JP2006119319A - Variable power optical system, imaging lens device and digital equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable power optical system having a variable power ratio of approximately two to three times and also having a small size and high accuracy, and to provide an imaging lens device having the variable power optical system, and digital equipment equipped with the imaging lens device. <P>SOLUTION: The variable power optical system comprising a plurality of lens groups and varies a power by changing distances between the lens groups in the direction of its optical axis. The variable power optical system includes, in order from the object side, two or more lens groups whose optical power are negative and positive. Where an angle to a normal set in an image plane of the main light ray at a wide angle end and that at a telephoto end are represented by α<SB>W</SB>and α<SB>T</SB>respectively, the absolute value of a difference between them satisfies the following relation: 15°<¾α<SB>W</SB>-α<SB>T</SB>¾<30°. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention includes a variable magnification optical system that includes a plurality of lens groups and performs zooming by changing the interval between the lens groups in the optical axis direction, an imaging lens device including the zooming optical system, and the imaging lens device. It relates to the installed digital equipment.

  In recent years, mobile phones and personal digital assistants (PDAs) have become widespread, and specifications for incorporating compact digital still camera units and digital video units into these devices have become common. Since these devices are severely limited in size and cost, they have a small image sensor with a small number of pixels and a single-focus optical system consisting of about 1 to 3 plastic lenses compared to digital still cameras that are independent products. An imaging lens device provided is generally used.

  However, since the magnification of the single-focus optical system is similar to that of visual observation, the object that can be photographed is limited to that near the photographer. In this respect, with the rapid increase in the number of pixels and the functionality of image sensors, it can be mounted on a mobile phone or the like that can handle a high pixel image sensor and can photograph a subject away from the photographer. A compact variable magnification optical system is required.

As a variable magnification optical system having a compact configuration, for example, in Patent Document 1, a first lens group having negative optical power, a second lens group having positive optical power, which are sequentially arranged from the object side, A four-component variable magnification optical system composed of a third lens group and a fourth lens group having positive optical power has been proposed. In the technique disclosed in Patent Document 1, in order to shorten the optical total length, the lens group (fourth lens group) closest to the image side is always fixed, and the lens group (third lens group) immediately before this is focused. So-called rear focus type that moves for the purpose is adopted. Furthermore, the lens element is thinned to achieve a reduction in thickness when retracted.
JP 2002-90624 A

  However, a portable terminal such as a cellular phone has a severe impact resistance required, and it is difficult to retract. Furthermore, in the variable magnification optical system according to Patent Document 1, the number of constituent lenses is as large as four components, so it is difficult to reduce the total number of lenses. In addition, since the number of lens groups is large, the number of lens support members and lens drive systems also increases accordingly, and it is difficult to make the entire imaging lens device including the variable magnification optical system compact. Therefore, the variable magnification optical system according to Patent Document 1 has a long optical total length when used and is difficult to mount on a portable terminal.

  The present invention has been made in view of such a situation, and is an ultra-compact change in which an optical total length in use is short and aberrations are well corrected while being able to be changed by about 2 to 3 times. An object of the present invention is to provide a double optical system.

According to the first aspect of the present invention, an optical image of a subject is formed on a light receiving surface of an image sensor that converts an optical image into an electrical signal, and zooming is performed by changing the interval of each lens group in the optical axis direction. A variable power optical system including a first lens group having negative optical power and a second lens group having positive optical power, which are arranged in order from the object side, and from the wide-angle end to the telephoto end The zoom lens has a configuration in which the distance between the first lens group and the second lens group is reduced at the time of zooming, and the following conditional expression is satisfied.
15 ° <| α _W − α _T | <30 ° (1)
4.0 mm <T _W × f _W / f _T <9.0 mm (2)
However,
α _W : Angle (in degrees) with respect to the perpendicular to the principal ray image plane at the wide-angle end
α _T : Angle (degrees) at the telephoto end with respect to the perpendicular to the principal ray image plane
f _W : Total focal length of all optical systems at the wide angle end (mm)
f _T : Total focal length of all optical systems at the telephoto end (mm)
T _W : Optical total length of all optical systems at the wide-angle end (mm)
It is.

  According to this configuration, the first lens unit located closest to the object side has a so-called negative lead configuration in which negative optical power is provided. For this reason, a light ray incident at a large angle from the object side can be quickly relaxed by the negative optical power of the first lens group. Further, in the negative lead configuration, an increase in error sensitivity can be suppressed even if the size is reduced.

  Here, the image plane incident angle in conditional expression (1) defines the direction shown in FIG. 20 as the positive direction. That is, the principal ray angle when the left side of FIG. 20 is the object side and the right side is the image plane side and the exit pupil position is on the object side from the image plane is the positive direction.

  Here, if the lower limit of conditional expression (1) is not reached, the contribution to the zooming of the lens unit including the stop is reduced, and it becomes difficult to obtain a zooming ratio of about 2 to 3 times. Alternatively, if an attempt is made to obtain sufficient zooming under conditions that fall below the lower limit of conditional expression (1), the amount of movement of the lens unit including the aperture will increase, or the amount of movement of the exit pupil will increase. But the overall length is not compact. On the other hand, if the upper limit of conditional expression (1) is exceeded, the angle of incidence on the image sensor is greatly different between the wide-angle end and the telephoto end, resulting in excessive light vignetting at the microlens arranged on the image sensor. The drop in light intensity increases. In other words, by satisfying conditional expression (1), the incident angle of the light beam to the image sensor at the wide-angle end and the telephoto end becomes an appropriate value. Can be shortened.

  If the lower limit of conditional expression (2) is not reached, the total length at the wide-angle end is shortened, and the optical power of the lens group responsible for zooming becomes excessive, making it difficult to correct field curvature and spherical aberration. On the other hand, when the upper limit of conditional expression (2) is exceeded, the total length at the wide-angle end becomes long, and it is not compact.

A second aspect of the present invention is the variable magnification optical system according to the first aspect of the present invention, further satisfying the following conditional expression.
_{0.1 <L b / f W <} 0.9 ··· (3)
However,
L _b : Distance on the optical axis from the surface apex of the lens surface having the optical power closest to the image sensor to the image sensor surface at the telephoto end (lens back)
It is.

  Here, if the lower limit of conditional expression (3) is not reached, the distance between the image sensor and the lens on the image plane side is too short, making it difficult to mount the image sensor. On the other hand, when the upper limit of conditional expression (3) is exceeded, the lens back at the telephoto end becomes long, and it becomes difficult to secure the amount of movement of the second lens group necessary for zooming.

A third aspect of the invention is the variable magnification optical system according to the first or second aspect of the invention, and further satisfies the following conditional expression.
0 ° <α _W <30 ° (4)
Here, if the upper limit of conditional expression (4) is exceeded, the vignetting of off-axis light by the microlens on the image sensor increases, and the peripheral light amount drop resulting therefrom increases. On the other hand, if the lower limit of conditional expression (4) is not reached, the optical power required for the lens arranged closest to the image plane becomes strong, and it becomes difficult to correct distortion and curvature of field.

A fourth aspect of the present invention is the variable magnification optical system according to any one of the first to third aspects, further satisfying the following conditional expression.
0.2 <f _W / f _bg <2.0 (5)
However,
f _bg : the focal length of the lens unit closest to the image plane side.

  Here, if the lower limit of conditional expression (5) is not reached, the positive optical power of the lens unit closest to the image plane is weakened, so the angle at which off-axis rays are incident on the image sensor increases, and the exit pupil becomes the image sensor. Too close. For this reason, vignetting due to the microlens of the image sensor occurs, and the amount of peripheral light including the image sensor decreases. On the other hand, when the upper limit of conditional expression (5) is exceeded, the optical power of the lens unit closest to the image plane increases, and it becomes difficult to correct curvature of field and distortion generated in the lens unit.

