JP2005338344A - Imaging lens device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin type imaging lens device having a high performance, small type zoom lens system that satisfies high image quality. <P>SOLUTION: The zoom lens system TL that is a photographing lens system comprises, in order from an object side, a first group GR1 with negative power, a second group GR2 with positive power, a third group GR3 with negative power, and a fourth group GR4 with positive power. In zooming from a wide-angle end (W) to a telephoto end (T), the first group GR1 and the third group GR3 are fixed in position relative to an image face IM, the second group GR 2 moves towards the object, and the fourth group GR 4 moves so as to describe a projecting U-shaped locus on the image side. An optical image formed by the zoom lens system is converted into an electrical signal by an imaging element SR. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging lens device, and more specifically, an imaging lens device that optically captures an image of a subject by a photographing lens system and outputs it as an electrical signal by an imaging device {eg, a digital still camera; Main components of a camera incorporated in or externally attached to a personal computer, a mobile computer, a mobile phone, a portable information terminal, etc.}, in particular, an imaging lens device having a small zoom lens system, and a thin type having the imaging lens device Is related to the camera.

  In recent years, with the spread of personal computers and the like, digital still cameras and digital video cameras (hereinafter simply referred to as “digital cameras”) that can easily capture image information into digital devices are becoming popular at the individual user level. . Digital cameras are expected to become increasingly popular as image information input devices. The image quality of such a digital camera is generally determined by the number of pixels of a solid-state imaging device such as a CCD (Charge Coupled Device). Currently, digital cameras for general use have a higher pixel count of over 5 million pixels, and are approaching silver halide film cameras in terms of image quality. For this reason, the photographing lens system is required to have high optical performance corresponding to the increase in the number of pixels of the image sensor.

In general digital cameras, image scaling, particularly optical scaling with little image degradation, is desired. On the other hand, it is desired to reduce the thickness to improve portability. In order to meet the demand for higher image quality and thinner digital cameras, various types of zoom lens systems have been proposed (see, for example, Patent Documents 1 to 9).
JP 2001-296476 A JP 2000-137164 A JP-A-8-248318 JP-A-9-133858 JP 2002-277736 A JP 11-258678 A JP 2003-43354 A Japanese Patent Laid-Open No. 10-48521 JP 2000-292698 A

  Most zoom lens systems for digital cameras that have been proposed conventionally employ a so-called collapsible lens barrel as a method for making the digital camera thinner. In the retractable lens barrel, the zoom lens system is retracted when the camera is not used and the distance between the lenses is kept to a minimum. When the camera is used, the zoom lens system is extended to the original lens arrangement state. Retained. In the zoom lens system described in Patent Document 1, an attempt is made to reduce the thickness of the zoom lens system when retracted by reducing the number of constituent lenses while maintaining good optical performance. However, in the retractable method, the imaging lens device cannot be made thinner than the total value of the thickness of the lens itself, the thickness of the imaging device, and the thickness of optical filters necessary for the imaging device. As a result, the digital camera cannot be sufficiently thinned. In the retractable method, the lens structure needs to be extended when the camera is used, so that the structure of the lens barrel is complicated. As a result, there is a problem in that the image quality is greatly deteriorated and the cost is increased due to high manufacturing difficulty. Further, in the configuration in which the lens is extended after the camera power is turned on, it takes time until the preparation for photographing is completed, and there is a problem that the user misses the photographing opportunity.

  The digital camera can also be made thinner by devising the arrangement of the zoom lens system in the camera. In a general digital camera, the zoom lens system is arranged so that the largest surface of the housing faces the subject. When the zoom lens system is arranged in such a manner, the length of the zoom lens system becomes the thickness of the digital camera. It will greatly affect. Therefore, if a zoom lens system as described in Patent Document 2 is arranged so that its optical axis is parallel to the largest surface of the housing, the thickness of the digital camera depends on the length of the zoom lens system. Since it will not be influenced, the digital camera can be made thinner. However, the camera becomes elongated and becomes very difficult for the user to use. Although it is possible to improve the usability by rotating the lens barrel at the time of use, since a rotating mechanism is required, the thickness of the digital camera increases as a result. In addition, since troublesome rotating operation must be performed at the start of shooting and at the end of shooting, this is also not preferable.

  As described above, enabling the photographing with the largest surface of the housing facing the subject is a requirement for realizing a thin digital camera with excellent operability. As an optical configuration satisfying this requirement, zoom lens systems proposed in Patent Documents 3 to 7 can be cited. In the zoom lens systems described in Patent Documents 3 to 7, the optical path is bent by a prism or mirror inserted between the lenses so that the largest surface of the housing faces the subject. However, none of them is configured to make the digital camera sufficiently thin.

  For example, the zoom lens system described in Patent Document 3 has a zoom configuration in which the first group has positive power (so-called plus lead). The first group, the aperture stop, and the third group are fixed during zooming. The four groups are positive, negative, positive, and positive in order from the object side. Therefore, the lens barrel configuration can be simplified. However, the plus lead zoom configuration is suitable for a zoom lens system having a high zoom ratio, but in a zoom lens system having a zoom ratio of about 2 to 3, the number of lenses increases, Since the total length becomes large, the compactness is lost as a result.

  In the zoom lens system described in Patent Document 4, the first lens unit has a zoom configuration including an afocal system. Since the first group does not have paraxial power, effects such as aberration correction are small when viewed from the entire optical system. Therefore, the burden of aberration correction for other zoom groups is increased, resulting in an increase in cost and size due to an increase in the number of lenses. In the zoom lens system described in Patent Document 5, the mirror is deformed during zooming. The drive / control configuration for deforming the mirrors makes it difficult to reduce the thickness of the digital camera. In the zoom lens system described in Patent Document 6, a lens positioned closer to the object side than the mirror is configured to zoom. Since the zoom movement is performed in the vertical direction with respect to the largest surface of the housing, it is still difficult to reduce the thickness of the digital camera.

  The zoom lens system described in Patent Document 7 has a zoom configuration in which the first group has negative power (so-called minus lead). In addition, although it is a minus lead, a configuration in which three or more components are moved for zoom movement, and a configuration in which power is provided on the light incident side surface or the light emission side surface of the prism having a reflecting surface are adopted. Since the zoom ratio is about 3 times, it is suitable for downsizing, but moving a large number of groups (three or more) in zoom movement, even with a negative lead, results in a complicated lens barrel configuration. It becomes disadvantageous for thinning. Moreover, the zoom movement is not necessarily optimized, and it has a problematic configuration. In addition, since the reflecting prism is a component that requires high accuracy, if a curved surface is provided on the reflecting prism, post-processing may be required, high accuracy may be difficult to achieve, and costs may increase. Many problems arise. Therefore, in view of the processing accuracy that can be currently achieved, it can be said that it is advantageous in terms of performance and cost to separately manufacture and combine the prism and the lens.

