JP4839753B2 - Imaging optical system and imaging apparatus - Google Patents

Description

  The present invention relates to an imaging optical system and an imaging apparatus, and more particularly to a folded imaging optical system in which an imaging magnification is variable.

  In recent years, with the widespread use of personal computers, digital cameras that can easily capture images into personal computers have become widespread. In addition, it has become common to incorporate a digital camera into an information processing device such as a mobile computer, a mobile phone, or a personal digital assistant (PDA). With the spread of such digital cameras, there is a demand for smaller digital cameras, and the imaging optical system needs to be further reduced in size.

Therefore, in order to reduce the size of the imaging optical system, in Patent Documents 1 and 2, a prism or a reflection mirror is provided in the middle of the optical path of the imaging optical system so that the optical path length is not changed even if the light beam is bent and scaled. There are proposals to reduce the size.
JP 2003-202500 A JP 2003-302576 A

  However, the optical systems described in Patent Document 1 and Patent Document 2 are miniaturized by bending the optical path of the zoom lens, but the angle of view at the wide-angle end of the zoom lens is about 55 to 65 degrees. Yes, it is hard to say that the angle of view is widened.

  The present invention has been made in view of such problems, and is small in size, has a large zoom ratio, has a wide angle of view exceeding 70 degrees at the wide angle end of the zoom lens, and has excellent aberration correction. An object is to provide an optical system.

  The above problem is solved by the following configuration.

An imaging optical system according to an aspect is an imaging optical system that forms an image of light from an imaging target on an imaging element, and includes a first lens group including a reflective optical element that bends a light beam at a substantially right angle in order from the imaging target side; And a subsequent lens group, and by changing the axial distance between the first lens group and the image plane, the magnification is changed from the wide-angle end to the telephoto end, and the length of the entire system at the wide-angle end is reflected by TLw. The relationship of 4 <(TLw / dr) × (y / fw) <6, where the on-axis distance of the optical element is denoted by dr, the maximum image height of the image plane is denoted by y, and the focal length of the entire system at the wide angle end is denoted by fw. fulfills, when referring to the focal length of the first lens group is f1, 2 <| f1 / fw | <4 relationships, and, a second lens group in the rear lens group, the second lens group When the focal length is represented by f2, the smaller of 0.5 <| f2 / fw | <2 Both and satisfies one relation.

In another aspect, in the above-described imaging optical system, the first lens group has a positive refractive power, and the subsequent lens group has a negative refractive power in order from the imaging target side. It has the 3rd lens group which has refractive power, and the 4th lens which has positive refractive power .

In another aspect, in these above-mentioned imaging optical system, in a case where a second lens group in the subsequent lens group, the second lens group, a lens having a lens and a negative refractive power having a positive refractive power It has the cemented lens which joined .

In another aspect, the above-described imaging optical system is characterized by satisfying a relationship of 1.1 <TLt / TLw <2 when the length of the entire system at the telephoto end is represented by TLt .

An imaging apparatus according to another aspect includes any one of the above-described imaging optical systems and an imaging element .

  The present invention has a reflective optical element that bends a light beam at a substantially right angle in the first lens group, and increases the axial distance between the first lens group and the image plane when zooming from the wide-angle end to the telephoto end. By setting the relationship between the on-axis distance of the reflective optical element and the angle of view with respect to the length of the entire system at the wide-angle end within an appropriate range, the zoom lens is small and has a large zoom ratio, and at the wide-angle end of the zoom lens With a wide angle of view exceeding 70 degrees, the aberration can be corrected satisfactorily. The imaging apparatus of the present invention including the imaging optical system having such a feature is a small and high-performance apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. An appearance of a digital camera 1 according to an embodiment of the present invention is schematically shown in FIG. 1A is a front view, FIG. 1B is a rear view, and a dotted line portion represents an imaging optical system 12 inside a digital camera 1 described later.

  The digital camera 1 has a substantially rectangular parallelepiped casing 10, and the normal direction is the direction of the shortest side of the casing 10, which is the direction perpendicular to the paper surface of FIG. The direction is defined as the horizontal direction, and the vertical direction in FIG. 1 is defined as the vertical direction. The screen imaged by the digital camera 1 is a rectangular range that is long in the horizontal direction and short in the vertical direction.

