JP2005070437A - Zoom optical system, image input device and personal digital assistant device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom optical system capable of suppressing performance degradation, such as eccentricity, constituted of a small number of lenses, made bright, and varying power with high power from a wide angle side, while adopting the configuration of five or more groups whose focal distances are positive, negative, positive, positive and positive in the order starting from the object side. <P>SOLUTION: The zoom optical system is equipped with the 1st group I having the positive focal distance, the 2nd group II having the negative focal distance, the 3rd group III having the positive focal distance, the 4th group IV having the positive focal distance, and the 5th group V having the positive focal distance in order from the object side, and is also equipped with a diaphragm 21 on the object side of the 3rd group III. In the zoom optical system, the 2nd group II is fixed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a zoom optical system, an image input device, and an information terminal device, and more particularly to an improvement of a zoom optical system using five or more lens groups.

  2. Description of the Related Art In recent years, digital cameras with integrated lenses (as an image input device) are mainly provided with a zoom optical system having a zoom ratio of approximately 62 to 3 times as a photographing optical system. This is because the front lens diameter and total lens length of the photographing lens can be made compact by suppressing the angle of view and the zoom ratio to this extent.

  However, the zoom optical system that is normally used in traditional silver halide cameras has a high zoom ratio of about 74 to 3 to 5 times, which is a wider angle of view than that for digital cameras. For cameras, there is a demand for zoom optical systems having specifications equivalent to or higher than those for silver halide cameras, that is, a wide angle of view and a high zoom ratio.

Here, as a zoom optical system of five groups in which the focal length (refractive power) is positive, negative, positive, positive, positive in order from the object side, for example, the angle of view is about 64 degrees and the zoom ratio is about 3 times. A zoom lens (Patent Document 1), a zoom lens (Patent Document 2) with a zoom ratio of 11 times or more from an angle of view of about 70 degrees, and a zoom lens (Patent Documents 3 and 4 with an image angle of about 74 degrees to a zoom ratio of about 10 times) Etc.) have been proposed.
JP-A-57-195213 Japanese Patent No. 3352804 Japanese Patent Laid-Open No. 10-161028 JP 2002-098893 A

  Incidentally, the zoom lens disclosed in Patent Document 1 is composed of 18 or more lenses, and there is a problem that the number of constituent lenses is large. Further, the zoom ratio is only about 3 times, and the high magnification requirement cannot be satisfied.

  In the zoom lens disclosed in Patent Document 2, the first group, the third group, and the fifth group are fixed at the time of zooming, and the number of constituent lenses is as small as 11, but a video camera or the like is photographed. Although it is sufficient for use, it cannot be said that it has sufficient lens performance for still image shooting such as still cameras. Therefore, it is difficult to obtain the resolving power corresponding to the imaging element of 3 to 5 million pixel class with the configuration and refractive power arrangement of the zoom lens disclosed in Patent Document 2 as it is.

  On the other hand, although the zoom lens disclosed in Patent Document 3 has an angle of view of about 74 degrees and a zoom ratio of 10 times or more, the minimum value of the F-number is 4.1 and is dark.

  In the zoom lens disclosed in Patent Document 4, since there is almost no movement in which the third group and the fourth group approach each other at the time of zooming, the focal length is positive, negative, positive in order from the object side. There is substantially no difference from the positive four-group zoom optical system, and the merit of the five-group configuration by bringing the third group and the fourth group close to each other is not utilized.

  Further, for example, in Japanese Patent Application Laid-Open No. 2002-156581, a zoom ratio of about 5 times is realized from about 64 degrees, and the number of constituent lenses is as small as about 10, but in terms of angle of view, further widening of the angle is possible. desired.

  In order to realize such an improvement in performance, it is necessary to suppress factors of performance degradation such as eccentricity between the zoom optical system and various housings to which the zoom optical system is attached.

  The present invention has been made in view of the above circumstances, and suppresses performance deterioration such as eccentricity while adopting a configuration of five or more groups in which the focal length is positive, negative, positive, positive, positive in order from the object side. Accordingly, an object of the present invention is to provide a zoom optical system that is bright and can be changed from a wide angle side at a high magnification with a small number of constituent lenses.

  In addition, the present invention adopts a configuration of five or more groups in which the focal length is positive, negative, positive, positive, positive in order from the object side, and suppresses performance deterioration such as decentration, thereby reducing the number of constituent lenses. An image input device having a zoom optical system that is bright and capable of zooming at a higher magnification from a wider angle side, and a mobile phone that partially includes a camera function unit having such a zoom optical system. It aims at providing portable information terminal devices, such as PDA.

  The zoom optical system according to claim 1 of the present invention includes, in order from the object side, a first group having a positive focal length, a second group having a negative focal length, and a third group having a positive focal length. The second group is fixed in a zoom optical system having a fourth group having a positive focal length and a fifth group having a positive focal length and having a stop on the object side of the third group. It is characterized by that.

  Here, having a positive focal length is substantially synonymous with having a positive refractive power, and having a negative focal length is substantially synonymous with having a negative refractive power. .

  A zoom optical system according to a second aspect of the present invention is the zoom optical system according to the first aspect, wherein the first group includes a lens having a negative refractive power and a lens having a positive refractive power in order from the object side. Is a three-lens configuration including a cemented lens in which is bonded and a lens having a positive refractive power.

The zoom optical system according to a third aspect of the present invention is the zoom optical system according to the first or second aspect, wherein the lens on the most object side in the second group has an Abbe number νd satisfying the following formula (1): It is characterized by being.
νd <45 (1)

  The zoom optical system according to a fourth aspect of the present invention is the zoom optical system according to any one of the first to third aspects, wherein the most object-side surface of the second group is an aspherical surface. To do.

  A zoom optical system according to a fifth aspect of the present invention is the zoom optical system according to any one of the first to fourth aspects, wherein the fourth group includes a cemented lens.

  A zoom optical system according to a sixth aspect of the present invention is the zoom optical system according to any one of the first to fifth aspects, wherein the most object-side surface of the fourth group is an aspherical surface. To do.

