JP2011112992A - Zoom lens and imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom lens with which the thickness dimension of an imaging device is reduced, cost reduction effect by use of a plastic lens is enhanced, the productivity is excellent, and various aberrations are favorably corrected. <P>SOLUTION: The zoom lens consists of, in the order from an object, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a fourth lens group having a positive refractive power, and varies power by changing the intervals between the respective lens groups. The first lens group consists of, in the order from the object, a negative lens, a reflective optical element acting so as to bend an optical path by reflecting light beams, a negative lens, and a positive lens. The second lens group consists of, in the order from the object, a positive lens, a negative 2n lens made of plastic, and a positive 2p2 lens made of plastic, and satisfies a conditional expression: 0.1<fW/fc2<0.5, where fW is a focal distance of the entire system at the wide angle end, and fc2 is a synthetic focal distance of the 2n lens and the 2p2 lens. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a zoom lens that includes four lens groups and is suitable for a digital camera, a video camera, a portable terminal, and the like, and an imaging apparatus including the zoom lens.

  Conventionally, as an optical system that can reduce the thickness of a camera with a zoom ratio of about 3 times, the first lens group has a negative refractive power, and a reflective optical element such as a prism is used in the first lens group. A bending optical system that bends the optical axis is widely used. In order to achieve cost reduction, an optical system using a lens made of plastic is used. These are disclosed in patent publications (see, for example, Patent Documents 1 to 3).

Japanese Patent Laid-Open No. 2007-4020 JP 2004-361642 A JP 2006-119324 A

  However, Patent Document 1 uses 3 plastic lenses among the 8 lenses, and Patent Document 2 uses 3 plastic lenses among the 7 lenses. Is not obtained. In Patent Document 3, a plastic lens is used for each group. However, since there is a large amount of focus movement at the time of temperature change, and eccentricity / coaxial error sensitivity is large, adjustment / alignment, etc. Production technology is required, and practicality and productivity are low.

  The present invention has been made in view of such a problem, and can reduce the thickness of an imaging device such as a camera, has a high cost reduction effect by using a plastic lens, has good productivity, and has various aberrations corrected well. An object of the present invention is to provide a zoom lens and an image pickup apparatus including the zoom lens.

  The above object is achieved by the invention described below.

1. In order from the object side, the first lens group having negative refractive power, the second lens group having positive refractive power, the third lens group having negative refractive power, and the fourth lens group having positive refractive power In a zoom lens that is configured and performs zooming by changing the interval of each lens group,
The first lens group includes, in order from the object side, a negative 1n1 lens, a reflective optical element having a function of bending a light path by reflecting a light beam, a negative 1n2 lens, and a positive 1p lens. The second lens group includes, in order from the object side, a positive 2p1 lens, a negative 2n lens made of plastic, and a positive 2p2 lens made of plastic, and satisfies the following conditional expression: Zoom lens.

0.1 <fW / fc2 <0.5 (1)
However,
fW: focal length of the entire system at the wide angle end fc2: combined focal length of the 2n lens and the 2p2 lens 2. The zoom lens according to 1, wherein the 2n lens and the 2p2 lens are cemented with each other and satisfy the following conditional expression:

n2n-n2p2> 0.05 (2)
ν2p2-ν2n> 20 (3)
However,
n2n: Refractive index at the d-line of the 2n lens n2p2: Refractive index at the d-line of the 2p2 lens ν2n: Abbe number of the 2n lens ν2p2: Abbe number of the 2p2 lens 3. The zoom lens according to 1 or 2 above, wherein the 1n2 lens and the 1p lens are made of plastic and satisfy the following conditional expression.

| Fc1 / fW |> 20 (4)
However,
fc1: combined focal length of the 1n2 lens and the 1p lens fW: focal length of the entire system at the wide angle end 4. The zoom lens according to claim 1, wherein the 1n2 lens and the 1p lens are cemented with each other and satisfy the following conditional expression.

n1n2-n1p> 0.05 (5)
ν1p−ν1n2> 20 (6)
However,
n1n2: Refractive index at the d-line of the 1n2 lens n1p: Refractive index at the d-line of the 1p lens ν1p: Abbe number of the 1p lens ν1n2: Abbe number of the 1n2 lens 5. The zoom lens according to claim 1, wherein the first lens group satisfies the following conditional expression.

1.5 <| f1n1 / fW | <2.5 (7)
However,
f1n1: focal length of the 1n1 lens fW: focal length of the entire system at the wide angle end The zoom lens according to any one of 1 to 5, wherein the 1n1 lens satisfies the following conditional expression.

n1n1> 1.8 (8)
ν1n1> 30 (9)
However,
n1n1: Refractive index at the d-line of the 1n1 lens ν1n1: Abbe number of the 1n1 lens The zoom lens according to any one of 1 to 6, wherein the following conditional expression is satisfied.

1.5 <| f1 / fW | <2.5 (10)
However,
f1: focal length of the first lens group fW: focal length of the entire system at the wide angle end 8. The zoom lens according to any one of 1 to 7, wherein the following conditional expression is satisfied.

1.5 <β2T / β2W <2.5 (11)
However,
β2W: lateral magnification of the second lens group at the wide-angle end β2T: lateral magnification of the second lens group at the telephoto end The third lens group includes one negative lens made of plastic and having at least one surface formed as an aspherical surface, and satisfies the following conditional expression: The described zoom lens.

1.5 <| f3 / fW | <3.5 (12)
However,
f3: focal length of the third lens group fW: focal length of the entire system at the wide angle end 10. The zoom lens according to claim 1, wherein focusing is performed between infinity and a finite distance by moving the third lens group, and the following conditional expression is satisfied: .

0.5 <β34W <1.5 (13)
1.2 <β34T <1.8 (14)
However,
10. β34W: combined lateral magnification of the third lens group and the fourth lens group at the wide angle end β34T: combined lateral magnification of the third lens group and the fourth lens group at the wide angle end The fourth lens group is composed of one positive lens made of plastic and having at least one surface formed as an aspherical surface, and satisfies the following conditional expression: The described zoom lens.

1.5 <f4 / fW <3.0 (15)
However,
f4: focal length of the fourth lens group fW: focal length of the entire system at the wide angle end 12. The zoom lens according to any one of 1 to 11, wherein the following conditional expression is satisfied.

0.6 <fBW / fW <1.0 (16)
However,
fBW: Back focus at the wide-angle end (air equivalent length)
fW: focal length of the entire system at the wide-angle end The zoom lens according to any one of 1 to 12, wherein the first lens group and the fourth lens group are fixed at the time of zooming and focusing.

  14 14. An imaging apparatus comprising the zoom lens according to any one of 1 to 13.

  In the present invention, zooming is performed by moving the second lens group and the third lens group on the optical axis during zooming. On the wide-angle side, which is easily affected by the cosine fourth power rule, the relationship between the first lens group and the second lens group is a negative / positive retrofocus type arrangement, so that it is easy to secure the peripheral light amount and back focus. There are advantages. On the other hand, on the telephoto side, since the relationship between the first and second lens groups and the third and fourth lens groups is a positive / negative telephoto type, a compact optical system can be configured. In addition, since the aperture stop is present in the vicinity of the second lens group, the negative first and third lens groups existing before and after this are arranged substantially symmetrically with respect to the stop, thereby enabling good aberration correction. Become. By giving the fourth lens group positive refracting power, the divergent light beam from the negative third lens group can be converged, and good telecentricity can be obtained.

  In the case of the bending optical system as in the present invention, the height of the light incident on the reflecting optical element can be lowered by disposing the negative lens on the object side of the reflecting optical element, so that the thickness of the camera is reduced. Is possible. Furthermore, since this negative lens has a meniscus shape that is convex on the object side, the angle of light incident on the lens can be reduced.