  According to a fifth aspect of the present invention, there is provided an imaging lens device comprising the variable magnification optical system according to any one of the first to fourth aspects, wherein the variable magnification optical system is an optical image of a subject on a predetermined imaging surface. It is the structure which can be formed.

  According to this configuration, in a compact and high-definition imaging lens device that can be mounted on a mobile phone, a portable information terminal, or the like, it is possible to perform zooming about 2 to 3 times.

  The invention according to claim 6 is a digital device, and the imaging lens device according to claim 5, the imaging element, and at least one of still image shooting and moving image shooting of the object on the object side is captured by the imaging lens. And a functional unit to be executed by the apparatus and the image sensor.

  According to this configuration, zooming can be realized in a digital device such as a mobile phone or a portable information terminal while maintaining high definition.

  According to the first aspect of the present invention, the first lens group located closest to the object side has a so-called negative lead configuration having negative optical power. For this reason, a light ray incident at a large angle from the object side can be quickly relaxed by the negative optical power of the first lens group. In addition, since the optical total length can be shortened in the negative lead configuration, the overall size can be reduced as compared with the positive lead. Furthermore, the negative lead configuration suppresses an increase in error sensitivity even if the size is reduced, so the conditions imposed on the processing accuracy of the lens surface and the positional accuracy when the lens is placed on the lens barrel are relaxed. Also, high optical performance can be achieved. That is, manufacture becomes easy.

  Further, since the conditional expression (1) is satisfied, the contribution of the lens group responsible for zooming becomes appropriate, and a zoom ratio of about 2-3 times can be obtained. Furthermore, since the incident angle of the light beam to the image sensor at the wide-angle end and the telephoto end becomes an appropriate value, the total optical length in use can be shortened while keeping the peripheral light amount from being reduced.

  Furthermore, since the conditional expression (2) is satisfied, the optical power of the lens group responsible for zooming becomes appropriate, and correction of field curvature and spherical aberration can be performed satisfactorily. In addition, since the total length at the wide-angle end can be suppressed, downsizing is possible.

  According to the second aspect of the invention, the distance between the image sensor and the lens on the image plane side is appropriate, and the image sensor can be easily attached. Furthermore, since the lens back at the telephoto end can be kept short, it is possible to ensure the amount of movement of the second lens group necessary for zooming.

  According to the third aspect of the invention, the vignetting of off-axis light by the microlens on the image sensor is small, and the peripheral light amount drop can be suppressed small. Furthermore, since the optical power required for the lens arranged closest to the image plane is appropriate, distortion and field curvature can be corrected satisfactorily.

  According to the fourth aspect of the invention, since the positive optical power of the lens unit closest to the image plane is appropriate, the angle at which the off-axis ray is incident on the image sensor is appropriate. Therefore, the vignetting by the microlens of the image sensor is reduced, and the peripheral light amount drop can be suppressed small. Furthermore, since the optical power of the lens group closest to the image plane is appropriate, it is possible to satisfactorily correct field curvature and distortion occurring in the lens group.

  According to the fifth aspect of the present invention, it is possible to realize a compact and high-definition image pickup lens device that can perform a magnification change of about 2 to 3 times and can be mounted on a mobile phone or a portable information terminal.

  According to the invention described in claim 6, it is possible to realize a digital device such as a mobile phone or a portable information terminal capable of zooming in still image shooting or moving image shooting of a subject while maintaining high definition.

  FIG. 21 is an external configuration diagram of a camera-equipped mobile phone showing an embodiment of a digital device according to the present invention. In the present invention, the digital device includes a digital still camera, a digital video camera, a personal digital assistant (PDA), a personal computer, a mobile computer, or peripheral devices in addition to the mobile phone. . Digital still cameras and digital video cameras are imaging lens devices that optically capture an image of a subject, then convert the image to an electrical signal using a semiconductor element, and store it as a digital data in a storage medium such as a flash memory. is there. Furthermore, in the present invention, a mobile phone, a personal digital assistant, a personal computer, a mobile computer, or a peripheral device having a specification that incorporates a compact imaging lens device that optically captures a still or moving image of a subject. Contains.

  21A shows the operation surface of the mobile phone, and FIG. 21B shows the back surface of the operation surface, that is, the back surface. The mobile phone main body 200 has an antenna 201 on the top, a display 202 on the operation surface, an image switching button 203 for starting an image shooting mode and switching between still image and moving image shooting, and zooming according to the present invention. A scaling button 204, a shutter button 205, and a dial button 206 are provided. The enlargement / reduction button 204 is printed with “T” representing the telephoto end at the upper end portion and “W” representing the wide-angle end at the lower end portion, and each enlargement operation is performed by pressing the print position. Is configured with a two-contact type switch or the like. Further, the mobile phone body 200 includes an imaging lens device (camera) 207 configured by the variable magnification optical system according to the present invention, and the imaging lens is exposed on the back surface.

  When shooting a still image, first, the image switching mode 203 is pressed to activate the image shooting mode. Here, it is assumed that the still image shooting mode is activated by pressing the image switching button 203 once, and the moving image shooting mode is switched by pressing the image switching button 203 again in this state. That is, upon receiving an instruction from the image switching button 203, the control unit (not shown) of the mobile phone body 200 executes at least one of still image shooting and moving image shooting of the object on the object side on the imaging lens device and the imaging element. It has a function to make it.

  When the still image shooting mode is activated, an image of a subject is periodically and repeatedly imaged by an imaging element such as a CCD through the imaging lens device 207, transferred to the display memory, and then guided to the display 202. By looking through the display 202, it is possible to adjust the main subject so as to be in a desired position on the screen. By pressing the shutter button 205 in this state, a still image can be obtained, that is, image data is stored in a still image memory.

  At this time, when zoom shooting is performed because the subject is at a position away from the photographer or a close subject is to be enlarged, the state is detected by pressing the upper end “T” of the magnification button 204, The lens drive for zooming is executed according to the pressing time, and zooming is continuously performed. In addition, when it is desired to reduce the enlargement ratio of the subject, such as when zooming is excessive, the state is detected by pressing the lower end “W” printed portion of the scaling button 204, and continuously depending on the pressing time. Therefore, zooming is performed. In this way, the enlargement ratio can be adjusted using the zoom button 204 even for a subject away from the photographer. Then, as in normal normal shooting, an enlarged still image can be obtained by adjusting the main subject so that it falls within a desired position on the screen and pressing the shutter button 205.

  In addition, when performing moving image shooting, the still image shooting mode is activated by pressing the image switching button 203 once, and then the image switching button 203 is pressed again to switch to the moving image shooting mode. After that, as in the case of still image shooting, the display 202 is looked into, and the subject image obtained through the imaging lens device 207 is adjusted so as to be in a desired position on the screen. At this time, the enlargement ratio of the subject image can be adjusted using the scaling button 204. By pressing the shutter button 205 in this state, moving image shooting is started. During this shooting, the enlargement ratio of the subject can be changed at any time by the zoom button 204. Here, when the shutter button 205 is pressed again, the moving image shooting ends. The moving image is guided to a display memory for the display 202 and is also stored in a moving image memory.

  The scaling button 204 according to the present invention is not limited to this embodiment, and an existing dial button 206 may be used, or a rotary dial having a rotary shaft on the dial button installation surface. For example, a mode having a function of enabling scaling in two directions of enlargement and reduction may be used.

  Further, the present invention is not limited to a mobile phone, and can be applied to other digital devices such as a digital still camera, a digital video camera, a personal digital assistant, a personal computer, a mobile computer, or peripheral devices thereof. it can.

  As the lens system in the imaging lens device 207 according to the present invention shown in FIG. 21B, zooming is possible so that a subject away from the photographer can be photographed. There is a strong demand for the system. In the variable magnification optical system, a plurality of lens groups constitutes the lens system, and the variable magnification and focusing are performed by changing the distance between the lens groups in the optical axis direction. The present invention provides an image pickup lens device that forms an optical image of a subject on a light receiving surface of an image pickup device that converts the optical image into an electrical signal by using the zoom optical system, and the zoom optical system. The present invention relates to a digital device that includes an imaging lens device and an imaging element and has a function of performing still image or moving image shooting.