  A zoom optical system according to a seventh aspect of the present invention is the zoom optical system according to any one of the first to sixth aspects, wherein the focusing is performed by the movement of the fifth group.

  An image input apparatus according to the present invention is an image input apparatus including a photographic optical system and an imaging device, and includes the zoom optical system according to the present invention as the photographic optical system.

  Here, the image input device is typically a camera device such as a digital (still) camera or a digital video camera provided with an imaging device such as a CCD or CMOS, but is limited to these camera devices. It includes various devices that can acquire an image of an object as an image signal by an imaging device, such as an image input unit or a scanner device of a digital copying machine.

  The imaging device only needs to be a device that can acquire an image of an object as at least a two-dimensional image signal, and the device itself does not have to have a two-dimensional array of elements. A two-dimensional image signal may be acquired by scanning the element in a direction substantially orthogonal to the arrangement direction or the like and time-division. Further, a three-dimensional image signal may be acquired such as a hologram.

  The portable information terminal device according to the present invention includes the zoom optical system according to the present invention as the photographing optical system in the portable information terminal device partially including a camera function unit having a photographing optical system and an imaging device. It is characterized by.

  Here, the portable information terminal device having a camera function part is typically a PDA (Personal Digital Assistance) or a mobile phone (smart phone, PHS (Personal Handy-Phone System)) having a camera function, for example. Other portable information terminal devices, such as so-called mobile PCs (Personal Computers), wristwatch-shaped information terminal devices, portable GPSs (Global Positioning Systems) As for the terminal device and the like, those having the above-described camera function are included in the portable information terminal device of the present invention, and a notebook PC or the like having such a camera function is also included as long as portability is not hindered.

  For example, even a camera device such as a digital camera whose main body is the camera function unit itself has a function other than the original camera function such as a communication function by using a communication card or the like. It is included in the portable information terminal device according to the invention.

  According to the zoom optical system of the first aspect of the present invention, since the second group does not move, the fixed second group is applied as a portion for supporting the zoom optical system on a fixed frame or the like of the lens barrel. be able to. The fixed frame and the like are directly coupled to a housing of an image input device such as a camera device to which the zoom optical system is attached and a housing of a portable information terminal device provided with a camera function unit. The positional relationship with the imaging device provided in the camera function unit of the information terminal device can be ensured with high accuracy and is not easily affected by performance degradation due to eccentricity or the like. Therefore, even when used in an image input device or a portable information terminal device equipped with an imaging device having a high resolution of 3 million to 5 million pixels, the high resolution performance of the imaging device can be sufficiently exhibited.

  As a result of being less susceptible to such performance deterioration, the zoom optical system itself can be brightened with a small number of constituent lenses, and can be zoomed from a wide angle side at a high magnification.

  According to the zoom optical system according to claim 2 of the present invention, the lens having the negative refractive power and the lens having the positive refractive power are joined to the first group closest to the object side in order from the object side. The three-lens configuration including the cemented lens and the lens having positive refractive power can satisfactorily correct the spherical aberration on the long focal side (telephoto side) even when the zoom ratio is high. In addition, correction of lateral chromatic aberration can be facilitated.

  In the zoom optical system according to claim 3 of the present invention, the lens closest to the object side in the second group is made of a glass material, and its Abbe number νd is less than 45, so that even with a high magnification ratio. The chromatic aberration of magnification can be corrected satisfactorily.

  In addition, the chromatic aberration of magnification increases outside the condition range of claim 3, and for example, when an imaging device of 3 million to 5 million pixel class having a high resolving power is disposed on the image side, the image for each color is a different pixel of the imaging device. It is easy to form an image, that is, it is easy to form an image across the pixels of the imaging device, and the image quality is likely to be deteriorated.

  With the zoom optical system according to claim 4 of the present invention, since the most object side surface of the second group is an aspheric surface, each aberration such as distortion, curvature of field, astigmatism on the wide angle side, It can be corrected efficiently. That is, each aberration such as distortion, curvature of field, and astigmatism is caused by the optical path of the principal ray of the light bundle incident from outside the optical axis, and the light incident surface of the lens is formed as an aspherical surface. Therefore, it is easy to arbitrarily operate this optical path, and therefore it is possible to effectively correct the aberration.

  According to the zoom optical system of the fifth aspect of the present invention, the fourth group includes the cemented lens, so that chromatic aberration and higher-order aberration can be corrected, and performance deterioration due to decentration can be further suppressed. .

  According to the zoom optical system of the sixth aspect of the present invention, since the most object side surface of the fourth group is an aspherical surface, it is possible to correct aberrations such as field curvature that may occur during zooming. it can.

  According to the zoom optical system of the seventh aspect of the present invention, by performing focusing by moving the fifth group, the fifth group can be configured with a small number of lenses, so that the weight can be reduced, and focusing can be achieved. The operation can be speeded up.

  In particular, when an imaging device such as a CCD or CMOS is provided on the image side, it is desirable that the light incident on the imaging surface is parallel light, and the fifth group closest to the imaging surface is a positive focal length. It is easy to arrange the light beam into parallel light.

  By making at least one of the lenses constituting the focusing group an aspherical surface, it is possible to improve the degree of freedom of aberration correction for obtaining good photographing performance from infinity to a short distance with a small number of lenses. It is possible and preferable.

  According to the image input device of the present invention, the zoom optical system according to the present invention described above is provided as a photographing optical system, and therefore, a fixed frame of a lens barrel that supports the zoom optical system is included in the image input device. Since it is directly coupled to the housing, the positional relationship with the imaging device is ensured with high accuracy, and is less susceptible to performance degradation due to eccentricity or the like. Accordingly, even when an imaging device having a high resolution of 3 million to 5 million pixels is mounted, the high resolution performance of the imaging device can be sufficiently exhibited.

  And as a result of being less susceptible to such performance degradation, the zoom optical system itself can be brightened with a small number of constituent lenses, and can be zoomed from a wide angle side with a high magnification, so that a high quality is achieved. An image can be obtained.