The digital camera 1 has an objective window 11, a flash light emitting unit 13, a self-timer lamp 14 on the front, a display unit 15, a mode setting switch 16, a cursor button 17, a plurality of operation keys 18, and a release button 19 on the upper surface. A power button 20 is provided.

  The objective window 11 can be opened and closed. When the objective window 11 is opened, the imaging optical system 12 appears. The flash light emitting unit 13 emits flash light that illuminates the imaging target. The self-timer lamp 14 is lit to indicate that preparation for self-timer imaging is in progress.

  The display unit 15 is composed of a liquid crystal display and displays various information such as the setting status of the digital camera 1 and operation guidance in addition to the captured image. The mode setting switch 16 is a slide type and is used for setting an operation mode of the digital camera 1.

  The cross key 17 has four contacts on the top, bottom, left, and right, and is used to move the cursor displayed on the display unit 15. The imaging optical system 12 includes a zoom lens, and the cross key 17 is also used to adjust the focal length. The operation keys 18 are used for settings related to functions of the digital camera 1 such as switching of items to be displayed on the display unit 15 and selection of displayed items. The release button 19 operates in two stages, and is used for an instruction to prepare for capturing an image to be recorded and an instruction to capture an image to be recorded.

  FIG. 2 schematically shows the configuration of the digital camera 1. In addition to the imaging optical system 12 and the display unit 15, the digital camera 1 includes an imaging element 26, a signal processing unit 22, a recording unit 23, an operation unit 24, an imaging optical system driving unit 25, and a control unit 27. The image sensor 26 is a CCD area sensor, and outputs a signal indicating the amount of received light for each pixel. The signal processing unit 22 processes the output signal of the image sensor 26 and generates image data representing the captured image. The recording unit 23 records the image data generated by the signal processing unit 22 on a detachable recording medium 23a, and reads the image data from the recording medium 23a for reproducing and displaying the image. The operation unit 24 is a general term for the above-described buttons 16 to 20, and transmits signals related to user operations to the control unit 27.

  The imaging optical system drive unit 25 has a transmission mechanism that transmits several motors and driving force thereof to the lens group of the imaging optical system 12 so that the imaging optical system 12 has a desired focal length and focal position. Move the lens group. The control unit 27 controls each unit in accordance with an instruction given via the operation unit 24.

  The configuration of the imaging optical system 12 will be described. FIGS. 3 to 7 show infinitely focused states at the wide-angle end focal length of the imaging optical systems according to the first to fifth embodiments of the present invention, and the arrows indicate the positions of the lens groups G1 to G5 during zooming. Yes. The base end of the arrow corresponds to the wide-angle end, and the tip corresponds to the telephoto end. An arrow is not shown for a lens group that is fixed during zooming. 3 to 7 are views in which the state incorporated in the digital camera 1 is developed on a plane. The prism is represented by a parallel plate and the optical axis is represented by a straight line. That is, when the imaging optical system of the first embodiment of FIG. 3 is incorporated in the digital camera 1, the imaging optical system is as shown in FIG. 8, and the parallel plate L2 in FIG. 3 corresponds to the right-angle prism PR in FIG. . The on-axis interval of the right-angle prism PR is indicated by dr.

  A first embodiment is shown in FIG. The imaging optical system of FIG. 3 includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a diaphragm S, and a third lens having a positive refractive power in order from the imaging target side. The lens group G3 includes a fourth lens group G4 having a positive refractive power.

  The first lens group G1 includes, in order from the object to be imaged, a meniscus negative lens L1 having a concave surface directed to the image surface side, a right-angle prism L2 represented by a parallel plate in the drawing, a positive lens L3 having a convex surface directed to the image surface side, It is composed of a positive lens L4 having a convex surface facing the imaging target side.

  The second lens group G2 includes, in order from the imaging target, a negative lens L5 having a meniscus shape with a convex surface directed toward the imaging target and an aspheric surface on the image plane side, a biconcave negative lens L6, and a negative lens L6. It is composed of a cemented biconvex positive lens L7.

  The third lens group G3 includes, in order from the imaging target, a positive lens L8 having a biconvex shape and a surface on the imaging target side being an aspherical surface, and a meniscus negative lens facing the convex surface toward the image plane joined with the positive lens L8. L9, a biconvex positive lens L10, a meniscus negative lens L11 having a convex surface facing the image plane joined to the lens L10, and a negative lens L12 having a biconcave shape and both surfaces being aspheric.