  Hereinafter, a variable power optical system according to the present invention, which constitutes the imaging lens device 207 of the camera-equipped mobile phone shown in FIG. 21B, will be described with reference to the drawings.

  In addition, throughout this specification, the optical power of each single lens constituting the cemented lens is such that both sides of the lens surface of the single lens have an interface with air, that is, the single lens exists alone. It refers to the power when you are.

[Embodiment 1]
FIG. 1 is a cross-sectional view of an arrangement of lens groups in the variable magnification optical system according to Embodiment 1 along the optical axis (AX). In FIG. 1 and FIGS. 2 to 9 shown below, the lens arrangement at the wide angle end (W) is shown. Throughout this embodiment, these lens groups are, in order from the object side (left side in FIG. 1) in the figure, a first lens group (Gr1) having a negative optical power as a whole, and a second lens having a positive optical power. It is composed of a group (Gr2) and a third lens group (Gr3) having a positive optical power. In each embodiment, an optical aperture (ST) for adjusting the amount of light is provided on the first lens group (Gr1) side of the second lens group (Gr2). A plane parallel plate (PL) and an image sensor (SR) are arranged on the side farther from the object of the lens group farthest from the object side.

  Hereinafter, in this specification, the terms “concave”, “convex” or “meniscus” are used for the lens, and these represent the lens shape in the vicinity of the optical axis (near the center of the lens), It does not represent the shape of the entire lens or near the end of the lens. This is not a problem with a spherical lens, but with an aspherical lens, it should be noted that generally the shape near the center and the end of the lens is different.

  In the variable power optical system of Embodiment 1 shown in FIG. 1, each lens group is configured as follows in order from the object side. The first lens group (Gr1) having negative optical power as a whole includes a biconcave negative lens (lens having negative optical power) and a positive meniscus lens convex to the object side (having positive optical power). Lens). The second lens group (Gr2) having a positive optical power as a whole is a cemented lens of a biconvex positive lens and a biconcave negative lens. The third lens group (Gr3) having a positive optical power as a whole is a biconvex positive lens. The number ri (i = 1, 2, 3,...) Shown in FIG. 1 is the i-th lens surface when counted from the object side (however, the cemented surface of the lens is counted as one surface). The surface with ri attached with * is an aspherical surface.

  Here, the number of lenses in the cemented lens is not represented by one for the entire cemented lens, but by the number of single lenses constituting the cemented lens. For example, the number of lenses of a cemented lens composed of three single lenses is counted as three instead of one.

  Under such a configuration, light rays incident from the object side in the figure sequentially pass through the first, second, and third lens groups (Gr1, Gr2, Gr3), and form an optical image of the object there. The optical image formed by this lens group passes through a plane parallel plate (PL) arranged adjacent to the third lens group (Gr3). At this time, the optical image is corrected so as to minimize so-called aliasing noise that occurs when the image is converted into an electrical signal in the imaging element (SR). The plane parallel plate (PL) corresponds to an optical low-pass filter, an infrared cut filter, a cover glass of an image sensor, or the like. Finally, in the image sensor (SR), the optical image corrected in the plane parallel plate (PL) is converted into an electrical signal. This electric signal is subjected to predetermined digital image processing, image compression processing, and the like as necessary, and is recorded as a digital video signal in a memory of a mobile phone, a portable information terminal, or other digital device by wire or wirelessly Or transmitted to.

  FIG. 10 is a schematic diagram showing how to move these lens groups at the time of zooming, and shows not only the first embodiment but also how to move each lens group in the second and later embodiments described later. is there. In FIG. 10, the left side is the object side as before, and the first lens group (Gr1), the second lens group (Gr2), and the third lens group (Gr3) are arranged in this order from the object side. Yes. In this figure, the symbol W indicates the wide angle end with the shortest focal length, that is, the largest angle of view, and the symbol T indicates the telephoto end with the longest focal length, that is, the smallest angle of view. The symbol M represents the middle (hereinafter referred to as an intermediate point) between the wide angle end (W) and the telephoto end (T). The actual lens group is moved on a straight line along the optical axis. In this figure, the positions of the lens group at the wide-angle end (W), the intermediate point (M), and the telephoto end (T) are It is shown in the form of arranging from the bottom.

  In the variable power optical system including three components having negative and positive optical powers as handled in the present embodiment, the second lens group (Gr2) is responsible for the variable power. Therefore, the second lens group (Gr2) mainly has optical power. However, in the compact variable power optical system according to the present invention, it is difficult to ensure a zoom ratio of about 2 to 3 times only by moving the second lens group (Gr2). Therefore, the lens group other than the second lens group (Gr2) is configured to be responsible for zooming. In Embodiment 1 having a lens configuration as shown in FIG. 1, the first lens group (Gr1) and the second lens group (Gr2) approach the object when zooming from the wide-angle end (W) to the telephoto end (T). On the other hand, the third lens group (Gr3) is linearly moved away from the object. The second lens group (Gr2) and the third lens group (Gr3) are mainly responsible for zooming.

  Hereinafter, the lens configurations from the second embodiment to the ninth embodiment will be described in order as in the first embodiment with reference to the drawings. At this time, the meanings of the reference numerals in FIGS. 2 to 9 are the same as those in FIG.

[Embodiment 2]
FIG. 2 is a cross-sectional view of the arrangement of lens groups in the variable magnification optical system according to Embodiment 2 taken along the optical axis (AX). In the variable magnification optical system according to the second embodiment, each lens group is configured as follows in order from the object side. The first lens group (Gr1) having negative optical power as a whole is composed of a cemented lens of a biconcave negative lens and a positive meniscus lens convex on the object side, and a biconcave negative lens. The second lens group (Gr2) having a positive optical power as a whole is a cemented lens of a biconvex positive lens and a biconcave negative lens. The third lens group (Gr3) having a positive optical power as a whole is a positive meniscus lens convex to the image side.

  In Embodiment 2 having such a lens configuration, as shown in FIG. 10, the first lens group (Gr1) is convex on the image side at the time of zooming from the wide-angle end (W) to the telephoto end (T). Moved to draw a trajectory. In other words, after being moved closer to the image side on the way from the wide-angle end (W) to the intermediate point (M), it is moved toward the object side, and the image at the telephoto end (T) is slightly larger than the position at the wide-angle end (W). Become side. Then, the second lens group (Gr2) is linearly moved in the direction approaching the object, and the third lens group (Gr3) is linearly moved away from the object.

[Embodiment 3]
FIG. 3 is a cross-sectional view of the arrangement of lens groups in the variable magnification optical system of Embodiment 3, with the optical axis (AX) cut longitudinally. In the variable power optical system of Embodiment 3 shown in FIG. 3, each lens group is configured as follows in order from the object side. The first lens group (Gr1) having a negative optical power as a whole is a cemented lens of a biconcave negative lens and a positive meniscus lens convex on the object side. The second lens group (Gr2) having a positive optical power as a whole is a cemented lens of a biconvex positive lens and a biconcave negative lens. The third lens group (Gr3) having a positive optical power as a whole is a cemented lens of a positive meniscus lens convex on the image side and a negative meniscus lens convex on the image side.

  In Embodiment 3 having such a lens configuration, when zooming from the wide-angle end (W) to the telephoto end (T), as shown in FIG. 10, the first lens group (Gr1) is convex on the image side. Moved to draw a trajectory. In other words, after being moved closer to the image side in the middle from the wide-angle end (W) to the intermediate point (M), it is moved to the object side, and the object at the telephoto end (T) is slightly more than the position at the wide-angle end (W). Become side. Then, the second lens group (Gr2) is linearly moved in the direction approaching the object, and the third lens group (Gr3) is linearly moved away from the object.