  Further, the first group closest to the object side is composed of a cemented lens in which a lens having a negative refractive power and a lens having a positive refractive power are joined in order from the object side, and a lens having a positive refractive power. The three-element zoom optical system can satisfactorily correct spherical aberration on the long focal point side (telephoto side) even when the zoom ratio is high. In addition, correction of lateral chromatic aberration can be facilitated.

  Further, the chromatic aberration of magnification can be satisfactorily corrected even with a high zoom ratio by a zoom optical system in which the most object side lens of the second group is made of a glass material and the Abbe number νd is less than 45. .

  In addition, the zoom optical system having the aspherical surface on the most object side in the second group can efficiently correct each aberration such as distortion, curvature of field, and astigmatism on the wide angle side. That is, each aberration such as distortion, curvature of field, and astigmatism is caused by the optical path of the principal ray of the light bundle incident from outside the optical axis, and the light incident surface of the lens is formed as an aspherical surface. Therefore, it is easy to arbitrarily operate this optical path, and the aberration can be corrected effectively.

  Furthermore, the zoom optical system in which the fourth group includes a cemented lens can correct chromatic aberration and higher-order aberration, and can further suppress performance deterioration due to decentration.

  In addition, aberrations such as field curvature that can occur during zooming can be corrected by the zoom optical system in which the most object-side surface of the fourth group is an aspherical surface.

  Further, the zoom optical system that performs focusing by moving the fifth group can configure the fifth group with a small number of lenses, so that the weight can be reduced and the focusing operation can be speeded up.

  In particular, in the image input apparatus of the present invention in which an image pickup device such as a CCD or CMOS is arranged on the image side, it is desirable that the light incident on the imaging surface is parallel light, and the fifth group closest to the imaging surface. Since the light beam has a positive focal length, the light beam can be easily adjusted to parallel light.

  By making at least one of the lenses constituting the focusing group an aspherical surface, it is possible to improve the degree of freedom of aberration correction for obtaining good photographing performance from infinity to a short distance with a small number of lenses. It is possible and preferable.

  As described above, according to the image input device of the present invention, it is possible to obtain a small, high-magnification and high-quality image, excellent portability, and high resolution of 3 to 5 million pixel class. An imaging device can also be supported.

  According to the portable information terminal device of the ninth aspect of the present invention, since the zoom optical system according to the present invention is provided as the photographing optical system of the camera function unit, the lens barrel supporting the zoom optical system is fixed. Since the frame and the like are directly coupled to the camera function unit or the casing of the portable information terminal device, the positional relationship with the imaging device is ensured with high accuracy and is not easily affected by performance deterioration due to eccentricity or the like. Become. Accordingly, even when an imaging device having a high resolution of 3 million to 5 million pixels is mounted, the high resolution performance of the imaging device can be sufficiently exhibited.

  And as a result of being less susceptible to such performance degradation, the zoom optical system itself can be brightened with a small number of constituent lenses, and can be zoomed from a wide angle side with a high magnification, so that a high quality is achieved. An image can be obtained.

  Further, the first group closest to the object side is composed of a cemented lens in which a lens having a negative refractive power and a lens having a positive refractive power are joined in order from the object side, and a lens having a positive refractive power. The three-element zoom optical system can satisfactorily correct spherical aberration on the long focal point side (telephoto side) even when the zoom ratio is high. In addition, correction of lateral chromatic aberration can be facilitated.

  Further, the chromatic aberration of magnification can be satisfactorily corrected even with a high zoom ratio by a zoom optical system in which the most object side lens of the second group is made of a glass material and the Abbe number νd is less than 45. .

  In addition, the zoom optical system having the aspherical surface on the most object side in the second group can efficiently correct each aberration such as distortion, curvature of field, and astigmatism on the wide angle side. That is, each aberration such as distortion, curvature of field, and astigmatism is caused by the optical path of the principal ray of the light bundle incident from outside the optical axis, and the light incident surface of the lens is formed as an aspherical surface. Therefore, it is easy to arbitrarily operate this optical path, and the aberration can be corrected effectively.

  Furthermore, the zoom optical system in which the fourth group includes a cemented lens can correct chromatic aberration and higher-order aberration, and can further suppress performance deterioration due to decentration.

  In addition, aberrations such as field curvature that can occur during zooming can be corrected by the zoom optical system in which the most object-side surface of the fourth group is an aspherical surface.

  Further, the zoom optical system that performs focusing by moving the fifth group can configure the fifth group with a small number of lenses, so that the weight can be reduced and the focusing operation can be speeded up.

  In particular, in the portable information terminal device of the present invention having a camera function unit in which an imaging device such as a CCD or CMOS is disposed on the image side, it is desirable that the light incident on the imaging surface is parallel light. By making the fifth group closest to the one having a positive focal length, it is easy to arrange the light into parallel light.

  By making at least one of the lenses constituting the focusing group an aspherical surface, it is possible to improve the degree of freedom of aberration correction for obtaining good photographing performance from infinity to a short distance with a small number of lenses. It is possible and preferable.

  As described above, according to the portable information terminal device of the present invention, it is possible to have a small, high-magnification and high-quality camera function unit, which is excellent in portability and has a class of 3 to 5 million pixels. It is also possible to deal with an imaging device that exhibits high resolution. Furthermore, if the portable information terminal device has a communication function unit such as a mobile phone, an image obtained by the camera function unit can be easily transmitted to the outside by the communication function unit.

  It should be noted that all lenses constituting the zoom optical system according to the present invention and the zoom optical system used in the image input device and the portable information terminal device according to the present invention are chemically stable and contain noxious substances such as lead and arsenic. It is preferable to form with no optical glass material. This is because the optical glass material can be recycled, and there is no concern about water pollution due to waste liquid during processing, which can contribute to global environmental conservation.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a zoom optical system, an image input device, and a portable information terminal device according to the invention will be described with reference to the drawings.