  In the present invention, a prism is used for the reflective optical element, but the present invention is not limited to this. For example, a mirror may be used. However, the use of a prism is more advantageous for miniaturization because the diameter of the light beam passing through the reflecting optical system can be made smaller than when a mirror is used.

  By disposing a negative lens on the image side of the reflective optical element, the negative refractive power in the first lens group can be divided, so that the occurrence of distortion, astigmatism, lateral chromatic aberration, etc. occurring here is reduced. It becomes possible to suppress.

  Furthermore, chromatic aberration in the first lens group can be effectively corrected by disposing a positive lens in the first lens group. If the positive lens is disposed on the image side of the reflective optical element, the camera thickness can be reduced. Further, by joining the negative lens and the positive lens, it is possible to reduce the number of elements incorporated into the lens barrel, and to improve productivity.

  Since the positive and negative lenses located on the image side of the reflective optical element are made of plastic, an aspherical surface can be easily added, so distortion and astigmatism that occur here, spherical aberration on the telephoto side Etc. can be suppressed. Further, when an environmental change such as a temperature change occurs, a lens shape and a refractive index change with different signs occur, so that the focus movement and the optical performance change tend to be canceled out and can be relatively small. Furthermore, the plasticization of the lens contributes to the weight reduction of the lens unit.

  When the reflecting optical element of the first lens group is a prism, its volume is relatively large, and therefore the weight of the first lens group tends to be heavy. Therefore, it is preferable to fix the first lens group at the time of zooming or focusing, because the load on the drive mechanism is small. Further, since the first lens group has an action of bending the optical path, if the first lens group is moved at the time of zooming or focusing, the photographing range changes for each zoom position or object distance, which is not preferable in practical use.

  Since the second lens group is composed of positive, negative, and positive lenses in order from the object side, a triplet type arrangement is obtained, so that spherical aberration, coma aberration, longitudinal chromatic aberration, and the like can be corrected well. Furthermore, in the present invention, the second lens group is composed of two component elements by bonding two negative and positive lenses on the image side, so compared with the case where it is composed of three single lenses, Productivity is improved because the number of man-hours and error factors incorporated into the lens barrel are reduced.

  In addition, since this bonded lens is made of plastic, an aspherical surface can be easily added, so that spherical aberration, coma aberration, and the like occurring here can be suppressed. In addition, when environmental changes such as temperature changes occur, lens shapes and refractive index changes occur between lenses having mutually different refractive powers, so that focus movement and optical performance changes tend to be offset, It's small. Furthermore, the plasticization of the lens contributes to the weight reduction of the lens unit. In particular, since the second lens group moves during zooming, reducing the weight of the lens also reduces the load on the drive mechanism.

  Because of the positive refractive power of the second lens group, the width of the light beam passing through the third and subsequent groups becomes relatively narrow, so astigmatism and distortion aberration even if the third group and the fourth group are composed of a single lens. It is possible to sufficiently correct the above. If an aspherical surface is used, the correction effect is further enhanced.

  Employing plastic lenses for the third and fourth lens groups contributes to cost reduction and weight reduction. In particular, since the third lens group moves during zooming and focusing, the load on the actuator can be kept small. As described above, the diameter of the light beam passing through the third lens group and the fourth lens group is relatively thin, and the third lens group and the fourth lens group have negative and positive refractive powers, and therefore the temperature changes. The focal point movement and optical performance change at the time can be small.

  It is desirable to perform focusing between infinity and a finite distance by moving the third lens group. When trying to focus with the second lens group, the distance between the first lens group and the first lens group is insufficient on the telephoto side, making it difficult to focus. Further, when attempting to focus with the fourth lens group, since the magnification of the group is small, the amount of movement is increased, miniaturization of the optical system is hindered, and fluctuations in optical performance are also large. Therefore, it is easy to achieve downsizing and high performance of the optical system by using the third lens group that has a relatively high magnification and easily secures a space necessary for movement.

  If the fourth lens group is fixed at the time of zooming and focusing, there is an effect of improving the sealing performance in the vicinity of the image sensor and preventing the entry of dust and dirt. It also contributes to the simplification of the mechanism.

  By staying within the range of conditional expression (1), even if the plastic lens in the second lens group undergoes a refractive index change or a shape change due to an environmental change such as temperature or humidity, the focal position shift and optical performance change are reduced. It becomes possible to suppress.

  By keeping within the range of conditional expression (2), it is possible to satisfactorily correct spherical aberration, coma aberration, and the like in the entire zoom range on the cemented surface of the 2n lens and the 2p2 lens. In addition, the effect will further increase if it falls within the range of the following conditional expression.

n2n-n2p2> 0.07
By staying within the range of conditional expression (3), axial chromatic aberration over the entire zoom range can be favorably corrected in the cemented lens of the 2n lens and the 2p2 lens. In addition, the effect will further increase if it falls within the range of the following conditional expression.

ν2p2-ν2n> 25
By staying within the range of conditional expression (4), even if the plastic lens in the first lens group undergoes a refractive index change or a shape change due to environmental changes such as temperature and humidity, the focal position movement and optical performance change are reduced. It becomes possible to suppress.

  By staying within the range of conditional expression (5), astigmatism on the wide angle side, spherical aberration on the telephoto side, and the like can be favorably corrected on the cemented surface of the 1n2 lens and the 1p lens. In addition, the effect will further increase if it falls within the range of the following conditional expression.

n1n2-n1p> 0.07
By staying within the range of conditional expression (6), it is possible to satisfactorily correct the lateral chromatic aberration on the wide-angle side and the axial chromatic aberration on the telephoto side in the cemented lens of the 1n2 lens and the 1p lens. In addition, the effect will further increase if it falls within the range of the following conditional expression.

ν1p−ν1n2> 25
If the lower limit of conditional expression (7) is exceeded, the refractive power of the 1n1 lens will become too large, and distortion, astigmatism, etc. will become too large and correction by other lenses will be difficult. If the upper limit is exceeded, the refractive power of the 1n1 lens becomes too small, the diameter of the light beam passing through the reflection optical system becomes large, and the thickness dimension of the camera becomes large. Therefore, if it falls within the range of conditional expression (7), it is possible to achieve both good optical performance and downsizing of the optical system. In addition, the said effect will further increase if it falls within the range of the following conditional expression.

1.9 <| f1n1 / fW | <2.0
When the conditional expression (8) is satisfied, the refractive index of the lens is increased, so that a relatively gentle radius of curvature can be provided to obtain the same refractive power, and as a result, distortion and astigmatism can be suppressed. Will increase. In addition, the effect will further increase if it falls within the range of the following conditional expression.

n1n1> 1.85
When the conditional expression (9) is satisfied, the chromatic dispersion of the 1n1 lens is reduced, so that the lateral chromatic aberration can be suppressed. In addition, the effect will further increase if it falls within the range of the following conditional expression.

ν1n1> 40
When the lower limit of conditional expression (10) is exceeded, the refractive power of the first lens group becomes too strong, and distortion, astigmatism, and the like increase, and good optical performance cannot be obtained. Further, the optical performance deterioration is increased when a coaxial system / eccentric error occurs in the first lens group. If the upper limit is exceeded, the refractive power of the first lens group becomes too weak, leading to an increase in the size of the optical system. Therefore, if it falls within the range of conditional expression (10), good optical performance can be obtained. In addition, the effect will further increase if it falls within the range of the following conditional expression.