[Embodiment 4]
FIG. 4 is a cross-sectional view of the arrangement of lens groups in the variable magnification optical system according to Embodiment 4 taken along the optical axis (AX). The second lens in the fourth embodiment is a composite aspherical lens (a lens that is aspherical by applying a thin resin material on a spherical glass material to be a substrate). Since the resin material used for this composite aspherical lens has only an additional function of the substrate glass material, it is not handled as a single optical member, but is treated as if the substrate glass material has an aspherical surface, and the number of lenses is also Think of it as one. At this time, the lens refractive index is also defined as the refractive index of the glass material serving as the substrate.

  In the variable power optical system of Embodiment 4 shown in FIG. 4, each lens group is configured as follows in order from the object side. The first lens group (Gr1) having negative optical power as a whole is a cemented lens of a negative meniscus lens convex on the object side and a positive meniscus lens convex on the object side. The second lens group (Gr2) having a positive optical power as a whole is a cemented lens of a biconvex positive lens and a biconcave negative lens. The third lens group (Gr3) having a positive optical power as a whole is a positive meniscus lens convex to the image side.

  In Embodiment 4 having such a lens configuration, when zooming from the wide-angle end (W) to the telephoto end (T), as shown in FIG. 10, the first lens group (Gr1) is convex on the image side. Moved to draw a U-turn trajectory. That is, it is moved closer to the image side in the vicinity of the intermediate point (M) and then moved to the object side, and the positions at the telephoto end (T) and the wide-angle end (W) are substantially equal. Then, the second lens group (Gr2) is linearly moved in the direction approaching the object, and the third lens group (Gr3) is linearly moved away from the object.

[Embodiment 5]
FIG. 5 is a cross-sectional view of the arrangement of lens groups in the variable magnification optical system of Embodiment 5 taken along the optical axis (AX). In the variable power optical system of Embodiment 5, each lens group is configured as follows in order from the object side. The first lens group (Gr1) having a negative optical power as a whole is a cemented lens of a biconcave negative lens and a positive meniscus lens convex on the object side. The second lens group (Gr2) having a positive optical power as a whole is composed of a biconvex positive lens and a biconcave negative lens. Furthermore, the third lens group (Gr3) having a positive optical power as a whole is a biconvex positive lens.

  In Embodiment 5 having such a lens configuration, as shown in FIG. 10, at the time of zooming from the wide angle end (W) to the telephoto end (T), the first lens group (Gr1), the second lens group ( Gr2) and the third lens group (Gr3) are moved so as to draw the same trajectory as in the fourth embodiment.

[Embodiment 6]
FIG. 6 is a cross-sectional view of the lens group in the variable magnification optical system according to the sixth embodiment, taken along the optical axis (AX). In the zoom optical system of Embodiment 6, each lens group is configured as follows in order from the object side. The first lens group (Gr1) having negative optical power as a whole is a cemented lens of a negative meniscus lens convex on the object side and a positive meniscus lens convex on the object side. The second lens group (Gr2) having a positive optical power as a whole is a three-piece cemented lens including a biconvex positive lens, a biconcave negative lens, and a positive meniscus lens convex on the object side. Further, the third lens group (Gr3) having a positive optical power as a whole is a positive meniscus lens convex to the image side.

  In Embodiment 6 having such a lens configuration, when zooming from the wide angle end (W) to the telephoto end (T), as shown in FIG. 10, the first lens group (Gr1), the second lens group ( Gr2) and the third lens group (Gr3) are moved so as to draw the same trajectory as in Embodiments 4 and 5 described above.

[Embodiment 7]
FIG. 7 is a cross-sectional view of the arrangement of lens groups in the variable magnification optical system of Embodiment 7, with the optical axis (AX) taken longitudinally. In the variable magnification optical system of the seventh embodiment, each lens group is configured as follows in order from the object side. The first lens group (Gr1) having negative optical power as a whole is composed of a biconcave negative lens and a positive meniscus lens convex on the object side. The second lens group (Gr2) having a positive optical power as a whole includes a biconvex positive lens and a negative meniscus lens convex on the object side. Furthermore, the third lens group (Gr3) having a positive optical power as a whole is a biconvex positive lens.

  In Embodiment 7 having such a lens configuration, as shown in FIG. 10, the first lens group (Gr1) is convex on the image side at the time of zooming from the wide angle end (W) to the telephoto end (T). Moved to draw a trajectory. In other words, after being moved closer to the image side in the middle from the wide-angle end (W) to the intermediate point (M), it is moved to the object side, and the object at the telephoto end (T) is slightly more than the position at the wide-angle end (W). Become side. The second lens group (Gr2) is linearly moved in the direction approaching the object, and the position of the third lens group (Gr3) is fixed.

[Embodiment 8]
FIG. 8 is a cross-sectional view of the lens group in the variable magnification optical system according to the eighth embodiment, taken along the optical axis (AX). In the variable magnification optical system according to the eighth embodiment, each lens unit is configured as follows in order from the object side. The first lens group (Gr1) having negative optical power as a whole is composed of a biconcave negative lens and a positive meniscus lens convex on the object side. The second lens group (Gr2) having a positive optical power as a whole is a cemented lens of a biconvex positive lens and a negative meniscus lens convex on the object side. Furthermore, the third lens group (Gr3) having a positive optical power as a whole is a biconvex positive lens.

  In Embodiment 8 having such a lens configuration, as shown in FIG. 10, at the time of zooming from the wide angle end (W) to the telephoto end (T), the first lens group (Gr1), the second lens group ( Gr2) and the third lens group (Gr3) are moved so as to draw the same trajectory as in the seventh embodiment.

[Embodiment 9]
FIG. 9 is a cross-sectional view of the lens group in the variable magnification optical system according to the ninth embodiment, taken along the optical axis (AX). In the variable magnification optical system according to the ninth embodiment, each lens group is configured as follows in order from the object side. The first lens group (Gr1) having a negative optical power as a whole is a cemented lens of a biconcave negative lens and a positive meniscus lens convex on the object side. The second lens group (Gr2) having a positive optical power as a whole is a cemented lens of a biconvex positive lens and a biconcave negative lens. Further, the third lens group (Gr3) having a positive optical power as a whole is a positive meniscus lens convex to the image side.

  In Embodiment 9 having such a lens configuration, as shown in FIG. 9, the position of the first lens group (Gr1) is fixed at the time of zooming from the wide-angle end (W) to the telephoto end (T). Yes. The second lens group (Gr2) is linearly moved in a direction approaching the object, and the third lens group (Gr3) is linearly moved in a direction away from the object.

  In Embodiments 1 to 6 and 9 described above, the third lens group (Gr3) is linearly moved in the direction away from the object, but may be moved in a U-turn shape.

  In the first to ninth embodiments described above, the first lens group located closest to the object side has a so-called negative lead configuration having negative optical power. For this reason, a light ray incident at a large angle from the object side can be quickly relaxed by the negative optical power of the first lens group. In addition, since the optical total length can be shortened in the negative lead configuration, the overall size can be reduced as compared with the positive lead. Furthermore, the negative lead configuration suppresses an increase in error sensitivity even if the size is reduced, so the conditions imposed on the processing accuracy of the lens surface and the positional accuracy when the lens is placed on the lens barrel are relaxed. Also, high optical performance can be achieved. That is, manufacture becomes easy.

  In the first to ninth embodiments described above, the optical diaphragm (ST) is moved together with the second lens group (Gr2) having the largest movement amount. Therefore, an increase in the effective lens outer diameter of the second lens group (Gr2) can be suppressed. Furthermore, according to this configuration, since it is not necessary to provide a drive device dedicated to the optical diaphragm, the configuration of the lens drive device is simplified, and the entire imaging lens device can be made compact.