  1, 2 and 3 are diagrams showing an embodiment of a digital camera which is an aspect of the image input device of the present invention. FIGS. 1 and 2 are perspective views including a front surface, and FIG. 3 is a perspective view including a rear surface. FIG. On the front surface 21a side of the illustrated digital camera 100, a finder 22 provided on the upper left side of the left and right center of the camera body 21 as a housing, a flash 23 provided on the right side of the left and right center, The zoom lens 24 includes a plurality of lens groups, and performs zooming by changing the interval between the lens groups, and also includes a zoom lens 24 as a photographing optical system that performs focusing by displacing a predetermined lens group.

  A power switch 25 and a shutter button 26 are provided on the upper surface 21 b of the camera body 21. Further, a slide-type zoom lever 27, a liquid crystal monitor (display device) 29, and a plurality of operation buttons 30 are provided on the back surface 21 c side of the camera body 21. The zoom lever 27 is slid between the short focal end W (Wide; wide angle end) and the long focal end T (Tele; telephoto end) by sliding in the left-right direction as indicated by an arrow 28. It has become.

  A card slot 31 is provided on the side surface 21 d of the camera body 21. The card slot 31 is provided as a general-purpose slot that can use a memory card, a communication card, or the like. In FIG. 3, for example, a semiconductor memory 32 as a memory card is inserted into the card slot 31 so as to be insertable / removable.

  The operation of the liquid crystal monitor (display device) 29 is controlled by an arithmetic control circuit (control device) 33 having a central arithmetic unit as shown in FIG. The arithmetic control circuit 33 is connected to a switch 27 a operated by the zoom lever 27, a power switch 25, a plurality of operation buttons 30, and a semiconductor memory 32 inserted in the card slot 31. Furthermore, switches 26 a and 26 b operated by the shutter button 26 are also connected to the arithmetic control circuit 33.

  Here, when the shutter button 26 is half-pressed, the switch 26a is switched from OFF to ON, and the ON signal of the switch 26a is input to the arithmetic control circuit 33, and the arithmetic control circuit 33 performs control so as to start the focusing operation. . Further, when the shutter button 26 is fully pressed, the switch 26b is switched from OFF to ON, and an ON signal of the switch 26b is input to the arithmetic control circuit 33. The arithmetic control circuit 33 executes photographing after the focusing operation is completed. In addition, since this structure is a known structure, detailed description is abbreviate | omitted.

  Further, the arithmetic control circuit 33 drives and controls a driving device 34 such as a pulse motor or an ultrasonic motor that drives the lens barrel 24a of the zoom lens 24 to extend and contract according to the operation amount input to the zoom lever 27. Controls the zoom operation.

  In the camera body 21, an imaging device 35 such as a CCD that photoelectrically converts a subject image projected by the zoom lens 24 and outputs the image as an image signal is disposed. An image signal that is an electrical signal output from the imaging device 35 is input to the arithmetic control circuit 33 via the signal processing device 36 and the image processing device 37. Then, the arithmetic control circuit 33 displays the image signal output from the image processing device 37 on the liquid crystal monitor 29 as a visible image.

  Here, details of the zoom lens 24 used as a photographing optical system in the digital camera 100 which is the image input apparatus of the present embodiment will be described. The zoom lens 24 corresponds to an embodiment of the zoom optical system according to the present invention.

  For example, as shown in FIGS. 5, 9, 13, and 17, the zoom lens 24 has, in order from the object (subject) side, a first group (first lens group) I having a positive focal length and a negative focal length. A second group (second lens group) II, a third group (third lens group) III having a positive focal length, a fourth group (fourth lens group) IV having a positive focal length, And a fifth group (fifth lens group) V having a focal length of 5 mm, a diaphragm 21 on the object side of the third group III, and the second group II being fixed. A filter 22 and a cover glass 23 are disposed on the image side of the fifth group V.

  5, 9, 13, and 17, the distance (A) on the optical axis P between the first group I and the second group II, and on the optical axis P between the second group II and the stop 21. (B), an interval (C) on the optical axis P between the third group III and the fourth group IV, an interval (D) on the optical axis P between the fourth group IV and the fifth group V ), The distance (E) on the optical axis P between the fifth group V and the filter 22 is variable, and other than the second group II when zooming from the short focal end to the long focal end. Part or all of each group I, III, IV, V is displaced in the component direction along the optical axis P in the direction indicated by the arrow.

  The first lens group I of the zoom lens 24 includes, in order from the object side, a cemented lens in which a first lens 1 having a negative refractive power and a second lens 2 having a positive refractive power are cemented, and a positive lens. This is a three-lens configuration including the third lens 3 having refractive power.

Further, the fourth lens 4 on the most object side in the second group II is formed of a glass material having an Abbe number νd that satisfies the following formula (1).
νd <45 (1)

  The most object side surface (surface number 7 described later) of the second lens group II of the zoom lens 24 is formed as an aspherical surface. This aspherical surface is, for example, on the object surface (surface number 8) side of the fourth lens 4 formed into a spherical surface, and its image-side surface coincides with the object-side surface (surface number 7) of the fourth lens 4. The object side surface is formed by laminating a resin layer 4a having an aspherical surface.

  The resin layers 3a, 7a, 8a, and 11a (FIGS. 5 and 9) and 12a (FIGS. 13 and 17), which will be described later, including the resin layer 4a, are adjacent lenses 4, 3, 7, 8, and 11 respectively. , 12 may constitute a part of the aspherical lens, but in this specification, the material and Abbe of the fourth lens 4 as the lens closest to the object side in the second group II are used. When referring to the number νd, it is assumed that the resin layer 4 a does not constitute a part of the fourth lens 4.

  The fourth group IV of the zoom lens 24 includes a cemented lens.

  Further, the most object side surface (surface number 14) of the fourth lens group IV of the zoom lens 24 is formed as an aspherical surface. Also for this aspherical surface, for example, on the object surface side of the eighth lens 8 formed on the spherical surface, the image-side surface coincides with the object-side surface of the eighth lens 8, and the object-side surface is aspherical. The resin layer 8a is formed by laminating the resin layer 8a.