  As described above, selecting a minus lead zoom type is a requirement for realizing a thin digital camera. As an optical configuration that satisfies this requirement, there are zoom lens systems proposed in Patent Documents 8 and 9. The zoom lens systems described in Patent Documents 8 and 9 have four groups of negative, positive, negative, and positive in order from the object side, and the zoom positions of the first group and the third group are fixed. However, none of them is configured to make the digital camera sufficiently thin.

  For example, in the zoom lens system described in Patent Document 8, the first group and the third group are fixed during zooming in a negative / positive / negative / positive four-group configuration, but the aperture stop is integrated with the third group. Therefore, the lens diameters of the first group and the second group are increased, making it difficult to reduce the thickness of the digital camera. In the case of the zoom lens system described in Patent Document 9, the first group and the third group are fixed during zooming in a negative, positive, negative, positive, and positive five-group configuration, but a projection lens system used for a liquid crystal projector or the like. Therefore, the zoom ratio is as small as about 1.5 times and the entire lens system is large. Therefore, the photographic lens system for a digital camera is not suitable in terms of size, specifications, and the like.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a thin imaging lens device including a high-performance and compact zoom lens system that satisfies high image quality.

  In order to achieve the above object, an imaging lens device according to a first aspect of the present invention includes a zoom lens system that is composed of a plurality of groups and performs zooming by changing the group interval, and an optical image formed by the zoom lens system. The zoom lens system includes, in order from the object side, a first group of negative power, a second group of positive power, and a negative power The zoom lens has at least a third lens group and a fourth lens group having positive power, and the first lens group and the third lens group are fixed with respect to the image plane during zooming from the wide-angle end to the telephoto end; The group moves to the object side, and the fourth group moves to the image side, or moves so as to draw a locus of a U-turn shape convex to the image side.

  The imaging lens device according to a second invention is characterized in that, in the first invention, the second group has an aperture stop.

  An imaging lens device according to a third aspect of the present invention is the imaging lens device according to the first or second aspect, wherein the first group has a reflecting member for bending the optical path, and the reflecting member has an optical axis of the zoom lens system of approximately 90 degrees. The light beam is reflected so as to be bent.

  The imaging lens device according to a fourth aspect of the present invention is the imaging lens device according to the first or third aspect, wherein the first group is a first lens having a negative power having an aspheric surface closest to the object side, and one lens closest to the image side. A negative lens and a cemented lens made up of one positive lens.

  An imaging lens device according to a fifth aspect of the present invention is the imaging lens device according to any one of the first to fourth aspects, wherein the fourth group includes at least one negative lens and at least one positive lens. Features.

  The imaging lens device according to a sixth aspect of the present invention is the imaging lens device according to any one of the first to fifth aspects, wherein focusing from an infinite object to a close object is performed by moving the fourth group to the object side. Features.

An imaging lens device according to a seventh invention is characterized in that, in any one of the first to sixth inventions, the following conditional expression (1) is satisfied.
-15.0 <f3 / fw <-2.0… (1)
However,
f3: focal length of the third group,
fw: Focal length of the entire zoom lens system at the wide-angle end,
It is.

An imaging lens device according to an eighth invention is characterized in that, in any one of the first to seventh inventions, the following conditional expression (2) is satisfied.
1.0 <(ft · m2w) / (fw · m2t)… (2)
However,
fw: Focal length of the entire zoom lens system at the wide-angle end,
ft: Focal length of the entire zoom lens system at the telephoto end,
m2w: imaging magnification of the second group at the wide angle end,
m2t: imaging magnification of the second group at the telephoto end,
It is.

  A camera according to a ninth aspect includes the imaging lens device according to any one of the first to eighth aspects.

  According to the present invention, in the zoom lens system having negative, positive, negative, and positive zoom groups in order from the object side, the first group and the third group are fixed during zooming with respect to the image plane, and the second group Zooms to the object side and the fourth lens unit zooms to the image side, or zooms so as to draw a convex U-turn locus on the image side, thereby zooming from the wide-angle end to the telephoto end. Therefore, a thin imaging lens device including a high-performance and compact zoom lens system that satisfies high image quality can be realized. If the imaging lens device according to the present invention is used in devices such as a digital camera and a personal digital assistant, it contributes to thin, light, compact, low cost, high performance, high functionality, etc. of these devices. Can do.

  Hereinafter, an imaging lens device and the like embodying the present invention will be described with reference to the drawings. An imaging lens device according to the present invention is an optical device that optically captures an image of a subject and outputs it as an electrical signal, and constitutes a main component of a camera used for still image shooting and moving image shooting of a subject. It is. Examples of such a camera include a digital camera; a video camera; a surveillance camera; an in-vehicle camera; a videophone camera; a doorphone camera; a personal computer, a mobile computer, a mobile phone, a personal digital assistant (PDA), These peripheral devices (mouse, scanner, printer, etc.), and cameras built in or externally attached to other digital devices can be mentioned. As can be seen from these examples, it is possible not only to configure a camera by using an imaging lens device, but also to add a camera function by mounting the imaging lens device in various devices. For example, a digital device with an image input function such as a mobile phone with a camera can be configured.

  The term “digital camera” used to refer to the recording of optical still images, but digital still cameras and home digital movie cameras that can handle still images and movies simultaneously have been proposed. In particular, it has become indistinguishable. Therefore, the term “digital camera” means a digital still camera, digital movie camera, or web camera (whether an open type or a private type, a camera that is connected to a network and connected to a device that enables image transmission / reception). , And the like, including those directly connected to a network and those connected via a device having an information processing function such as a personal computer.) All cameras including an imaging lens device including an imaging element or the like for converting the video signal into an electric video signal are included as main components.

  FIG. 13 shows a configuration example of the imaging lens device UT. The imaging lens device UT includes a zoom lens system (corresponding to a photographic lens system) TL that forms an optical image (IM: image plane) of an object in order from the object (that is, subject) side, and a parallel plane. Formed on the light receiving surface SS by a face plate PL (optical filters such as an optical low-pass filter and an infrared cut filter disposed as necessary; corresponding to a cover glass of the image sensor SR) and a zoom lens system TL. And an image sensor SR that converts the optical image IM into an electrical signal, and corresponds to a digital camera, a portable information device (that is, a small and portable information device terminal such as a mobile phone or a PDA), and the like. It forms part of the equipment CT. When a digital camera is configured with the imaging lens device UT, the imaging lens device UT is usually disposed inside the body of the camera. However, when realizing the camera function, it is possible to adopt a form as necessary. Is possible. For example, the unitized imaging lens device UT may be configured to be detachable or rotatable with respect to the camera body, and the unitized imaging lens device UT may be attached to or detached from a portable information device (such as a mobile phone or PDA). You may comprise freely or rotatably.

  In the imaging lens device UT shown in FIG. 13, a planar reflecting surface RL is disposed in the middle of the optical path in the zoom lens system TL, and at least one lens is disposed on each of the front side and the rear side of the reflecting surface RL. Has been. By this reflection surface RL, the optical path for using the zoom lens system TL as a bending optical system is bent, and at this time, the optical axis AX is bent by approximately 90 degrees (that is, 90 degrees or substantially 90 degrees). Thus, the light beam is reflected. If the reflection surface RL that bends the optical path is provided in the optical path of the zoom lens system TL in this way, the degree of freedom of arrangement of the imaging lens device UT increases, and the size in the thickness direction of the imaging lens device UT is changed. It is possible to achieve an apparent thinning of the imaging lens device UT.