  However, the present invention is not limited to this, and the optical diaphragm (ST) may be moved independently of the lens group. According to this configuration, at the time of zooming from the wide-angle end to the telephoto end, it is possible to appropriately control the off-axis ray incident angle to the image pickup device by the optical aperture (ST).

  Hereinafter, conditions or conditional expressions for optical characteristics required for the lens system constituting the variable magnification optical system according to the present invention will be listed, and the grounds for the conditions (or grounds for numerical ranges) will be described.

A first lens group having negative optical power and a second lens group having positive optical power, which are arranged in order from the object side, are changed by changing the distance between the lens groups in the optical axis direction. In the variable magnification optical system that performs magnification, it is more desirable that the incident angle of the principal ray at the effective image circle diameter among the incident rays on the imaging surface satisfies the following conditional expression.
15 ° <| α _W − α _T | <25 ° ・ ・ ・ (1) '
With this configuration, the positional error in manufacturing the microlens and the image sensor can be increased, so that the image sensor can be easily manufactured and the manufacturing cost of the image sensor can be reduced.

The variable magnification optical system more preferably satisfies the following conditional expression.
0.3 <L _b / f _W <0.7 (3) ′
This is because, if the lower limit of conditional expression (3) ′ is not reached, the distance between the image sensor and the lens on the image plane side is too short, making it difficult to mount the image sensor. On the other hand, when the upper limit of conditional expression (3) ′ is exceeded, the lens back at the telephoto end becomes long, and it becomes difficult to secure the amount of movement of the second lens group necessary for zooming.

The variable magnification optical system more preferably satisfies the following conditional expression.
0 ° <α _W <20 ° ・ ・ ・ (4) '
This is because the position error in manufacturing the microlens and the image sensor can be increased by using this configuration, so that the image sensor can be easily manufactured and the manufacturing cost can be reduced.

The variable magnification optical system is
0.2 <f _W / f _bg <1.0 (5) ′
It is more desirable to satisfy
0.4 <f _W / f _bg <0.7 (5) ''
It is more desirable to satisfy. This is because if the upper limit of conditional expression (5) ′ is exceeded, the error sensitivity of the lens unit closest to the image plane becomes high, and manufacturing becomes difficult. If the lower limit of conditional expression (5) ′ is not reached, the incident angle of off-axis light to the image sensor cannot be reduced, and the amount of light loss including vignetting by the microlens on the image sensor becomes too large. .

The variable magnification optical system is
_{-4.0 <f 1g / f w <} -1.0 ··· (6)
It is more desirable to satisfy
_{-3.3 <f 1g / f w <} -2.0 ··· (6) '
It is more desirable to satisfy.
However,
f _1g is the focal length of the first lens group (Gr1).

  This is because, if the lower limit of conditional expression (6) is not reached, the negative optical power of the first lens group (Gr1) becomes weak, so that the amount of movement necessary for zooming becomes large, and the total lens length becomes not compact. . On the other hand, when the upper limit of conditional expression (6) is exceeded, the optical power of the first lens group (Gr1) becomes strong, and it becomes difficult to correct the field curvature generated in the first lens group (Gr1). The error sensitivity in the first lens group (Gr1) becomes excessive, making manufacturing difficult.

  On the other hand, if the lower limit of conditional expression (6) ′ is not reached, the negative optical power of the first lens group (Gr1) becomes too weak, the lens diameter of the first lens group (Gr1) becomes large, and it is not compact in the radial direction. . On the other hand, if the upper limit of conditional expression (6) ′ is exceeded, the optical power of the negative lens in the first lens group (Gr1) becomes too strong, and the concave shape of the negative lens becomes tight. Rises.

The variable magnification optical system is
0.5 < _f2g / _fw <3.0 (7)
It is more desirable to satisfy
1.0 < _f2g / _fw <1.9 (7) '
It is more desirable to satisfy.
However,
f _2g is the focal length of the second lens group (Gr2).

  This is because if the lower limit of conditional expression (7) is not reached, the positive optical power of the second lens group (Gr2) becomes stronger, and it is difficult to correct axial chromatic aberration and spherical aberration generated in the second lens group (Gr2). This is because the error sensitivity in the second lens group (Gr2) becomes excessive and manufacturing becomes difficult. On the other hand, if the upper limit of conditional expression (7) is exceeded, the optical power of the second lens group (Gr2) becomes weak, and the amount of movement necessary for zooming becomes large, so the total lens length is not compact.

  If the lower limit of conditional expression (7) ′ is not reached, the error sensitivity in the second lens group (Gr2) increases, and it is necessary to adjust the lens position in order to obtain good performance with a high-pixel imaging device. This increases the manufacturing cost. On the other hand, if the upper limit of conditional expression (7) 'is exceeded, the optical power of the second lens group (Gr2) becomes weak and the amount of movement required for zooming becomes large, so that the total lens length is not compact.

The variable magnification optical system is
-5 ° <α _T <15 ° (8)
It is more desirable to satisfy
-4 ° <α _T <7 ° (8) '
It is more desirable to satisfy.

  This is because, if the lower limit of conditional expression (8) is not reached, the lens diameter close to the image sensor increases and the size of the lens unit in the radial direction is not compact. On the other hand, if the upper limit of conditional expression (8) is exceeded, the vignetting of off-axis light by the microlens on the image sensor increases at the wide-angle end, and the peripheral light amount drop resulting therefrom increases.

  Further, when the conditional expression (8) ′ is satisfied, it becomes possible to increase a positional tolerance between the microlens and the light receiving element on the image sensor, and even if a higher-definition image sensor is used, the off-axis light of the microlens is reduced. Since vignetting can be prevented, it is suitable for increasing the number of pixels.

  In the variable magnification optical system, it is desirable to perform focusing by moving the second lens group (Gr2) or the lens group on the image side of the second lens group alone or by moving a plurality of groups. Since the variable magnification optical system according to the present invention is a compact size that can be mounted on a mobile phone or the like, performing focusing by extending the first lens group (Gr1) is disadvantageous from the viewpoint of the total optical length. is there. Further, focusing with the first lens group (Gr1) is not desirable because it causes an increase in the front lens diameter in order to secure the peripheral light amount.

  When the optical power of the lens group includes negative positive / negative in order from the object side as in the variable magnification optical system in the present embodiment, the third lens group has weaker optical power than other lens groups, and aberrations The effect on the correction is not great. For this reason, it is desirable to use one or two sheets. And when comprised with two sheets, you may arrange | position so that there may be an air gap between lens surfaces, and you may arrange | position with a lens surface closely_contact | adhered. Furthermore, it may be fixedly integrated into a cemented lens.

  In any lens group, when the lens surfaces are brought into close contact, an adhesive such as an ultraviolet curable resin may be interposed between the lens surfaces.

  In the embodiment described above, each lens group has an aspherical surface, but is not limited thereto. For example, if an aspherical surface is disposed in the first lens group (Gr1), it is possible to effectively correct off-axis aberrations, particularly astigmatism and distortion. Further, for example, if an aspheric surface is arranged in the second lens group (Gr2), it is possible to effectively correct axial aberrations, particularly spherical aberration.

  Furthermore, it is more desirable to make all lens surfaces having an interface with gas aspherical because the aspherical effect can be effectively exhibited. As a result, both compactness and high image quality can be achieved.

  Moreover, it is desirable that at least one of the negative lens and the positive lens is made of a resin material. In this case, the deformation caused by the expansion or contraction of the resin material caused by the temperature change and the back focus shift due to the refractive index change can be canceled out by the negative lens and the positive lens, and can be suppressed to a small level.

  Furthermore, the lens having an aspherical surface may be molded by a mold, or of course a composite type of a glass material and a resin material. The mold type is suitable for mass production, but the glass material is limited. On the other hand, the composite type has the advantage that there are many glass materials that can be used as a substrate and the degree of freedom in design is high.