  The fourth lens group includes a positive lens L13 having a biconvex shape and both aspheric surfaces.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, the second lens group G2 moves to the image plane side, the third lens group G3 is fixed, and the fourth lens group G4 is The image plane moves further together with the low-pass filter F and the image plane of the image sensor 26. This movement increases the axial distance between the first lens group G1 and the image plane in zooming from the wide-angle end to the telephoto end.

  In zooming from the wide-angle end to the telephoto end, the first lens group G1 is moved to the imaging target side, the second lens group G2 is moved to the imaging target side, and the third lens group G3 is moved to the imaging target side. In addition, by fixing the image planes of the fourth lens group G4, the low-pass filter F, and the image sensor 26, it is possible to increase the axial distance between the first lens group G1 and the image plane. In this modification, the driving mechanism can be simplified by moving the first lens group G1 and the third lens group G3 at the same speed during zooming.

  A second embodiment is shown in FIG. The imaging optical system in FIG. 4 includes, in order from the imaging target side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a diaphragm S, and a third lens having a positive refractive power. The lens group G3 includes a fourth lens group G4 having a positive refractive power.

  The first lens group G1 includes, in order from the object to be imaged, a meniscus negative lens L1 having a concave surface directed to the image surface side, a right-angle prism L2 represented by a parallel plate in the drawing, a positive lens L3 having a convex surface directed to the image surface side, It is composed of a positive lens L4 having a convex surface facing the imaging target side.

  The second lens group G2 includes, in order from the imaging target, a negative lens L5 having a meniscus shape with a convex surface directed toward the imaging target and an aspheric surface on the image plane side, a biconcave negative lens L6, and a negative lens L6. It is composed of a cemented biconvex positive lens L7.

  The third lens group G3 includes, in order from the imaging target, a positive lens L8 having a biconvex shape and a surface on the imaging target side being an aspherical surface, and a meniscus negative lens facing the convex surface toward the image plane joined with the positive lens L8. L9, a biconvex positive lens L10, a meniscus negative lens L11 having a convex surface facing the image plane joined to the lens L10, and a negative lens L12 having a biconcave shape and both surfaces being aspheric.

  The fourth lens group includes a positive lens L13 having a biconvex shape and both aspheric surfaces.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, the second lens group G2 moves to the image plane side, the third lens group G3 is fixed, and the fourth lens group G4 is The image plane moves further together with the low-pass filter F and the image plane of the image sensor 26. This movement increases the axial distance between the first lens group G1 and the image plane in zooming from the wide-angle end to the telephoto end.

  In zooming from the wide-angle end to the telephoto end, the first lens group G1 is moved to the imaging target side, the second lens group G2 is moved to the imaging target side, and the third lens group G3 is moved to the imaging target side. In addition, by fixing the image planes of the fourth lens group G4, the low-pass filter F, and the image sensor 26, it is possible to increase the axial distance between the first lens group G1 and the image plane. In this modification, the driving mechanism can be simplified by moving the first lens group G1 and the third lens group G3 at the same speed during zooming.

  A third embodiment is shown in FIG. The imaging optical system of FIG. 5 includes, in order from the imaging target side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a stop S, and a third lens having a positive refractive power. The lens unit includes a group G3, a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a positive refractive power.

  The first lens group G1, in order from the object to be imaged, is a meniscus negative lens L1 with a concave surface facing the image plane side, a right-angle prism L2 represented by a parallel plate in the figure, a biconvex shape, and the surface on the image plane side is non-surface. It is comprised from the positive lens L3 which is a spherical surface.

  The second lens group G2 includes, in order from the imaging target, a negative lens L4 having a biconcave shape, a negative lens L5 having a biconcave shape, and a positive lens L6 having a convex surface facing the imaging target side that is joined to the negative lens L5. Is done.

  The third lens group G3 includes, in order from the object to be imaged, a positive lens L7 having a biconvex shape and a negative lens L8 having a biconcave shape and having an aspheric surface on the image plane side.

  The fourth lens group includes, in order from the imaging target, a meniscus negative lens L9 having a convex surface directed toward the imaging target, and a positive lens 10 having a biconvex shape joined to the negative lens L9.