  The reflection surface RL is constituted by a reflection member such as a prism (right angle prism or the like), a mirror (plane mirror or the like). For example, in the first to third embodiments to be described later, a right-angle prism is used as the reflecting member. However, the reflecting member to be used is not limited to the prisms, and a mirror such as a plane mirror is used as the reflecting member. The reflective surface RL may be configured. Further, a reflecting member that reflects a light beam so that the optical axis AX of the zoom lens system TL is bent by approximately 90 degrees with two or more reflecting surfaces may be used. The optical action for bending the optical path is not limited to reflection, but may be refraction, diffraction, or a combination thereof. That is, a bending optical member having a reflecting surface, a refracting surface, a diffractive surface, or a combination thereof may be used.

  The prism PR used in the first to third embodiments described later does not have optical power (power: an amount defined by the reciprocal of the focal length), but is an optical member that bends the optical path. You may give optical power. For example, if the optical power of the zoom lens system TL is partially borne on the reflecting surface RL, the light incident side surface, the light emitting side surface, and the like of the prism PR, the optical performance can be improved by reducing the power burden on the lens element. It becomes possible. In the first to third embodiments to be described later, the first lens L1 is arranged on the object side of the prism PR. However, instead of arranging the first lens L1, the object side surface of the prism PR (that is, the light incident side). The side surface) may be curved to have negative or positive power. Further, the bending position of the optical path may be any of the front side, the middle, and the rear side of the zoom lens system TL. The bending position of the optical path may be set as necessary, and the apparent thinness and compactness of the digital device (for example, digital camera) CT on which the imaging lens device UT is mounted can be achieved by appropriately bending the optical path. Is possible.

  In the first to third embodiments to be described later, a zoom lens system TL that includes a plurality of groups and performs zooming by changing the group interval is used as a photographing lens system. The zoom lens system TL constituting the first to third embodiments includes a negative power first group GR1, a positive power second group GR2, and a negative power third group GR3 in order from the object side. A fourth group GR4 having a positive power, and at least the first group GR1 and the third group GR3 are fixed groups. The second group GR2 and the fourth group GR4 are moving groups, and perform zooming of the zoom lens system TL by moving along the optical axis AX so as to change the interval between the groups. As shown in FIG. 13, using the zoom lens system TL as a bending optical system is effective in reducing the overall length of the zoom lens system TL and making the entire system compact. As a result, the imaging lens device UT can be effectively reduced in size and thickness.

  As the imaging element SR, for example, a solid-state imaging element such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) sensor having a plurality of pixels is used. Then, the optical image formed by the zoom lens system TL (on the light receiving surface SS of the image sensor SR) is converted into an electrical signal by the image sensor SR. The signal generated by the image sensor SR is subjected to predetermined digital image processing, image compression processing, etc. as necessary, and recorded as a digital video signal in a memory (semiconductor memory, optical disk, etc.), or in some cases via a cable. Or converted into an infrared signal and transmitted to another device.

  An optical image to be formed by the zoom lens system TL passes through an optical low-pass filter (corresponding to a parallel plane plate PL in FIG. 13) having a predetermined cutoff frequency characteristic determined by the pixel pitch of the image sensor SR. By doing so, the spatial frequency characteristic is adjusted so that the so-called aliasing noise generated when converted into an electrical signal is minimized. Thereby, generation | occurrence | production of a color moire can be suppressed. However, if the performance around the resolution limit frequency is suppressed, there is no need to worry about the occurrence of noise without using an optical low-pass filter, and the display system where the noise is not very noticeable (for example, the liquid crystal of a mobile phone) When a user performs shooting or viewing using a screen or the like, it is not necessary to use an optical low-pass filter in the shooting lens system. Therefore, in an imaging lens device that does not require an optical low-pass filter, if the exit pupil position can be appropriately arranged, it is possible to achieve downsizing of the imaging lens device and camera by shortening the back focus.

  As the optical low-pass filter, a birefringence low-pass filter, a phase low-pass filter, or the like can be applied. Examples of the birefringent low-pass filter include those made of a birefringent material such as quartz whose crystal axis direction is adjusted to a predetermined direction, and those obtained by laminating wave plates that change the polarization plane. Examples of the phase type low-pass filter include those that achieve the required optical cutoff frequency characteristics by the diffraction effect.

  1 to 3 are optical configuration diagrams respectively corresponding to the zoom lens systems TL constituting the first to third embodiments, and the lens arrangement, the optical path, and the like at the wide angle end (W) in the optical path expanded state. An optical cross section is shown. 4 to 6 are optical configuration diagrams respectively corresponding to the zoom lens systems TL constituting the first to third embodiments, and the lens arrangement at the wide-angle end (W), the optical path, and the like are bent in the optical path. The optical cross section is shown in FIG. 1 to 3, solid arrows m2 and m4 schematically show movements of the second group GR2 and the fourth group GR4 during zooming from the wide-angle end (W) to the telephoto end (T), respectively. m1, m3, and m5 indicate that the first group GR1, the third group GR3, and the fifth group GR5 are fixed in position during zooming. An arrow mF schematically shows the movement of the focus lens group from infinity shooting to short-distance shooting. 1 to 3, the surface with ri (i = 1,2,3, ...) is the i-th surface counted from the object side (the surface with ri marked with * is aspherical) ), And the axis top surface interval with di (i = 1, 2, 3,...) Is a variable interval that changes during zooming among the i-th axis surface interval counted from the object side.

  As described above, each of the zoom lens systems TL constituting the first to third embodiments, in order from the object side, the first group GR1 having negative power and the second group having positive power. By having a group GR2, a third group GR3 having a negative power, and a fourth group GR4 having a positive power, and changing each group interval using the second group GR2 and the fourth group GR4 as a movable group This is a zoom lens for imaging that performs zooming. Then, during zooming from the wide-angle end (W) to the telephoto end (T), the second group GR2 moves to the object side. That is, during zooming from the wide-angle end (W) to the telephoto end (T), the second group GR2 moves monotonously from the image side to the object side, thereby changing the relative position with respect to the image plane IM.

  The zoom movement of the fourth group GR4 differs between the first and second embodiments (FIGS. 1 and 2) and the third embodiment (FIG. 3). In the first and second embodiments, during zooming from the wide-angle end (W) to the telephoto end (T), the fourth group GR4 moves so as to draw a U-turn locus that is convex toward the image side. That is, during zooming from the wide-angle end (W) to the telephoto end (T), the fourth group GR4 first moves from the object side to the image side, and then moves from the image side to the object side near the telephoto end (T). By doing so, the relative position with respect to the image plane IM is changed. The change point of the zoom movement direction of the fourth group GR4 exists between the intermediate focal length state (M) and the telephoto end (T), as will be specifically shown later with data. In the third embodiment, the fourth lens group GR4 moves to the image side during zooming from the wide-angle end (W) to the telephoto end (T). That is, during zooming from the wide-angle end (W) to the telephoto end (T), the fourth group GR4 monotonously moves from the object side to the image side, thereby changing the relative position with respect to the image plane IM.

