed of two negative lenses and a positive lens group composed of one positive lens. The electronic imaging device according to claim 1.

[15] The first group includes, in order from the object side, a negative lens group including two or less negative lenses and a positive lens group including one positive lens. 14. The electronic imaging apparatus according to any one of the above items 10 to 13, wherein one negative lens includes an aspheric surface.

[16] The electron according to any one of the above items 9 to 15, wherein the total thickness of each of the first and second groups satisfies the following conditions (6) and (7). Imaging device.

(6) 0.6 <t ₁ /Y<2.2 (7) 0.3 <t ₂ /Y<1.5 where t ₁ is the most image from the most object side surface of the first lens unit. Is the thickness on the optical axis up to the side surface, t ₂ is the thickness on the optical axis from the most object side surface to the most image side surface of the second group, and Y is the effective imaging of the image sensor. The diagonal length of the area.

[17] The transmittance at the wavelength of 600 nm is 80% or more and the transmittance at the wavelength of 700 nm is 10% on the object side with respect to the image pickup device behind the zoom lens.
17. The electronic imaging device according to any one of the items 9 to 16, further comprising a near-infrared sharp cut coat described below.

[18] The electronic imaging apparatus according to the above item 17, wherein the imaging element has a complementary color mosaic filter as a colorization filter.

[19] The complementary color mosaic filters are composed of at least four types of color filters, and are arranged in a mosaic shape such that each has substantially the same number and adjacent pixels do not correspond to the same type of color filters. 19. The electronic imaging device according to the above item 18, wherein

[20] The complementary color mosaic filter is composed of at least four types of color filters.
The electronic imaging device according to the above item 18 or 19, wherein the characteristics of the types of color filters are as follows.

[0165] Each green color filter element G has a spectral strength peak at a wavelength G _P, yellow filter element Y _e has a spectral strength peak at a wavelength Y _P, a color Buiruta C of cyan in the wavelength C _P The magenta color filter M has a peak of the spectral intensity, and has peaks at the wavelengths M _P1 and M _P2 , and satisfies the following conditions.

[0166] _{510nm <G P <540nm 5nm <} Y P -G P <35nm -100nm <C P -G P <-5nm 430nm <M P1 <480nm 580nm <M P2 <640nm [21] the green, yellow, cyan 530 nm for each spectral intensity peak
21. The magenta color filter has an intensity of 10% to 50% at a larger peak of a wavelength of 530 nm with respect to a peak of the spectral intensity of the magenta color filter. Electronic imaging device.

[22] An optical low-pass filter having a total thickness t _LPF on the optical axis that satisfies the following condition (8) is disposed closer to the object side than the image pickup device. Item 12. The electronic imaging device according to Item 1.

(8) 0.15 × 10 ³ <t _LPF / a <
0.45 × 10 ³ where a is the horizontal pixel pitch of the electronic image sensor.

[23] A plurality of openings having a fixed opening shape are provided, and one of the openings is provided between any one of the first group and the third object which is closest to the image side. 23. The electronic imaging apparatus according to any one of the above items 10 to 22, wherein the image plane illuminance is adjusted by being insertable into the optical path and being replaceable with another opening.

[24] A medium having a transmittance of less than 80% for a wavelength of 550 nm in some of the plurality of openings, and a transmittance for a wavelength of 550 nm of another part of the openings is 80% or more. 24. The electronic imaging apparatus according to the above item 23, wherein:

[25] The F number obtained from the focal length of the zoom lens and the diameter of the entrance pupil is F _no , and the F number when the transmittance at the wavelength of 550 nm in the aperture is T is F _no
Assuming that / √T is the effective F number F _no ′ and the horizontal pixel pitch of the electronic image sensor is a, F _no ′> a / 0.4 μm
In the case where the adjustment is performed so that the light amount becomes equivalent to the effective F-number, the aperture provided with the medium having the transmittance T of less than 80% for the wavelength of 550 nm is inserted into the optical path of the zoom lens. 23. The above-mentioned 23,
An electronic imaging device according to claim 1.

[26] The electronic imaging apparatus as described in any one of [23] to [25] above, wherein a plurality of the plurality of openings have optical low-pass filters having different spatial frequency characteristics.

[0173]

As is apparent from the above description, according to the present invention, it is possible to obtain a zoom lens which has a thin collapsible thickness, is excellent in storability, and has a high magnification and excellent imaging performance even in rear focus. In addition, it is possible to reduce the thickness of an electronic imaging device, particularly, a video camera or a digital camera.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a zoom lens used in an electronic imaging apparatus according to an embodiment of the present invention at a wide-angle end when focusing on an object point at infinity.

FIG. 2 is a sectional view of a zoom lens according to a second embodiment, which is similar to FIG.

FIG. 3 is a sectional view of a zoom lens according to a third embodiment, which is similar to FIG.

FIG. 4 is a sectional view of a zoom lens according to a fourth embodiment, which is similar to FIG.

FIG. 5 is a lens sectional view similar to FIG. 1 of a zoom lens according to a fifth embodiment.

FIG. 6 is a sectional view of a zoom lens according to a sixth embodiment, which is similar to FIG.

FIG. 7 is an aberration diagram for Example 1 upon focusing on an object point at infinity.

FIG. 8 is a diagram showing transmittance characteristics of an example of a near-infrared sharp cut coat.

FIG. 9 is a diagram illustrating transmittance characteristics of an example of a color filter provided on an emission surface side of a low-pass filter.

FIG. 10 is a diagram showing a color filter arrangement of a complementary color mosaic filter.

FIG. 11 is a diagram illustrating an example of a wavelength characteristic of a complementary color mosaic filter.

FIG. 12 is a perspective view illustrating details of an example of a brightness stop portion of each embodiment.