1.7 <| f1 / fW | <2.0
If the lower limit of conditional expression (11) is exceeded, the zooming effect in the second lens group will be too small, so that the refractive power of the third lens group will be increased to maintain the same size, and astigmatism will occur here. If the error sensitivity is increased or the optical performance is to be maintained, an increase in the amount of movement of the third lens group will increase the size of the optical system. If the upper limit is exceeded, an attempt is made to increase the zooming effect in the second lens group, and deterioration of spherical aberration, coma aberration, etc. and an increase in error sensitivity occur due to the excessive increase in the refractive power of the second lens group. In order to maintain the optical performance, increasing the amount of movement of the second lens group leads to an increase in the size of the optical system. Therefore, if it falls within the range of conditional expression (11), it is possible to achieve both good optical performance and downsizing of the optical system. In addition, the effect will further increase if it falls within the range of the following conditional expression.

2.0 <β2T / β2W <2.2
When the lower limit of conditional expression (12) is exceeded, the refractive power of the third lens group becomes too strong, and astigmatism and lateral chromatic aberration generated here increase, resulting in a decrease in optical performance. In addition, the optical performance is greatly deteriorated when a coaxial error or eccentricity error occurs. If the upper limit is exceeded, the refractive power of the third lens group becomes too weak, and the other lens groups are strengthened to maintain the same overall length, increasing various aberrations and error sensitivity, and providing good optical performance. As a result, the optical system is enlarged. Therefore, if it falls within the range of conditional expression (12), it is possible to achieve both good optical performance and downsizing of the optical system. In addition, the said effect will further increase if it falls within the range of the following conditional expression.

1.9 <| f3 / fW | <2.4
If the lower limit of conditional expressions (13) and (14) is exceeded, the combined lateral magnification of the third lens group and the fourth lens group at the wide-angle end / telephoto end becomes too small, and the amount of movement of the third lens group at the time of focusing Too much increases the size of the optical system. When the upper limit is exceeded, the combined lateral magnification of the third lens group and the fourth lens group becomes too large, and the amount of focus movement at the time of focusing becomes too large. Then, since the change of the focusing distance becomes large with respect to the discrete focusing movement, very fine lens driving is required. Further, since the focal point movement when the lens position changes due to a mechanism or control error becomes large, very high precision of parts and control are required, resulting in low productivity. Therefore, if it falls within the range of conditional expressions (13) and (14), it is possible to achieve both reduction in size of the optical system and good productivity. In addition, the said effect is further heightened by staying in the range of the following conditional expression.

1.1 <β34W <1.3
1.6 <β34T <1.7
If the conditional expression (15) is satisfied, it is possible to suppress the occurrence of distortion and the like occurring in the fourth lens group due to the refractive power of the fourth lens group becoming too strong below the lower limit, and also when the temperature changes Optical performance and focal point movement can also be suppressed. If the refractive power of the fourth lens group becomes too weak above the upper limit, it is possible to avoid an increase in the size of the optical system and a decrease in telecentricity. In addition, the said effect is further heightened by staying in the range of the following conditional expression.

2.0 <f4 / fW <2.5
If the lower limit of conditional expression (16) is exceeded, the back focus will be too short, the fourth lens group will be too close to the imaging surface, dust and scratches will be conspicuous, and at the same time the fourth lens group will move away from the aperture. This makes it difficult to correct aperture aberration such as astigmatism in this group. If the upper limit is exceeded, the position of the fourth lens group is too close to the object side and the moving range of the second lens group and the third lens group is narrowed, so that the refractive power of these lens groups becomes stronger than necessary. , Decrease optical performance or increase error sensitivity. Therefore, good optical performance can be obtained within the range of conditional expression (16). In addition, the said effect will further increase if it falls within the range of the following conditional expression.

  0.7 <fBW / fW <0.8

  According to the zoom lens of the present invention and the image pickup apparatus equipped with the zoom lens, the thickness dimension of the image pickup apparatus such as a camera is reduced, the cost reduction effect by using a plastic lens is high, the productivity is good, and various aberrations are also caused. There is an effect that it is corrected well.

It is a block diagram of an imaging device. It is sectional drawing of the zoom lens used for an imaging device. It is a block diagram which shows the internal structure of a mobile telephone. 2 is a lens configuration diagram at a wide angle end in Embodiment 1. FIG. FIG. 4 is an aberration diagram at a wide-angle end in Example 1. FIG. 4 is an aberration diagram at an intermediate focal length in Example 1. FIG. 3 is an aberration diagram at a telephoto end in Example 1. 6 is a lens configuration diagram at a wide-angle end in Embodiment 2. FIG. FIG. 6 is an aberration diagram at a wide-angle end in Example 2. FIG. 6 is an aberration diagram at an intermediate focal length in Example 2. FIG. 6 is an aberration diagram at a telephoto end in Example 2. 6 is a lens configuration diagram at a wide-angle end in Embodiment 3. FIG. FIG. 6 is an aberration diagram at a wide-angle end in Example 3. FIG. 6 is an aberration diagram at an intermediate focal length in Example 3. FIG. 6 is an aberration diagram at a telephoto end in Example 3. 6 is a lens configuration diagram at a wide angle end in Embodiment 4. FIG. FIG. 6 is an aberration diagram at a wide-angle end in Example 4. FIG. 6 is an aberration diagram at an intermediate focal length in Example 4. FIG. 10 is an aberration diagram at a telephoto end in Example 4. 10 is a lens configuration diagram at a wide-angle end in Embodiment 5. FIG. FIG. 10 is an aberration diagram at a wide-angle end in Example 5. FIG. 10 is an aberration diagram at an intermediate focal length in Example 5. FIG. 10 is an aberration diagram at a telephoto end in Example 5. 10 is a lens configuration diagram at a wide-angle end in Embodiment 6. FIG. FIG. 10 is an aberration diagram at a wide-angle end in Example 6. FIG. 10 shows aberration diagrams at the intermediate focal length in Example 6. FIG. 10 is an aberration diagram at a telephoto end in Example 6. 10 is a lens configuration diagram at a wide angle end according to Embodiment 7. FIG. FIG. 10 is an aberration diagram at a wide-angle end in Example 7. FIG. 10 shows aberration diagrams at the intermediate focal length in Example 7. FIG. 10 is an aberration diagram at a telephoto end in Example 7.

  An embodiment of an imaging apparatus equipped with the zoom lens of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram of the imaging apparatus.

  In FIG. 1, an imaging apparatus 100 includes a zoom lens 101, an imaging device 102, an A / D conversion unit 103, a control unit 104, an optical system driving unit 105, a timing generation unit 106, an imaging device driving unit 107, an image memory 108, and an image. The processing unit 109, the image compression unit 110, the image recording unit 111, the display unit 112, and the operation unit 113 are configured.

  The zoom lens 101 has a function of forming a subject image on the imaging surface of the image sensor 102.

  The image sensor 102 is composed of a CCD (charge coupled device) or a CMOS (complementary metal oxide semiconductor), photoelectrically converts incident light for each RGB, and outputs an analog signal thereof.

  The A / D conversion unit 103 converts an analog signal into digital image data.

  The control unit 104 controls each unit of the imaging device 100. The control unit 104 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Memory), and performs various processes in cooperation with various programs read from the ROM and expanded in the RAM. Execute.

  The optical system driving unit 105 controls the zoom lens 101 in zooming, focusing, exposure, and the like under the control of the control unit 104.

  The timing generator 106 outputs a timing signal for analog signal output.

  The image sensor drive unit 107 performs scanning drive control of the image sensor 102.

  The image memory 108 stores image data so as to be readable and writable.

  The image processing unit 109 performs various image processes on the image data.

  The image compression unit 110 compresses captured image data by a compression method such as JPEG (Joint Photographic Experts Group).

  The image recording unit 111 records image data on a recording medium such as a memory card set in a slot (not shown).

  The display unit 112 is a color liquid crystal panel or the like, and displays image data after shooting, a through image before shooting, various operation screens, and the like.