  The zoom lens system TL of the second and third embodiments (FIGS. 2 and 3) has a fifth group GR5. The fifth group GR5 is fixed in position during zooming. Therefore, it is essentially the same as the four component zoom of negative / positive / negative / positive. By disposing the lens group whose position is fixed most during the zooming, the performance can be improved based on the aberration correction advantage. In addition, since the moving group is not increased, there is no disadvantage in reducing the thickness of the imaging lens device UT or the like.

  As described above, in any of the embodiments, the first group GR1 and the third group GR3 are fixed groups, and are fixed during zooming together with the plane parallel plate PL and the image sensor SR, that is, from the wide angle end (W) to the telephoto end. The position is fixed with respect to the image plane IM during zooming up to (T). The second group GR2 has an aperture stop ST closest to the first group GR1, and moves as a part of the second group GR2 during zooming. With the configuration in which the aperture stop ST zooms as a part of the second group GR2, the diameter of the second group GR2, which is the moving group, is reduced, and the diameter of the first group GR1, which is the largest, is also reduced. Therefore, since the entire lens diameter and overall length of the zoom lens system TL can be reduced, the imaging lens device UT can be reduced in size and thickness.

  The lens configuration of the zoom lens system TL constituting the first to third embodiments will be described in detail below. In any of the embodiments, an optical filter (for example, an optical low-pass filter, red) is used as an imaging lens device UT used in a camera (corresponding to the digital device CT in FIG. 13) provided with an imaging element SR. Two glass plane parallel plates PL corresponding to the outer cut filter) are disposed on the image plane IM side of the zoom lens system TL.

  In the first embodiment (FIGS. 1 and 4), each group in the negative / positive / negative / positive four-group zoom configuration is configured as follows. The first group GR1 includes, in order from the object side, a first lens L1, a second lens L2, a third lens L3, and a prism PR inserted between the first lens L1 and the second lens L2. ing. The first lens L1 is composed of a negative meniscus lens having an aspheric surface on one side and is concave on the image side. The prism PR has a reflecting surface RL (FIGS. 4 and 13) for bending the optical axis AX by 90 degrees. Consists of. The second lens L2 is composed of a biconcave negative lens, the third lens L3 is composed of a positive meniscus lens convex on the object side, and the second lens L2 and the third lens L3 constitute a cemented lens. Yes. The second group GR2 includes, in order from the object side, an aperture stop ST, a biconvex positive lens, a cemented lens composed of a biconcave negative lens and a biconvex positive lens, and a single surface that is aspheric and concave on the image side. And a negative meniscus lens. The third group GR3 is composed of a negative meniscus lens having a double-sided aspherical surface and concave on the object side. The fourth group GR4 includes, in order from the object side, a biconvex positive lens LP having one aspheric surface and a negative meniscus lens LN concave on the object side.

  In the second embodiment (FIGS. 2 and 5), in the negative / positive / negative / positive / negative 5-group zoom configuration, each group is configured as follows. The first group GR1 includes, in order from the object side, a first lens L1, a second lens L2, a third lens L3, and a prism PR inserted between the first lens L1 and the second lens L2. ing. The first lens L1 is composed of a negative meniscus lens that is concave on the image side, one side of which is an aspheric surface, and the prism PR is a right-angle prism having a reflecting surface RL (FIGS. 5 and 13) for bending the optical axis AX by 90 degrees. Consists of. The second lens L2 is composed of a biconcave negative lens, the third lens L3 is composed of a positive meniscus lens convex on the object side, and the second lens L2 and the third lens L3 constitute a cemented lens. Yes. The second group GR2 includes, in order from the object side, an aperture stop ST, a biconvex positive lens whose one surface is an aspheric surface, a cemented lens composed of a positive lens and a negative lens, and a biconvex positive lens. ing. The third group GR3 is composed of a negative meniscus lens having a double-sided aspherical surface and concave on the object side. The fourth group GR4 includes, in order from the object side, a biconvex positive lens LP and a negative meniscus lens LN concave on the image side. The fifth group GR5 is composed of a negative lens having one surface that is flat and concave on the object side.

  In the third embodiment (FIGS. 3 and 6), each group is configured as follows in a negative / positive / negative / positive / negative 5-group zoom configuration. The first group GR1 includes, in order from the object side, a first lens L1, a second lens L2, a third lens L3, and a prism PR inserted between the first lens L1 and the second lens L2. ing. The first lens L1 is composed of a negative lens which is concave on the object side and whose object side surface is an aspherical surface and whose image side surface is a flat surface. The prism PR is composed of a right-angle prism having a reflecting surface RL (FIGS. 6 and 13) for bending the optical axis AX by 90 degrees, and is joined to the first lens L1. The second lens L2 is composed of a biconcave negative lens having an aspheric object side surface, the third lens L3 is composed of a biconvex positive lens, and a cemented lens is formed by the second lens L2 and the third lens L3. It is composed. In order from the object side, the second group GR2 includes an aperture stop ST, a positive meniscus lens convex on the object side, a cemented lens including a biconcave negative lens and a biconvex positive lens, and a double-sided aspheric surface on the image side. And a convex positive meniscus lens. The third group GR3 is composed of a biconcave negative lens. The fourth group GR4 includes, in order from the object side, a negative meniscus lens LN that is concave on the object side, and a biconvex positive lens LP that has a double-sided aspheric surface. The fifth group GR5 includes a negative meniscus lens that is concave on the object side.

  In general, a negative / positive / positive or negative / positive / negative / positive negative lead zoom lens system is not suitable for high zooming of 5 to 10 times. This is because, when zooming at a high zoom ratio is performed, the lens diameters of the first group and the second group at the telephoto end are increased. However, in the case of a zoom lens system having a zoom ratio of about 3 times as in the first to third embodiments, compared to a zoom lens system in which the first group has positive power (so-called plus lead). It is known that the number of lens groups is small and the decentration error sensitivity is small. Furthermore, if a fixed group having negative power is arranged between two moving groups, it is possible to improve the optical performance and further reduce the overall eccentric error sensitivity without increasing the number of moving groups. Therefore, the negative / positive / negative / positive zoom configuration employed in the first to third embodiments is preferable because it has advantages such as a small manufacturing error and a small number of lens groups.

In order to achieve the above performance improvement and sensitivity reduction, it is necessary that the power of the third lens group GR3 is optimally arranged. Specifically, it is desirable that the following conditional expression (1) is satisfied.
-15.0 <f3 / fw <-2.0… (1)
However,
f3: focal length of the third group,
fw: Focal length of the entire zoom lens system at the wide-angle end,
It is.