FIG. 13 is a diagram illustrating details of another example of a brightness stop portion in each embodiment.

FIG. 14 is a front perspective view showing the appearance of a digital camera incorporating the zoom lens according to the present invention.

FIG. 15 is a rear perspective view of the digital camera shown in FIG. 14;

FIG. 16 is a sectional view of the digital camera of FIG. 14;

FIG. 17 is a front perspective view of a personal computer in which a zoom lens according to the present invention is incorporated as an objective optical system with a cover opened.

FIG. 18 is a sectional view of a photographing optical system of a personal computer.

FIG. 19 is a side view of the state shown in FIG. 17;

FIG. 20 is a front view, a side view, and a cross-sectional view of a photographing optical system of a mobile phone in which a zoom lens according to the present invention is incorporated as an objective optical system.

[Explanation of symbols]

 G1 First group G2 Second group G3 Third group G4 Fourth group F Optical low-pass filter C Cover glass I Image plane E Observer eye 1A, 1B, 1C, 1D, 1E Opening 1A ', 1B', 1C ', 1D', 1E '... Aperture 10 ... Turret 10' ... Turret 11 ... Rotation axis 40 ... Digital camera 41 ... Shooting optical system 42 ... Shooting optical path 43 ... Finder optical system 44 ... For finder Optical path 45 ... Shutter 46 ... Flash 47 ... Liquid crystal display monitor 49 ... CCD 50 ... Cover member 51 ... Processing means 52 ... Recording means 53 ... Objective optical system for viewfinder 55 ... Poro prism 57 ... Field frame 59 ... Eyepiece optical system 112 ... Objective Lens 113 ... Mirror frame 114 ... Cover glass 160 ... Imaging unit 162 ... Imaging element chip 166 ... Terminal 300 ... Pasoko 301 ... Keyboard 302 ... monitor 303 ... imaging optical system 304 ... photographing optical path 305 ... image 400 ... mobile phone 401 ... microphone unit 402 ... speaker 403 ... input dial 404 ... monitor 405 ... imaging optical system 406 ... antenna 407 ... imaging optical path

Continued on front page F term (reference) 2H087 KA03 MA14 PA06 PA07 PA17 PA18 PB06 PB07 PB08 QA02 QA03 QA06 QA07 QA17 QA19 QA21 QA22 QA25 QA32 QA34 QA41 QA46 RA05 RA12 RA13 RA36 RA42 RA43 SA24 SB26 SA29 SB22 SB32 5C022 AA13 AB66 AC51 AC54 AC55

Claims (9)

[Claims] 1. An electronic imaging apparatus comprising: an imaging optical system; and an electronic imaging device disposed on an image side of the imaging optical system, wherein the imaging optical system includes an aspherical surface and is always fixed. An electronic image pickup apparatus comprising: a final lens closest to the image side; and a focus lens group disposed immediately before the object side with respect to the final lens and moving for focusing. 2. The electronic imaging apparatus according to claim 1, wherein the imaging optical system includes a lens unit having a positive refractive power that moves only to the object side when zooming from the wide-angle end to the telephoto end. apparatus. 3. The imaging optical system includes, in order from the object side, a first lens unit having a negative refractive power, and a first lens unit having a positive refractive power that moves only to the object side when zooming from the wide-angle end to the telephoto end. 3. The electronic imaging apparatus according to claim 1, comprising two lens groups. 4. The imaging optical system includes, in order from the object side, a first lens unit having a negative refractive power, and a plurality of positive refractive powers moving only to the object side when zooming from the wide-angle end to the telephoto end. The electronic imaging device according to claim 1, further comprising: a lens group. 5. An electronic imaging apparatus comprising: an imaging optical system; and an electronic imaging device arranged on an image side of the imaging optical system, wherein the imaging optical system has a negative arrangement disposed closest to the object side. A first lens group having a refractive power and at least three lens groups disposed on the image side thereof, and a mutual distance from the object side to a fourth lens group is changed for zooming or focusing. The lens group that is variable and is closest to the image side is fixedly constituted by one aspherical lens, and has an aperture stop that moves integrally with the lens group immediately after the image side of the first lens group during zooming. Electronic imaging device. 6. An electronic image pickup apparatus comprising a zoom lens and an electronic image pickup device arranged on the image side of the zoom lens, wherein the zoom lens has a first lens group having a negative refractive power in order from the object side. , A second lens group having a positive refractive power, a third lens group having a positive refractive power, and a fourth lens group, and the third lens group is extended toward the object side so as to be closer to the object. Wherein the fourth lens group comprises a single fixed lens including an aspheric surface. 7. An electronic image pickup apparatus comprising a zoom lens and an electronic image pickup device arranged on an image side of the zoom lens, wherein the zoom lens has a first lens group having a negative refractive power in order from the object side. , A second lens group having a positive refractive power, a third lens group having a positive refractive power, and a fourth lens group, and the third lens group is extended toward the object side so as to be closer to the object. Wherein the second lens group includes one single lens including an aspheric surface;
An electronic imaging apparatus comprising: a cemented lens composed of a positive lens and a negative lens in order from the object side; and wherein the third lens group includes one positive single lens. 8. An electronic image pickup apparatus comprising a zoom lens and an electronic image pickup device arranged on the image side of the zoom lens, wherein the zoom lens has a first lens group having a negative refractive power in order from the object side. And a second lens group having a positive refractive power, a third lens group having a positive refractive power, and a fourth lens group. By moving the third lens group toward the object side, The second lens group can focus on a subject, and the second lens group includes one positive lens including an aspheric surface;
An electronic imaging apparatus comprising: one negative lens; and the third lens group includes one positive single lens. 9. The electronic imaging apparatus according to claim 1, wherein the first lens group moves during zooming.