  The zoom lens 24 performs a focusing operation by moving the fifth group V (moving in the direction along the optical axis P direction).

  Next, the operation of the digital camera 100 of this embodiment will be described.

  First, when the power switch 25 is in an OFF state, the zoom lens 24 is in a retracted state as shown in FIG. The digital camera 100 is usually carried in this retracted state. When the user operates the power switch 25 to switch to the ON state, the lens barrel 24a is extended to the subject side as shown in FIG. At this time, each group of the zoom lens 24 inside the lens barrel 24a is arranged at the short focal end as shown in FIGS.

  Here, when the zoom lever 27 is slid in the long focal end T direction, the arrangement of each of the groups I and III to V except for the second group II is displaced as indicated by the arrows, and is moved in the long focal direction. Scaling can be performed. The viewfinder 22 also scales in conjunction with the change in the angle of view (2ω) of the zoom lens 24.

  Then, the zoom lens 24 projects an image of the subject on the imaging device 35. The subject image is converted into an electrical signal by the imaging device 35 and converted into digitized image information by the signal processing device 36 under the control of the arithmetic control circuit 33. The digitized image information is subjected to predetermined image processing by the image processing device 37 under the control of the arithmetic control circuit 13 and then displayed on the liquid crystal monitor 29 as a visible image of the subject in substantially real time. .

  In this state, when the shutter button 26 is half-pressed, the switch 26a is turned on, and the zoom lens 24 is focused on the subject. That is, when the shutter button 26 is half-pressed and the switch 26a is turned ON, the arithmetic control circuit 33 controls the driving device 34 to control the movement of the fifth group V in the direction along the optical axis P, and to capture an image. A focusing operation is performed so that the subject image is focused on the device 35 in an appropriate focus state.

  In addition, the arithmetic control circuit 33 determines white balance, exposure, shutter speed, and the like together with this focusing operation. At this time, in order to control the amount of light reaching the imaging device 35, the aperture may be changed or the ND filter may be inserted / removed. As a result, a subject image in an appropriate focus state is formed on the imaging device 35, and the subject image at this time is displayed on the liquid crystal monitor 9.

  When the shutter button 26 is further pressed (fully pressed), the switch 26b is switched on and shooting is performed. That is, the arithmetic control circuit 33 causes the semiconductor memory 32 to record the image information output from the image processing device 37 when the shutter button 26 is fully pressed.

  When the communication card 32a is inserted into the card slot 31 shown in FIG. 3 and the communication card 32a is connected to the arithmetic control circuit 33 as shown in FIG. An image signal representing an image can be transmitted to the outside by the communication function of the communication card 32a. In this case, the digital camera 100 shown in FIGS. 1 to 3 can be regarded as a portable information terminal device mainly including the communication card 32a and the camera function unit including the zoom lens 24, the imaging device 35, and the like. Such a portable information terminal device can be an embodiment of the portable information terminal device according to the present invention.

  Next, a specific numerical example 1 of the zoom lens 24 shown in FIG. 5 will be described. In Examples 1 to 4 below, f is the focal length (mm) of the entire system, F is the F number, ω is the half angle of view (degrees), R is the radius of curvature (mm), and D is the distance between the top surfaces of the shafts. (Mm), Nd represents a refractive index, and νd represents an Abbe number.

The shape of the aspherical surface is defined by the following equation (2). The curvature (reciprocal of the paraxial radius of curvature) at the aspherical vertex (on the optical axis P) is C, the conic constant is K, and the fourth-order aspherical coefficient is A ₄ , where the sixth-order aspheric coefficient is A ₆ , the eighth-order aspheric coefficient is A ₈ , and the tenth-order aspheric coefficient is A ₁₀ , the height H from the optical axis P and the optical axis P This represents the relationship with the length X of a perpendicular line drawn from a point on the aspherical surface of height H to a tangential plane (a plane perpendicular to the optical axis P) at the aspherical vertex.
X = [C · H ² / {1+ {1− (1 + K) · C ² · H ² } ^1/2 }]
+ A ₄ · H ⁴ + A ₆ · H ⁶ + A ₈ · H ⁸ + A ₁₀ · H ¹⁰ (2)

  The zoom lens 24 according to the first exemplary embodiment has eleven elements in five groups, and the specifications of each lens (the radius of curvature R, the refractive index Nd, the Abbe number νd) according to the surface numbers in order from the object side to the image side. ) And the surface distance D on the optical axis P are shown in Table 1-1.

  In this <Table 1-1>, the mark * indicates that the surface of the surface number (6, 7, 14, 17, 24) corresponding to the radius of curvature R marked with the * mark is an expression. The aspherical surface represented by (2) is shown, and the value of the radius of curvature R indicates the value of the radius of curvature on the optical axis P.

  Further, the resin layer 3a (see FIG. 5; the same applies hereinafter) adjacent to the image side surface (surface number 5) of the third lens 3 and the object side surface (surface number 8) of the fourth lens 4 are adjacent. Resin layer 4a, resin layer 7a adjacent to the object side surface (surface number 15) of the seventh lens 7, resin layer 8a adjacent to the object side surface (surface number 18) of the eighth lens 8, eleventh lens 11 The resin layer 11a adjacent to the object-side surface (surface number 25) is superposed on the surface of each surface number of each of the adjacent lenses 3, 4, 7, 8, and 11 to correspond to an aspheric surface. A lens is formed.

The values of the conic constant K and the aspheric coefficients A ₄ , A ₆ , A ₈ , and A ₁₀ in Equation (2) for each aspheric surface (surface numbers 6, 7, 14, 17, 24) are < Shown in Table 1-2>.

  Further, among the shaft upper surface distance D in <Table 1-1>, the surface distance between groups represented by variable (A), variable (B), variable (C), variable (D), and variable (E). The value of D corresponds to when the focal length of the entire system of the zoom lens 24 is at the short focal end (Wide), at the intermediate focal length (Mean), or at the long focal end (Tele). The results are shown in <Table 1-3>.