  Conditional expression (1) defines a preferable condition range regarding the power of the third lens group. Exceeding the lower limit of conditional expression (1) is not preferable because the power of the third lens group becomes weak and the effect of achieving performance improvement and sensitivity reduction by arranging the fixed third lens group becomes small. On the contrary, if the upper limit of conditional expression (1) is exceeded, the power of the third group becomes too strong, so that the aberration generated in the third group becomes too large and it becomes difficult to correct the aberration of the entire optical system. turn into.

It is more desirable to satisfy the following conditional expression (1a).
-10.0 <f3 / fw <-4.0… (1a)
The conditional expression (1a) defines a more preferable condition range based on the above viewpoints, etc., among the condition ranges defined by the conditional expression (1). When this conditional expression (1a) is satisfied, it becomes possible to obtain a better optical performance and to realize a lower sensitivity.

  Further, a lens group (for example, a lens group having a condenser function) whose position is fixed with respect to the image plane IM during zooming from the wide-angle end (W) to the telephoto end (T) may be disposed near the image plane IM. . If a positive power or negative power lens group with a fixed position during zooming is added near the image plane IM, a slight performance improvement is expected. Even in that case, it is possible to obtain the same effect as the zoom lens system TL employed in the first to third embodiments.

  As in the first to third embodiments (FIGS. 1 to 6), it is preferable that the first group GR1 is fixed during zooming. That is, in order from the object side, the zoom lens includes the negative power first group GR1, the second group GR2 with positive power, the third group GR3 with negative power, and the fourth group GR4 with positive power. It is preferable that the first lens group GR1 is fixed with respect to the image plane IM during the zooming from the wide-angle end (W) to the telephoto end (T). By fixing the first group GR1 during zooming, the length in the optical axis AX direction on the incident side of the zoom lens system TL can be shortened. Therefore, it is possible to achieve a reduction in size and increase in the magnification of the zoom lens system TL and a reduction in the thickness of the imaging lens device UT and the digital device (digital camera or the like) CT.

  Since the first group GR1 includes the reflection surface RL, a large space is required to move the first group GR1. In particular, when the reflecting surface RL is composed of the prism PR, if a heavy prism PR is moved, a large burden is imposed on the driving mechanism. If the zoom position of the first lens group GR1 at the time of zooming is fixed with respect to the image plane IM as described above, such a problem does not occur and the total length does not change (that is, the thickness due to zooming or collapsing). A zoom lens system in which no change occurs can be obtained. If the entire length of the zoom lens system does not change, the entire zoom lens system can be held with a box-type structure, and therefore the zoom lens system can be held with a highly rigid structure.

  Negative / positive / negative / positive zoom lens systems are roughly classified into two types with respect to movement in zooming. In the first type, during zooming from the wide-angle end to the telephoto end, the second group and the fourth group move together toward the object side at different speeds. In the second type, during zooming from the wide-angle end to the telephoto end, the second group moves toward the object side, the fourth group moves linearly toward the image side, or a U-turn shape that is convex toward the image side. Move along a trail. The reason why the zoom movement differs greatly between the two types is that there is a great difference in the variable magnification burden of each group.

  In the case of the first type, the second group performs multiplication and the third group performs multiplication. In such a case, the zooming load of the second group becomes larger than the zooming ratio of the entire system, and the aberration fluctuation generated in the second group becomes large, which is not preferable. In the case of the second type, since the zooming is shared between the second group and the fourth group, the aberration variation during zooming is small. Therefore, good aberration performance can be obtained over the entire zoom range even with a small number of lenses. Therefore, as in the first to third embodiments, during zooming from the wide-angle end (W) to the telephoto end (T), the second group GR2 moves to the object side, and the fourth group GR4 moves to the image side. Alternatively, it is preferable to move so as to draw a convex U-turn locus on the image side. However, the movement of the second group GR2 toward the object side is linear (that is, monotonous) with respect to the movement of the fourth group GR4 that draws a convex U-turn shape locus on the image side.

In order to perform the second type of zooming, it is necessary that the zooming load of the second group is smaller than the zooming load of the entire system. Specifically, it is desirable that the following conditional expression (2) is satisfied. If the lower limit of the conditional expression (2) is exceeded, the variable magnification burden of the second lens group GR2 becomes too large, and it becomes difficult to obtain good performance.
1.0 <(ft · m2w) / (fw · m2t)… (2)
However,
fw: Focal length of the entire zoom lens system at the wide-angle end,
ft: Focal length of the entire zoom lens system at the telephoto end,
m2w: imaging magnification of the second group at the wide angle end,
m2t: imaging magnification of the second group at the telephoto end,
It is.

  As described above, the zoom lens systems TL of the first to third embodiments have the prism PR as the reflecting member in the first group GR1. The prism PR (FIGS. 1 to 6) used in the first to third embodiments is a right-angle prism, and the reflecting surface RL (FIG. 13) is configured by the prism PR. That is, as shown in FIGS. 4 to 6, the prism PR is configured to reflect the light beam by the internal reflection surface RL so that the optical axis AX of the zoom lens system TL is bent by approximately 90 degrees. The prism PR is not limited to a right-angle prism, and for example, may be one that reflects a light beam so that the optical axis AX of the zoom lens system is bent by approximately 90 degrees with two or more reflecting surfaces.

  The screen shape of a normal image sensor is a rectangle, and the screen shape of the image sensor SR used in the first to third embodiments is also a rectangle with a ratio of long side: short side = 4: 3. . For this reason, in order to achieve thinning of the imaging lens device UT, it is preferable to bend the optical path in the short side direction of the imaging element SR. The bending direction of the optical path shown in FIGS. 4 to 6 is the short side direction of the image sensor SR. In FIGS. 1 to 3, the optical path is expressed by expressing the prism PR as a parallel plane plate. It is shown in a linearly expanded state.

  The prism PR used in the first to third embodiments is an internal reflection prism, but is not limited thereto. As the reflection member constituting the reflection surface RL, any reflection member such as a surface reflection prism, an internal reflection flat plate mirror, or a surface reflection flat plate mirror may be employed. The internal reflection prism reflects the object light inside the prism, whereas the surface reflection prism reflects the object light with the prism surface as a reflection surface without causing the object light to enter the prism. The front reflection flat mirror reflects the object light with the mirror surface as a reflection surface, whereas the internal reflection flat mirror reflects the object light incident on the glass plate with the back surface of the glass plate as a reflection surface. .

  In order to achieve a reduction in the thickness of a digital device CT (FIG. 13) such as a digital camera or a portable information device, an internal reflecting prism is the most suitable among the reflecting members. When the internal reflection prism is employed, the object light passes through the prism medium, so that the surface interval when the object light passes through the prism is physically shortened. For this reason, when an internal reflection prism is employed in the configuration of the reflecting surface RL, it is preferable because an optically equivalent configuration can be achieved in a more compact space. Further, the reflection surface RL may not be a complete total reflection surface. That is, a part of the object light may be branched by appropriately adjusting the reflectance of a part of the reflecting surface RL and may be incident on the photometric sensor or the distance measuring sensor. Furthermore, the finder light may be branched by appropriately adjusting the reflectance of the entire reflecting surface RL.