  The operation unit 113 includes a release button and various operation keys for setting various modes, and outputs information input by the user to the control unit 104.

  Here, the operation of the imaging apparatus 100 will be described. At the time of shooting, subject monitoring (through image display) and image shooting execution are performed. In monitoring, an image of the subject obtained through the zoom lens 101 is formed on the light receiving surface of the image sensor 102. The image sensor 102 is scan-driven by the timing generator 106 and the image sensor driver 107, and outputs an analog signal for one screen as a photoelectric conversion output corresponding to an optical image formed at regular intervals.

  The analog signal is appropriately gain-adjusted for each primary color component of RGB, and then converted into digital data by the A / D conversion unit 103. The digital data is subjected to color process processing including pixel interpolation processing and Y correction processing by the image processing unit 109 to generate a digital luminance signal Y and color difference signals Cb, Cr (image data), and the image memory. 108, the signal is periodically read out and the video signal is generated and output to the display unit 112.

  The display unit 112 functions as an electronic viewfinder in monitoring, and displays captured images in real time. In this state, zooming, focusing, exposure, and the like of the zoom lens 101 are set by driving the optical system driving unit 105 based on an operation input via the operation unit 113 by the user.

  In such a monitoring state, when the user operates the release button of the operation unit 113, still image data is captured. In response to the operation of the release button, one frame of image data stored in the image memory 108 is read out and compressed by the image compression unit 110. The compressed image data is recorded on a recording medium by the image recording unit 111.

  Note that the above-described imaging apparatus 100 is an example of an imaging apparatus suitable for the present invention, and the present invention is not limited to this.

  That is, the image pickup apparatus equipped with the zoom lens may be a digital still camera, a video camera, a mobile phone with an image pickup function, a PHS (Personal Handyphone System), a PDA (Personal Digital Assistant), or the like.

  Next, the zoom lens 101 will be described based on the lens cross-sectional view of FIG.

  The zoom lens 101 includes four groups of a first lens group G1, a second lens group G2, a third lens group G3, and a fourth lens group G4.

  The first lens group G1 includes a first lens L1 (1n1 lens), a reflective optical element P, and a cemented lens of a second lens L2 (1n2 lens) and a third lens L3 (1p lens), and is negative as a whole. Has refractive power. The reflective optical element P is a right angle prism, for example.

  The light beam from the object passes through the first lens L1, is reflected by the reflective optical element P, is bent at a right angle, and passes through the second lens L2 and the third lens L3. Accordingly, the optical axis OA of the first lens L1 and the optical axes OB of the second lens L2 and the third lens L3 intersect at substantially right angles. The first lens group G1 is fixed and does not move.

  The second lens group G2 includes a fourth lens L4 (2p1 lens) and a cemented lens of a fifth lens L5 (2n lens) and a sixth lens L6 (2p2 lens), and has a positive refractive power as a whole. ing. The second lens group G2 is driven by driving means (not shown) at the time of zooming, and moves forward and backward along the optical axis OB. A diaphragm S is disposed in front of the fourth lens L4.

  The third lens group G3 includes a single seventh lens L7, and has negative refractive power. The third lens group G3 is driven by driving means (not shown) at the time of zooming, and moves forward and backward along the optical axis OB. The third lens group G3 moves along the optical axis OB for focusing between infinity and a finite distance after zooming is completed.

  The fourth lens group G4 includes a single eighth lens L8, and has positive refractive power. The fourth lens group G4 is fixed and does not move.

  The parallel plate F is an IR cut filter, and the parallel plate CG is a seal glass of the image sensor. An optical low-pass filter may be used for the parallel plate F.

  As described above, the light image of the object is formed on the imaging surface I of the image sensor by the zoom lens including the first lens group G1, the second lens group G2, the third lens group G3, and the fourth lens group G4.

  Next, an example of the mobile phone 300 on which the imaging device 100 is mounted will be described with reference to FIG. FIG. 2 is a block diagram showing the internal configuration of the mobile phone.

  The mobile phone 300 has a control unit (CPU) 310 that performs overall control of each unit and executes a program corresponding to each process, an operation unit 320 for operating and inputting a number and the like with keys, and other predetermined data. System unit for displaying a video image captured on the wireless communication unit 340, a wireless communication unit 340 for realizing various information communication with an external server via the antenna 341, the imaging device 100, and the mobile phone 300. Storage unit (ROM) 360 storing necessary data such as various processing programs and terminal IDs, and various processing programs and data executed by the control unit 310, imaging data by the imaging apparatus 100, etc. And a temporary storage unit (RAM) 370 used as a work area for temporarily storing.

  Note that the control unit 104 of the imaging apparatus 100 and the control unit 310 of the mobile phone 300 are communicably connected. In such a case, the functions of the display unit 112 and the operation unit 113 shown in FIG. However, the operation of the imaging device 100 itself is basically the same. More specifically, an external connection terminal (not shown) of the imaging device 100 is connected to the control unit 310 of the mobile phone 300, and a release signal is transmitted from the mobile phone 300 side to the imaging device 100 side and obtained by imaging. Image signals such as luminance signals and color difference signals are output from the imaging apparatus 100 side to the control unit 310 side. Such an image signal can be stored in the storage unit 360 or displayed on the display unit 330 by the control system of the mobile phone 300, and further transmitted to the outside as video information via the wireless communication unit 340.

  In addition, as an image pickup apparatus equipped with a zoom lens, a camera module that has only an image pickup element mounted on a substrate and can be connected to an external device including a control unit, an image processing unit, a display unit, and the like by a connector or the like. It may be.

  Examples relating to the zoom lens of the present invention are shown below.

  In addition, the code | symbol shown below is as follows.

f: Focal length of the entire system F: F number ω: Half angle of view R: Radius of curvature d: Lens spacing n _d : Refractive index with respect to d-line ν _d : Abbe number *: Aspheric surface Is the origin, and the X axis is taken in the optical axis direction, and the height in the direction perpendicular to the optical axis is h.

However,
A _i : i-order aspherical coefficient R: radius of curvature K: conic constant In the lens configuration diagram, the sign is the same as in FIG. 2, and the arrow indicates the moving direction of the lens group at the time of zooming from the wide angle end. The reflective optical element P is represented as a parallel plate equivalent to the optical path length.