  Further, it is desirable that the exit pupil position at the wide-angle end (W) be arranged on the object side with respect to the imaging element surface. This is because it is possible to achieve a compact size while ensuring a wide angle of view.

  Furthermore, although the present embodiment is a continuous variable magnification optical system, the present invention is not limited to this, and a bifocal switching optical system having the same optical configuration may be used in order to further reduce the size. In particular, when the zoom movement from the wide-angle end to the telephoto end makes the U-turn of the first group and the optical total length at the wide-angle end and the telephoto end is the same, a two-focus switching variable magnification optical system is obtained. Thus, since the first lens group (Gr1) is a fixed group, there is a great effect in reducing the unit size including the drive mechanism.

  Furthermore, in the above embodiment, a mechanical shutter having a function of shielding light from the image sensor (SR) may be disposed as the optical diaphragm (ST). The mechanical shutter is also effective in preventing smear when, for example, a CCD system is used as an image sensor.

  The variable power optical system constituting each embodiment includes a refractive lens that deflects incident light by refraction (that is, a lens that deflects at the interface between media having different refractive indexes). Although used, the lens which can be used is not restricted to this. For example, a diffractive lens that deflects incident light by diffracting action, a refractive / diffractive hybrid lens that deflects incident light by combining diffractive action and refracting action, and a refractive index distribution that deflects incident light by a refractive index distribution in the medium A mold lens or the like may be used. Further, in addition to the optical aperture (ST), a light beam restricting plate or the like may be arranged as necessary.

  As described above, the present invention relates to an ultra-compact, inexpensive, and high-definition variable magnification optical system. The entire optical system is composed of lens groups having two or more components, and has a mechanism for changing the magnification by changing the distance between the lens groups in the optical axis direction.

  At this time, as shown in the above embodiment, it is desirable that all the lens groups are composed of single lenses or cemented lenses. According to this configuration, it is not necessary to provide a plurality of members for supporting the lens in the lens group. As a result, the mechanical mechanism can be simplified and the entire imaging lens device can be made more compact.

  In the case of a cemented lens, it is possible to maintain the accuracy at the time of lens cementing rather than the mechanical accuracy of the support member for supporting the lens. As a result, aged deterioration that the optical axis shifts within the lens group due to long-term use does not occur, and optical adjustment becomes easy. Furthermore, the error sensitivity due to eccentricity can be reduced by bonding. In addition, since there is no gap between the lens surfaces due to the cementing, unnecessary inter-surface reflected light can be suppressed, and a good optical image can be obtained.

  The first lens group (Gr1) is preferably composed of one negative lens and one positive lens arranged in order from the object side. Thereby, since the chromatic aberration in the first lens group (Gr1) can be corrected, the performance of the lens group can be improved. In addition, by disposing a negative lens on the object side, the angle of off-axis light incident on the positive second lens can be reduced, so that error sensitivity can be reduced. Furthermore, since the first lens group (Gr1) is composed of two lenses, the lens can be made thinner than that of three or more lenses, so that the total lens length can be reduced. In addition to the above, it is desirable that an aspherical surface be disposed in the first lens group (Gr1). With this configuration, it is possible to correct field curvature aberration generated in the first lens group (Gr1). Become.

  The second lens group (Gr2) is preferably composed of one positive lens and one negative lens arranged in order from the object side. Thereby, since the chromatic aberration in the second lens group (Gr2) can be corrected, the performance of the lens group can be improved. In addition, since the height of the on-axis light incident on the negative lens can be reduced by arranging the positive lens on the object side, the error sensitivity of spherical aberration can be reduced. Furthermore, since the second lens group (Gr2) is composed of two lenses, it can be made thinner than that of three or more lenses, so that the total lens length can be reduced. In addition to the above, it is desirable to dispose an aspherical surface in the second lens group (Gr2). With this configuration, it is possible to correct spherical aberration occurring in the second lens group (Gr2).

  Furthermore, it is desirable to dispose at least one aspherical surface on the lens disposed closest to the image sensor. With this configuration, distortion aberration correction is possible, and the exit pupil position at each image height can be controlled, so that fluctuations in the exit pupil position at each image height can be reduced. The arrangement of microlenses can be simplified. Therefore, it is possible to reduce the manufacturing cost of the image sensor including the microlens.

  Next, an example of a specific embodiment of an imaging lens device incorporating the variable magnification optical system according to the present invention will be described with reference to the drawings.

  FIG. 22 is a perspective view illustrating an example of an internal configuration of the imaging lens device 10. However, here, in addition to the imaging lens device that combines the lens group constituting the variable magnification optical system, the driving device for the lens group, etc., it is shown in a form including an imaging element (not shown). In this embodiment, the variable magnification optical system is composed of three lens groups. Further, it is assumed that when zooming, the second lens group 102 and the third lens group 103 are moved to zoom and focus, and the position of the first lens group 101 is fixed. This corresponds to the movement of the ninth embodiment shown in FIG.

  As shown in FIG. 22, in the imaging lens device 10, a first lens group 101, a second lens group 102, and a third lens group 103 are arranged from the subject (object) side so that their optical axes coincide with each other. Configured. The first, second and third lens groups 101 to 103 are supported by support members 104 to 106, respectively. The parallel plane plate and the image sensor (not shown) are supported by a fixing member 107 and are fixed to the central portion of the fixing member 107. The fixing member 107 is fixed to a mobile phone body (not shown). A rod-shaped guide member 108 is passed through the support members 104 to 106 of the first, second, and third lens groups.

  In addition, a drive unit 20 made of, for example, an impact-type piezoelectric actuator is attached to the support member 106 of the third lens group. Driven along the optical axis. More specifically, the drive unit 20 includes a support member 21, a piezoelectric element 22, a drive member 23, and an engagement member 24. The support member 21 is fixed to a mobile phone body (not shown) and holds the piezoelectric element 22 and the drive member 23. The piezoelectric element 22 is installed such that the direction of expansion and contraction, which is the polarization direction, coincides with the axial direction of the support member 21. One end of the drive member 23 is fixed to the piezoelectric element 22, and the other end is fixed to the side surface of the engagement member 24. Further, the support members 105 and the engaging member 24 of the second lens group are respectively provided with engaging portions 105a and 106a at appropriate positions.

  With the above configuration, when a voltage is applied to the piezoelectric element 22 by a driving means (not shown), the piezoelectric element 22 extends or contracts in the optical axis direction depending on the direction of the voltage. Then, the expansion or contraction is transmitted to the engaging member 24 joined through the driving member 23. Since the engaging member 24 is bonded to the support member 106 of the third lens group, the third lens group 103 can be moved thereby. At this time, the engaging portions 105a and 106a are engaged with cam members or the like (not shown) to cause the second and third lens groups 102 and 103 to perform desired movements necessary for zooming and focusing. Is possible. Further, by providing an engaging portion similar to the engaging portions 105a and 106a on the support member 104 of the first lens group, it is possible to simultaneously drive the three lens groups to perform zooming and focusing. . Furthermore, with the same configuration, it is possible to provide two or four or more lens groups and drive them independently or with correlation to perform zooming and focusing.

  In such an imaging lens device, a light beam incident from the subject side sequentially passes through the first, second, and third lens groups 101 to 103. Then, the light passes through a parallel plane plate (not shown) arranged adjacent to the third lens group 103. At this time, the optical image is corrected so as to minimize so-called aliasing noise that occurs when the image is converted into an electrical signal in the image sensor. This parallel plane plate corresponds to an optical low-pass filter, an infrared cut filter, a cover glass of an image sensor, or the like. Finally, an optical image of the object is formed on the light-receiving surface of the imaging element (not shown), and then the optical image is converted into an electrical signal. This electric signal is subjected to predetermined digital image processing, image compression processing, and the like as necessary, and is recorded as a digital video signal in a memory of a mobile phone, a portable information terminal, or other digital device by wire or wirelessly Or transmitted to.