  According to the zoom lens 24 of Example 1 configured as described above, the aberrations shown in FIGS. 6 to 8 were obtained. 6 is an aberration curve diagram at the short focal end (wide angle end), FIG. 7 is an aberration curve diagram at the intermediate focal length (the aperture diameter is the same as the short focus end), and FIG. 8 is at the long focal end (telephoto end). It is an aberration curve diagram.

  As shown in the aberration curve diagrams of FIGS. 6 to 8, it is confirmed that the zoom lens according to Example 1 sufficiently corrects each aberration of spherical aberration, astigmatism, distortion, and coma. It was done.

  By configuring the zoom lens as in the first embodiment, a sufficiently wide angle of view and a high zoom ratio can be achieved in a balanced manner, and very good image performance can be ensured. did it.

  Next, specific numerical example 2 of the zoom lens 24 shown in FIG. 9 will be described. The zoom lens 24 according to the second exemplary embodiment has an eleven lens group in five groups, and the specifications of each lens (the radius of curvature R, the refractive index Nd, the Abbe number νd) according to the surface numbers in order from the object side to the image side. ) And the surface interval D on the optical axis P are shown in Table 2-1.

  In this <Table 2-1>, the mark * indicates that the surface of the surface number (6, 7, 14, 17, 24) corresponding to the radius of curvature R marked with the * mark is an expression. The aspherical surface represented by (2) is shown, and the value of the radius of curvature R indicates the value of the radius of curvature on the optical axis P.

  Further, the resin layer 3a (see FIG. 9; the same applies hereinafter) adjacent to the image side surface (surface number 5) of the third lens 3 and the object side surface (surface number 8) of the fourth lens 4 are adjacent to each other. Resin layer 4a, resin layer 7a adjacent to the object side surface (surface number 15) of the seventh lens 7, resin layer 8a adjacent to the object side surface (surface number 18) of the eighth lens 8, eleventh lens 11 The resin layer 11a adjacent to the object-side surface (surface number 25) is superposed on the surface of each surface number of each of the adjacent lenses 3, 4, 7, 8, and 11 to correspond to an aspheric surface. A lens is formed.

The values of the conic constant K and the aspheric coefficients A ₄ , A ₆ , A ₈ , and A ₁₀ in Equation (2) for each aspheric surface (surface numbers 6, 7, 14, 17, 24) are < Table 2-2> shows.

  Further, among the shaft upper surface distance D in <Table 2-1>, the surface distance between groups represented by variable (A), variable (B), variable (C), variable (D), and variable (E). The value of D corresponds to when the focal length of the entire system of the zoom lens 24 is the short focal end (Wide), the intermediate focal length (Mean), or the long focal end (Tele), respectively. The results are shown in <Table 2-3>.

  According to the zoom lens 24 of Example 2 configured as described above, the aberrations shown in FIGS. 10 to 12 were obtained. Here, FIG. 10 is an aberration curve diagram at the short focal end (wide angle end), FIG. 11 is an aberration curve diagram at the intermediate focal length (the aperture diameter is the same as the short focus end), and FIG. 12 is at the long focal end (telephoto end). It is an aberration curve diagram.

  As shown in the aberration curve diagrams of FIGS. 10 to 12, it is confirmed that the zoom lens according to Example 2 sufficiently corrects each aberration of spherical aberration, astigmatism, distortion, and coma. It was done. Therefore, it was confirmed that it corresponds to the resolution of an image sensor of 3 million to 5 million pixel class.

  By configuring the zoom lens as in the second embodiment, a sufficiently wide angle of view and a high zoom ratio can be realized in a balanced manner, and very good image performance can be ensured. did it.

  Next, a specific numerical example 3 of the zoom lens 24 shown in FIG. 13 is shown. The zoom lens 24 of Embodiment 3 has a lens configuration of 12 elements in 5 groups, and the specifications of each lens (the radius of curvature R, the refractive index Nd, the Abbe number νd) according to the surface numbers in order from the object side to the image side. ) And the surface distance D on the optical axis P are shown in Table 3-1.

  In this <Table 3-1>, the mark * indicates that the surface of the surface number (6, 7, 14, 17, 25) corresponding to the radius of curvature R marked with the * mark is an expression. The aspherical surface represented by (2) is shown, and the value of the radius of curvature R indicates the value of the radius of curvature on the optical axis P.

  Further, the resin layer 3a (see FIG. 13; the same applies hereinafter) adjacent to the image side surface (surface number 5) of the third lens 3 and the object side surface (surface number 8) of the fourth lens 4 are adjacent to each other. Resin layer 4a, resin layer 7a adjacent to the object side surface (surface number 15) of the seventh lens 7, resin layer 8a adjacent to the object side surface (surface number 18) of the eighth lens 8, and twelfth lens 12 The resin layer 12a adjacent to the object side surface (surface number 26) is superposed on the surface of each surface number corresponding to each of the adjacent lenses 3, 4, 7, 8, and 12 and is aspherical. A lens is formed.

The values of the conic constant K and the aspheric coefficients A ₄ , A ₆ , A ₈ , and A ₁₀ in Equation (2) for each aspheric surface (surface numbers 6, 7, 14, 17, 25) are < Shown in Table 3-2>.

  Further, among the shaft upper surface distance D in <Table 3-1>, the surface distance between groups represented by variable (A), variable (B), variable (C), variable (D), and variable (E). The value of D corresponds to when the focal length of the entire system of the zoom lens 24 is at the short focal end (Wide), at the intermediate focal length (Mean), or at the long focal end (Tele). The results are shown in <Table 3-3>.

  According to the zoom lens 24 of Example 3 configured as above, the aberrations shown in FIGS. 14 to 16 were obtained. 14 is an aberration curve diagram at the short focal end (wide angle end), FIG. 15 is an aberration curve diagram at the intermediate focal length (the aperture diameter is the same as the short focus end), and FIG. 16 is at the long focal end (telephoto end). It is an aberration curve diagram.