In the aspheric coefficient, a power of 10 (for example, 2.5 × 10 ⁻⁰² ) is expressed using E (for example, 2.5E-02).
Example 1
・ Surface data is shown below.
Surface number R (mm) d (mm) n _d ν _d
1 354.913 0.50 1.88300 40.8
2 5.656 1.30
3 ∞ 4.70 1.84666 23.8
4 ∞ 0.20
5 (*) 15.852 0.70 1.53048 55.7
6 3.568 1.61 1.60700 27.0
7 (*) 9.697 d1 (variable)
8 (Aperture) ∞ 0.00
9 10.724 0.86 1.72916 54.7
10 -27.487 0.64
11 (*) 7.201 1.21 1.60700 27.0
12 2.440 2.47 1.53048 55.7
13 (*) -11.697 d2 (variable)
14 (*) 6.051 0.70 1.53048 55.7
15 (*) 2.292 d3 (variable)
16 (*) 28.244 1.52 1.53048 55.7
17 (*) -4.973 0.30
18 ∞ 0.50 1.51633 64.2
19 ∞ 0.30
20 ∞ 0.70 1.51633 64.2
21 ∞
However, the second lens, the third lens, the fifth lens, the sixth lens, the seventh lens, and the eighth lens are plastic lenses.
・ Aspheric coefficient is shown below.
5th page
K = 0, A4 = -2.13001E-04, A6 = -3.41131E-04, A8 = 6.32015E-05, A10 = -2.87981E-06
7th page
K = 0, A4 = -5.38575E-04, A6 = -5.17967E-04, A8 = 1.33518E-04, A10 = -8.56603E-06
11th page
K = 0, A4 = -9.28994E-04, A6 = 1.62490E-04, A8 = -1.03216E-04, A10 = 2.12355E-05
Side 13
K = 0, A4 = -6.11208E-05, A6 = 6.30044E-04, A8 = -4.15214E-04, A10 = 8.93966E-05
14th page
K = 0, A4 = 3.38719E-03, A6 = 1.30643E-03, A8 = 1.03643E-04, A10 = -5.60931E-05
15th page
K = 0, A4 = -4.66213E-04, A6 = 1.95345E-03, A8 = -1.01735E-04, A10 = -8.02843E-05
16th page
K = 0, A4 = 2.19984E-04, A6 = 9.64171E-04, A8 = 4.25105E-05, A10 = -1.24736E-05,
A12 = 4.82809E-07
17th page
K = 0, A4 = 3.01160E-03, A6 = 9.94832E-04, A8 = -1.48848E-04, A10 = 4.02493E-05
A12 = -3.47535E-06
-Various data at the time of zooming are shown below.
Zoom ratio 2.86
Wide angle Medium Telephoto focal length 3.33 5.60 9.53
F number 3.25 4.40 5.72
Half angle of view 34.4 20.9 12.4
Image height 2.15 2.15 2.15
Total lens length 30.02 29.98 29.97
Back focus 2.60 2.56 2.55
d1 7.230 3.823 0.500
d2 1.700 1.996 3.855
d3 1.673 4.784 6.248
・ The zoom lens group data is shown below.
Group Start surface Focal length 1 1 -5.82
2 9 5.87
3 14 -7.43
4 16 8.10
・ The amount of focus movement due to temperature changes of plastic lenses is shown below.