  A stepping motor or the like may be used to drive each lens group and the optical aperture. Alternatively, when the moving amount is small or the weight of the lens group is light, an ultra-small piezoelectric actuator may be used independently for each lens group. Thereby, not only can each lens group be driven independently, but also the entire imaging lens device can be made more compact while suppressing an increase in volume and power consumption of the drive unit.

  Hereinafter, examples of the variable magnification optical system according to the present invention will be described in more detail with reference to construction data, aberration diagrams, and the like.

  The construction data of each lens in Embodiment 1 (Example 1) is shown in Tables 1 and 2. In the present embodiment, the first and fifth lenses, that is, the object side lens and the third lens group (Gr3) in the first lens group (Gr1) are plastic lenses (resin lenses).

  Table 1 shows, in order from the left, the number of each lens surface, the radius of curvature (unit: mm) of each surface, the wide angle end (W), the intermediate point (M), and the optical axis at the telephoto end (T). The distance between each lens surface (axis top surface distance) (unit: mm), the refractive index of each lens, and the Abbe number. The blanks for the axial top surface spacings M and T indicate that they are the same as the values in the left W column. Here, the number ri (i = 1, 2, 3,...) Of each lens surface is the i-th lens surface counted from the object side, as shown in FIG. The attached surface is an aspherical surface.

  As can be seen from Table 1, in Example 1, both surfaces of the first lens (first lens counted from the object side) (first lens group (Gr1)), the second lens (first lens group (Gr1)). )) Image side surface, both end surfaces (surfaces facing the outside air) of each cemented lens constituting the second lens group (Gr2), and both surfaces of the fifth lens (third lens group (Gr3)). Is an aspherical surface. In addition, since each surface of the optical diaphragm (ST), both surfaces of the plane parallel plate (PL), and the light receiving surface of the image sensor (SR) is a flat surface, the radius of curvature thereof is ∞.

  The aspherical shape of the lens is defined by the following equation using a local orthogonal coordinate system (x, y, z) in which the surface vertex is the origin and the direction from the object toward the image sensor is the positive direction of the z axis. .

However,
z: Amount of displacement in the z-axis direction at the position of height h (based on the surface vertex)
h: Height in the direction perpendicular to the z-axis (h ² = x ² + y ² )
c: Paraxial curvature (= 1 / radius of curvature)
A, B, C, D, E, F, G, H, J: 4th, 6th, 8th, 10th, 12th, 14th, 16th, 18th, and 20th-order aspherical coefficients k: conic coefficients. Table 2 shows only the conical coefficient k and the aspheric coefficients A, B, C, and D, but the other aspheric coefficients E, F, G, H, and J are zero. As can be seen from Equation 1, the radius of curvature for the aspherical lens shown in Table 1 shows a value near the center of the lens.

  Spherical aberration (LONGITUDINAL SPHERICAL ABERRATION) and astigmatism of the entire optical system of Example 1 (a combination of the first, second, and third lens groups) under the lens arrangement and configuration as described above. (ASTIGMATISM) and distortion (DISTORTION) are shown in order from the left side of FIG. In this figure, the upper part represents the aberration at the wide-angle end (W), the middle part represents the aberration at the intermediate point (M), and the lower part represents the aberration at the telephoto end (T). Further, the horizontal axis of spherical aberration and astigmatism represents the shift of the focal position in mm, and the horizontal axis of distortion aberration represents the amount of distortion as a percentage of the whole. The vertical axis of spherical aberration is indicated by a value normalized by the incident height, while the vertical axis of astigmatism and distortion is indicated by the height of the image (image height) (unit: mm). Further, the spherical aberration diagram shows three different wavelengths: red (wavelength 656.27 nm) with a dashed line, yellow (so-called d line; wavelength 587.56 nm) with a solid line, and blue (wavelength 435.83 nm) with a broken line. The aberrations when using light are shown respectively. In the figure of astigmatism, symbols S and T represent results on a sagittal (radial) surface and a tangential (meridional) surface, respectively. Further, the diagrams of astigmatism and distortion are the results when the yellow line (d line) is used. As can be seen from FIG. 11, the lens group of Example 1 has a spherical aberration and astigmatism of approximately 0.1 mm at any of the wide angle end (W), the intermediate point (M), and the telephoto end (T). In addition, the distortion aberration is excellent within about 5%. Further, Table 19 and Table 20 show the focal length (unit: mm) and the F value at the wide angle end (W), the intermediate point (M), and the telephoto end (T) in Example 1, respectively. From these tables, it can be seen that in the present invention, a bright optical system with a short focus can be realized.

  Next, construction data of each lens in Embodiment 2 (Example 2) are shown in Tables 3 and 4. As can be seen from these tables, in Example 2, the most object-side surface of the first lens (first lens group (Gr1)) and both end surfaces of each cemented lens constituting the second lens group (Gr2) (Surface facing the outside air) and both surfaces of the sixth lens (third lens group (Gr3)) are aspherical surfaces. In this embodiment, all the constituent lenses are made of glass.

  Construction data of each lens in Embodiment 3 (Example 3) is shown in Tables 5 and 6. As can be seen from these tables, in Example 3, the image-side surface of the second lens (first lens group (Gr1)) and both end surfaces of the cemented lenses constituting the second lens group (Gr2) ( The surface facing the outside air) and the image side surface of the sixth lens (third lens group (Gr3)) are aspherical. That is, all lens surfaces facing the outside air are aspheric. In this embodiment, all the constituent lenses are made of glass.

  The construction data of each lens in Embodiment 4 (Example 4) is shown in Table 7 and Table 8. As can be seen from these tables, in Example 4, both end surfaces (surfaces facing the outside air) of the respective cemented lenses constituting the first lens group (Gr1) and the second lens group (Gr2), the first Both surfaces of the five lenses (third lens group (Gr3)) are aspherical. That is, all lens surfaces facing the outside air are aspheric. In particular, the image side surface of the second lens is a composite aspherical lens. In this embodiment, all the constituent lenses are made of glass.

  Construction data of each lens in Embodiment 5 (Example 5) is shown in Table 9 and Table 10. As can be seen from these tables, in Example 5, both end surfaces (surfaces facing the outside air) of the cemented lenses constituting the first lens group (Gr1) and the second lens group (Gr2), and Both surfaces of the fifth lens (third lens group (Gr3)) are aspheric. That is, all lens surfaces facing the outside air are aspheric. In the present embodiment, the first, second and fifth lenses, that is, the first lens group (Gr1) and the third lens group (Gr3) are plastic lenses.

  The construction data of each lens in Embodiment 6 (Example 6) is shown in Table 11 and Table 12. As can be seen from these tables, in Example 6, both end faces (surfaces facing the outside air) of the cemented lenses constituting the first lens group (Gr1) and the second lens group (Gr2), and Both surfaces of the sixth lens (third lens group (Gr3)) are aspheric. That is, all lens surfaces facing the outside air are aspheric.

  Construction data of each lens in Embodiment 7 (Example 7) is shown in Table 13 and Table 14. As can be seen from these tables, in Example 7, both surfaces of all the lenses constituting the first lens group (Gr1), the second lens group (Gr2), and the third lens group (Gr3) are aspherical. . That is, all lens surfaces facing the outside air are aspheric. In this embodiment, all the constituent lenses are made of glass.

  Table 15 and Table 16 show construction data of each lens in the eighth embodiment (Example 8). As can be seen from these tables, in Example 8, both surfaces of all the lenses constituting the first lens group (Gr1), the second lens group (Gr2), and the third lens group (Gr3) are aspherical. . That is, all lens surfaces facing the outside air are aspheric. In this embodiment, all the constituent lenses are made of glass.