  As shown in the aberration curve diagrams of FIGS. 14 to 16, it is confirmed that the zoom lens according to the third example is sufficiently corrected for spherical aberration, astigmatism, distortion, and coma. It was done. Therefore, it was confirmed that it corresponds to the resolution of an image sensor of 3 million to 5 million pixel class.

  By configuring the zoom lens as in the third embodiment, a sufficiently wide angle of view and a high zoom ratio can be realized in a balanced manner, and very good image performance can be ensured. did it.

  Next, specific numerical value example 4 of the zoom lens 24 shown in FIG. 17 will be described. The zoom lens 24 of Example 4 has a lens configuration of 12 elements in 5 groups, and the specifications of each lens (the radius of curvature R, the refractive index Nd, the Abbe number νd) according to the surface numbers in order from the object side to the image side. ) And the surface interval D on the optical axis P are shown in <Table 4-1>.

  In this <Table 4-1>, the mark * indicates that the surface of the surface number (6, 7, 14, 17, 25) corresponding to the radius of curvature R marked with the * is an expression. The aspherical surface represented by (2) is shown, and the value of the radius of curvature R indicates the value of the radius of curvature on the optical axis P.

  Further, the resin layer 3a (see FIG. 17; the same applies hereinafter) adjacent to the image side surface (surface number 5) of the third lens 3 and the object side surface (surface number 8) of the fourth lens 4 are adjacent. Resin layer 4a, resin layer 7a adjacent to the object side surface (surface number 15) of the seventh lens 7, resin layer 8a adjacent to the object side surface (surface number 18) of the eighth lens 8, and twelfth lens 12 The resin layer 12a adjacent to the object side surface (surface number 26) is superposed on the surface of each surface number corresponding to each of the adjacent lenses 3, 4, 7, 8, and 12 and is aspherical. A lens is formed.

The values of the conic constant K and the aspheric coefficients A ₄ , A ₆ , A ₈ , and A ₁₀ in Equation (2) for each aspheric surface (surface numbers 6, 7, 14, 17, 25) are < Shown in Table 4-2>.

  Further, among the shaft upper surface distances D in <Table 4-1>, the surface distances between groups represented by variable (A), variable (B), variable (C), variable (D), and variable (E). The value of D corresponds to when the focal length of the entire system of the zoom lens 24 is at the short focal end (Wide), at the intermediate focal length (Mean), or at the long focal end (Tele). The results are shown in <Table 4-3>.

  According to the zoom lens 24 of Example 4 configured in this way, the aberrations shown in FIGS. 18 to 20 were obtained. 18 is an aberration curve diagram at the short focal end (wide angle end), FIG. 19 is an aberration curve diagram at the intermediate focal length (the aperture diameter is the same as the short focus end), and FIG. 20 is at the long focal end (telephoto end). It is an aberration curve diagram.

  As shown in the aberration curve diagrams of FIGS. 18 to 20, it is confirmed that the zoom lens according to the fourth example is sufficiently corrected for spherical aberration, astigmatism, distortion, and coma. It was done. Therefore, it was confirmed that it corresponds to the resolution of an image sensor of 3 million to 5 million pixel class.

By configuring the zoom lens as in the fourth embodiment, a sufficiently wide angle of view and a high zoom ratio can be realized in a balanced manner, and very good image performance can be ensured. did it.
(Modification 1)
As shown in FIG. 3, the digital camera 100 as the image input device or the portable information terminal device according to the embodiment described above is provided with a general-purpose slot 31 that can use a memory card, a communication card, or the like on the side surface 21 d of the camera body 21. However, the image input device and the portable information terminal device of the present invention are not necessarily limited to this mode.

  That is, for example, as shown in FIG. 21, a memory card slot 41 for the semiconductor memory 32 as a memory card and a communication card slot 42 for the communication card 32a are provided on the side surface 21d of the camera body 21 respectively. Also good.

  In the digital camera 100 having dedicated card slots 41 and 42 for each type of card, for example, as shown in FIG. 22, a semiconductor memory 32 and a communication card 32a are connected to an arithmetic control circuit 33, respectively.

  Then, the arithmetic control circuit 33 reads out the image signal (image information) of the subject image stored and accumulated in the semiconductor memory 32 by operating any one of the plurality of operation buttons 30, and the read image signal is read out. It can be transmitted to the outside by the communication card 32a.

  As described above in detail, according to the zoom lens (zoom optical system) 24 according to the embodiment (including numerical examples 1 to 4) of the present invention, the second lens group II does not move, and therefore the lens barrel 24a. As a portion for supporting the zoom lens 24 on a fixed frame or the like (not shown), the second group II that is fixed can be applied. Since the fixed frame and the like are directly coupled to the camera body 21 of the digital camera 100 to which the zoom lens 24 is attached, the positional relationship between the zoom lens 24 and the imaging device 35 of the digital camera 100 is ensured with high accuracy. It is less susceptible to performance degradation due to eccentricity. Therefore, even when used in the digital camera 100 equipped with the 3 to 5 million pixel class imaging device 35 having a high resolving power, the high resolving power performance of the imaging device 35 can be sufficiently exhibited.

  As a result of being less susceptible to such performance degradation, the zoom lens 24 itself can be brightened with a small number of constituent lenses, and can be zoomed from a wide angle side at a high magnification.

  Further, the first lens group I closest to the object side is joined in order from the object side, a cemented lens in which a first lens 1 having a negative refractive power and a second lens 2 having a positive refractive power are cemented; The three-lens configuration including the third lens 3 having refractive power can satisfactorily correct spherical aberration on the long focal side (telephoto side) even when the zoom ratio is high. In addition, correction of lateral chromatic aberration can be facilitated.

  Furthermore, the fourth lens 4 on the most object side in the second group II is made of a glass material, and its Abbe number νd is less than 45, so that the chromatic aberration of magnification can be corrected well even with a high zoom ratio. Can do.