Wide angle Medium telephoto f 3.33 5.60 9.53
Focus travel 0.022 0.037 0.085
-Values corresponding to the above conditional expressions are shown below.
fw / fc2 = 0.31
n2n-n2p2 = 0.08
ν2p2-ν2n = 28.6
| Fc1 / fw | = 83
n1n2-n1p = 0.08
ν1p−ν1n2 = 28.6
| F1n1 / fW | = 1.96
n1n1 = 1.883
ν1n1 = 40.8
| F1 / fW | = 1.75
β2T / β2W = 2.14
| F3 / fW | = 2.23
β34W = 1.23
β34T = 1.64
f4 / fW = 2.43
fBW / fW = 0.78
4 is a lens configuration diagram at the wide angle end, FIG. 5 is an aberration diagram at the wide angle end, FIG. 6 is an aberration diagram at an intermediate focal length, and FIG. 7 is an aberration diagram at the telephoto end.
(Example 2)
・ Surface data is shown below.
Surface number R (mm) d (mm) n _d ν _d
1 2905.338 0.50 1.88300 40.8
2 5.638 1.30
3 ∞ 4.70 1.84666 23.8
4 ∞ 0.20
5 (*) 14.155 0.70 1.49420 71.6
6 3.929 1.46 1.60700 27.0
7 (*) 9.040 d1 (variable)
8 (Aperture) ∞ 0.00
9 10.582 0.86 1.72916 54.7
10 -27.206 0.64
11 (*) 7.658 1.27 1.60700 27.0
12 2.459 2.43 1.53048 55.7
13 (*) -11.142 d2 (variable)
14 (*) 6.139 0.70 1.53048 55.7
15 (*) 2.337 d3 (variable)
16 (*) 29.775 1.53 1.53048 55.7
17 (*) -4.887 0.30
18 ∞ 0.50 1.51633 64.2
19 ∞ 0.30
20 ∞ 0.70 1.51633 64.2
21 ∞
However, the second lens, the third lens, the fifth lens, the sixth lens, the seventh lens, and the eighth lens are plastic lenses.
・ Aspheric coefficient is shown below.
5th page
K = 0, A4 = -1.33662E-05, A6 = -4.09164E-04, A8 = 7.80017E-05, A10 = -3.94946E-06
7th page
K = 0, A4 = -3.41312E-04, A6 = -5.61415E-04, A8 = 1.44623E-04, A10 = -9.89857E-06
11th page
K = 0, A4 = -1.01937E-03, A6 = 1.75816E-04, A8 = -1.13614E-04, A10 = 2.35596E-05
Side 13
K = 0, A4 = -2.30399E-04, A6 = 6.36402E-04, A8 = -4.14406E-04, A10 = 9.02313E-05
14th page
K = 0, A4 = 3.26117E-03, A6 = 1.50576E-03, A8 = -1.77488E-05, A10 = -1.82243E-05
15th page
K = 0, A4 = -3.12368E-04, A6 = 2.21320E-03, A8 = -3.00673E-04, A10 = 1.22516E-05
16th page
K = 0, A4 = 4.49683E-05, A6 = 1.02402E-03, A8 = 2.32375E-05, A10 = -1.08091E-05,
A12 = 4.66173E-07
17th page
K = 0, A4 = 2.94914E-03, A6 = 1.09433E-03, A8 = -1.59362E-04, A10 = 3.73839E-05,
A12 = -3.08611E-06
-Various data at the time of zooming are shown below.
Zoom ratio 2.86
Wide angle Medium Telephoto focal length 3.33 5.60 9.53
F number 3.23 4.37 5.70
Half angle of view 34.4 20.9 12.4
Image height 2.15 2.15 2.15
Total lens length 30.01 29.99 29.98
Back focus 2.59 2.57 2.56
d1 7.348 3.888 0.500
d2 1.709 1.929 3.693
d3 1.667 4.908 6.531
・ The zoom lens group data is shown below.
Group Start surface Focal length 1 1 -5.99
2 9 5.93
3 14 -7.60
4 16 8.04
-Values corresponding to the above conditional expressions are shown below.
fw / fc2 = 0.30
n2n-n2p2 = 0.08
ν2p2-ν2n = 28.6
| Fc1 / fw | = 113
n1n2-n1p = 0.11
ν1p−ν1n2 = 44.5
| F1n1 / fW | = 1.92
n1n1 = 1.883
ν1n1 = 40.8
| F1 / fW | = 1.80
β2T / β2W = 2.12
| F3 / fW | = 2.28
β34W = 1.21
β34T = 1.64
f4 / fW = 2.41
fBW / fW = 0.78
8 is a lens configuration diagram at the wide-angle end, FIG. 9 is an aberration diagram at the wide-angle end, FIG. 10 is an aberration diagram at an intermediate focal length, and FIG. 11 is an aberration diagram at the telephoto end.
(Example 3)
・ Surface data is shown below.
Surface number R (mm) d (mm) n _d ν _d
1 234.004 0.50 1.88300 40.8
2 5.672 1.30
3 ∞ 4.70 1.84666 23.8
4 ∞ 0.20
5 (*) 23.672 0.70 1.53048 55.7
6 3.898 1.53 1.60700 27.0
7 (*) 12.214 d1 (variable)
8 (Aperture) ∞ 0.00
9 11.018 1.30 1.72916 54.7
10 -58.389 0.20
11 (*) 5.530 1.45 1.64900 21.0
12 2.686 2.07 1.53048 55.7
13 (*) -15.476 d2 (variable)
14 (*) 9.233 0.70 1.53048 55.7
15 (*) 2.453 d3 (variable)
16 (*) 13.388 1.75 1.53048 55.7
17 (*) -4.979 0.30
18 ∞ 0.50 1.51633 64.2
19 ∞ 0.30
20 ∞ 0.70 1.51633 64.2
21 ∞
However, the second lens, the third lens, the fifth lens, the sixth lens, the seventh lens, and the eighth lens are plastic lenses.
・ Aspheric coefficient is shown below.
5th page
K = 0, A4 = 5.03347E-05, A6 = -1.63620E-04, A8 = 3.53948E-05, A10 = -1.65760E-06
7th page
K = 0, A4 = -3.04503E-04, A6 = -2.56076E-04, A8 = 7.42107E-05, A10 = -4.94017E-06
11th page
K = 0, A4 = -4.09427E-04, A6 = 1.13530E-04, A8 = -6.09444E-05, A10 = 1.19205E-05
Side 13
K = 0, A4 = 1.20807E-03, A6 = 4.03371E-04, A8 = -2.96729E-04, A10 = 6.97593E-05
14th page
K = 0, A4 = 1.15644E-03, A6 = 1.10275E-03, A8 = -4.45522E-04, A10 = 1.07226E-04
15th page
K = 0, A4 = -1.63615E-03, A6 = 3.91997E-04, A8 = -2.41646E-04, A10 = 2.61720E-05
16th page
K = 0, A4 = 1.14066E-04, A6 = 3.56640E-04, A8 = 1.64324E-05, A10 = -5.03334E-07,
A12 = -1.95142E-07
17th page
K = 0, A4 = 2.38036E-03, A6 = 6.91273E-04, A8 = -1.70728E-04, A10 = 3.32425E-05,
A12 = -2.19286E-06
-Various data at the time of zooming are shown below.
Zoom ratio 2.86
Wide angle Medium Telephoto focal length 3.33 5.60 9.53
F number 3.24 4.38 5.72
Half angle of view 34.4 20.9 12.4
Image height 2.15 2.15 2.15
Total lens length 30.02 29.98 29.97
Back focus 2.60 2.57 2.56
d1 7.260 3.805 0.500
d2 1.829 2.281 4.132
d3 1.519 4.522 5.977
・ The zoom lens group data is shown below.
Group Start surface Focal length 1 1 -5.90
2 9 5.78
3 14 -6.53
4 16 7.08
-Values corresponding to the above conditional expressions are shown below.
fw / fc2 = 0.35
n2n-n2p2 = 0.12
ν2p2−ν2n = 34.7
| Fc1 / fw | = 56
n1n2-n1p = 0.08
ν1p−ν1n2 = 28.6
| F1n1 / fW | = 1.98
n1n1 = 1.883
ν1n1 = 40.8
| F1 / fW | = 1.77
β2T / β2W = 2.15
| F3 / fW | = 1.96
β34W = 1.23
β34T = 1.64
f4 / fW = 2.13
fBW / fW = 0.78
12 is a lens configuration diagram at the wide-angle end, FIG. 13 is an aberration diagram at the wide-angle end, FIG. 14 is an aberration diagram at the intermediate focal length, and FIG. 15 is an aberration diagram at the telephoto end.
Example 4
・ Surface data is shown below.
Surface number R (mm) d (mm) n _d ν _d
1 389.782 0.50 1.88300 40.8
2 5.663 1.30
3 ∞ 4.70 1.84666 23.8
4 ∞ 0.20
5 (*) 22.698 0.70 1.49420 71.6
6 5.942 1.15 1.64900 21.0
7 (*) 12.791 d1 (variable)
8 (Aperture) ∞ 0.00
9 11.176 1.30 1.72916 54.7
10 -98.367 0.20
11 (*) 5.551 1.58 1.64900 21.0
12 2.989 1.89 1.49420 71.6
13 (*) -10.454 d2 (variable)
14 (*) 6.613 0.88 1.53048 55.7
15 (*) 2.124 d3 (variable)
16 (*) 11.443 1.88 1.53048 55.7
17 (*) -4.877 0.30
18 ∞ 0.50 1.51633 64.2
19 ∞ 0.30
20 ∞ 0.70 1.51633 64.2
21 ∞
However, the second lens, the third lens, the fifth lens, the sixth lens, the seventh lens, and the eighth lens are plastic lenses.
・ Aspheric coefficient is shown below.
5th page
K = 0, A4 = 2.91759E-04, A6 = -9.53113E-05, A8 = 2.65948E-05, A10 = -1.42604E-06
7th page
K = 0, A4 = -2.12454E-04, A6 = -1.34613E-04, A8 = 4.42124E-05, A10 = -3.17179E-06
11th page
K = 0, A4 = -5.03656E-04, A6 = 7.89132E-05, A8 = -4.83441E-05, A10 = 9.42146E-06
Side 13
K = 0, A4 = 1.20489E-03, A6 = 2.06434E-04, A8 = -2.10309E-04, A10 = 5.04667E-05
14th page
K = 0, A4 = -6.18306E-03, A6 = 1.28393E-03, A8 = -4.86965E-04, A10 = 1.25643E-04
15th page
K = 0, A4 = -1.50008E-02, A6 = -7.64968E-04, A8 = -3.18465E-05, A10 = -7.60650E-05
16th page
K = 0, A4 = 8.46396E-05, A6 = 1.81226E-04, A8 = 2.23381E-07, A10 = 3.14259E-06,
A12 = -3.35403E-07
17th page
K = 0, A4 = 2.61753E-03, A6 = 5.21423E-04, A8 = -1.54765E-04, A10 = 2.72149E-05,
A12 = -1.59882E-06
-Various data at the time of zooming are shown below.
Zoom ratio 2.86
Wide angle Medium Telephoto focal length 3.33 5.60 9.53
F number 3.27 4.42 5.77
Half angle of view 34.3 20.8 12.4
Image height 2.15 2.15 2.15
Total lens length 30.01 29.99 29.98
Back focus 2.60 2.57 2.56
d1 7.487 3.921 0.500
d2 1.704 2.149 3.904
d3 1.531 4.651 6.318
・ The zoom lens group data is shown below.
Group Start surface Focal length 1 1 -6.16
2 9 5.89
3 14 -6.33
4 16 6.71
-Values corresponding to the above conditional expressions are shown below.
fw / fc2 = 0.36
n2n-n2p2 = 0.15
ν2p2-ν2n = 50.6
| Fc1 / fw | = 308
n1n2-n1p = 0.15
ν1p−ν1n2 = 50.6
| F1n1 / fW | = 1.96
n1n1 = 1.883
ν1n1 = 40.8
| F1 / fW | = 1.85
β2T / β2W = 2.12
| F3 / fW | = 1.90
β34W = 1.21
β34T = 1.64
f4 / fW = 2.02
fBW / fW = 0.78
16 is a lens configuration diagram at the wide-angle end, FIG. 17 is an aberration diagram at the wide-angle end, FIG. 18 is an aberration diagram at the intermediate focal length, and FIG. 19 is an aberration diagram at the telephoto end.
(Example 5)
・ Surface data is shown below.
Surface number R (mm) d (mm) n _d ν _d
1 -785.973 0.50 1.88300 40.8
2 5.786 1.30
3 ∞ 4.70 1.84666 23.8
4 ∞ 0.20
5 ∞ 0.50 1.64769 33.8
6 5.082 1.30 1.92286 20.9
7 16.692 d1 (variable)
8 (Aperture) ∞ 0.00
9 12.600 1.30 1.72916 54.7
10 -18.954 0.20
11 (*) 10.589 1.44 1.60700 27.0
12 2.761 3.00 1.53048 55.7
13 (*) -8.524 d2 (variable)
14 (*) 5.571 0.82 1.53048 55.7
15 (*) 2.272 d3 (variable)
16 (*) 105.760 1.54 1.53048 55.7
17 (*) -4.183 0.30
18 ∞ 0.50 1.51633 64.2
19 ∞ 0.30
20 ∞ 0.70 1.51633 64.2
21 ∞
However, the fifth lens, the sixth lens, the seventh lens, and the eighth lens are plastic lenses.
・ Aspheric coefficient is shown below.
11th page
K = 0, A4 = -1.17083E-03, A6 = 4.21857E-04, A8 = -2.21123E-04, A10 = 3.73160E-05
Side 13
K = 0, A4 = 2.63212E-04, A6 = -2.85929E-04, A8 = 3.24691E-06, A10 = 8.03215E-06
14th page
K = 0, A4 = 3.13318E-03, A6 = -4.25315E-03, A8 = 1.50124E-03, A10 = -1.96844E-04
15th page
K = 0, A4 = 2.94871E-04, A6 = -7.54686E-03, A8 = 2.67488E-03, A10 = -4.86119E-04
16th page
K = 0, A4 = 2.74709E-03, A6 = -3.63959E-05, A8 = 1.72786E-04, A10 = -2.32559E-05,
A12 = 1.23684E-06
17th page
K = 0, A4 = 4.02171E-03, A6 = 1.48731E-03, A8 = -2.95817E-04, A10 = 4.26501E-05,
A12 = -1.97097E-06
-Various data at the time of zooming are shown below.
Zoom ratio 2.87
Wide angle Medium Telephoto focal length 3.33 5.70 9.57
F number 3.26 4.46 5.74
Half angle of view 34.5 20.4 12.4
Image height 2.15 2.15 2.15
Total lens length 31.03 30.98 30.95
Back focus 2.61 2.56 2.53
d1 7.722 3.985 0.500
d2 1.700 1.866 3.502
d3 1.791 5.362 7.212
・ The zoom lens group data is shown below.
Group Start surface Focal length 1 1 -6.33
2 9 6.22
3 14 -7.91
4 16 7.62
・ The amount of focus movement due to temperature changes of plastic lenses is shown below.