  The fifth lens group G5 includes a positive lens L11 having aspheric surfaces on both sides with a convex surface facing the imaging target.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, the second lens group G2 moves to the image plane side, the third lens group G3 is fixed, and the fourth lens group G4 is The fifth lens group G5 moves further to the image plane side together with the low-pass filter F and the image plane of the image sensor 26. This movement increases the axial distance between the first lens group G1 and the image plane in zooming from the wide-angle end to the telephoto end.

  In zooming from the wide-angle end to the telephoto end, the first lens group G1 is moved to the imaging target side, the second lens group G2 is moved to the image plane side, and the third lens group G3 is moved to the imaging target side. Then, the fourth lens group G4 is moved to the imaging target side, and the fifth lens group G5, the low-pass filter F, and the image plane of the image sensor 26 are fixed, whereby the axial distance between the first lens group G1 and the image plane is fixed. Can be increased. In this modification, the driving mechanism can be simplified by moving the first lens group G1 and the third lens group G3 at the same speed during zooming.

  A fourth embodiment is shown in FIG. The imaging optical system in FIG. 6 includes, in order from the imaging target side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a diaphragm S, and a third lens having a positive refractive power. The lens group G3 includes a fourth lens group G4 having a positive refractive power.

  The first lens group G1, in order from the object to be imaged, is a meniscus negative lens L1 with a concave surface facing the image plane side, a right-angle prism L2 represented by a parallel plate in the figure, a biconvex shape, and the surface on the image plane side is non-surface. It is comprised from the positive lens L3 which is a spherical surface.

  The second lens group G2 includes, in order from the imaging target, a negative lens L4 having a biconcave shape and an aspheric surface on the image side, a negative lens L5 having a biconcave shape, and an imaging target side joined to the negative lens L5. And a positive lens L6 having a convex surface facing the surface.

  The third lens group G3 includes, in order from the object to be imaged, a positive lens L7 having a biconvex shape, a negative lens L8 having a biconcave shape and an aspheric surface on the image surface side, and a meniscus shape having a concave surface facing the image surface side. Negative lens L9 and a positive lens 10 having a biconvex shape joined to the negative lens L9.

  The fourth lens group G4 includes a positive lens L11 having both aspheric surfaces with the convex surface facing the image surface side.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, the second lens group G2 moves to the image plane side, the third lens group G3 is fixed, and the fourth lens group G4 is The image plane moves further together with the low-pass filter F and the image plane of the image sensor 26. This movement increases the axial distance between the first lens group G1 and the image plane in zooming from the wide-angle end to the telephoto end.

  In zooming from the wide-angle end to the telephoto end, the first lens group G1 is moved to the imaging target side, the second lens group G2 is moved to the imaging target side, and the third lens group G3 is moved to the imaging target side. In addition, by fixing the image planes of the fourth lens group G4, the low-pass filter F, and the image sensor 26, it is possible to increase the axial distance between the first lens group G1 and the image plane. In this modification, the driving mechanism can be simplified by moving the first lens group G1 and the third lens group G3 at the same speed during zooming.

  A fifth embodiment is shown in FIG. The imaging optical system of FIG. 7 includes, in order from the imaging target side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, an aperture S, and a third lens having a positive refractive power. The lens group G3 includes a fourth lens group G4 having a positive refractive power.

  The first lens group G1 includes, in order from the object to be imaged, a meniscus negative lens L1 having a concave surface directed to the image surface side, a right-angle prism L2 represented by a parallel plate in the drawing, a positive lens L3 having a convex surface directed to the image surface side, It is composed of a positive lens L4 having a convex surface facing the imaging target side.

  The second lens group G2 includes, in order from the imaging target, a negative lens L5 having a meniscus shape with a convex surface directed toward the imaging target and an aspheric surface on the image plane side, a biconcave negative lens L6, and a negative lens L6. It is composed of a cemented biconvex positive lens L7.

  The third lens group G3 includes, in order from the imaging target, a positive lens L8 having a biconvex shape and a surface on the imaging target side being an aspherical surface, and a meniscus negative lens facing the convex surface toward the image plane joined with the positive lens L8. L9, a biconvex positive lens L10, a meniscus negative lens L11 having a convex surface facing the image plane joined to the lens L10, and a negative lens L12 having a biconcave shape and both surfaces being aspheric.