  In addition, since the most object side surface (surface number 7) of the second group II is an aspherical surface, each aberration such as distortion, curvature of field, astigmatism on the wide angle side can be efficiently corrected. By including the cemented lens in the fourth group IV, it is possible to correct chromatic aberration and higher-order aberration, and to further suppress performance deterioration due to decentration.

  Further, since the most object-side surface (surface number 17) of the fourth lens group IV is an aspherical surface, aberrations such as field curvature that can occur during zooming can be corrected. By performing focusing by movement, the fifth group V can be configured with a small number of lenses, so that the weight can be reduced and the focusing operation can be speeded up.

  In particular, when an imaging device is disposed on the image side, it is desirable that the light incident on the imaging plane is parallel light, and the fifth group V closest to the imaging plane has a positive focal length. Therefore, it is easy to arrange the light into parallel light.

  In addition, according to the digital camera 100 according to the above-described embodiment and the first modification, it is possible to obtain a small, high-magnification and high-quality image, excellent portability, and high resolution of 3 to 5 million pixel class. It can also correspond to the imaging device 35 that exhibits the above.

  In addition, when all the lenses constituting the zoom lens 24 of the above embodiment are formed of an optical glass material that is chemically stable and does not contain lead, arsenic, or the like, the material can be recycled, and There is no concern about water pollution due to waste liquid during processing, and it can contribute to global environmental conservation.

  The digital camera 100 according to the embodiment and the modification described above is an embodiment of the image input device or the portable information terminal device according to the present invention. The digital camera 100 is used as the portable information terminal device according to the present invention. In addition to the above embodiment, the mobile phone or PDA having at least the zoom lens 24 and the imaging device 35 as a camera function part as a camera function unit is also included. Such a mobile phone is also small and has a high zoom ratio. In addition, it can have a high-quality camera function unit, is excellent in portability, and can also be applied to an imaging device that exhibits high resolution of 3 million to 5 million pixel class. Furthermore, the image obtained by the camera function unit can be easily transmitted to the outside by the communication function unit.

It is a perspective view from the front side of a digital camera concerning one embodiment provided with a zoom lens concerning one embodiment of the present invention. FIG. 2 is a perspective view showing a state in which the lens barrel of the zoom lens of the digital camera shown in FIG. 1 is extended toward the subject side. It is a perspective view from the back side of the digital camera shown in FIG. (A) is a block diagram showing a control circuit when a memory card is inserted into the card slot, and (b) is a block diagram showing a control circuit when a communication card is inserted into the card slot. FIG. 3 is a diagram illustrating a lens configuration (Example 1) of a zoom lens included in the digital camera illustrated in FIGS. FIG. 6 is a diagram of aberration curves at the short focal end of the zoom lens according to Example 1; FIG. 4 is a diagram of aberration curves at an intermediate focal length of the zoom lens according to Example 1; FIG. 6 is a diagram of aberration curves at the long focal end of the zoom lens according to Example 1; FIG. 3 is a diagram illustrating a lens configuration (Example 2) of a zoom lens included in the digital camera illustrated in FIGS. FIG. 9 is a diagram illustrating aberration curves at the short focal point of the zoom lens according to Example 2; FIG. 10 is a diagram of aberration curves at an intermediate focal length of the zoom lens according to Example 2; FIG. 9 is a diagram of aberration curves at the long focal end of the zoom lens according to Example 2; FIG. 6 is a diagram illustrating a lens configuration (Example 3) of a zoom lens included in the digital camera illustrated in FIGS. FIG. 10 is a diagram of aberration curves at the short focal point of the zoom lens according to Example 3; FIG. 9 is a diagram of aberration curves at an intermediate focal length of the zoom lens according to Example 3; FIG. 10 is a diagram of aberration curves at the long focal end of the zoom lens according to Example 3; FIG. 7 is a diagram illustrating a lens configuration (Example 4) of a zoom lens included in the digital camera illustrated in FIGS. FIG. 10 is a diagram of aberration curves at the short focal end of the zoom lens according to Example 4; FIG. 9 is a diagram of aberration curves at an intermediate focal length of the zoom lens according to Example 4; FIG. 10 is a diagram of aberration curves at the long focal end of the zoom lens according to Example 4; It is a perspective view equivalent to FIG. 3 which shows the digital camera which concerns on other embodiment. It is a block diagram which shows the control circuit of the digital camera shown in FIG.

Explanation of symbols

I Group 1
II Second group
III Group 3
IV 4th group V 5th group 1 to 11 1st to 11th lens 21 Aperture 22 Filter 23 Cover glass R Curvature radius (A) to (B) Variable axis upper surface distance P Optical axis

Claims (9)

  In order from the object side, a first group having a positive focal length, a second group having a negative focal length, a third group having a positive focal length, a fourth group having a positive focal length, A zoom optical system comprising: a fifth group having a focal length of 5 mm; and a zoom optical system having a stop on the object side of the third group, wherein the second group is fixed.   The first group has a three-lens configuration including, in order from the object side, a cemented lens in which a lens having negative refractive power and a lens having positive refractive power are cemented, and a lens having positive refractive power. The zoom optical system according to claim 1. 3. The zoom optical system according to claim 1, wherein the lens on the most object side in the second group is a glass material having an Abbe number νd satisfying the following formula.
νd <45   4. The zoom optical system according to claim 1, wherein the most object-side surface of the second group is an aspherical surface. 5.   The zoom optical system according to claim 1, wherein the fourth group includes a cemented lens.   6. The zoom optical system according to claim 1, wherein the most object side surface of the fourth group is an aspherical surface.   The zoom optical system according to claim 1, wherein focusing is performed by moving the fifth group.   An image input apparatus comprising a photographic optical system and an imaging device, comprising the zoom optical system according to claim 1 as the photographic optical system. 8. A portable information terminal device including a camera function unit having a photographing optical system and an imaging device in part, wherein the zoom optical system according to any one of claims 1 to 7 is provided as the photographing optical system. A portable information terminal device.

Images