Wide angle Medium telephoto f 3.33 5.70 9.57
Focus travel 0.017 0.028 0.068
-Values corresponding to the above conditional expressions are shown below.
fw / fc2 = 0.29
n2n-n2p2 = 0.08
ν2p2-ν2n = 28.6
n1n2-n1p = 0.28
ν1p−ν1n2 = 13.0
| F1n1 / fW | = 1.95
n1n1 = 1.883
ν1n1 = 40.8
n1n2-n1p = 0.28
| F1 / fW | = 1.90
β2T / β2W = 2.07
| F3 / fW | = 2.38
β34W = 1.18
β34T = 1.64
f4 / fW = 2.29
fBW / fW = 0.78
20 is a lens configuration diagram at the wide-angle end, FIG. 21 is an aberration diagram at the wide-angle end, FIG. 22 is an aberration diagram at the intermediate focal length, and FIG. 23 is an aberration diagram at the telephoto end.
(Example 6)
・ Surface data is shown below.
Surface number R (mm) d (mm) n _d ν _d
1-131.729 0.50 1.88300 40.8
2 5.583 1.30
3 ∞ 4.70 1.84666 23.8
4 ∞ 0.20
5 (*) 27.477 0.70 1.53048 55.7
6 3.776 2.67 1.60700 27.0
7 (*) 15.310 d1 (variable)
8 (Aperture) ∞ 0.00
9 10.328 1.30 1.72916 54.7
10 17.185 0.20
11 (*) 5.395 0.57 1.60700 27.0
12 2.555 2.94 1.53048 55.7
13 (*) -8.251 d2 (variable)
14 (*) 8.335 0.87 1.53048 55.7
15 (*) 2.574 d3 (variable)
16 (*) 43.519 1.57 1.53048 55.7
17 (*) -4.437 0.30
18 ∞ 0.50 1.51633 64.2
19 ∞ 0.30
20 ∞ 0.70 1.51633 64.2
21 ∞
However, the second lens, the third lens, the fifth lens, the sixth lens, the seventh lens, and the eighth lens are plastic lenses.
・ Aspheric coefficient is shown below.
5th page
K = 0, A4 = 7.73556E-05, A6 = -7.57323E-05, A8 = 2.06366E-05, A10 = -1.14052E-06
7th page
K = 0, A4 = -2.83627E-04, A6 = -7.25778E-05, A8 = 2.94957E-05, A10 = -1.90543E-06
11th page
K = 0, A4 = -7.13523E-04, A6 = 1.68569E-04, A8 = -6.62639E-05, A10 = 1.01395E-05
Side 13
K = 0, A4 = 1.37010E-03, A6 = -4.46128E-05, A8 = -4.29645E-05, A10 = 7.94872E-06
14th page
K = 0, A4 = 2.57769E-03, A6 = -6.43291E-04, A8 = 4.74865E-04, A10 = -1.00194E-04
15th page
K = 0, A4 = 1.64110E-03, A6 = -2.02728E-03, A8 = 1.48154E-03, A10 = -3.58079E-04
16th page
K = 0, A4 = -9.86449E-05, A6 = 7.21014E-04, A8 = 2.53290E-05, A10 = -4.89832E-06,
A12 = 2.51475E-07
17th page
K = 0, A4 = 2.60067E-03, A6 = 1.17422E-03, A8 = -2.19742E-04, A10 = 3.81187E-05,
A12 = -2.04494E-06
-Various data at the time of zooming are shown below.
Zoom ratio 2.86
Wide angle Medium Telephoto focal length 3.33 5.60 9.53
F number 3.26 4.46 5.74
Half angle of view 34.4 20.8 12.4
Image height 2.15 2.15 2.15
Total lens length 33.14 33.09 33.12
Back focus 2.59 2.54 2.57
d1 7.764 4.141 0.500
d2 3.224 3.593 5.662
d3 1.628 4.882 6.453
・ The zoom lens group data is shown below.
Group Start surface Focal length 1 1 -5.78
2 9 6.52
3 14 -7.41
4 16 7.68
・ The amount of focus movement due to temperature changes of plastic lenses is shown below.