  The fourth lens group includes a positive lens L13 having a biconvex shape and both aspheric surfaces.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, the second lens group G2 moves to the image plane side, the third lens group G3 is fixed, and the fourth lens group G4 is The image plane moves further together with the low-pass filter F and the image plane of the image sensor 26. This movement increases the axial distance between the first lens group G1 and the image plane in zooming from the wide-angle end to the telephoto end.

  In zooming from the wide-angle end to the telephoto end, the first lens group G1 is moved to the imaging target side, the second lens group G2 is moved to the imaging target side, and the third lens group G3 is moved to the imaging target side. In addition, by fixing the image planes of the fourth lens group G4, the low-pass filter F, and the image sensor 26, it is possible to increase the axial distance between the first lens group G1 and the image plane. In this modification, the driving mechanism can be simplified by moving the first lens group G1 and the third lens group G3 at the same speed during zooming.

  In each embodiment, the imaging optical system that forms an image of light from the imaging target on the imaging element, in order from the imaging target side, includes a first lens group that includes a reflective optical element that bends the light beam at a substantially right angle, and a subsequent lens group. And zooming is performed from the wide-angle end to the telephoto end by increasing the axial distance between the first lens group and the image plane.

  When zooming from the wide-angle end to the telephoto end, the axial distance between the first lens group and the image plane is increased, that is, when the first lens group approaches the image plane side at the wide-angle end, the light enters the first lens group. Since the light beam that determines the angle of view that passes through a low position from the optical axis of the first lens group, a wide angle of view can be obtained at the wide angle end. In addition, the first lens group including the reflective optical element can be reduced in size, and in particular, the depth direction of the reflective optical element can be reduced in size.

  Moreover, the relationship of the following formula 1 is satisfied.

4 <(TLw / dr) × (y / fw) <6 Equation 1
Where TLw is the length of the entire system at the wide-angle end, dr is the axial distance of the reflecting optical element, y is the maximum image height of the image plane, and fw is the focal length of the entire system at the wide-angle end.

  Expression 1 defines the relationship between the axial distance of the reflective optical element and the angle of view with respect to the length of the entire system at the wide-angle end in an appropriate range. If the value of (TLw / dr) × (y / fw) exceeds the lower limit of Equation 1, the axial distance of the first lens group becomes long and the depth of the imaging optical system becomes large, which is not preferable. On the other hand, if the value of (TLw / dr) × (y / fw) exceeds the upper limit of Equation 1, the on-axis spacing of the reflective optical element becomes small, and the light beam that determines the angle of view cannot be secured at the wide angle end. It is difficult to achieve a wide angle of view.

  It is assumed that the relationship of the following formula 2 is satisfied. Here, f1 is the focal length of the first lens group.

2 <| f1 / fw | <4 Expression 2
Formula 2 defines an appropriate range of the refractive power of the first lens unit at the wide-angle end, maintains good aberration performance, and realizes downsizing. If the value of | f1 / fw | exceeds the lower limit of Equation 2, the refractive power of the first lens group becomes too strong, negative distortion increases, and it becomes difficult to correct the aberration. On the other hand, if the value of | f1 / fw | exceeds the upper limit of Expression 2, the refractive power of the first lens group becomes too weak and the entire length of the imaging optical system becomes long.

  It is assumed that the relationship of the following formula 3 is satisfied. Here, f2 is the focal length of the second lens group of the subsequent lens group.

0.5 <| f2 / fw | <2 Equation 3
Expression 3 defines an appropriate range of the refractive power of the second lens group at the wide-angle end, maintains good aberration performance, and realizes downsizing of the imaging optical system. If the value of | f2 / fw | exceeds the lower limit of Equation 3, the refractive power of the second lens group becomes too strong, and various aberrations occur. In particular, curvature of field deteriorates and astigmatism increases. It becomes difficult to correct the aberration. On the other hand, if the value of | f1 / fw | exceeds the upper limit of Equation 3, the refractive power of the second lens group becomes too weak and the entire length of the imaging optical system becomes long.

  Moreover, it is preferable to configure the refractive power distribution of the imaging optical system as follows. The imaging optical system includes a first lens group having a positive refractive power, a subsequent lens group having a negative refractive power in order from the imaging target side, a third lens group having a positive refractive power, a positive lens And a fourth lens having a refractive power of. With such a configuration, a wide angle of view can be achieved at the wide-angle end, and a lens that is bright at the telephoto end (small F-number) and has a high zoom ratio can be achieved.