  When the optical elements such as the lens and the diaphragm included in the zoom lens system are linearly arranged without changing the direction of the optical axis as in the conventional imaging lens device, the size in the thickness direction of the imaging lens device is It is practically determined by the size from the optical element on the most object side of the zoom lens system to the image sensor. However, due to the improvement of the image processing capability of semiconductor elements and the like, the imaging lens device mounted on a personal computer, mobile computer, mobile phone, portable information terminal, etc. is not as simple as the conventional one, but has a higher pixel, An imaging lens device having high magnification and high image quality has been demanded. For this reason, the number of lens elements of the zoom lens system included in the imaging lens device is also increasing, and it is difficult to achieve a reduction in thickness due to the thickness of the lens element even when not in use (so-called collapsed state). Yes.

  On the other hand, as in the zoom lens system TL constituting the first to third embodiments, if a configuration is adopted in which object light is reflected by the reflecting surface RL and the optical axis AX is bent by approximately 90 degrees, It is possible to reduce the size of the imaging lens device UT in the thickness direction to the size from the first lens L1 located closest to the object side to the reflecting surface RL. Therefore, it is possible to achieve an apparent thinning and downsizing of the imaging lens device UT. Further, when a configuration in which the optical axis AX is bent by approximately 90 degrees on the reflection surface RL is adopted, the optical path of the object light can be superimposed in the vicinity of the reflection surface RL, so that the space can be used effectively, and the imaging lens device Further downsizing of the UT can be achieved.

  As in the first to third embodiments, the position of the reflection surface RL is preferably inside the first group GR1. By disposing the reflecting surface RL inside the first group GR1 disposed on the most object side, the size of the imaging lens device UT in the thickness direction can be minimized. If necessary, the bending angle of the optical axis AX may be set to an angle other than 90 degrees, but the imaging lens device UT can be made more compact as the bending angle of the optical axis AX is closer to 90 degrees. become. Therefore, the bending angle of the optical axis AX is preferably as close to 90 degrees.

  As described above, the first group GR1 includes the prism PR that reflects the light beam as the reflecting member so as to bend the optical axis AX of the zoom lens system TL by approximately 90 degrees, but the first to third embodiments. As in the zoom lens system TL, it is preferable to dispose a negative power first lens L1 having an aspheric surface on the object side of the reflecting member. The lens arranged on the object side of the reflecting member such as the prism PR is a single lens, that is, by arranging only the first lens L1 as the optical element having power on the object side of the reflecting member, the optical axis AX is changed. The width of the bent zoom lens system TL (that is, the length in the optical axis AX direction on the incident side of the zoom lens system TL) can be reduced, and the imaging lens device UT can be thinned. . Further, by using a negative lens as the first lens L1, it becomes possible to widen the angle of view and reduce the front lens diameter.

  In the first to third embodiments, the light incident side surface and the light emission side surface of the prism PR are both flat. In the third embodiment, the light emission side surface of the first lens L1 is also a flat surface. ing. Moreover, in the third embodiment, the light emission side surface of the first lens L1 and the light incident side surface of the prism PR are joined (that is, the surface interval is zero). The prism PR and the first lens L1 have different refractive indexes. However, if the refractive indexes of the prism PR and the first lens L1 are the same, they can be processed integrally. However, this means that the light incident side surface of the prism is not a flat surface but a curved surface. Therefore, when considering glass molding / plastic injection molding technology and prism post-processing, there are significant issues to be solved in manufacturing, and cost increases due to performance degradation due to manufacturing errors during integrated processing and difficulty in manufacturing integrated processing. This is not preferable because of concern.

  In the zoom lens system TL in which the first lens group GR1 has negative power as in the first to third embodiments, it is generally very difficult to correct distortion and field curvature that occur at the wide angle end (W). . It is usually possible to solve this problem by increasing the number of lenses, but if the number of lenses is increased, the aberration performance may be reduced. For example, as in the first embodiment, when the prism PR is inserted between the first lens L1 and the cemented lenses L2 and L3, the image side principal point of the first group GR1 is compared with the case where the prism PR is not provided. The position moves greatly to the object side, and the power becomes weak. In order to obtain the same power, it is necessary to increase the power of each lens. However, when the power is increased, the field curvature is further increased. In the first to third embodiments, an aspheric surface is introduced into the first lens L1 to correct distortion, astigmatism, and the like that occur in the configuration. Moreover, since the power of the first lens L1 can be increased by introducing an aspherical surface to the first lens L1, the optical path width at the reflecting member can be reduced as a result. In order to obtain this effect, it is desirable to introduce into the first lens L1 an aspheric surface in which the negative power of the first lens L1 becomes weaker as the distance from the optical axis AX increases.

  If the first lens group GR1 is composed of only the first lens L1 and the reflecting member (for example, the prism PR), the zoom lens system TL becomes compact, but it becomes difficult to correct chromatic aberration and other aberrations. In order to correct various aberrations satisfactorily, the first group GR1 includes a lens group including at least one negative lens and at least one positive lens on the image side of the reflecting member such as the prism PR. preferable. Accordingly, the first group GR1 includes, in order from the object side, a negative power first lens L1 having an aspherical surface and a reflecting member such as a prism PR that reflects a light beam so that the optical axis AX of the zoom lens system TL is bent by approximately 90 degrees. And a lens group including at least one negative lens and at least one positive lens. This makes it possible to correct chromatic aberration, distortion, astigmatism and the like with a compact configuration. In addition, it is preferable that at least one negative lens and a positive lens are cemented because manufacturing errors can be reduced. The lens group (in the first group GR1) disposed on the image side of the reflecting member more preferably has positive power.

  In order to satisfactorily correct chromatic aberration and the like in the first group GR1, as in the first to third embodiments, on the image side of the reflecting member such as the prism PR in the first group GR1. It is preferable that the cemented lens formed by the second lens L2 made of a negative lens and the third lens L3 made of a positive lens is arranged as the lens group, and has a biconcave shape as in the third embodiment. More preferably, a cemented lens including a second lens L2 made of a negative lens and a third lens L3 made of a biconvex positive lens is arranged as the lens group. Since the cemented lens can be easily incorporated into the zoom lens system, if a cemented lens composed of two negative and positive lenses is arranged on the image side of the reflecting member, distortion and astigmatism can be achieved with a simple and compact configuration. It becomes possible to correct aberrations satisfactorily.

  As described above, in the zoom lens systems TL of the first to third embodiments, the first group GR1 and the third group GR3 (and the fifth group GR5) are fixed during zooming, and the second group GR2 The fourth group GR4 performs zooming by zooming. In a negative / positive / negative / positive zoom lens system, the aberration variation is corrected by the zoom movement of the first group, so that the fourth group has a single lens configuration. However, when the first group is fixed at the zoom position, the aberration fluctuation with respect to the fourth group becomes considerably large, and it is difficult to correct the aberration fluctuation during zooming with a single lens configuration. Therefore, as in the first to third embodiments, it is preferable that the fourth group GR4 is configured by at least one negative lens LN and at least one positive lens LP. If at least one negative lens LN and one positive lens LP are used in this way, chromatic aberration and the like can be corrected, so that good performance can be ensured.