Wide angle Medium telephoto f 3.33 5.60 9.53
Focus travel 0.070 0.128 0.246
-Values corresponding to the above conditional expressions are shown below.
f2p1 / f2 = 5.04
| F1n1 / fW | = 1.82
n1n1 = 1.883
ν1n1 = 40.8
| Fc1 / fw | = 112
n1n2-n1p = 0.08
ν1p−ν1n2 = 28.6
| F1 / fW | = 1.745
β2T / β2W = 2.12
fw / fc2 = 0.45
n2n-n2p2 = 0.08
ν2p2-ν2n = 28.6
| F3 / fW | = 2.23
β34W = 1.21
β34T = 1.64
f4 / fW = 2.31
fBW / fW = 0.78
24 is a lens configuration diagram at the wide-angle end, FIG. 25 is an aberration diagram at the wide-angle end, FIG. 26 is an aberration diagram at the intermediate focal length, and FIG. 27 is an aberration diagram at the telephoto end.
(Example 7)
・ Surface data is shown below.
Surface number R (mm) d (mm) n _d ν _d
1 -85.778 0.50 1.88300 40.8
2 5.560 1.30
3 ∞ 4.70 1.84666 23.8
4 ∞ 0.20
5 (*) -87.045 0.70 1.53048 55.7
6 6.269 1.55 1.60 700 27.0
7 (*) -85.311 d1 (variable)
8 (Aperture) ∞ 0.00
9 9.577 2.90 1.72916 54.7
10 -25.058 1.19
11 (*) 13.763 1.50 1.60700 27.0
12 2.921 3.00 1.53048 55.7
13 (*) -24.381 d2 (variable)
14 (*) 7.447 0.76 1.53048 55.7
15 (*) 2.998 d3 (variable)
16 (*) 9.042 1.95 1.53048 55.7
17 (*) -6.044 0.30
18 ∞ 0.50 1.51633 64.2
19 ∞ 0.30
20 ∞ 0.70 1.51633 64.2
21 ∞
However, the second lens, the third lens, the fifth lens, the sixth lens, the seventh lens, and the eighth lens are plastic lenses.
・ Aspheric coefficient is shown below.
5th page
K = 0, A4 = 1.54129E-03, A6 = -4.31232E-04, A8 = 7.44685E-05, A10 = -4.11112E-06
7th page
K = 0, A4 = 7.36731E-04, A6 = -3.82661E-04, A8 = 7.26827E-05, A10 = -4.43528E-06
11th page
K = 0, A4 = -1.14015E-03, A6 = 7.51814E-05, A8 = -4.36980E-05, A10 = 6.78758E-06
Side 13
K = 0, A4 = -1.52521E-03, A6 = 7.20968E-04, A8 = -3.12835E-04, A10 = 4.94581E-05
14th page
K = 0, A4 = 2.39330E-03, A6 = 3.27822E-03, A8 = -9.84711E-04, A10 = 1.40934E-04
15th page
K = 0, A4 = 4.05069E-04, A6 = 5.59552E-03, A8 = -1.96634E-03, A10 = 3.45034E-04
16th page
K = 0, A4 = -8.81514E-04, A6 = 7.85544E-04, A8 = -1.20007E-04, A10 = 1.09380E-05,
A12 = -5.51892E-07
17th page
K = 0, A4 = 2.17404E-03, A6 = 8.21103E-04, A8 = -1.64393E-04, A10 = 1.44360E-05,
A12 = -6.35708E-07
-Various data at the time of zooming are shown below.
Zoom ratio 2.86
Wide angle Medium Telephoto focal length 3.33 5.60 9.53
F number 3.26 4.46 5.74
Half angle of view 34.4 20.8 12.4
Image height 2.15 2.15 2.15
Total lens length 35.85 35.83 35.84
Back focus 2.61 2.58 2.59
d1 9.239 4.863 0.500
d2 1.700 2.089 4.824
d3 1.651 5.638 7.266
・ The zoom lens group data is shown below.
Group Start surface Focal length 1 1 -6.92
2 9 7.88
3 14 -10.05
4 16 7.15
・ The amount of focus movement due to temperature changes of plastic lenses is shown below.

Wide angle Medium telephoto f 3.33 5.60 9.53
Focus travel 0.004 0.006 0.043
-Values corresponding to the above conditional expressions are shown below.
f2p1 / f2 = 1.25
| F1n1 / fW | = 1.77
n1n1 = 1.883
ν1n1 = 40.8
| Fc1 / fw | = 23
n1n2-n1p = 0.08
ν1p−ν1n2 = 28.6
| F1 / fW | = 2.08
β2T / β2W = 2.17
fw / fc2 = 0.13
n2n-n2p2 = 0.08
ν2p2-ν2n = 28.6
| F3 / fW | = 3.02
β34W = 0.99
β34T = 1.31
f4 / fW = 2.15
fBW / fW = 0.78
28 is a lens configuration diagram at the wide-angle end, FIG. 29 is an aberration diagram at the wide-angle end, FIG. 30 is an aberration diagram at the intermediate focal length, and FIG. 31 is an aberration diagram at the telephoto end.

G1 1st lens group G2 2nd lens group G3 3rd lens group G4 4th lens group L1 1st lens L2 2nd lens L3 3rd lens L4 4th lens L5 5th lens L6 6th lens L7 7th lens L8 1st lens 8 lenses S Aperture OA, OB Optical axis F, CG Parallel plate I Imaging surface

Claims (14)

In order from the object side, the first lens group having negative refractive power, the second lens group having positive refractive power, the third lens group having negative refractive power, and the fourth lens group having positive refractive power In a zoom lens that is configured and performs zooming by changing the interval of each lens group,
The first lens group includes, in order from the object side, a negative 1n1 lens, a reflective optical element having a function of bending a light path by reflecting a light beam, a negative 1n2 lens, and a positive 1p lens. The second lens group includes, in order from the object side, a positive 2p1 lens, a negative 2n lens made of plastic, and a positive 2p2 lens made of plastic, and satisfies the following conditional expression: Zoom lens.
0.1 <fW / fc2 <0.5
However,
fW: focal length of the entire system at the wide angle end fc2: combined focal length of the 2n lens and the 2p2 lens The zoom lens according to claim 1, wherein the 2n lens and the 2p2 lens are cemented with each other and satisfy the following conditional expression.
n2n-n2p2> 0.05
ν2p2-ν2n> 20
However,
n2n: Refractive index at the d-line of the 2n lens n2p2: Refractive index at the d-line of the 2p2 lens ν2n: Abbe number of the 2n lens ν2p2: Abbe number of the 2p2 lens The zoom lens according to claim 1 or 2, wherein the 1n2 lens and the 1p lens are made of plastic and satisfy the following conditional expression.
| Fc1 / fW |> 20
However,
fc1: combined focal length of the 1n2 lens and the 1p lens fW: focal length of the entire system at the wide angle end The zoom lens according to claim 1, wherein the 1n2 lens and the 1p lens are cemented with each other and satisfy the following conditional expression.
n1n2-n1p> 0.05
ν1p−ν1n2> 20
However,
n1n2: Refractive index at the d-line of the 1n2 lens n1p: Refractive index at the d-line of the 1p lens ν1p: Abbe number of the 1p lens ν1n2: Abbe number of the 1n2 lens The zoom lens according to claim 1, wherein the first lens group satisfies the following conditional expression.
1.5 <| f1n1 / fW | <2.5
However,
f1n1: focal length of the 1n1 lens fW: focal length of the entire system at the wide angle end The zoom lens according to claim 1, wherein the 1n1 lens satisfies the following conditional expression.
n1n1> 1.8
ν1n1> 30
However,
n1n1: Refractive index at the d-line of the 1n1 lens ν1n1: Abbe number of the 1n1 lens The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
1.5 <| f1 / fW | <2.5
However,
f1: focal length of the first lens group fW: focal length of the entire system at the wide angle end The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
1.5 <β2T / β2W <2.5
However,
β2W: lateral magnification of the second lens group at the wide angle end β2T: lateral magnification of the second lens group at the telephoto end 9. The third lens group according to claim 1, wherein the third lens group is made of a single negative lens made of plastic and having at least one surface formed as an aspheric surface, and satisfies the following conditional expression. Zoom lens described in 1.
1.5 <| f3 / fW | <3.5
However,
f3: focal length of the third lens group fW: focal length of the entire system at the wide-angle end 10. The zoom according to claim 1, wherein focusing is performed between infinity and a finite distance by moving the third lens group, and the following conditional expression is satisfied: 10. lens.
0.5 <β34W <1.5
1.2 <β34T <1.8
However,
β34W: combined lateral magnification of the third lens group and the fourth lens group at the wide angle end β34T: combined lateral magnification of the third lens group and the fourth lens group at the wide angle end The said 4th lens group consists of one sheet of positive lenses which consist of plastics and at least 1 surface was formed in the aspherical surface, and satisfy | fills the following conditional expressions, The one of Claims 1-10 characterized by the above-mentioned. Zoom lens described in 1.
1.5 <f4 / fW <3.0
However,
f4: focal length of the fourth lens group fW: focal length of the entire system at the wide angle end The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
0.6 <fBW / fW <1.0
However,
fBW: Back focus at the wide-angle end (air equivalent length)
fW: focal length of the entire system at the wide angle end   The zoom lens according to any one of claims 1 to 12, wherein the first lens group and the fourth lens group are fixed at the time of zooming and focusing.   An imaging apparatus comprising the zoom lens according to claim 1.

Images