  Furthermore, it is desirable that the second lens group has a cemented lens of a positive lens and a negative lens. With this configuration, in the optical system in which the second lens group mainly performs zooming of the imaging optical system, the refractive power of the second lens group becomes strong and chromatic aberration occurs. The cemented lens disposed in the two lens group corrects chromatic aberration at the wide-angle end and the telephoto end satisfactorily.

  Moreover, it is desirable to satisfy the following relationship. However, TLt is the total length at the telephoto end.

1.1 <TLt / TLw <2 Equation 4
Formula 4 defines the ratio of the total length of the wide-angle end and the telephoto end within an appropriate range. If the ratio of the total length of the wide-angle end and the telephoto end is within a specified range, the entrance pupil position can be disposed away from the image plane and moved toward the imaging target side, and the first lens group can be arranged even at a wide angle of view. The effective diameter of the image sensor becomes smaller, and the imaging optical system can be made smaller. If the value of TLt / TLw exceeds the lower limit of Equation 4, the total length of the wide-angle end and the telephoto end become substantially the same length, the effective diameter of the first lens group becomes large, and it is not suitable for downsizing of the imaging optical system. Conversely, if the value of TLt / TLw exceeds the upper limit of Equation 4, the ratio of the total length of the wide-angle end and the telephoto end increases, and the configuration of the zooming movement mechanism becomes complicated.

  In addition, when zooming, a configuration that moves as follows is desirable. In an imaging apparatus including an imaging optical system and an imaging element that receives light guided by the imaging optical system to form an image, the first lens group has a positive refractive power, and the subsequent lens group from the imaging target side A second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens having a positive refractive power are sequentially arranged, and the first lens group is fixed when zooming is performed. The fourth lens group moves together with the image plane of the image sensor. With such a configuration, when zooming in, an image sensor is moved, the first lens group having a reflective optical element is fixed, and the total length of the imaging optical system is changed, so that an object at a short distance is imaged. Even if you change the magnification, there is no change in the field of view of the subject.

  The reflection optical element L2 (PR in FIG. 8) may be any of an internal reflection prism, a surface reflection prism, an internal reflection plane mirror, and a surface reflection mirror, but an internal reflection prism and a surface reflection prism are desirable. Since these prisms have an interval shorter than the physical interval due to the air interval due to the refractive index of the medium, the first lens group G1 can be further reduced in size.

  In each of the above embodiments, an example of a digital camera that captures a still image has been described. However, the imaging optical system of the present invention is applicable to a digital video camera that captures moving images, a mobile computer, a mobile phone, an information portable terminal, and the like. It can also be employed in cameras incorporated into information processing equipment.

  The configuration of the imaging optical system included in the imaging apparatus embodying the present invention will be described more specifically with reference to construction data and aberration diagrams. Examples 1 to 5 described as examples correspond to the first to fifth embodiments described above, respectively. Lens configuration diagrams (FIGS. 3 to 7) representing the first to fifth embodiments respectively show the lens configurations of the corresponding Examples 1 to 5. FIG.

  In the construction data of Tables 1 to 10, the radius of curvature is indicated by r, the number is assigned in order from the imaging target side, the axial interval is indicated by d, and the axial interval from the imaging target side is indicated in order from the top of the table. Yes. As for the on-axis interval that changes due to zooming, values at the wide-angle end, the intermediate focal length, and the telephoto end are shown in order from the left. The refractive index and Abbe number are indicated by N and ν, and the refractive index and Abbe number from the imaging target side are shown in order from the top of the table. Further, the refractive index and the Abbe number are for the d line, and the refractive index and the Abbe number are omitted for air. For aspheric surfaces, an asterisk (*) is added to the end of the surface number. An image sensor is disposed behind the final surface. The focal length (f) of the entire system is shown at the wide angle end, the intermediate focal length and the telephoto end, and the F number (FNO) at each focal length is shown together with other data. The unit of focal length, radius of curvature, and on-axis spacing is mm.

  The aspherical surface is defined by the following formula 5.

X (H) = C · H ² / {1+ (1−ε · C ² · H ² ) ^1/2 } + ΣAk · Hk Equation 5
Here, H is the height in the direction perpendicular to the optical axis, X (H) is the amount of displacement in the optical axis direction at the position of the height H (based on the surface vertex), C is the paraxial curvature, and ε is 2 The quadratic surface parameter, k is the order of the aspheric surface, and Ak is the k-th order aspheric coefficient.