  Table 17 and Table 18 show construction data of each lens in the ninth embodiment (Example 9). As can be seen from these tables, in Example 9, both end surfaces of the respective lens groups constituting the first lens group (Gr1), the second lens group (Gr2), and the third lens group (Gr3) (external air) The facing surface) is aspherical. That is, all lens surfaces facing the outside air are aspheric. In this embodiment, all the constituent lenses are made of glass.

  The spherical aberration, astigmatism, and astigmatism of all the optical systems of Examples 2 to 9 (combining the first, second, and third lens groups) under the lens arrangement and configuration as described above. The distortion aberration is shown in FIGS. In any of the embodiments, the lens group has both spherical aberration and astigmatism within approximately 0.1 mm and distortion of approximately 5% at the wide-angle end (W), the intermediate point (M), and the telephoto end (T). It shows excellent optical properties. In addition, Tables 19 and 20 show focal lengths (unit: mm) and F values at the wide-angle end (W), the intermediate point (M), and the telephoto end (T) in Examples 2 to 9, respectively. From these tables, it can be seen that, similarly to Example 1, a bright optical system with a short focal point can be realized.

  Further, Table 21 shows values of the conditional expressions (1) to (17) obtained in Examples 1 to 9. In this example, it can be seen that the above-described desirable value is obtained in any conditional expression.

  As described above, the present embodiment is mainly configured by using a glass lens. In the first and fifth embodiments, a plastic lens is used in combination. However, the present invention is not limited to these, and one or more lenses can be plastic lenses. In particular, since the first lens group (Gr1) has a larger lens diameter than the other lens groups, the effect of weight reduction by using plastic is the greatest. Further, in the variable magnification optical system according to the present invention, the amount of movement of the second lens group (Gr2) is the largest. However, by making it the plastic, the load on the lens driving device can be reduced.

  Furthermore, since the optical power of the third lens group (Gr3) is weaker than other lens groups, it can be made of plastic while maintaining good aberration correction. In any case, by using a plastic lens, the lens driving device can be downsized, and as a result, the entire imaging lens device including the lens group and the lens driving device can be further downsized. Furthermore, plastic lenses are superior in terms of cost and productivity compared to glass lenses.

  As described above, since the imaging lens device incorporating the variable magnification optical system according to the present invention is small and lightweight, it can be mounted on a digital device such as a cellular phone. As a result, still image or moving image shooting can be performed at a desired magnification. Furthermore, since it has high optical performance that can be applied to a high-pixel imaging device of 2 million pixel class or higher, it has a high advantage over an electronic zoom method that requires interpolation.

FIG. 3 is a cross-sectional view in which the optical axis in the variable magnification optical system according to Embodiment 1 is longitudinally cut. FIG. 5 is a cross-sectional view in which the optical axis in the variable magnification optical system of Embodiment 2 is vertically cut. FIG. 5 is a cross-sectional view in which the optical axis in the variable magnification optical system of Embodiment 3 is cut longitudinally. FIG. 6 is a cross-sectional view in which the optical axis in the variable magnification optical system of Embodiment 4 is vertically cut. FIG. 10 is a cross-sectional view in which the optical axis in the variable magnification optical system of Embodiment 5 is cut longitudinally. FIG. 10 is a cross-sectional view in which an optical axis in a variable magnification optical system according to Embodiment 6 is vertically cut. FIG. 10 is a cross-sectional view in which the optical axis in the variable magnification optical system of Embodiment 7 is cut longitudinally. FIG. 10 is a cross-sectional view in which the optical axis in the variable magnification optical system according to Embodiment 8 is vertically cut. FIG. 10 is a cross-sectional view in which the optical axis in the variable magnification optical system of Embodiment 9 is cut longitudinally. It is a schematic diagram which shows how to move the lens group in the variable magnification optical system of Embodiments 1-9. FIG. 6 is an aberration diagram showing spherical aberration, astigmatism, and distortion of the lens group in the variable magnification optical system of Example 1. FIG. 6 is an aberration diagram showing spherical aberration, astigmatism, and distortion of the lens group in the variable magnification optical system of Example 2. FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion of the lens group in the variable magnification optical system of Example 3. FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion of the lens group in the variable magnification optical system of Example 4; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion of the lens group in the variable magnification optical system of Example 5. 10 is an aberration diagram illustrating spherical aberration, astigmatism, and distortion of the lens group in the variable magnification optical system of Example 6. FIG. 10 is an aberration diagram illustrating spherical aberration, astigmatism, and distortion of the lens group in the variable magnification optical system of Example 7. FIG. 10 is an aberration diagram illustrating spherical aberration, astigmatism, and distortion of the lens group in the variable magnification optical system of Example 8. FIG. 10 is an aberration diagram illustrating spherical aberration, astigmatism, and distortion of the lens group in the variable magnification optical system of Example 9. FIG. It is a schematic diagram which shows the definition of the image surface incident angle of a chief ray. (A) is an external appearance block diagram which shows the operation surface of the mobile telephone with a camera carrying the variable magnification optical system based on this invention. (B) is an external appearance block diagram which shows the back surface of the operation surface of the mobile telephone with a camera carrying the variable magnification optical system based on this invention. It is a perspective view which shows an example of an internal structure of the imaging lens apparatus provided with the variable magnification optical system and imaging device which concern on this invention.

Explanation of symbols

Gr1 1st lens group Gr2 2nd lens group Gr3 3rd lens group Gr4 4th lens group ST Optical aperture PL Parallel plane plate SR Image sensor AX Optical axis 10 Imaging lens device 101 1st lens group 102 2nd lens group 103 3rd Lens Group 104 First Lens Group Support Member 105 Second Lens Group Support Member 106 Third Lens Group Support Member 107 Imaging Element Fixing Member 105a Second Lens Group Support Member Engagement Part 106a Engagement Part 108 Guide Member 20 Drive unit 21 Support member 22 Piezoelectric element 23 Drive member 24 Engagement member 200 Mobile phone body 201 Antenna 202 Display 203 Image switching button 204 Scaling button 205 Shutter button 206 Dial button 207 Imaging lens device (camera)

Claims (6)

A variable power optical system that forms an optical image of a subject on a light receiving surface of an image sensor that converts an optical image into an electrical signal, and performs zooming by changing the interval of each lens group in the optical axis direction,
The first lens includes a first lens group having negative optical power and a second lens group having positive optical power, which are arranged in order from the object side, and at the time of zooming from the wide angle end to the telephoto end. A variable magnification optical system having a configuration in which a distance between the first lens group and the second lens group is reduced and satisfying the following conditional expression.
15 ° <| α _W − α _T | <30 °
4.0 mm <T _W × f _W / f _T <9.0 mm
α _W : Angle (in degrees) with respect to the perpendicular to the principal ray image plane at the wide-angle end
α _T : Angle (degrees) at the telephoto end with respect to the perpendicular to the principal ray image plane
f _W : Total focal length of all optical systems at the wide angle end (mm)
f _T : Total focal length of all optical systems at the telephoto end (mm)
T _W : Optical total length of all optical systems at the wide-angle end (mm) The variable magnification optical system according to claim 1, further satisfying the following conditional expression:
_{0.1 <L b / f W <} 0.9
L _b : Distance on the optical axis from the surface apex of the lens surface having the optical power closest to the image sensor to the image sensor surface at the telephoto end The zoom lens system according to claim 1, further satisfying the following conditional expression:
0 ° <α _W <30 ° 4. The variable magnification optical system according to claim 1, further satisfying the following conditional expression.
0.2 <f _W / f _bg <2.0
f _bg : Focal length of the lens unit closest to the image plane   5. An imaging system comprising the variable magnification optical system according to claim 1, wherein the variable magnification optical system is capable of forming an optical image of a subject on a predetermined imaging surface. Lens device.   6. The image pickup lens device according to claim 5, an image pickup device, and a functional unit that causes the image pickup lens device and the image pickup device to perform at least one of still image shooting and moving image shooting of the object on the object side. A digital device characterized by

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