  As in the first to third embodiments, having an aperture stop ST or shutter closer to the image side than the prism PR is effective in reducing the size and thickness of the imaging lens device UT. In addition, in order to reduce the thickness of a digital camera, it is necessary that optical components such as lenses and prisms can be arranged in a thin region, but in addition to this, the configuration including the lens barrel and driving components must be compact. . In the first to third embodiments, the aperture stop ST is disposed on the most object side in the second group GR2, and is configured to zoom as a part of the second group GR2. In a normal digital camera, a mechanical shutter is arranged at the position of the aperture stop ST. However, when using a mechanical shutter, it is necessary to secure a place for the light shielding portion to retract, and a driving element such as a driving motor is also required. . Therefore, a considerably large space is required.

  When the aperture stop ST zooms together with the moving group as in the first to third embodiments, if a mechanical shutter that requires a large space is mounted on the moving group, the moving group itself becomes large. In addition, an excessive burden is placed on the drive unit, which may result in a very large configuration as a whole. In other words, even if only the optical component is compact, it may be difficult to reduce the size depending on the configuration. Therefore, in the first to third embodiments, it is preferable not to mount the shutter mechanism in the moving group for downsizing including the mechanical configuration. In addition, it is preferable to dispose a shutter mechanism on the image plane IM side of the third group GR3 whose zoom position is fixed. Note that if a solid-state imaging device having an electronic shutter function is used as the imaging device SR, the imaging lens device UT can be further reduced in size.

  In the first to third embodiments, as shown by the arrow mF (FIGS. 1 to 3), the fourth group GR4 is moved to the object side to perform focusing from an infinite object to a close object. It has become. Conventionally, lens driving for zooming has been performed by transmitting the power of one driving device to a plurality of moving lens groups through a zoom cam. Focusing is performed by moving the focus lens group using another driving device. However, if there are two lens groups that move by zooming or focusing as in the first to third embodiments, the driving device can be directly connected to each of the two lens groups without using a cam or the like. . If zooming or focusing is performed by controlling the movement amount of each lens group, the cam is not necessary, so that the configuration can be simplified and the thickness can be reduced. In addition, as described above, the fourth group GR4 is configured using at least one negative lens LN and one positive lens LP, and focusing when performing close-up shooting is performed by extending the fourth group GR4 to the object side. This is preferable because aberration fluctuations during focusing can be reduced.

  The zoom lens system constituting the first to third embodiments includes a refractive lens that deflects incident light by refraction (that is, a type in which deflection is performed at the interface between media having different refractive indexes). Lens) is used, but a usable lens is not limited 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. However, it is desirable to use a homogeneous material lens having a uniform refractive index distribution, because the refractive index distribution type lens whose refractive index changes in the medium increases the cost of its complicated manufacturing method. In addition to the aperture stop ST, a light flux restricting plate or the like for cutting unnecessary light may be disposed as necessary.

  Each embodiment described above and each example to be described later include the following configuration. According to the configuration, a zoom lens system that achieves good optical performance and achieves miniaturization is realized. can do. And by using it as a photographic lens system for digital cameras, portable information devices (cell phones, PDAs, etc.), it contributes to lightening, compactness, low cost, high performance and high functionality of the devices. be able to.

  (Z1) In order from the object side, it has at least a first group of negative power, a second group of positive power, a third group of negative power, and a fourth group of positive power, from the wide-angle end to the telephoto end During zooming, the first group and the third group are fixed with respect to the image plane, the second group moves toward the object side, and the fourth group moves toward the image side, or the image side A zoom lens system that moves so as to draw a convex U-turn locus.

  (Z2) The zoom lens system according to (Z1), wherein the second group has an aperture stop.

  (Z3) The (Z1) or the above, wherein the first group has a reflecting member for bending the optical path, and the reflecting member reflects the light beam so as to bend the optical axis of the zoom lens system by approximately 90 degrees. The zoom lens system according to (Z2).

  (Z4) The first group includes, in order from the object side, a negative power first lens having an aspherical surface, the reflecting member, and a cemented lens including one negative lens and one positive lens. The zoom lens system according to (Z3) above, wherein

  (Z5) The zoom lens according to any one of (Z1) to (Z4), wherein the fourth group includes at least one negative lens and at least one positive lens. system.

  (Z6) The zoom lens according to any one of (Z1) to (Z5), wherein focusing is performed from an object at infinity to a close object by moving the fourth group toward the object side. system.

  (Z7) The zoom lens system according to any one of (Z1) to (Z6), wherein at least one of the conditional expressions (1), (1a), and (2) is satisfied.

  (Z8) The zoom lens system according to any one of (Z1) to (Z7), further including an aperture stop or a shutter closer to the image side than the prism.

  (U1) The zoom lens system according to any one of (Z1) to (Z8) above, and an image sensor that converts an optical image formed by the zoom lens system into an electrical signal. An imaging lens device characterized by the above.

  (C1) A camera comprising the imaging lens device according to (U1) and used for at least one of still image shooting and moving image shooting of a subject.

  (C2) A digital camera; a video camera; or a camera as described in (C1) above, which is a mobile phone, a personal digital assistant, a personal computer, a mobile computer, or a camera built in or externally attached to these peripheral devices .

  (D1) A digital device provided with the imaging lens device according to (U1), to which at least one of a still image shooting and a moving image shooting function is added.

  (D2) The digital device described in (D1) above, which is a mobile phone, a personal digital assistant, a personal computer, a mobile computer, or a peripheral device thereof.

  Hereinafter, the configuration of the zoom lens system used in the imaging lens apparatus embodying the present invention will be described more specifically with reference to construction data and the like. Examples 1 to 3 listed here are numerical examples corresponding respectively to the first to third embodiments described above, and are optical configuration diagrams showing the first to third embodiments (FIGS. 1 to 3). 6) shows the lens configurations of the corresponding first to third embodiments.

Tables 1 to 6 show construction data of Examples 1 to 3, and Table 7 shows data corresponding to parameters defined in each conditional expression and related data for each example. In Tables 1, 3 and 5, λ ₀ is the design wavelength (unit: nm), and Y′max is the maximum image height (the distance from the optical axis AX) on the light receiving surface SS of the image sensor SR. : mm), f, and Fno respectively indicate the focal length (unit: mm) and F number of the entire system corresponding to each focal length state (W), (M), (T). W is the wide angle end (shortest focal length state), M is the middle (intermediate focal length state), and T is the telephoto end (longest focal length state).

  In the basic optical configuration (i: surface number) from the object plane OB to the image plane IM in Table 1, Table 3, and Table 5, ri (i = 0, 1, 2, 3, ...) is the object. Radius of curvature of the i-th surface counting from the side (unit: mm), di (i = 0,1,2,3, ...) is the i-th surface and (i + 1) -th counting from the object side Is the distance between the upper surfaces of the axes (unit: mm) (d0: object distance), Ni (i = 1,2,3, ...), νi (i = 1,2,3, (...) indicates the refractive index (Nd) and the Abbe number (νd) of the optical material positioned at the axial upper surface distance di with respect to the d-line. Each embodiment is an example in which an optical low-pass filter (corresponding to the plane parallel plate PL) exists, but as described above, the optical low-pass filter can be omitted as appropriate.