  9A to 14B, aberrations at the wide-angle end (a), the intermediate focal length (b), and the telephoto end (c) are shown. The spherical aberration line d represents the d-line aberration, and the line SC represents the sine condition unsatisfactory amount. Astigmatism lines DM and DS are aberrations on the meridional surface and the sagittal surface, respectively. The unit is percentage only for the horizontal axis of the distortion, and mm for all other axes.

The values of the respective examples corresponding to the conditional expressions and the angle of view at the wide-angle end are shown in Table 11. All the examples satisfy the conditional expressions and achieve the problem.
<Example 1>

[Aspherical data]

<Example 2>

[Aspherical data]

<Example 3>

[Aspherical data]

<Example 4>

[Aspherical data]

<Example 5>

[Aspherical data]

[Conditional expression values]

The front view (a) and back view (b) which show typically the appearance of the digital camera of each embodiment. The figure which shows typically the structure of the digital camera of each embodiment. 1 is a diagram illustrating a configuration of an imaging optical system of a digital camera according to a first embodiment. The figure which shows the structure of the imaging optical system of the digital camera of 2nd Embodiment. The figure which shows the structure of the imaging optical system of the digital camera of 3rd Embodiment. The figure which shows the structure of the imaging optical system of the digital camera of 4th Embodiment. The figure which shows the structure of the imaging optical system of the digital camera of 5th Embodiment. The block diagram which shows the use condition in the wide angle end of the imaging optical system of 1st Embodiment. The figure which shows the aberration at the wide-angle end (a), intermediate | middle focal distance (b), and telephoto end (c) of the imaging optical system of the digital camera of 1st Embodiment. The figure which shows the aberration in the wide-angle end (a), intermediate | middle focal distance (b), and telephoto end (c) of the imaging optical system of the digital camera of 2nd Embodiment. The figure which shows the aberration in the wide-angle end (a), intermediate | middle focal distance (b), and telephoto end (c) of the imaging optical system of the digital camera of 3rd Embodiment. The figure which shows the aberration in the wide-angle end (a), intermediate | middle focal distance (b), and telephoto end (c) of the imaging optical system of the digital camera of 4th Embodiment. The figure which shows the aberration in the wide-angle end (a), intermediate | middle focal distance (b), and telephoto end (c) of the imaging optical system of the digital camera of 5th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Digital camera 12 Imaging optical system 26 Imaging device G1-G5 Lens group L1-L13 Lens PR Prism S Aperture F Low-pass filter r1-r29 surface

Claims (5)

In an imaging optical system that forms an image of light from an imaging target on an imaging device,
In order from the imaging target side, the first lens group including a reflective optical element that bends the light beam at a substantially right angle, and a subsequent lens group,
While increasing the axial distance between the first lens group and the image plane, zooming from the wide-angle end to the telephoto end,
When the length of the entire system at the wide angle end is represented by TLw, the on-axis distance of the reflecting optical element is represented by dr, the maximum image height of the image plane is represented by y, and the focal length of the entire system at the wide angle end is represented by fw.
4 <(TLw / dr) × (y / fw) <6
With satisfying the relationship,
When the focal length of the first lens group is represented by f1, the relationship of 2 <| f1 / fw | <4 and the second lens group are included in the subsequent lens group, and the focal length of the second lens group is f2. An imaging optical system characterized by satisfying at least one of the relationships of 0.5 <| f2 / fw | <2 . The first lens group has a positive refractive power, the second lens group has a negative refractive power in order from the imaging target side, a third lens group having a positive refractive power, and a positive refractive power. The imaging optical system according to claim 1, further comprising: a fourth lens including: In case of having a second lens group in the subsequent lens unit, according to claim wherein the second lens group, characterized by having a cemented lens obtained by cementing a lens having a lens and a negative refractive power having a positive refractive power The imaging optical system according to claim 1 or 2 . When the length of the entire system at the telephoto end is represented by TLt,
1.1 <TLt / TLw <2
The imaging optical system according to claim 1 , wherein the relationship is satisfied. An imaging apparatus comprising: the imaging optical system according to any one of claims 1 to 4 ; and an imaging element.

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