Surfaces marked with * in the data of the radius of curvature ri are aspheric surfaces (aspherical refractive optical surfaces, surfaces having a refractive action equivalent to aspherical surfaces, etc.), and represent the following aspherical surface shapes: It is defined by the formula (AS). Tables 2, 4 and 6 show aspherical data of each example. However, the coefficient of the term not described is 0, and E−n = × 10 ⁻ⁿ and E + n = × 10 ^{+ n} for all data. In addition, the air interval marked with # in the data of the shaft upper surface interval di is a variable interval that changes due to zooming or focusing. Table 2, Table 4, and Table 6 show the variable interval data of each example. POS1, POS2, POS3 are in focus at infinity, POS4, POS5, POS6 are in focus at close distance, POS1, POS4 are at wide angle end (W), POS2, POS5 are middle (M), POS3, POS6 are at telephoto end ( The variable interval data at T) is shown respectively.

x = (C0 ・ y ² ) / [1+ {1- (1 + K) ・ C0 ²・ y ² } ^1/2 ] + Σ (Aj ・ y ^j )… (AS)
However, in the formula (AS)
x: Displacement amount in the optical axis AX direction at the position of height y (based on the surface vertex),
y: height in a direction perpendicular to the optical axis AX,
C0: Paraxial curvature (= 1 / ri),
K: cone coefficient,
Aj: j-order aspheric coefficient,
It is.

  7 to 12 are aberration diagrams of Examples 1 to 3, and POS1, POS2, and POS3 in FIGS. 7, 9, and 11 show various aberrations in the infinitely focused state of Examples 1 to 3, respectively. 8, 10, and 12, POS 4, POS 5, and POS 6 indicate various aberrations in the close-in-focus state in Examples 1 to 3, respectively. (A) to (C) are the wide angle end (W), (D) to (F) are the middle (M), and (G) to (I) are the various aberrations at the telephoto end (T). Yes.

7 to 12, (A), (D), (G) are spherical aberration diagrams, (B), (E), (H) are astigmatism diagrams, (C), (F), (I). ) Is a distortion diagram. The spherical aberration diagram shows the amount of spherical aberration with respect to the d line (wavelength 587.56 nm: λ ₀ ) indicated by the line d, the amount of spherical aberration with respect to the C line (wavelength 656.28 nm) indicated by the line C, and the g line indicated by the line g (wavelength 435.84 nm). ) Is expressed by the amount of deviation in the optical axis AX direction from the paraxial image plane (horizontal axis, unit: mm), and the vertical axis indicates the height of incidence on the pupil as its maximum height. Value (ie, relative pupil height). In the astigmatism diagram, the broken line DT is the tangential image surface with respect to the d line, the solid line DS is the sagittal image surface with respect to the d line, and the amount of deviation in the optical axis AX direction from the paraxial image surface (horizontal axis, unit: mm). The vertical axis represents the image height (IMG HT, unit: mm). In the distortion diagram, the horizontal axis represents distortion (%) with respect to the d-line, and the vertical axis represents image height (IMG HT, unit: mm).

1 is an optical configuration diagram showing an optical path and a lens configuration of a first embodiment (Example 1) in an optical path developed state. FIG. The optical block diagram which shows the optical path and lens structure of 2nd Embodiment (Example 2) in an optical path expansion | deployment state. The optical block diagram which shows the optical path and lens structure of 3rd Embodiment (Example 3) in an optical path expansion | deployment state. FIG. 3 is an optical configuration diagram showing the optical path and lens configuration of the first embodiment (Example 1) in a bent optical path state. The optical block diagram which shows the optical path and lens structure of 2nd Embodiment (Example 2) in an optical path bending state. The optical block diagram which shows the optical path and lens structure of 3rd Embodiment (Example 3) in an optical path bending state. FIG. 6 is an aberration diagram in Example 1 when focused on infinity. FIG. 6 is an aberration diagram for Example 1 in the close distance in-focus state. FIG. 6 is an aberration diagram in Example 2 when focused on infinity. FIG. 6 is an aberration diagram in Example 2 when the proximity distance is in focus. FIG. 6 is an aberration diagram for Example 3 in the infinitely focused state. FIG. 6 is an aberration diagram for Example 3 in the close distance in-focus state. 1 is a schematic diagram showing a schematic optical configuration of an imaging lens device according to the present invention.

Explanation of symbols

CT digital equipment (camera)
UT imaging lens device TL zoom lens system GR1 first group GR2 second group GR3 third group GR4 fourth group GR5 fifth group L1 to L3 first to third lenses LP positive lens LN negative lens PR prism (reflective member)
RL Reflecting surface ST Aperture stop PL Parallel plane plate SR Image sensor SS Light receiving surface IM Image surface AX Optical axis

Claims (9)

  An imaging lens apparatus comprising a zoom lens system that includes a plurality of groups and performs zooming by changing a group interval, and an imaging element that converts an optical image formed by the zoom lens system into an electrical signal. The zoom lens system includes, in order from the object side, at least a first group of negative power, a second group of positive power, a third group of negative power, and a fourth group of positive power. During zooming from the end to the telephoto end, the first group and the third group are fixed with respect to the image plane, the second group moves to the object side, and the fourth group moves to the image side. Or an imaging lens apparatus that moves so as to draw a U-turn locus convex toward the image side.   The imaging lens device according to claim 1, wherein the second group includes an aperture stop.   3. The imaging according to claim 1, wherein the first group includes a reflecting member for bending the optical path, and the reflecting member reflects the light flux so as to bend the optical axis of the zoom lens system by approximately 90 degrees. Lens device.   The first group includes a negative power first lens having an aspheric surface closest to the object side, and a cemented lens including one negative lens and one positive lens closest to the image side. The imaging lens device according to claim 1, wherein:   5. The imaging lens device according to claim 1, wherein the fourth group includes at least one negative lens and at least one positive lens. 6.   The imaging lens device according to claim 1, wherein focusing is performed from an object at infinity to a close object by moving the fourth group toward the object side. The imaging lens device according to any one of claims 1 to 6, wherein the following conditional expression (1) is satisfied;
-15.0 <f3 / fw <-2.0… (1)
However,
f3: focal length of the third group,
fw: Focal length of the entire zoom lens system at the wide-angle end,
It is. The imaging lens device according to claim 1, wherein the following conditional expression (2) is satisfied:
1.0 <(ft · m2w) / (fw · m2t)… (2)
However,
fw: Focal length of the entire zoom lens system at the wide-angle end,
ft: Focal length of the entire zoom lens system at the telephoto end,
m2w: imaging magnification of the second group at the wide angle end,
m2t: imaging magnification of the second group at the telephoto end,
It is.   A camera comprising the imaging lens device according to claim 1.

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